Sample - Project Phase - I

8/10/2019 Sample - Project Phase - I

1/40

CFD ANALYSIS ON LIQUID-AIR JET COMPRESSOR USING

FLUENT

BY

RAMESH A

(610812408004)

PROJECT REPORT

(PHASE I)

Submitted to the

FACULTY OF MECHANICAL ENGINEERING

In partial fulfillment of the requirement

for the award of the degree

Of

MASTER OF ENGINEERING

IN

ENGINEERING DESIGN

E! PERUMAL MANIME"ALAI ENGINEERING COLLEGE#

HOSUR

ANNA UNI$ERSITY

CHENNAI % 600 02&

DECEMBER# 2014

1


2/40

CERTIFICATE

Certified that this report titled 'CFD ANALYSIS ON LIQUID-AIR JET

COMPRESSOR USING FLUENT, for the phase I of the project is the bonafide work of

M! RAMESH A (610812408004) who carried out the project under my supervision, for the

partial fulfillment of the requirements for the award of the degree of Master of

Engineering inEngineering Design. Certified further that to the best of my knowledge

and belief, the work reported herein does not form part of any other thesis or dissertation on the

basis of which a degree or an award was conferred on an earlier occasion.

Signature of Supervisor Signature of !"

Prof. M.RAVIKUMAR, M.E., Dr. C. SOLAIMUTHU, M. Tec., P.

D.,

#ssistant $rofessor, $rofessor cum "irector %&esearch' and !" ( $.)

"epartment of *echanical +ngineering "epartment of *echanical +ngineering

+r. $erumal *animekalai College of +ngg.. +r. $erumal *animekalai College of +ngineering

H*+ % 6,& 11! H*+ % 6,& 11!

Submitted for the vivavoce e-amination held on

I./. E35. E3/. E35.

!


3/40

DECLARATIO"

I affirm that the project report work entitled CFD ANALYSIS ON LIQUID-

AIR JET COMPRESSOR USING FLUENT being submitted in partial fulfillment for the

award of Master of Engineering #Engineering Design$is the original work carried out

by me. It has not formed the part of any other project submitted.

Signature of the Candidate

RAMESH A

#%1&'1!(&'&&($

I certify that the declaration made above by the candidate is true.

Signature of Supervisor

P6. M. RAVIKUMAR, M.E.,

#ssistant $rofessor,

"epartment of *echanical +ngineering,

+r. $erumal *animekalai College of +ngineering,

osur /01 223.

)


4/40


5/40

TABLE OF CONTENTS

S! NO :

C;! N! DESCRIPTION PAGE NO

#bstract i

1! CHAPTER I - INTRODUCTION 1

2.2 C!*$&+SS!& 58$+S 2

2.2.2. $ositive "isplacement Compressors 9

2.2.2a. &eciprocating Compressors 9

2.2.2b. &otary Compressors 0

2.2.2c. "ynamic Compressors 0

2.9 :+5 +:+C5!& ;

2.0 5!< /

2.0.2 =low pattern of twophase /

2.0.9 =low pattern in vertical tubes /

2.0.0 =low pattern in ori7ontal tubes3

2 CHAPTER 2- LITERATURE SUR$EY *!"+> 9;

4CHAPTER 4- INTRODUCTION TO CFD

26

;.2 ?6*+&IC#> *+5!"S 9/

;.2.2 ?umerical methods include 9/

;.9 # 58$IC#> C=" SI*6>#5I!? C!?SIS5S !=

S+A+> S5#)+S, "+SC&IB+" B+>!iquid air jet compressor.

# >iquidair jet compressor uses a jet of primary fluid water to induce a peripheral

secondary air flow against back pressure. +-pansion of primary jet produces a partial vacuum

+


8/40

near the secondary flow inlet creating a rapid repressuri7ation of the mi-ed fluids followed by a

diffuser to increase the pressure at the e-it.

5he first phase of the project work is concentrated on the numerical study of the >iquid#ir

jet ejector, which involves C=" analysis of >iquid#ir jet ejector. 5his is made to predict the

variation of the entrainment ratio for different independent variables %primary inlet pressure %$2',

Secondary inlet pressure %$9', and "iffuser outlet pressure %$0''.

In this phase of the project work is concentrated on the development of the e-perimental

setup for validating the entrainment ratio of the >iquid#ir jet ejector. =inally, the e-perimental

investigations on entrainment ratio are carried out to compare the numerical simulation of

>iquid#ir jet ejector. 5he obtained numerical results are compared with the e-perimental

analysis of the >iquid#ir jet ejector. It is also found that the numerical and e-perimental results

are comparable with good agreement. 5he independent operating parameters %primary inlet

pressure %$2', and "iffuser outlet pressure %$0'' will be varied and then analytical equation will

be developed by #symptotic Computational 5echniques %#C="' to validate the e-perimental

values.

CHAPTER 1

INTRODUCTION

#ir compressors account for significant amount of electricity used in Indian industries.

#ir compressors are used in a variety of industries to supply process requirements, to operate

pneumatic tools and equipment, and to meet instrumentation needs. !nly 2E 0EF of energy

reaches the point of enduse, and balance 3E @EF of energy of the power of the prime mover

'


9/40

being converted to unusable heat energy and to a lesser e-tent lost in form of friction, misuse and

noise.

1!1 C;** T=;*

Compressors are broadly classified asG $ositive displacement compressor and "ynamic

compressor. $ositive displacement compressors increase the pressure of the gas by reducing the

volume. $ositive displacement compressors are further classified as reciprocating and rotary

compressors. "ynamic compressors increase the air velocity, which is then converted to

increased pressure at the outlet. "ynamic compressors are basically centrifugal compressors and

are further classified as radial and a-ial flow types.

5he flow and pressure requirements of a given application determine the suitability of a

particulars type of compressor.

1!1!1 P*5/5> D5*;9./ C;***

1!1!1 R95;9/5.? C;***

&eciprocating compressors are the most widely used type for air compression. 5hey are

characteri7ed by a flow output that remains nearly constant over a range of discharge pressures.

#lso, the compressor capacity is directly proportional to the speed. 5he output, however, is a

pulsating one. &eciprocating compressors are available in many configurations, the four most


10/40

widely used of which are hori7ontal, vertical, hori7ontal balance opposed and tandem. Aertical

type reciprocating compressors are used in the capacity range of 1E 21E cfm. ori7ontal

balance opposed compressors are used in the capacity range of 9EE 1EEE cfm in multistage

design and upto 2E,EEE cfm in single stage designs.

&eciprocating compressors are also available in variety of typesG

H >ubricated and nonlubricated

H Single or multiple cylinder

H


11/40

and have a lower number of parts which means less failure rate. #mong rotary compressor, the

&oots blower %also called as lobe compressor' and screw compressors are among the most

widely used. 5he roots blower is essentially a lowpressure blower and is limited to a discharge

pressure of 2 bar in singlestage design and up to 9.9 bar in two stage design. 5he most common

rotary air compressor is the single stage helical or spiral lube oil flooded screw air compressor.

5hese compressors consist of two rotors, within a casing where the rotors compress the air

internally. 5here are no valves. 5hese units are basically oil cooled %with air cooled or water

cooled oil coolers' where the oil seals the internal clearances. Since the cooling takes place right

inside the compressor, the working parts never e-perience e-treme operating temperatures. 5he

oil has to be separated from discharge air. Because of the simple design and few wearing parts,

rotary screw air compressors are easy to maintain, to operate and install. 5he oil free rotary

screw air compressor uses specially designed air ends to compress air without oil in the

compression chamber producing true oil free air. 5hese compressors are available as aircooled

or water cooled types and provide the same fle-ibility as oil flooded rotary compressors. 5here is

a wide range of availability in configuration and in pressure and capacity. "ry types deliver oil

free air and are available in si7es up to 9E,EEE cfm and pressure upto 21 bar. >ubricated types are

available in si7es ranging from 2EE to 2EEE cfm, with discharge pressure up to 2E bar.

1!1!19 D=.59 C;***

"ynamic compressors are mainly centrifugal compressors and operate on similar

principles to centrifugal pump. 5hese compressors have appreciably different characteristics as

compared to reciprocating machines. # small change in compression ratio produces a marked

change in compressor output and efficiency. Centrifugal machines are better suited for

applications requiring very high capacities, typically above 29,EEE cfm. 5he centrifugal air

compressor depends on transfer of energy from a rotating impeller to the air. 5his momentum is

converted to useful pressure by slowing the air down in a stationary diffuser. 5he centrifugal air

compressor is an oil free compressor by design. 5he oillubricated running gear is separated from

the air by shaft seals and atmospheric vents. # singlestage centrifugal machine can provide the

same capacity as a multistage reciprocating compressor. *achines with either a-ial or radial

11


12/40

flow impellers are available. #-ial flow compressors are suitable for higher compression ratios

and are generally more efficient than radial compressors. #-ial compressors typically are multi

stage machines, while radial machines are usually singlestage designs.

It is worth noting that the running cost of a compressed air system is far higher than the

cost of a compressor itself %see =igure'. +nergy consumption is around E percent resulting in

increase in operating cost and energy consumption, in order to overcome this difficulty the

proposed system is design to get better energy efficient and low operating e-penses.

1!2 JET EJECTOR

5he injector was invented by a =renchman, enri )iffardin 21K2L and patented in the

6nited ingdomby *essrs Sharp Stewart 4 Co. of )lasgow. *otiveforcewas provided at the

inlet by a suitable highpressure fluid. #n 9/, */ 9/, or / 9;** is a

pumplikedevice that uses the Aenturi effectof a convergingdiverging no77leto convert the

pressureenergy of a motive fluid to velocityenergy which creates a low pressure 7one that draws

in and entrains a suction fluid. #fter passing through the throat of the injector, the mi-ed fluid

e-pands and the velocity is reduced which results in recompressing the mi-ed fluids by

converting velocity energy back into pressure energy. 5he motive fluid may be a liquid, steam or

any other gas. 5he entrained suction fluid may be a gas, a liquid, slurry, or a dustladen gas

stream.

1!
http://en.wikipedia.org/wiki/Henri_Giffardhttp://en.wikipedia.org/wiki/United_Kingdomhttp://en.wikipedia.org/wiki/Glasgowhttp://en.wikipedia.org/wiki/Forcehttp://en.wikipedia.org/wiki/Pumphttp://en.wikipedia.org/wiki/Venturi_effecthttp://en.wikipedia.org/wiki/De_Laval_nozzlehttp://en.wikipedia.org/wiki/Pressurehttp://en.wikipedia.org/wiki/Velocityhttp://en.wikipedia.org/wiki/Henri_Giffardhttp://en.wikipedia.org/wiki/United_Kingdomhttp://en.wikipedia.org/wiki/Glasgowhttp://en.wikipedia.org/wiki/Forcehttp://en.wikipedia.org/wiki/Pumphttp://en.wikipedia.org/wiki/Venturi_effecthttp://en.wikipedia.org/wiki/De_Laval_nozzlehttp://en.wikipedia.org/wiki/Pressurehttp://en.wikipedia.org/wiki/Velocity


13/40


14/40

istorically the most commonlystudied cases of twophase flow are in largescale power

systems. Coal and gasfired power stations used very large boilers to produce steam for use in

turbines. In such cases, pressuri7ed water is passed through heated pipes and it changes to steam

as it moves through the pipe. 5he design of boilers requires a detailed understanding of two

phase flow heattransfer and pressure drop behavior, which is significantly different from the

singlephase case.

+ven more critically, nuclear reactors use water to remove heat from the reactor core

using twophase flow. # great deal of study has been performed on the nature of twophase flow

in such cases, so that engineers can design against possible failures in pipe work, loss of

pressure, and so on

1!,!1F ;//. /-;*

5he flow pattern is generally two types

i' Aertical flow

ii' ori7ontal flow

1!,!2 F ;//. 5. >/59 /+@*

=or cocurrent up flow of gas and liquid in a vertical tube, the liquid and gas phases

distribute themselves into several recogni7able structures.

B+@@= G ?umerous bubbles are observable as the gas is dispersed in the form of discrete

bubbles in the continuous liquid phase. 5he bubbles may vary widely in si7e and shape but

they are typically nearly spherical and are much smaller than the diameter of the tube itself

S+? G with increasing gas void fraction, the pro-imity of the bubbles is very close such

that bubbles collide and coalesce to form larger bubbles, which are similar to a bullet with a

hemispherical nose with a blunt tail end.

1(


15/40

C+. G increasing the velocity of the flow, the structure of the flow becomes unstable

with the fluid traveling up and down in an oscillatory fashion but with a net upward flow.

A..+ G !nce the interfacial shear of the high velocity gas on the liquid film becomes

dominant over gravity, the liquid is e-pelled from the center of the tube and flows as a

continuous phase up the center of the tube. 5he interface is disturbed by high frequency waves

and ripples.

1!,!, F ;//. 5. H5./ /+@*

5wophase flow patterns in hori7ontal tubes are similar to those in vertical flows but the

distribution of the liquid is influenced by gravity that acts to stratify the liquid to the bottom of

the tube and the gas to the top.

B+@@2=

62 5he gas bubbles are dispersed in the liquid with a high concentration of

bubbles in the upper half of the tube due to their buoyancy. = Increasing the gas velocity in a stratified flow, waves are formed on the

interface and travel in the direction of flow . 5he wavesclimb up the sides of the tube, leaving

thin films of liquid on the wall after the passage of the wave .

I./045//0./ 62=urther increasing the gas velocity, these interfacial waves become large

enough to wash the top of the tube. 5his regime is characteri7ed by large amplitude waves

intermittently washing the top of the tube with smaller amplitude waves in between. >arge

amplitude waves often contain entrained bubbles. 5he top wall is nearly continuously wetted

1*


16/40

by the large amplitude waves and the thin liquid films left behind. Intermittent flow is also a

composite of the plug and slug flowregimes.

A..+21 62#t even larger gas flow rates, the liquid forms a continuous annular film around

the perimeter of the tube, similar to that in vertical flow but the liquid film is thicker at the

bottom than the top. 5he interface between the liquid annulus and the vapor core is disturbed

by small amplitude waves and droplets may be dispersed in the gas core. #t high gas

fractions, the top of the tube with its thinner film becomes dry first, so that the annular film

covers only part of the tube perimeter and thus this is then classified as stratifiedwavy flow.

M5*/ 62Similar to vertical flow, at very high gas velocities, all the liquid may be stripped

from the wall and entrained as small droplets in the now continuous gas phase.

CHAPTER 2

LITERATURE SUR$EY

5he ejector was introduced as an engineering device in the early9Eth century. #t the same

time, researchers started to investigate its working mechanism

=au7an&ahman, ".B. et a- K2L have investigated gas entrainment rate as a function of

liquid flow rate in ejectors is investigated using no77les of different geometries. 5he data are

1%


17/40

analy7ed through macroenergy balance for each phase considering air and water inlet line

discharge coefficients. ?o77les with smaller discharge coefficients are effective in producing

higher vacuum and hence higher entrainment rates. It has been observed that the factor limiting

the air entrainment rate is the low discharge coefficient in the air inlet line. igher air inlet line

discharge coefficients can increase the entrainment rate.

*.5. andakure, et a- K9L carried out that the system use of ejectors as a gasliquid

contacting device has been reported to give higher mass transfer rates than conventional

contactors. Computational fluid dynamics %C="' modeling studies were undertaken to

understand the hydrodynamic characteristics with reference to the ejector geometry.

S. Balamurugan, et a- K0L +jectors are gasliquid contactors that are reported to provide

higher mass transfer rates than conventional contactors. "etailed e-periments were performed

and computational fluid dynamics %C="' modeling studies were undertaken to understand the

hydrodynamic characteristics of the ejector geometry..

?. ?. "utta et a- K;L investigated 5he mass transfer and hydrodynamic characteristics of

a loop reactor have been investigated using downflow liquid jet ejectors fitted with straight and

venturitype throats. 5he entminment rate of the liquid jet and the gas holdup were shown asfunctions of power input per unit volume of the liquid. Similarly, the interfacial area and

volumetric masstransfer coefficient were correlated with the power input. 5he interfacial areas

achieved with a venturi ejector are far superior to those obtained with a straight throat ejector.

=or the liquidside mass transfer coefficient, the trend was found to be reversed within the mnge

of the operating variables studied in this work. 5he gasliquid behaviour inside the ejectors was

analysed qualitatively for a better understanding of the phenomenon.

$..*.&. Cramers , et a- K1L =or the design and scaleup of gasliquid ejectors, reliable

data are required which describe the mass transfer characteristics as a function of the physical

fluid properties, geometrical design and the process related parameters. 5herefore, the mass

transfer characteristics of various ejector geometries and scales were investigated using the

desorption of o-ygen from water, by means of an inert gas, as a model system. In order to

1+


18/40

investigate scaleup, the ejector was geometrically scaledup by a factor of 9 %and hence, a

volumetric scaleup by a factor of '. Since industrial venturi reactors are operated at elevated

pressures, the influence of the gas density on the mass transfer characteristics was also studied

Bergander et al K/L studied that the development of a novel vapor compression cycle for

refrigeration with regenerative use of the potential energy of twophase flow e-pansion, which in

traditional systems is lost in e-pansion valves. 5he new cycle includes a second step

compression by an ejector device, which combines the compression with simultaneous throttling

of the liquid.

"essouky, +ttouney K3L carried out a Seawater desalination by parallel feed multiple

effect evaporation has a simple layout in comparison with other multipleeffect or multistage

desalination systems. 5he thermal performance ratio of the 5AC and specific power consumption

of the *AC are found to decrease at higher heating steam temperatures. #lso, an increase of the

heating steam temperature drastically reduces the specific heat transfer area.

Mosto/a0e, 1one 2'3 carrie0 o4t a e56eri7enta- in8estigation

on t9o:6ase, tat te 64r6ose of tis is to a-ign te 8e-ocities in te

7i5ing section in or0er to re04ce te -osses. Te o1;ecti8e is to

i76ro8e te e.

Kan0i- et a- 23 st40ie0 tat te ;et 6476 is e76-o=e0 as 6art of

a s6ace ter7a-:7anage7ent s=ste7 1ase0 on a c=c-e ?no9n as te

so-ar interna- ter7a- 7anage7ent an0 6o9er. @i8e sets a8e te

sa7e 6ri7ar= in-et 6ress4re 9i-e 8ar=ing te secon0ar= 6ress4re.

2.1 JET PUMP

Te tecno-og= of ;et 6476 is ?no9n for 7ore tan a cent4r=. It as een4se0 in ce7ica- an0 6rocess in04str= for 6ro04cing 8ac447. It as een

4se0 as a fee09ater s466-= 0e8ice in -oco7oti8es an0 si6s. @or te -ast fo4r

0eca0es it as een 4se0 as a ;et e;ector in te refrigeration c=c-e. In recent

=ears it is st40ie0 as a 6ro6ose0 s=ste7 for e7ergenc= core coo-ing an0 as

1'


19/40

fee09ater eater an0 4se0 as ;et air e;ector to re7o8e non con0ensa-e

gasses fro7 te con0enser in stea7 6o9er 6-ants. It as a-so een 4se0 in

foo0, 6a6er, oi- e56-oration, 0istrict eating an0 9ater 0esa-ination in04str=.

Te ;et 6476 is a genera- na7e an0 tere are 8ario4s na7es gi8en to it

0e6en0ing 46on te o9, o6erating con0itions an0Bor 4i0 t=6e as gi8en

e-o9

Ejector: It genera--= 0escries a-- t=6es of ;et 6476s tat 0iscarge at a

6ress4re inter7e0iate et9een 7oti8e an0 s4ction 6ress4res.

Injector: It 0escries a-- t=6es of ;et 6476s tat 4se a con0ensa-e gas to

entrain a -i4i0 an0 0iscarge against a 6ress4re iger tan eiter 7oti8e

or s4ction 6ress4re. It is a-so ca--e0 as oi-er in;ector.

Eductor: It is a ;et 6476 tat 4ses -i4i0 as te 7oti8e 4i0 to 6476 -i4i0s.

Jet compressor: It is a ;et 6476 4se0 to oost te 6ress4re of gases.

Siphon: It is a ;et 6476 4ti-i/ing a con0ensa-e 8a6or, as te 7oti8e 4i0, to6476 -i4i0s.

In te -ast tree to fo4r 0eca0es te ;et 6476 as een st40ie0, 7ain-=, as

;et e;ector or in;ector, terefore, tis -iterat4re re8ie9 9i-- foc4s on te

researc 9or? 0one in te 6ast re-ate0 to ;et e;ector an0 in;ector.

2.1.1 Jet ejector

Te re8ie9 = 21+3 o4t-ine0 te 0e8e-o67ents in 7ate7atica-

7o0e-ing an0 0esign of ;et e;ectors. Te re8ie9 so9s tat tere are t9o

asic a66roaces for e;ector ana-=sis. Tese inc-40e 7i5ing of te 7oti8e

an0 entraine0 7e0i47s, eiter at constant 6ress4re or at constant area as

so9n in @ig4re !.1 21'3.

1


20/40

@ig4re !.1 Constant area an0 constant 6ress4re 0esigns of e;ector 21'3

Design 7o0e-s of strea7 7i5ing at constant 6ress4re are 7ore co77on in

-iterat4re eca4se te 6erfor7ance of te e;ectors 0esigne0 = tis 7eto0

is 7ore s46erior to te constant area 7eto0 an0 it co76ares fa8ora-=

against e56eri7enta- 0ata. Te constant 6ress4re 0esign 6roce04re 9as

initia--= 0e8e-o6e0 = 213. S4se4ent-=, se8era- in8estigators a8e 4se0

tis 7o0e- for 0esigning an0 e8a-4ating te 6erfor7ance of 8ario4s t=6es of

;et e;ectors. Tis in8o-8e0 a n47er of 7o0ications in te 7o0e-, es6ecia--=

-osses 9itin te e;ector an0 7i5ing of te 7oti8e an0 entraine0 strea7s. In

tis researc 9or? te constant 6ress4re 0esign 9as 4se0. 1!

!&


21/40

Se8era- teoretica- 7o0e-s a8e een s4ggeste0 an0 e56eri7enta-

9or? carrie0 o4t to st40= te 6erfor7ance of ;et e;ectors 21:!)3. Most of

tese 9ere a66-ie0 to coo-ing an0 refrigeration s=ste7s o6erating at -o9

te76erat4re ranges. Keenan an0 is co9or?ers 21, !)3 6resente0 a 7o0e-

for ana-=/ing air ;et e;ectors. Te= 6resente0 a 1:D 7o0e- of ;et e;ector ase0

on i0ea- gas -a9 in con;4nction 9it te 6rinci6-es of te conser8ation of

7ass, 7o7ent47, an0 energ=. 46ta an0 is co9or?ers 2!!3 0e8e-o6e0 a

teoretica- 7o0e- for stea7:8a6or s=ste7 in a sing-e:stage e;ector. Te

7o0e- is 4se0 to esti7ate te 7oti8e stea7 re4ire7ents o8er an e5ten0e0

range of e;ector -oa0. Ea7es et a-. 2!13 7o0ie0 te 1:D 7o0e- of Keenan

an0 is co9or?ers 21, !)3 = intro04cing te irre8ersii-ities associate0 9it

te no//-e, 7i5ing section, an0 0iF4ser in te 7o0e-. Te= a-so 6erfor7e0

e56eri7entation on a stea7 ;et refrigeration s=ste7. A6ornratana an0

Ea7es 2!(3 6erfor7e0 e56eri7ents on a s7a-- sca-e stea7 e;ector

refrigerator 4sing e;ector 9it a0;4sta-e 6ri7ar= no//-e an0 so9e0 tat a

sing-e o6ti747 6ri7ar= no//-e 6osition cannot e 0ene0 to 7eet a--

o6erating con0itions. Cen an0 S4n 2!*3 6erfor7e0 e56eri7ents to

in8estigate te caracteristics of te stea7 e;ector refrigeration c=c-e. It 9as

fo4n0 tat canging te o6erating con0itions great-= aFects ot te critica-

entrain7ent ratio an0 te critica- ac? 6ress4re. Te= a-so c-ai7e0 tat te

6erfor7ance caracteristics of stea7 e;ector are etter tan tose e;ectors

o6erate0 9it refrigerant R11(.

Te re8ie9 of -iterat4res = 21:!), !%3, so9s tat te 0esign an0

0e8e-o67ent of a stea7 ;et refrigeration s=ste7 re4ires a toro4g 1)

4n0erstan0ing of te o9 insi0e te ;et 6476, es6ecia--=, in te 7i5ing

section. In te 6ast, e;ectors 9ere 0esigne0 ase0 on a c-assica- 1:D teor=

0e8e-o6e0 = Keenan an0 "e47ann 213. Ho9e8er, tis teor= is a66-ica-e,

9en te e;ector is o6erate0 at its critica- ac? 6ress4re an0 0oes not

inc-40e te eFects of te e;ectorGs geo7etries. Recent-=, 9it te e8o-4tion

of co764ters an0 n47erica- so-4tion 7eto0s, researcers are atte76ting to

a66-= n47erica- tecni4es in 7o0e-ing te o9 9itin e;ectors. Teir

!1


22/40


23/40

si74-ate a stea7 e;ector, e4i66e0 in an e56eri7enta- stea7 ;et

refrigeration c=c-e. Te eFects of o6erating con0itions an0 geo7etric

6ara7eters on te 6erfor7ance of stea7 ;et e;ector are in8estigate0 ot

n47erica--= an0 e56eri7enta--=. A-e5is an0 Rog0a?is 2)%3 0e8e-o6e0 a

n47erica- 7o0e- for ;et 6476 ase0 on te teor= of 2)+3. Te= 8a-i0ate0

te res4-ts of teir 7o0e- 9it 8ario4s e56eri7enta- res4-ts a8ai-a-e in

-iterat4re. Katta an0 ara?at 2)'3 0e8e-o6e0 a teoretica- 7o0e- for

ana-=/ing so-ar stea7 ;et coo-ing c=c-es for air con0itioning. Te= st40ie0 te

6erfor7ance of so-ar stea7 ;et coo-ing s=ste7 4n0er 0iFerent 0esign an0

o6erating con0itions 4sing tis 7o0e-. S4n 2)3 0e8e-o6e0 a co764ter

6rogra7 for st40=ing te 6erfor7ance of e;ector refrigeration s=ste7. Te

st40= is foc4se0 on co76aring 8ario4s refrigerants 4se0 in ;et e;ector

refrigeration s=ste7. 1* Piantong an0 is co9or?ers 21!3 st40ie0 e;ector

refrigeration s=ste7, o6erate0 on 9ater as te 9or?ing 4i0. Te= con04cte0

C@D si74-ations 4sing @-4ent co0e. Te 7o0e- 4se0 is te one 4se0 in

C4nnanon0Gs st40= 2(&3. Te n47erica- res4-ts are a-so co76are0 9it

e56eri7enta- ones.

2.1.2 Jet injector

Jet in;ector as een st40ie0 = se8era- researcers in te 6ast !&:)&

=ears an0 6ro6ose0 se8era- s=ste7s for 4se in n4c-ear in04str=. In;ector is

getting 7ore an0 7ore attention eca4se of its ai-it= to generate a ig

ac? 6ress4re, e8en iger tan te 7oti8e 7e0i47 in-et 6ress4re, an0

transfer of eat to entraine0 7e0i47. Ho9e8er, te o9 6eno7enon

tro4g te in;ector is ig-= co76-e5. Terefore a -ot 7ore eFort is re4ire0

to f4--= 4n0erstan0 te eat, 7ass an0 7o7ent47 transfer occ4rring in te

7i5ing section of ;et in;ector. >it te e8o-4tion of co764ters an0

0e8e-o67ent of n47erica- tecni4es, te C@D a66-ication to te o9

6eno7ena in ;et in;ector is eco7ing an eFecti8e too- to 4n0erstan0 te

6=sics of te 6ro-e7. Te e56eri7enta- an0 co764tationa- eForts of so7e

of te researcers, re-ate0 to stea7 ;et in;ectors, are 6resente0 e-o9.

Catta0ori an0 is co9or?ers 2'3 6erfor7e0 e56eri7ents on stea7 in;ector.

!)


24/40

Te ig 6ress4re safet= in;ection s=ste7 for >R is consi0ere0 as te

reference a66-ication of tis in;ector. Te= a-so 6resente0 an0 a66-ie0 a

si76-e one:0i7ensiona- 7ate7atica- 7o0e-, ca--e0 te g-oa- 7o0e-, to tis

in;ector. In tis 7o0e- te 7ass, 7o7ent47 an0 energ= a-ance e4ations

are a66-ie0 at te in-et an0 o4t-et of eac section of te stea7 in;ector. Te

res4-ts ca-c4-ate0 9it tis 7o0e- are in goo0 agree7ent 9it te

e56eri7enta- one. An i76ortant o4tco7e of tese e56eri7ents is tat te

ac? 9ater 6ress4re is ao4t 1& iger tan te in-et stea7 6ress4re.

Deerne et a-. 21&3 a-so a66-ie0 te one:0i7ensiona- g-oa- 7o0e- to

si74-ate te o9 tro4g stea7 in;ector. Te= consi0ere0 sec4rit= 9ater

in;ection in 1% stea7 generators of n4c-ear reactors as te reference

a66-ication. Te= 6erfor7e0 e56eri7ents on a 1B1! sca-e0 test faci-it=,

0esigne0 an0 4i-t to re6resent te 0esire0 s=ste7 of n4c-ear reactor.

Deerne an0 is co:9or?ers 21&3 st40ie0 te in4ence of te 7i5ing section

o4t-et 0ia7eter, te in-et stea7 6ress4re an0 in-et -i4i0 te76erat4re. Te=

re6orte0 tat acc4rac= of te 7o0e- is ao4t 1*. Deerne et a-. 2(13

6erfor7e0 e56eri7ents to 4n0erstan0 te 6=sica- -a9s 0ri8ing te o9 in

te 7i5ing section of a stea7 in;ector. Te= 7eas4re0 8oi0 fraction in te

7i5ing region 9it a77a:ra= atten4ation 7eto0 an0 a-so 8is4a-i/e0 te

o9 in te 7i5ing section 9it an ana-og ca7era. Te= re6orte0 tat at te

entrance of te 7i5ing section te o9 is caracteri/e0 = a strong non:

e4i-iri47 of te76erat4res an0 8e-ocities an0 is strong-= 0issi6ati8e 9it

ig 6ro04ction of irre8ersii-ities. 4ic?-= te o9 eco7es o7ogeneo4s

an0 fo--o9s a 4asi:isentro6ic e8o-4tion. eito4 an0 A=ar 2(:+3 0e8e-o6e0 a

one:0i7ensiona-, stea0= state, contro- 8o-47e ase0 co764ter 6rogra7 to

si74-ate te o9 tro4g stea7 in;ector. Te geo7etr= of stea7 in;ector

se-ecte0 is si7i-ar to tat e56eri7ente0 = 2'3 an0 te reference a66-ication

is 6assi8e core in;ection s=ste7 of a >R. Te res4-ts of te 7o0e- are

8a-i0ate0 9it te e56eri7enta- res4-ts of Catta0ori an0 is co:9or?ers 2'3.

Te a4tors of 2(!:(+3 a8e 0e8e-o6e0 a t9o:0i7ensiona-, t9o:6ase

o9 7o0e- an0 e7e0 it in PHOE"ICS an0 Star:CD soft9are. Te= a-so

!(


25/40

6erfor7e0 e56eri7ents on a 1B!, 1B*, an0 1B+ sca-e0 8is4a-i/e0 stea7

in;ector 7o0e-s. Te 7o0e- is 4se0 to si74-ate stea7 in;ector:0ri8en 6assi8e

core in;ection s=ste7, stea7 in;ector:0ri8en 6ri7ar= -oo6 recirc4-ation

s=ste7 an0 74-ti:stage stea7 in;ectors 0ri8en fee09ater eaters of a08ance

>R. Te= c-ai7e0 tat te con8entiona- core coo-ant in;ection s=ste7s an0

fee09ater eating s=ste7s of n4c-ear 6o9er 6-ant can e re6-ace0 eR.

Te= 4se0 tree 0iFerent e56eri7enta- faci-ities a -a:sca-e faci-it= #IMP:PA"$

in Po-an0, an in04stria- sca-e faci-it= #CLAUDIA$ in @rance an0 anoter

in04stria- sca-e faci-it= #IETI$ in Ita-=. @or C@D si74-ation CATHARE co0e is

4se0 = 7o0if=ing it = intro04cing eat an0 7o7ent47 transfer

corre-ations ase0 on te res4-ts of CLUDIA tests. Tis ne9 7o0e- is 4se0 in a

co76-e5 >>ER 6-ant #C/ec D4?o8an= Po9er P-ant$ in64t 0ata 0ec? an0 a

4it satisfactor= ea8ior is otaine0 ca-c4-ating a -ac?o4t acci0ent. Sa et

a-. 2)3 6erfor7e0 e56eri7ents on a -a:sca-e stea7 ;et 6476 to st40= its

s4ction caracteristics. Te 6eno7ena of 0irect:contact con0ensation in te

7i5ing region are e56-ore0 = 6erfor7ing ):D, stea0= state C@D si74-ations

4sing @-4ent %.) co0e an0 te DCC 7o0e- 0e8e-o6e0 = te sa7e a4tors.

Te ao8e -iterat4re s4r8e= in0icates tat te 6ast researc re-ate0 to ;et

6476 is -i7ite0 to e56eri7enta- 0ata, e76irica- corre-ations, 1:D or !:D

7o0e-ing an0 si74-ation. @4rter7ore, tere is no re6orte0 st40= re-ate0 to

te s4ction caracteristics of stea7 ;et 6476. Terefore, in tis st40= it is

!*


26/40

ai7e0 to 9or? on te 7o0e-ing of trans6ort 6eno7ena an0 s4ction

caracteristics of stea7 ;et 6476. 1'

2.2 DIRECT-C!T"CT C!DE!S"TI! #DCC$

In te 7i5ing section of a stea7:0ri8en, 9ater:entraine0 ;et 6476 te

t9o strea7s co7e into 0irect contact 9it eac oter. As a res4-t 0irect:

contact con0ensation of sat4rate0 stea7 into s4coo-e0 9ater ta?es 6-ace.

Te 6rocess of eat, 7ass an0 7o7ent47 transfer in DCC is ig-=

co76-icate0. It as een st40ie0 e5tensi8e-= in te -ast t9o:tree 0eca0es

eca4se of its i76ortance in a 8ariet= of in04stria- o6erations s4c as

4n0er9ater 6ro64-sion s=ste7s, stea7 ;et 6476s, 0irect fee09ater eaters

an0 n4c-ear reactor s=ste7s #e.g., 0e6ress4ri/ation s=ste7 of P>R an0

6ress4re s466ression s=ste7 of >R$. Tere are 7an= e56eri7enta- an0

teoretica- 9or?s on te o9 in8o-8ing te 6rocess of 0irect:contact

con0ensation. So7e of te7 are re6orte0 ere. A n47er of 6re8io4s

in8estigators 2*&:*!3 6ro6ose0 e76irica- eat transfer corre-ations for DCC of

8a6or ;ets into s4coo-e0 9ater. Tese corre-ations are otaine0 = 4sing a

si76-ie0 stea7:9ater interfacia- area. Tese res4-ts so9 tat te DCC eat

transfer is 8er= eei7er et a-. 2**3 0e8e-o6e0 a

teoretica- e56ression for te 6enetration -engt of 8a6or ;ets in;ecte0 into

4iescent s4coo-e0 -i4i0s of te sa7e 4i0. Te= ass47e0 8a6or ;et as

a5is=7etric free ;et in 9ic te 8a6or 4-es an0 -i4i0 are 0is6erse0

tro4go4t te ;et 6-47e. 1Cen an0 @aet 2*%3 6resente0 si76-ie0

teoretica- 7o0e-s for te 6enetration -engt of te stea7 ;et. Te= ass47e0

an i0ea-i/e0 6-47e sa6e an0 a o7ogeno4s t9o:6ase o9. C47o et a-.

!%


27/40


28/40

9it so:ca--e0 te stea7 con0ensation region 7o0e- 4sing C@ (.(. Te

co764tationa- res4-ts are 8a-i0ate0 9it te test 0ata. >4 et a-. 21*, %):%*3

6erfor7e0 e56eri7ents on DCC of sonic an0 s46ersonic stea7 ;ets in

s4coo-e0 9ater tan? an0 st40ie0 te 6-47e sa6e, 6enetration -engt, eat

transfer coe4 et a-. 21*3 st40ie0 s46ersonic stea7 ;et

con0ensation 6eno7ena for te rst ti7e an0 6resente0 corre-ations for

6enetration -engt an0 con0ensation eat transfer coe


29/40

carrie0 o4t e56eri7ents 4sing 74-ti:ea7 ga77a:ra= 0ensito7etr= to

7eas4re 8oi0 fraction in =0rocaron 74-ti6ase oi-, 9ater an0 gas 6i6e-ines

an0 in oi- an0 gas 6i6e-ines, res6ecti8e-=.

Dong:4i et a-. 2%'3 0e8e-o6e0 a 04a-:energ= ga77a:ra= atten4ation

s=ste7 to 7eas4re te 8o-47e fractions of static oi-, 9ater an0 gas

74-ti6ase 7i5t4res. Te= 6erfor7e0 e56eri7ents on ori/onta- 6i6e o9 =

4sing t9o 0iFerent ga77a:ra= so4rces of A7erici47 #$ an0 Cesi47 #$.

Te= re6orte0 tat te 7eas4re7ents a8e acce6ta-e acc4rac=. As-ina et a-.

2%3 7eas4re0 te 8oi0 fraction in t9o 6ase o9 9it 8ertica- ga77a:ra=

ea7. Te= 4se0 a tra8ersing ea7 ga77a:ra= 0ensito7eter to 6erfor7 te

e56eri7ents. Te= st40ie0 te cross:sectiona- 6ase 0istri4tion of 9ater

an0 ?erosene in a ori/onta- stain-ess stee- section, 4sing ga77a:ra=

ea7.Te st40= of 8oi0 fraction in te 7i5ing section of SJP is carrie0 o4t =

Deerne et a-. 2(13, 4sing ga77a:ra= atten4ation 7eto0. Using tese

e56eri7enta- res4-ts te= 6resente0 t9o e76irica- 7o0e-s for so-8ing te

rest of te 6ara7eters #7ass o9 rates an0 8e-ocities of te t9o 6ases

in8o-8e0$ in te 7i5ing section of SJP. Te ao8e -iterat4re re-ate0 to 8oi0

fraction 7eas4re7ent in 74-ti6ase o9 = ga77a:ra= 0ensito7etr= so9s

tat tis tecni4e 6ro8i0es an eiquidair jet compressor, by using water as

primary fluid. 5he pressure energy of the fluid is converted into velocity energy in primary

!


30/40

no77le, which creates the low pressure 7one. Because of the low pressure 7one it sucks or

entrained the atmospheric air %secondary fluid'. Both the fluids are mi-ed in the mi-ing chamber,

then this mi-ture is gets re compressed in the throat and gain the pressure energy back and then

comes out of the diffuser as water#ir mi-ture.

5he water#ir mi-ture is separated in the separating chamber, then the air is used for the

different operation and water is re circulated to the system by pump.

=ig 0.2 Schematic diagram of proposed system

T ;*./ */+; 9.*5*/*

Centrifugal pumps

:et ejector

)&


31/40

Collecting tank

!rifice meter

$ressure gauges

CENTRIFUGAL PUMPS

Centrifugal pumps are a subclass of dynamic a-isymmetric workabsorbing turbo

machinery. Centrifugal pumps are used to transport liquids(fluids by the conversion of the

rotational kinetic energy to the hydro dynamics energy of the liquid flow. 5he rotational energy

typically comes from an engine or electric motor or turbine. In the typical simple case, the fluid

enters the pump impeller along or near to the rotating a-is and is accelerated by the impeller,

flowing radially outward into a diffuser or volute chamber %casing', from where it e-its.

Common uses include water, sewage, petroleum and petrochemical pumping. 5he reverse

function of the centrifugal pump is a water turbine converting potential energy of water pressure

into mechanical rotational energy.

JET EJECTOR

#n injector, ejector, steam ejector, steam injector, educatorjet pump or thermo

compressor is a type of pump that uses the Aenturi effect of a convergingdiverging no77le toconvert the pressure energy of a motive fluid to velocity energy which creates a low pressure

7one that draws in and entrains a suction fluid. #fter passing through the throat of the injector,

the mi-ed fluid e-pands and the velocity is reduced which results in recompressing the mi-ed

fluids by converting velocity energy back into pressure energy. 5he motive fluid may be a liquid,

steam or any other gas. 5he entrained suction fluid may be a gas, a liquid, a slurry, or a dust

laden gas stream.

5he adjacent diagram depicts a typical modern ejector. It consists of a motive fluid inlet

no77le and a convergingdiverging outlet no77le.


32/40


33/40

use of the technology since the plate must remain completely immersed i.e. the approach pipe

must be full, and the river must be substantially free of debris.

5he secondary inlet %air' flow rate was determined by installing an orifice meter along

with the *anometer.

,!1 MATHEMATICAL MODEL

#s shown as figure 0.2 the process in the ejector can be classified in to three 7ones

2. ?o77le sections, where the primary fluids e-pands through a no77le and secondary fluid

enters the ejector through a suction chamber.

9. *i-ing section, where mi-ing between water and air occurs in a mi-ing chamber

0. "iffuser section, in which the mi-ture passes through and converts its kinectic energy into

pressure

CONSER$ATION EQUATIONS

Conservation equations for momentum, energy and mass are successively applied to a

control volume in the primary and secondary no77les, the mi-ing chamber, the constant area

7one and the diffuser.

E.?= 9.*>/5.G

))


34/40

5>52:2 5-1>

25-1:2

M** 9.*>/5.G

5A5>55-1A5-1>5-1

M./+ 9.*>/5.G

5he momentum equation is needed when shock conditions are present, particularly in the

constant section 7one or during off design operation. Because the 7one in which this

phenomenon takes place is very thin it may be considered to be a discontinuity in the flow, such

that the area change across the shock wave is negligible. 6nder these conditions the momentum

equation reduces to

5>5255-1>

25-1 5-1

So far twophase ejectors have been found wider applications in the fields of refrigeration,

chemical engineering and jet compression. !ut of these three, the field what I have chosen is jet

compression.

E./5../ R/5(ER)

+ntrainment ratio%+&' O O

CHAPTER 4

INTRODUCTION TO CFD

5he need to control and predict the movement of fluids is a common problem. 5he study

of this area is called fluid dynamics and the systems that are studied range from global weather

patterns, through aircraft aerodynamics to the way blood circulates. Computational =luid

"ynamics %C="' takes these problems and solves them using a computer.

C=" and its application is a rapidly developing discipline due to the continuous

development in the capabilities of commercial software and the growth of computer power. C="

is already widely used in industry and its application is set to spread.

)(


35/40

4!1 NUMERICAL METHODS

4!1!1 N+59 /* 5.9+

2. "iscretisation methods.

9. Solvers and numerical parameters.

0. )rid generation and transformation.

;. igh $erformance Computation %$C' and postprocessing.

4!2 A TYPICAL CFD SIMULATION CONSISTS OF SE$ERAL STAGES# DESCRIBED

BELO7

4!2!1 A;;35/5. / ?/=

5he geometry of the physical system needs to be appro-imated by a geometric C#" type

model. 5he more closely the model geometry represents the actual geometry, the more accurate

the results are likely to be.

4!2!2 C/5. / .+59 ?5 5/5. / ?/59

5o identify the discrete, finite locations at which the variables are to be calculated, the

geometry is divided into a finite number of cells that make up the numerical grid. Before doing

this, it is necessary to identify the physical flow phenomena e-pected %turbulence, compressible

flow, shocks, combustion, multiphase flow, mi-ing, etc.' so the grid generated is suitable to

capture these phenomena.

4!2!, S9/5. * . 5.? ;/*

!nce the geometry and grid have been established, the mathematical models and

parameters for those phenomena are then selected and boundary conditions defined throughout

the domain.

4!2!4 C9+/5. / >5@ >+*

)*


36/40

"iscretisation yields a large number of algebraic equations %one set for each cell'. 5hese

equations are then generally solved using an iterative method, starting with a first guess value for

all variables and completing a computational cycle. +rror or residual values are computed from

the discretised equations and the calculations repeated many times, reducing the residual values,

until a sufficiently converged solution is judged to have been reached.

4!2!& D/5./5. *+595./= 9.>? *+/5.

5he final stage in the solution process is to determine when the solution has reached a

sufficient level of convergence.


37/40

=igure ;.2 )ambit Schematic "iagram

4!4 FLUENT

=>6+?5 is the C=" solver of choice for comple- flows ranging from incompressible to

mildly compressible to highly compressible flows. $roviding multiple choices of solver options,

combined with a convergenceenhancing multigrid method, =>6+?5 delivers optimum solution

efficiency and accuracy for a wide range of speed regimes. 5he wealth of physical models in

=>6+?5 allows you to accurately predict laminar and turbulent flows, various modes of heat

transfer, chemical reactions, multiphase flows, and other phenomena with complete mesh

fle-ibility and solutionbased mesh adaption.

GENERAL MODELING CAPABILITIES

9" planar, 9" a-isymmetric, 9" a-isymmetric with swirl, and 0" flows

6nstructured mesh %triangle and quadrilateral elements for 9"'

$rism and pyramid elements for 0"'

Steadystate or transient flows

#ll speed regimes %low subsonic, transonic, supersonic, and hypersonic flows'

In viscid, laminar, and turbulent flows

?ewtonian or non?ewtonian flows

=ull range of turbulence models including kepsilon, komega, &S*, "+S, and >+S

)+


38/40

MODELLING AND SIMULATION

In C=" calculations, there are three main steps.

2. $re$rocessing

9. Solver +-ecution

0. $ost$rocessing

$re$rocessing is the step where the modelling goals are determined and computational

grid is created. In the second step numerical models and boundary conditions are set to start up

the solver. Solver runs until the convergence is reached.


39/40

REFERENCE

2. =au7an&ahman, ".B. 6mesh, ". Subbarao, *. &amasamy Chemical engineering and

processing ;@ %9E2E'

9. *.5. andakure, A.). )aikar, #.


40/40

1. $..*.&. Cramers , #.#.C.*. Beenackers Influence of the ejectors configuration scale and

gas density on the mass transfer characteristics of gasliquid ejectors,Chem.+ng.Sci.9%9EE2'

/. Bergander. : *., 9EE/, P&efrigeration Cycle with 5wo$hase Condensing +jectorQ *agnetic

"evelopment, Inc.

3. "essouky ., +ttouney . R*., 2@@@, P*ultipleeffect evaporation desalination systems

thermal analysisQ "esalination 291 %2@@@' 91@93/

. *ostofi7adeh C., Bohne "., P5heoretical and e-perimental investigation of a twophase (two

component ejector for cold productionQ institute for energie and verfahrentechnik, )ermany.

@.andil S.R*., >ear

Documents

Sample - Project Phase - I