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ID:18771794
大小:46.00 KB
页数:3页
时间:2018-09-23
《化学英语证书考试(pec)-化工热力学常用术语》由会员上传分享,免费在线阅读,更多相关内容在行业资料-天天文库。
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
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