化学化工专业英语试题_化学工程与工艺专业英语阅读教程_化学工程与工艺考教师(42)

Itmustbeemphasized,however,thatwhiletherearesimilaritiesbetweenthetransportprocesses,therearealsoimportantdifferences,especiallybetweenthetransportofmomentum(avector)andthatofheatormass(scalars).Nevertheless,asystematicstudyofthesimilaritiesbetweenthetransportprocessesmakesiteasiertoidentifyandunderstandthedifferencesbetweenthem.必须强调,虽然有相似之处,也有传递过程之间的差异,尤其重要的是运输动量(矢量)和热或质量(标量).然而,系统地研究了相似性传递过程之间的相似性,使它更容易识别和理解它们之间的差别。

1．HowWeApproachtheSubject怎么研究传递过程？

Inordertodemonstratetheogiesbetweenthetransportprocesses,wewillstudyeachoftheprocessinparallel-insteadofstudyingmomentumtransportfirst,thenenergytransport,andfinallymasstransport.Besidespromotingunderstanding,thereisanotherpedagogicalreasonfornotusingtheserialapproachthatisusedinothertextbooks:ofthethreeprocesses,theconceptsandequationsinvolvedinthestudyofmomentumtransportarethemostdifficultforthebeginnertounderstandandtouse.Becauseitisimpossibletocoverheatandmasstransportthoroughlywithoutpriorknowledgeofmomentumtransport,oneisforcedundertheserialapproachtotakeupthemostdifficultsubject(momentumtransport)first.Ontheotherhand,ifthesubjectsarestudiedinparallel,momentumtransportbecomesmoreunderstandablebyreferencetothefamiliarsubjectofheattransport.为了找出传递过程间的相似性，我们将同时研究每一种传递过程——取代先研究动量传递，再传热，最后传质的方法。除了促进理解之外，对于不使用在其他教科书里用到的顺序法还有另一个教学的原因：在三个过程中，包含在动量传递研究中的概念和方程对初学者来说是最难以理解并使用。因为在不具有有关动量传递的知识前提下一个人不可能完全理解传热和传质，在顺序法的情况下他就被迫先研究最难的课程即动量传递。另一方面，如果课程同时被研究，通过参照有关传热的熟悉课程动量传递就变得更好理解。

Furthermore,theparalleltreatmentmakesitpossibletostudytherthephysicalprocessesthatareoccurringratherthanthemathematicalproceduresandrepresentations.Forexample，wewillstudyone-dimensionaltransportphenomenafirstbecauseequationsinsteadofpartialrequiringvectornotationandwecanoftenuseordinarydifferentialequationsinsteadofpartialdifferentialequations,whichareharderto