工程热力学与传热学-试题011

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1、姓名：班级：学号：工程热力学传热学总分题号—三四五傅分AlltheanswersbewrittenontheanswersheetThermodynamics一.PROBLEMS(30pointsfortotal)1Considerawellinsulatedrigidtankthatisdividedintotwocompartmentsbyapartition.Initially,onesideholdsair,whiletheothersideisevacuated.ThepartitionIsnowremoved,andtheairfillstheentiretank・An

2、alysis:(1)thechangeofinternalenergyoftheair;(2)Istheworkdonebyair?(6points)2Writetheapplicableconditionsoftheexpressions.(8points)・(1)从=5(几—G；⑵叱=-[vdp;(3)wf=-A/2；⑷vvz4k_'p、3Describethechangeofenthalpy(熔)ofidealgasduringaprocessfromaninitialstate1toafinalstate2inT-sdiagram・(4points)4Asystemund

3、ergoesaprocessbetweentwofixedstatesfirstinareversiblemannerandtheninanirreversiblemanner.Forwhichcaseistheentropychangegreater?Why?(4points)5AccordingtotheT-sfigureofanidealregenerativeranklecycle(回热循环)，describethethermalprocessesinvolvedinthecycle・Writetheexpressionofthermalefficiency.(8point

4、s)二.CALCULATION(30pointsfortotal)1Considerawellinsulatedhorizontalrigidcylinderthatisdividedintotwocompartmentsbyapistonthatisfreetomovebutdoesnotalloweithergastoleakintotheotherside・Initially,onesideholds0.5kgoftheidealgasat302C,and0.4MPa,whiletheothersideholds0.5kgofthesameidealgasat302C,and

5、0.12MPa.Nowthermalequilibriumisestablishedinthecylinderasaresultofheattransferthroughthepiston.(1)FindexpressionsfortheequilibriumtemperatureTandpressurePreached・(2)CalculatetheentropychangesforAandBandthetotalentropychangeofthecylinder.AssumethatCv,misconstant,Rg=0.287kJ/(kg.K).(15points)1Ani

6、nventorclaimstohavedevisedaheatpumpwhichexchangesheatwithreservoirsat393Kand300K,theworkisprovidedbyaheatenginewhichexchangesheatwithtwoconstanttemperaturereservoirsat1200Kand300K.TheheatengineabsorbsheatQH=1100kJ,producesworkWnet=742.5kJDetermine：Th=1200KTl=300KTl=300K(1)Cantheheatenginework?

7、reversibleorirreversible?(2)IftheheatpumprejectsheatQi=2400kJ,cantheheatpumpwork?reversibleorirreversible?(3)ThemaximumamountofheatthatheatpumpproducesQi,max-(15points)HeatTransfer一.PROBLEMS(24pointsfortotal)1Describetheexpressions(1)Fo