第三章 理想气体性质与热力过程

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1、第三章理想气体的性质和理想气体的热力过程英文习题1.MassofairinaroomDeterminethemassoftheairinaroomwhosedimensionsare4m×5m×6mat100kPaand25℃2.StateequationofanidealgasAcylinderwithacapacityof2.0m3containedoxygengasatapressureof500kPaand25℃initially.Thenaleakdevelopedandwasnotdiscoveredu

2、ntilthepressuredroppedto300kPawhilethetemperaturestayedthesame.Assumingideal-gasbehavior,determinehowmuchoxygenhadleakedoutofthecylinderbythetimetheleakwasdiscovered.3.Twotanksareconnectedbyavalve.Onetankcontains2kgofcarbonmonoxidegasat77ºCand0.7bar.Theotherta

3、nkholds8kgofthesamegasat27ºCand1.2bar.Thevalveisopenedandthegasesareallowedtomixwhilereceivingenergybyheattransferfromthesurrounding.Thefinalequilibriumtemperatureis42℃Usingtheidealgasmodel,determine(a)thefinalequilibriumpressure,inbar,and(b)theheattransferfor

4、theprocess,inkJ.4.ElectricheatingofairinahouseTheelectricheatingsystemsusedinmanyhousesconsistofasimpleductwithresistancewires.Airisheatedasitflowsoverresistancewires.Considera15-kWelectricsystem.Airenterstheheatingsectionat100kPaand17ºCwithavolumeflowrateof15

5、0m3/min.Ifheatislostfromtheairintheducttothesurroundingsatarateof200W,determinetheexittemperatureofair.CP=1.005kJ/(kg.K).5.EvaluationoftheΔuofanidealgasAirat300Kand200kPaisheatedatconstantpressureto600K.Determinethechangeininternalenergyofairperunitmass,using(

6、a)datafromtheairtable,(b)thefunctionalformofthespecificheat,and(c)theaveragespecificheatvalue.6.PropertiesofanidealgasAgashasadensityof1.875kg/m3atapressureof1barandwithatemperatureof15ºC.Amassof0.9kgofthegasrequiresaheattransferof175kJtoraiseitstemperaturefro

7、m15ºCto250ºCwhilethepressureofthegasremainsconstant.Determine(1)thecharacteristicgasconstantofthegas,(2)thespecificheatcapacityofthegasatconstantpressure,(3)thespecificheatcapacityofthegasatconstantvolume,(4)thechangeofinternalenergy,(5)theworktransfer.7.Freez

8、ingofchickeninaboxAsupplyof50kgofchickenat6℃containedinaboxistobefrozento-18℃inafreezer.Determinetheamountofheatthatneedstoberemoved.Thelatentheatofthechickenis247kJ/kg,anditsspeci