过程装备与控制工程外文文献翻译

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1、内蒙古工业大学本科毕业设计说明书PrinciplesofMassTransfer1.GeneralRemarksSomeofthemosttypicalchemicalengineeringproblemslieinthefieldofmasstransfer.Adistinguishingmarkofthechemicalengineerishisabilitytodesignandoperateequipmentinwhichreactantsareprepared,chemicalreactionstakeplace,andsep

2、arationsoftheresultingproductsaremade.Thisabilityrestslargelyonaproficiencyinthescienceofmasstransfer.Applicationsoftheprinciplesofmomentumandheattransferarecommoninmanybranchesofengineering,buttheapplicationofmasstransferhastraditionallybeenlargelylimitedtochemicalengin

3、eering.Otherimportantapplicationsoccurinmetallurgicalprocesses,inproblemsofhigh-speedflight,andinwastetreatmentandpollution-controlprocesses.Bymasstransferismeantthetendencyofacomponentinamixturetotravelfromaregionofhighconcentrationtooneoflowconcentration.Forexample,ifa

4、nopentesttubewithsomewaterinthebottomisplacedinaroominwhichtheairisrelativelydry,watervaporwilldiffuseoutthroughthecolumnofairinthetesttube.Thereisamasstransferofwaterfromaplacewhereitsconcentrationishigh(justabovetheliquidsurface)toaplacewhereitsconcentrationislow(atthe

5、outletofthetube).Ifthegasmixtureinthetubeisstagnant,thetransferoccursbymoleculardiffusion.Ifthereisabulkmixingofthelayersofgasinthetubebymechanicalstirringorbecauseofadensitygradient,masstransferoccursprimarilybythemechanismofforcedornaturalconvection.Thesemechanismsarea

6、nalogoustothetransferofheatbyconductionandbyconvection;thereis,however,nocounterpartinmasstransferforthermalradiation.Theanalogybetweenmomentumandenergytransferhasalreadybeenstudiedinsomedetail,anditisnowpossibletoextendtheanalogytoincludemasstransfer.Indiscussingthefund

7、amentalsofmasstransferweshallconsidermainlybinarymixtures,althoughmulticomponentmixturesareimportantinindustrialapplications.Someofthesemorecomplicatedsituationswillbediscussedafterthebasicprincipleshavebeenillustratedintermsofbinarymixtures,7内蒙古工业大学本科毕业设计说明书2.MolecularD

8、iffusionMoleculardiffusionoccursinagasasaresultoftherandommotionofthemolecules.Thismotionissometimesref