1. December16, 2014 StudentName:___________________
ET 135C ClosedBookFinal Exam
1. Refrigerantfilterdriershave 2functions:Filtertoremove particulate/dirtandadesiccantthat
___________ moisture.
a) physicallyremoves
b) absorbs
c) adsorbs
d) evaporates
2. In a refrigeratingmachine,heatrejectedis__________ heat absorbed.
a) equal to
b) lessthan
c) greaterthan
3. The formationof froston coolingcoilsinarefrigerator
a) increasesheattransfer
b) improvesC.O.P.of the system
c) increasespowerconsumption
d) reducespowerconsumption
4. The by-passfactorfor a coolingcoil
a) increaseswithincrease invelocityof airpassingthroughit
b) decreaseswithincrease invelocityof airpassingthroughit
c) remainsunchangedwithincreaseinvelocityof airpassingthroughit
d) may increase ordecrease withincrease invelocityof airpassingthroughitdependinguponthe
conditionof airentering
5. The difference betweendrybulbtemperatureandwetbulbtemperature,iscalled
a) dry bulbdepression
b) wetbulb depression
c) dewpointdepression
d) degree of saturation
6. Accordingto Dalton'slawof partial pressures,(where Pb=Barometricpressure,Pa= Partial pressure
of dryair, and Pv= Partial pressure of watervapor)
a) Pb = Pa - Pv
b) Pb = Pa + Pv
c) Pb = Pa x Pv
d) Pb = Pa/Pv
7. The relative humidityisdefinedas
a) the mass of watervapor presentin1 ft3 of dry air
b) the mass of watervapor presentin1 lbmof dry air
c) the ratio of the actual mass of watervapor ina unitmassof dryair to the massof watervaporin
the same mass of dry air whenitis saturatedat the same temperature andpressure.
d) the ratio of actual massof watervapor ina givenvolume of moistairto the massof watervapor
inthe same volume of saturatedairat the same temperature andpressure

2. 8. In aqua-ammoniaandLithium-bromide waterabsorptionrefrigerationsystems,the refrigerantsare
respectively
a) waterand water
b) waterand lithiumbromide
c) ammoniaandlithiumbromide
d) ammoniaandwater
9. For ammoniarefrigeratingsystems,the tubesof ashell andtube condenserare made of
a) copper
b) aluminum
c) steel
d) brass
10. The heat transferbyradiation__________ a medium.
a) requires
b) doesnotrequire
11. The sub-coolinginarefrigerationcycle
a) doesnotalter C.O.P.
b) increasesC.O.P.
c) decreasesC.O.P.
d) none of these
12. A watercooledcondenseroperatesata __________ condensingtemperature thananair-cooled
condenser.
a) higher
b) lower
13. The centrifugal compressorsare generallyusedforrefrigerantsthatrequire
a) small displacementsandlowcondensingpressures
b) large displacementsandhighcondensingpressures
c) small displacementsandhighcondensingpressures
d) large displacementsandlowcondensingpressures
14. A pressure gauge onthe discharge side of a refrigerantcompressorreadstoohigh.The reasons will
be
a) lack of coolingwaterthroughcondenser
b) coolingwatertemperature beinghigh
c) dirtycondensersurface
d) all of these
15. The counter-currentflowheatexchangercantransfer__________ heatthan parallel flow heat
exchanger.
a) less
b) more
c) equal amountof

3. 16. The freongroup of refrigerantsare
a) halo-carbonrefrigerants
b) azeotrope refrigerants
c) inorganicrefrigerants
d) hydro-carbonrefrigerants
17. Whichof the followingwouldleadtoareductioninthermal resistance?
a) In conduction,reductioninthe thicknessof the material andanincrease inthermal
conductivity.
b) In convection,stirringof the fluidandcleaningthe heatingsurface.
c) In radiation,increasingthe temperature andreducingthe emissivity.
d) all of the above
18. Foulingfactorisused
a) inheat exchangerdesignasasafetyfactor
b) incase of Newtonianfluids
c) whena liquidexchangesheatwithagas
d) none of the above
19. The natural convectionaircooledcondensersare usedin
a) domesticrefrigerators
b) watercoolers
c) room airconditioners
d) all of these
20. At 100% relative humidity,wetbulbtemperature,drybulbtemperature,dew pointtemperature and
saturationtemperature are equal.
a) correct
b) incorrect
21. The super-heatinginarefrigerationcycle
a) doesnotalter C.O.P.
b) increasesC.O.P.
c) decreasesC.O.P.
d) none of these
22. In a shell andcoil condenser,waterflowsinthe shell andthe refrigerantinthe coil.
a) true
b) false
23. The capillarytube isnot usedinlarge capacityrefrigerationsystemsbecause
a) cost istoo high
b) capacitycontrol isnot possible
c) it ismade of copper
d) requiredpressure dropcannotbe achieved

4. 24. In a vapor compressionsystem,the conditionof refrigerantbefore enteringthe expansionor
throttle valve is
a) highpressure saturatedliquid
b) highpressure wetvapor
c) highpressure verywetvapor
d) lowpressure dryvapor
25. The pressure at the outletof a refrigerantcompressoriscalled
a) suctionpressure
b) discharge pressure
c) critical pressure
d) back pressure
26. If the evaporatortemperature iskeptconstant,the coefficientof performance of arefrigeration
cycle __________ withthe increase incondensertemperature.
a) increases
b) decreases
27. In counter-currentflow heatexchanger,the logarithmictemperature difference betweenthe fluids
is__________ as comparedto parallel flow heatexchanger.
a) same
b) less
c) greater
28. A designerchoosesthe valuesof fluidflow ratesandspecificheatsinsucha mannerthat the heat
capacitiesof the twofluidsare equal.A hotfluidentersthe counterflow heatexchangerat100°F and
leavesat60°F. A cold fluidentersthe heatexchangerat40°F. The meantemperature difference
betweenthe twofluidsis
a) 20°F
b) 40°F
c) 60°F
d) 66.7°F
29. A thermostaticexpansionvalve inarefrigerationsystem
a) ensuresthe evaporatorcompletelyfilledwithrefrigerantof the load
b) issuitable onlyforconstantloadsystems
c) maintainsdifferenttemperaturesinevaporatorinproportiontoload
d) none of the above
30. Duringsub-cooling,sensibleheatfromaliquidrefrigerantisremoved.
a) yes
b) no
31. A valve whichmaintainsaconstant level of liquidinthe evaporator,iscalled
a) automaticexpansionvalve
b) short tube restrictor
c) thermostaticexpansionvalve
d) lowside floatvalve

5. 32. The reciprocatingrefrigerantcompressorsare verysuitablefor
a) small displacementsandlowcondensingpressures
b) large displacementsandhighcondensingpressures
c) small displacementsandhighcondensingpressures
d) large displacementsandlowcondensingpressures
33. Whichof the followingstatementiscorrect?
a) In vaporabsorptionrefrigerator,the compressionof refrigerantisavoided.
b) Sub-coolingcanbe achievedbycirculatingmore quantityof coolingwaterthroughthe
condenser.
c) In vaporcompressionrefrigeration,the vaporisdrawninthe compressorcylinderduringits
suctionstroke andis compressedadiabaticallyduringthe compressionstroke.
d) all of the above
34. The desirable propertyof arefrigerantis
a) lowboilingpoint
b) highcritical temperature
c) highlatentheatof vaporization
d) all of these
35. For large tonnage (more than200 tons) air-conditioningapplications,the compressorrecommended
is
a) reciprocating
b) rotating
c) centrifugal
d) screw
36. The transferof heatby molecularcollisionissmallestin
a) solids
b) liquids
c) gases
d) none of these
37. Whenthe discharge pressure istoohighina refrigerationsystem,highpressurecontrol isinstalled
to stopthe compressor.
a) correct
b) incorrect
38. In a shell andtube heatexchanger,bafflesare providedonthe shell sideto
a) improve heattransfer
b) provide supportfortubes
c) preventstagnationof shell sidefluid
d) all of these

6. 39. Moisture shouldbe removedfromrefrigerantstoavoid
a) freezingatthe expansionvalve
b) restrictiontorefrigerantflow
c) corrosionof steel plates
d) all of these
40. Sensibleheatfactorisgivenby(where S.H. = Sensibleheat,andL.H.= Latentheat)
a)
b)
c)
d)
41. In counter-currentflow heatexchangers
a) boththe fluidsatinletare intheirhotteststate
b) boththe fluidsatinletare intheircoldeststate
c) boththe fluidsatexitare intheirhottest state
d) one fluidiscoldestandthe otherishottestat inlet
42. Whichof the followingrefrigerantishighlytoxicandflammable?
a) ammonia
b) carbon dioxide
c) sulphurdioxide
d) R-502a
e) a. and c.
43. The wetbulbtemperature at100% relative humidityis__________ drybulbtemperature.
a) same as
b) lowerthan
c) higherthan
44. In a vapor absorptionrefrigerationsystem,the compressorof the vaporcompressionsystemis
replacedby
a) liquidpump
b) generator
c) absorberand generator
d) absorber,generatorandliquidpump

7. 45. In whichof the followingrefrigerationsystem,waste heatcanbe effectivelyused?
a) vapor compressioncycle
b) vapor absorptioncycle
c) air refrigerationcycle
d) all of these
46. The material of pipe linesforasystemusingR-22 as a refrigerantshouldbe
a) brass
b) copper
c) steel
d) aluminum
47. In a pressure enthalpychart,the space tothe leftof the saturatedliquidline represents
a) wetvapor region
b) superheatedvaporregion
c) sub-cooledliquidregion
d) none of these
48. Whichstatementisfalse?
a) Hermeticcompressors are popularbecause theyare inexpensive andthe valvesandvalve plates
can be changedshouldthe needarise.
b) Opencompressorsare directdrive orbeltdriven.
c) Scroll compressorsare more toleranttoliquidcontentthanare reciprocatingcompressors.
d) Hermeticcompressorsare suctioncooled.
49. The type of unitthat incorporatesseveralstagesof compressionusingdifferentrefrigerantsiscalled
a _______________ system.
a) directexpansion
b) cascade
c) absorption
d) directstage
50. Whichstatementisfalse?
a) Scroll compressorshave noclearance volume.
b) The rotor of a vane-type rotarycompressortravelseccentricallywithinthe cylinderblock.
c) The velocityof a pistonislimitedbythe sonicvelocityof the refrigerant.
d) Compressionringsare more likelytobe used onpistonscastfrom aluminum
e) The interiorof an opencompressorishermeticallysealedfromthe ambient.