Ies mechanical-engineering-2000

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IIIBCHANICAL BNGINBBAING

PAPER-I Wluch one of the followmg sets of thermodyn=c laws/!S d1rectly mvolved m detenrurung the final properties dunng an ad!abahc mnnng process?

a The first and second laws of thermodynam1cs

b The second law of thermodyn=cs and steady flowrelahons

c Perfect gas relahonslnp and steady flowrelahons

d The first law of thermodynam1cs and perfect gas rei ah on sh1p

The aJr Wlth enthalpy of 100 kJ!kg 1S compressed by an aJr compressor to a pressure and Y temperature at wlnch 1ts enthalpy becomes 200 k.Jikg The loss of heat 1S 40 k.Jikg from the compressor as the atr passes through 11 Neglechng kmehc and potenhal energ1es, the power reqmred for an aJr mass flow of 0 5 k.J/s 1S

a 30 kW

b 50 kW

c 70 kW

d 90 kW

ConSider the folloWing statements

1 The first law of thermodynam1cs 1S a !<Ne of conservahon of energy

2 Perpetual mohon maclnne of the first kmd converts energy mto eqU1valent work

3 A closed system does not exchange work or energy With 1ts surroundmgs

4 The second law of thermodyn=cs shpulates the law of conservahon of energy and entropy

Wluch of these statements are correct?

a 1land3

b 2 and4

c 2,3and4

d 1,2and3

A heat engme rece1ves 10 00 k W of heat at a constant temperature of 285 C and reJ eels 492 k W of heat at 5° C ConSider

the folloWing thermodynam1c cycles 1n tlusregard

1 Camot cycle

2 reverSible cycle

3 IrreverSible cycle

VAich of these cycles could posSibly be executed by the engme?

a 1 alone

b 3 alone

c 1and2

d Noneof1,2and3

"] '\ ( L"-" The process 1-2 for steam shown1n the g!Ven figure 1S

" !So bane

b 1Sentrop1c

c 1Senthalp1c,

d iSothermal

In w!uch one of the folloWing workmg sub stances, does the relahon T, I T 1 = (p, I p1) 0 286 hold good 1f the process takes place With zero heat transfer?

a Wetsteam

b Superheat steam

c Petrolvapouranda1rnuxture

d Me


When dry saturated steam 1S throttled from a h1gher pressure to a lower pressure, the

pressure decreases and the volume mcreases

2 temperature decreases and the steam becomes superheated

3 temperature and the dryness llachon mcrease

4 entropy mcreases Without any change m enthalpy

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a 1 and4

b 1,2and4

c land3

d 2and4

1 0 kg of water 1S heated from 3 00 K to 35 0 K m an msulated tank due to chunung achon by a shrrer The amb1ent temperature 1S 300 K In tlus context, match List I W!th hst II and select the correct answer

List I

A Enthalpy change

B Entropy change I kg

C Avadab1hty I kg

D Loss of av31lab1hty

List II

12 2 kJikg

2 1968kJ

3 2090 kJ 4 656Jikg-K

Codes,

b

d

c

'

In wh1ch one of the folloWing S!luahons the entropy change W!ll be negahve?

a Alr expands iSothermally from 6 bars to3bars

b Alr 1S compressed to half the volume at constant pressure

c Heat 1S supphed to atr at constant volume hll the pressure becomes three folds

d Alr expands 1Sentrop1cally from 6 bars to3bars

ConSider the folloWing thermodyn=c relahons

Tds = du + pdv

2 Tds=du-pdv

3 Tds=dh+vdp

4 Tds = dh -vdp

Winch of these thermodynamic relahons are correct?

a land3

b 1 and4

c 2and3

d 2and4

The head added to a closed system dunng a reverSible pro cess 1S g!Ven by Q = aT + p", where a and ~ are constant The entropy change of the system as 1ts temperature changes from T1 toT, 1S equal Co

a a+,B(T,-T1)

b [a+,B(T,-Ij)+,B12(r,'-z;')]11;

c [a12+(T,'-z;')+,B13(r,'-z;')]1z;'

d aln(T,Ilj)+2a(T,-T1)

The mtemal energy of a gas obe)'!ng van

der Waals equahon (p+ J )tv-b)=RT

depends on 1ts

a Temperature

b Temperature and pressure

c Temperature and sp eafi c volume

d Pressure and speafic volume


A real gas obeys perfect gas law at very

1 h1gh temperatures

2 h1gh pressures

3 low pressures Winch of these statements dare correct?

a 1 alone

b 1 and3

c 2 alone

d 3 alone

The Clapeyron equahon Wlth usual notahons 1S g1ven by

a (dTidP),.,=h,g!Tvtg

b (dPidT),.,=h,g!Tvtg

c (dTidP),.,=Th,glvtg

d (dPidD,.,=Th,glvtg

The capaaty of an a1r compressor 1S speafied as 10 m31mm It means that the compressor 1S capable of

a suppl)'!ng 3m3 of compressed a1r per mmute

b compressmg 3 m3 of free a1r per mmute

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c supplymg 3 m3 of compressed aJr at NTC

d compressmg 3 m3 of standard atr per mmute

A two -stage compressor takes in aJr at 1 1 bars and discharges at 20 bars For ma:nmum effiaency, the mtermediate pressure 1S

a 1055bars

b 7 33 bars

c 55bars

d 47bars

For the same max:1mum pressure and heat mput, the most efficient cycle 1S

a Otto cycle

b Diesel cycle

c Brayton cycle

d Dual combushon cycle


1 Octane rahng of gasohne 1S based on !So-octane and !So-heptane fuels wlnch are paraffin's

2 Tetraethyllead 1S added to gasohne to increase octane number

3 Ethylene dibroffi!de 1S added as scavengmg agent to remove lead depoSits on spark plugs

4 Surface igruhon need not necessanly cause kno ckmg


a 1,2,3and4 b 2,'3and4

c 1 and4

d 1,2and3


Recychng exhaust gases W!th intake increases effi!sS!on of oX!des of mtrogen from the engme

2 When the carburetor throttle 1S suddenly opened, the fuel-aJr m1xture leans out temporanly causmg engme stall

3 The effect of mcrease m alhtude on carburettor 1S to ennch the enhre partthrottle operahon

4 Use of mulhple ventun, system makes it posSible to obtaJn a lngh velocity aJr stream when the fuel!S mtroduced at the maJn ventun throat


a 1and3

b 1and2

c 2and3

d 2and4

Match List I (Alr-fuel raho by mass) W!th List II (Engme opera!! on mode) and select the correct answer

List I

A >C

' " c " D 12 5 1

List II

CI engme part load

2 SI engmepartload

3 SI engmeidhng

4 CI full load

5 Sifullload

Codes,

A C c

b

d ConSider the folloWing statements

In down draft carburettor, a hot spot 1S formed at the bottom wall which 1S common for mtake and exhaust marufolds Tiushelpsto

1 improve evaporahon ofhqmd fuel

2 providelngherthermal effiaency

3 reduce fuel consumphon

4 lower the exhaust gas temperature Wluch of these statements are correct?

a 1,2and4

b 1,2and3

c 1,3and4

d 2,3and4

In a petrol engme car, which one of the folloWing performance charactenshcs 1S affected by the front- end volatility of the gasohne used?

a Hot startmg and vapour lock b Engme warm-up and spark plug

fouhng

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c Spark plug fouhng and hot start:tng

d Vapour lock, eng~ne warm-up and spark plug fouhng

In turbo prop, the expans10n of gases takes place approXImately

a 100% m the turbme

b 80% m the turbme and 20% m the nozzle

c 50% m the turbme and 50% m the nozzle

d 100% m the nozzle

The most conunonly used moderator m nuclear power plants 1S

a heavy water

b concrete and bncks

c steel

d graph1te

Sh1eld!ng m a nuclear reactor 1S generally done to protect agamst

a excess electrons

b X-rays

c a- and ~-rays

d neutron and gamma rays

Asserl!on (A) If a cube 1S placed m a hqU1d W!th two of 1ts surfaces parallel to the free surface of the hqU1d, then the pressures on the two surfaces wluch are parallel to the free surface, are the same

Reason (R) Pascal's law states that when a f!U1d 1S at rest, the pressure at any plane 1S the same 1n all d!rechons

a Both A and R are hue and R 1S the correct explanahon of A

b Both A and R are hue but R 1S NOT the correct explanahon of A

c A 1S hue but R 1S false

d A 1S false but R 1S hue

Asserl!on (A) Catalyhc converters for reduchon of ox1des of rutrogen m engme exhaust catulotbe used W!th leaded fuels

Reason (R) Catalyst W!ll be removed due to chem1cal corros10n by lead salts




d A 1S false but R 1S hue

Asserl!on (A) The CI eng~ne 1S baSically more sU1table for supercharg~ng than the SI engme

Reason (R) sup erchargmg knockmg

In the CI engme tends to prevent d1esel




d A!SfalsebutR!Strue

Asserl!on (A) W1th the help of a Bomb calonmeter, the lower calonfic value of a sohd or hqU1d fuel can be deternuned, as the water vapour formed 1S earned away by the exhaust gases

Reason (R) The lower calonfic value of a fuel!S the net value of heat ava1lable found by subtrachng the latent head of the water formed and earned all{ay by exhaust gas from the lu gher cal onfi c value





Asserl!on (A) The thermal effic1ency of Brayton cycle would not necessanly mcrease W!th reheat

Reason (R) Constant pressure hnes on the T-s d!agram shghtly d1verge W!th mcrease m entropy





Asserl!on (A) A thermodynamic system may be conSidered as a quanhty of working substance W!lh wluch mterachons of heat and work are stud!ed

Reason (R) Energy m the form of work and heat are mutually convert1bl e



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c A 1S true but R 1S false

d A 1S false but R 1S true

Asserl:ton (A) All analyses of heat transfer m turbulent flow must eventually rely on expenmental data

Reason (R) The eddy properl:tes vary across the boundary layer and no adequate theory 1S ava~lable to predict thetr behav10ur

a Both A and R are true and R 1S the correct explanahon of A

b Both A and R are true but R 1S NOT the correct explanahon of A



Asserl:ton (A) The leakage heat transfer from the outSide surface of a steel pipe canymg hot gases 1S reduced to a greater extent on promdmg refractory bnck luung on the mS!de of the pipe as compared to that W!th bnck hrung on the outS! de

Reason (R) The refractory bnck hrung on the mS!de of the pipe offers a higher thermal reSiStance





Asserl:ton (A) Thermal conductance of heat pipe 1S several hundred hmes that of the best ava~lable metal conductor under idenhcal condihons

Reason (R) The value of latent heat 1S far greater than that of spea fie heat





Asserl:ton (A) The effiaency of a pump 1S generally less than that of a turbme

Reason (R) Although the losses m the two types of machmes are of the same kmd, the losses m pumps are more due to eddies and turbulence





Assert:ton (A) Modem turbmes have veloaty compounding at the ituhal stages and pressure compoundmg m subsequent stages Reason (R) ExcesSive hp leakage occurs m the lngh pressure reg10n of reachon baldmg





Assert:ton (A) The a~r-fuel ratio employed magasturbme1Saround60 1

Reason (R) A lean m1xture of 60 1 m a gas turbme 1S ma~nly used for complete combust10n





Winch one of the folloWing pus of features and compressors type 1S NOT correct! y matched?

a Intake and delivery ports compress10n " atta~ned by back flow and mtemal compress10n cyhndncal rotor set to eccentnc casmg Vane compressor

b Intenruttent discharge reqmres recetver, produces lngh pressure, slow speed and lubncat10n problems Reciprocahng compressor

c Contmuous flow, radial flow, handles large volume, much higher speed and fitted mto deSign of aero- engmes Centnfugal compressor

d SuccesSive pressure drops through contrachng passages, blades are formed from a number of circular arcs, ax:1al flow

39 ConSider the folloWing statements

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Forced circulahon 1S always used m high pressure power b 01l ers

2 Soot blowers are used for cleamng tube surfaces at regular mtervals

3 Electrostahc preapitator 1S used to remove fly ash from flue gases


a 1,2and3

b 2and3

c 1and3

d 1and2

Once- through boilers operate at

a subcnhcal pressure

b supercnhcal pressure

c subcnhcal as well as supercnhcal pressure

d cnhcal pressure only

Match List I (Components) W!th List II (Funchons) and select the correct answer

List I

A Steam trap

B FuSible plug

C Blow-offcock

D Feed check valve

List II

Controls steam flow rate

Controls rate of water flow to boiler

Puts off furnace fire when water level reaches unsafe hm1 t

4 Removes mud and dut collected at the bottom ofb01ler

5 Drams off water collected by parhal condensat10n of steam m pipes

Codes,

b

d

A

'

Parhal adm1sS1on steam turbine refers to the S1tuat10n where the

a steam 1S ad!mtted partially blades through nozzles

b nozzles occupy the circumference leadmg mto annulus

mto the

complete the blade

c nozzles do not occupy the complete Circumference leadmg mto the blade annulus

d steam 1S adm!tted parhally mto the blades directly

ConSider the folloWing statements regardmg a 1 0 0% react10n h!rbme

1 Change m absolute velocity of steam across the movmg blades 1S zero

2 Change m absolute velocity of steam across the momng blades 1S negahve

3 Enthalpy drop m fixed blades 1S zero

Winch of these statements" /are correct?

a 1 alone

b 2 alone

c 2and3

d 1and3

Winch one of the folloWing pam 1S NOT correct! y matched?

a Internal efficiency of steam turbme Product of stage efficiency and reheat factor

b Stage efficiency of a turbme Raho of ad!abahc heat drop to the iSentropic heat drop per stage

c Dryness frachon of a steam W!thm a stage Decreases due to reheahng

d Steam condensahon through the h!rbme eros10n

dunng expans10n Enhances blade


For supersaturated flow through a steam nozzle, the

enthalpy drop reduces further

2 eX! t temperature mcreases

3 flow rate mcreases

Winch of these statements are correct?

a 1,2and3

b 1and2

c 2and3

d 1and3

Velocity tnangle for a reachon h!rbme stage 1S shownm the grven figure (AB = v1 =absolute veloaty at rotor blade mlet, CB = W! = relahve velocity at rotor blade mtel, CE = w, = relahve veloaty at rotor balade e:nt and CD= CB)

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' ' " ' ill7 D

~ B g

The raho of reach on force to 1m pulse force

" a CE/CB

b CD/CE

c DEIBD

d AEIAB


1 Throttle govemmg 1mproves quahty of steam m the last few stages

Internal effic1ency of senously effected govemmg

steam 1S not by throttle

3 Throttle govermng1sbetterthannozzle govemmg


a 1,2and3

b land3

c 2and3

d land2

Wluch one of the followmg statements 1S correct?

a Reheat factor 1S zero 1f effic1ency of the turbme 1S close to umty

b Lower the effic1ency, h1gher Will be the reheat factor

c Reheat factor 1S mdependent of steam cond1hons atturbme mlet

d AvaJlab1hty of reheat 1S higher at lower pressure end

In a steam power plant, the raho of the iSentropic heat drop m the pnme mover to the amount of heat supphed per umt mass of steam 1S known as

a stage efficiency

b degree of reach on

c Rankme efficiency

d relahve efficiency

The cnhcal pressure raho for max:1mum discharge through a nozzle 1S given by

' b (,: ,)"

,_,

' (";')' d (n~ J~' ConSider the followmg statements

The volumetnc effic1ency of a rec1procahng compressor can be enhanced b,

heahng the mtake aJr

decreas1ng the clearance volume

coohng the 1ntake aJr

Wluch of these statements 1S I are correct?

a 1 alone

b 1and2

c 2and3

d 3 alone

Reciprocahng compressors are promded ~ili

a Simple d!Sd plate valve

b poppetvalve

c spnng-loaded disc valve

d solen01d valve

ConSider the folloWing statements In centnfugal compressor~ there 1S a tendency of mcreasmg surge when

the number of diffuser vanes " less than the number of impeller vanes

2 the number of diffuser vanes 1S greater than the number of impeller vanes

3 the number of diffuser vanes 1S equal to the number of impeller vanes

4 mass flow" greatly m excess of that corresponding to the deSign mass flow

Wlu ch of these statements dare correct?

a 1 and4

b 2 alone

c 3and4

d 2and4

In an axial flow compressor deSign, veloaty diagrams are conshucted from the expenmental data of aerof01l cascades Wluch one of the folloWing statements in tln s regard is correct?

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a Incidence angle of the approaclung a1r 1S measured from the tra1hng edge of the blade

b 5 1S the demahon angle between the angle of incidence and tangent to the camberlme

c The deflechon " of the gas stream while passmg through the cascade 1S

given by o~a1 -a,

d " 1S the sum of the angle of mcidence and camber less any deviahon angle, ie o~ue-5

The effiaency of a Simple gas turbme can be improved by usmg a regenerator, because the

a work of compress10n 1S reduced

b heat reqmred to be supphed 1S reduced

c work output of the turbme 1S mcreased

d heat reJected 1S increased

Wluch one of the followmg patrs of formulae represents the specific speeds of turbme and pump respechvely? (Notahons have thetr usual meanmgs)

a NQ 112 I H3

A and NP112 H

514

b NQ 112 I H3

A and NP112 H

314

c NPw I H314 and NQP112

H514

d NPw I H514 and NQ 112

H314

ConSider the followmg turbmes I wheels

1 FranciS turbme

2 PeltonwheelW!thtwoormoreJets

3 Pelton wheel W!th asmgleJet

4 Kaplan turbme

The correct sequence of these turbmesl wheels m mcreasmg order of their sp ea fie speeds 1S

a 2,3, 1,4

b 3,2, 1,4

c 2,3,4, 1

d 3,2,4, 1

The gross head ava1lable to a hydraulic power plant 1S 1 00 m The uhhzed head m the runner of the hydraulic turbine 1S 72 m If the hydrauhc efficiency of the turbme 1S

90% the pipe fnchon head 1S eshmated to be

a 20m

b 18m

c 16 2m

d 1 8m

Match L!St I (Outlet vane angle 3 2) W!th List II (Curves labelled 1, 2 and 3 m the grven figure) for a pump and select the correct answer

List I

A /3, <90°

B /32 ~90°

c /3,>90° List II

Q Di>charge

Codes,

A

b

d ConSider the regardmg the centnfugal pump

folloWing statements volute cashng of a

1 Loss of heat due to change m veloaty 1S ehmmated

2 Effi aency of the pump 1S mcreased

3 Water from the penphety of the impeller 1S collected and transm1tted to the dehvety pipe at constant velo a ty

Winch of these statements are correct?

a 1,2and3

b land2

c 2and3

d land3

The cavitahons number of any flmd

machmety 1S defined a~ p-,r' (P 1S pVU

absolute pressure, p 1S denSity and V 1S

free stream velocity) The symbol p' denotes

a stahc pressure of flmd

b dyn=c pressure of flmd

c vapour pressure offlmd

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d shear stress offlmd

ConSider the folloWing statements,

A water turbme governor

helps m startmg and shuthng down the turbo umt

2 controls the speed of turbme set to match it With the hydroelectnc system

3 sets the amount of load' wluch a turbine unit has to cany

Wluch of these, statements are correct?

a 1,2and3

b 1and2

c 2and3

d 1and3

ConSider the folloWing, statements regardmg a torque converter

Its maX!mum efficiency 1S less than that of the flmd couphng

2 It has two tu!Ulers and a set of stahonary vanes mterposed between them

3 It has two runners

4 The raho of secondary to pnmary torque 1S zero for the zero value of angular velocity of secondary


a 1and2

b 3and4

c 1 and4

d 2and4


The reheat eye! e helps to reduce

1 field consumphon

2 steam flow

3 the condenser S!ze Wluch of these statements are correct?

a 1and2

b 1and3

c 2and3

d 1,2and3

The outer surface of a long cyhnder 1S mamtamed at constant temperature The cyhnder does not have any heat source The temperature in the cylmder Will

a mcrease lmearly With radms

b decrease hnearly With rad!us

c bemdependentofrad!us

d VaJY loganthnucally, With radms

A compoSite plane walliS made up of two d!fferent matenals of the same thickness and havmg thermal conductnnhes of h and k, respechvely The eqmvalent thermal conduchvity of the slab 1S

a ~+k,

b '"

d

k, + k,

"" '"" ,., A copper Wire of radms 0 5 mm 1S msulated With a sheatlung of thickness 1 nun havmg a thermal conduchvity of 0 5 W/m -K The outSide surface convechve heat transfer coeffiaent!S 10 Wim'- K If the tluckness of msulahon sheatlung !S' ratsed by 10 nun, then the electncal current-carry1ng capaa ty of the Wire Will

a mcrease

b decrease

c remam the same

d VaJY dependmg upon the electncal conduchvity of the Wire

For the fully developed lanunar flow and heat transfer m a urufonnly heated long arcular tube, if the flow veloaty 1S doubled and the tube d!ameter 1S halved, the' heat transfer co effi aent wdl be

a double of the ongmal value

b halfofthe ong~nal value

c same as before

d fourhmesoftheong~nalvalue

Heat transfer by rad!ahon between two grey b o d!es of em!SS! mty 1S prop orh onal to (notahons have their usual mearungs)

" b

d

(E,-J) ( 1 o)

(E,-J) (1 o)/o

(E,-J) (1 o)'

(E,-J) (' ?)

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Solar rad!ahon of 1200 Wim' falls perpend!cularly on a grey opaque surface of enusS!Vily 05 If the surface temperature " 5 ooc and surface enu sS! ve power " 60 0 Wlm', the radioS!Iy of that surface W!ll be

a 600 Wlm'

b 1000W/m2

d

1200 Wim'

1800 Wim'

The overall heat, transfer coefficient U for a plane compo S1 te wall of n 1 ayers 1S g!Ven by (the tluckness of the i th layer 1S t:,

thermal conduchvity of the i th layer 1S k, convective, heat transfer coefficient Is h)

b

d

1 " I 1 -+ L_!_+~; ,_, k, h,

1 " I 1 -+ L_!_+~; ,_, k, h,

The equahon of effechveness "= 1 -e-mu of a heat exchanger 1S valid (NTU 1S number of transfer umts) m the case of

a boiler and condenser for parallel flow

b boiler and condenser for counterflow

c boiler and condenser for both parallel flow and counterflow

d gas turbme for both parallel flow and counterflow

Match List I W!th list II and select the correct answer

List I

A Fm

B Heat exchanger

C TranSient conduct10n

D Heisler chart

List II

UAICmm

2 x/2&

3 .jhplkA

4 hL/ K

Codes,

b

d

D

' ' The Nusselts number 1S related to Reynolds number m lammar and turbulent flows respechvely as a Re -lr.l andRe 02

b RewandRe 08

c Re-wandRe 08

d Re-WandRe- 02

In respect of free convechon over a verhcal flat plate the Nusselt number vanes W!th Grashof number 'Gr' as

a Gr and Gr'A for lammar and turbulent flows respechvely

b

d

Gr112 and Gr"' for lanunar turbulent flows resp echvely

Gr114 and Gr"' for lanunar turbulent flows resp echvely

Gr"' and Gr114 for lanunar turbulent flows resp echvely

ConSider the folloWing condihons for heat transfer (thickness of thermal boundary layer 1S 1\ velocity of boundaty layer iS 1\,

and 5 Prandtl number!S P,)

5,(x)=5(x)'f P,=1

2 a,(x)»5(x),fP,«1

3 a,(x)«5(x)lf P,»1

Wluch of these condihons apply for convech ve heat transfer?

a 1and2

b 2and3

c 1and3

d 1,2and3

The enthalpies at the beg~ruung of compress10n, at the end of compress10n and at the end of condensahon are respechvely 185 kJ!kg, 210 k.Jikg and 85 k.Jikg The COP of the vapour compress10n refn gerahon system 1S

a 0 25

b q

c '

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d 1 35

ConSider the followmg statements regardmg refngerants

1 Refngerant NH3 1S used m reciprocahng compressors

2 Refngerant CO, 1S used m reciprocahng compressors

3 Refngerant R -llis used in centnfugal compressors

Which of these statements are correct?

a land3

b land2

c 2and3

d 1,2and3

The COP of a heat pump /3m and the

COP of a refngerator ~IM are related as

a ~IIP+~M=l

b ~IIP-~IM=l

C ~IM-~Hp=l

d ~HP+~M=O


The pressure m a honzontal capillary tube of a refngerahon system decreases due to ilie

fn chonal reSiStance offered by the tube will!

2 accelerahon of refngerant m the tube

3 heat transfer from the tube wall

4 decrease m the potenhal energy

Which of these statements are correct?

a 1 and4

b 2,3and4

c 1,2and3

d land2

The diScharge pressure of the compressor m the refngerat10n system goes up due to ilie

a Lower volumetnc efficiency of the compressor

b Formahon of scale m the condenser

c Large S!ze of the condenser

d Undercharge oftherefngerant

The leakage in a Freon-based refngerahon system can be detected by usmg alan

a Oxy-acetylene torch

b Halide torch

c Sulphur torch

d Blue litmus paper

ConSider the followmg statements

1 Azeotropes are the mmtures of refngerants and behave hke pure substances

2 Isomers refngerants are compounds W!th the same chenucal formula but have different molecular structures

3 The formula n + p + q = 2m I used for unsaturated chlorofluorocarbon compounds (m, n, p and q are the numbers of atoms of carbon, hydrogen, fluonne and chlonne respechvely)

Wluch of the statements are correct?

a land3

b 2and3

c land2

d 1,2and3


The typical a1r veloahes m the ducts of air-condihorung systems are

lower m reS!denhal bmld!ngs as compared to those of pubhc bmldmgs

2 higher in reS!denhal bmldmg as compared to those of pubhc bmldmgs

3 higher in mdustnal bmldmgs as compared to those of pubhc bmldmgs

4 equal mall types ofbmldmgs

Wluch of these statements slare correct?

a 1 alone

b land3

c 2and3

d 4 alone

When warm saturated air 1S cooled

a excess moiSture condenses

b excess moiSture condenses but relahve hunudity remains unchanged

c excess moiSture condenses and spec!lic hunudity mcrease but relative humid! ty remains unchanged

d spec!lic hmmdity increases and relahve hmmdity decreases

When d-bulb and wet-bulb temperatures are idenhcal, it means that the

a a1r 1S fully saturated and dew-p01nt temperature has reached

b a1r 1S fully saturated

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c dew-pomt temperature has reached and hutllldity 1S 100%

d parl!al pressure of water vapour 1S

equal to total pressure

ConSider the folloWing parameters

1 Dty-bulb temperature

2 Hutllld!tyraho

3 Alrvelocity

4 Solar rad!ahon mtenS!ty

Wluch of these parameters are taken mto account for detertlllmng effechve temperature for human comfort?

a land2

b 1 and4

c 2,3and4

d 1,2and3

The deS!fable a1r velocity m the occupied zone for comfort for summer a!rcond!honers 1S m the range of

a 6 -7 m!tlllnute

b 4 - 5 m!tlllnute

c 2 - 3 m!tlllnute

d 0 5 - 1 5 m/mmute


1 The reconunended outSide a1r reqmred per person for an auditonum 1S

approX!mately 0 25 m3/mm

2 OutSide a1r for venhlal!on purposes causes senSible heat load and also latentheatload

3 The senSible heat factor for an aud!tonum 1S generally kept as 0 7


a land2

b 2and3

c land3

d 1,2and3

An a1r-cond!t10ned room of volume 10m3

has mfiltrahon of a1r eqmvalent to 3 a1r changes DenSity of u 1S 1 2 kg/m3

,

specific heat Cp 1S 1 k.Jikg K and temperature difference between room and ambient a1r 1S 20 K The senSible heat load due to mfiltrated a1r 1S

a 60kJ!hr

b 12k.Jihr

c 6 kW

d 0 2 kW

n

If heat and mass transfer take place Simultaneously the raho of heat transfer coeffiaent to the mass transfer coefficient 1S a funchon oftheraho of

a Schmidt and Reynolds numbers

b Schmidt and Prandtl numbers

c Nusselt and LeW!snumbers

d Reynolds and Lew:1s numbers

An aeroplane travels at 400 kmlhr at sea level where the temperature" 15° C The velo aty of the aeroplane at the same Mach number at an alhtude where a temperature of - 25 oc is preva1hng, would be

a 126 78 kmlhr

b 1306kmlhr

c 371 2 kmlhr

d 400 10 kmlhr

Po--t+~--·~·~·

",~J 1

• I IPlom Moo:k !

....., The plot for the pressure raho along the length of the convergent -divergent nozzle 1S shown in the given figure The sequence of the flow cond!t10ns labelled dl, m, ~ and 0m the figure 1S respechvely

a supersomc, some, subsomc and supersomc

b Some, supersomc subsomc and supersomc

c subsomc, supersomc, some and subsomc

d some, some supersomc and sub some

If the full-scale turbine 1S requued to work under a head of 30 m and to run at 428 rpm, then a quarter-scale turbme model tested under ahead of 10 m must run at

a 143rpm

b 341 rpm

c 428rpm

d 988rpm

The d!mens10nless group formed by wavelength J,., denSity of flmd p, accelerahon due to gramty g and surface tens10n CJ, 1S

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a a!A2gp

b a!Ag'p

c ag!A'p

d a!A'ga

Wluch one of the standard flows 1S represent the flow cyhnder?

followmg sets of supenmposed to

around a rotahng

a Doublet, vortex and uruform flow

b Source, vortex and uruform flow

c Smk, vertex and uruform flow

d Vertex and un1form flow

A float of cub1cal shape has Sides of 10 em The float valve JUSt touches the valve seat to have a flow area of 0 5 em' as shown m the g1ven figure If the pressure of water m the p1pehne 1S 1 bar, the nse of water level h m the tank to JUSt stop the water flowW!ll be

a 7 5 em

b 50 em

c 2 5cm

d 0 5 em

A U- tube manometer 1S cotmected to a p1pehne conveymg water as shownm the g1ven figure The pressure head of water m thep1pehne1S

a 7 12m

b 6 56 m

c 6 0 m

d 5 12m

The eye of a tornado has a radius of 40 m If the maX!mum W!nd veloc1ty 1S 50 rrJ~ the velo a ty at a diStance of 80 m radms 1 s

a 100 rrJs

b 2500 m/s

c 3125m/s

d 25 m/s

If a vessel contammg hqmd moves downward W!th constant accelerat10n g, iliee

a the pressure throughout the hqmd mass 1S ahnosphenc

b the pressure m the hqmd mass 1S greater than the hydro stat1c pressure

c thereW!llbevacuummthehqmd

d the pressure throughout the hqmd mass 1S greater than ahnosphenc

Improved streamhmng produces 25% reduchon m the drag coeff!C!ent of a torpedo When 11 1S travehng fully submerged and assummg the dnvmg power to remam the same, the mcrease m speed W!ll be

a 10%

b 20%

c 25%

d 30%

If a bullet" fired 1n standard a1r at 15 oc at the Mach angle of 30°, the veloc1ty of the bullet would be

a 5135m/s

b 585 5m/s

c 645 5m/s

d 680 5m/s

103 A stream funchon 1S g1ven by (x'- i'l The potenh al funchon of the flow W!ll be

a 2xy + f(x)

b 2xy + constant

c 2(x'-y")

d 2xy + f(y)

The he1ght of a cyhndncal conta1ner 1S tw:!ce that of 1ts diameter The raho of the honzontal forces on the wall of the cyhnder when 11 1S completely filled to that when 11 1S half filled W!lh the same hqmd,

"

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omThe veloc1hes and correspondmg flow areas of the branches labelled CD,®,~, 0 and m for p1pe system shownm the g!Ven figure are g!Ven m the followmg table

Pip. Lol:l<l 1 -(j) 5 anls

"' 6 cmls

"' V, <m/s

" 4 crnls

"' V, cm/o

The velo c1ty Vs would be

a 2 5 crrJs

b 5 crn/s

c 7 5 crrJs

d 10cm/s

-4 "'•rnl ,,_ ,,_ 10 sq em ,,_

106 A p1pe 1S connected m senes to another p1pe whose d1ameter 1S twice and length 1S 32 hmes that of the first p1pe The raho of fnchonal head losses for the first p1pe to those for the second p1 pe 1S (both the p1p es have the same fnchonal constant)

" ' b ' c ' d

107 Wluch one of the followmg statements 1S

correct?

a Hydraul1c grade hne and energy grade !me are the same m flmd flow problems

b Energy grade !me hes above the hydraul1c grade hne and 1S always parallel to 11

c Energy grade !me hes above the hydraul1c grade !me and they are separated from each other by a vert1cal diStance equal to the veloc1ty head

d The hydraul1c grade !me slopes upwards meehng the energy grade !me on! y at the e:nt of flow

If lammar flow takes place m two p1pe~ hamng relahve rough nesses of 0 002 and 0 00 3, at a Reynolds number of 18 15, then

a the p1pe ofrelahve roughness ofO 003 has a lngher fnchon factor

b the p1pe ofrelahve roughness ofO 003 has a lower fnct10n factor

c both p1pes have the same fnchon factor

d no companson 1S posSible due to madequate data

109 A p1pehne connechng two reserv01rs has 1ts d!ameter reduced by 20% due to depoS!hon of chem1cals For a g1ven head d!fference m the reserv01rs W!th unaltered fnchon factor, th!S would cause a reduchon m d!scharge of

'"

'"

a 42 8%

b 20%

c 17 8%

d 10 6%

A tank contammg water has two onfices of the same S!ze at depths of 40 em and 90 crn below the free surface of water the rat1o of diScharges through these on £ices 1S

" " b n c 0

d 1 6 8 1

A P1tot stahc tube 1S used to measure the velo aty of water US!ng a d1fferenhal gauge winch contams a manometnc flmd of relahve denSity 1 4 The deflechon of the gauge flmd when water flows at a veloaty of 1 2 rrJs W!ll be (the coeffic1ent of the tube may be assumed to be 1)

a 1835mm

b 52 4 mm

c 524mm

d 734mm

The development of boundary layer zones labelled F Q, R and S over a flat plate 1S shown m the g1ven figure

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'"

'"

'"

/---,-----~' ' / ,.; ,_; __ .------;.,-

{f"l!/1 fTTT7T! 1 fUllll.2D

Based on tlus figure, match List I (BoundaJY 1 ayer zones) With List II (Types of boundaty layer) and select the correct answer

List I

A c

' Q c R

D ' List II

TranS!honal

2 Lammarv!Scous sub-layer

3 Lammar

4 Turbulent

Codes,

b

d

c

'

A p1pe of 20 em d!ameter and 30 km length transports od from a tankers to the shore Wlth a veloaty of 0 318 m/s The flow 1S lammar If ~ = 0 1 N - rrJs', the power reqmred for the flow would be

a 925kW

b 836kW

c 763kW

d 1013kW

In a turbulent boundaty layer over the enhre length of a plate, the boundaty layer tlnckness 1ncreases With 1ts d!stance X from the leadmg edge as

a X112

b x'" c x'" d x'" Separahon of flmd flow 1S caused by

a Reduchon of pressure m the duechon of flow

b Reduchon of the boundaty layer tluckness

c Presence of adverse pressure grad! en!

d Presence of favourable pressure grachent

When pressure drag over a body 1S large as compared to the fnchon drag, then the shape of the body 1S that of

a An aerof01l

b A streamlined body

c A two-d!mens10nal body

d A bluff body

11 7 A c1rcul ar cylmder of 400 mm d! ameter 1S

rotated about 1ts ax!S 1S a stream of water hamng a uruform veloaty of 4 m/s When both the stragnahon pomts comc1de, the hft force expenenced by the cylmder 1S

a 160 kN/m

b 1005kN/m

c 80 kN/m

d 402kN/m

An automob1le momng at a veloc1ty of 40 km!hr 1 s exp en encmg a wmd reSiStance of 2 kN If the automob1le 1S momng at a veloaty of 50 km!hr, the power requued to over -come the wmd resiStance 1S

a 43 4 kW

b 3 125kW

c 2 5 kW

d 27776kW

When a cyhnder 1S placed m an 1deal flmd and the flow 1S umfonn, the pressure coeffiaent Cp 1S equal to

a 1-sm'e

b

d

1-2sm'e

1-4sm'e

1-8sm'e

If the upstream Mach number of a normal shock occur-nng m a1r (k = 1 4) 1S 1 68, then the Mach number after the shock 1S

a 0 84

b 0 646

c 0 336

d 0 564

Education

Ies mechanical-engineering-2000