Research ArticleComparative Studies on Thermal Performance of Conic CutTwist Tape Inserts with SiO2 and TiO2 Nanofluids

Sami D Salman12 Abdul Amir H Kadhum1 Mohd S Takriff1 and Abu Bakar Mohamad1

1Department of Chemical and Process Engineering Faculty of Engineering and Built Environment Universiti Kebangsaan Malaysia43600 Bangi Selangor Malaysia2Biochemical Engineering Department Al-khwarizmi College of Engineering University of Baghdad Baghdad 47024 Iraq

Correspondence should be addressed to Sami D Salman samialbayatigmailcom

Received 20 August 2014 Revised 21 October 2014 Accepted 28 October 2014

Academic Editor Rupesh S Devan

Copyright copy 2015 Sami D Salman et alThis is an open access article distributed under the Creative CommonsAttribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

This paper presents a comparison study on thermal performance conic cut twist tape inserts in laminar flow of nanofluids througha constant heat fluxed tube Three tape configurations namely quadrant cut twisted tape (QCT) parabolic half cut twisted tape(PCT) and triangular cut twisted (VCT) of twist ratio 119910 = 293 and cut depth 119889

119890= 05 cm were used with 1 and 2 volume

concentration of SiO2water and TiO

2water nanofluids Typical twist tape with twist ratio of 119910 = 293 was used for comparisonThe

results show that the heat transfer was enhanced by increasing of Reynolds number and nanoparticles concentration of nanofluidThe results have also revealed that the use of twist tape enhanced the heat transfer coefficient significantly and maximum heattransfer enhancement was achieved by the presence of triangular cut twist tape insert with 2 volume concentration of SiO

2

nanofluid Over the range investigated the maximum thermal performance factor of 513 is found with the simultaneous use ofthe SiO

2nanofluid at 2 volume concentration VCT at Reynolds number of 220 Furthermore new empirical correlations for

Nusselt number friction factor and thermal performance factor are developed and reported

1 Introduction

Heat transfer enhancement technique plays substantial rolefor laminar flow regime due to the deficiency of heattransfer coefficient in plain tubes Heat transfer augmentationtechniques can be classified as active and passive techniques[1 2] Active techniques require external power sourcesuch as electric field surface vibration or Jet impingementWhereas passive techniques require fluid additives surfacemodifications or swirlvortex flow devices to enhance heattransfer The swirl flow devices include coil wire helical wirecoil and twist tape inserts Somany published articles relatedto experimental and numerical investigation on convectiveheat transfer using twisted tape inserts and water as test fluidhave been reported in the literature [3ndash13] The limitationof thermophysical properties and low thermal conductivityof water led to innovative new fluid which can enhancethe heat transfer Small amount of nanoparticles was dis-persed into base fluid to improve its thermal conductivity

The resultant fluid of suspended nanoparticles into base fluidwas called nanofluid Nanofluids were first used by Choiand Eastman [14] in 1995 at Argonne National LaboratoryUSA Subsequently several types of nanoparticles have beenemployed for nanofluid preparation including metals suchas gold (Au) copper (Cu) and silver (Ag) and also metaloxides such as TiO

2 Fe3O4 Al2O3 and CuO [15ndash21] Due

to their significantly lower cost metal oxides are preferredfor heat transfer enhancement application compared tometals The combination between twisted tape inserts withnanofluids was simultaneously utilized to produce heat trans-fer enhancement greater than either techniques operatingindividually Pathipakka and Sivashanmugam [22] proposedCFD simulation for laminar heat transfer characteristicsusing Al

2O3water nanofluids in a uniform heat fluxed

tube equipped with helical twist tape inserts Twist tapeof twist ratios 293 391 and 489 with three differentvolume concentrations of 05 1 and 15 Al

2O3water

was simultaneously used for simulation The maximum heat

Hindawi Publishing CorporationJournal of NanomaterialsVolume 2015 Article ID 921394 14 pageshttpdxdoiorg1011552015921394

2 Journal of Nanomaterials

transfer enhancement of 3129 was obtained with the useof helical insert of twist ratio 293 together with nanofluidwith volume concentration of 15 at Reynolds number of2039Wongcharee andEiamsa-ard [23] have investigated heattransfer friction and thermal performance characteristics ofCuOwater nanofluids in a circular tube fitted with alternateaxis and the typical twisted tapes experimentally Threedifferent volume concentrations of 03 05 and 07CuOwater with twisted tapes at constant twist ratio 119910119908 =

3 were used for investigation Their results revealed thatmaximum thermal performance factor of 553 was obtainedat Reynolds number of 1990 with the simultaneous useof 07 CuOwater nanofluid with alternate axis twistedtape Suresh et al [24] have performed a comparative studyon the thermal performance of helical screw tape insertswith 01 volume concentrationAl

2O3water andCuOwater

nanofluids in laminar flow through a straight circular ductunder constant heat flux boundary condition The helicalscrew tape inserts with twist ratios 119910 = 178 244 and 3were used for investigation The experimental results showthat the helical screw tape inserts offered better thermalperformance factor when used with CuOwater nanofluidthan with Al

2O3water nanofluid Salman et al [25] reported

numerical study on heat transfer enhancement of CuOwaternanofluid in a constant heat fluxed tube fitted with classicaland one side parabolic-cut twist tape inserts using FLUENTversion 6326 Twisted tapes of different twist ratios (119910 =293 391 and 489) and different cut depths (119908 = 05 1 and15 cm) were simultaneously used with 2 and 4 volumeconcentration CuO nanofluid for simulation Their resultselaborated that the parabolic cut twist tape of twist ratio 119910 =

293 and cut depth 119908 = 05 with 4 CuO nanofluid offersabout 10 enhancement for the Nusselt number than that ofclassical twisted tape at the same conditions Salman et al[26] reported an application of a mathematical model of theheat transfer enhancement and friction factor characteristicsof water in constant heat-fluxed tube fitted with one sideelliptical cut twisted tape inserts with twist ratios (119910 =

293 391 and 489) and different cut depths (119908 = 0408 and 14 cm) under laminar flow using FLUENT version6326 The results elaborated that the enhancement of heattransfer rate and the friction factor induced by elliptical cuttwisted tape inserts increases with the Reynolds number anddecreases with twist ratio In addition the results show thatthe elliptical cut twisted tape with twist ratio 119910 = 293 andcut depth 119908 = 05 cm offered higher heat transfer rate withsignificant increases in friction factor Salman et al [27] alsostudied heat transfer of water in a uniformly heated circulartube fitted with one side quadrant cut twisted tape insertsin laminar flow using FLUENT version 6326 Classical andquadrant cut twisted tape with twist ratio (119910 = 293 391and 489) and different cut depths (119908 = 05 1 and 15 cm)were employed for the simulation The results show thatthe quadrant cut twisted tape with twist ratio (119910 = 293)and cut depth (119908 = 05 cm) presents a maximum heattransfer rate with significant increases in friction factor Theattractive characteristics of triangular elliptic and quadrantcut twist tape with twist ratio 119910 = 293 mentioned abovehave motivated the present research to combine the effects

H W

Figure 1 Typical twisted tape (TT)

wde

W

H

y = HW = 293

Figure 2 Quadrant cut twisted tape (QCT)

of a novel tube insert with the laminar flow of nanofluidsFor the present study an experimental comparison studyon the thermal performance of alternative conic cut twisttape inserts with SiO

2water and TiO

2water nanofluids in

uniform heat fluxed tube was implemented The tests usingnanofluid with and without typical twisted tape were alsoconducted for comparison

2 Technical Details of Twisted Tape Inserts

The geometrical configuration of typical and conic-cut twisttape inserts is shown in Figures 1 2 3 and 4 Aluminiumstrips of 08mm thickness 245mm width and 1800mmlength are uniformly winding over a specified distance of75mm to produce the desired twist ratio (119910 = 293)The twistratio ldquo119910rdquo was defined as the ratio of the length of one full twist(360∘) to the tape width The conic cut shapes are drawn forthe specified distance on the strips before twistingThereaftercuts are made on twisted tape based on these cut shapes toobtain the desired configurations

3 Nanofluid Properties

The silica and titanium oxide nanoparticles delivered fromUSResearchNanomaterials Inc with properties illustrated inTable 1 were used for nanofluids preparation of the nanofluidThe particle size and chemical composition of nanoparticleswere checked before nanofluid samples preparation FieldEmission Scanning Electron Microscopy (FESEM) was usedfor particle size shape and agglomeration visualization TheFESEM results show that the nanoparticles are in approxi-mately spherical shape with diameter around 20 nm Energy-dispersive X-ray spectroscopy (EDX) was used for elementalanalysis or chemical characterization The EDX spectrumof nanoparticles is shown in Figures 5 and 6 Nanofluidswith desired volume concentrations of 1 and 2 wereprepared by dispersing specified amounts of SiO

2and TiO

2

nanoparticles in deionised water The samples were agitated

Journal of Nanomaterials 3

wde

W

H

y = HW = 293

Figure 3 Parabolic half cut twisted tape (PCT)

wde

W

H

y = HW = 293

Figure 4 Triangular cut twist tape (VCT)

Table 1 Properties of nanoparticles at 20∘C

Material Density(gmcm3)

Specific heat(MJm3 K)

Thermalconductivity(WmK)

Particlesize(nm)

SiO2 22 745 14 15ndash20TiO2 39 650 112 15ndash20

Table 2Thermophysical properties of water and nanofluids at 25∘C

Fluid Density 120588(gmcm3)

Viscosity120583 (Nsm2)

Specificheat

(MJm3sdotK)

Thermalconductiv-

ity(WmsdotK)

Water 09969 0000963 41672 06096Water + 1 SiO2 1 0090 0001068 41412 06275Water + 2 SiO2 10211 0001197 41141 06288Water + 1 TiO2 10260 0001073 41483 06455Water + 2 TiO2 10550 0001188 41415 06672

for 1 hr and finally transferred to Ultrasonic bath (NEY-280H) for 1 hour in order to break up any potential clustersof nanoparticles and to achieve the required homogeneoussuspensions The thermophysical properties of nanofluidsfor desired volume concentration 120601 were measured 25∘Cusing portable density meter (Type DA-130N) POLYVISCrotational viscometer and Hot Disk Transient Plane SourceTPS 2500S Properties of the water and nanofluids are shownin Table 2

4 Experimental Setup

Theexperimental set-up as shown in Figure 7 consists of a testsection calming section chilled water tankwith cooling unitcirculation pump and pipe line system Both the calming sec-tion and test sections are made of straight stainless steel tube

Energy (keV)

O

SiElement

OK 5557 6871SiK 4443 3129

Total 100 100

0 1 2 3 4 5 6 7 8 9 10

Weight () Atomic ()

Inte

nsity

(cou

nt1

s)

Figure 5 EDX spectrum of SiO2nanoparticles

ElementOK 5121 7586TiK 4879 2414

Total 100 100

Ti

Ti

TiO

Energy (keV)

Inte

nsity

(cou

nt1

s)

Weight () Atomic ()

0 1 2 3 4 5 6 7 8 9 10

Figure 6 EDX spectrum of TiO2nanoparticles

with the dimensions 2000 and 1800mm long respectivelywith 254mm ID and 3333mm OD The calming section isused to eliminate the entrance effect The outside surface ofthe test section is brazed with fifteen thermowells made ofstainless steel with dimensions of 636mm ID 1mm thickand 120mm length which are mounted on the test section ataxial positions as shown in Figure 8 The test section tube iswound with ceramic beads coated electrical SWG Nichromeheating wire of resistance 18Ω Over the electrical windingtwo layers of asbestos rope and glass wool insulations are usedtominimize heat lossThe terminals of theNichromewire areattached to theVolteq 3KVA variac variable transformerwithinput single phase 220VAC 50Hz and output voltage can beadjusted from 0 to 150V ACThe amount of heat required intest section can be achieved by varying the output voltageFifteen calibrated RTD PT 100 type temperature sensors with075 accuracy are placed in the thermowells to measure theoutsidewall temperatures TwoRTDPT 100 type temperaturesensors are inserted near the centre of pipe to measure thebulk temperature of fluid at inlet and outlet of test sectionThe pressure drop across the test section is measured usingDMP3051 digital on-line differential pressure transmitter andthe velocity of water and nanofluids is measured by portableTDS-100H ultrasonic flowmeter The hot fluid after passingthrough the heated test section flows through chilled waterfor cooling and the desired temperature is controlled bytemperature controller 30m head centrifugal pump with by-pass valves is used to regulate the flow rate through the

4 Journal of Nanomaterials

Table 3 Technical details of experimental setup and test conditions

Setup and conditions Description(A) Experimental setup

(a) Inner tube inner diameter (di) 2540mm(b) Outer tube inner diameter (do) 3335mm(c) Test tube length 1800mm(d) Material of inner tube Stainless steel 304L

(f) Insulation material Asbestos rope and glasswool

(g) Temperature measurements RTD Pt 100 type(plusmn075 accuracy)

(h) Flow measurementsTDS-100H ultrasonicflowmeter (plusmn01

accuracy)

(i) Pressure measurementDMP3051 differentialpressure transmitter(plusmn02 accuracy)

(k) Heater capacity 3 KW(B) Typical twisted tape (TT)

(a) Material Aluminium(b) Tape width (119882) 245mm(c) Tape thickness 08mm(d) Tape pitch length (119867 360∘) 75mm(e) Twist ratio (119910 =119867di) 293

(C) Conic cut twisted tape(a) Material Aluminium(b) Tape width (119882) 245mm(c) Tape thickness 08mm(d) Tape pitch length (119867 360∘) 75mm(e) Twist ratio (119910 =119867di) 293(f) Quadrant cut twist tape (QCT) 119908 = 5mm de = 5mm(g) Parabolic cut twist tape (PCT) 119908 = 589mm de = 5mm(h) Triangular cut twist tape (VCT) 119908 = 785mm de = 5mm

(D) Test conditions(a) Reynolds number (Re) 200 to 1500(b) Type of flow in inner tube Laminar

test section The details of experimental setup and operatingconditions are summarized in Table 3

5 Data Reduction

The measured data were used to calculate the Nusselt num-ber friction factor and thermal performance factor in thelaminar flow regime for Reynolds number ranging from 200to 1500

The heat transfer rate obtained from the hot fluid in thetest section tubes can be expressed as

119876conv = 119898119888119901(119879out minus 119879in) (1)

The heat transfer rate in terms of mean convective heattransfer coefficient (ℎ) can be expressed as

119876conv = ℎ119860 (119904minus 119879119887) (2)

The heat flux becomes

11990210158401015840

119904=119876conv119860

= ℎ (119904minus 119879119887) (3)

where 119879119887is a mean bulk flow temperature 119879

119887= (119879out +119879in)2

Thenmean inner wall surface temperature (119904) of the test

section is calculated from 15 stations of surface temperatureslocated between the inlet and the outlet of the test sectionusing the following equation

119904= sum

119879119904119894(119909)

15 (4)

where 119879119904119894(119909) is a local inner wall temperature which can

be calculated from steady one dimensional heat conductionequation in cylindrical coordinate [28]

1

119903

119889

119889119903(119896119903

119889119879

119889119903) = 0 (5)

The solution of this equation with constant heat flux bound-ary condition at the wall becomes

119879119904119894(119909) = 119879

119904119900(119909) minus

119876conv ln (119863119900119863119894)2120587119896119871

(6)

where 119879119904119900(119909) represent the local outer wall temperatures

measured by RTD PT 100 type temperature sensors 119863119900 119863119894

are the outer and inner tube diameters 119896 is the thermalconductivity of the test section wall and 119871 is the length ofthe test section

The average Nusselt number (Nu) can be estimated fromthe following equation

Nu =ℎavg119863119894

119896119891

(7)

The average heat transfer coefficient can be determined from(7)

ℎavg =11990210158401015840

119904

(119904minus 119879119887) (8)

The pressure drop (Δ119901) measured across the test sectionwas used to calculate friction factor (119891) using the followingequation

119891119863=2Δ119901119863

119894

1198711205881199062 (9)

The performance evaluation analysis for laminar flow at thesame pumping power is given by the following correlationproposed by Usui et al [29]

120578 =(NuNu

119900)

(119891119891119900)01666

(10)

Journal of Nanomaterials 5

Air chiller

NotebookData logger

Flow

met

er

Set of thermocouples

PumpCold water tank

Valve

Valve

Test section

Pressure transmitter

Calming section

Power supply

Volt meter amp meter and power meter

Figure 7 Schematic diagram of the experimental setup

Figure 8 Test section with thermocouple locations

where Nu and 119891 are respectively the Nusselt number andfriction factor of the tube with enhancing factor (nanofluidandor twisted tape) while Nu

119900and 119891

119900are respectively the

Nusselt number and friction factor of the plain tubeA standard uncertainty analysis was conducted for each

measurement using Kline-McClintock method [30] Themaximum uncertainties for Reynolds number Nusselt num-ber and friction factor were calculated to be 61 848 and24 respectively

6 Results and Discussions

61 Experimental Setup Validation To evaluate the reliabilityof the present experimental setup the experimental results

of pure water in plain tube without twisted tape underlaminar flow conditions were validated with shah equation[31] and Hagen-Poiseuille equation [28] The results showedreasonable agreement with the local Nusselt number (Nu

119909)

and friction factor (119891) as shown in Figures 9 and 10

Nu119909= 1953119909

minus13

lowastfor 119909lowastle 003

Nu119909= 4364 +

00722

119909lowast

for 119909lowastgt 003

(11)

119891 =64

Re (12)

The results of Nusselt number for plain tube with typicaltwisted tape (119910 = 293) were also validated with Manglik andBergle equation [3] As shown in Figure 11 the data obtainedwere found to be in good agreement with the availablecorrelation For the proof of the present typical twisted tapeNusselt number of a tube fitted with the present typicaltwisted tapes was compared with experimental data of right-left helical twist tape [32] as shown in Figures 12 and 13Apparently the typical twist tape offered an additional heattransfer enhancement with less skin friction factor

6 Journal of Nanomaterials

Axial distance x (m)

Re = 220 experimentalRe = 730 experimentalRe = 1460 experimental

Re = 220 theoreticalRe = 720 theoreticalRe = 1460 theoretical

0

5

10

15

20

25

30

0 05 1 15 2

Loca

l Nus

selt

num

ber (

Nu x

)

Figure 9 Comparison between measured and calculated localNusselt number (Nu

119909) using DI-Water

62 Effect of Nanoparticle Volume Concentration in PlainTube Experiments were performed to study heat transferenhancements in plain tube with laminar flow of deionizedwater and SiO

2and TiO

2nanofluids of 1 and 2 volume

concentration The obtained results of Nusselt number andfriction factor are elaborated in Figures 14 and 15 FromFigure 14 it can be seen that the Nusselt number increasedwith the increase of nanoparticle concentration andReynoldsnumber This means that the presence of nanoparticlesincreases the energy exchange rates in the fluid with penaltyon the wall shear stress due to Brownian motion [33] theincreases of Reynolds number increase random movementsof the fluid and consequently enhance the thermal dispersionof the flow Evidently SiO

2nanofluid with 2 volume

concentration offered highest Nusselt number followed byTiO2and water respectively On other hand Figure 15 shows

slightly augmentation in friction factor value with increasesof nanoparticles concentration This means that the pres-ence of nanoparticles volume fraction increases nanofluidviscosity with wall shear stressThe experimental results wereused to derive the following correlations of Nusselt numberand friction for water (120601 = 0) SiO

2and TiO

2nanofluids

(120601 le 2) The predicted values of these correlations showreasonable agreement with the experimental results as shownin Figures 16 and 17

For SiO2nanofluid

Nu = 06116Pr04Re02795 (1 + 120601)347 (13)

119891 = 63236Reminus0994 (1 + 120601) (14)

Dar

cy fr

ictio

n fa

ctor

(f)

0

005

01

015

02

025

03

035

0 500 1000 1500 2000

Reynolds number (Re)

Experimental dataDarcy friction factor

Figure 10 Friction factor across the test section using DI-water asthe working fluid

For TiO2nanofluid

Nu = 06116Pr04Re02795 (1 + 120601)147 (15)

119891 = 63236Reminus0994 (1 + 120601) (16)

63 Effect of Nanoparticle Volume Concentration with TwistTape Variations ofNusselt number and friction factor versusReynolds number for laminar flow of deionized water SiO

2

and TiO2nanofluids of 1 and 2 volume concentration

in tube fitted with typical twist tape (119910 = 293) areshown in Figures 18 and 19 Evidently Figure 18 shows thatthe combined use of nanofluid with twist tape producesfurther augment in heat transfer coefficient than eithernanofluid or twist tape individually The simultaneous use ofnanofluid with twist tape increases the thermal conductivityand viscosity of working fluid as well as increasing swirlflow pathThus greater fluid mixing and higher heat transfercoefficient are produced Eventually SiO

2nanofluid with 2

volume concentration with typical twist tape offered a higherNusselt number compared with the others As shown inFigure 19 the friction factor decreases with the increase ofReynolds number for water and different volume fractionsof nanoparticles Based on the experimental results thefollowing correlations of Nusselt number and friction factorwere derived The correlations are valid for laminar flow(Re lt 1500) 120601 le 2 volume concentration (120601 = 0 for water)of SiO

2and TiO

2nanofluid and typical twist tape of twist

ratio 119910 = 293 The predicted data were in good agreement

Journal of Nanomaterials 7N

usse

lt nu

mbe

r (ex

perim

enta

l)

Nusselt number (Manglik and Bergles equation)

y = 293

+15

minus15

0

20

40

60

80

100

0 20 40 60 80 100

Figure 11 Comparison of experimental and predicted Nusseltnumber of the plain tube fitted with typical twisted tape

with the experimental data within plusmn6 for Nusselt numberand plusmn8 friction factor as shown in Figures 20 and 21

Nu = 5236Pr04Re02357119910minus00881 (1 + 120601)0124 (17)

119891 = 76789Reminus0686119910minus0375 (1 + 120601)0198 (18)

64 Effect of Twist Tape Configuration The influence of andconic (quadrant parabolic half and triangular) cut twistedtape of twist ratio 119910 = 293 and cut depth 119889

119890= 05 cm

with 2 volume concentration of SiO2nanofluid on Nusselt

number and friction factor are shown in Figures 22 and 23Apparently from Figure 22 conic cut twist exhibits higherNusselt number than the typical twisted tape This can beexplained by the fact that conic cut twist tape generates swirlflow with efficient fluid mixing nearby their alternative cutswhile the typical twist tape causes swirl flow only The resultsalso reveal that the triangular cut twisted tape provides ahigherNusselt number comparedwith the othersThismeansthat the vortices behind the alternative cut edges of triangularcut twist tape give superior efficient fluid mixing resultingin further heat transfer enhancement From Figure 23 it canbe seen that friction factor decreases with the increase ofReynolds number and triangular cut twisted tape (VCT) giveshigher friction factor compared with all the other Reynoldsnumbers This implies that the influence of alternative cutsalong the edge of the triangular cut twisted tape promotesadditional wall shear stress due to flow mixing betweenthe fluids at the twist tape and tube wall In addition theexperimental data of conic cut twisted tapes with water (120601 =

0) and nanofluids (120601 = 2) were used to develop the

Nus

selt

num

ber (

Nu)

Reynolds number (Re)

RLT (y = 293) expTT (y = 293) exp

0

15

30

45

60

75

0 500 1000 1500 2000

Figure 12 Experimental Nusselt number of typical twist tape withRLT inserts

following correlations for Nusselt number and friction factorwith reasonable agreement as shown in Figures 24 and 25

For triangular cut twisted tape

Nu = 5387Pr04Re0229 (1 + 119908

119882)

00383

(1 +119889119890

119882)

minus0185

sdot (1 + 120601)0025

(19)

119891 = 6184Reminus067 (1 + 119908

119882)

0127

(1 +119889119890

119882)

minus0468

sdot (1 + 120601)0137

(20)

For parabolic half cut twisted tape

Nu = 5388Pr04Re0229 (1 + 119908

119882)

00384

(1 +119889119890

119882)

minus0184

sdot (1 + 120601)0025

(21)

119891 = 6876Reminus06771 (1 + 119908

119882)

0137

(1 +119889119890

119882)

minus0197

sdot (1 + 120601)00134

(22)

8 Journal of Nanomaterials

0

05

1

15

2

0 500 1000 1500 2000

Reynolds number (Re)

RLT (y = 293) expTT (y = 293) exp

Fric

tion

fact

or (f

)

Figure 13 Experimental friction factor of typical twist tape withRLT inserts

Nus

selt

num

ber (

Nu)

Reynolds number (Re)

DI water1 TiO2

2 TiO2

1 SiO2

2 SiO2

4

6

8

10

12

0 500 1000 1500 2000

Figure 14 Nusselt number versus Reynolds number for plain tubewith nanofluids

0

01

02

03

04

0 500 1000 1500 2000

Reynolds number (Re)

DI water1 TiO2

2 TiO2

1 SiO2

2 SiO2

Fric

tion

fact

or (f

)

Figure 15 Friction factor versus Reynolds number for plain tubewith nanofluids

0

4

8

12

16

0 4 8 12 16

Nus

selt

num

ber (

expe

rimen

tal)

Nusselt number (predicted)

DI water1 TiO2

2 TiO2

1 SiO2

2 SiO2

+6

minus6

Figure 16 Comparison of experimental and predicted Nusseltnumber for plain tube

Journal of Nanomaterials 9

0

01

02

03

04

0 01 02 03 04

Fric

tion

fact

or (e

xper

imen

tal)

Friction factor (predicted)

DI water1 TiO2

2 TiO2

1 SiO2

2 SiO2

+8

minus8

Figure 17 Comparison of experimental and predicted frictionfactor for plain tube

30

35

40

45

50

55

60

0 500 1000 1500 2000

Nus

selt

num

ber (

Nu)

Reynolds number (Re)

DI water1 TiO2

2 TiO2

1 SiO2

2 SiO2

Figure 18 Nusselt number versus Reynolds number for nanofluidswith typical twist tape (119910 = 293)

0

025

05

075

1

125

15

0 500 1000 1500 2000

Reynolds number (Re)

DI water

Fric

tion

fact

or (f

)

1 TiO2

2 TiO21 SiO2

2 SiO2

Figure 19 Nusselt number versus Reynolds number for nanofluidswith typical twist tape (119910 = 293)

0

20

40

60

80

0 20 40 60 80

Nus

selt

num

ber (

expe

rimen

tal)

Nusselt number (predicted)

DI water1 TiO2 2 TiO2

1 SiO2

2 SiO2

+6

minus6

Figure 20 Comparison of experimental and predicted Nusseltnumber with typical twist tape

10 Journal of Nanomaterials

0

025

05

075

1

125

15

0 025 05 075 1 125 15

Fric

tion

fact

or (e

xper

imen

tal)

Friction factor (predicted)

DI water1 TiO2

2 TiO2

1 SiO2

2 SiO2

+8

+8

Figure 21 Comparison of experimental and predicted frictionfactor with typical twist tape

30

35

40

45

50

55

60

65

0 500 1000 1500 2000

Nus

selt

num

ber (

Nu)

Reynolds number (Re)

QCT (2 SiO2)PCT (2 SiO2)VCT (2 SiO2)

TT (2 SiO2)TT (DI water)

Figure 22 Nusselt number versus Reynolds number for typical andconic cut twist tapes

0

03

06

09

12

15

18

0 500 1000 1500 2000

Reynolds number (Re)

QCT (2 SiO2)PCT (2 SiO2)VCT (2 SiO2)

TT (DI water)TT (DI water)

Fric

tion

fact

or (f

)

Figure 23 Friction factor versus Reynolds number for typical andconic cut twist tapes

0

20

40

60

80

0 20 40 60 80

Nus

selt

num

ber (

expe

rimen

tal)

Nusselt number (predicted)

+8

minus8

QCT (2 SiO2)PCT ( SiO2)VCT (2 SiO2)

TT (2 SiO2)TT (DI water)

Figure 24 Comparison of experimental and predicted Nusseltnumber for typical and conic cut twist tapes

Journal of Nanomaterials 11

0

05

1

15

2

0 05 1 15 2

Fric

tion

fact

or (e

xper

imen

tal)

Friction factor (predicted)

QCT (2 SiO2)PCT (2 SiO2)VCT (2 SiO2)

TT (2 SiO2)TT (DI water)

+10

minus10

Figure 25 Comparison of experimental and predicted frictionfactor for typical and conic cut twist tapes

For quadrant cut twisted tape

Nu = 538Pr04Re0226 (1 + 119908

119882)

00387

(1 +119889119890

119882)

minus0187

sdot (1 + 120601)0027

(23)

119891 = 6913Reminus071 (1 + 119908

119882)

0127

(1 +119889119890

119882)

minus016

sdot (1 + 120601)031

(24)

65 Thermal Performance of Twist Tapes The performanceanalysis of typical and conic cut twisted tape inserts in lami-nar flow of SiO

2nanofluid was accomplished by evaluating

thermal performance factor for constant pumping powercondition Thermal performance factor (120578) at constantspumping power is defined as ratio of the convective heattransfer coefficient of the tube with turbulator or enhancingmethod to that of the plain tube The following thermalperformance factor for laminar proposed by [29] is used forperformance analysis

120578 =(NuNu

119900)

(119891119891119900)01666

(25)

where Nu 119891 Nu119900 and 119891

119900are the Nusselt numbers and

friction factors for a duct configuration with and withoutinserts respectively

2

3

4

5

6

0 500 1000 1500 2000

Reynolds number (Re)

QCT (2 SiO2)PCT (2 SiO2)VCT (2 SiO2) TT (2 SiO2)

TT (DI water)

Ther

mal

per

form

ance

fact

or (120578

)

Figure 26 Variation of the thermal performance factor of typicaland conic cut twist tape

Figure 26 shows the variation of thermal performancefactor with Reynolds number for 2 volume concentrationof SiO

2nanofluid The values of thermal performance factor

at all Reynolds were found to be greater than unity for bothtypical and conic cut twisted tape inserts This indicates thattwist tape inserts are feasible in terms of energy saving in lam-inar flow regime It is evident that the thermal performancefactor triangular cut twist tape at constant Reynolds numberis higher than other twist tapes This is due to the strongerturbulenceswirl flow generated by alternative cuts along theedge twist tape The thermal performance factor was foundto be decreasing with increases in Reynolds number Thisis because of the increase in pressure loss as the Reynoldsnumber increases

The experimental results showed that the thermal perfor-mance factor is around 513ndash416 for VCT 498ndash408 for PCT488ndash405 for QCT and 483ndash401 for TT when used with2 SiO

2nanofluid While the thermal performance factor

to be around 475ndash396 for TT with water Therefore theVCT insert shows better thermal performance when usedwith SiO

2nanofluid than other twist tapesThe experimental

results are used to derive the following correlations of thermalperformance factor using least square method of regressionanalysis These correlations are valid for laminar flow (Re lt

1500) of water and 2 volume concentration SiO2for typical

and conic cut twist tapesThe comparisons between the ther-mal performance factor values obtained from experimentaldata and those predicted from the above correlations are

12 Journal of Nanomaterials

3

4

5

6

3 4 5 6

QCT (2 SiO2)PCT (2 SiO2)VCT (2 SiO2) TT (2 SiO2)

TT (DI water)

+6

minus6

Ther

mal

per

form

ance

fact

or (e

xper

imen

tal)

Thermal performance factor (predicted)

Figure 27 Comparison of experimental and predicted thermalperformance for typical and conic cut twist tapes

shown in Figure 27 As shown the predicted data are in goodagreement with the experimental data

For VCT twisted tape

120578 = 5173Reminus0118 (1 + 119908

119882)

2483

(1 +119889119890

119882)

minus0247

sdot (1 + 120601SiO2

)00183

(26)

For PCT twisted tape

120578 = 5173Re00945 (1 + 119908

119882)

3113

(1 +119889119890

119882)

minus0247

sdot (1 + 120601SiO2

)00183

(27)

For QCT twisted tape

120578 = 5173Re0118 (1 + 119908

119882)

349

(1 +119889119890

119882)

minus0247

sdot (1 + 120601SiO2

)00183

(28)

For TT twisted tape with SiO nanofluid

120578 = 791Re0093 (1 + 120601SiO2

)1283

(29)

For TT twisted tape with deionized water

120578 = 791Re0093 (30)

7 Conclusions

Heat transfer friction and thermal performance characteris-tics of SiO

2and TiO

2nanofluids with two concentrations of

1 and 2 by volume in a circular tube fitted with a typicaland conic cut twist tape in the laminar regime have beenexperimentally investigated The main conclusions from thisexperimental study are as follows

(71) SiO2and TiO

2nanofluids of different volume con-

centration in plain tube give good enhancement inNusselt number compared to deionized water Thehigher enhancement inNusselt number is obtained bySiO2nanofluids with volume concentrations of 2

(72) At similar conditions the insertion of typical twisttape causes very significant convective heat transferenhancement in the laminar flow however furtherenhancement is observed by the simultaneous use ofnanofluid with twisted tape compared to the use oftwisted tape or nanofluid alone

(73) The use of nanofluid with the conic cut twist tapeprovides a considerably higher Nusselt number thanthat of nanofluid with the typical twist tape for allReynolds numbers examinedThe triangular cut twisttape offers higher heat transfer rate than the typicaltwist tape and other conic cut configurations

(74) Over the range investigated (Re = 220ndash1500) themaximum thermal performance factor of 513 isfound with the simultaneous use of the triangulartwist tape with SiO

2nanofluid with 2 volume

concentration at Reynolds number of 220(75) The empirical correlations for the Nusselt number

friction factor and the thermal performance factorfor typical and conic cut twist tapes are developedand fitted with the experimental data of water andnanofluids

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

The authors would like to thank the National Universityof Malaysia and the Ministry of Higher Education for thefinancial support (FRGS12013TK07UKM011 and DPP-2013-114) to perform this investigation

References

[1] A Bejan and A D KrausHeat Transfer Handbook John Wileyamp Sons 2003

[2] I Singh and N Diwakar International Journal of AppliedResearch in Mechanical Engineering vol 3 pp 16ndash29 2013

[3] R M Manglik and A E Bergles ldquoHeat transfer and pressuredrop correlations for twisted-tape inserts in isothermal tubes

Journal of Nanomaterials 13

part Imdashlaminar flowsrdquo Journal of Heat Transfer vol 115 no 4pp 881ndash889 1993

[4] S K Saha and D Chakraborty ldquoHeat transfer and pressuredrop characteristics of laminar flow through a circular tubefitted with regularly spaced twisted tape elements with multipletwistsrdquo in Proceedings of the Heat andMass Transfer Conferencepp 313ndash318 Kanpur India 1997

[5] S Al-Fahed L M Chamra and W Chakroun ldquoPressure dropand heat transfer comparison for both microfin tube andtwisted-tape inserts in laminar flowrdquo ExperimentalThermal andFluid Science vol 18 no 4 pp 323ndash333 1998

[6] M S Lokanath and R D Misal ldquoAn experimental study on theperformance of plate heat exchanger and an augmented shelland tube heat exchanger for different types of fluids for marineapplicationsrdquo in Proceedings of the 5th ISHMT-ASME Heat andMass Transfer Conference pp 863ndash868 TataMcGraw-Hill NewDelhi India 2002

[7] P Sivashanmugam and S Suresh ldquoExperimental studies onheat transfer and friction factor characteristics of laminar flowthrough a circular tube fitted with helical screw-tape insertsrdquoApplied Thermal Engineering vol 26 no 16 pp 1990ndash19972006

[8] P Sivashanmugam and S Suresh ldquoExperimental studies onheat transfer and friction factor characteristics of laminar flowthrough a circular tube fitted with regularly spaced helicalscrew-tape insertsrdquo Experimental Thermal and Fluid Sciencevol 31 no 4 pp 301ndash308 2007

[9] S Jaisankar T K Radhakrishnan and K N Sheeba ldquoStudieson heat transfer and friction factor characteristics of ther-mosyphon solar water heating system with helical twistedtapesrdquo Energy vol 34 no 9 pp 1054ndash1064 2009

[10] A V N Kapatkar B D A S Padalkar and C S KasbeldquoExperimental investigation on heat transfer enhancement inlaminar flow in circular tube equipped with different insertsrdquoAMAE International Journal on Manufacturing and MaterialScience vol 1 pp 1ndash6 2011

[11] J Guo A Fan X Zhang and W Liu ldquoA numerical studyon heat transfer and friction factor characteristics of laminarflow in a circular tube fitted with center-cleared twisted taperdquoInternational Journal ofThermal Sciences vol 50 no 7 pp 1263ndash1270 2011

[12] K Wongcharee and S Eiamsa-ard ldquoFriction and heat trans-fer characteristics of laminar swirl flow through the roundtubes inserted with alternate clockwise and counter-clockwisetwisted-tapesrdquo International Communications in Heat andMassTransfer vol 38 no 3 pp 348ndash352 2011

[13] E Z Ibrahim ldquoAugmentation of laminar flow and heat transferin flat tubes by means of helical screw-tape insertsrdquo EnergyConversion and Management vol 52 no 1 pp 250ndash257 2011

[14] S U S Choi and J A Eastman ldquoEnhancing thermal con-ductivity of fluids with nanoparticlesrdquo in Developments andApplications of Non-Newtonian Flows D A Siguier and HP Wang Eds pp 99ndash105 American Society of MechanicalEngineers New York NY USA 1995

[15] C Y Tsai H T Chien P P Ding B Chan T Y Luh and PH Chen ldquoEffect of structural character of gold nanoparticles innanofluid on heat pipe thermal performancerdquoMaterials Lettersvol 58 no 9 pp 1461ndash1465 2004

[16] M-S Liu M C-C Lin C Y Tsai and C-C Wang ldquoEnhance-ment of thermal conductivity with Cu for nanofluids using

chemical reduction methodrdquo International Journal of Heat andMass Transfer vol 49 no 17-18 pp 3028ndash3033 2006

[17] E Tamjid andBHGuenther ldquoRheology and colloidal structureof silver nanoparticles dispersed in diethylene glycolrdquo PowderTechnology vol 197 no 1-2 pp 49ndash53 2010

[18] SM SMurshed K C Leong and C Yang ldquoEnhanced thermalconductivity of TiO

2water based nanofluidsrdquo International

Journal of Thermal Sciences vol 44 no 4 pp 367ndash373 2005[19] H Zhu C Zhang S Liu Y Tang and Y Yin ldquoEffects of

nanoparticle clustering and alignment on thermal conductiv-ities of Fe

3O4aqueous nanofluidsrdquo Applied Physics Letters vol

89 Article ID 023123 2006[20] J A Eastman U S Choi S Li L J Thompson and S Lee

ldquoEnhanced thermal conductivity through the development ofnanofluidsrdquoMRS Proceedings vol 457 1996

[21] M EMeibodi M Vafaie-Sefti AM Rashidi A Amrollahi MTabasi and H S Kalal ldquoSimple model for thermal conductivityof nanofluids using resistance model approachrdquo InternationalCommunications in Heat and Mass Transfer vol 37 no 5 pp555ndash559 2010

[22] G Pathipakka and P Sivashanmugam ldquoHeat transfer behaviourof nanofluids in a uniformly heated circular tube fittedwith heli-cal inserts in laminar flowrdquo Superlattices and Microstructuresvol 47 no 2 pp 349ndash360 2010

[23] K Wongcharee and S Eiamsa-ard ldquoEnhancement of heattransfer using CuOwater nanofluid and twisted tape withalternate axisrdquo International Communications in Heat and MassTransfer vol 38 no 6 pp 742ndash748 2011

[24] S Suresh K P Venkitaraj and P Selvakumar ldquoComparativestudy on thermal performance of helical screw tape inserts inlaminar flow using Al

2O3water and CuOwater nanofluidsrdquo

Superlattices and Microstructures vol 49 no 6 pp 608ndash6222011

[25] S D Salman A A H Kadhum M S Takriff and A BMohamad ldquoHeat transfer enhancement of laminar nanofluidsflow in a circular tube fitted with parabolic-cut twisted tapeinsertsrdquo The Scientific World Journal vol 2014 Article ID543231 7 pages 2014

[26] S D Salman A A H Kadhum M S Takriff and A BMohamad ldquoCFD simulation of heat transfer and friction factoraugmentation in a circular tube fitted with elliptic-cut twistedtape insertsrdquo Mathematical Problems in Engineering vol 2013Article ID 163839 7 pages 2013

[27] S D Salman A A H Kadhum M S Takriff and A BMohamad ldquoCFD analysis of Heat transfer and friction factorcharacteristics in a circular tube fitted with Quadrant-cuttwisted tape insertsrdquoMathematical Problems in Engineering vol2013 Article ID 273764 8 pages 2013

[28] F P Incropera D P Dewitt T L Bergman and A S LavineFundamentals of Heat and Mass Transfer John Wiley amp Sons2007

[29] H Usui Y Sano K Iwashita and A Isozaki ldquoEnhancement ofheat transfer by a combination of internally grooved rough tubeand twisted taperdquo International Chemical Engineering vol 26no 1 pp 97ndash104 1986

[30] J P Holman Experimental Methods for Engineers McGraw-Hill New York NY USA 2011

[31] R K Shah and A L London Laminar Flow Forced Convectionin Ducts Academic Press New York NY USA 1978

14 Journal of Nanomaterials

[32] P KNagarajan andP Sivashanmugam ldquoCFD simulation of heattransfer augmentation in a circular tube fitted with right-lefthelical inserts with spacerrdquo International Journal of ChemicalEngineering Research vol 1 pp 1ndash11 2009

[33] P Keblinski S R Phillpot S U S Choi and J A EastmanldquoMechanisms of heat flow in suspensions of nano-sized particles(nanofluids)rdquo International Journal of Heat and Mass Transfervol 45 no 4 pp 855ndash863 2002

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

2 Journal of Nanomaterials

transfer enhancement of 3129 was obtained with the useof helical insert of twist ratio 293 together with nanofluidwith volume concentration of 15 at Reynolds number of2039Wongcharee andEiamsa-ard [23] have investigated heattransfer friction and thermal performance characteristics ofCuOwater nanofluids in a circular tube fitted with alternateaxis and the typical twisted tapes experimentally Threedifferent volume concentrations of 03 05 and 07CuOwater with twisted tapes at constant twist ratio 119910119908 =

3 were used for investigation Their results revealed thatmaximum thermal performance factor of 553 was obtainedat Reynolds number of 1990 with the simultaneous useof 07 CuOwater nanofluid with alternate axis twistedtape Suresh et al [24] have performed a comparative studyon the thermal performance of helical screw tape insertswith 01 volume concentrationAl

2O3water andCuOwater

nanofluids in laminar flow through a straight circular ductunder constant heat flux boundary condition The helicalscrew tape inserts with twist ratios 119910 = 178 244 and 3were used for investigation The experimental results showthat the helical screw tape inserts offered better thermalperformance factor when used with CuOwater nanofluidthan with Al

2O3water nanofluid Salman et al [25] reported

numerical study on heat transfer enhancement of CuOwaternanofluid in a constant heat fluxed tube fitted with classicaland one side parabolic-cut twist tape inserts using FLUENTversion 6326 Twisted tapes of different twist ratios (119910 =293 391 and 489) and different cut depths (119908 = 05 1 and15 cm) were simultaneously used with 2 and 4 volumeconcentration CuO nanofluid for simulation Their resultselaborated that the parabolic cut twist tape of twist ratio 119910 =

293 and cut depth 119908 = 05 with 4 CuO nanofluid offersabout 10 enhancement for the Nusselt number than that ofclassical twisted tape at the same conditions Salman et al[26] reported an application of a mathematical model of theheat transfer enhancement and friction factor characteristicsof water in constant heat-fluxed tube fitted with one sideelliptical cut twisted tape inserts with twist ratios (119910 =

293 391 and 489) and different cut depths (119908 = 0408 and 14 cm) under laminar flow using FLUENT version6326 The results elaborated that the enhancement of heattransfer rate and the friction factor induced by elliptical cuttwisted tape inserts increases with the Reynolds number anddecreases with twist ratio In addition the results show thatthe elliptical cut twisted tape with twist ratio 119910 = 293 andcut depth 119908 = 05 cm offered higher heat transfer rate withsignificant increases in friction factor Salman et al [27] alsostudied heat transfer of water in a uniformly heated circulartube fitted with one side quadrant cut twisted tape insertsin laminar flow using FLUENT version 6326 Classical andquadrant cut twisted tape with twist ratio (119910 = 293 391and 489) and different cut depths (119908 = 05 1 and 15 cm)were employed for the simulation The results show thatthe quadrant cut twisted tape with twist ratio (119910 = 293)and cut depth (119908 = 05 cm) presents a maximum heattransfer rate with significant increases in friction factor Theattractive characteristics of triangular elliptic and quadrantcut twist tape with twist ratio 119910 = 293 mentioned abovehave motivated the present research to combine the effects

H W

Figure 1 Typical twisted tape (TT)

wde

W

H

y = HW = 293

Figure 2 Quadrant cut twisted tape (QCT)

of a novel tube insert with the laminar flow of nanofluidsFor the present study an experimental comparison studyon the thermal performance of alternative conic cut twisttape inserts with SiO

2water and TiO

2water nanofluids in

uniform heat fluxed tube was implemented The tests usingnanofluid with and without typical twisted tape were alsoconducted for comparison

2 Technical Details of Twisted Tape Inserts

The geometrical configuration of typical and conic-cut twisttape inserts is shown in Figures 1 2 3 and 4 Aluminiumstrips of 08mm thickness 245mm width and 1800mmlength are uniformly winding over a specified distance of75mm to produce the desired twist ratio (119910 = 293)The twistratio ldquo119910rdquo was defined as the ratio of the length of one full twist(360∘) to the tape width The conic cut shapes are drawn forthe specified distance on the strips before twistingThereaftercuts are made on twisted tape based on these cut shapes toobtain the desired configurations

3 Nanofluid Properties

The silica and titanium oxide nanoparticles delivered fromUSResearchNanomaterials Inc with properties illustrated inTable 1 were used for nanofluids preparation of the nanofluidThe particle size and chemical composition of nanoparticleswere checked before nanofluid samples preparation FieldEmission Scanning Electron Microscopy (FESEM) was usedfor particle size shape and agglomeration visualization TheFESEM results show that the nanoparticles are in approxi-mately spherical shape with diameter around 20 nm Energy-dispersive X-ray spectroscopy (EDX) was used for elementalanalysis or chemical characterization The EDX spectrumof nanoparticles is shown in Figures 5 and 6 Nanofluidswith desired volume concentrations of 1 and 2 wereprepared by dispersing specified amounts of SiO

2and TiO

2

nanoparticles in deionised water The samples were agitated

Journal of Nanomaterials 3

wde

W

H

y = HW = 293

Figure 3 Parabolic half cut twisted tape (PCT)

wde

W

H

y = HW = 293

Figure 4 Triangular cut twist tape (VCT)

Table 1 Properties of nanoparticles at 20∘C

Material Density(gmcm3)

Specific heat(MJm3 K)

Thermalconductivity(WmK)

Particlesize(nm)

SiO2 22 745 14 15ndash20TiO2 39 650 112 15ndash20

Table 2Thermophysical properties of water and nanofluids at 25∘C

Fluid Density 120588(gmcm3)

Viscosity120583 (Nsm2)

Specificheat

(MJm3sdotK)

Thermalconductiv-

ity(WmsdotK)

Water 09969 0000963 41672 06096Water + 1 SiO2 1 0090 0001068 41412 06275Water + 2 SiO2 10211 0001197 41141 06288Water + 1 TiO2 10260 0001073 41483 06455Water + 2 TiO2 10550 0001188 41415 06672

for 1 hr and finally transferred to Ultrasonic bath (NEY-280H) for 1 hour in order to break up any potential clustersof nanoparticles and to achieve the required homogeneoussuspensions The thermophysical properties of nanofluidsfor desired volume concentration 120601 were measured 25∘Cusing portable density meter (Type DA-130N) POLYVISCrotational viscometer and Hot Disk Transient Plane SourceTPS 2500S Properties of the water and nanofluids are shownin Table 2

4 Experimental Setup

Theexperimental set-up as shown in Figure 7 consists of a testsection calming section chilled water tankwith cooling unitcirculation pump and pipe line system Both the calming sec-tion and test sections are made of straight stainless steel tube

Energy (keV)

O

SiElement

OK 5557 6871SiK 4443 3129

Total 100 100

0 1 2 3 4 5 6 7 8 9 10

Weight () Atomic ()

Inte

nsity

(cou

nt1

s)

Figure 5 EDX spectrum of SiO2nanoparticles

ElementOK 5121 7586TiK 4879 2414

Total 100 100

Ti

Ti

TiO

Energy (keV)

Inte

nsity

(cou

nt1

s)

Weight () Atomic ()

0 1 2 3 4 5 6 7 8 9 10

Figure 6 EDX spectrum of TiO2nanoparticles

with the dimensions 2000 and 1800mm long respectivelywith 254mm ID and 3333mm OD The calming section isused to eliminate the entrance effect The outside surface ofthe test section is brazed with fifteen thermowells made ofstainless steel with dimensions of 636mm ID 1mm thickand 120mm length which are mounted on the test section ataxial positions as shown in Figure 8 The test section tube iswound with ceramic beads coated electrical SWG Nichromeheating wire of resistance 18Ω Over the electrical windingtwo layers of asbestos rope and glass wool insulations are usedtominimize heat lossThe terminals of theNichromewire areattached to theVolteq 3KVA variac variable transformerwithinput single phase 220VAC 50Hz and output voltage can beadjusted from 0 to 150V ACThe amount of heat required intest section can be achieved by varying the output voltageFifteen calibrated RTD PT 100 type temperature sensors with075 accuracy are placed in the thermowells to measure theoutsidewall temperatures TwoRTDPT 100 type temperaturesensors are inserted near the centre of pipe to measure thebulk temperature of fluid at inlet and outlet of test sectionThe pressure drop across the test section is measured usingDMP3051 digital on-line differential pressure transmitter andthe velocity of water and nanofluids is measured by portableTDS-100H ultrasonic flowmeter The hot fluid after passingthrough the heated test section flows through chilled waterfor cooling and the desired temperature is controlled bytemperature controller 30m head centrifugal pump with by-pass valves is used to regulate the flow rate through the

4 Journal of Nanomaterials

Table 3 Technical details of experimental setup and test conditions

Setup and conditions Description(A) Experimental setup

(a) Inner tube inner diameter (di) 2540mm(b) Outer tube inner diameter (do) 3335mm(c) Test tube length 1800mm(d) Material of inner tube Stainless steel 304L

(f) Insulation material Asbestos rope and glasswool

(g) Temperature measurements RTD Pt 100 type(plusmn075 accuracy)

(h) Flow measurementsTDS-100H ultrasonicflowmeter (plusmn01

accuracy)

(i) Pressure measurementDMP3051 differentialpressure transmitter(plusmn02 accuracy)

(k) Heater capacity 3 KW(B) Typical twisted tape (TT)

(a) Material Aluminium(b) Tape width (119882) 245mm(c) Tape thickness 08mm(d) Tape pitch length (119867 360∘) 75mm(e) Twist ratio (119910 =119867di) 293

(C) Conic cut twisted tape(a) Material Aluminium(b) Tape width (119882) 245mm(c) Tape thickness 08mm(d) Tape pitch length (119867 360∘) 75mm(e) Twist ratio (119910 =119867di) 293(f) Quadrant cut twist tape (QCT) 119908 = 5mm de = 5mm(g) Parabolic cut twist tape (PCT) 119908 = 589mm de = 5mm(h) Triangular cut twist tape (VCT) 119908 = 785mm de = 5mm

(D) Test conditions(a) Reynolds number (Re) 200 to 1500(b) Type of flow in inner tube Laminar

test section The details of experimental setup and operatingconditions are summarized in Table 3

5 Data Reduction

The measured data were used to calculate the Nusselt num-ber friction factor and thermal performance factor in thelaminar flow regime for Reynolds number ranging from 200to 1500

The heat transfer rate obtained from the hot fluid in thetest section tubes can be expressed as

119876conv = 119898119888119901(119879out minus 119879in) (1)

The heat transfer rate in terms of mean convective heattransfer coefficient (ℎ) can be expressed as

119876conv = ℎ119860 (119904minus 119879119887) (2)

The heat flux becomes

11990210158401015840

119904=119876conv119860

= ℎ (119904minus 119879119887) (3)

where 119879119887is a mean bulk flow temperature 119879

119887= (119879out +119879in)2

Thenmean inner wall surface temperature (119904) of the test

section is calculated from 15 stations of surface temperatureslocated between the inlet and the outlet of the test sectionusing the following equation

119904= sum

119879119904119894(119909)

15 (4)

where 119879119904119894(119909) is a local inner wall temperature which can

be calculated from steady one dimensional heat conductionequation in cylindrical coordinate [28]

1

119903

119889

119889119903(119896119903

119889119879

119889119903) = 0 (5)

The solution of this equation with constant heat flux bound-ary condition at the wall becomes

119879119904119894(119909) = 119879

119904119900(119909) minus

119876conv ln (119863119900119863119894)2120587119896119871

(6)

where 119879119904119900(119909) represent the local outer wall temperatures

measured by RTD PT 100 type temperature sensors 119863119900 119863119894

are the outer and inner tube diameters 119896 is the thermalconductivity of the test section wall and 119871 is the length ofthe test section

The average Nusselt number (Nu) can be estimated fromthe following equation

Nu =ℎavg119863119894

119896119891

(7)

The average heat transfer coefficient can be determined from(7)

ℎavg =11990210158401015840

119904

(119904minus 119879119887) (8)

The pressure drop (Δ119901) measured across the test sectionwas used to calculate friction factor (119891) using the followingequation

119891119863=2Δ119901119863

119894

1198711205881199062 (9)

The performance evaluation analysis for laminar flow at thesame pumping power is given by the following correlationproposed by Usui et al [29]

120578 =(NuNu

119900)

(119891119891119900)01666

(10)

Journal of Nanomaterials 5

Air chiller

NotebookData logger

Flow

met

er

Set of thermocouples

PumpCold water tank

Valve

Valve

Test section

Pressure transmitter

Calming section

Power supply

Volt meter amp meter and power meter

Figure 7 Schematic diagram of the experimental setup

Figure 8 Test section with thermocouple locations

where Nu and 119891 are respectively the Nusselt number andfriction factor of the tube with enhancing factor (nanofluidandor twisted tape) while Nu

119900and 119891

119900are respectively the

Nusselt number and friction factor of the plain tubeA standard uncertainty analysis was conducted for each

measurement using Kline-McClintock method [30] Themaximum uncertainties for Reynolds number Nusselt num-ber and friction factor were calculated to be 61 848 and24 respectively

6 Results and Discussions

61 Experimental Setup Validation To evaluate the reliabilityof the present experimental setup the experimental results

of pure water in plain tube without twisted tape underlaminar flow conditions were validated with shah equation[31] and Hagen-Poiseuille equation [28] The results showedreasonable agreement with the local Nusselt number (Nu

119909)

and friction factor (119891) as shown in Figures 9 and 10

Nu119909= 1953119909

minus13

lowastfor 119909lowastle 003

Nu119909= 4364 +

00722

119909lowast

for 119909lowastgt 003

(11)

119891 =64

Re (12)

The results of Nusselt number for plain tube with typicaltwisted tape (119910 = 293) were also validated with Manglik andBergle equation [3] As shown in Figure 11 the data obtainedwere found to be in good agreement with the availablecorrelation For the proof of the present typical twisted tapeNusselt number of a tube fitted with the present typicaltwisted tapes was compared with experimental data of right-left helical twist tape [32] as shown in Figures 12 and 13Apparently the typical twist tape offered an additional heattransfer enhancement with less skin friction factor

6 Journal of Nanomaterials

Axial distance x (m)

Re = 220 experimentalRe = 730 experimentalRe = 1460 experimental

Re = 220 theoreticalRe = 720 theoreticalRe = 1460 theoretical

0

5

10

15

20

25

30

0 05 1 15 2

Loca

l Nus

selt

num

ber (

Nu x

)

Figure 9 Comparison between measured and calculated localNusselt number (Nu

119909) using DI-Water

62 Effect of Nanoparticle Volume Concentration in PlainTube Experiments were performed to study heat transferenhancements in plain tube with laminar flow of deionizedwater and SiO

2and TiO

2nanofluids of 1 and 2 volume

concentration The obtained results of Nusselt number andfriction factor are elaborated in Figures 14 and 15 FromFigure 14 it can be seen that the Nusselt number increasedwith the increase of nanoparticle concentration andReynoldsnumber This means that the presence of nanoparticlesincreases the energy exchange rates in the fluid with penaltyon the wall shear stress due to Brownian motion [33] theincreases of Reynolds number increase random movementsof the fluid and consequently enhance the thermal dispersionof the flow Evidently SiO

2nanofluid with 2 volume

concentration offered highest Nusselt number followed byTiO2and water respectively On other hand Figure 15 shows

slightly augmentation in friction factor value with increasesof nanoparticles concentration This means that the pres-ence of nanoparticles volume fraction increases nanofluidviscosity with wall shear stressThe experimental results wereused to derive the following correlations of Nusselt numberand friction for water (120601 = 0) SiO

2and TiO

2nanofluids

(120601 le 2) The predicted values of these correlations showreasonable agreement with the experimental results as shownin Figures 16 and 17

For SiO2nanofluid

Nu = 06116Pr04Re02795 (1 + 120601)347 (13)

119891 = 63236Reminus0994 (1 + 120601) (14)

Dar

cy fr

ictio

n fa

ctor

(f)

0

005

01

015

02

025

03

035

0 500 1000 1500 2000

Reynolds number (Re)

Experimental dataDarcy friction factor

Figure 10 Friction factor across the test section using DI-water asthe working fluid

For TiO2nanofluid

Nu = 06116Pr04Re02795 (1 + 120601)147 (15)

119891 = 63236Reminus0994 (1 + 120601) (16)

63 Effect of Nanoparticle Volume Concentration with TwistTape Variations ofNusselt number and friction factor versusReynolds number for laminar flow of deionized water SiO

2

and TiO2nanofluids of 1 and 2 volume concentration

in tube fitted with typical twist tape (119910 = 293) areshown in Figures 18 and 19 Evidently Figure 18 shows thatthe combined use of nanofluid with twist tape producesfurther augment in heat transfer coefficient than eithernanofluid or twist tape individually The simultaneous use ofnanofluid with twist tape increases the thermal conductivityand viscosity of working fluid as well as increasing swirlflow pathThus greater fluid mixing and higher heat transfercoefficient are produced Eventually SiO

2nanofluid with 2

volume concentration with typical twist tape offered a higherNusselt number compared with the others As shown inFigure 19 the friction factor decreases with the increase ofReynolds number for water and different volume fractionsof nanoparticles Based on the experimental results thefollowing correlations of Nusselt number and friction factorwere derived The correlations are valid for laminar flow(Re lt 1500) 120601 le 2 volume concentration (120601 = 0 for water)of SiO

2and TiO

2nanofluid and typical twist tape of twist

ratio 119910 = 293 The predicted data were in good agreement

Journal of Nanomaterials 7N

usse

lt nu

mbe

r (ex

perim

enta

l)

Nusselt number (Manglik and Bergles equation)

y = 293

+15

minus15

0

20

40

60

80

100

0 20 40 60 80 100

Figure 11 Comparison of experimental and predicted Nusseltnumber of the plain tube fitted with typical twisted tape

with the experimental data within plusmn6 for Nusselt numberand plusmn8 friction factor as shown in Figures 20 and 21

Nu = 5236Pr04Re02357119910minus00881 (1 + 120601)0124 (17)

119891 = 76789Reminus0686119910minus0375 (1 + 120601)0198 (18)

64 Effect of Twist Tape Configuration The influence of andconic (quadrant parabolic half and triangular) cut twistedtape of twist ratio 119910 = 293 and cut depth 119889

119890= 05 cm

with 2 volume concentration of SiO2nanofluid on Nusselt

number and friction factor are shown in Figures 22 and 23Apparently from Figure 22 conic cut twist exhibits higherNusselt number than the typical twisted tape This can beexplained by the fact that conic cut twist tape generates swirlflow with efficient fluid mixing nearby their alternative cutswhile the typical twist tape causes swirl flow only The resultsalso reveal that the triangular cut twisted tape provides ahigherNusselt number comparedwith the othersThismeansthat the vortices behind the alternative cut edges of triangularcut twist tape give superior efficient fluid mixing resultingin further heat transfer enhancement From Figure 23 it canbe seen that friction factor decreases with the increase ofReynolds number and triangular cut twisted tape (VCT) giveshigher friction factor compared with all the other Reynoldsnumbers This implies that the influence of alternative cutsalong the edge of the triangular cut twisted tape promotesadditional wall shear stress due to flow mixing betweenthe fluids at the twist tape and tube wall In addition theexperimental data of conic cut twisted tapes with water (120601 =

0) and nanofluids (120601 = 2) were used to develop the

Nus

selt

num

ber (

Nu)

Reynolds number (Re)

RLT (y = 293) expTT (y = 293) exp

0

15

30

45

60

75

0 500 1000 1500 2000

Figure 12 Experimental Nusselt number of typical twist tape withRLT inserts

following correlations for Nusselt number and friction factorwith reasonable agreement as shown in Figures 24 and 25

For triangular cut twisted tape

Nu = 5387Pr04Re0229 (1 + 119908

119882)

00383

(1 +119889119890

119882)

minus0185

sdot (1 + 120601)0025

(19)

119891 = 6184Reminus067 (1 + 119908

119882)

0127

(1 +119889119890

119882)

minus0468

sdot (1 + 120601)0137

(20)

For parabolic half cut twisted tape

Nu = 5388Pr04Re0229 (1 + 119908

119882)

00384

(1 +119889119890

119882)

minus0184

sdot (1 + 120601)0025

(21)

119891 = 6876Reminus06771 (1 + 119908

119882)

0137

(1 +119889119890

119882)

minus0197

sdot (1 + 120601)00134

(22)

8 Journal of Nanomaterials

0

05

1

15

2

0 500 1000 1500 2000

Reynolds number (Re)

RLT (y = 293) expTT (y = 293) exp

Fric

tion

fact

or (f

)

Figure 13 Experimental friction factor of typical twist tape withRLT inserts

Nus

selt

num

ber (

Nu)

Reynolds number (Re)

DI water1 TiO2

2 TiO2

1 SiO2

2 SiO2

4

6

8

10

12

0 500 1000 1500 2000

Figure 14 Nusselt number versus Reynolds number for plain tubewith nanofluids

0

01

02

03

04

0 500 1000 1500 2000

Reynolds number (Re)

DI water1 TiO2

2 TiO2

1 SiO2

2 SiO2

Fric

tion

fact

or (f

)

Figure 15 Friction factor versus Reynolds number for plain tubewith nanofluids

0

4

8

12

16

0 4 8 12 16

Nus

selt

num

ber (

expe

rimen

tal)

Nusselt number (predicted)

DI water1 TiO2

2 TiO2

1 SiO2

2 SiO2

+6

minus6

Figure 16 Comparison of experimental and predicted Nusseltnumber for plain tube

Journal of Nanomaterials 9

0

01

02

03

04

0 01 02 03 04

Fric

tion

fact

or (e

xper

imen

tal)

Friction factor (predicted)

DI water1 TiO2

2 TiO2

1 SiO2

2 SiO2

+8

minus8

Figure 17 Comparison of experimental and predicted frictionfactor for plain tube

30

35

40

45

50

55

60

0 500 1000 1500 2000

Nus

selt

num

ber (

Nu)

Reynolds number (Re)

DI water1 TiO2

2 TiO2

1 SiO2

2 SiO2

Figure 18 Nusselt number versus Reynolds number for nanofluidswith typical twist tape (119910 = 293)

0

025

05

075

1

125

15

0 500 1000 1500 2000

Reynolds number (Re)

DI water

Fric

tion

fact

or (f

)

1 TiO2

2 TiO21 SiO2

2 SiO2

Figure 19 Nusselt number versus Reynolds number for nanofluidswith typical twist tape (119910 = 293)

0

20

40

60

80

0 20 40 60 80

Nus

selt

num

ber (

expe

rimen

tal)

Nusselt number (predicted)

DI water1 TiO2 2 TiO2

1 SiO2

2 SiO2

+6

minus6

Figure 20 Comparison of experimental and predicted Nusseltnumber with typical twist tape

10 Journal of Nanomaterials

0

025

05

075

1

125

15

0 025 05 075 1 125 15

Fric

tion

fact

or (e

xper

imen

tal)

Friction factor (predicted)

DI water1 TiO2

2 TiO2

1 SiO2

2 SiO2

+8

+8

Figure 21 Comparison of experimental and predicted frictionfactor with typical twist tape

30

35

40

45

50

55

60

65

0 500 1000 1500 2000

Nus

selt

num

ber (

Nu)

Reynolds number (Re)

QCT (2 SiO2)PCT (2 SiO2)VCT (2 SiO2)

TT (2 SiO2)TT (DI water)

Figure 22 Nusselt number versus Reynolds number for typical andconic cut twist tapes

0

03

06

09

12

15

18

0 500 1000 1500 2000

Reynolds number (Re)

QCT (2 SiO2)PCT (2 SiO2)VCT (2 SiO2)

TT (DI water)TT (DI water)

Fric

tion

fact

or (f

)

Figure 23 Friction factor versus Reynolds number for typical andconic cut twist tapes

0

20

40

60

80

0 20 40 60 80

Nus

selt

num

ber (

expe

rimen

tal)

Nusselt number (predicted)

+8

minus8

QCT (2 SiO2)PCT ( SiO2)VCT (2 SiO2)

TT (2 SiO2)TT (DI water)

Figure 24 Comparison of experimental and predicted Nusseltnumber for typical and conic cut twist tapes

Journal of Nanomaterials 11

0

05

1

15

2

0 05 1 15 2

Fric

tion

fact

or (e

xper

imen

tal)

Friction factor (predicted)

QCT (2 SiO2)PCT (2 SiO2)VCT (2 SiO2)

TT (2 SiO2)TT (DI water)

+10

minus10

Figure 25 Comparison of experimental and predicted frictionfactor for typical and conic cut twist tapes

For quadrant cut twisted tape

Nu = 538Pr04Re0226 (1 + 119908

119882)

00387

(1 +119889119890

119882)

minus0187

sdot (1 + 120601)0027

(23)

119891 = 6913Reminus071 (1 + 119908

119882)

0127

(1 +119889119890

119882)

minus016

sdot (1 + 120601)031

(24)

65 Thermal Performance of Twist Tapes The performanceanalysis of typical and conic cut twisted tape inserts in lami-nar flow of SiO

2nanofluid was accomplished by evaluating

thermal performance factor for constant pumping powercondition Thermal performance factor (120578) at constantspumping power is defined as ratio of the convective heattransfer coefficient of the tube with turbulator or enhancingmethod to that of the plain tube The following thermalperformance factor for laminar proposed by [29] is used forperformance analysis

120578 =(NuNu

119900)

(119891119891119900)01666

(25)

where Nu 119891 Nu119900 and 119891

119900are the Nusselt numbers and

friction factors for a duct configuration with and withoutinserts respectively

2

3

4

5

6

0 500 1000 1500 2000

Reynolds number (Re)

QCT (2 SiO2)PCT (2 SiO2)VCT (2 SiO2) TT (2 SiO2)

TT (DI water)

Ther

mal

per

form

ance

fact

or (120578

)

Figure 26 Variation of the thermal performance factor of typicaland conic cut twist tape

Figure 26 shows the variation of thermal performancefactor with Reynolds number for 2 volume concentrationof SiO

2nanofluid The values of thermal performance factor

at all Reynolds were found to be greater than unity for bothtypical and conic cut twisted tape inserts This indicates thattwist tape inserts are feasible in terms of energy saving in lam-inar flow regime It is evident that the thermal performancefactor triangular cut twist tape at constant Reynolds numberis higher than other twist tapes This is due to the strongerturbulenceswirl flow generated by alternative cuts along theedge twist tape The thermal performance factor was foundto be decreasing with increases in Reynolds number Thisis because of the increase in pressure loss as the Reynoldsnumber increases

The experimental results showed that the thermal perfor-mance factor is around 513ndash416 for VCT 498ndash408 for PCT488ndash405 for QCT and 483ndash401 for TT when used with2 SiO

2nanofluid While the thermal performance factor

to be around 475ndash396 for TT with water Therefore theVCT insert shows better thermal performance when usedwith SiO

2nanofluid than other twist tapesThe experimental

results are used to derive the following correlations of thermalperformance factor using least square method of regressionanalysis These correlations are valid for laminar flow (Re lt

1500) of water and 2 volume concentration SiO2for typical

and conic cut twist tapesThe comparisons between the ther-mal performance factor values obtained from experimentaldata and those predicted from the above correlations are

12 Journal of Nanomaterials

3

4

5

6

3 4 5 6

QCT (2 SiO2)PCT (2 SiO2)VCT (2 SiO2) TT (2 SiO2)

TT (DI water)

+6

minus6

Ther

mal

per

form

ance

fact

or (e

xper

imen

tal)

Thermal performance factor (predicted)

Figure 27 Comparison of experimental and predicted thermalperformance for typical and conic cut twist tapes

shown in Figure 27 As shown the predicted data are in goodagreement with the experimental data

For VCT twisted tape

120578 = 5173Reminus0118 (1 + 119908

119882)

2483

(1 +119889119890

119882)

minus0247

sdot (1 + 120601SiO2

)00183

(26)

For PCT twisted tape

120578 = 5173Re00945 (1 + 119908

119882)

3113

(1 +119889119890

119882)

minus0247

sdot (1 + 120601SiO2

)00183

(27)

For QCT twisted tape

120578 = 5173Re0118 (1 + 119908

119882)

349

(1 +119889119890

119882)

minus0247

sdot (1 + 120601SiO2

)00183

(28)

For TT twisted tape with SiO nanofluid

120578 = 791Re0093 (1 + 120601SiO2

)1283

(29)

For TT twisted tape with deionized water

120578 = 791Re0093 (30)

7 Conclusions

Heat transfer friction and thermal performance characteris-tics of SiO

2and TiO

2nanofluids with two concentrations of

1 and 2 by volume in a circular tube fitted with a typicaland conic cut twist tape in the laminar regime have beenexperimentally investigated The main conclusions from thisexperimental study are as follows

(71) SiO2and TiO

2nanofluids of different volume con-

centration in plain tube give good enhancement inNusselt number compared to deionized water Thehigher enhancement inNusselt number is obtained bySiO2nanofluids with volume concentrations of 2

(72) At similar conditions the insertion of typical twisttape causes very significant convective heat transferenhancement in the laminar flow however furtherenhancement is observed by the simultaneous use ofnanofluid with twisted tape compared to the use oftwisted tape or nanofluid alone

(73) The use of nanofluid with the conic cut twist tapeprovides a considerably higher Nusselt number thanthat of nanofluid with the typical twist tape for allReynolds numbers examinedThe triangular cut twisttape offers higher heat transfer rate than the typicaltwist tape and other conic cut configurations

(74) Over the range investigated (Re = 220ndash1500) themaximum thermal performance factor of 513 isfound with the simultaneous use of the triangulartwist tape with SiO

2nanofluid with 2 volume

concentration at Reynolds number of 220(75) The empirical correlations for the Nusselt number

friction factor and the thermal performance factorfor typical and conic cut twist tapes are developedand fitted with the experimental data of water andnanofluids

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

The authors would like to thank the National Universityof Malaysia and the Ministry of Higher Education for thefinancial support (FRGS12013TK07UKM011 and DPP-2013-114) to perform this investigation

References

[1] A Bejan and A D KrausHeat Transfer Handbook John Wileyamp Sons 2003

[2] I Singh and N Diwakar International Journal of AppliedResearch in Mechanical Engineering vol 3 pp 16ndash29 2013

[3] R M Manglik and A E Bergles ldquoHeat transfer and pressuredrop correlations for twisted-tape inserts in isothermal tubes

Journal of Nanomaterials 13

part Imdashlaminar flowsrdquo Journal of Heat Transfer vol 115 no 4pp 881ndash889 1993

[4] S K Saha and D Chakraborty ldquoHeat transfer and pressuredrop characteristics of laminar flow through a circular tubefitted with regularly spaced twisted tape elements with multipletwistsrdquo in Proceedings of the Heat andMass Transfer Conferencepp 313ndash318 Kanpur India 1997

[5] S Al-Fahed L M Chamra and W Chakroun ldquoPressure dropand heat transfer comparison for both microfin tube andtwisted-tape inserts in laminar flowrdquo ExperimentalThermal andFluid Science vol 18 no 4 pp 323ndash333 1998

[6] M S Lokanath and R D Misal ldquoAn experimental study on theperformance of plate heat exchanger and an augmented shelland tube heat exchanger for different types of fluids for marineapplicationsrdquo in Proceedings of the 5th ISHMT-ASME Heat andMass Transfer Conference pp 863ndash868 TataMcGraw-Hill NewDelhi India 2002

[7] P Sivashanmugam and S Suresh ldquoExperimental studies onheat transfer and friction factor characteristics of laminar flowthrough a circular tube fitted with helical screw-tape insertsrdquoApplied Thermal Engineering vol 26 no 16 pp 1990ndash19972006

[8] P Sivashanmugam and S Suresh ldquoExperimental studies onheat transfer and friction factor characteristics of laminar flowthrough a circular tube fitted with regularly spaced helicalscrew-tape insertsrdquo Experimental Thermal and Fluid Sciencevol 31 no 4 pp 301ndash308 2007

[9] S Jaisankar T K Radhakrishnan and K N Sheeba ldquoStudieson heat transfer and friction factor characteristics of ther-mosyphon solar water heating system with helical twistedtapesrdquo Energy vol 34 no 9 pp 1054ndash1064 2009

[10] A V N Kapatkar B D A S Padalkar and C S KasbeldquoExperimental investigation on heat transfer enhancement inlaminar flow in circular tube equipped with different insertsrdquoAMAE International Journal on Manufacturing and MaterialScience vol 1 pp 1ndash6 2011

[11] J Guo A Fan X Zhang and W Liu ldquoA numerical studyon heat transfer and friction factor characteristics of laminarflow in a circular tube fitted with center-cleared twisted taperdquoInternational Journal ofThermal Sciences vol 50 no 7 pp 1263ndash1270 2011

[12] K Wongcharee and S Eiamsa-ard ldquoFriction and heat trans-fer characteristics of laminar swirl flow through the roundtubes inserted with alternate clockwise and counter-clockwisetwisted-tapesrdquo International Communications in Heat andMassTransfer vol 38 no 3 pp 348ndash352 2011

[13] E Z Ibrahim ldquoAugmentation of laminar flow and heat transferin flat tubes by means of helical screw-tape insertsrdquo EnergyConversion and Management vol 52 no 1 pp 250ndash257 2011

[14] S U S Choi and J A Eastman ldquoEnhancing thermal con-ductivity of fluids with nanoparticlesrdquo in Developments andApplications of Non-Newtonian Flows D A Siguier and HP Wang Eds pp 99ndash105 American Society of MechanicalEngineers New York NY USA 1995

[15] C Y Tsai H T Chien P P Ding B Chan T Y Luh and PH Chen ldquoEffect of structural character of gold nanoparticles innanofluid on heat pipe thermal performancerdquoMaterials Lettersvol 58 no 9 pp 1461ndash1465 2004

[16] M-S Liu M C-C Lin C Y Tsai and C-C Wang ldquoEnhance-ment of thermal conductivity with Cu for nanofluids using

chemical reduction methodrdquo International Journal of Heat andMass Transfer vol 49 no 17-18 pp 3028ndash3033 2006

[17] E Tamjid andBHGuenther ldquoRheology and colloidal structureof silver nanoparticles dispersed in diethylene glycolrdquo PowderTechnology vol 197 no 1-2 pp 49ndash53 2010

[18] SM SMurshed K C Leong and C Yang ldquoEnhanced thermalconductivity of TiO

2water based nanofluidsrdquo International

Journal of Thermal Sciences vol 44 no 4 pp 367ndash373 2005[19] H Zhu C Zhang S Liu Y Tang and Y Yin ldquoEffects of

nanoparticle clustering and alignment on thermal conductiv-ities of Fe

3O4aqueous nanofluidsrdquo Applied Physics Letters vol

89 Article ID 023123 2006[20] J A Eastman U S Choi S Li L J Thompson and S Lee

ldquoEnhanced thermal conductivity through the development ofnanofluidsrdquoMRS Proceedings vol 457 1996

[21] M EMeibodi M Vafaie-Sefti AM Rashidi A Amrollahi MTabasi and H S Kalal ldquoSimple model for thermal conductivityof nanofluids using resistance model approachrdquo InternationalCommunications in Heat and Mass Transfer vol 37 no 5 pp555ndash559 2010

[22] G Pathipakka and P Sivashanmugam ldquoHeat transfer behaviourof nanofluids in a uniformly heated circular tube fittedwith heli-cal inserts in laminar flowrdquo Superlattices and Microstructuresvol 47 no 2 pp 349ndash360 2010

[23] K Wongcharee and S Eiamsa-ard ldquoEnhancement of heattransfer using CuOwater nanofluid and twisted tape withalternate axisrdquo International Communications in Heat and MassTransfer vol 38 no 6 pp 742ndash748 2011

[24] S Suresh K P Venkitaraj and P Selvakumar ldquoComparativestudy on thermal performance of helical screw tape inserts inlaminar flow using Al

2O3water and CuOwater nanofluidsrdquo

Superlattices and Microstructures vol 49 no 6 pp 608ndash6222011

[25] S D Salman A A H Kadhum M S Takriff and A BMohamad ldquoHeat transfer enhancement of laminar nanofluidsflow in a circular tube fitted with parabolic-cut twisted tapeinsertsrdquo The Scientific World Journal vol 2014 Article ID543231 7 pages 2014

[26] S D Salman A A H Kadhum M S Takriff and A BMohamad ldquoCFD simulation of heat transfer and friction factoraugmentation in a circular tube fitted with elliptic-cut twistedtape insertsrdquo Mathematical Problems in Engineering vol 2013Article ID 163839 7 pages 2013

[27] S D Salman A A H Kadhum M S Takriff and A BMohamad ldquoCFD analysis of Heat transfer and friction factorcharacteristics in a circular tube fitted with Quadrant-cuttwisted tape insertsrdquoMathematical Problems in Engineering vol2013 Article ID 273764 8 pages 2013

[28] F P Incropera D P Dewitt T L Bergman and A S LavineFundamentals of Heat and Mass Transfer John Wiley amp Sons2007

[29] H Usui Y Sano K Iwashita and A Isozaki ldquoEnhancement ofheat transfer by a combination of internally grooved rough tubeand twisted taperdquo International Chemical Engineering vol 26no 1 pp 97ndash104 1986

[30] J P Holman Experimental Methods for Engineers McGraw-Hill New York NY USA 2011

[31] R K Shah and A L London Laminar Flow Forced Convectionin Ducts Academic Press New York NY USA 1978

14 Journal of Nanomaterials

[32] P KNagarajan andP Sivashanmugam ldquoCFD simulation of heattransfer augmentation in a circular tube fitted with right-lefthelical inserts with spacerrdquo International Journal of ChemicalEngineering Research vol 1 pp 1ndash11 2009

[33] P Keblinski S R Phillpot S U S Choi and J A EastmanldquoMechanisms of heat flow in suspensions of nano-sized particles(nanofluids)rdquo International Journal of Heat and Mass Transfervol 45 no 4 pp 855ndash863 2002

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

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NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

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CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

Journal of Nanomaterials 3

wde

W

H

y = HW = 293

Figure 3 Parabolic half cut twisted tape (PCT)

wde

W

H

y = HW = 293

Figure 4 Triangular cut twist tape (VCT)

Table 1 Properties of nanoparticles at 20∘C

Material Density(gmcm3)

Specific heat(MJm3 K)

Thermalconductivity(WmK)

Particlesize(nm)

SiO2 22 745 14 15ndash20TiO2 39 650 112 15ndash20

Table 2Thermophysical properties of water and nanofluids at 25∘C

Fluid Density 120588(gmcm3)

Viscosity120583 (Nsm2)

Specificheat

(MJm3sdotK)

Thermalconductiv-

ity(WmsdotK)

Water 09969 0000963 41672 06096Water + 1 SiO2 1 0090 0001068 41412 06275Water + 2 SiO2 10211 0001197 41141 06288Water + 1 TiO2 10260 0001073 41483 06455Water + 2 TiO2 10550 0001188 41415 06672

for 1 hr and finally transferred to Ultrasonic bath (NEY-280H) for 1 hour in order to break up any potential clustersof nanoparticles and to achieve the required homogeneoussuspensions The thermophysical properties of nanofluidsfor desired volume concentration 120601 were measured 25∘Cusing portable density meter (Type DA-130N) POLYVISCrotational viscometer and Hot Disk Transient Plane SourceTPS 2500S Properties of the water and nanofluids are shownin Table 2

4 Experimental Setup

Theexperimental set-up as shown in Figure 7 consists of a testsection calming section chilled water tankwith cooling unitcirculation pump and pipe line system Both the calming sec-tion and test sections are made of straight stainless steel tube

Energy (keV)

O

SiElement

OK 5557 6871SiK 4443 3129

Total 100 100

0 1 2 3 4 5 6 7 8 9 10

Weight () Atomic ()

Inte

nsity

(cou

nt1

s)

Figure 5 EDX spectrum of SiO2nanoparticles

ElementOK 5121 7586TiK 4879 2414

Total 100 100

Ti

Ti

TiO

Energy (keV)

Inte

nsity

(cou

nt1

s)

Weight () Atomic ()

0 1 2 3 4 5 6 7 8 9 10

Figure 6 EDX spectrum of TiO2nanoparticles

with the dimensions 2000 and 1800mm long respectivelywith 254mm ID and 3333mm OD The calming section isused to eliminate the entrance effect The outside surface ofthe test section is brazed with fifteen thermowells made ofstainless steel with dimensions of 636mm ID 1mm thickand 120mm length which are mounted on the test section ataxial positions as shown in Figure 8 The test section tube iswound with ceramic beads coated electrical SWG Nichromeheating wire of resistance 18Ω Over the electrical windingtwo layers of asbestos rope and glass wool insulations are usedtominimize heat lossThe terminals of theNichromewire areattached to theVolteq 3KVA variac variable transformerwithinput single phase 220VAC 50Hz and output voltage can beadjusted from 0 to 150V ACThe amount of heat required intest section can be achieved by varying the output voltageFifteen calibrated RTD PT 100 type temperature sensors with075 accuracy are placed in the thermowells to measure theoutsidewall temperatures TwoRTDPT 100 type temperaturesensors are inserted near the centre of pipe to measure thebulk temperature of fluid at inlet and outlet of test sectionThe pressure drop across the test section is measured usingDMP3051 digital on-line differential pressure transmitter andthe velocity of water and nanofluids is measured by portableTDS-100H ultrasonic flowmeter The hot fluid after passingthrough the heated test section flows through chilled waterfor cooling and the desired temperature is controlled bytemperature controller 30m head centrifugal pump with by-pass valves is used to regulate the flow rate through the

4 Journal of Nanomaterials

Table 3 Technical details of experimental setup and test conditions

Setup and conditions Description(A) Experimental setup

(a) Inner tube inner diameter (di) 2540mm(b) Outer tube inner diameter (do) 3335mm(c) Test tube length 1800mm(d) Material of inner tube Stainless steel 304L

(f) Insulation material Asbestos rope and glasswool

(g) Temperature measurements RTD Pt 100 type(plusmn075 accuracy)

(h) Flow measurementsTDS-100H ultrasonicflowmeter (plusmn01

accuracy)

(i) Pressure measurementDMP3051 differentialpressure transmitter(plusmn02 accuracy)

(k) Heater capacity 3 KW(B) Typical twisted tape (TT)

(a) Material Aluminium(b) Tape width (119882) 245mm(c) Tape thickness 08mm(d) Tape pitch length (119867 360∘) 75mm(e) Twist ratio (119910 =119867di) 293

(C) Conic cut twisted tape(a) Material Aluminium(b) Tape width (119882) 245mm(c) Tape thickness 08mm(d) Tape pitch length (119867 360∘) 75mm(e) Twist ratio (119910 =119867di) 293(f) Quadrant cut twist tape (QCT) 119908 = 5mm de = 5mm(g) Parabolic cut twist tape (PCT) 119908 = 589mm de = 5mm(h) Triangular cut twist tape (VCT) 119908 = 785mm de = 5mm

(D) Test conditions(a) Reynolds number (Re) 200 to 1500(b) Type of flow in inner tube Laminar

test section The details of experimental setup and operatingconditions are summarized in Table 3

5 Data Reduction

The measured data were used to calculate the Nusselt num-ber friction factor and thermal performance factor in thelaminar flow regime for Reynolds number ranging from 200to 1500

The heat transfer rate obtained from the hot fluid in thetest section tubes can be expressed as

119876conv = 119898119888119901(119879out minus 119879in) (1)

The heat transfer rate in terms of mean convective heattransfer coefficient (ℎ) can be expressed as

119876conv = ℎ119860 (119904minus 119879119887) (2)

The heat flux becomes

11990210158401015840

119904=119876conv119860

= ℎ (119904minus 119879119887) (3)

where 119879119887is a mean bulk flow temperature 119879

119887= (119879out +119879in)2

Thenmean inner wall surface temperature (119904) of the test

section is calculated from 15 stations of surface temperatureslocated between the inlet and the outlet of the test sectionusing the following equation

119904= sum

119879119904119894(119909)

15 (4)

where 119879119904119894(119909) is a local inner wall temperature which can

be calculated from steady one dimensional heat conductionequation in cylindrical coordinate [28]

1

119903

119889

119889119903(119896119903

119889119879

119889119903) = 0 (5)

The solution of this equation with constant heat flux bound-ary condition at the wall becomes

119879119904119894(119909) = 119879

119904119900(119909) minus

119876conv ln (119863119900119863119894)2120587119896119871

(6)

where 119879119904119900(119909) represent the local outer wall temperatures

measured by RTD PT 100 type temperature sensors 119863119900 119863119894

are the outer and inner tube diameters 119896 is the thermalconductivity of the test section wall and 119871 is the length ofthe test section

The average Nusselt number (Nu) can be estimated fromthe following equation

Nu =ℎavg119863119894

119896119891

(7)

The average heat transfer coefficient can be determined from(7)

ℎavg =11990210158401015840

119904

(119904minus 119879119887) (8)

The pressure drop (Δ119901) measured across the test sectionwas used to calculate friction factor (119891) using the followingequation

119891119863=2Δ119901119863

119894

1198711205881199062 (9)

The performance evaluation analysis for laminar flow at thesame pumping power is given by the following correlationproposed by Usui et al [29]

120578 =(NuNu

119900)

(119891119891119900)01666

(10)

Journal of Nanomaterials 5

Air chiller

NotebookData logger

Flow

met

er

Set of thermocouples

PumpCold water tank

Valve

Valve

Test section

Pressure transmitter

Calming section

Power supply

Volt meter amp meter and power meter

Figure 7 Schematic diagram of the experimental setup

Figure 8 Test section with thermocouple locations

where Nu and 119891 are respectively the Nusselt number andfriction factor of the tube with enhancing factor (nanofluidandor twisted tape) while Nu

119900and 119891

119900are respectively the

Nusselt number and friction factor of the plain tubeA standard uncertainty analysis was conducted for each

measurement using Kline-McClintock method [30] Themaximum uncertainties for Reynolds number Nusselt num-ber and friction factor were calculated to be 61 848 and24 respectively

6 Results and Discussions

61 Experimental Setup Validation To evaluate the reliabilityof the present experimental setup the experimental results

of pure water in plain tube without twisted tape underlaminar flow conditions were validated with shah equation[31] and Hagen-Poiseuille equation [28] The results showedreasonable agreement with the local Nusselt number (Nu

119909)

and friction factor (119891) as shown in Figures 9 and 10

Nu119909= 1953119909

minus13

lowastfor 119909lowastle 003

Nu119909= 4364 +

00722

119909lowast

for 119909lowastgt 003

(11)

119891 =64

Re (12)

The results of Nusselt number for plain tube with typicaltwisted tape (119910 = 293) were also validated with Manglik andBergle equation [3] As shown in Figure 11 the data obtainedwere found to be in good agreement with the availablecorrelation For the proof of the present typical twisted tapeNusselt number of a tube fitted with the present typicaltwisted tapes was compared with experimental data of right-left helical twist tape [32] as shown in Figures 12 and 13Apparently the typical twist tape offered an additional heattransfer enhancement with less skin friction factor

6 Journal of Nanomaterials

Axial distance x (m)

Re = 220 experimentalRe = 730 experimentalRe = 1460 experimental

Re = 220 theoreticalRe = 720 theoreticalRe = 1460 theoretical

0

5

10

15

20

25

30

0 05 1 15 2

Loca

l Nus

selt

num

ber (

Nu x

)

Figure 9 Comparison between measured and calculated localNusselt number (Nu

119909) using DI-Water

62 Effect of Nanoparticle Volume Concentration in PlainTube Experiments were performed to study heat transferenhancements in plain tube with laminar flow of deionizedwater and SiO

2and TiO

2nanofluids of 1 and 2 volume

concentration The obtained results of Nusselt number andfriction factor are elaborated in Figures 14 and 15 FromFigure 14 it can be seen that the Nusselt number increasedwith the increase of nanoparticle concentration andReynoldsnumber This means that the presence of nanoparticlesincreases the energy exchange rates in the fluid with penaltyon the wall shear stress due to Brownian motion [33] theincreases of Reynolds number increase random movementsof the fluid and consequently enhance the thermal dispersionof the flow Evidently SiO

2nanofluid with 2 volume

concentration offered highest Nusselt number followed byTiO2and water respectively On other hand Figure 15 shows

slightly augmentation in friction factor value with increasesof nanoparticles concentration This means that the pres-ence of nanoparticles volume fraction increases nanofluidviscosity with wall shear stressThe experimental results wereused to derive the following correlations of Nusselt numberand friction for water (120601 = 0) SiO

2and TiO

2nanofluids

(120601 le 2) The predicted values of these correlations showreasonable agreement with the experimental results as shownin Figures 16 and 17

For SiO2nanofluid

Nu = 06116Pr04Re02795 (1 + 120601)347 (13)

119891 = 63236Reminus0994 (1 + 120601) (14)

Dar

cy fr

ictio

n fa

ctor

(f)

0

005

01

015

02

025

03

035

0 500 1000 1500 2000

Reynolds number (Re)

Experimental dataDarcy friction factor

Figure 10 Friction factor across the test section using DI-water asthe working fluid

For TiO2nanofluid

Nu = 06116Pr04Re02795 (1 + 120601)147 (15)

119891 = 63236Reminus0994 (1 + 120601) (16)

63 Effect of Nanoparticle Volume Concentration with TwistTape Variations ofNusselt number and friction factor versusReynolds number for laminar flow of deionized water SiO

2

and TiO2nanofluids of 1 and 2 volume concentration

in tube fitted with typical twist tape (119910 = 293) areshown in Figures 18 and 19 Evidently Figure 18 shows thatthe combined use of nanofluid with twist tape producesfurther augment in heat transfer coefficient than eithernanofluid or twist tape individually The simultaneous use ofnanofluid with twist tape increases the thermal conductivityand viscosity of working fluid as well as increasing swirlflow pathThus greater fluid mixing and higher heat transfercoefficient are produced Eventually SiO

2nanofluid with 2

volume concentration with typical twist tape offered a higherNusselt number compared with the others As shown inFigure 19 the friction factor decreases with the increase ofReynolds number for water and different volume fractionsof nanoparticles Based on the experimental results thefollowing correlations of Nusselt number and friction factorwere derived The correlations are valid for laminar flow(Re lt 1500) 120601 le 2 volume concentration (120601 = 0 for water)of SiO

2and TiO

2nanofluid and typical twist tape of twist

ratio 119910 = 293 The predicted data were in good agreement

Journal of Nanomaterials 7N

usse

lt nu

mbe

r (ex

perim

enta

l)

Nusselt number (Manglik and Bergles equation)

y = 293

+15

minus15

0

20

40

60

80

100

0 20 40 60 80 100

Figure 11 Comparison of experimental and predicted Nusseltnumber of the plain tube fitted with typical twisted tape

with the experimental data within plusmn6 for Nusselt numberand plusmn8 friction factor as shown in Figures 20 and 21

Nu = 5236Pr04Re02357119910minus00881 (1 + 120601)0124 (17)

119891 = 76789Reminus0686119910minus0375 (1 + 120601)0198 (18)

64 Effect of Twist Tape Configuration The influence of andconic (quadrant parabolic half and triangular) cut twistedtape of twist ratio 119910 = 293 and cut depth 119889

119890= 05 cm

with 2 volume concentration of SiO2nanofluid on Nusselt

number and friction factor are shown in Figures 22 and 23Apparently from Figure 22 conic cut twist exhibits higherNusselt number than the typical twisted tape This can beexplained by the fact that conic cut twist tape generates swirlflow with efficient fluid mixing nearby their alternative cutswhile the typical twist tape causes swirl flow only The resultsalso reveal that the triangular cut twisted tape provides ahigherNusselt number comparedwith the othersThismeansthat the vortices behind the alternative cut edges of triangularcut twist tape give superior efficient fluid mixing resultingin further heat transfer enhancement From Figure 23 it canbe seen that friction factor decreases with the increase ofReynolds number and triangular cut twisted tape (VCT) giveshigher friction factor compared with all the other Reynoldsnumbers This implies that the influence of alternative cutsalong the edge of the triangular cut twisted tape promotesadditional wall shear stress due to flow mixing betweenthe fluids at the twist tape and tube wall In addition theexperimental data of conic cut twisted tapes with water (120601 =

0) and nanofluids (120601 = 2) were used to develop the

Nus

selt

num

ber (

Nu)

Reynolds number (Re)

RLT (y = 293) expTT (y = 293) exp

0

15

30

45

60

75

0 500 1000 1500 2000

Figure 12 Experimental Nusselt number of typical twist tape withRLT inserts

following correlations for Nusselt number and friction factorwith reasonable agreement as shown in Figures 24 and 25

For triangular cut twisted tape

Nu = 5387Pr04Re0229 (1 + 119908

119882)

00383

(1 +119889119890

119882)

minus0185

sdot (1 + 120601)0025

(19)

119891 = 6184Reminus067 (1 + 119908

119882)

0127

(1 +119889119890

119882)

minus0468

sdot (1 + 120601)0137

(20)

For parabolic half cut twisted tape

Nu = 5388Pr04Re0229 (1 + 119908

119882)

00384

(1 +119889119890

119882)

minus0184

sdot (1 + 120601)0025

(21)

119891 = 6876Reminus06771 (1 + 119908

119882)

0137

(1 +119889119890

119882)

minus0197

sdot (1 + 120601)00134

(22)

8 Journal of Nanomaterials

0

05

1

15

2

0 500 1000 1500 2000

Reynolds number (Re)

RLT (y = 293) expTT (y = 293) exp

Fric

tion

fact

or (f

)

Figure 13 Experimental friction factor of typical twist tape withRLT inserts

Nus

selt

num

ber (

Nu)

Reynolds number (Re)

DI water1 TiO2

2 TiO2

1 SiO2

2 SiO2

4

6

8

10

12

0 500 1000 1500 2000

Figure 14 Nusselt number versus Reynolds number for plain tubewith nanofluids

0

01

02

03

04

0 500 1000 1500 2000

Reynolds number (Re)

DI water1 TiO2

2 TiO2

1 SiO2

2 SiO2

Fric

tion

fact

or (f

)

Figure 15 Friction factor versus Reynolds number for plain tubewith nanofluids

0

4

8

12

16

0 4 8 12 16

Nus

selt

num

ber (

expe

rimen

tal)

Nusselt number (predicted)

DI water1 TiO2

2 TiO2

1 SiO2

2 SiO2

+6

minus6

Figure 16 Comparison of experimental and predicted Nusseltnumber for plain tube

Journal of Nanomaterials 9

0

01

02

03

04

0 01 02 03 04

Fric

tion

fact

or (e

xper

imen

tal)

Friction factor (predicted)

DI water1 TiO2

2 TiO2

1 SiO2

2 SiO2

+8

minus8

Figure 17 Comparison of experimental and predicted frictionfactor for plain tube

30

35

40

45

50

55

60

0 500 1000 1500 2000

Nus

selt

num

ber (

Nu)

Reynolds number (Re)

DI water1 TiO2

2 TiO2

1 SiO2

2 SiO2

Figure 18 Nusselt number versus Reynolds number for nanofluidswith typical twist tape (119910 = 293)

0

025

05

075

1

125

15

0 500 1000 1500 2000

Reynolds number (Re)

DI water

Fric

tion

fact

or (f

)

1 TiO2

2 TiO21 SiO2

2 SiO2

Figure 19 Nusselt number versus Reynolds number for nanofluidswith typical twist tape (119910 = 293)

0

20

40

60

80

0 20 40 60 80

Nus

selt

num

ber (

expe

rimen

tal)

Nusselt number (predicted)

DI water1 TiO2 2 TiO2

1 SiO2

2 SiO2

+6

minus6

Figure 20 Comparison of experimental and predicted Nusseltnumber with typical twist tape

10 Journal of Nanomaterials

0

025

05

075

1

125

15

0 025 05 075 1 125 15

Fric

tion

fact

or (e

xper

imen

tal)

Friction factor (predicted)

DI water1 TiO2

2 TiO2

1 SiO2

2 SiO2

+8

+8

Figure 21 Comparison of experimental and predicted frictionfactor with typical twist tape

30

35

40

45

50

55

60

65

0 500 1000 1500 2000

Nus

selt

num

ber (

Nu)

Reynolds number (Re)

QCT (2 SiO2)PCT (2 SiO2)VCT (2 SiO2)

TT (2 SiO2)TT (DI water)

Figure 22 Nusselt number versus Reynolds number for typical andconic cut twist tapes

0

03

06

09

12

15

18

0 500 1000 1500 2000

Reynolds number (Re)

QCT (2 SiO2)PCT (2 SiO2)VCT (2 SiO2)

TT (DI water)TT (DI water)

Fric

tion

fact

or (f

)

Figure 23 Friction factor versus Reynolds number for typical andconic cut twist tapes

0

20

40

60

80

0 20 40 60 80

Nus

selt

num

ber (

expe

rimen

tal)

Nusselt number (predicted)

+8

minus8

QCT (2 SiO2)PCT ( SiO2)VCT (2 SiO2)

TT (2 SiO2)TT (DI water)

Figure 24 Comparison of experimental and predicted Nusseltnumber for typical and conic cut twist tapes

Journal of Nanomaterials 11

0

05

1

15

2

0 05 1 15 2

Fric

tion

fact

or (e

xper

imen

tal)

Friction factor (predicted)

QCT (2 SiO2)PCT (2 SiO2)VCT (2 SiO2)

TT (2 SiO2)TT (DI water)

+10

minus10

Figure 25 Comparison of experimental and predicted frictionfactor for typical and conic cut twist tapes

For quadrant cut twisted tape

Nu = 538Pr04Re0226 (1 + 119908

119882)

00387

(1 +119889119890

119882)

minus0187

sdot (1 + 120601)0027

(23)

119891 = 6913Reminus071 (1 + 119908

119882)

0127

(1 +119889119890

119882)

minus016

sdot (1 + 120601)031

(24)

65 Thermal Performance of Twist Tapes The performanceanalysis of typical and conic cut twisted tape inserts in lami-nar flow of SiO

2nanofluid was accomplished by evaluating

thermal performance factor for constant pumping powercondition Thermal performance factor (120578) at constantspumping power is defined as ratio of the convective heattransfer coefficient of the tube with turbulator or enhancingmethod to that of the plain tube The following thermalperformance factor for laminar proposed by [29] is used forperformance analysis

120578 =(NuNu

119900)

(119891119891119900)01666

(25)

where Nu 119891 Nu119900 and 119891

119900are the Nusselt numbers and

friction factors for a duct configuration with and withoutinserts respectively

2

3

4

5

6

0 500 1000 1500 2000

Reynolds number (Re)

QCT (2 SiO2)PCT (2 SiO2)VCT (2 SiO2) TT (2 SiO2)

TT (DI water)

Ther

mal

per

form

ance

fact

or (120578

)

Figure 26 Variation of the thermal performance factor of typicaland conic cut twist tape

Figure 26 shows the variation of thermal performancefactor with Reynolds number for 2 volume concentrationof SiO

2nanofluid The values of thermal performance factor

at all Reynolds were found to be greater than unity for bothtypical and conic cut twisted tape inserts This indicates thattwist tape inserts are feasible in terms of energy saving in lam-inar flow regime It is evident that the thermal performancefactor triangular cut twist tape at constant Reynolds numberis higher than other twist tapes This is due to the strongerturbulenceswirl flow generated by alternative cuts along theedge twist tape The thermal performance factor was foundto be decreasing with increases in Reynolds number Thisis because of the increase in pressure loss as the Reynoldsnumber increases

The experimental results showed that the thermal perfor-mance factor is around 513ndash416 for VCT 498ndash408 for PCT488ndash405 for QCT and 483ndash401 for TT when used with2 SiO

2nanofluid While the thermal performance factor

to be around 475ndash396 for TT with water Therefore theVCT insert shows better thermal performance when usedwith SiO

2nanofluid than other twist tapesThe experimental

results are used to derive the following correlations of thermalperformance factor using least square method of regressionanalysis These correlations are valid for laminar flow (Re lt

1500) of water and 2 volume concentration SiO2for typical

and conic cut twist tapesThe comparisons between the ther-mal performance factor values obtained from experimentaldata and those predicted from the above correlations are

12 Journal of Nanomaterials

3

4

5

6

3 4 5 6

QCT (2 SiO2)PCT (2 SiO2)VCT (2 SiO2) TT (2 SiO2)

TT (DI water)

+6

minus6

Ther

mal

per

form

ance

fact

or (e

xper

imen

tal)

Thermal performance factor (predicted)

Figure 27 Comparison of experimental and predicted thermalperformance for typical and conic cut twist tapes

shown in Figure 27 As shown the predicted data are in goodagreement with the experimental data

For VCT twisted tape

120578 = 5173Reminus0118 (1 + 119908

119882)

2483

(1 +119889119890

119882)

minus0247

sdot (1 + 120601SiO2

)00183

(26)

For PCT twisted tape

120578 = 5173Re00945 (1 + 119908

119882)

3113

(1 +119889119890

119882)

minus0247

sdot (1 + 120601SiO2

)00183

(27)

For QCT twisted tape

120578 = 5173Re0118 (1 + 119908

119882)

349

(1 +119889119890

119882)

minus0247

sdot (1 + 120601SiO2

)00183

(28)

For TT twisted tape with SiO nanofluid

120578 = 791Re0093 (1 + 120601SiO2

)1283

(29)

For TT twisted tape with deionized water

120578 = 791Re0093 (30)

7 Conclusions

Heat transfer friction and thermal performance characteris-tics of SiO

2and TiO

2nanofluids with two concentrations of

1 and 2 by volume in a circular tube fitted with a typicaland conic cut twist tape in the laminar regime have beenexperimentally investigated The main conclusions from thisexperimental study are as follows

(71) SiO2and TiO

2nanofluids of different volume con-

centration in plain tube give good enhancement inNusselt number compared to deionized water Thehigher enhancement inNusselt number is obtained bySiO2nanofluids with volume concentrations of 2

(72) At similar conditions the insertion of typical twisttape causes very significant convective heat transferenhancement in the laminar flow however furtherenhancement is observed by the simultaneous use ofnanofluid with twisted tape compared to the use oftwisted tape or nanofluid alone

(73) The use of nanofluid with the conic cut twist tapeprovides a considerably higher Nusselt number thanthat of nanofluid with the typical twist tape for allReynolds numbers examinedThe triangular cut twisttape offers higher heat transfer rate than the typicaltwist tape and other conic cut configurations

(74) Over the range investigated (Re = 220ndash1500) themaximum thermal performance factor of 513 isfound with the simultaneous use of the triangulartwist tape with SiO

2nanofluid with 2 volume

concentration at Reynolds number of 220(75) The empirical correlations for the Nusselt number

friction factor and the thermal performance factorfor typical and conic cut twist tapes are developedand fitted with the experimental data of water andnanofluids

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

The authors would like to thank the National Universityof Malaysia and the Ministry of Higher Education for thefinancial support (FRGS12013TK07UKM011 and DPP-2013-114) to perform this investigation

References

[1] A Bejan and A D KrausHeat Transfer Handbook John Wileyamp Sons 2003

[2] I Singh and N Diwakar International Journal of AppliedResearch in Mechanical Engineering vol 3 pp 16ndash29 2013

[3] R M Manglik and A E Bergles ldquoHeat transfer and pressuredrop correlations for twisted-tape inserts in isothermal tubes

Journal of Nanomaterials 13

part Imdashlaminar flowsrdquo Journal of Heat Transfer vol 115 no 4pp 881ndash889 1993

[4] S K Saha and D Chakraborty ldquoHeat transfer and pressuredrop characteristics of laminar flow through a circular tubefitted with regularly spaced twisted tape elements with multipletwistsrdquo in Proceedings of the Heat andMass Transfer Conferencepp 313ndash318 Kanpur India 1997

[5] S Al-Fahed L M Chamra and W Chakroun ldquoPressure dropand heat transfer comparison for both microfin tube andtwisted-tape inserts in laminar flowrdquo ExperimentalThermal andFluid Science vol 18 no 4 pp 323ndash333 1998

[6] M S Lokanath and R D Misal ldquoAn experimental study on theperformance of plate heat exchanger and an augmented shelland tube heat exchanger for different types of fluids for marineapplicationsrdquo in Proceedings of the 5th ISHMT-ASME Heat andMass Transfer Conference pp 863ndash868 TataMcGraw-Hill NewDelhi India 2002

[7] P Sivashanmugam and S Suresh ldquoExperimental studies onheat transfer and friction factor characteristics of laminar flowthrough a circular tube fitted with helical screw-tape insertsrdquoApplied Thermal Engineering vol 26 no 16 pp 1990ndash19972006

[8] P Sivashanmugam and S Suresh ldquoExperimental studies onheat transfer and friction factor characteristics of laminar flowthrough a circular tube fitted with regularly spaced helicalscrew-tape insertsrdquo Experimental Thermal and Fluid Sciencevol 31 no 4 pp 301ndash308 2007

[9] S Jaisankar T K Radhakrishnan and K N Sheeba ldquoStudieson heat transfer and friction factor characteristics of ther-mosyphon solar water heating system with helical twistedtapesrdquo Energy vol 34 no 9 pp 1054ndash1064 2009

[10] A V N Kapatkar B D A S Padalkar and C S KasbeldquoExperimental investigation on heat transfer enhancement inlaminar flow in circular tube equipped with different insertsrdquoAMAE International Journal on Manufacturing and MaterialScience vol 1 pp 1ndash6 2011

[11] J Guo A Fan X Zhang and W Liu ldquoA numerical studyon heat transfer and friction factor characteristics of laminarflow in a circular tube fitted with center-cleared twisted taperdquoInternational Journal ofThermal Sciences vol 50 no 7 pp 1263ndash1270 2011

[12] K Wongcharee and S Eiamsa-ard ldquoFriction and heat trans-fer characteristics of laminar swirl flow through the roundtubes inserted with alternate clockwise and counter-clockwisetwisted-tapesrdquo International Communications in Heat andMassTransfer vol 38 no 3 pp 348ndash352 2011

[13] E Z Ibrahim ldquoAugmentation of laminar flow and heat transferin flat tubes by means of helical screw-tape insertsrdquo EnergyConversion and Management vol 52 no 1 pp 250ndash257 2011

[14] S U S Choi and J A Eastman ldquoEnhancing thermal con-ductivity of fluids with nanoparticlesrdquo in Developments andApplications of Non-Newtonian Flows D A Siguier and HP Wang Eds pp 99ndash105 American Society of MechanicalEngineers New York NY USA 1995

[15] C Y Tsai H T Chien P P Ding B Chan T Y Luh and PH Chen ldquoEffect of structural character of gold nanoparticles innanofluid on heat pipe thermal performancerdquoMaterials Lettersvol 58 no 9 pp 1461ndash1465 2004

[16] M-S Liu M C-C Lin C Y Tsai and C-C Wang ldquoEnhance-ment of thermal conductivity with Cu for nanofluids using

chemical reduction methodrdquo International Journal of Heat andMass Transfer vol 49 no 17-18 pp 3028ndash3033 2006

[17] E Tamjid andBHGuenther ldquoRheology and colloidal structureof silver nanoparticles dispersed in diethylene glycolrdquo PowderTechnology vol 197 no 1-2 pp 49ndash53 2010

[18] SM SMurshed K C Leong and C Yang ldquoEnhanced thermalconductivity of TiO

2water based nanofluidsrdquo International

Journal of Thermal Sciences vol 44 no 4 pp 367ndash373 2005[19] H Zhu C Zhang S Liu Y Tang and Y Yin ldquoEffects of

nanoparticle clustering and alignment on thermal conductiv-ities of Fe

3O4aqueous nanofluidsrdquo Applied Physics Letters vol

89 Article ID 023123 2006[20] J A Eastman U S Choi S Li L J Thompson and S Lee

ldquoEnhanced thermal conductivity through the development ofnanofluidsrdquoMRS Proceedings vol 457 1996

[21] M EMeibodi M Vafaie-Sefti AM Rashidi A Amrollahi MTabasi and H S Kalal ldquoSimple model for thermal conductivityof nanofluids using resistance model approachrdquo InternationalCommunications in Heat and Mass Transfer vol 37 no 5 pp555ndash559 2010

[22] G Pathipakka and P Sivashanmugam ldquoHeat transfer behaviourof nanofluids in a uniformly heated circular tube fittedwith heli-cal inserts in laminar flowrdquo Superlattices and Microstructuresvol 47 no 2 pp 349ndash360 2010

[23] K Wongcharee and S Eiamsa-ard ldquoEnhancement of heattransfer using CuOwater nanofluid and twisted tape withalternate axisrdquo International Communications in Heat and MassTransfer vol 38 no 6 pp 742ndash748 2011

[24] S Suresh K P Venkitaraj and P Selvakumar ldquoComparativestudy on thermal performance of helical screw tape inserts inlaminar flow using Al

2O3water and CuOwater nanofluidsrdquo

Superlattices and Microstructures vol 49 no 6 pp 608ndash6222011

[25] S D Salman A A H Kadhum M S Takriff and A BMohamad ldquoHeat transfer enhancement of laminar nanofluidsflow in a circular tube fitted with parabolic-cut twisted tapeinsertsrdquo The Scientific World Journal vol 2014 Article ID543231 7 pages 2014

[26] S D Salman A A H Kadhum M S Takriff and A BMohamad ldquoCFD simulation of heat transfer and friction factoraugmentation in a circular tube fitted with elliptic-cut twistedtape insertsrdquo Mathematical Problems in Engineering vol 2013Article ID 163839 7 pages 2013

[27] S D Salman A A H Kadhum M S Takriff and A BMohamad ldquoCFD analysis of Heat transfer and friction factorcharacteristics in a circular tube fitted with Quadrant-cuttwisted tape insertsrdquoMathematical Problems in Engineering vol2013 Article ID 273764 8 pages 2013

[28] F P Incropera D P Dewitt T L Bergman and A S LavineFundamentals of Heat and Mass Transfer John Wiley amp Sons2007

[29] H Usui Y Sano K Iwashita and A Isozaki ldquoEnhancement ofheat transfer by a combination of internally grooved rough tubeand twisted taperdquo International Chemical Engineering vol 26no 1 pp 97ndash104 1986

[30] J P Holman Experimental Methods for Engineers McGraw-Hill New York NY USA 2011

[31] R K Shah and A L London Laminar Flow Forced Convectionin Ducts Academic Press New York NY USA 1978

14 Journal of Nanomaterials

[32] P KNagarajan andP Sivashanmugam ldquoCFD simulation of heattransfer augmentation in a circular tube fitted with right-lefthelical inserts with spacerrdquo International Journal of ChemicalEngineering Research vol 1 pp 1ndash11 2009

[33] P Keblinski S R Phillpot S U S Choi and J A EastmanldquoMechanisms of heat flow in suspensions of nano-sized particles(nanofluids)rdquo International Journal of Heat and Mass Transfervol 45 no 4 pp 855ndash863 2002

Submit your manuscripts athttpwwwhindawicom

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MaterialsJournal of

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Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

4 Journal of Nanomaterials

Table 3 Technical details of experimental setup and test conditions

Setup and conditions Description(A) Experimental setup

(a) Inner tube inner diameter (di) 2540mm(b) Outer tube inner diameter (do) 3335mm(c) Test tube length 1800mm(d) Material of inner tube Stainless steel 304L

(f) Insulation material Asbestos rope and glasswool

(g) Temperature measurements RTD Pt 100 type(plusmn075 accuracy)

(h) Flow measurementsTDS-100H ultrasonicflowmeter (plusmn01

accuracy)

(i) Pressure measurementDMP3051 differentialpressure transmitter(plusmn02 accuracy)

(k) Heater capacity 3 KW(B) Typical twisted tape (TT)

(a) Material Aluminium(b) Tape width (119882) 245mm(c) Tape thickness 08mm(d) Tape pitch length (119867 360∘) 75mm(e) Twist ratio (119910 =119867di) 293

(C) Conic cut twisted tape(a) Material Aluminium(b) Tape width (119882) 245mm(c) Tape thickness 08mm(d) Tape pitch length (119867 360∘) 75mm(e) Twist ratio (119910 =119867di) 293(f) Quadrant cut twist tape (QCT) 119908 = 5mm de = 5mm(g) Parabolic cut twist tape (PCT) 119908 = 589mm de = 5mm(h) Triangular cut twist tape (VCT) 119908 = 785mm de = 5mm

(D) Test conditions(a) Reynolds number (Re) 200 to 1500(b) Type of flow in inner tube Laminar

test section The details of experimental setup and operatingconditions are summarized in Table 3

5 Data Reduction

The measured data were used to calculate the Nusselt num-ber friction factor and thermal performance factor in thelaminar flow regime for Reynolds number ranging from 200to 1500

The heat transfer rate obtained from the hot fluid in thetest section tubes can be expressed as

119876conv = 119898119888119901(119879out minus 119879in) (1)

The heat transfer rate in terms of mean convective heattransfer coefficient (ℎ) can be expressed as

119876conv = ℎ119860 (119904minus 119879119887) (2)

The heat flux becomes

11990210158401015840

119904=119876conv119860

= ℎ (119904minus 119879119887) (3)

where 119879119887is a mean bulk flow temperature 119879

119887= (119879out +119879in)2

Thenmean inner wall surface temperature (119904) of the test

section is calculated from 15 stations of surface temperatureslocated between the inlet and the outlet of the test sectionusing the following equation

119904= sum

119879119904119894(119909)

15 (4)

where 119879119904119894(119909) is a local inner wall temperature which can

be calculated from steady one dimensional heat conductionequation in cylindrical coordinate [28]

1

119903

119889

119889119903(119896119903

119889119879

119889119903) = 0 (5)

The solution of this equation with constant heat flux bound-ary condition at the wall becomes

119879119904119894(119909) = 119879

119904119900(119909) minus

119876conv ln (119863119900119863119894)2120587119896119871

(6)

where 119879119904119900(119909) represent the local outer wall temperatures

measured by RTD PT 100 type temperature sensors 119863119900 119863119894

are the outer and inner tube diameters 119896 is the thermalconductivity of the test section wall and 119871 is the length ofthe test section

The average Nusselt number (Nu) can be estimated fromthe following equation

Nu =ℎavg119863119894

119896119891

(7)

The average heat transfer coefficient can be determined from(7)

ℎavg =11990210158401015840

119904

(119904minus 119879119887) (8)

The pressure drop (Δ119901) measured across the test sectionwas used to calculate friction factor (119891) using the followingequation

119891119863=2Δ119901119863

119894

1198711205881199062 (9)

The performance evaluation analysis for laminar flow at thesame pumping power is given by the following correlationproposed by Usui et al [29]

120578 =(NuNu

119900)

(119891119891119900)01666

(10)

Journal of Nanomaterials 5

Air chiller

NotebookData logger

Flow

met

er

Set of thermocouples

PumpCold water tank

Valve

Valve

Test section

Pressure transmitter

Calming section

Power supply

Volt meter amp meter and power meter

Figure 7 Schematic diagram of the experimental setup

Figure 8 Test section with thermocouple locations

where Nu and 119891 are respectively the Nusselt number andfriction factor of the tube with enhancing factor (nanofluidandor twisted tape) while Nu

119900and 119891

119900are respectively the

Nusselt number and friction factor of the plain tubeA standard uncertainty analysis was conducted for each

measurement using Kline-McClintock method [30] Themaximum uncertainties for Reynolds number Nusselt num-ber and friction factor were calculated to be 61 848 and24 respectively

6 Results and Discussions

61 Experimental Setup Validation To evaluate the reliabilityof the present experimental setup the experimental results

of pure water in plain tube without twisted tape underlaminar flow conditions were validated with shah equation[31] and Hagen-Poiseuille equation [28] The results showedreasonable agreement with the local Nusselt number (Nu

119909)

and friction factor (119891) as shown in Figures 9 and 10

Nu119909= 1953119909

minus13

lowastfor 119909lowastle 003

Nu119909= 4364 +

00722

119909lowast

for 119909lowastgt 003

(11)

119891 =64

Re (12)

The results of Nusselt number for plain tube with typicaltwisted tape (119910 = 293) were also validated with Manglik andBergle equation [3] As shown in Figure 11 the data obtainedwere found to be in good agreement with the availablecorrelation For the proof of the present typical twisted tapeNusselt number of a tube fitted with the present typicaltwisted tapes was compared with experimental data of right-left helical twist tape [32] as shown in Figures 12 and 13Apparently the typical twist tape offered an additional heattransfer enhancement with less skin friction factor

6 Journal of Nanomaterials

Axial distance x (m)

Re = 220 experimentalRe = 730 experimentalRe = 1460 experimental

Re = 220 theoreticalRe = 720 theoreticalRe = 1460 theoretical

0

5

10

15

20

25

30

0 05 1 15 2

Loca

l Nus

selt

num

ber (

Nu x

)

Figure 9 Comparison between measured and calculated localNusselt number (Nu

119909) using DI-Water

62 Effect of Nanoparticle Volume Concentration in PlainTube Experiments were performed to study heat transferenhancements in plain tube with laminar flow of deionizedwater and SiO

2and TiO

2nanofluids of 1 and 2 volume

concentration The obtained results of Nusselt number andfriction factor are elaborated in Figures 14 and 15 FromFigure 14 it can be seen that the Nusselt number increasedwith the increase of nanoparticle concentration andReynoldsnumber This means that the presence of nanoparticlesincreases the energy exchange rates in the fluid with penaltyon the wall shear stress due to Brownian motion [33] theincreases of Reynolds number increase random movementsof the fluid and consequently enhance the thermal dispersionof the flow Evidently SiO

2nanofluid with 2 volume

concentration offered highest Nusselt number followed byTiO2and water respectively On other hand Figure 15 shows

slightly augmentation in friction factor value with increasesof nanoparticles concentration This means that the pres-ence of nanoparticles volume fraction increases nanofluidviscosity with wall shear stressThe experimental results wereused to derive the following correlations of Nusselt numberand friction for water (120601 = 0) SiO

2and TiO

2nanofluids

(120601 le 2) The predicted values of these correlations showreasonable agreement with the experimental results as shownin Figures 16 and 17

For SiO2nanofluid

Nu = 06116Pr04Re02795 (1 + 120601)347 (13)

119891 = 63236Reminus0994 (1 + 120601) (14)

Dar

cy fr

ictio

n fa

ctor

(f)

0

005

01

015

02

025

03

035

0 500 1000 1500 2000

Reynolds number (Re)

Experimental dataDarcy friction factor

Figure 10 Friction factor across the test section using DI-water asthe working fluid

For TiO2nanofluid

Nu = 06116Pr04Re02795 (1 + 120601)147 (15)

119891 = 63236Reminus0994 (1 + 120601) (16)

63 Effect of Nanoparticle Volume Concentration with TwistTape Variations ofNusselt number and friction factor versusReynolds number for laminar flow of deionized water SiO

2

and TiO2nanofluids of 1 and 2 volume concentration

in tube fitted with typical twist tape (119910 = 293) areshown in Figures 18 and 19 Evidently Figure 18 shows thatthe combined use of nanofluid with twist tape producesfurther augment in heat transfer coefficient than eithernanofluid or twist tape individually The simultaneous use ofnanofluid with twist tape increases the thermal conductivityand viscosity of working fluid as well as increasing swirlflow pathThus greater fluid mixing and higher heat transfercoefficient are produced Eventually SiO

2nanofluid with 2

volume concentration with typical twist tape offered a higherNusselt number compared with the others As shown inFigure 19 the friction factor decreases with the increase ofReynolds number for water and different volume fractionsof nanoparticles Based on the experimental results thefollowing correlations of Nusselt number and friction factorwere derived The correlations are valid for laminar flow(Re lt 1500) 120601 le 2 volume concentration (120601 = 0 for water)of SiO

2and TiO

2nanofluid and typical twist tape of twist

ratio 119910 = 293 The predicted data were in good agreement

Journal of Nanomaterials 7N

usse

lt nu

mbe

r (ex

perim

enta

l)

Nusselt number (Manglik and Bergles equation)

y = 293

+15

minus15

0

20

40

60

80

100

0 20 40 60 80 100

Figure 11 Comparison of experimental and predicted Nusseltnumber of the plain tube fitted with typical twisted tape

with the experimental data within plusmn6 for Nusselt numberand plusmn8 friction factor as shown in Figures 20 and 21

Nu = 5236Pr04Re02357119910minus00881 (1 + 120601)0124 (17)

119891 = 76789Reminus0686119910minus0375 (1 + 120601)0198 (18)

64 Effect of Twist Tape Configuration The influence of andconic (quadrant parabolic half and triangular) cut twistedtape of twist ratio 119910 = 293 and cut depth 119889

119890= 05 cm

with 2 volume concentration of SiO2nanofluid on Nusselt

number and friction factor are shown in Figures 22 and 23Apparently from Figure 22 conic cut twist exhibits higherNusselt number than the typical twisted tape This can beexplained by the fact that conic cut twist tape generates swirlflow with efficient fluid mixing nearby their alternative cutswhile the typical twist tape causes swirl flow only The resultsalso reveal that the triangular cut twisted tape provides ahigherNusselt number comparedwith the othersThismeansthat the vortices behind the alternative cut edges of triangularcut twist tape give superior efficient fluid mixing resultingin further heat transfer enhancement From Figure 23 it canbe seen that friction factor decreases with the increase ofReynolds number and triangular cut twisted tape (VCT) giveshigher friction factor compared with all the other Reynoldsnumbers This implies that the influence of alternative cutsalong the edge of the triangular cut twisted tape promotesadditional wall shear stress due to flow mixing betweenthe fluids at the twist tape and tube wall In addition theexperimental data of conic cut twisted tapes with water (120601 =

0) and nanofluids (120601 = 2) were used to develop the

Nus

selt

num

ber (

Nu)

Reynolds number (Re)

RLT (y = 293) expTT (y = 293) exp

0

15

30

45

60

75

0 500 1000 1500 2000

Figure 12 Experimental Nusselt number of typical twist tape withRLT inserts

following correlations for Nusselt number and friction factorwith reasonable agreement as shown in Figures 24 and 25

For triangular cut twisted tape

Nu = 5387Pr04Re0229 (1 + 119908

119882)

00383

(1 +119889119890

119882)

minus0185

sdot (1 + 120601)0025

(19)

119891 = 6184Reminus067 (1 + 119908

119882)

0127

(1 +119889119890

119882)

minus0468

sdot (1 + 120601)0137

(20)

For parabolic half cut twisted tape

Nu = 5388Pr04Re0229 (1 + 119908

119882)

00384

(1 +119889119890

119882)

minus0184

sdot (1 + 120601)0025

(21)

119891 = 6876Reminus06771 (1 + 119908

119882)

0137

(1 +119889119890

119882)

minus0197

sdot (1 + 120601)00134

(22)

8 Journal of Nanomaterials

0

05

1

15

2

0 500 1000 1500 2000

Reynolds number (Re)

RLT (y = 293) expTT (y = 293) exp

Fric

tion

fact

or (f

)

Figure 13 Experimental friction factor of typical twist tape withRLT inserts

Nus

selt

num

ber (

Nu)

Reynolds number (Re)

DI water1 TiO2

2 TiO2

1 SiO2

2 SiO2

4

6

8

10

12

0 500 1000 1500 2000

Figure 14 Nusselt number versus Reynolds number for plain tubewith nanofluids

0

01

02

03

04

0 500 1000 1500 2000

Reynolds number (Re)

DI water1 TiO2

2 TiO2

1 SiO2

2 SiO2

Fric

tion

fact

or (f

)

Figure 15 Friction factor versus Reynolds number for plain tubewith nanofluids

0

4

8

12

16

0 4 8 12 16

Nus

selt

num

ber (

expe

rimen

tal)

Nusselt number (predicted)

DI water1 TiO2

2 TiO2

1 SiO2

2 SiO2

+6

minus6

Figure 16 Comparison of experimental and predicted Nusseltnumber for plain tube

Journal of Nanomaterials 9

0

01

02

03

04

0 01 02 03 04

Fric

tion

fact

or (e

xper

imen

tal)

Friction factor (predicted)

DI water1 TiO2

2 TiO2

1 SiO2

2 SiO2

+8

minus8

Figure 17 Comparison of experimental and predicted frictionfactor for plain tube

30

35

40

45

50

55

60

0 500 1000 1500 2000

Nus

selt

num

ber (

Nu)

Reynolds number (Re)

DI water1 TiO2

2 TiO2

1 SiO2

2 SiO2

Figure 18 Nusselt number versus Reynolds number for nanofluidswith typical twist tape (119910 = 293)

0

025

05

075

1

125

15

0 500 1000 1500 2000

Reynolds number (Re)

DI water

Fric

tion

fact

or (f

)

1 TiO2

2 TiO21 SiO2

2 SiO2

Figure 19 Nusselt number versus Reynolds number for nanofluidswith typical twist tape (119910 = 293)

0

20

40

60

80

0 20 40 60 80

Nus

selt

num

ber (

expe

rimen

tal)

Nusselt number (predicted)

DI water1 TiO2 2 TiO2

1 SiO2

2 SiO2

+6

minus6

Figure 20 Comparison of experimental and predicted Nusseltnumber with typical twist tape

10 Journal of Nanomaterials

0

025

05

075

1

125

15

0 025 05 075 1 125 15

Fric

tion

fact

or (e

xper

imen

tal)

Friction factor (predicted)

DI water1 TiO2

2 TiO2

1 SiO2

2 SiO2

+8

+8

Figure 21 Comparison of experimental and predicted frictionfactor with typical twist tape

30

35

40

45

50

55

60

65

0 500 1000 1500 2000

Nus

selt

num

ber (

Nu)

Reynolds number (Re)

QCT (2 SiO2)PCT (2 SiO2)VCT (2 SiO2)

TT (2 SiO2)TT (DI water)

Figure 22 Nusselt number versus Reynolds number for typical andconic cut twist tapes

0

03

06

09

12

15

18

0 500 1000 1500 2000

Reynolds number (Re)

QCT (2 SiO2)PCT (2 SiO2)VCT (2 SiO2)

TT (DI water)TT (DI water)

Fric

tion

fact

or (f

)

Figure 23 Friction factor versus Reynolds number for typical andconic cut twist tapes

0

20

40

60

80

0 20 40 60 80

Nus

selt

num

ber (

expe

rimen

tal)

Nusselt number (predicted)

+8

minus8

QCT (2 SiO2)PCT ( SiO2)VCT (2 SiO2)

TT (2 SiO2)TT (DI water)

Figure 24 Comparison of experimental and predicted Nusseltnumber for typical and conic cut twist tapes

Journal of Nanomaterials 11

0

05

1

15

2

0 05 1 15 2

Fric

tion

fact

or (e

xper

imen

tal)

Friction factor (predicted)

QCT (2 SiO2)PCT (2 SiO2)VCT (2 SiO2)

TT (2 SiO2)TT (DI water)

+10

minus10

Figure 25 Comparison of experimental and predicted frictionfactor for typical and conic cut twist tapes

For quadrant cut twisted tape

Nu = 538Pr04Re0226 (1 + 119908

119882)

00387

(1 +119889119890

119882)

minus0187

sdot (1 + 120601)0027

(23)

119891 = 6913Reminus071 (1 + 119908

119882)

0127

(1 +119889119890

119882)

minus016

sdot (1 + 120601)031

(24)

65 Thermal Performance of Twist Tapes The performanceanalysis of typical and conic cut twisted tape inserts in lami-nar flow of SiO

2nanofluid was accomplished by evaluating

thermal performance factor for constant pumping powercondition Thermal performance factor (120578) at constantspumping power is defined as ratio of the convective heattransfer coefficient of the tube with turbulator or enhancingmethod to that of the plain tube The following thermalperformance factor for laminar proposed by [29] is used forperformance analysis

120578 =(NuNu

119900)

(119891119891119900)01666

(25)

where Nu 119891 Nu119900 and 119891

119900are the Nusselt numbers and

friction factors for a duct configuration with and withoutinserts respectively

2

3

4

5

6

0 500 1000 1500 2000

Reynolds number (Re)

QCT (2 SiO2)PCT (2 SiO2)VCT (2 SiO2) TT (2 SiO2)

TT (DI water)

Ther

mal

per

form

ance

fact

or (120578

)

Figure 26 Variation of the thermal performance factor of typicaland conic cut twist tape

Figure 26 shows the variation of thermal performancefactor with Reynolds number for 2 volume concentrationof SiO

2nanofluid The values of thermal performance factor

at all Reynolds were found to be greater than unity for bothtypical and conic cut twisted tape inserts This indicates thattwist tape inserts are feasible in terms of energy saving in lam-inar flow regime It is evident that the thermal performancefactor triangular cut twist tape at constant Reynolds numberis higher than other twist tapes This is due to the strongerturbulenceswirl flow generated by alternative cuts along theedge twist tape The thermal performance factor was foundto be decreasing with increases in Reynolds number Thisis because of the increase in pressure loss as the Reynoldsnumber increases

The experimental results showed that the thermal perfor-mance factor is around 513ndash416 for VCT 498ndash408 for PCT488ndash405 for QCT and 483ndash401 for TT when used with2 SiO

2nanofluid While the thermal performance factor

to be around 475ndash396 for TT with water Therefore theVCT insert shows better thermal performance when usedwith SiO

2nanofluid than other twist tapesThe experimental

results are used to derive the following correlations of thermalperformance factor using least square method of regressionanalysis These correlations are valid for laminar flow (Re lt

1500) of water and 2 volume concentration SiO2for typical

and conic cut twist tapesThe comparisons between the ther-mal performance factor values obtained from experimentaldata and those predicted from the above correlations are

12 Journal of Nanomaterials

3

4

5

6

3 4 5 6

QCT (2 SiO2)PCT (2 SiO2)VCT (2 SiO2) TT (2 SiO2)

TT (DI water)

+6

minus6

Ther

mal

per

form

ance

fact

or (e

xper

imen

tal)

Thermal performance factor (predicted)

Figure 27 Comparison of experimental and predicted thermalperformance for typical and conic cut twist tapes

shown in Figure 27 As shown the predicted data are in goodagreement with the experimental data

For VCT twisted tape

120578 = 5173Reminus0118 (1 + 119908

119882)

2483

(1 +119889119890

119882)

minus0247

sdot (1 + 120601SiO2

)00183

(26)

For PCT twisted tape

120578 = 5173Re00945 (1 + 119908

119882)

3113

(1 +119889119890

119882)

minus0247

sdot (1 + 120601SiO2

)00183

(27)

For QCT twisted tape

120578 = 5173Re0118 (1 + 119908

119882)

349

(1 +119889119890

119882)

minus0247

sdot (1 + 120601SiO2

)00183

(28)

For TT twisted tape with SiO nanofluid

120578 = 791Re0093 (1 + 120601SiO2

)1283

(29)

For TT twisted tape with deionized water

120578 = 791Re0093 (30)

7 Conclusions

Heat transfer friction and thermal performance characteris-tics of SiO

2and TiO

2nanofluids with two concentrations of

1 and 2 by volume in a circular tube fitted with a typicaland conic cut twist tape in the laminar regime have beenexperimentally investigated The main conclusions from thisexperimental study are as follows

(71) SiO2and TiO

2nanofluids of different volume con-

centration in plain tube give good enhancement inNusselt number compared to deionized water Thehigher enhancement inNusselt number is obtained bySiO2nanofluids with volume concentrations of 2

(72) At similar conditions the insertion of typical twisttape causes very significant convective heat transferenhancement in the laminar flow however furtherenhancement is observed by the simultaneous use ofnanofluid with twisted tape compared to the use oftwisted tape or nanofluid alone

(73) The use of nanofluid with the conic cut twist tapeprovides a considerably higher Nusselt number thanthat of nanofluid with the typical twist tape for allReynolds numbers examinedThe triangular cut twisttape offers higher heat transfer rate than the typicaltwist tape and other conic cut configurations

(74) Over the range investigated (Re = 220ndash1500) themaximum thermal performance factor of 513 isfound with the simultaneous use of the triangulartwist tape with SiO

2nanofluid with 2 volume

concentration at Reynolds number of 220(75) The empirical correlations for the Nusselt number

friction factor and the thermal performance factorfor typical and conic cut twist tapes are developedand fitted with the experimental data of water andnanofluids

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

The authors would like to thank the National Universityof Malaysia and the Ministry of Higher Education for thefinancial support (FRGS12013TK07UKM011 and DPP-2013-114) to perform this investigation

References

[1] A Bejan and A D KrausHeat Transfer Handbook John Wileyamp Sons 2003

[2] I Singh and N Diwakar International Journal of AppliedResearch in Mechanical Engineering vol 3 pp 16ndash29 2013

[3] R M Manglik and A E Bergles ldquoHeat transfer and pressuredrop correlations for twisted-tape inserts in isothermal tubes

Journal of Nanomaterials 13

part Imdashlaminar flowsrdquo Journal of Heat Transfer vol 115 no 4pp 881ndash889 1993

[4] S K Saha and D Chakraborty ldquoHeat transfer and pressuredrop characteristics of laminar flow through a circular tubefitted with regularly spaced twisted tape elements with multipletwistsrdquo in Proceedings of the Heat andMass Transfer Conferencepp 313ndash318 Kanpur India 1997

[5] S Al-Fahed L M Chamra and W Chakroun ldquoPressure dropand heat transfer comparison for both microfin tube andtwisted-tape inserts in laminar flowrdquo ExperimentalThermal andFluid Science vol 18 no 4 pp 323ndash333 1998

[6] M S Lokanath and R D Misal ldquoAn experimental study on theperformance of plate heat exchanger and an augmented shelland tube heat exchanger for different types of fluids for marineapplicationsrdquo in Proceedings of the 5th ISHMT-ASME Heat andMass Transfer Conference pp 863ndash868 TataMcGraw-Hill NewDelhi India 2002

[7] P Sivashanmugam and S Suresh ldquoExperimental studies onheat transfer and friction factor characteristics of laminar flowthrough a circular tube fitted with helical screw-tape insertsrdquoApplied Thermal Engineering vol 26 no 16 pp 1990ndash19972006

[8] P Sivashanmugam and S Suresh ldquoExperimental studies onheat transfer and friction factor characteristics of laminar flowthrough a circular tube fitted with regularly spaced helicalscrew-tape insertsrdquo Experimental Thermal and Fluid Sciencevol 31 no 4 pp 301ndash308 2007

[9] S Jaisankar T K Radhakrishnan and K N Sheeba ldquoStudieson heat transfer and friction factor characteristics of ther-mosyphon solar water heating system with helical twistedtapesrdquo Energy vol 34 no 9 pp 1054ndash1064 2009

[10] A V N Kapatkar B D A S Padalkar and C S KasbeldquoExperimental investigation on heat transfer enhancement inlaminar flow in circular tube equipped with different insertsrdquoAMAE International Journal on Manufacturing and MaterialScience vol 1 pp 1ndash6 2011

[11] J Guo A Fan X Zhang and W Liu ldquoA numerical studyon heat transfer and friction factor characteristics of laminarflow in a circular tube fitted with center-cleared twisted taperdquoInternational Journal ofThermal Sciences vol 50 no 7 pp 1263ndash1270 2011

[12] K Wongcharee and S Eiamsa-ard ldquoFriction and heat trans-fer characteristics of laminar swirl flow through the roundtubes inserted with alternate clockwise and counter-clockwisetwisted-tapesrdquo International Communications in Heat andMassTransfer vol 38 no 3 pp 348ndash352 2011

[13] E Z Ibrahim ldquoAugmentation of laminar flow and heat transferin flat tubes by means of helical screw-tape insertsrdquo EnergyConversion and Management vol 52 no 1 pp 250ndash257 2011

[14] S U S Choi and J A Eastman ldquoEnhancing thermal con-ductivity of fluids with nanoparticlesrdquo in Developments andApplications of Non-Newtonian Flows D A Siguier and HP Wang Eds pp 99ndash105 American Society of MechanicalEngineers New York NY USA 1995

[15] C Y Tsai H T Chien P P Ding B Chan T Y Luh and PH Chen ldquoEffect of structural character of gold nanoparticles innanofluid on heat pipe thermal performancerdquoMaterials Lettersvol 58 no 9 pp 1461ndash1465 2004

[16] M-S Liu M C-C Lin C Y Tsai and C-C Wang ldquoEnhance-ment of thermal conductivity with Cu for nanofluids using

chemical reduction methodrdquo International Journal of Heat andMass Transfer vol 49 no 17-18 pp 3028ndash3033 2006

[17] E Tamjid andBHGuenther ldquoRheology and colloidal structureof silver nanoparticles dispersed in diethylene glycolrdquo PowderTechnology vol 197 no 1-2 pp 49ndash53 2010

[18] SM SMurshed K C Leong and C Yang ldquoEnhanced thermalconductivity of TiO

2water based nanofluidsrdquo International

Journal of Thermal Sciences vol 44 no 4 pp 367ndash373 2005[19] H Zhu C Zhang S Liu Y Tang and Y Yin ldquoEffects of

nanoparticle clustering and alignment on thermal conductiv-ities of Fe

3O4aqueous nanofluidsrdquo Applied Physics Letters vol

89 Article ID 023123 2006[20] J A Eastman U S Choi S Li L J Thompson and S Lee

ldquoEnhanced thermal conductivity through the development ofnanofluidsrdquoMRS Proceedings vol 457 1996

[21] M EMeibodi M Vafaie-Sefti AM Rashidi A Amrollahi MTabasi and H S Kalal ldquoSimple model for thermal conductivityof nanofluids using resistance model approachrdquo InternationalCommunications in Heat and Mass Transfer vol 37 no 5 pp555ndash559 2010

[22] G Pathipakka and P Sivashanmugam ldquoHeat transfer behaviourof nanofluids in a uniformly heated circular tube fittedwith heli-cal inserts in laminar flowrdquo Superlattices and Microstructuresvol 47 no 2 pp 349ndash360 2010

[23] K Wongcharee and S Eiamsa-ard ldquoEnhancement of heattransfer using CuOwater nanofluid and twisted tape withalternate axisrdquo International Communications in Heat and MassTransfer vol 38 no 6 pp 742ndash748 2011

[24] S Suresh K P Venkitaraj and P Selvakumar ldquoComparativestudy on thermal performance of helical screw tape inserts inlaminar flow using Al

2O3water and CuOwater nanofluidsrdquo

Superlattices and Microstructures vol 49 no 6 pp 608ndash6222011

[25] S D Salman A A H Kadhum M S Takriff and A BMohamad ldquoHeat transfer enhancement of laminar nanofluidsflow in a circular tube fitted with parabolic-cut twisted tapeinsertsrdquo The Scientific World Journal vol 2014 Article ID543231 7 pages 2014

[26] S D Salman A A H Kadhum M S Takriff and A BMohamad ldquoCFD simulation of heat transfer and friction factoraugmentation in a circular tube fitted with elliptic-cut twistedtape insertsrdquo Mathematical Problems in Engineering vol 2013Article ID 163839 7 pages 2013

[27] S D Salman A A H Kadhum M S Takriff and A BMohamad ldquoCFD analysis of Heat transfer and friction factorcharacteristics in a circular tube fitted with Quadrant-cuttwisted tape insertsrdquoMathematical Problems in Engineering vol2013 Article ID 273764 8 pages 2013

[28] F P Incropera D P Dewitt T L Bergman and A S LavineFundamentals of Heat and Mass Transfer John Wiley amp Sons2007

[29] H Usui Y Sano K Iwashita and A Isozaki ldquoEnhancement ofheat transfer by a combination of internally grooved rough tubeand twisted taperdquo International Chemical Engineering vol 26no 1 pp 97ndash104 1986

[30] J P Holman Experimental Methods for Engineers McGraw-Hill New York NY USA 2011

[31] R K Shah and A L London Laminar Flow Forced Convectionin Ducts Academic Press New York NY USA 1978

14 Journal of Nanomaterials

[32] P KNagarajan andP Sivashanmugam ldquoCFD simulation of heattransfer augmentation in a circular tube fitted with right-lefthelical inserts with spacerrdquo International Journal of ChemicalEngineering Research vol 1 pp 1ndash11 2009

[33] P Keblinski S R Phillpot S U S Choi and J A EastmanldquoMechanisms of heat flow in suspensions of nano-sized particles(nanofluids)rdquo International Journal of Heat and Mass Transfervol 45 no 4 pp 855ndash863 2002

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

Journal of Nanomaterials 5

Air chiller

NotebookData logger

Flow

met

er

Set of thermocouples

PumpCold water tank

Valve

Valve

Test section

Pressure transmitter

Calming section

Power supply

Volt meter amp meter and power meter

Figure 7 Schematic diagram of the experimental setup

Figure 8 Test section with thermocouple locations

where Nu and 119891 are respectively the Nusselt number andfriction factor of the tube with enhancing factor (nanofluidandor twisted tape) while Nu

119900and 119891

119900are respectively the

Nusselt number and friction factor of the plain tubeA standard uncertainty analysis was conducted for each

measurement using Kline-McClintock method [30] Themaximum uncertainties for Reynolds number Nusselt num-ber and friction factor were calculated to be 61 848 and24 respectively

6 Results and Discussions

61 Experimental Setup Validation To evaluate the reliabilityof the present experimental setup the experimental results

of pure water in plain tube without twisted tape underlaminar flow conditions were validated with shah equation[31] and Hagen-Poiseuille equation [28] The results showedreasonable agreement with the local Nusselt number (Nu

119909)

and friction factor (119891) as shown in Figures 9 and 10

Nu119909= 1953119909

minus13

lowastfor 119909lowastle 003

Nu119909= 4364 +

00722

119909lowast

for 119909lowastgt 003

(11)

119891 =64

Re (12)

The results of Nusselt number for plain tube with typicaltwisted tape (119910 = 293) were also validated with Manglik andBergle equation [3] As shown in Figure 11 the data obtainedwere found to be in good agreement with the availablecorrelation For the proof of the present typical twisted tapeNusselt number of a tube fitted with the present typicaltwisted tapes was compared with experimental data of right-left helical twist tape [32] as shown in Figures 12 and 13Apparently the typical twist tape offered an additional heattransfer enhancement with less skin friction factor

6 Journal of Nanomaterials

Axial distance x (m)

Re = 220 experimentalRe = 730 experimentalRe = 1460 experimental

Re = 220 theoreticalRe = 720 theoreticalRe = 1460 theoretical

0

5

10

15

20

25

30

0 05 1 15 2

Loca

l Nus

selt

num

ber (

Nu x

)

Figure 9 Comparison between measured and calculated localNusselt number (Nu

119909) using DI-Water

62 Effect of Nanoparticle Volume Concentration in PlainTube Experiments were performed to study heat transferenhancements in plain tube with laminar flow of deionizedwater and SiO

2and TiO

2nanofluids of 1 and 2 volume

concentration The obtained results of Nusselt number andfriction factor are elaborated in Figures 14 and 15 FromFigure 14 it can be seen that the Nusselt number increasedwith the increase of nanoparticle concentration andReynoldsnumber This means that the presence of nanoparticlesincreases the energy exchange rates in the fluid with penaltyon the wall shear stress due to Brownian motion [33] theincreases of Reynolds number increase random movementsof the fluid and consequently enhance the thermal dispersionof the flow Evidently SiO

2nanofluid with 2 volume

concentration offered highest Nusselt number followed byTiO2and water respectively On other hand Figure 15 shows

slightly augmentation in friction factor value with increasesof nanoparticles concentration This means that the pres-ence of nanoparticles volume fraction increases nanofluidviscosity with wall shear stressThe experimental results wereused to derive the following correlations of Nusselt numberand friction for water (120601 = 0) SiO

2and TiO

2nanofluids

(120601 le 2) The predicted values of these correlations showreasonable agreement with the experimental results as shownin Figures 16 and 17

For SiO2nanofluid

Nu = 06116Pr04Re02795 (1 + 120601)347 (13)

119891 = 63236Reminus0994 (1 + 120601) (14)

Dar

cy fr

ictio

n fa

ctor

(f)

0

005

01

015

02

025

03

035

0 500 1000 1500 2000

Reynolds number (Re)

Experimental dataDarcy friction factor

Figure 10 Friction factor across the test section using DI-water asthe working fluid

For TiO2nanofluid

Nu = 06116Pr04Re02795 (1 + 120601)147 (15)

119891 = 63236Reminus0994 (1 + 120601) (16)

63 Effect of Nanoparticle Volume Concentration with TwistTape Variations ofNusselt number and friction factor versusReynolds number for laminar flow of deionized water SiO

2

and TiO2nanofluids of 1 and 2 volume concentration

in tube fitted with typical twist tape (119910 = 293) areshown in Figures 18 and 19 Evidently Figure 18 shows thatthe combined use of nanofluid with twist tape producesfurther augment in heat transfer coefficient than eithernanofluid or twist tape individually The simultaneous use ofnanofluid with twist tape increases the thermal conductivityand viscosity of working fluid as well as increasing swirlflow pathThus greater fluid mixing and higher heat transfercoefficient are produced Eventually SiO

2nanofluid with 2

volume concentration with typical twist tape offered a higherNusselt number compared with the others As shown inFigure 19 the friction factor decreases with the increase ofReynolds number for water and different volume fractionsof nanoparticles Based on the experimental results thefollowing correlations of Nusselt number and friction factorwere derived The correlations are valid for laminar flow(Re lt 1500) 120601 le 2 volume concentration (120601 = 0 for water)of SiO

2and TiO

2nanofluid and typical twist tape of twist

ratio 119910 = 293 The predicted data were in good agreement

Journal of Nanomaterials 7N

usse

lt nu

mbe

r (ex

perim

enta

l)

Nusselt number (Manglik and Bergles equation)

y = 293

+15

minus15

0

20

40

60

80

100

0 20 40 60 80 100

Figure 11 Comparison of experimental and predicted Nusseltnumber of the plain tube fitted with typical twisted tape

with the experimental data within plusmn6 for Nusselt numberand plusmn8 friction factor as shown in Figures 20 and 21

Nu = 5236Pr04Re02357119910minus00881 (1 + 120601)0124 (17)

119891 = 76789Reminus0686119910minus0375 (1 + 120601)0198 (18)

64 Effect of Twist Tape Configuration The influence of andconic (quadrant parabolic half and triangular) cut twistedtape of twist ratio 119910 = 293 and cut depth 119889

119890= 05 cm

with 2 volume concentration of SiO2nanofluid on Nusselt

number and friction factor are shown in Figures 22 and 23Apparently from Figure 22 conic cut twist exhibits higherNusselt number than the typical twisted tape This can beexplained by the fact that conic cut twist tape generates swirlflow with efficient fluid mixing nearby their alternative cutswhile the typical twist tape causes swirl flow only The resultsalso reveal that the triangular cut twisted tape provides ahigherNusselt number comparedwith the othersThismeansthat the vortices behind the alternative cut edges of triangularcut twist tape give superior efficient fluid mixing resultingin further heat transfer enhancement From Figure 23 it canbe seen that friction factor decreases with the increase ofReynolds number and triangular cut twisted tape (VCT) giveshigher friction factor compared with all the other Reynoldsnumbers This implies that the influence of alternative cutsalong the edge of the triangular cut twisted tape promotesadditional wall shear stress due to flow mixing betweenthe fluids at the twist tape and tube wall In addition theexperimental data of conic cut twisted tapes with water (120601 =

0) and nanofluids (120601 = 2) were used to develop the

Nus

selt

num

ber (

Nu)

Reynolds number (Re)

RLT (y = 293) expTT (y = 293) exp

0

15

30

45

60

75

0 500 1000 1500 2000

Figure 12 Experimental Nusselt number of typical twist tape withRLT inserts

following correlations for Nusselt number and friction factorwith reasonable agreement as shown in Figures 24 and 25

For triangular cut twisted tape

Nu = 5387Pr04Re0229 (1 + 119908

119882)

00383

(1 +119889119890

119882)

minus0185

sdot (1 + 120601)0025

(19)

119891 = 6184Reminus067 (1 + 119908

119882)

0127

(1 +119889119890

119882)

minus0468

sdot (1 + 120601)0137

(20)

For parabolic half cut twisted tape

Nu = 5388Pr04Re0229 (1 + 119908

119882)

00384

(1 +119889119890

119882)

minus0184

sdot (1 + 120601)0025

(21)

119891 = 6876Reminus06771 (1 + 119908

119882)

0137

(1 +119889119890

119882)

minus0197

sdot (1 + 120601)00134

(22)

8 Journal of Nanomaterials

0

05

1

15

2

0 500 1000 1500 2000

Reynolds number (Re)

RLT (y = 293) expTT (y = 293) exp

Fric

tion

fact

or (f

)

Figure 13 Experimental friction factor of typical twist tape withRLT inserts

Nus

selt

num

ber (

Nu)

Reynolds number (Re)

DI water1 TiO2

2 TiO2

1 SiO2

2 SiO2

4

6

8

10

12

0 500 1000 1500 2000

Figure 14 Nusselt number versus Reynolds number for plain tubewith nanofluids

0

01

02

03

04

0 500 1000 1500 2000

Reynolds number (Re)

DI water1 TiO2

2 TiO2

1 SiO2

2 SiO2

Fric

tion

fact

or (f

)

Figure 15 Friction factor versus Reynolds number for plain tubewith nanofluids

0

4

8

12

16

0 4 8 12 16

Nus

selt

num

ber (

expe

rimen

tal)

Nusselt number (predicted)

DI water1 TiO2

2 TiO2

1 SiO2

2 SiO2

+6

minus6

Figure 16 Comparison of experimental and predicted Nusseltnumber for plain tube

Journal of Nanomaterials 9

0

01

02

03

04

0 01 02 03 04

Fric

tion

fact

or (e

xper

imen

tal)

Friction factor (predicted)

DI water1 TiO2

2 TiO2

1 SiO2

2 SiO2

+8

minus8

Figure 17 Comparison of experimental and predicted frictionfactor for plain tube

30

35

40

45

50

55

60

0 500 1000 1500 2000

Nus

selt

num

ber (

Nu)

Reynolds number (Re)

DI water1 TiO2

2 TiO2

1 SiO2

2 SiO2

Figure 18 Nusselt number versus Reynolds number for nanofluidswith typical twist tape (119910 = 293)

0

025

05

075

1

125

15

0 500 1000 1500 2000

Reynolds number (Re)

DI water

Fric

tion

fact

or (f

)

1 TiO2

2 TiO21 SiO2

2 SiO2

Figure 19 Nusselt number versus Reynolds number for nanofluidswith typical twist tape (119910 = 293)

0

20

40

60

80

0 20 40 60 80

Nus

selt

num

ber (

expe

rimen

tal)

Nusselt number (predicted)

DI water1 TiO2 2 TiO2

1 SiO2

2 SiO2

+6

minus6

Figure 20 Comparison of experimental and predicted Nusseltnumber with typical twist tape

10 Journal of Nanomaterials

0

025

05

075

1

125

15

0 025 05 075 1 125 15

Fric

tion

fact

or (e

xper

imen

tal)

Friction factor (predicted)

DI water1 TiO2

2 TiO2

1 SiO2

2 SiO2

+8

+8

Figure 21 Comparison of experimental and predicted frictionfactor with typical twist tape

30

35

40

45

50

55

60

65

0 500 1000 1500 2000

Nus

selt

num

ber (

Nu)

Reynolds number (Re)

QCT (2 SiO2)PCT (2 SiO2)VCT (2 SiO2)

TT (2 SiO2)TT (DI water)

Figure 22 Nusselt number versus Reynolds number for typical andconic cut twist tapes

0

03

06

09

12

15

18

0 500 1000 1500 2000

Reynolds number (Re)

QCT (2 SiO2)PCT (2 SiO2)VCT (2 SiO2)

TT (DI water)TT (DI water)

Fric

tion

fact

or (f

)

Figure 23 Friction factor versus Reynolds number for typical andconic cut twist tapes

0

20

40

60

80

0 20 40 60 80

Nus

selt

num

ber (

expe

rimen

tal)

Nusselt number (predicted)

+8

minus8

QCT (2 SiO2)PCT ( SiO2)VCT (2 SiO2)

TT (2 SiO2)TT (DI water)

Figure 24 Comparison of experimental and predicted Nusseltnumber for typical and conic cut twist tapes

Journal of Nanomaterials 11

0

05

1

15

2

0 05 1 15 2

Fric

tion

fact

or (e

xper

imen

tal)

Friction factor (predicted)

QCT (2 SiO2)PCT (2 SiO2)VCT (2 SiO2)

TT (2 SiO2)TT (DI water)

+10

minus10

Figure 25 Comparison of experimental and predicted frictionfactor for typical and conic cut twist tapes

For quadrant cut twisted tape

Nu = 538Pr04Re0226 (1 + 119908

119882)

00387

(1 +119889119890

119882)

minus0187

sdot (1 + 120601)0027

(23)

119891 = 6913Reminus071 (1 + 119908

119882)

0127

(1 +119889119890

119882)

minus016

sdot (1 + 120601)031

(24)

65 Thermal Performance of Twist Tapes The performanceanalysis of typical and conic cut twisted tape inserts in lami-nar flow of SiO

2nanofluid was accomplished by evaluating

thermal performance factor for constant pumping powercondition Thermal performance factor (120578) at constantspumping power is defined as ratio of the convective heattransfer coefficient of the tube with turbulator or enhancingmethod to that of the plain tube The following thermalperformance factor for laminar proposed by [29] is used forperformance analysis

120578 =(NuNu

119900)

(119891119891119900)01666

(25)

where Nu 119891 Nu119900 and 119891

119900are the Nusselt numbers and

friction factors for a duct configuration with and withoutinserts respectively

2

3

4

5

6

0 500 1000 1500 2000

Reynolds number (Re)

QCT (2 SiO2)PCT (2 SiO2)VCT (2 SiO2) TT (2 SiO2)

TT (DI water)

Ther

mal

per

form

ance

fact

or (120578

)

Figure 26 Variation of the thermal performance factor of typicaland conic cut twist tape

Figure 26 shows the variation of thermal performancefactor with Reynolds number for 2 volume concentrationof SiO

2nanofluid The values of thermal performance factor

at all Reynolds were found to be greater than unity for bothtypical and conic cut twisted tape inserts This indicates thattwist tape inserts are feasible in terms of energy saving in lam-inar flow regime It is evident that the thermal performancefactor triangular cut twist tape at constant Reynolds numberis higher than other twist tapes This is due to the strongerturbulenceswirl flow generated by alternative cuts along theedge twist tape The thermal performance factor was foundto be decreasing with increases in Reynolds number Thisis because of the increase in pressure loss as the Reynoldsnumber increases

The experimental results showed that the thermal perfor-mance factor is around 513ndash416 for VCT 498ndash408 for PCT488ndash405 for QCT and 483ndash401 for TT when used with2 SiO

2nanofluid While the thermal performance factor

to be around 475ndash396 for TT with water Therefore theVCT insert shows better thermal performance when usedwith SiO

2nanofluid than other twist tapesThe experimental

results are used to derive the following correlations of thermalperformance factor using least square method of regressionanalysis These correlations are valid for laminar flow (Re lt

1500) of water and 2 volume concentration SiO2for typical

and conic cut twist tapesThe comparisons between the ther-mal performance factor values obtained from experimentaldata and those predicted from the above correlations are

12 Journal of Nanomaterials

3

4

5

6

3 4 5 6

QCT (2 SiO2)PCT (2 SiO2)VCT (2 SiO2) TT (2 SiO2)

TT (DI water)

+6

minus6

Ther

mal

per

form

ance

fact

or (e

xper

imen

tal)

Thermal performance factor (predicted)

Figure 27 Comparison of experimental and predicted thermalperformance for typical and conic cut twist tapes

shown in Figure 27 As shown the predicted data are in goodagreement with the experimental data

For VCT twisted tape

120578 = 5173Reminus0118 (1 + 119908

119882)

2483

(1 +119889119890

119882)

minus0247

sdot (1 + 120601SiO2

)00183

(26)

For PCT twisted tape

120578 = 5173Re00945 (1 + 119908

119882)

3113

(1 +119889119890

119882)

minus0247

sdot (1 + 120601SiO2

)00183

(27)

For QCT twisted tape

120578 = 5173Re0118 (1 + 119908

119882)

349

(1 +119889119890

119882)

minus0247

sdot (1 + 120601SiO2

)00183

(28)

For TT twisted tape with SiO nanofluid

120578 = 791Re0093 (1 + 120601SiO2

)1283

(29)

For TT twisted tape with deionized water

120578 = 791Re0093 (30)

7 Conclusions

Heat transfer friction and thermal performance characteris-tics of SiO

2and TiO

2nanofluids with two concentrations of

1 and 2 by volume in a circular tube fitted with a typicaland conic cut twist tape in the laminar regime have beenexperimentally investigated The main conclusions from thisexperimental study are as follows

(71) SiO2and TiO

2nanofluids of different volume con-

centration in plain tube give good enhancement inNusselt number compared to deionized water Thehigher enhancement inNusselt number is obtained bySiO2nanofluids with volume concentrations of 2

(72) At similar conditions the insertion of typical twisttape causes very significant convective heat transferenhancement in the laminar flow however furtherenhancement is observed by the simultaneous use ofnanofluid with twisted tape compared to the use oftwisted tape or nanofluid alone

(73) The use of nanofluid with the conic cut twist tapeprovides a considerably higher Nusselt number thanthat of nanofluid with the typical twist tape for allReynolds numbers examinedThe triangular cut twisttape offers higher heat transfer rate than the typicaltwist tape and other conic cut configurations

(74) Over the range investigated (Re = 220ndash1500) themaximum thermal performance factor of 513 isfound with the simultaneous use of the triangulartwist tape with SiO

2nanofluid with 2 volume

concentration at Reynolds number of 220(75) The empirical correlations for the Nusselt number

friction factor and the thermal performance factorfor typical and conic cut twist tapes are developedand fitted with the experimental data of water andnanofluids

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

The authors would like to thank the National Universityof Malaysia and the Ministry of Higher Education for thefinancial support (FRGS12013TK07UKM011 and DPP-2013-114) to perform this investigation

References

[1] A Bejan and A D KrausHeat Transfer Handbook John Wileyamp Sons 2003

[2] I Singh and N Diwakar International Journal of AppliedResearch in Mechanical Engineering vol 3 pp 16ndash29 2013

[3] R M Manglik and A E Bergles ldquoHeat transfer and pressuredrop correlations for twisted-tape inserts in isothermal tubes

Journal of Nanomaterials 13

part Imdashlaminar flowsrdquo Journal of Heat Transfer vol 115 no 4pp 881ndash889 1993

[4] S K Saha and D Chakraborty ldquoHeat transfer and pressuredrop characteristics of laminar flow through a circular tubefitted with regularly spaced twisted tape elements with multipletwistsrdquo in Proceedings of the Heat andMass Transfer Conferencepp 313ndash318 Kanpur India 1997

[5] S Al-Fahed L M Chamra and W Chakroun ldquoPressure dropand heat transfer comparison for both microfin tube andtwisted-tape inserts in laminar flowrdquo ExperimentalThermal andFluid Science vol 18 no 4 pp 323ndash333 1998

[6] M S Lokanath and R D Misal ldquoAn experimental study on theperformance of plate heat exchanger and an augmented shelland tube heat exchanger for different types of fluids for marineapplicationsrdquo in Proceedings of the 5th ISHMT-ASME Heat andMass Transfer Conference pp 863ndash868 TataMcGraw-Hill NewDelhi India 2002

[7] P Sivashanmugam and S Suresh ldquoExperimental studies onheat transfer and friction factor characteristics of laminar flowthrough a circular tube fitted with helical screw-tape insertsrdquoApplied Thermal Engineering vol 26 no 16 pp 1990ndash19972006

[8] P Sivashanmugam and S Suresh ldquoExperimental studies onheat transfer and friction factor characteristics of laminar flowthrough a circular tube fitted with regularly spaced helicalscrew-tape insertsrdquo Experimental Thermal and Fluid Sciencevol 31 no 4 pp 301ndash308 2007

[9] S Jaisankar T K Radhakrishnan and K N Sheeba ldquoStudieson heat transfer and friction factor characteristics of ther-mosyphon solar water heating system with helical twistedtapesrdquo Energy vol 34 no 9 pp 1054ndash1064 2009

[10] A V N Kapatkar B D A S Padalkar and C S KasbeldquoExperimental investigation on heat transfer enhancement inlaminar flow in circular tube equipped with different insertsrdquoAMAE International Journal on Manufacturing and MaterialScience vol 1 pp 1ndash6 2011

[11] J Guo A Fan X Zhang and W Liu ldquoA numerical studyon heat transfer and friction factor characteristics of laminarflow in a circular tube fitted with center-cleared twisted taperdquoInternational Journal ofThermal Sciences vol 50 no 7 pp 1263ndash1270 2011

[12] K Wongcharee and S Eiamsa-ard ldquoFriction and heat trans-fer characteristics of laminar swirl flow through the roundtubes inserted with alternate clockwise and counter-clockwisetwisted-tapesrdquo International Communications in Heat andMassTransfer vol 38 no 3 pp 348ndash352 2011

[13] E Z Ibrahim ldquoAugmentation of laminar flow and heat transferin flat tubes by means of helical screw-tape insertsrdquo EnergyConversion and Management vol 52 no 1 pp 250ndash257 2011

[14] S U S Choi and J A Eastman ldquoEnhancing thermal con-ductivity of fluids with nanoparticlesrdquo in Developments andApplications of Non-Newtonian Flows D A Siguier and HP Wang Eds pp 99ndash105 American Society of MechanicalEngineers New York NY USA 1995

[15] C Y Tsai H T Chien P P Ding B Chan T Y Luh and PH Chen ldquoEffect of structural character of gold nanoparticles innanofluid on heat pipe thermal performancerdquoMaterials Lettersvol 58 no 9 pp 1461ndash1465 2004

[16] M-S Liu M C-C Lin C Y Tsai and C-C Wang ldquoEnhance-ment of thermal conductivity with Cu for nanofluids using

chemical reduction methodrdquo International Journal of Heat andMass Transfer vol 49 no 17-18 pp 3028ndash3033 2006

[17] E Tamjid andBHGuenther ldquoRheology and colloidal structureof silver nanoparticles dispersed in diethylene glycolrdquo PowderTechnology vol 197 no 1-2 pp 49ndash53 2010

[18] SM SMurshed K C Leong and C Yang ldquoEnhanced thermalconductivity of TiO

2water based nanofluidsrdquo International

Journal of Thermal Sciences vol 44 no 4 pp 367ndash373 2005[19] H Zhu C Zhang S Liu Y Tang and Y Yin ldquoEffects of

nanoparticle clustering and alignment on thermal conductiv-ities of Fe

3O4aqueous nanofluidsrdquo Applied Physics Letters vol

89 Article ID 023123 2006[20] J A Eastman U S Choi S Li L J Thompson and S Lee

ldquoEnhanced thermal conductivity through the development ofnanofluidsrdquoMRS Proceedings vol 457 1996

[21] M EMeibodi M Vafaie-Sefti AM Rashidi A Amrollahi MTabasi and H S Kalal ldquoSimple model for thermal conductivityof nanofluids using resistance model approachrdquo InternationalCommunications in Heat and Mass Transfer vol 37 no 5 pp555ndash559 2010

[22] G Pathipakka and P Sivashanmugam ldquoHeat transfer behaviourof nanofluids in a uniformly heated circular tube fittedwith heli-cal inserts in laminar flowrdquo Superlattices and Microstructuresvol 47 no 2 pp 349ndash360 2010

[23] K Wongcharee and S Eiamsa-ard ldquoEnhancement of heattransfer using CuOwater nanofluid and twisted tape withalternate axisrdquo International Communications in Heat and MassTransfer vol 38 no 6 pp 742ndash748 2011

[24] S Suresh K P Venkitaraj and P Selvakumar ldquoComparativestudy on thermal performance of helical screw tape inserts inlaminar flow using Al

2O3water and CuOwater nanofluidsrdquo

Superlattices and Microstructures vol 49 no 6 pp 608ndash6222011

[25] S D Salman A A H Kadhum M S Takriff and A BMohamad ldquoHeat transfer enhancement of laminar nanofluidsflow in a circular tube fitted with parabolic-cut twisted tapeinsertsrdquo The Scientific World Journal vol 2014 Article ID543231 7 pages 2014

[26] S D Salman A A H Kadhum M S Takriff and A BMohamad ldquoCFD simulation of heat transfer and friction factoraugmentation in a circular tube fitted with elliptic-cut twistedtape insertsrdquo Mathematical Problems in Engineering vol 2013Article ID 163839 7 pages 2013

[27] S D Salman A A H Kadhum M S Takriff and A BMohamad ldquoCFD analysis of Heat transfer and friction factorcharacteristics in a circular tube fitted with Quadrant-cuttwisted tape insertsrdquoMathematical Problems in Engineering vol2013 Article ID 273764 8 pages 2013

[28] F P Incropera D P Dewitt T L Bergman and A S LavineFundamentals of Heat and Mass Transfer John Wiley amp Sons2007

[29] H Usui Y Sano K Iwashita and A Isozaki ldquoEnhancement ofheat transfer by a combination of internally grooved rough tubeand twisted taperdquo International Chemical Engineering vol 26no 1 pp 97ndash104 1986

[30] J P Holman Experimental Methods for Engineers McGraw-Hill New York NY USA 2011

[31] R K Shah and A L London Laminar Flow Forced Convectionin Ducts Academic Press New York NY USA 1978

14 Journal of Nanomaterials

[32] P KNagarajan andP Sivashanmugam ldquoCFD simulation of heattransfer augmentation in a circular tube fitted with right-lefthelical inserts with spacerrdquo International Journal of ChemicalEngineering Research vol 1 pp 1ndash11 2009

[33] P Keblinski S R Phillpot S U S Choi and J A EastmanldquoMechanisms of heat flow in suspensions of nano-sized particles(nanofluids)rdquo International Journal of Heat and Mass Transfervol 45 no 4 pp 855ndash863 2002

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

6 Journal of Nanomaterials

Axial distance x (m)

Re = 220 experimentalRe = 730 experimentalRe = 1460 experimental

Re = 220 theoreticalRe = 720 theoreticalRe = 1460 theoretical

0

5

10

15

20

25

30

0 05 1 15 2

Loca

l Nus

selt

num

ber (

Nu x

)

Figure 9 Comparison between measured and calculated localNusselt number (Nu

119909) using DI-Water

62 Effect of Nanoparticle Volume Concentration in PlainTube Experiments were performed to study heat transferenhancements in plain tube with laminar flow of deionizedwater and SiO

2and TiO

2nanofluids of 1 and 2 volume

concentration The obtained results of Nusselt number andfriction factor are elaborated in Figures 14 and 15 FromFigure 14 it can be seen that the Nusselt number increasedwith the increase of nanoparticle concentration andReynoldsnumber This means that the presence of nanoparticlesincreases the energy exchange rates in the fluid with penaltyon the wall shear stress due to Brownian motion [33] theincreases of Reynolds number increase random movementsof the fluid and consequently enhance the thermal dispersionof the flow Evidently SiO

2nanofluid with 2 volume

concentration offered highest Nusselt number followed byTiO2and water respectively On other hand Figure 15 shows

slightly augmentation in friction factor value with increasesof nanoparticles concentration This means that the pres-ence of nanoparticles volume fraction increases nanofluidviscosity with wall shear stressThe experimental results wereused to derive the following correlations of Nusselt numberand friction for water (120601 = 0) SiO

2and TiO

2nanofluids

(120601 le 2) The predicted values of these correlations showreasonable agreement with the experimental results as shownin Figures 16 and 17

For SiO2nanofluid

Nu = 06116Pr04Re02795 (1 + 120601)347 (13)

119891 = 63236Reminus0994 (1 + 120601) (14)

Dar

cy fr

ictio

n fa

ctor

(f)

0

005

01

015

02

025

03

035

0 500 1000 1500 2000

Reynolds number (Re)

Experimental dataDarcy friction factor

Figure 10 Friction factor across the test section using DI-water asthe working fluid

For TiO2nanofluid

Nu = 06116Pr04Re02795 (1 + 120601)147 (15)

119891 = 63236Reminus0994 (1 + 120601) (16)

63 Effect of Nanoparticle Volume Concentration with TwistTape Variations ofNusselt number and friction factor versusReynolds number for laminar flow of deionized water SiO

2

and TiO2nanofluids of 1 and 2 volume concentration

in tube fitted with typical twist tape (119910 = 293) areshown in Figures 18 and 19 Evidently Figure 18 shows thatthe combined use of nanofluid with twist tape producesfurther augment in heat transfer coefficient than eithernanofluid or twist tape individually The simultaneous use ofnanofluid with twist tape increases the thermal conductivityand viscosity of working fluid as well as increasing swirlflow pathThus greater fluid mixing and higher heat transfercoefficient are produced Eventually SiO

2nanofluid with 2

volume concentration with typical twist tape offered a higherNusselt number compared with the others As shown inFigure 19 the friction factor decreases with the increase ofReynolds number for water and different volume fractionsof nanoparticles Based on the experimental results thefollowing correlations of Nusselt number and friction factorwere derived The correlations are valid for laminar flow(Re lt 1500) 120601 le 2 volume concentration (120601 = 0 for water)of SiO

2and TiO

2nanofluid and typical twist tape of twist

ratio 119910 = 293 The predicted data were in good agreement

Journal of Nanomaterials 7N

usse

lt nu

mbe

r (ex

perim

enta

l)

Nusselt number (Manglik and Bergles equation)

y = 293

+15

minus15

0

20

40

60

80

100

0 20 40 60 80 100

Figure 11 Comparison of experimental and predicted Nusseltnumber of the plain tube fitted with typical twisted tape

with the experimental data within plusmn6 for Nusselt numberand plusmn8 friction factor as shown in Figures 20 and 21

Nu = 5236Pr04Re02357119910minus00881 (1 + 120601)0124 (17)

119891 = 76789Reminus0686119910minus0375 (1 + 120601)0198 (18)

64 Effect of Twist Tape Configuration The influence of andconic (quadrant parabolic half and triangular) cut twistedtape of twist ratio 119910 = 293 and cut depth 119889

119890= 05 cm

with 2 volume concentration of SiO2nanofluid on Nusselt

number and friction factor are shown in Figures 22 and 23Apparently from Figure 22 conic cut twist exhibits higherNusselt number than the typical twisted tape This can beexplained by the fact that conic cut twist tape generates swirlflow with efficient fluid mixing nearby their alternative cutswhile the typical twist tape causes swirl flow only The resultsalso reveal that the triangular cut twisted tape provides ahigherNusselt number comparedwith the othersThismeansthat the vortices behind the alternative cut edges of triangularcut twist tape give superior efficient fluid mixing resultingin further heat transfer enhancement From Figure 23 it canbe seen that friction factor decreases with the increase ofReynolds number and triangular cut twisted tape (VCT) giveshigher friction factor compared with all the other Reynoldsnumbers This implies that the influence of alternative cutsalong the edge of the triangular cut twisted tape promotesadditional wall shear stress due to flow mixing betweenthe fluids at the twist tape and tube wall In addition theexperimental data of conic cut twisted tapes with water (120601 =

0) and nanofluids (120601 = 2) were used to develop the

Nus

selt

num

ber (

Nu)

Reynolds number (Re)

RLT (y = 293) expTT (y = 293) exp

0

15

30

45

60

75

0 500 1000 1500 2000

Figure 12 Experimental Nusselt number of typical twist tape withRLT inserts

following correlations for Nusselt number and friction factorwith reasonable agreement as shown in Figures 24 and 25

For triangular cut twisted tape

Nu = 5387Pr04Re0229 (1 + 119908

119882)

00383

(1 +119889119890

119882)

minus0185

sdot (1 + 120601)0025

(19)

119891 = 6184Reminus067 (1 + 119908

119882)

0127

(1 +119889119890

119882)

minus0468

sdot (1 + 120601)0137

(20)

For parabolic half cut twisted tape

Nu = 5388Pr04Re0229 (1 + 119908

119882)

00384

(1 +119889119890

119882)

minus0184

sdot (1 + 120601)0025

(21)

119891 = 6876Reminus06771 (1 + 119908

119882)

0137

(1 +119889119890

119882)

minus0197

sdot (1 + 120601)00134

(22)

8 Journal of Nanomaterials

0

05

1

15

2

0 500 1000 1500 2000

Reynolds number (Re)

RLT (y = 293) expTT (y = 293) exp

Fric

tion

fact

or (f

)

Figure 13 Experimental friction factor of typical twist tape withRLT inserts

Nus

selt

num

ber (

Nu)

Reynolds number (Re)

DI water1 TiO2

2 TiO2

1 SiO2

2 SiO2

4

6

8

10

12

0 500 1000 1500 2000

Figure 14 Nusselt number versus Reynolds number for plain tubewith nanofluids

0

01

02

03

04

0 500 1000 1500 2000

Reynolds number (Re)

DI water1 TiO2

2 TiO2

1 SiO2

2 SiO2

Fric

tion

fact

or (f

)

Figure 15 Friction factor versus Reynolds number for plain tubewith nanofluids

0

4

8

12

16

0 4 8 12 16

Nus

selt

num

ber (

expe

rimen

tal)

Nusselt number (predicted)

DI water1 TiO2

2 TiO2

1 SiO2

2 SiO2

+6

minus6

Figure 16 Comparison of experimental and predicted Nusseltnumber for plain tube

Journal of Nanomaterials 9

0

01

02

03

04

0 01 02 03 04

Fric

tion

fact

or (e

xper

imen

tal)

Friction factor (predicted)

DI water1 TiO2

2 TiO2

1 SiO2

2 SiO2

+8

minus8

Figure 17 Comparison of experimental and predicted frictionfactor for plain tube

30

35

40

45

50

55

60

0 500 1000 1500 2000

Nus

selt

num

ber (

Nu)

Reynolds number (Re)

DI water1 TiO2

2 TiO2

1 SiO2

2 SiO2

Figure 18 Nusselt number versus Reynolds number for nanofluidswith typical twist tape (119910 = 293)

0

025

05

075

1

125

15

0 500 1000 1500 2000

Reynolds number (Re)

DI water

Fric

tion

fact

or (f

)

1 TiO2

2 TiO21 SiO2

2 SiO2

Figure 19 Nusselt number versus Reynolds number for nanofluidswith typical twist tape (119910 = 293)

0

20

40

60

80

0 20 40 60 80

Nus

selt

num

ber (

expe

rimen

tal)

Nusselt number (predicted)

DI water1 TiO2 2 TiO2

1 SiO2

2 SiO2

+6

minus6

Figure 20 Comparison of experimental and predicted Nusseltnumber with typical twist tape

10 Journal of Nanomaterials

0

025

05

075

1

125

15

0 025 05 075 1 125 15

Fric

tion

fact

or (e

xper

imen

tal)

Friction factor (predicted)

DI water1 TiO2

2 TiO2

1 SiO2

2 SiO2

+8

+8

Figure 21 Comparison of experimental and predicted frictionfactor with typical twist tape

30

35

40

45

50

55

60

65

0 500 1000 1500 2000

Nus

selt

num

ber (

Nu)

Reynolds number (Re)

QCT (2 SiO2)PCT (2 SiO2)VCT (2 SiO2)

TT (2 SiO2)TT (DI water)

Figure 22 Nusselt number versus Reynolds number for typical andconic cut twist tapes

0

03

06

09

12

15

18

0 500 1000 1500 2000

Reynolds number (Re)

QCT (2 SiO2)PCT (2 SiO2)VCT (2 SiO2)

TT (DI water)TT (DI water)

Fric

tion

fact

or (f

)

Figure 23 Friction factor versus Reynolds number for typical andconic cut twist tapes

0

20

40

60

80

0 20 40 60 80

Nus

selt

num

ber (

expe

rimen

tal)

Nusselt number (predicted)

+8

minus8

QCT (2 SiO2)PCT ( SiO2)VCT (2 SiO2)

TT (2 SiO2)TT (DI water)

Figure 24 Comparison of experimental and predicted Nusseltnumber for typical and conic cut twist tapes

Journal of Nanomaterials 11

0

05

1

15

2

0 05 1 15 2

Fric

tion

fact

or (e

xper

imen

tal)

Friction factor (predicted)

QCT (2 SiO2)PCT (2 SiO2)VCT (2 SiO2)

TT (2 SiO2)TT (DI water)

+10

minus10

Figure 25 Comparison of experimental and predicted frictionfactor for typical and conic cut twist tapes

For quadrant cut twisted tape

Nu = 538Pr04Re0226 (1 + 119908

119882)

00387

(1 +119889119890

119882)

minus0187

sdot (1 + 120601)0027

(23)

119891 = 6913Reminus071 (1 + 119908

119882)

0127

(1 +119889119890

119882)

minus016

sdot (1 + 120601)031

(24)

65 Thermal Performance of Twist Tapes The performanceanalysis of typical and conic cut twisted tape inserts in lami-nar flow of SiO

2nanofluid was accomplished by evaluating

thermal performance factor for constant pumping powercondition Thermal performance factor (120578) at constantspumping power is defined as ratio of the convective heattransfer coefficient of the tube with turbulator or enhancingmethod to that of the plain tube The following thermalperformance factor for laminar proposed by [29] is used forperformance analysis

120578 =(NuNu

119900)

(119891119891119900)01666

(25)

where Nu 119891 Nu119900 and 119891

119900are the Nusselt numbers and

friction factors for a duct configuration with and withoutinserts respectively

2

3

4

5

6

0 500 1000 1500 2000

Reynolds number (Re)

QCT (2 SiO2)PCT (2 SiO2)VCT (2 SiO2) TT (2 SiO2)

TT (DI water)

Ther

mal

per

form

ance

fact

or (120578

)

Figure 26 Variation of the thermal performance factor of typicaland conic cut twist tape

Figure 26 shows the variation of thermal performancefactor with Reynolds number for 2 volume concentrationof SiO

2nanofluid The values of thermal performance factor

at all Reynolds were found to be greater than unity for bothtypical and conic cut twisted tape inserts This indicates thattwist tape inserts are feasible in terms of energy saving in lam-inar flow regime It is evident that the thermal performancefactor triangular cut twist tape at constant Reynolds numberis higher than other twist tapes This is due to the strongerturbulenceswirl flow generated by alternative cuts along theedge twist tape The thermal performance factor was foundto be decreasing with increases in Reynolds number Thisis because of the increase in pressure loss as the Reynoldsnumber increases

The experimental results showed that the thermal perfor-mance factor is around 513ndash416 for VCT 498ndash408 for PCT488ndash405 for QCT and 483ndash401 for TT when used with2 SiO

2nanofluid While the thermal performance factor

to be around 475ndash396 for TT with water Therefore theVCT insert shows better thermal performance when usedwith SiO

2nanofluid than other twist tapesThe experimental

results are used to derive the following correlations of thermalperformance factor using least square method of regressionanalysis These correlations are valid for laminar flow (Re lt

1500) of water and 2 volume concentration SiO2for typical

and conic cut twist tapesThe comparisons between the ther-mal performance factor values obtained from experimentaldata and those predicted from the above correlations are

12 Journal of Nanomaterials

3

4

5

6

3 4 5 6

QCT (2 SiO2)PCT (2 SiO2)VCT (2 SiO2) TT (2 SiO2)

TT (DI water)

+6

minus6

Ther

mal

per

form

ance

fact

or (e

xper

imen

tal)

Thermal performance factor (predicted)

Figure 27 Comparison of experimental and predicted thermalperformance for typical and conic cut twist tapes

shown in Figure 27 As shown the predicted data are in goodagreement with the experimental data

For VCT twisted tape

120578 = 5173Reminus0118 (1 + 119908

119882)

2483

(1 +119889119890

119882)

minus0247

sdot (1 + 120601SiO2

)00183

(26)

For PCT twisted tape

120578 = 5173Re00945 (1 + 119908

119882)

3113

(1 +119889119890

119882)

minus0247

sdot (1 + 120601SiO2

)00183

(27)

For QCT twisted tape

120578 = 5173Re0118 (1 + 119908

119882)

349

(1 +119889119890

119882)

minus0247

sdot (1 + 120601SiO2

)00183

(28)

For TT twisted tape with SiO nanofluid

120578 = 791Re0093 (1 + 120601SiO2

)1283

(29)

For TT twisted tape with deionized water

120578 = 791Re0093 (30)

7 Conclusions

Heat transfer friction and thermal performance characteris-tics of SiO

2and TiO

2nanofluids with two concentrations of

1 and 2 by volume in a circular tube fitted with a typicaland conic cut twist tape in the laminar regime have beenexperimentally investigated The main conclusions from thisexperimental study are as follows

(71) SiO2and TiO

2nanofluids of different volume con-

centration in plain tube give good enhancement inNusselt number compared to deionized water Thehigher enhancement inNusselt number is obtained bySiO2nanofluids with volume concentrations of 2

(72) At similar conditions the insertion of typical twisttape causes very significant convective heat transferenhancement in the laminar flow however furtherenhancement is observed by the simultaneous use ofnanofluid with twisted tape compared to the use oftwisted tape or nanofluid alone

(73) The use of nanofluid with the conic cut twist tapeprovides a considerably higher Nusselt number thanthat of nanofluid with the typical twist tape for allReynolds numbers examinedThe triangular cut twisttape offers higher heat transfer rate than the typicaltwist tape and other conic cut configurations

(74) Over the range investigated (Re = 220ndash1500) themaximum thermal performance factor of 513 isfound with the simultaneous use of the triangulartwist tape with SiO

2nanofluid with 2 volume

concentration at Reynolds number of 220(75) The empirical correlations for the Nusselt number

friction factor and the thermal performance factorfor typical and conic cut twist tapes are developedand fitted with the experimental data of water andnanofluids

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

The authors would like to thank the National Universityof Malaysia and the Ministry of Higher Education for thefinancial support (FRGS12013TK07UKM011 and DPP-2013-114) to perform this investigation

References

[1] A Bejan and A D KrausHeat Transfer Handbook John Wileyamp Sons 2003

[2] I Singh and N Diwakar International Journal of AppliedResearch in Mechanical Engineering vol 3 pp 16ndash29 2013

[3] R M Manglik and A E Bergles ldquoHeat transfer and pressuredrop correlations for twisted-tape inserts in isothermal tubes

Journal of Nanomaterials 13

part Imdashlaminar flowsrdquo Journal of Heat Transfer vol 115 no 4pp 881ndash889 1993

[4] S K Saha and D Chakraborty ldquoHeat transfer and pressuredrop characteristics of laminar flow through a circular tubefitted with regularly spaced twisted tape elements with multipletwistsrdquo in Proceedings of the Heat andMass Transfer Conferencepp 313ndash318 Kanpur India 1997

[5] S Al-Fahed L M Chamra and W Chakroun ldquoPressure dropand heat transfer comparison for both microfin tube andtwisted-tape inserts in laminar flowrdquo ExperimentalThermal andFluid Science vol 18 no 4 pp 323ndash333 1998

[6] M S Lokanath and R D Misal ldquoAn experimental study on theperformance of plate heat exchanger and an augmented shelland tube heat exchanger for different types of fluids for marineapplicationsrdquo in Proceedings of the 5th ISHMT-ASME Heat andMass Transfer Conference pp 863ndash868 TataMcGraw-Hill NewDelhi India 2002

[7] P Sivashanmugam and S Suresh ldquoExperimental studies onheat transfer and friction factor characteristics of laminar flowthrough a circular tube fitted with helical screw-tape insertsrdquoApplied Thermal Engineering vol 26 no 16 pp 1990ndash19972006

[8] P Sivashanmugam and S Suresh ldquoExperimental studies onheat transfer and friction factor characteristics of laminar flowthrough a circular tube fitted with regularly spaced helicalscrew-tape insertsrdquo Experimental Thermal and Fluid Sciencevol 31 no 4 pp 301ndash308 2007

[9] S Jaisankar T K Radhakrishnan and K N Sheeba ldquoStudieson heat transfer and friction factor characteristics of ther-mosyphon solar water heating system with helical twistedtapesrdquo Energy vol 34 no 9 pp 1054ndash1064 2009

[10] A V N Kapatkar B D A S Padalkar and C S KasbeldquoExperimental investigation on heat transfer enhancement inlaminar flow in circular tube equipped with different insertsrdquoAMAE International Journal on Manufacturing and MaterialScience vol 1 pp 1ndash6 2011

[11] J Guo A Fan X Zhang and W Liu ldquoA numerical studyon heat transfer and friction factor characteristics of laminarflow in a circular tube fitted with center-cleared twisted taperdquoInternational Journal ofThermal Sciences vol 50 no 7 pp 1263ndash1270 2011

[12] K Wongcharee and S Eiamsa-ard ldquoFriction and heat trans-fer characteristics of laminar swirl flow through the roundtubes inserted with alternate clockwise and counter-clockwisetwisted-tapesrdquo International Communications in Heat andMassTransfer vol 38 no 3 pp 348ndash352 2011

[13] E Z Ibrahim ldquoAugmentation of laminar flow and heat transferin flat tubes by means of helical screw-tape insertsrdquo EnergyConversion and Management vol 52 no 1 pp 250ndash257 2011

[14] S U S Choi and J A Eastman ldquoEnhancing thermal con-ductivity of fluids with nanoparticlesrdquo in Developments andApplications of Non-Newtonian Flows D A Siguier and HP Wang Eds pp 99ndash105 American Society of MechanicalEngineers New York NY USA 1995

[15] C Y Tsai H T Chien P P Ding B Chan T Y Luh and PH Chen ldquoEffect of structural character of gold nanoparticles innanofluid on heat pipe thermal performancerdquoMaterials Lettersvol 58 no 9 pp 1461ndash1465 2004

[16] M-S Liu M C-C Lin C Y Tsai and C-C Wang ldquoEnhance-ment of thermal conductivity with Cu for nanofluids using

chemical reduction methodrdquo International Journal of Heat andMass Transfer vol 49 no 17-18 pp 3028ndash3033 2006

[17] E Tamjid andBHGuenther ldquoRheology and colloidal structureof silver nanoparticles dispersed in diethylene glycolrdquo PowderTechnology vol 197 no 1-2 pp 49ndash53 2010

[18] SM SMurshed K C Leong and C Yang ldquoEnhanced thermalconductivity of TiO

2water based nanofluidsrdquo International

Journal of Thermal Sciences vol 44 no 4 pp 367ndash373 2005[19] H Zhu C Zhang S Liu Y Tang and Y Yin ldquoEffects of

nanoparticle clustering and alignment on thermal conductiv-ities of Fe

3O4aqueous nanofluidsrdquo Applied Physics Letters vol

89 Article ID 023123 2006[20] J A Eastman U S Choi S Li L J Thompson and S Lee

ldquoEnhanced thermal conductivity through the development ofnanofluidsrdquoMRS Proceedings vol 457 1996

[21] M EMeibodi M Vafaie-Sefti AM Rashidi A Amrollahi MTabasi and H S Kalal ldquoSimple model for thermal conductivityof nanofluids using resistance model approachrdquo InternationalCommunications in Heat and Mass Transfer vol 37 no 5 pp555ndash559 2010

[22] G Pathipakka and P Sivashanmugam ldquoHeat transfer behaviourof nanofluids in a uniformly heated circular tube fittedwith heli-cal inserts in laminar flowrdquo Superlattices and Microstructuresvol 47 no 2 pp 349ndash360 2010

[23] K Wongcharee and S Eiamsa-ard ldquoEnhancement of heattransfer using CuOwater nanofluid and twisted tape withalternate axisrdquo International Communications in Heat and MassTransfer vol 38 no 6 pp 742ndash748 2011

[24] S Suresh K P Venkitaraj and P Selvakumar ldquoComparativestudy on thermal performance of helical screw tape inserts inlaminar flow using Al

2O3water and CuOwater nanofluidsrdquo

Superlattices and Microstructures vol 49 no 6 pp 608ndash6222011

[25] S D Salman A A H Kadhum M S Takriff and A BMohamad ldquoHeat transfer enhancement of laminar nanofluidsflow in a circular tube fitted with parabolic-cut twisted tapeinsertsrdquo The Scientific World Journal vol 2014 Article ID543231 7 pages 2014

[26] S D Salman A A H Kadhum M S Takriff and A BMohamad ldquoCFD simulation of heat transfer and friction factoraugmentation in a circular tube fitted with elliptic-cut twistedtape insertsrdquo Mathematical Problems in Engineering vol 2013Article ID 163839 7 pages 2013

[27] S D Salman A A H Kadhum M S Takriff and A BMohamad ldquoCFD analysis of Heat transfer and friction factorcharacteristics in a circular tube fitted with Quadrant-cuttwisted tape insertsrdquoMathematical Problems in Engineering vol2013 Article ID 273764 8 pages 2013

[28] F P Incropera D P Dewitt T L Bergman and A S LavineFundamentals of Heat and Mass Transfer John Wiley amp Sons2007

[29] H Usui Y Sano K Iwashita and A Isozaki ldquoEnhancement ofheat transfer by a combination of internally grooved rough tubeand twisted taperdquo International Chemical Engineering vol 26no 1 pp 97ndash104 1986

[30] J P Holman Experimental Methods for Engineers McGraw-Hill New York NY USA 2011

[31] R K Shah and A L London Laminar Flow Forced Convectionin Ducts Academic Press New York NY USA 1978

14 Journal of Nanomaterials

[32] P KNagarajan andP Sivashanmugam ldquoCFD simulation of heattransfer augmentation in a circular tube fitted with right-lefthelical inserts with spacerrdquo International Journal of ChemicalEngineering Research vol 1 pp 1ndash11 2009

[33] P Keblinski S R Phillpot S U S Choi and J A EastmanldquoMechanisms of heat flow in suspensions of nano-sized particles(nanofluids)rdquo International Journal of Heat and Mass Transfervol 45 no 4 pp 855ndash863 2002

Submit your manuscripts athttpwwwhindawicom

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CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

Journal of Nanomaterials 7N

usse

lt nu

mbe

r (ex

perim

enta

l)

Nusselt number (Manglik and Bergles equation)

y = 293

+15

minus15

0

20

40

60

80

100

0 20 40 60 80 100

Figure 11 Comparison of experimental and predicted Nusseltnumber of the plain tube fitted with typical twisted tape

with the experimental data within plusmn6 for Nusselt numberand plusmn8 friction factor as shown in Figures 20 and 21

Nu = 5236Pr04Re02357119910minus00881 (1 + 120601)0124 (17)

119891 = 76789Reminus0686119910minus0375 (1 + 120601)0198 (18)

64 Effect of Twist Tape Configuration The influence of andconic (quadrant parabolic half and triangular) cut twistedtape of twist ratio 119910 = 293 and cut depth 119889

119890= 05 cm

with 2 volume concentration of SiO2nanofluid on Nusselt

number and friction factor are shown in Figures 22 and 23Apparently from Figure 22 conic cut twist exhibits higherNusselt number than the typical twisted tape This can beexplained by the fact that conic cut twist tape generates swirlflow with efficient fluid mixing nearby their alternative cutswhile the typical twist tape causes swirl flow only The resultsalso reveal that the triangular cut twisted tape provides ahigherNusselt number comparedwith the othersThismeansthat the vortices behind the alternative cut edges of triangularcut twist tape give superior efficient fluid mixing resultingin further heat transfer enhancement From Figure 23 it canbe seen that friction factor decreases with the increase ofReynolds number and triangular cut twisted tape (VCT) giveshigher friction factor compared with all the other Reynoldsnumbers This implies that the influence of alternative cutsalong the edge of the triangular cut twisted tape promotesadditional wall shear stress due to flow mixing betweenthe fluids at the twist tape and tube wall In addition theexperimental data of conic cut twisted tapes with water (120601 =

0) and nanofluids (120601 = 2) were used to develop the

Nus

selt

num

ber (

Nu)

Reynolds number (Re)

RLT (y = 293) expTT (y = 293) exp

0

15

30

45

60

75

0 500 1000 1500 2000

Figure 12 Experimental Nusselt number of typical twist tape withRLT inserts

following correlations for Nusselt number and friction factorwith reasonable agreement as shown in Figures 24 and 25

For triangular cut twisted tape

Nu = 5387Pr04Re0229 (1 + 119908

119882)

00383

(1 +119889119890

119882)

minus0185

sdot (1 + 120601)0025

(19)

119891 = 6184Reminus067 (1 + 119908

119882)

0127

(1 +119889119890

119882)

minus0468

sdot (1 + 120601)0137

(20)

For parabolic half cut twisted tape

Nu = 5388Pr04Re0229 (1 + 119908

119882)

00384

(1 +119889119890

119882)

minus0184

sdot (1 + 120601)0025

(21)

119891 = 6876Reminus06771 (1 + 119908

119882)

0137

(1 +119889119890

119882)

minus0197

sdot (1 + 120601)00134

(22)

8 Journal of Nanomaterials

0

05

1

15

2

0 500 1000 1500 2000

Reynolds number (Re)

RLT (y = 293) expTT (y = 293) exp

Fric

tion

fact

or (f

)

Figure 13 Experimental friction factor of typical twist tape withRLT inserts

Nus

selt

num

ber (

Nu)

Reynolds number (Re)

DI water1 TiO2

2 TiO2

1 SiO2

2 SiO2

4

6

8

10

12

0 500 1000 1500 2000

Figure 14 Nusselt number versus Reynolds number for plain tubewith nanofluids

0

01

02

03

04

0 500 1000 1500 2000

Reynolds number (Re)

DI water1 TiO2

2 TiO2

1 SiO2

2 SiO2

Fric

tion

fact

or (f

)

Figure 15 Friction factor versus Reynolds number for plain tubewith nanofluids

0

4

8

12

16

0 4 8 12 16

Nus

selt

num

ber (

expe

rimen

tal)

Nusselt number (predicted)

DI water1 TiO2

2 TiO2

1 SiO2

2 SiO2

+6

minus6

Figure 16 Comparison of experimental and predicted Nusseltnumber for plain tube

Journal of Nanomaterials 9

0

01

02

03

04

0 01 02 03 04

Fric

tion

fact

or (e

xper

imen

tal)

Friction factor (predicted)

DI water1 TiO2

2 TiO2

1 SiO2

2 SiO2

+8

minus8

Figure 17 Comparison of experimental and predicted frictionfactor for plain tube

30

35

40

45

50

55

60

0 500 1000 1500 2000

Nus

selt

num

ber (

Nu)

Reynolds number (Re)

DI water1 TiO2

2 TiO2

1 SiO2

2 SiO2

Figure 18 Nusselt number versus Reynolds number for nanofluidswith typical twist tape (119910 = 293)

0

025

05

075

1

125

15

0 500 1000 1500 2000

Reynolds number (Re)

DI water

Fric

tion

fact

or (f

)

1 TiO2

2 TiO21 SiO2

2 SiO2

Figure 19 Nusselt number versus Reynolds number for nanofluidswith typical twist tape (119910 = 293)

0

20

40

60

80

0 20 40 60 80

Nus

selt

num

ber (

expe

rimen

tal)

Nusselt number (predicted)

DI water1 TiO2 2 TiO2

1 SiO2

2 SiO2

+6

minus6

Figure 20 Comparison of experimental and predicted Nusseltnumber with typical twist tape

10 Journal of Nanomaterials

0

025

05

075

1

125

15

0 025 05 075 1 125 15

Fric

tion

fact

or (e

xper

imen

tal)

Friction factor (predicted)

DI water1 TiO2

2 TiO2

1 SiO2

2 SiO2

+8

+8

Figure 21 Comparison of experimental and predicted frictionfactor with typical twist tape

30

35

40

45

50

55

60

65

0 500 1000 1500 2000

Nus

selt

num

ber (

Nu)

Reynolds number (Re)

QCT (2 SiO2)PCT (2 SiO2)VCT (2 SiO2)

TT (2 SiO2)TT (DI water)

Figure 22 Nusselt number versus Reynolds number for typical andconic cut twist tapes

0

03

06

09

12

15

18

0 500 1000 1500 2000

Reynolds number (Re)

QCT (2 SiO2)PCT (2 SiO2)VCT (2 SiO2)

TT (DI water)TT (DI water)

Fric

tion

fact

or (f

)

Figure 23 Friction factor versus Reynolds number for typical andconic cut twist tapes

0

20

40

60

80

0 20 40 60 80

Nus

selt

num

ber (

expe

rimen

tal)

Nusselt number (predicted)

+8

minus8

QCT (2 SiO2)PCT ( SiO2)VCT (2 SiO2)

TT (2 SiO2)TT (DI water)

Figure 24 Comparison of experimental and predicted Nusseltnumber for typical and conic cut twist tapes

Journal of Nanomaterials 11

0

05

1

15

2

0 05 1 15 2

Fric

tion

fact

or (e

xper

imen

tal)

Friction factor (predicted)

QCT (2 SiO2)PCT (2 SiO2)VCT (2 SiO2)

TT (2 SiO2)TT (DI water)

+10

minus10

Figure 25 Comparison of experimental and predicted frictionfactor for typical and conic cut twist tapes

For quadrant cut twisted tape

Nu = 538Pr04Re0226 (1 + 119908

119882)

00387

(1 +119889119890

119882)

minus0187

sdot (1 + 120601)0027

(23)

119891 = 6913Reminus071 (1 + 119908

119882)

0127

(1 +119889119890

119882)

minus016

sdot (1 + 120601)031

(24)

65 Thermal Performance of Twist Tapes The performanceanalysis of typical and conic cut twisted tape inserts in lami-nar flow of SiO

2nanofluid was accomplished by evaluating

thermal performance factor for constant pumping powercondition Thermal performance factor (120578) at constantspumping power is defined as ratio of the convective heattransfer coefficient of the tube with turbulator or enhancingmethod to that of the plain tube The following thermalperformance factor for laminar proposed by [29] is used forperformance analysis

120578 =(NuNu

119900)

(119891119891119900)01666

(25)

where Nu 119891 Nu119900 and 119891

119900are the Nusselt numbers and

friction factors for a duct configuration with and withoutinserts respectively

2

3

4

5

6

0 500 1000 1500 2000

Reynolds number (Re)

QCT (2 SiO2)PCT (2 SiO2)VCT (2 SiO2) TT (2 SiO2)

TT (DI water)

Ther

mal

per

form

ance

fact

or (120578

)

Figure 26 Variation of the thermal performance factor of typicaland conic cut twist tape

Figure 26 shows the variation of thermal performancefactor with Reynolds number for 2 volume concentrationof SiO

2nanofluid The values of thermal performance factor

at all Reynolds were found to be greater than unity for bothtypical and conic cut twisted tape inserts This indicates thattwist tape inserts are feasible in terms of energy saving in lam-inar flow regime It is evident that the thermal performancefactor triangular cut twist tape at constant Reynolds numberis higher than other twist tapes This is due to the strongerturbulenceswirl flow generated by alternative cuts along theedge twist tape The thermal performance factor was foundto be decreasing with increases in Reynolds number Thisis because of the increase in pressure loss as the Reynoldsnumber increases

The experimental results showed that the thermal perfor-mance factor is around 513ndash416 for VCT 498ndash408 for PCT488ndash405 for QCT and 483ndash401 for TT when used with2 SiO

2nanofluid While the thermal performance factor

to be around 475ndash396 for TT with water Therefore theVCT insert shows better thermal performance when usedwith SiO

2nanofluid than other twist tapesThe experimental

results are used to derive the following correlations of thermalperformance factor using least square method of regressionanalysis These correlations are valid for laminar flow (Re lt

1500) of water and 2 volume concentration SiO2for typical

and conic cut twist tapesThe comparisons between the ther-mal performance factor values obtained from experimentaldata and those predicted from the above correlations are

12 Journal of Nanomaterials

3

4

5

6

3 4 5 6

QCT (2 SiO2)PCT (2 SiO2)VCT (2 SiO2) TT (2 SiO2)

TT (DI water)

+6

minus6

Ther

mal

per

form

ance

fact

or (e

xper

imen

tal)

Thermal performance factor (predicted)

Figure 27 Comparison of experimental and predicted thermalperformance for typical and conic cut twist tapes

shown in Figure 27 As shown the predicted data are in goodagreement with the experimental data

For VCT twisted tape

120578 = 5173Reminus0118 (1 + 119908

119882)

2483

(1 +119889119890

119882)

minus0247

sdot (1 + 120601SiO2

)00183

(26)

For PCT twisted tape

120578 = 5173Re00945 (1 + 119908

119882)

3113

(1 +119889119890

119882)

minus0247

sdot (1 + 120601SiO2

)00183

(27)

For QCT twisted tape

120578 = 5173Re0118 (1 + 119908

119882)

349

(1 +119889119890

119882)

minus0247

sdot (1 + 120601SiO2

)00183

(28)

For TT twisted tape with SiO nanofluid

120578 = 791Re0093 (1 + 120601SiO2

)1283

(29)

For TT twisted tape with deionized water

120578 = 791Re0093 (30)

7 Conclusions

Heat transfer friction and thermal performance characteris-tics of SiO

2and TiO

2nanofluids with two concentrations of

1 and 2 by volume in a circular tube fitted with a typicaland conic cut twist tape in the laminar regime have beenexperimentally investigated The main conclusions from thisexperimental study are as follows

(71) SiO2and TiO

2nanofluids of different volume con-

centration in plain tube give good enhancement inNusselt number compared to deionized water Thehigher enhancement inNusselt number is obtained bySiO2nanofluids with volume concentrations of 2

(72) At similar conditions the insertion of typical twisttape causes very significant convective heat transferenhancement in the laminar flow however furtherenhancement is observed by the simultaneous use ofnanofluid with twisted tape compared to the use oftwisted tape or nanofluid alone

(73) The use of nanofluid with the conic cut twist tapeprovides a considerably higher Nusselt number thanthat of nanofluid with the typical twist tape for allReynolds numbers examinedThe triangular cut twisttape offers higher heat transfer rate than the typicaltwist tape and other conic cut configurations

(74) Over the range investigated (Re = 220ndash1500) themaximum thermal performance factor of 513 isfound with the simultaneous use of the triangulartwist tape with SiO

2nanofluid with 2 volume

concentration at Reynolds number of 220(75) The empirical correlations for the Nusselt number

friction factor and the thermal performance factorfor typical and conic cut twist tapes are developedand fitted with the experimental data of water andnanofluids

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

The authors would like to thank the National Universityof Malaysia and the Ministry of Higher Education for thefinancial support (FRGS12013TK07UKM011 and DPP-2013-114) to perform this investigation

References

[1] A Bejan and A D KrausHeat Transfer Handbook John Wileyamp Sons 2003

[2] I Singh and N Diwakar International Journal of AppliedResearch in Mechanical Engineering vol 3 pp 16ndash29 2013

[3] R M Manglik and A E Bergles ldquoHeat transfer and pressuredrop correlations for twisted-tape inserts in isothermal tubes

Journal of Nanomaterials 13

part Imdashlaminar flowsrdquo Journal of Heat Transfer vol 115 no 4pp 881ndash889 1993

[4] S K Saha and D Chakraborty ldquoHeat transfer and pressuredrop characteristics of laminar flow through a circular tubefitted with regularly spaced twisted tape elements with multipletwistsrdquo in Proceedings of the Heat andMass Transfer Conferencepp 313ndash318 Kanpur India 1997

[5] S Al-Fahed L M Chamra and W Chakroun ldquoPressure dropand heat transfer comparison for both microfin tube andtwisted-tape inserts in laminar flowrdquo ExperimentalThermal andFluid Science vol 18 no 4 pp 323ndash333 1998

[6] M S Lokanath and R D Misal ldquoAn experimental study on theperformance of plate heat exchanger and an augmented shelland tube heat exchanger for different types of fluids for marineapplicationsrdquo in Proceedings of the 5th ISHMT-ASME Heat andMass Transfer Conference pp 863ndash868 TataMcGraw-Hill NewDelhi India 2002

[7] P Sivashanmugam and S Suresh ldquoExperimental studies onheat transfer and friction factor characteristics of laminar flowthrough a circular tube fitted with helical screw-tape insertsrdquoApplied Thermal Engineering vol 26 no 16 pp 1990ndash19972006

[8] P Sivashanmugam and S Suresh ldquoExperimental studies onheat transfer and friction factor characteristics of laminar flowthrough a circular tube fitted with regularly spaced helicalscrew-tape insertsrdquo Experimental Thermal and Fluid Sciencevol 31 no 4 pp 301ndash308 2007

[9] S Jaisankar T K Radhakrishnan and K N Sheeba ldquoStudieson heat transfer and friction factor characteristics of ther-mosyphon solar water heating system with helical twistedtapesrdquo Energy vol 34 no 9 pp 1054ndash1064 2009

[10] A V N Kapatkar B D A S Padalkar and C S KasbeldquoExperimental investigation on heat transfer enhancement inlaminar flow in circular tube equipped with different insertsrdquoAMAE International Journal on Manufacturing and MaterialScience vol 1 pp 1ndash6 2011

[11] J Guo A Fan X Zhang and W Liu ldquoA numerical studyon heat transfer and friction factor characteristics of laminarflow in a circular tube fitted with center-cleared twisted taperdquoInternational Journal ofThermal Sciences vol 50 no 7 pp 1263ndash1270 2011

[12] K Wongcharee and S Eiamsa-ard ldquoFriction and heat trans-fer characteristics of laminar swirl flow through the roundtubes inserted with alternate clockwise and counter-clockwisetwisted-tapesrdquo International Communications in Heat andMassTransfer vol 38 no 3 pp 348ndash352 2011

[13] E Z Ibrahim ldquoAugmentation of laminar flow and heat transferin flat tubes by means of helical screw-tape insertsrdquo EnergyConversion and Management vol 52 no 1 pp 250ndash257 2011

[14] S U S Choi and J A Eastman ldquoEnhancing thermal con-ductivity of fluids with nanoparticlesrdquo in Developments andApplications of Non-Newtonian Flows D A Siguier and HP Wang Eds pp 99ndash105 American Society of MechanicalEngineers New York NY USA 1995

[15] C Y Tsai H T Chien P P Ding B Chan T Y Luh and PH Chen ldquoEffect of structural character of gold nanoparticles innanofluid on heat pipe thermal performancerdquoMaterials Lettersvol 58 no 9 pp 1461ndash1465 2004

[16] M-S Liu M C-C Lin C Y Tsai and C-C Wang ldquoEnhance-ment of thermal conductivity with Cu for nanofluids using

chemical reduction methodrdquo International Journal of Heat andMass Transfer vol 49 no 17-18 pp 3028ndash3033 2006

[17] E Tamjid andBHGuenther ldquoRheology and colloidal structureof silver nanoparticles dispersed in diethylene glycolrdquo PowderTechnology vol 197 no 1-2 pp 49ndash53 2010

[18] SM SMurshed K C Leong and C Yang ldquoEnhanced thermalconductivity of TiO

2water based nanofluidsrdquo International

Journal of Thermal Sciences vol 44 no 4 pp 367ndash373 2005[19] H Zhu C Zhang S Liu Y Tang and Y Yin ldquoEffects of

nanoparticle clustering and alignment on thermal conductiv-ities of Fe

3O4aqueous nanofluidsrdquo Applied Physics Letters vol

89 Article ID 023123 2006[20] J A Eastman U S Choi S Li L J Thompson and S Lee

ldquoEnhanced thermal conductivity through the development ofnanofluidsrdquoMRS Proceedings vol 457 1996

[21] M EMeibodi M Vafaie-Sefti AM Rashidi A Amrollahi MTabasi and H S Kalal ldquoSimple model for thermal conductivityof nanofluids using resistance model approachrdquo InternationalCommunications in Heat and Mass Transfer vol 37 no 5 pp555ndash559 2010

[22] G Pathipakka and P Sivashanmugam ldquoHeat transfer behaviourof nanofluids in a uniformly heated circular tube fittedwith heli-cal inserts in laminar flowrdquo Superlattices and Microstructuresvol 47 no 2 pp 349ndash360 2010

[23] K Wongcharee and S Eiamsa-ard ldquoEnhancement of heattransfer using CuOwater nanofluid and twisted tape withalternate axisrdquo International Communications in Heat and MassTransfer vol 38 no 6 pp 742ndash748 2011

[24] S Suresh K P Venkitaraj and P Selvakumar ldquoComparativestudy on thermal performance of helical screw tape inserts inlaminar flow using Al

2O3water and CuOwater nanofluidsrdquo

Superlattices and Microstructures vol 49 no 6 pp 608ndash6222011

[25] S D Salman A A H Kadhum M S Takriff and A BMohamad ldquoHeat transfer enhancement of laminar nanofluidsflow in a circular tube fitted with parabolic-cut twisted tapeinsertsrdquo The Scientific World Journal vol 2014 Article ID543231 7 pages 2014

[26] S D Salman A A H Kadhum M S Takriff and A BMohamad ldquoCFD simulation of heat transfer and friction factoraugmentation in a circular tube fitted with elliptic-cut twistedtape insertsrdquo Mathematical Problems in Engineering vol 2013Article ID 163839 7 pages 2013

[27] S D Salman A A H Kadhum M S Takriff and A BMohamad ldquoCFD analysis of Heat transfer and friction factorcharacteristics in a circular tube fitted with Quadrant-cuttwisted tape insertsrdquoMathematical Problems in Engineering vol2013 Article ID 273764 8 pages 2013

[28] F P Incropera D P Dewitt T L Bergman and A S LavineFundamentals of Heat and Mass Transfer John Wiley amp Sons2007

[29] H Usui Y Sano K Iwashita and A Isozaki ldquoEnhancement ofheat transfer by a combination of internally grooved rough tubeand twisted taperdquo International Chemical Engineering vol 26no 1 pp 97ndash104 1986

[30] J P Holman Experimental Methods for Engineers McGraw-Hill New York NY USA 2011

[31] R K Shah and A L London Laminar Flow Forced Convectionin Ducts Academic Press New York NY USA 1978

14 Journal of Nanomaterials

[32] P KNagarajan andP Sivashanmugam ldquoCFD simulation of heattransfer augmentation in a circular tube fitted with right-lefthelical inserts with spacerrdquo International Journal of ChemicalEngineering Research vol 1 pp 1ndash11 2009

[33] P Keblinski S R Phillpot S U S Choi and J A EastmanldquoMechanisms of heat flow in suspensions of nano-sized particles(nanofluids)rdquo International Journal of Heat and Mass Transfervol 45 no 4 pp 855ndash863 2002

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

8 Journal of Nanomaterials

0

05

1

15

2

0 500 1000 1500 2000

Reynolds number (Re)

RLT (y = 293) expTT (y = 293) exp

Fric

tion

fact

or (f

)

Figure 13 Experimental friction factor of typical twist tape withRLT inserts

Nus

selt

num

ber (

Nu)

Reynolds number (Re)

DI water1 TiO2

2 TiO2

1 SiO2

2 SiO2

4

6

8

10

12

0 500 1000 1500 2000

Figure 14 Nusselt number versus Reynolds number for plain tubewith nanofluids

0

01

02

03

04

0 500 1000 1500 2000

Reynolds number (Re)

DI water1 TiO2

2 TiO2

1 SiO2

2 SiO2

Fric

tion

fact

or (f

)

Figure 15 Friction factor versus Reynolds number for plain tubewith nanofluids

0

4

8

12

16

0 4 8 12 16

Nus

selt

num

ber (

expe

rimen

tal)

Nusselt number (predicted)

DI water1 TiO2

2 TiO2

1 SiO2

2 SiO2

+6

minus6

Figure 16 Comparison of experimental and predicted Nusseltnumber for plain tube

Journal of Nanomaterials 9

0

01

02

03

04

0 01 02 03 04

Fric

tion

fact

or (e

xper

imen

tal)

Friction factor (predicted)

DI water1 TiO2

2 TiO2

1 SiO2

2 SiO2

+8

minus8

Figure 17 Comparison of experimental and predicted frictionfactor for plain tube

30

35

40

45

50

55

60

0 500 1000 1500 2000

Nus

selt

num

ber (

Nu)

Reynolds number (Re)

DI water1 TiO2

2 TiO2

1 SiO2

2 SiO2

Figure 18 Nusselt number versus Reynolds number for nanofluidswith typical twist tape (119910 = 293)

0

025

05

075

1

125

15

0 500 1000 1500 2000

Reynolds number (Re)

DI water

Fric

tion

fact

or (f

)

1 TiO2

2 TiO21 SiO2

2 SiO2

Figure 19 Nusselt number versus Reynolds number for nanofluidswith typical twist tape (119910 = 293)

0

20

40

60

80

0 20 40 60 80

Nus

selt

num

ber (

expe

rimen

tal)

Nusselt number (predicted)

DI water1 TiO2 2 TiO2

1 SiO2

2 SiO2

+6

minus6

Figure 20 Comparison of experimental and predicted Nusseltnumber with typical twist tape

10 Journal of Nanomaterials

0

025

05

075

1

125

15

0 025 05 075 1 125 15

Fric

tion

fact

or (e

xper

imen

tal)

Friction factor (predicted)

DI water1 TiO2

2 TiO2

1 SiO2

2 SiO2

+8

+8

Figure 21 Comparison of experimental and predicted frictionfactor with typical twist tape

30

35

40

45

50

55

60

65

0 500 1000 1500 2000

Nus

selt

num

ber (

Nu)

Reynolds number (Re)

QCT (2 SiO2)PCT (2 SiO2)VCT (2 SiO2)

TT (2 SiO2)TT (DI water)

Figure 22 Nusselt number versus Reynolds number for typical andconic cut twist tapes

0

03

06

09

12

15

18

0 500 1000 1500 2000

Reynolds number (Re)

QCT (2 SiO2)PCT (2 SiO2)VCT (2 SiO2)

TT (DI water)TT (DI water)

Fric

tion

fact

or (f

)

Figure 23 Friction factor versus Reynolds number for typical andconic cut twist tapes

0

20

40

60

80

0 20 40 60 80

Nus

selt

num

ber (

expe

rimen

tal)

Nusselt number (predicted)

+8

minus8

QCT (2 SiO2)PCT ( SiO2)VCT (2 SiO2)

TT (2 SiO2)TT (DI water)

Figure 24 Comparison of experimental and predicted Nusseltnumber for typical and conic cut twist tapes

Journal of Nanomaterials 11

0

05

1

15

2

0 05 1 15 2

Fric

tion

fact

or (e

xper

imen

tal)

Friction factor (predicted)

QCT (2 SiO2)PCT (2 SiO2)VCT (2 SiO2)

TT (2 SiO2)TT (DI water)

+10

minus10

Figure 25 Comparison of experimental and predicted frictionfactor for typical and conic cut twist tapes

For quadrant cut twisted tape

Nu = 538Pr04Re0226 (1 + 119908

119882)

00387

(1 +119889119890

119882)

minus0187

sdot (1 + 120601)0027

(23)

119891 = 6913Reminus071 (1 + 119908

119882)

0127

(1 +119889119890

119882)

minus016

sdot (1 + 120601)031

(24)

65 Thermal Performance of Twist Tapes The performanceanalysis of typical and conic cut twisted tape inserts in lami-nar flow of SiO

2nanofluid was accomplished by evaluating

thermal performance factor for constant pumping powercondition Thermal performance factor (120578) at constantspumping power is defined as ratio of the convective heattransfer coefficient of the tube with turbulator or enhancingmethod to that of the plain tube The following thermalperformance factor for laminar proposed by [29] is used forperformance analysis

120578 =(NuNu

119900)

(119891119891119900)01666

(25)

where Nu 119891 Nu119900 and 119891

119900are the Nusselt numbers and

friction factors for a duct configuration with and withoutinserts respectively

2

3

4

5

6

0 500 1000 1500 2000

Reynolds number (Re)

QCT (2 SiO2)PCT (2 SiO2)VCT (2 SiO2) TT (2 SiO2)

TT (DI water)

Ther

mal

per

form

ance

fact

or (120578

)

Figure 26 Variation of the thermal performance factor of typicaland conic cut twist tape

Figure 26 shows the variation of thermal performancefactor with Reynolds number for 2 volume concentrationof SiO

2nanofluid The values of thermal performance factor

at all Reynolds were found to be greater than unity for bothtypical and conic cut twisted tape inserts This indicates thattwist tape inserts are feasible in terms of energy saving in lam-inar flow regime It is evident that the thermal performancefactor triangular cut twist tape at constant Reynolds numberis higher than other twist tapes This is due to the strongerturbulenceswirl flow generated by alternative cuts along theedge twist tape The thermal performance factor was foundto be decreasing with increases in Reynolds number Thisis because of the increase in pressure loss as the Reynoldsnumber increases

The experimental results showed that the thermal perfor-mance factor is around 513ndash416 for VCT 498ndash408 for PCT488ndash405 for QCT and 483ndash401 for TT when used with2 SiO

2nanofluid While the thermal performance factor

to be around 475ndash396 for TT with water Therefore theVCT insert shows better thermal performance when usedwith SiO

2nanofluid than other twist tapesThe experimental

results are used to derive the following correlations of thermalperformance factor using least square method of regressionanalysis These correlations are valid for laminar flow (Re lt

1500) of water and 2 volume concentration SiO2for typical

and conic cut twist tapesThe comparisons between the ther-mal performance factor values obtained from experimentaldata and those predicted from the above correlations are

12 Journal of Nanomaterials

3

4

5

6

3 4 5 6

QCT (2 SiO2)PCT (2 SiO2)VCT (2 SiO2) TT (2 SiO2)

TT (DI water)

+6

minus6

Ther

mal

per

form

ance

fact

or (e

xper

imen

tal)

Thermal performance factor (predicted)

Figure 27 Comparison of experimental and predicted thermalperformance for typical and conic cut twist tapes

shown in Figure 27 As shown the predicted data are in goodagreement with the experimental data

For VCT twisted tape

120578 = 5173Reminus0118 (1 + 119908

119882)

2483

(1 +119889119890

119882)

minus0247

sdot (1 + 120601SiO2

)00183

(26)

For PCT twisted tape

120578 = 5173Re00945 (1 + 119908

119882)

3113

(1 +119889119890

119882)

minus0247

sdot (1 + 120601SiO2

)00183

(27)

For QCT twisted tape

120578 = 5173Re0118 (1 + 119908

119882)

349

(1 +119889119890

119882)

minus0247

sdot (1 + 120601SiO2

)00183

(28)

For TT twisted tape with SiO nanofluid

120578 = 791Re0093 (1 + 120601SiO2

)1283

(29)

For TT twisted tape with deionized water

120578 = 791Re0093 (30)

7 Conclusions

Heat transfer friction and thermal performance characteris-tics of SiO

2and TiO

2nanofluids with two concentrations of

1 and 2 by volume in a circular tube fitted with a typicaland conic cut twist tape in the laminar regime have beenexperimentally investigated The main conclusions from thisexperimental study are as follows

(71) SiO2and TiO

2nanofluids of different volume con-

centration in plain tube give good enhancement inNusselt number compared to deionized water Thehigher enhancement inNusselt number is obtained bySiO2nanofluids with volume concentrations of 2

(72) At similar conditions the insertion of typical twisttape causes very significant convective heat transferenhancement in the laminar flow however furtherenhancement is observed by the simultaneous use ofnanofluid with twisted tape compared to the use oftwisted tape or nanofluid alone

(73) The use of nanofluid with the conic cut twist tapeprovides a considerably higher Nusselt number thanthat of nanofluid with the typical twist tape for allReynolds numbers examinedThe triangular cut twisttape offers higher heat transfer rate than the typicaltwist tape and other conic cut configurations

(74) Over the range investigated (Re = 220ndash1500) themaximum thermal performance factor of 513 isfound with the simultaneous use of the triangulartwist tape with SiO

2nanofluid with 2 volume

concentration at Reynolds number of 220(75) The empirical correlations for the Nusselt number

friction factor and the thermal performance factorfor typical and conic cut twist tapes are developedand fitted with the experimental data of water andnanofluids

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

The authors would like to thank the National Universityof Malaysia and the Ministry of Higher Education for thefinancial support (FRGS12013TK07UKM011 and DPP-2013-114) to perform this investigation

References

[1] A Bejan and A D KrausHeat Transfer Handbook John Wileyamp Sons 2003

[2] I Singh and N Diwakar International Journal of AppliedResearch in Mechanical Engineering vol 3 pp 16ndash29 2013

[3] R M Manglik and A E Bergles ldquoHeat transfer and pressuredrop correlations for twisted-tape inserts in isothermal tubes

Journal of Nanomaterials 13

part Imdashlaminar flowsrdquo Journal of Heat Transfer vol 115 no 4pp 881ndash889 1993

[4] S K Saha and D Chakraborty ldquoHeat transfer and pressuredrop characteristics of laminar flow through a circular tubefitted with regularly spaced twisted tape elements with multipletwistsrdquo in Proceedings of the Heat andMass Transfer Conferencepp 313ndash318 Kanpur India 1997

[5] S Al-Fahed L M Chamra and W Chakroun ldquoPressure dropand heat transfer comparison for both microfin tube andtwisted-tape inserts in laminar flowrdquo ExperimentalThermal andFluid Science vol 18 no 4 pp 323ndash333 1998

[6] M S Lokanath and R D Misal ldquoAn experimental study on theperformance of plate heat exchanger and an augmented shelland tube heat exchanger for different types of fluids for marineapplicationsrdquo in Proceedings of the 5th ISHMT-ASME Heat andMass Transfer Conference pp 863ndash868 TataMcGraw-Hill NewDelhi India 2002

[7] P Sivashanmugam and S Suresh ldquoExperimental studies onheat transfer and friction factor characteristics of laminar flowthrough a circular tube fitted with helical screw-tape insertsrdquoApplied Thermal Engineering vol 26 no 16 pp 1990ndash19972006

[8] P Sivashanmugam and S Suresh ldquoExperimental studies onheat transfer and friction factor characteristics of laminar flowthrough a circular tube fitted with regularly spaced helicalscrew-tape insertsrdquo Experimental Thermal and Fluid Sciencevol 31 no 4 pp 301ndash308 2007

[9] S Jaisankar T K Radhakrishnan and K N Sheeba ldquoStudieson heat transfer and friction factor characteristics of ther-mosyphon solar water heating system with helical twistedtapesrdquo Energy vol 34 no 9 pp 1054ndash1064 2009

[10] A V N Kapatkar B D A S Padalkar and C S KasbeldquoExperimental investigation on heat transfer enhancement inlaminar flow in circular tube equipped with different insertsrdquoAMAE International Journal on Manufacturing and MaterialScience vol 1 pp 1ndash6 2011

[11] J Guo A Fan X Zhang and W Liu ldquoA numerical studyon heat transfer and friction factor characteristics of laminarflow in a circular tube fitted with center-cleared twisted taperdquoInternational Journal ofThermal Sciences vol 50 no 7 pp 1263ndash1270 2011

[12] K Wongcharee and S Eiamsa-ard ldquoFriction and heat trans-fer characteristics of laminar swirl flow through the roundtubes inserted with alternate clockwise and counter-clockwisetwisted-tapesrdquo International Communications in Heat andMassTransfer vol 38 no 3 pp 348ndash352 2011

[13] E Z Ibrahim ldquoAugmentation of laminar flow and heat transferin flat tubes by means of helical screw-tape insertsrdquo EnergyConversion and Management vol 52 no 1 pp 250ndash257 2011

[14] S U S Choi and J A Eastman ldquoEnhancing thermal con-ductivity of fluids with nanoparticlesrdquo in Developments andApplications of Non-Newtonian Flows D A Siguier and HP Wang Eds pp 99ndash105 American Society of MechanicalEngineers New York NY USA 1995

[15] C Y Tsai H T Chien P P Ding B Chan T Y Luh and PH Chen ldquoEffect of structural character of gold nanoparticles innanofluid on heat pipe thermal performancerdquoMaterials Lettersvol 58 no 9 pp 1461ndash1465 2004

[16] M-S Liu M C-C Lin C Y Tsai and C-C Wang ldquoEnhance-ment of thermal conductivity with Cu for nanofluids using

chemical reduction methodrdquo International Journal of Heat andMass Transfer vol 49 no 17-18 pp 3028ndash3033 2006

[17] E Tamjid andBHGuenther ldquoRheology and colloidal structureof silver nanoparticles dispersed in diethylene glycolrdquo PowderTechnology vol 197 no 1-2 pp 49ndash53 2010

[18] SM SMurshed K C Leong and C Yang ldquoEnhanced thermalconductivity of TiO

2water based nanofluidsrdquo International

Journal of Thermal Sciences vol 44 no 4 pp 367ndash373 2005[19] H Zhu C Zhang S Liu Y Tang and Y Yin ldquoEffects of

nanoparticle clustering and alignment on thermal conductiv-ities of Fe

3O4aqueous nanofluidsrdquo Applied Physics Letters vol

89 Article ID 023123 2006[20] J A Eastman U S Choi S Li L J Thompson and S Lee

ldquoEnhanced thermal conductivity through the development ofnanofluidsrdquoMRS Proceedings vol 457 1996

[21] M EMeibodi M Vafaie-Sefti AM Rashidi A Amrollahi MTabasi and H S Kalal ldquoSimple model for thermal conductivityof nanofluids using resistance model approachrdquo InternationalCommunications in Heat and Mass Transfer vol 37 no 5 pp555ndash559 2010

[22] G Pathipakka and P Sivashanmugam ldquoHeat transfer behaviourof nanofluids in a uniformly heated circular tube fittedwith heli-cal inserts in laminar flowrdquo Superlattices and Microstructuresvol 47 no 2 pp 349ndash360 2010

[23] K Wongcharee and S Eiamsa-ard ldquoEnhancement of heattransfer using CuOwater nanofluid and twisted tape withalternate axisrdquo International Communications in Heat and MassTransfer vol 38 no 6 pp 742ndash748 2011

[24] S Suresh K P Venkitaraj and P Selvakumar ldquoComparativestudy on thermal performance of helical screw tape inserts inlaminar flow using Al

2O3water and CuOwater nanofluidsrdquo

Superlattices and Microstructures vol 49 no 6 pp 608ndash6222011

[25] S D Salman A A H Kadhum M S Takriff and A BMohamad ldquoHeat transfer enhancement of laminar nanofluidsflow in a circular tube fitted with parabolic-cut twisted tapeinsertsrdquo The Scientific World Journal vol 2014 Article ID543231 7 pages 2014

[26] S D Salman A A H Kadhum M S Takriff and A BMohamad ldquoCFD simulation of heat transfer and friction factoraugmentation in a circular tube fitted with elliptic-cut twistedtape insertsrdquo Mathematical Problems in Engineering vol 2013Article ID 163839 7 pages 2013

[27] S D Salman A A H Kadhum M S Takriff and A BMohamad ldquoCFD analysis of Heat transfer and friction factorcharacteristics in a circular tube fitted with Quadrant-cuttwisted tape insertsrdquoMathematical Problems in Engineering vol2013 Article ID 273764 8 pages 2013

[28] F P Incropera D P Dewitt T L Bergman and A S LavineFundamentals of Heat and Mass Transfer John Wiley amp Sons2007

[29] H Usui Y Sano K Iwashita and A Isozaki ldquoEnhancement ofheat transfer by a combination of internally grooved rough tubeand twisted taperdquo International Chemical Engineering vol 26no 1 pp 97ndash104 1986

[30] J P Holman Experimental Methods for Engineers McGraw-Hill New York NY USA 2011

[31] R K Shah and A L London Laminar Flow Forced Convectionin Ducts Academic Press New York NY USA 1978

14 Journal of Nanomaterials

[32] P KNagarajan andP Sivashanmugam ldquoCFD simulation of heattransfer augmentation in a circular tube fitted with right-lefthelical inserts with spacerrdquo International Journal of ChemicalEngineering Research vol 1 pp 1ndash11 2009

[33] P Keblinski S R Phillpot S U S Choi and J A EastmanldquoMechanisms of heat flow in suspensions of nano-sized particles(nanofluids)rdquo International Journal of Heat and Mass Transfervol 45 no 4 pp 855ndash863 2002

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

Journal of Nanomaterials 9

0

01

02

03

04

0 01 02 03 04

Fric

tion

fact

or (e

xper

imen

tal)

Friction factor (predicted)

DI water1 TiO2

2 TiO2

1 SiO2

2 SiO2

+8

minus8

Figure 17 Comparison of experimental and predicted frictionfactor for plain tube

30

35

40

45

50

55

60

0 500 1000 1500 2000

Nus

selt

num

ber (

Nu)

Reynolds number (Re)

DI water1 TiO2

2 TiO2

1 SiO2

2 SiO2

Figure 18 Nusselt number versus Reynolds number for nanofluidswith typical twist tape (119910 = 293)

0

025

05

075

1

125

15

0 500 1000 1500 2000

Reynolds number (Re)

DI water

Fric

tion

fact

or (f

)

1 TiO2

2 TiO21 SiO2

2 SiO2

Figure 19 Nusselt number versus Reynolds number for nanofluidswith typical twist tape (119910 = 293)

0

20

40

60

80

0 20 40 60 80

Nus

selt

num

ber (

expe

rimen

tal)

Nusselt number (predicted)

DI water1 TiO2 2 TiO2

1 SiO2

2 SiO2

+6

minus6

Figure 20 Comparison of experimental and predicted Nusseltnumber with typical twist tape

10 Journal of Nanomaterials

0

025

05

075

1

125

15

0 025 05 075 1 125 15

Fric

tion

fact

or (e

xper

imen

tal)

Friction factor (predicted)

DI water1 TiO2

2 TiO2

1 SiO2

2 SiO2

+8

+8

Figure 21 Comparison of experimental and predicted frictionfactor with typical twist tape

30

35

40

45

50

55

60

65

0 500 1000 1500 2000

Nus

selt

num

ber (

Nu)

Reynolds number (Re)

QCT (2 SiO2)PCT (2 SiO2)VCT (2 SiO2)

TT (2 SiO2)TT (DI water)

Figure 22 Nusselt number versus Reynolds number for typical andconic cut twist tapes

0

03

06

09

12

15

18

0 500 1000 1500 2000

Reynolds number (Re)

QCT (2 SiO2)PCT (2 SiO2)VCT (2 SiO2)

TT (DI water)TT (DI water)

Fric

tion

fact

or (f

)

Figure 23 Friction factor versus Reynolds number for typical andconic cut twist tapes

0

20

40

60

80

0 20 40 60 80

Nus

selt

num

ber (

expe

rimen

tal)

Nusselt number (predicted)

+8

minus8

QCT (2 SiO2)PCT ( SiO2)VCT (2 SiO2)

TT (2 SiO2)TT (DI water)

Figure 24 Comparison of experimental and predicted Nusseltnumber for typical and conic cut twist tapes

Journal of Nanomaterials 11

0

05

1

15

2

0 05 1 15 2

Fric

tion

fact

or (e

xper

imen

tal)

Friction factor (predicted)

QCT (2 SiO2)PCT (2 SiO2)VCT (2 SiO2)

TT (2 SiO2)TT (DI water)

+10

minus10

Figure 25 Comparison of experimental and predicted frictionfactor for typical and conic cut twist tapes

For quadrant cut twisted tape

Nu = 538Pr04Re0226 (1 + 119908

119882)

00387

(1 +119889119890

119882)

minus0187

sdot (1 + 120601)0027

(23)

119891 = 6913Reminus071 (1 + 119908

119882)

0127

(1 +119889119890

119882)

minus016

sdot (1 + 120601)031

(24)

65 Thermal Performance of Twist Tapes The performanceanalysis of typical and conic cut twisted tape inserts in lami-nar flow of SiO

2nanofluid was accomplished by evaluating

thermal performance factor for constant pumping powercondition Thermal performance factor (120578) at constantspumping power is defined as ratio of the convective heattransfer coefficient of the tube with turbulator or enhancingmethod to that of the plain tube The following thermalperformance factor for laminar proposed by [29] is used forperformance analysis

120578 =(NuNu

119900)

(119891119891119900)01666

(25)

where Nu 119891 Nu119900 and 119891

119900are the Nusselt numbers and

friction factors for a duct configuration with and withoutinserts respectively

2

3

4

5

6

0 500 1000 1500 2000

Reynolds number (Re)

QCT (2 SiO2)PCT (2 SiO2)VCT (2 SiO2) TT (2 SiO2)

TT (DI water)

Ther

mal

per

form

ance

fact

or (120578

)

Figure 26 Variation of the thermal performance factor of typicaland conic cut twist tape

Figure 26 shows the variation of thermal performancefactor with Reynolds number for 2 volume concentrationof SiO

2nanofluid The values of thermal performance factor

at all Reynolds were found to be greater than unity for bothtypical and conic cut twisted tape inserts This indicates thattwist tape inserts are feasible in terms of energy saving in lam-inar flow regime It is evident that the thermal performancefactor triangular cut twist tape at constant Reynolds numberis higher than other twist tapes This is due to the strongerturbulenceswirl flow generated by alternative cuts along theedge twist tape The thermal performance factor was foundto be decreasing with increases in Reynolds number Thisis because of the increase in pressure loss as the Reynoldsnumber increases

The experimental results showed that the thermal perfor-mance factor is around 513ndash416 for VCT 498ndash408 for PCT488ndash405 for QCT and 483ndash401 for TT when used with2 SiO

2nanofluid While the thermal performance factor

to be around 475ndash396 for TT with water Therefore theVCT insert shows better thermal performance when usedwith SiO

2nanofluid than other twist tapesThe experimental

results are used to derive the following correlations of thermalperformance factor using least square method of regressionanalysis These correlations are valid for laminar flow (Re lt

1500) of water and 2 volume concentration SiO2for typical

and conic cut twist tapesThe comparisons between the ther-mal performance factor values obtained from experimentaldata and those predicted from the above correlations are

12 Journal of Nanomaterials

3

4

5

6

3 4 5 6

QCT (2 SiO2)PCT (2 SiO2)VCT (2 SiO2) TT (2 SiO2)

TT (DI water)

+6

minus6

Ther

mal

per

form

ance

fact

or (e

xper

imen

tal)

Thermal performance factor (predicted)

Figure 27 Comparison of experimental and predicted thermalperformance for typical and conic cut twist tapes

shown in Figure 27 As shown the predicted data are in goodagreement with the experimental data

For VCT twisted tape

120578 = 5173Reminus0118 (1 + 119908

119882)

2483

(1 +119889119890

119882)

minus0247

sdot (1 + 120601SiO2

)00183

(26)

For PCT twisted tape

120578 = 5173Re00945 (1 + 119908

119882)

3113

(1 +119889119890

119882)

minus0247

sdot (1 + 120601SiO2

)00183

(27)

For QCT twisted tape

120578 = 5173Re0118 (1 + 119908

119882)

349

(1 +119889119890

119882)

minus0247

sdot (1 + 120601SiO2

)00183

(28)

For TT twisted tape with SiO nanofluid

120578 = 791Re0093 (1 + 120601SiO2

)1283

(29)

For TT twisted tape with deionized water

120578 = 791Re0093 (30)

7 Conclusions

Heat transfer friction and thermal performance characteris-tics of SiO

2and TiO

2nanofluids with two concentrations of

1 and 2 by volume in a circular tube fitted with a typicaland conic cut twist tape in the laminar regime have beenexperimentally investigated The main conclusions from thisexperimental study are as follows

(71) SiO2and TiO

2nanofluids of different volume con-

centration in plain tube give good enhancement inNusselt number compared to deionized water Thehigher enhancement inNusselt number is obtained bySiO2nanofluids with volume concentrations of 2

(72) At similar conditions the insertion of typical twisttape causes very significant convective heat transferenhancement in the laminar flow however furtherenhancement is observed by the simultaneous use ofnanofluid with twisted tape compared to the use oftwisted tape or nanofluid alone

(73) The use of nanofluid with the conic cut twist tapeprovides a considerably higher Nusselt number thanthat of nanofluid with the typical twist tape for allReynolds numbers examinedThe triangular cut twisttape offers higher heat transfer rate than the typicaltwist tape and other conic cut configurations

(74) Over the range investigated (Re = 220ndash1500) themaximum thermal performance factor of 513 isfound with the simultaneous use of the triangulartwist tape with SiO

2nanofluid with 2 volume

concentration at Reynolds number of 220(75) The empirical correlations for the Nusselt number

friction factor and the thermal performance factorfor typical and conic cut twist tapes are developedand fitted with the experimental data of water andnanofluids

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

The authors would like to thank the National Universityof Malaysia and the Ministry of Higher Education for thefinancial support (FRGS12013TK07UKM011 and DPP-2013-114) to perform this investigation

References

[1] A Bejan and A D KrausHeat Transfer Handbook John Wileyamp Sons 2003

[2] I Singh and N Diwakar International Journal of AppliedResearch in Mechanical Engineering vol 3 pp 16ndash29 2013

[3] R M Manglik and A E Bergles ldquoHeat transfer and pressuredrop correlations for twisted-tape inserts in isothermal tubes

Journal of Nanomaterials 13

part Imdashlaminar flowsrdquo Journal of Heat Transfer vol 115 no 4pp 881ndash889 1993

[4] S K Saha and D Chakraborty ldquoHeat transfer and pressuredrop characteristics of laminar flow through a circular tubefitted with regularly spaced twisted tape elements with multipletwistsrdquo in Proceedings of the Heat andMass Transfer Conferencepp 313ndash318 Kanpur India 1997

[5] S Al-Fahed L M Chamra and W Chakroun ldquoPressure dropand heat transfer comparison for both microfin tube andtwisted-tape inserts in laminar flowrdquo ExperimentalThermal andFluid Science vol 18 no 4 pp 323ndash333 1998

[6] M S Lokanath and R D Misal ldquoAn experimental study on theperformance of plate heat exchanger and an augmented shelland tube heat exchanger for different types of fluids for marineapplicationsrdquo in Proceedings of the 5th ISHMT-ASME Heat andMass Transfer Conference pp 863ndash868 TataMcGraw-Hill NewDelhi India 2002

[7] P Sivashanmugam and S Suresh ldquoExperimental studies onheat transfer and friction factor characteristics of laminar flowthrough a circular tube fitted with helical screw-tape insertsrdquoApplied Thermal Engineering vol 26 no 16 pp 1990ndash19972006

[8] P Sivashanmugam and S Suresh ldquoExperimental studies onheat transfer and friction factor characteristics of laminar flowthrough a circular tube fitted with regularly spaced helicalscrew-tape insertsrdquo Experimental Thermal and Fluid Sciencevol 31 no 4 pp 301ndash308 2007

[9] S Jaisankar T K Radhakrishnan and K N Sheeba ldquoStudieson heat transfer and friction factor characteristics of ther-mosyphon solar water heating system with helical twistedtapesrdquo Energy vol 34 no 9 pp 1054ndash1064 2009

[10] A V N Kapatkar B D A S Padalkar and C S KasbeldquoExperimental investigation on heat transfer enhancement inlaminar flow in circular tube equipped with different insertsrdquoAMAE International Journal on Manufacturing and MaterialScience vol 1 pp 1ndash6 2011

[11] J Guo A Fan X Zhang and W Liu ldquoA numerical studyon heat transfer and friction factor characteristics of laminarflow in a circular tube fitted with center-cleared twisted taperdquoInternational Journal ofThermal Sciences vol 50 no 7 pp 1263ndash1270 2011

[12] K Wongcharee and S Eiamsa-ard ldquoFriction and heat trans-fer characteristics of laminar swirl flow through the roundtubes inserted with alternate clockwise and counter-clockwisetwisted-tapesrdquo International Communications in Heat andMassTransfer vol 38 no 3 pp 348ndash352 2011

[13] E Z Ibrahim ldquoAugmentation of laminar flow and heat transferin flat tubes by means of helical screw-tape insertsrdquo EnergyConversion and Management vol 52 no 1 pp 250ndash257 2011

[14] S U S Choi and J A Eastman ldquoEnhancing thermal con-ductivity of fluids with nanoparticlesrdquo in Developments andApplications of Non-Newtonian Flows D A Siguier and HP Wang Eds pp 99ndash105 American Society of MechanicalEngineers New York NY USA 1995

[15] C Y Tsai H T Chien P P Ding B Chan T Y Luh and PH Chen ldquoEffect of structural character of gold nanoparticles innanofluid on heat pipe thermal performancerdquoMaterials Lettersvol 58 no 9 pp 1461ndash1465 2004

[16] M-S Liu M C-C Lin C Y Tsai and C-C Wang ldquoEnhance-ment of thermal conductivity with Cu for nanofluids using

chemical reduction methodrdquo International Journal of Heat andMass Transfer vol 49 no 17-18 pp 3028ndash3033 2006

[17] E Tamjid andBHGuenther ldquoRheology and colloidal structureof silver nanoparticles dispersed in diethylene glycolrdquo PowderTechnology vol 197 no 1-2 pp 49ndash53 2010

[18] SM SMurshed K C Leong and C Yang ldquoEnhanced thermalconductivity of TiO

2water based nanofluidsrdquo International

Journal of Thermal Sciences vol 44 no 4 pp 367ndash373 2005[19] H Zhu C Zhang S Liu Y Tang and Y Yin ldquoEffects of

nanoparticle clustering and alignment on thermal conductiv-ities of Fe

3O4aqueous nanofluidsrdquo Applied Physics Letters vol

89 Article ID 023123 2006[20] J A Eastman U S Choi S Li L J Thompson and S Lee

ldquoEnhanced thermal conductivity through the development ofnanofluidsrdquoMRS Proceedings vol 457 1996

[21] M EMeibodi M Vafaie-Sefti AM Rashidi A Amrollahi MTabasi and H S Kalal ldquoSimple model for thermal conductivityof nanofluids using resistance model approachrdquo InternationalCommunications in Heat and Mass Transfer vol 37 no 5 pp555ndash559 2010

[22] G Pathipakka and P Sivashanmugam ldquoHeat transfer behaviourof nanofluids in a uniformly heated circular tube fittedwith heli-cal inserts in laminar flowrdquo Superlattices and Microstructuresvol 47 no 2 pp 349ndash360 2010

[23] K Wongcharee and S Eiamsa-ard ldquoEnhancement of heattransfer using CuOwater nanofluid and twisted tape withalternate axisrdquo International Communications in Heat and MassTransfer vol 38 no 6 pp 742ndash748 2011

[24] S Suresh K P Venkitaraj and P Selvakumar ldquoComparativestudy on thermal performance of helical screw tape inserts inlaminar flow using Al

2O3water and CuOwater nanofluidsrdquo

Superlattices and Microstructures vol 49 no 6 pp 608ndash6222011

[25] S D Salman A A H Kadhum M S Takriff and A BMohamad ldquoHeat transfer enhancement of laminar nanofluidsflow in a circular tube fitted with parabolic-cut twisted tapeinsertsrdquo The Scientific World Journal vol 2014 Article ID543231 7 pages 2014

[26] S D Salman A A H Kadhum M S Takriff and A BMohamad ldquoCFD simulation of heat transfer and friction factoraugmentation in a circular tube fitted with elliptic-cut twistedtape insertsrdquo Mathematical Problems in Engineering vol 2013Article ID 163839 7 pages 2013

[27] S D Salman A A H Kadhum M S Takriff and A BMohamad ldquoCFD analysis of Heat transfer and friction factorcharacteristics in a circular tube fitted with Quadrant-cuttwisted tape insertsrdquoMathematical Problems in Engineering vol2013 Article ID 273764 8 pages 2013

[28] F P Incropera D P Dewitt T L Bergman and A S LavineFundamentals of Heat and Mass Transfer John Wiley amp Sons2007

[29] H Usui Y Sano K Iwashita and A Isozaki ldquoEnhancement ofheat transfer by a combination of internally grooved rough tubeand twisted taperdquo International Chemical Engineering vol 26no 1 pp 97ndash104 1986

[30] J P Holman Experimental Methods for Engineers McGraw-Hill New York NY USA 2011

[31] R K Shah and A L London Laminar Flow Forced Convectionin Ducts Academic Press New York NY USA 1978

14 Journal of Nanomaterials

[32] P KNagarajan andP Sivashanmugam ldquoCFD simulation of heattransfer augmentation in a circular tube fitted with right-lefthelical inserts with spacerrdquo International Journal of ChemicalEngineering Research vol 1 pp 1ndash11 2009

[33] P Keblinski S R Phillpot S U S Choi and J A EastmanldquoMechanisms of heat flow in suspensions of nano-sized particles(nanofluids)rdquo International Journal of Heat and Mass Transfervol 45 no 4 pp 855ndash863 2002

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

10 Journal of Nanomaterials

0

025

05

075

1

125

15

0 025 05 075 1 125 15

Fric

tion

fact

or (e

xper

imen

tal)

Friction factor (predicted)

DI water1 TiO2

2 TiO2

1 SiO2

2 SiO2

+8

+8

Figure 21 Comparison of experimental and predicted frictionfactor with typical twist tape

30

35

40

45

50

55

60

65

0 500 1000 1500 2000

Nus

selt

num

ber (

Nu)

Reynolds number (Re)

QCT (2 SiO2)PCT (2 SiO2)VCT (2 SiO2)

TT (2 SiO2)TT (DI water)

Figure 22 Nusselt number versus Reynolds number for typical andconic cut twist tapes

0

03

06

09

12

15

18

0 500 1000 1500 2000

Reynolds number (Re)

QCT (2 SiO2)PCT (2 SiO2)VCT (2 SiO2)

TT (DI water)TT (DI water)

Fric

tion

fact

or (f

)

Figure 23 Friction factor versus Reynolds number for typical andconic cut twist tapes

0

20

40

60

80

0 20 40 60 80

Nus

selt

num

ber (

expe

rimen

tal)

Nusselt number (predicted)

+8

minus8

QCT (2 SiO2)PCT ( SiO2)VCT (2 SiO2)

TT (2 SiO2)TT (DI water)

Figure 24 Comparison of experimental and predicted Nusseltnumber for typical and conic cut twist tapes

Journal of Nanomaterials 11

0

05

1

15

2

0 05 1 15 2

Fric

tion

fact

or (e

xper

imen

tal)

Friction factor (predicted)

QCT (2 SiO2)PCT (2 SiO2)VCT (2 SiO2)

TT (2 SiO2)TT (DI water)

+10

minus10

Figure 25 Comparison of experimental and predicted frictionfactor for typical and conic cut twist tapes

For quadrant cut twisted tape

Nu = 538Pr04Re0226 (1 + 119908

119882)

00387

(1 +119889119890

119882)

minus0187

sdot (1 + 120601)0027

(23)

119891 = 6913Reminus071 (1 + 119908

119882)

0127

(1 +119889119890

119882)

minus016

sdot (1 + 120601)031

(24)

65 Thermal Performance of Twist Tapes The performanceanalysis of typical and conic cut twisted tape inserts in lami-nar flow of SiO

2nanofluid was accomplished by evaluating

thermal performance factor for constant pumping powercondition Thermal performance factor (120578) at constantspumping power is defined as ratio of the convective heattransfer coefficient of the tube with turbulator or enhancingmethod to that of the plain tube The following thermalperformance factor for laminar proposed by [29] is used forperformance analysis

120578 =(NuNu

119900)

(119891119891119900)01666

(25)

where Nu 119891 Nu119900 and 119891

119900are the Nusselt numbers and

friction factors for a duct configuration with and withoutinserts respectively

2

3

4

5

6

0 500 1000 1500 2000

Reynolds number (Re)

QCT (2 SiO2)PCT (2 SiO2)VCT (2 SiO2) TT (2 SiO2)

TT (DI water)

Ther

mal

per

form

ance

fact

or (120578

)

Figure 26 Variation of the thermal performance factor of typicaland conic cut twist tape

Figure 26 shows the variation of thermal performancefactor with Reynolds number for 2 volume concentrationof SiO

2nanofluid The values of thermal performance factor

at all Reynolds were found to be greater than unity for bothtypical and conic cut twisted tape inserts This indicates thattwist tape inserts are feasible in terms of energy saving in lam-inar flow regime It is evident that the thermal performancefactor triangular cut twist tape at constant Reynolds numberis higher than other twist tapes This is due to the strongerturbulenceswirl flow generated by alternative cuts along theedge twist tape The thermal performance factor was foundto be decreasing with increases in Reynolds number Thisis because of the increase in pressure loss as the Reynoldsnumber increases

The experimental results showed that the thermal perfor-mance factor is around 513ndash416 for VCT 498ndash408 for PCT488ndash405 for QCT and 483ndash401 for TT when used with2 SiO

2nanofluid While the thermal performance factor

to be around 475ndash396 for TT with water Therefore theVCT insert shows better thermal performance when usedwith SiO

2nanofluid than other twist tapesThe experimental

results are used to derive the following correlations of thermalperformance factor using least square method of regressionanalysis These correlations are valid for laminar flow (Re lt

1500) of water and 2 volume concentration SiO2for typical

and conic cut twist tapesThe comparisons between the ther-mal performance factor values obtained from experimentaldata and those predicted from the above correlations are

12 Journal of Nanomaterials

3

4

5

6

3 4 5 6

QCT (2 SiO2)PCT (2 SiO2)VCT (2 SiO2) TT (2 SiO2)

TT (DI water)

+6

minus6

Ther

mal

per

form

ance

fact

or (e

xper

imen

tal)

Thermal performance factor (predicted)

Figure 27 Comparison of experimental and predicted thermalperformance for typical and conic cut twist tapes

shown in Figure 27 As shown the predicted data are in goodagreement with the experimental data

For VCT twisted tape

120578 = 5173Reminus0118 (1 + 119908

119882)

2483

(1 +119889119890

119882)

minus0247

sdot (1 + 120601SiO2

)00183

(26)

For PCT twisted tape

120578 = 5173Re00945 (1 + 119908

119882)

3113

(1 +119889119890

119882)

minus0247

sdot (1 + 120601SiO2

)00183

(27)

For QCT twisted tape

120578 = 5173Re0118 (1 + 119908

119882)

349

(1 +119889119890

119882)

minus0247

sdot (1 + 120601SiO2

)00183

(28)

For TT twisted tape with SiO nanofluid

120578 = 791Re0093 (1 + 120601SiO2

)1283

(29)

For TT twisted tape with deionized water

120578 = 791Re0093 (30)

7 Conclusions

Heat transfer friction and thermal performance characteris-tics of SiO

2and TiO

2nanofluids with two concentrations of

1 and 2 by volume in a circular tube fitted with a typicaland conic cut twist tape in the laminar regime have beenexperimentally investigated The main conclusions from thisexperimental study are as follows

(71) SiO2and TiO

2nanofluids of different volume con-

centration in plain tube give good enhancement inNusselt number compared to deionized water Thehigher enhancement inNusselt number is obtained bySiO2nanofluids with volume concentrations of 2

(72) At similar conditions the insertion of typical twisttape causes very significant convective heat transferenhancement in the laminar flow however furtherenhancement is observed by the simultaneous use ofnanofluid with twisted tape compared to the use oftwisted tape or nanofluid alone

(73) The use of nanofluid with the conic cut twist tapeprovides a considerably higher Nusselt number thanthat of nanofluid with the typical twist tape for allReynolds numbers examinedThe triangular cut twisttape offers higher heat transfer rate than the typicaltwist tape and other conic cut configurations

(74) Over the range investigated (Re = 220ndash1500) themaximum thermal performance factor of 513 isfound with the simultaneous use of the triangulartwist tape with SiO

2nanofluid with 2 volume

concentration at Reynolds number of 220(75) The empirical correlations for the Nusselt number

friction factor and the thermal performance factorfor typical and conic cut twist tapes are developedand fitted with the experimental data of water andnanofluids

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

The authors would like to thank the National Universityof Malaysia and the Ministry of Higher Education for thefinancial support (FRGS12013TK07UKM011 and DPP-2013-114) to perform this investigation

References

[1] A Bejan and A D KrausHeat Transfer Handbook John Wileyamp Sons 2003

[2] I Singh and N Diwakar International Journal of AppliedResearch in Mechanical Engineering vol 3 pp 16ndash29 2013

[3] R M Manglik and A E Bergles ldquoHeat transfer and pressuredrop correlations for twisted-tape inserts in isothermal tubes

Journal of Nanomaterials 13

part Imdashlaminar flowsrdquo Journal of Heat Transfer vol 115 no 4pp 881ndash889 1993

[4] S K Saha and D Chakraborty ldquoHeat transfer and pressuredrop characteristics of laminar flow through a circular tubefitted with regularly spaced twisted tape elements with multipletwistsrdquo in Proceedings of the Heat andMass Transfer Conferencepp 313ndash318 Kanpur India 1997

[5] S Al-Fahed L M Chamra and W Chakroun ldquoPressure dropand heat transfer comparison for both microfin tube andtwisted-tape inserts in laminar flowrdquo ExperimentalThermal andFluid Science vol 18 no 4 pp 323ndash333 1998

[6] M S Lokanath and R D Misal ldquoAn experimental study on theperformance of plate heat exchanger and an augmented shelland tube heat exchanger for different types of fluids for marineapplicationsrdquo in Proceedings of the 5th ISHMT-ASME Heat andMass Transfer Conference pp 863ndash868 TataMcGraw-Hill NewDelhi India 2002

[7] P Sivashanmugam and S Suresh ldquoExperimental studies onheat transfer and friction factor characteristics of laminar flowthrough a circular tube fitted with helical screw-tape insertsrdquoApplied Thermal Engineering vol 26 no 16 pp 1990ndash19972006

[8] P Sivashanmugam and S Suresh ldquoExperimental studies onheat transfer and friction factor characteristics of laminar flowthrough a circular tube fitted with regularly spaced helicalscrew-tape insertsrdquo Experimental Thermal and Fluid Sciencevol 31 no 4 pp 301ndash308 2007

[9] S Jaisankar T K Radhakrishnan and K N Sheeba ldquoStudieson heat transfer and friction factor characteristics of ther-mosyphon solar water heating system with helical twistedtapesrdquo Energy vol 34 no 9 pp 1054ndash1064 2009

[10] A V N Kapatkar B D A S Padalkar and C S KasbeldquoExperimental investigation on heat transfer enhancement inlaminar flow in circular tube equipped with different insertsrdquoAMAE International Journal on Manufacturing and MaterialScience vol 1 pp 1ndash6 2011

[11] J Guo A Fan X Zhang and W Liu ldquoA numerical studyon heat transfer and friction factor characteristics of laminarflow in a circular tube fitted with center-cleared twisted taperdquoInternational Journal ofThermal Sciences vol 50 no 7 pp 1263ndash1270 2011

[12] K Wongcharee and S Eiamsa-ard ldquoFriction and heat trans-fer characteristics of laminar swirl flow through the roundtubes inserted with alternate clockwise and counter-clockwisetwisted-tapesrdquo International Communications in Heat andMassTransfer vol 38 no 3 pp 348ndash352 2011

[13] E Z Ibrahim ldquoAugmentation of laminar flow and heat transferin flat tubes by means of helical screw-tape insertsrdquo EnergyConversion and Management vol 52 no 1 pp 250ndash257 2011

[14] S U S Choi and J A Eastman ldquoEnhancing thermal con-ductivity of fluids with nanoparticlesrdquo in Developments andApplications of Non-Newtonian Flows D A Siguier and HP Wang Eds pp 99ndash105 American Society of MechanicalEngineers New York NY USA 1995

[15] C Y Tsai H T Chien P P Ding B Chan T Y Luh and PH Chen ldquoEffect of structural character of gold nanoparticles innanofluid on heat pipe thermal performancerdquoMaterials Lettersvol 58 no 9 pp 1461ndash1465 2004

[16] M-S Liu M C-C Lin C Y Tsai and C-C Wang ldquoEnhance-ment of thermal conductivity with Cu for nanofluids using

chemical reduction methodrdquo International Journal of Heat andMass Transfer vol 49 no 17-18 pp 3028ndash3033 2006

[17] E Tamjid andBHGuenther ldquoRheology and colloidal structureof silver nanoparticles dispersed in diethylene glycolrdquo PowderTechnology vol 197 no 1-2 pp 49ndash53 2010

[18] SM SMurshed K C Leong and C Yang ldquoEnhanced thermalconductivity of TiO

2water based nanofluidsrdquo International

Journal of Thermal Sciences vol 44 no 4 pp 367ndash373 2005[19] H Zhu C Zhang S Liu Y Tang and Y Yin ldquoEffects of

nanoparticle clustering and alignment on thermal conductiv-ities of Fe

3O4aqueous nanofluidsrdquo Applied Physics Letters vol

89 Article ID 023123 2006[20] J A Eastman U S Choi S Li L J Thompson and S Lee

ldquoEnhanced thermal conductivity through the development ofnanofluidsrdquoMRS Proceedings vol 457 1996

[21] M EMeibodi M Vafaie-Sefti AM Rashidi A Amrollahi MTabasi and H S Kalal ldquoSimple model for thermal conductivityof nanofluids using resistance model approachrdquo InternationalCommunications in Heat and Mass Transfer vol 37 no 5 pp555ndash559 2010

[22] G Pathipakka and P Sivashanmugam ldquoHeat transfer behaviourof nanofluids in a uniformly heated circular tube fittedwith heli-cal inserts in laminar flowrdquo Superlattices and Microstructuresvol 47 no 2 pp 349ndash360 2010

[23] K Wongcharee and S Eiamsa-ard ldquoEnhancement of heattransfer using CuOwater nanofluid and twisted tape withalternate axisrdquo International Communications in Heat and MassTransfer vol 38 no 6 pp 742ndash748 2011

[24] S Suresh K P Venkitaraj and P Selvakumar ldquoComparativestudy on thermal performance of helical screw tape inserts inlaminar flow using Al

2O3water and CuOwater nanofluidsrdquo

Superlattices and Microstructures vol 49 no 6 pp 608ndash6222011

[25] S D Salman A A H Kadhum M S Takriff and A BMohamad ldquoHeat transfer enhancement of laminar nanofluidsflow in a circular tube fitted with parabolic-cut twisted tapeinsertsrdquo The Scientific World Journal vol 2014 Article ID543231 7 pages 2014

[26] S D Salman A A H Kadhum M S Takriff and A BMohamad ldquoCFD simulation of heat transfer and friction factoraugmentation in a circular tube fitted with elliptic-cut twistedtape insertsrdquo Mathematical Problems in Engineering vol 2013Article ID 163839 7 pages 2013

[27] S D Salman A A H Kadhum M S Takriff and A BMohamad ldquoCFD analysis of Heat transfer and friction factorcharacteristics in a circular tube fitted with Quadrant-cuttwisted tape insertsrdquoMathematical Problems in Engineering vol2013 Article ID 273764 8 pages 2013

[28] F P Incropera D P Dewitt T L Bergman and A S LavineFundamentals of Heat and Mass Transfer John Wiley amp Sons2007

[29] H Usui Y Sano K Iwashita and A Isozaki ldquoEnhancement ofheat transfer by a combination of internally grooved rough tubeand twisted taperdquo International Chemical Engineering vol 26no 1 pp 97ndash104 1986

[30] J P Holman Experimental Methods for Engineers McGraw-Hill New York NY USA 2011

[31] R K Shah and A L London Laminar Flow Forced Convectionin Ducts Academic Press New York NY USA 1978

14 Journal of Nanomaterials

[32] P KNagarajan andP Sivashanmugam ldquoCFD simulation of heattransfer augmentation in a circular tube fitted with right-lefthelical inserts with spacerrdquo International Journal of ChemicalEngineering Research vol 1 pp 1ndash11 2009

[33] P Keblinski S R Phillpot S U S Choi and J A EastmanldquoMechanisms of heat flow in suspensions of nano-sized particles(nanofluids)rdquo International Journal of Heat and Mass Transfervol 45 no 4 pp 855ndash863 2002

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

Journal of Nanomaterials 11

0

05

1

15

2

0 05 1 15 2

Fric

tion

fact

or (e

xper

imen

tal)

Friction factor (predicted)

QCT (2 SiO2)PCT (2 SiO2)VCT (2 SiO2)

TT (2 SiO2)TT (DI water)

+10

minus10

Figure 25 Comparison of experimental and predicted frictionfactor for typical and conic cut twist tapes

For quadrant cut twisted tape

Nu = 538Pr04Re0226 (1 + 119908

119882)

00387

(1 +119889119890

119882)

minus0187

sdot (1 + 120601)0027

(23)

119891 = 6913Reminus071 (1 + 119908

119882)

0127

(1 +119889119890

119882)

minus016

sdot (1 + 120601)031

(24)

65 Thermal Performance of Twist Tapes The performanceanalysis of typical and conic cut twisted tape inserts in lami-nar flow of SiO

2nanofluid was accomplished by evaluating

thermal performance factor for constant pumping powercondition Thermal performance factor (120578) at constantspumping power is defined as ratio of the convective heattransfer coefficient of the tube with turbulator or enhancingmethod to that of the plain tube The following thermalperformance factor for laminar proposed by [29] is used forperformance analysis

120578 =(NuNu

119900)

(119891119891119900)01666

(25)

where Nu 119891 Nu119900 and 119891

119900are the Nusselt numbers and

friction factors for a duct configuration with and withoutinserts respectively

2

3

4

5

6

0 500 1000 1500 2000

Reynolds number (Re)

QCT (2 SiO2)PCT (2 SiO2)VCT (2 SiO2) TT (2 SiO2)

TT (DI water)

Ther

mal

per

form

ance

fact

or (120578

)

Figure 26 Variation of the thermal performance factor of typicaland conic cut twist tape

Figure 26 shows the variation of thermal performancefactor with Reynolds number for 2 volume concentrationof SiO

2nanofluid The values of thermal performance factor

at all Reynolds were found to be greater than unity for bothtypical and conic cut twisted tape inserts This indicates thattwist tape inserts are feasible in terms of energy saving in lam-inar flow regime It is evident that the thermal performancefactor triangular cut twist tape at constant Reynolds numberis higher than other twist tapes This is due to the strongerturbulenceswirl flow generated by alternative cuts along theedge twist tape The thermal performance factor was foundto be decreasing with increases in Reynolds number Thisis because of the increase in pressure loss as the Reynoldsnumber increases

The experimental results showed that the thermal perfor-mance factor is around 513ndash416 for VCT 498ndash408 for PCT488ndash405 for QCT and 483ndash401 for TT when used with2 SiO

2nanofluid While the thermal performance factor

to be around 475ndash396 for TT with water Therefore theVCT insert shows better thermal performance when usedwith SiO

2nanofluid than other twist tapesThe experimental

results are used to derive the following correlations of thermalperformance factor using least square method of regressionanalysis These correlations are valid for laminar flow (Re lt

1500) of water and 2 volume concentration SiO2for typical

and conic cut twist tapesThe comparisons between the ther-mal performance factor values obtained from experimentaldata and those predicted from the above correlations are

12 Journal of Nanomaterials

3

4

5

6

3 4 5 6

QCT (2 SiO2)PCT (2 SiO2)VCT (2 SiO2) TT (2 SiO2)

TT (DI water)

+6

minus6

Ther

mal

per

form

ance

fact

or (e

xper

imen

tal)

Thermal performance factor (predicted)

Figure 27 Comparison of experimental and predicted thermalperformance for typical and conic cut twist tapes

shown in Figure 27 As shown the predicted data are in goodagreement with the experimental data

For VCT twisted tape

120578 = 5173Reminus0118 (1 + 119908

119882)

2483

(1 +119889119890

119882)

minus0247

sdot (1 + 120601SiO2

)00183

(26)

For PCT twisted tape

120578 = 5173Re00945 (1 + 119908

119882)

3113

(1 +119889119890

119882)

minus0247

sdot (1 + 120601SiO2

)00183

(27)

For QCT twisted tape

120578 = 5173Re0118 (1 + 119908

119882)

349

(1 +119889119890

119882)

minus0247

sdot (1 + 120601SiO2

)00183

(28)

For TT twisted tape with SiO nanofluid

120578 = 791Re0093 (1 + 120601SiO2

)1283

(29)

For TT twisted tape with deionized water

120578 = 791Re0093 (30)

7 Conclusions

Heat transfer friction and thermal performance characteris-tics of SiO

2and TiO

2nanofluids with two concentrations of

1 and 2 by volume in a circular tube fitted with a typicaland conic cut twist tape in the laminar regime have beenexperimentally investigated The main conclusions from thisexperimental study are as follows

(71) SiO2and TiO

2nanofluids of different volume con-

centration in plain tube give good enhancement inNusselt number compared to deionized water Thehigher enhancement inNusselt number is obtained bySiO2nanofluids with volume concentrations of 2

(72) At similar conditions the insertion of typical twisttape causes very significant convective heat transferenhancement in the laminar flow however furtherenhancement is observed by the simultaneous use ofnanofluid with twisted tape compared to the use oftwisted tape or nanofluid alone

(73) The use of nanofluid with the conic cut twist tapeprovides a considerably higher Nusselt number thanthat of nanofluid with the typical twist tape for allReynolds numbers examinedThe triangular cut twisttape offers higher heat transfer rate than the typicaltwist tape and other conic cut configurations

(74) Over the range investigated (Re = 220ndash1500) themaximum thermal performance factor of 513 isfound with the simultaneous use of the triangulartwist tape with SiO

2nanofluid with 2 volume

concentration at Reynolds number of 220(75) The empirical correlations for the Nusselt number

friction factor and the thermal performance factorfor typical and conic cut twist tapes are developedand fitted with the experimental data of water andnanofluids

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

The authors would like to thank the National Universityof Malaysia and the Ministry of Higher Education for thefinancial support (FRGS12013TK07UKM011 and DPP-2013-114) to perform this investigation

References

[1] A Bejan and A D KrausHeat Transfer Handbook John Wileyamp Sons 2003

[2] I Singh and N Diwakar International Journal of AppliedResearch in Mechanical Engineering vol 3 pp 16ndash29 2013

[3] R M Manglik and A E Bergles ldquoHeat transfer and pressuredrop correlations for twisted-tape inserts in isothermal tubes

Journal of Nanomaterials 13

part Imdashlaminar flowsrdquo Journal of Heat Transfer vol 115 no 4pp 881ndash889 1993

[4] S K Saha and D Chakraborty ldquoHeat transfer and pressuredrop characteristics of laminar flow through a circular tubefitted with regularly spaced twisted tape elements with multipletwistsrdquo in Proceedings of the Heat andMass Transfer Conferencepp 313ndash318 Kanpur India 1997

[5] S Al-Fahed L M Chamra and W Chakroun ldquoPressure dropand heat transfer comparison for both microfin tube andtwisted-tape inserts in laminar flowrdquo ExperimentalThermal andFluid Science vol 18 no 4 pp 323ndash333 1998

[6] M S Lokanath and R D Misal ldquoAn experimental study on theperformance of plate heat exchanger and an augmented shelland tube heat exchanger for different types of fluids for marineapplicationsrdquo in Proceedings of the 5th ISHMT-ASME Heat andMass Transfer Conference pp 863ndash868 TataMcGraw-Hill NewDelhi India 2002

[7] P Sivashanmugam and S Suresh ldquoExperimental studies onheat transfer and friction factor characteristics of laminar flowthrough a circular tube fitted with helical screw-tape insertsrdquoApplied Thermal Engineering vol 26 no 16 pp 1990ndash19972006

[8] P Sivashanmugam and S Suresh ldquoExperimental studies onheat transfer and friction factor characteristics of laminar flowthrough a circular tube fitted with regularly spaced helicalscrew-tape insertsrdquo Experimental Thermal and Fluid Sciencevol 31 no 4 pp 301ndash308 2007

[9] S Jaisankar T K Radhakrishnan and K N Sheeba ldquoStudieson heat transfer and friction factor characteristics of ther-mosyphon solar water heating system with helical twistedtapesrdquo Energy vol 34 no 9 pp 1054ndash1064 2009

[10] A V N Kapatkar B D A S Padalkar and C S KasbeldquoExperimental investigation on heat transfer enhancement inlaminar flow in circular tube equipped with different insertsrdquoAMAE International Journal on Manufacturing and MaterialScience vol 1 pp 1ndash6 2011

[11] J Guo A Fan X Zhang and W Liu ldquoA numerical studyon heat transfer and friction factor characteristics of laminarflow in a circular tube fitted with center-cleared twisted taperdquoInternational Journal ofThermal Sciences vol 50 no 7 pp 1263ndash1270 2011

[12] K Wongcharee and S Eiamsa-ard ldquoFriction and heat trans-fer characteristics of laminar swirl flow through the roundtubes inserted with alternate clockwise and counter-clockwisetwisted-tapesrdquo International Communications in Heat andMassTransfer vol 38 no 3 pp 348ndash352 2011

[13] E Z Ibrahim ldquoAugmentation of laminar flow and heat transferin flat tubes by means of helical screw-tape insertsrdquo EnergyConversion and Management vol 52 no 1 pp 250ndash257 2011

[14] S U S Choi and J A Eastman ldquoEnhancing thermal con-ductivity of fluids with nanoparticlesrdquo in Developments andApplications of Non-Newtonian Flows D A Siguier and HP Wang Eds pp 99ndash105 American Society of MechanicalEngineers New York NY USA 1995

[15] C Y Tsai H T Chien P P Ding B Chan T Y Luh and PH Chen ldquoEffect of structural character of gold nanoparticles innanofluid on heat pipe thermal performancerdquoMaterials Lettersvol 58 no 9 pp 1461ndash1465 2004

[16] M-S Liu M C-C Lin C Y Tsai and C-C Wang ldquoEnhance-ment of thermal conductivity with Cu for nanofluids using

chemical reduction methodrdquo International Journal of Heat andMass Transfer vol 49 no 17-18 pp 3028ndash3033 2006

[17] E Tamjid andBHGuenther ldquoRheology and colloidal structureof silver nanoparticles dispersed in diethylene glycolrdquo PowderTechnology vol 197 no 1-2 pp 49ndash53 2010

[18] SM SMurshed K C Leong and C Yang ldquoEnhanced thermalconductivity of TiO

2water based nanofluidsrdquo International

Journal of Thermal Sciences vol 44 no 4 pp 367ndash373 2005[19] H Zhu C Zhang S Liu Y Tang and Y Yin ldquoEffects of

nanoparticle clustering and alignment on thermal conductiv-ities of Fe

3O4aqueous nanofluidsrdquo Applied Physics Letters vol

89 Article ID 023123 2006[20] J A Eastman U S Choi S Li L J Thompson and S Lee

ldquoEnhanced thermal conductivity through the development ofnanofluidsrdquoMRS Proceedings vol 457 1996

[21] M EMeibodi M Vafaie-Sefti AM Rashidi A Amrollahi MTabasi and H S Kalal ldquoSimple model for thermal conductivityof nanofluids using resistance model approachrdquo InternationalCommunications in Heat and Mass Transfer vol 37 no 5 pp555ndash559 2010

[22] G Pathipakka and P Sivashanmugam ldquoHeat transfer behaviourof nanofluids in a uniformly heated circular tube fittedwith heli-cal inserts in laminar flowrdquo Superlattices and Microstructuresvol 47 no 2 pp 349ndash360 2010

[23] K Wongcharee and S Eiamsa-ard ldquoEnhancement of heattransfer using CuOwater nanofluid and twisted tape withalternate axisrdquo International Communications in Heat and MassTransfer vol 38 no 6 pp 742ndash748 2011

[24] S Suresh K P Venkitaraj and P Selvakumar ldquoComparativestudy on thermal performance of helical screw tape inserts inlaminar flow using Al

2O3water and CuOwater nanofluidsrdquo

Superlattices and Microstructures vol 49 no 6 pp 608ndash6222011

[25] S D Salman A A H Kadhum M S Takriff and A BMohamad ldquoHeat transfer enhancement of laminar nanofluidsflow in a circular tube fitted with parabolic-cut twisted tapeinsertsrdquo The Scientific World Journal vol 2014 Article ID543231 7 pages 2014

[26] S D Salman A A H Kadhum M S Takriff and A BMohamad ldquoCFD simulation of heat transfer and friction factoraugmentation in a circular tube fitted with elliptic-cut twistedtape insertsrdquo Mathematical Problems in Engineering vol 2013Article ID 163839 7 pages 2013

[27] S D Salman A A H Kadhum M S Takriff and A BMohamad ldquoCFD analysis of Heat transfer and friction factorcharacteristics in a circular tube fitted with Quadrant-cuttwisted tape insertsrdquoMathematical Problems in Engineering vol2013 Article ID 273764 8 pages 2013

[28] F P Incropera D P Dewitt T L Bergman and A S LavineFundamentals of Heat and Mass Transfer John Wiley amp Sons2007

[29] H Usui Y Sano K Iwashita and A Isozaki ldquoEnhancement ofheat transfer by a combination of internally grooved rough tubeand twisted taperdquo International Chemical Engineering vol 26no 1 pp 97ndash104 1986

[30] J P Holman Experimental Methods for Engineers McGraw-Hill New York NY USA 2011

[31] R K Shah and A L London Laminar Flow Forced Convectionin Ducts Academic Press New York NY USA 1978

14 Journal of Nanomaterials

[32] P KNagarajan andP Sivashanmugam ldquoCFD simulation of heattransfer augmentation in a circular tube fitted with right-lefthelical inserts with spacerrdquo International Journal of ChemicalEngineering Research vol 1 pp 1ndash11 2009

[33] P Keblinski S R Phillpot S U S Choi and J A EastmanldquoMechanisms of heat flow in suspensions of nano-sized particles(nanofluids)rdquo International Journal of Heat and Mass Transfervol 45 no 4 pp 855ndash863 2002

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

12 Journal of Nanomaterials

3

4

5

6

3 4 5 6

QCT (2 SiO2)PCT (2 SiO2)VCT (2 SiO2) TT (2 SiO2)

TT (DI water)

+6

minus6

Ther

mal

per

form

ance

fact

or (e

xper

imen

tal)

Thermal performance factor (predicted)

Figure 27 Comparison of experimental and predicted thermalperformance for typical and conic cut twist tapes

shown in Figure 27 As shown the predicted data are in goodagreement with the experimental data

For VCT twisted tape

120578 = 5173Reminus0118 (1 + 119908

119882)

2483

(1 +119889119890

119882)

minus0247

sdot (1 + 120601SiO2

)00183

(26)

For PCT twisted tape

120578 = 5173Re00945 (1 + 119908

119882)

3113

(1 +119889119890

119882)

minus0247

sdot (1 + 120601SiO2

)00183

(27)

For QCT twisted tape

120578 = 5173Re0118 (1 + 119908

119882)

349

(1 +119889119890

119882)

minus0247

sdot (1 + 120601SiO2

)00183

(28)

For TT twisted tape with SiO nanofluid

120578 = 791Re0093 (1 + 120601SiO2

)1283

(29)

For TT twisted tape with deionized water

120578 = 791Re0093 (30)

7 Conclusions

Heat transfer friction and thermal performance characteris-tics of SiO

2and TiO

2nanofluids with two concentrations of

1 and 2 by volume in a circular tube fitted with a typicaland conic cut twist tape in the laminar regime have beenexperimentally investigated The main conclusions from thisexperimental study are as follows

(71) SiO2and TiO

2nanofluids of different volume con-

centration in plain tube give good enhancement inNusselt number compared to deionized water Thehigher enhancement inNusselt number is obtained bySiO2nanofluids with volume concentrations of 2

(72) At similar conditions the insertion of typical twisttape causes very significant convective heat transferenhancement in the laminar flow however furtherenhancement is observed by the simultaneous use ofnanofluid with twisted tape compared to the use oftwisted tape or nanofluid alone

(73) The use of nanofluid with the conic cut twist tapeprovides a considerably higher Nusselt number thanthat of nanofluid with the typical twist tape for allReynolds numbers examinedThe triangular cut twisttape offers higher heat transfer rate than the typicaltwist tape and other conic cut configurations

(74) Over the range investigated (Re = 220ndash1500) themaximum thermal performance factor of 513 isfound with the simultaneous use of the triangulartwist tape with SiO

2nanofluid with 2 volume

concentration at Reynolds number of 220(75) The empirical correlations for the Nusselt number

friction factor and the thermal performance factorfor typical and conic cut twist tapes are developedand fitted with the experimental data of water andnanofluids

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

The authors would like to thank the National Universityof Malaysia and the Ministry of Higher Education for thefinancial support (FRGS12013TK07UKM011 and DPP-2013-114) to perform this investigation

References

[1] A Bejan and A D KrausHeat Transfer Handbook John Wileyamp Sons 2003

[2] I Singh and N Diwakar International Journal of AppliedResearch in Mechanical Engineering vol 3 pp 16ndash29 2013

[3] R M Manglik and A E Bergles ldquoHeat transfer and pressuredrop correlations for twisted-tape inserts in isothermal tubes

Journal of Nanomaterials 13

part Imdashlaminar flowsrdquo Journal of Heat Transfer vol 115 no 4pp 881ndash889 1993

[4] S K Saha and D Chakraborty ldquoHeat transfer and pressuredrop characteristics of laminar flow through a circular tubefitted with regularly spaced twisted tape elements with multipletwistsrdquo in Proceedings of the Heat andMass Transfer Conferencepp 313ndash318 Kanpur India 1997

[5] S Al-Fahed L M Chamra and W Chakroun ldquoPressure dropand heat transfer comparison for both microfin tube andtwisted-tape inserts in laminar flowrdquo ExperimentalThermal andFluid Science vol 18 no 4 pp 323ndash333 1998

[6] M S Lokanath and R D Misal ldquoAn experimental study on theperformance of plate heat exchanger and an augmented shelland tube heat exchanger for different types of fluids for marineapplicationsrdquo in Proceedings of the 5th ISHMT-ASME Heat andMass Transfer Conference pp 863ndash868 TataMcGraw-Hill NewDelhi India 2002

[7] P Sivashanmugam and S Suresh ldquoExperimental studies onheat transfer and friction factor characteristics of laminar flowthrough a circular tube fitted with helical screw-tape insertsrdquoApplied Thermal Engineering vol 26 no 16 pp 1990ndash19972006

[8] P Sivashanmugam and S Suresh ldquoExperimental studies onheat transfer and friction factor characteristics of laminar flowthrough a circular tube fitted with regularly spaced helicalscrew-tape insertsrdquo Experimental Thermal and Fluid Sciencevol 31 no 4 pp 301ndash308 2007

[9] S Jaisankar T K Radhakrishnan and K N Sheeba ldquoStudieson heat transfer and friction factor characteristics of ther-mosyphon solar water heating system with helical twistedtapesrdquo Energy vol 34 no 9 pp 1054ndash1064 2009

[10] A V N Kapatkar B D A S Padalkar and C S KasbeldquoExperimental investigation on heat transfer enhancement inlaminar flow in circular tube equipped with different insertsrdquoAMAE International Journal on Manufacturing and MaterialScience vol 1 pp 1ndash6 2011

[11] J Guo A Fan X Zhang and W Liu ldquoA numerical studyon heat transfer and friction factor characteristics of laminarflow in a circular tube fitted with center-cleared twisted taperdquoInternational Journal ofThermal Sciences vol 50 no 7 pp 1263ndash1270 2011

[12] K Wongcharee and S Eiamsa-ard ldquoFriction and heat trans-fer characteristics of laminar swirl flow through the roundtubes inserted with alternate clockwise and counter-clockwisetwisted-tapesrdquo International Communications in Heat andMassTransfer vol 38 no 3 pp 348ndash352 2011

[13] E Z Ibrahim ldquoAugmentation of laminar flow and heat transferin flat tubes by means of helical screw-tape insertsrdquo EnergyConversion and Management vol 52 no 1 pp 250ndash257 2011

[14] S U S Choi and J A Eastman ldquoEnhancing thermal con-ductivity of fluids with nanoparticlesrdquo in Developments andApplications of Non-Newtonian Flows D A Siguier and HP Wang Eds pp 99ndash105 American Society of MechanicalEngineers New York NY USA 1995

[15] C Y Tsai H T Chien P P Ding B Chan T Y Luh and PH Chen ldquoEffect of structural character of gold nanoparticles innanofluid on heat pipe thermal performancerdquoMaterials Lettersvol 58 no 9 pp 1461ndash1465 2004

[16] M-S Liu M C-C Lin C Y Tsai and C-C Wang ldquoEnhance-ment of thermal conductivity with Cu for nanofluids using

chemical reduction methodrdquo International Journal of Heat andMass Transfer vol 49 no 17-18 pp 3028ndash3033 2006

[17] E Tamjid andBHGuenther ldquoRheology and colloidal structureof silver nanoparticles dispersed in diethylene glycolrdquo PowderTechnology vol 197 no 1-2 pp 49ndash53 2010

[18] SM SMurshed K C Leong and C Yang ldquoEnhanced thermalconductivity of TiO

2water based nanofluidsrdquo International

Journal of Thermal Sciences vol 44 no 4 pp 367ndash373 2005[19] H Zhu C Zhang S Liu Y Tang and Y Yin ldquoEffects of

nanoparticle clustering and alignment on thermal conductiv-ities of Fe

3O4aqueous nanofluidsrdquo Applied Physics Letters vol

89 Article ID 023123 2006[20] J A Eastman U S Choi S Li L J Thompson and S Lee

ldquoEnhanced thermal conductivity through the development ofnanofluidsrdquoMRS Proceedings vol 457 1996

[21] M EMeibodi M Vafaie-Sefti AM Rashidi A Amrollahi MTabasi and H S Kalal ldquoSimple model for thermal conductivityof nanofluids using resistance model approachrdquo InternationalCommunications in Heat and Mass Transfer vol 37 no 5 pp555ndash559 2010

[22] G Pathipakka and P Sivashanmugam ldquoHeat transfer behaviourof nanofluids in a uniformly heated circular tube fittedwith heli-cal inserts in laminar flowrdquo Superlattices and Microstructuresvol 47 no 2 pp 349ndash360 2010

[23] K Wongcharee and S Eiamsa-ard ldquoEnhancement of heattransfer using CuOwater nanofluid and twisted tape withalternate axisrdquo International Communications in Heat and MassTransfer vol 38 no 6 pp 742ndash748 2011

[24] S Suresh K P Venkitaraj and P Selvakumar ldquoComparativestudy on thermal performance of helical screw tape inserts inlaminar flow using Al

2O3water and CuOwater nanofluidsrdquo

Superlattices and Microstructures vol 49 no 6 pp 608ndash6222011

[25] S D Salman A A H Kadhum M S Takriff and A BMohamad ldquoHeat transfer enhancement of laminar nanofluidsflow in a circular tube fitted with parabolic-cut twisted tapeinsertsrdquo The Scientific World Journal vol 2014 Article ID543231 7 pages 2014

[26] S D Salman A A H Kadhum M S Takriff and A BMohamad ldquoCFD simulation of heat transfer and friction factoraugmentation in a circular tube fitted with elliptic-cut twistedtape insertsrdquo Mathematical Problems in Engineering vol 2013Article ID 163839 7 pages 2013

[27] S D Salman A A H Kadhum M S Takriff and A BMohamad ldquoCFD analysis of Heat transfer and friction factorcharacteristics in a circular tube fitted with Quadrant-cuttwisted tape insertsrdquoMathematical Problems in Engineering vol2013 Article ID 273764 8 pages 2013

[28] F P Incropera D P Dewitt T L Bergman and A S LavineFundamentals of Heat and Mass Transfer John Wiley amp Sons2007

[29] H Usui Y Sano K Iwashita and A Isozaki ldquoEnhancement ofheat transfer by a combination of internally grooved rough tubeand twisted taperdquo International Chemical Engineering vol 26no 1 pp 97ndash104 1986

[30] J P Holman Experimental Methods for Engineers McGraw-Hill New York NY USA 2011

[31] R K Shah and A L London Laminar Flow Forced Convectionin Ducts Academic Press New York NY USA 1978

14 Journal of Nanomaterials

[32] P KNagarajan andP Sivashanmugam ldquoCFD simulation of heattransfer augmentation in a circular tube fitted with right-lefthelical inserts with spacerrdquo International Journal of ChemicalEngineering Research vol 1 pp 1ndash11 2009

[33] P Keblinski S R Phillpot S U S Choi and J A EastmanldquoMechanisms of heat flow in suspensions of nano-sized particles(nanofluids)rdquo International Journal of Heat and Mass Transfervol 45 no 4 pp 855ndash863 2002

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

Journal of Nanomaterials 13

part Imdashlaminar flowsrdquo Journal of Heat Transfer vol 115 no 4pp 881ndash889 1993

[4] S K Saha and D Chakraborty ldquoHeat transfer and pressuredrop characteristics of laminar flow through a circular tubefitted with regularly spaced twisted tape elements with multipletwistsrdquo in Proceedings of the Heat andMass Transfer Conferencepp 313ndash318 Kanpur India 1997

[5] S Al-Fahed L M Chamra and W Chakroun ldquoPressure dropand heat transfer comparison for both microfin tube andtwisted-tape inserts in laminar flowrdquo ExperimentalThermal andFluid Science vol 18 no 4 pp 323ndash333 1998

[6] M S Lokanath and R D Misal ldquoAn experimental study on theperformance of plate heat exchanger and an augmented shelland tube heat exchanger for different types of fluids for marineapplicationsrdquo in Proceedings of the 5th ISHMT-ASME Heat andMass Transfer Conference pp 863ndash868 TataMcGraw-Hill NewDelhi India 2002

[7] P Sivashanmugam and S Suresh ldquoExperimental studies onheat transfer and friction factor characteristics of laminar flowthrough a circular tube fitted with helical screw-tape insertsrdquoApplied Thermal Engineering vol 26 no 16 pp 1990ndash19972006

[8] P Sivashanmugam and S Suresh ldquoExperimental studies onheat transfer and friction factor characteristics of laminar flowthrough a circular tube fitted with regularly spaced helicalscrew-tape insertsrdquo Experimental Thermal and Fluid Sciencevol 31 no 4 pp 301ndash308 2007

[9] S Jaisankar T K Radhakrishnan and K N Sheeba ldquoStudieson heat transfer and friction factor characteristics of ther-mosyphon solar water heating system with helical twistedtapesrdquo Energy vol 34 no 9 pp 1054ndash1064 2009

[10] A V N Kapatkar B D A S Padalkar and C S KasbeldquoExperimental investigation on heat transfer enhancement inlaminar flow in circular tube equipped with different insertsrdquoAMAE International Journal on Manufacturing and MaterialScience vol 1 pp 1ndash6 2011

[11] J Guo A Fan X Zhang and W Liu ldquoA numerical studyon heat transfer and friction factor characteristics of laminarflow in a circular tube fitted with center-cleared twisted taperdquoInternational Journal ofThermal Sciences vol 50 no 7 pp 1263ndash1270 2011

[12] K Wongcharee and S Eiamsa-ard ldquoFriction and heat trans-fer characteristics of laminar swirl flow through the roundtubes inserted with alternate clockwise and counter-clockwisetwisted-tapesrdquo International Communications in Heat andMassTransfer vol 38 no 3 pp 348ndash352 2011

[13] E Z Ibrahim ldquoAugmentation of laminar flow and heat transferin flat tubes by means of helical screw-tape insertsrdquo EnergyConversion and Management vol 52 no 1 pp 250ndash257 2011

[14] S U S Choi and J A Eastman ldquoEnhancing thermal con-ductivity of fluids with nanoparticlesrdquo in Developments andApplications of Non-Newtonian Flows D A Siguier and HP Wang Eds pp 99ndash105 American Society of MechanicalEngineers New York NY USA 1995

[15] C Y Tsai H T Chien P P Ding B Chan T Y Luh and PH Chen ldquoEffect of structural character of gold nanoparticles innanofluid on heat pipe thermal performancerdquoMaterials Lettersvol 58 no 9 pp 1461ndash1465 2004

[16] M-S Liu M C-C Lin C Y Tsai and C-C Wang ldquoEnhance-ment of thermal conductivity with Cu for nanofluids using

chemical reduction methodrdquo International Journal of Heat andMass Transfer vol 49 no 17-18 pp 3028ndash3033 2006

[17] E Tamjid andBHGuenther ldquoRheology and colloidal structureof silver nanoparticles dispersed in diethylene glycolrdquo PowderTechnology vol 197 no 1-2 pp 49ndash53 2010

[18] SM SMurshed K C Leong and C Yang ldquoEnhanced thermalconductivity of TiO

2water based nanofluidsrdquo International

Journal of Thermal Sciences vol 44 no 4 pp 367ndash373 2005[19] H Zhu C Zhang S Liu Y Tang and Y Yin ldquoEffects of

nanoparticle clustering and alignment on thermal conductiv-ities of Fe

3O4aqueous nanofluidsrdquo Applied Physics Letters vol

89 Article ID 023123 2006[20] J A Eastman U S Choi S Li L J Thompson and S Lee

ldquoEnhanced thermal conductivity through the development ofnanofluidsrdquoMRS Proceedings vol 457 1996

[21] M EMeibodi M Vafaie-Sefti AM Rashidi A Amrollahi MTabasi and H S Kalal ldquoSimple model for thermal conductivityof nanofluids using resistance model approachrdquo InternationalCommunications in Heat and Mass Transfer vol 37 no 5 pp555ndash559 2010

[22] G Pathipakka and P Sivashanmugam ldquoHeat transfer behaviourof nanofluids in a uniformly heated circular tube fittedwith heli-cal inserts in laminar flowrdquo Superlattices and Microstructuresvol 47 no 2 pp 349ndash360 2010

[23] K Wongcharee and S Eiamsa-ard ldquoEnhancement of heattransfer using CuOwater nanofluid and twisted tape withalternate axisrdquo International Communications in Heat and MassTransfer vol 38 no 6 pp 742ndash748 2011

[24] S Suresh K P Venkitaraj and P Selvakumar ldquoComparativestudy on thermal performance of helical screw tape inserts inlaminar flow using Al

2O3water and CuOwater nanofluidsrdquo

Superlattices and Microstructures vol 49 no 6 pp 608ndash6222011

[25] S D Salman A A H Kadhum M S Takriff and A BMohamad ldquoHeat transfer enhancement of laminar nanofluidsflow in a circular tube fitted with parabolic-cut twisted tapeinsertsrdquo The Scientific World Journal vol 2014 Article ID543231 7 pages 2014

[26] S D Salman A A H Kadhum M S Takriff and A BMohamad ldquoCFD simulation of heat transfer and friction factoraugmentation in a circular tube fitted with elliptic-cut twistedtape insertsrdquo Mathematical Problems in Engineering vol 2013Article ID 163839 7 pages 2013

[27] S D Salman A A H Kadhum M S Takriff and A BMohamad ldquoCFD analysis of Heat transfer and friction factorcharacteristics in a circular tube fitted with Quadrant-cuttwisted tape insertsrdquoMathematical Problems in Engineering vol2013 Article ID 273764 8 pages 2013

[28] F P Incropera D P Dewitt T L Bergman and A S LavineFundamentals of Heat and Mass Transfer John Wiley amp Sons2007

[29] H Usui Y Sano K Iwashita and A Isozaki ldquoEnhancement ofheat transfer by a combination of internally grooved rough tubeand twisted taperdquo International Chemical Engineering vol 26no 1 pp 97ndash104 1986

[30] J P Holman Experimental Methods for Engineers McGraw-Hill New York NY USA 2011

[31] R K Shah and A L London Laminar Flow Forced Convectionin Ducts Academic Press New York NY USA 1978

14 Journal of Nanomaterials

[32] P KNagarajan andP Sivashanmugam ldquoCFD simulation of heattransfer augmentation in a circular tube fitted with right-lefthelical inserts with spacerrdquo International Journal of ChemicalEngineering Research vol 1 pp 1ndash11 2009

[33] P Keblinski S R Phillpot S U S Choi and J A EastmanldquoMechanisms of heat flow in suspensions of nano-sized particles(nanofluids)rdquo International Journal of Heat and Mass Transfervol 45 no 4 pp 855ndash863 2002

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

14 Journal of Nanomaterials

[32] P KNagarajan andP Sivashanmugam ldquoCFD simulation of heattransfer augmentation in a circular tube fitted with right-lefthelical inserts with spacerrdquo International Journal of ChemicalEngineering Research vol 1 pp 1ndash11 2009

[33] P Keblinski S R Phillpot S U S Choi and J A EastmanldquoMechanisms of heat flow in suspensions of nano-sized particles(nanofluids)rdquo International Journal of Heat and Mass Transfervol 45 no 4 pp 855ndash863 2002

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials