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请有识之士帮忙做一点关于heattransfer的英文介绍啊
更新时间:2024-04-25 08:56:47
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请有识之士帮忙做一点关于heattransfer的英文介绍啊

马莹回答:
  BasicsofHeatTransfer   Inthesimplestofterms,thedisciplineofheattransferisconcernedwithonlytwothings:temperature,andtheflowofheat.Temperaturerepresentstheamountofthermalenergyavailable,whereasheatflowrepresentsthemovementofthermalenergyfromplacetoplace.   Onamicroscopicscale,thermalenergyisrelatedtothekineticenergyofmolecules.Thegreateramaterial'stemperature,thegreaterthethermalagitationofitsconstituentmolecules(manifestedbothinlinearmotionandvibrationalmodes).Itisnaturalforregionscontaininggreatermolecularkineticenergytopassthisenergytoregionswithlesskineticenergy.   Severalmaterialpropertiesservetomodulatetheheattranferedbetweentworegionsatdifferingtemperatures.Examplesincludethermalconductivities,specificheats,materialdensities,fluidvelocities,fluidviscosities,surfaceemissivities,andmore.Takentogether,thesepropertiesservetomakethesolutionofmanyheattransferproblemsaninvolvedprocess.   HeatTransferMechanisms   Heattransfermechanismscanbegroupedinto3broadcategories:   Conduction:Regionswithgreatermolecularkineticenergywillpasstheirthermalenergytoregionswithlessmolecularenergythroughdirectmolecularcollisions,aprocessknownasconduction.Inmetals,asignificantportionofthetransportedthermalenergyisalsocarriedbyconduction-bandelectrons.   Convection:Whenheatconductsintoastaticfluiditleadstoalocalvolumetricexpansion.Asaresultofgravity-inducedpressuregradients,theexpandedfluidparcelbecomesbuoyantanddisplaces,therebytransportingheatbyfluidmotion(i.e.convection)inadditiontoconduction.Suchheat-inducedfluidmotionininitiallystaticfluidsisknownasfreeconvection.   Forcaseswherethefluidisalreadyinmotion,heatconductedintothefluidwillbetransportedawaychieflybyfluidconvection.Thesecases,knownasforcedconvection,requireapressuregradienttodrivethefluidmotion,asopposedtoagravitygradienttoinducemotionthroughbuoyancy.   Radiation:Allmaterialsradiatethermalenergyinamountsdeterminedbytheirtemperature,wheretheenergyiscarriedbyphotonsoflightintheinfraredandvisibleportionsoftheelectromagneticspectrum.Whentemperaturesareuniform,theradiativefluxbetweenobjectsisinequilibriumandnonetthermalenergyisexchanged.Thebalanceisupsetwhentemperaturesarenotuniform,andthermalenergyistransportedfromsurfacesofhighertosurfacesoflowertemperature
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