雨课堂学堂在线学堂云《Thermodynamics：Fundamentals（北京交通）》单元测试考核答案

第1题Considerasubmarinecruising30mbelowthefreesurfaceofseawaterwhosedensityis1025kg/m3.Theincreaseinthepressureexertedonthesubmarinewhenitdivestoadepthof110mbelowthefreesurfaceisA480kPa

B804kPa

C1400kPaD144kPaE1100kPa第2题Theatmosphericpressuresatthetopandthebottomofamountainarereadbyabarometertobe93.8and100.5kPa.Iftheaveragedensityofairis1.25kg/m^3,theheightofthemountainisA5360mB683m

C547mD8200mE7650m第3题Thepressuredropinaductistobemeasuredbyadifferentialoilmanometer.Ifthedifferentialheightbetweenthetwofluidcolumnsis3.2

cmandthedensityofoilis860kg/m^3,thepressuredropintheductisA28PaB135PaC482PaD

270Pa

E760Pa第1题A1.2-m^3rigidtankcontainsnitrogengasat200kPaand350K.Nowheatistransferredtothenitrogeninthetankandthepressureofnitrogenrisesto900kPa.TheworkdoneduringthisprocessisA840kJ

B0kJC156kJD240kJE1080kJ第2题An8-Lcylindercontainsairat300kPaand300K.Nowairiscompressedisothermallytoavolumeof2L.Theworkdoneonairduringthiscompressionprocessis

A119kJ

B1.8kJC3.3kJD

4.5kJ

E0kJ第3题Abucketofwaterwithamassof20kgat18°Cistobecooledto0°Cbydroppingicecubesat0°Cintoit.Thelatentheatoffusionoficeis334kJ/kg,andthespecificheatofwateris4.18kJ/kg.°C.TheamountoficethatneedstobeaddedisA

4.5kgB0.25kgC10kg

D20kgE8.6kg第4题Apiston-cylinderdevicecontains3kgofairat300kPaand25°C.Duringaquasi-equilibriumisothermalexpansionprocess,20kJofboundaryworkisdonebythesystem,and8kJofpaddle-wheelworkisdoneonthesystem.TheheattransferduringthisprocessisA28kJB20kJC36kJD12kJE4kJProject3-Homework第1题Aheatenginecycleisexecutedwithsteaminthesaturationdome.Thepressureofsteamis2MPaduringheataddition,and0.1MPaduringheatrejection.ThehighestpossibleefficiencyofthisheatengineisA47%B

95%

C53%

D100%E

23%

正确答案：E第2题Aheatenginereceivesheatfromasourceat800°Candrejectsthewasteheattoasinkat40°C.Ifheatisrejectedfromthisengineatarateof80kJ/s,themaximumpowerthisheatenginecanproduceisA194kWB1520kWC80kWD241kWE128kW

第3题Aheatengineoperatesbetweenthetemperaturelimitsof1200°Cand300°C.Ifheatissuppliedtotheheatengineatarateof200kJ/s,themaximumpoweroutputofthisheatengineisA150kW

B200kWC327kW

D

78

kWE122kW正确答案：EProject4-Homework第1题Arigidtankcontains7kgofanidealgasat5atmand30°C.Nowavalveisopened,andhalfofmassofthegasisallowedtoescape.Ifthefinalpressureinthetankis1.5atm,thefinaltemperatureinthetankisA

-91°CB125°C

C-182°CD91°C

E15°C第2题Thepressureinanairstoragetankismeasuredtobe250kPa(gage)inthemorning,and275kPa(gage)intheafternoonasaresultofsolarheating.Thelocalatmosphericpressureis100kPa.Ifthetemperatureofairinthetankis15°Cinthemorning,theairtemperatureintheafternoonis

A

15.9

°C

B31.5

°C

C38.0

°CD16.2

°CE15

°C

第3题

Africtionlesspiston-cylinderdeviceandarigidtankcontain5kgofheliumgasatthesametemperature,pressureandvolume.Nowheatistransferred,andthetemperatureofbothsystemsisdroppedby12°C.Theamountofextraheatthatmustbesuppliedtoheliumgasinthecylinderthatismaintainedatconstantpressureis

A125kJ

B

0kJ

C312kJD187kJE

499kJ第4题AunitmassofanidealgasattemperatureTundergoesareversibleisothermalprocessfromvolumeV1tovolumeV2whileloosingheattothesurroundingsattemperatureTintheamountofq.IfthegasconstantofthegasisRg,theentropychangeofthegasDsduringthisprocessis

A

Ds

=Rg

ln(V2/V1)-q/T

B

Ds

=

Rg

ln(V2/V1)

CDs

=Rg

ln(V1/V2)DDs

=Rg

ln(V1/V2)-q/TE

Ds=0Project6-Homework第1题A230-m^3rigidtankisfilledwithsaturatedliquid-vapormixtureofwaterat120°C.If25%ofthemassisliquidandthe75%ofthemassisvapor,thetotalmassinthetankis

A252kgB824kgC344kg

D230kgE

683kg第2题Waterisboiledat300kPapressureinapressurecooker.Thecookerinitiallycontains3kgofwater.Onceboilingstarted,itisobservedthathalfofthewaterinthecookerevaporatedin30minutes.Iftheheatlossfromthecookerisnegligible,theaveragerateofenergytransfertothecookerisA2.3kWB

136kW

C3.6kWD1.80kWE0.9kW第3题Arigidtankcontains0.8kgofsteamat10MPaand300°C.Thevolumeofthetankis

A11m3B21m3C4.3m3D1.1m3E0.23m3

Project7-Homework第1题Aroomisfilledwithsaturatedmoistairat20°Candatotalpressureof90kPa.Ifthemassofdryairintheroomis100kg,themassofwatervaporisA1.52kgB

2.60kg

C1.62kg

D1.66kgE

4.21kg第2题Aroomcontains40kgofdryairand0.5kgofwatervaporat20°Cand95kPatotalpressure.TherelativehumidityofairintheroomisA1.2%

B2.5%C80%

D56%

E72%第3题Aroomcontainsairat25°Candatotalpressureof87.0kPawitharelativehumidityof85%.ThepartialpressureofdryairisA2.69kPa

B83.8kPaC

84.3kPa

D74.0kPaE

87.0kPa第4题Theairinahouseisat25°Cand72percentrelativehumidity.Nowtheairiscooledatconstantpressure.Thetemperatureatwhichthemoistureintheairwillstartcondensingis

A8.7°CB15.3°C

C18.0°CD19.6°C

E

21.2°CProject8-Homework第1题Airinapiston-cylinderdeviceiscompressedfrom25°Cand100kPato500kPaduringapolytropicprocessforwhichPv^1.3=constant.TheairtemperatureaftercompressionisA156°C

B156°CC

1207°C

D115°CE182°C

第2题Steamiscompressedfrom4MPaand300°Cto9MPaisentropically.ThefinaltemperatureofthesteamisA300°CB

418°CC303°C

D362°C

E446°C

第3题Heliumgasexpandsinanadiabaticturbinefrom2MPaand750°Cto0.18MPaatarateof1.5kg/s.Assumingconstantspecificheatsatroomtemperature,themaximumpoweroutputoftheturbineisA1384kW

B830kWC3613kW

D5316kWE923kW第4题Airat900kPaand25°Cisallowedtoexpandsteadilyandisothermallyto100kPaatarateof1.4kg/s.Themaximumpoweroutputoftheturbineis

A22kWB188kW

C

263kW

D137kW

E94kWProject9-Homework第1题Abulletismovinginstillairat15°Catavelocityof1200m/s.TheairtemperatureatthenoseofthebulletwherestagnationoccursisA716

°C

B716

°C

C1448

°CD386

°CE731

°C正确答案：E第2题Anaircraftisreportedtobecruisinginstillairat5°Cand68kPaataMachnumberof0.82.ThevelocityoftheaircraftisA

92m/sB55m/sC37m/s

D274m/s

E408m/s第3题Airisapproachingaconverging-divergingnozzlewithalowvelocityat20°Cand85kPa,anditleavesthenozzleatasupersonicvelocity.Thevelocityofairatthethroatofthenozzleis

A82m/s

B98m/sC

313m/sD

343m/s

E408m/s第4题TemperatureChangeduringThrottlingAsubstancewhoseJoule-Thomsoncoefficientispositiveisthrottledtoalowerpressure.Duringthisprocess,(selectthecorrectstatement)Athetemperatureofthesubstancewillincrease.Bthetemperatureofthesubstancewilldecrease.C

theentropyofthesubstancewillremainconstant.Dtheentropyofthesubstancewilldecrease.Etheenthalpyofthesubstancewilldecrease.Project10-Homework第1题AnOttocyclewithairastheworkingfluidhasacompressionratioof8.2.Undercoldairstandardconditions,thethermalefficiencyofthiscycleis

A12%

B43%C

52%D57%E75%第2题ACarnotcycleoperatesbetweenthetemperaturelimitsof400Kand1600K,andproduces3600kWofnetpower.TherateofentropychangeoftheworkingfluidduringtheheatadditionprocessisA0B1.8kW/K

C3.0kW/K

D2.3kW/KE

9.0kW/K第3题InanidealOttocycle,airiscompressedfrom1.15kg/m^3and2.2Lto0.26L,andthenetworkoutputofthecycleis620kJ/kg.Themeaneffectivepressure(MEP)forthiscycleis

A

713kPaB

807kPa

C638kPa

D96kPa

E367kPaProject11-Homework第1题AsimpleidealRankinecycleoperatesbetweenthepressurelimitsof20kPaand3MPa,withaturbineinlettemperatureof500°C.Disregardingthepumpwork,thecycleefficiencyisA

26%

B33%C57%

D67%

E74%第2题AsimpleidealRankinecycleoperatesbetweenthepressurelimitsof10kPaand4MPa,withaturbineinlettemperatureof500°C.Themassfractionofsteamthatcondensesattheturbineexitis

A

0%B8%

C14%

D

92%E86%第3题ConsiderasimpleidealRankinecyclewithfixedboilerandcondenserpressuresandturbineinlettemperature.Ifthecycleismodifiedwithidealreheating,(selectthecorrectstatement)Atheturbineworkoutputwilldecrease.Btheamountofheatrejectedwillincrease.Cthepumpworkinputwilldecrease.Dthemoisturecontentatturbineexitwillincrease.Etheamountofheatinputwilldecrease.第4题ConsiderasimpleidealRankinecyclewithfixedboilerandcondenserpressuresandturbineinlettemperature.Ifthecycleismodifiedwithidealregenerationthatinvolvesoneclosedfeedwaterheater,(selectthecorrectstatementperunitmassofsteamflowingthroughtheboiler)Atheturbineworkoutputwillincrease.Btheamountofheatrejectedwillincrease.Cthecyclethermalefficiencywilldecrease.Dthequalityofsteamatturbineexitwilldecrease.Etheamountofheatinputwilldecrease.正确答案：EProject12-Homework第1题Anidealgasrefrigerationcycleusingairastheworkingfluidoperatesbetweenthepressurelimitsof80kPaand240kPa.Airiscooledto40°Cbeforeenteringtheturbine.Thelowesttemperatureofthiscycleis

A

–44

°CB

29

°C

C40

°C

D

-205

°CE

-71

°C第2题Arefrigeratorremovesheatfromarefrigeratedspaceat–10°Catarateof420J/sandrejectsittoanenvironmentat25°C.TheminimumrequiredpowerinputisA420WB

56WC588WD124WE371W第3题Consideranidealgasrefrigerationcycleusingheliumastheworkingfluid.Heliumentersthecompressorat100kPaand–20°Candiscompressedto220kPa.Heliumisthencooledto20°Cbeforeitente