化学英语证书考试(pec)-化工热力学常用术语

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1、化学英语证书考试（PEC）-化工热力学常用术语Absoluteentropy  isentropycalculatedrelativetotheabsolutereferencepointdeterminedbythethirdlawofthermodynamics.Clausiusinequality  firststatedbytheGermanphysicistR.J.E.Clausius(1822-1888),isexpressedasthecyclicintegralof Q/T isalwayslessthanorequaltozero.Thi

2、sinequalityisvalidforallcycles,reversibleorirreversible.Entropy  (fromaclassicalthermodynamicspointofview)isapropertydesignated S andisdefinedas dS=(dQ/T)intrev.Entropy  (fromastatisticalthermodynamicspointofview)canbeviewedasameasureofmoleculardisorder,ormolecularrandomness.Theen

3、tropyofasystemisrelatedtothetotalnumberofpossiblemicroscopicstatesofthatsystem,calledthermodynamicprobability p,bytheBoltzmannrelation, expressedas S=k ln pwhere k istheBoltzmannconstant.Entropybalancerelationforacontrolvolume  isstatedastherateofentropychangewithinthecontrolvolum

4、eduringaprocessisequaltothesumoftherateofentropytransferthroughthecontrolvolumeboundarybyheattransfer,thenetrateofentropytransferintothecontrolvolumebymassflow,andtherateofentropygenerationwithintheboundariesofthecontrolvolumeasaresultofirreversibilities.Entropybalancerelationinge

5、neral  isstatedastheentropychangeofasystemduringaprocessisequaltothenetentropytransferthroughthesystemboundaryandtheentropygeneratedwithinthesystemasaresultofirreversibilities.Entropychangeofaclosedsystem  isduetotheentropytransferaccompanyingheattransferandtheentropygenerationwit

6、hinthesystemboundaries.Entropygeneration  Sgen isentropygeneratedorcreatedduringanirreversibleprocess,isdueentirelytothepresenceofirreversibilities,andisameasureofthemagnitudesoftheirreversibilitiespresentduringthatprocess.Entropygenerationisalwaysapositivequantityorzero.Itsvalued

7、ependsontheprocess,andthusitisnotaproperty.Heattransfer  istheareaundertheprocesscurveona T-S diagramduringaninternallyreversibleprocess.Theareahasnomeaningforirreversibleprocesses.Increaseofentropyprincipleorsecondlawofthermodynamics  isexpressedastheentropyofanisolatedsystemduri

8、ngaprocessalwaysincreasesor,inthe