建筑环境与能源应用工程专业英语5

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1、LessonFiveHeatTransferTopicsWordslearning1Introducitonofheattransfer2Workingsitepictures33Textlerning44heattransferequipment传热设备heatexchanger热交换器boiler锅炉condenser冷凝器radiator散热器refrigerator冰箱solarcollector太阳能集热器heattransferrate传热(速)率temperaturedifference温差factorofsafety安全系数experimenta

2、lerror实验误差operatingcondition运行条件heattransfercoefficient传热系数undertheseadverseconditions在最不利工况下threeformsofheattransfer:conduction传导convection对流radiation辐射heattransferequipment传热设备heatexchanger热交换器boiler锅炉condenser冷凝器radiator散热器refrigerator冰箱solarcollector太阳能集热器heattransferrate传热(速)率te

3、mperaturedifference温差factorofsafety安全系数experimentalerror实验误差operatingcondition运行条件heattransfercoefficient传热系数undertheseadverseconditions在最不利工况下threeformsofheattransfer:conduction传导convection对流radiation辐射Topicone:FrequentlyusedwordsandphrasesHeatSensibleHeatLatentHeatduetomolecularthe

4、rmalmotionSolidificationfusionLiquefactionevaporationTopictwo:IntroducitonofheattransferConductionConvectionRadiationThreeformsofheattransferForsteady-stateheatconductioninonedimension,theFourierlawistemperaturegradientcross-sectionalareanormaltoflowthermalconductivityheatflowrateEqu

5、ation(1)statesthattheheatflowrateqinthexdirectionisdirectlyproportionaltothetemperaturegradientdt/dxandthecross-sectionalareaAnormaltotheheatflow.Theproportionalityfactoristhethermalconductivityλ.Theminussignindicatesthattheheatflowispositiveinthedirectionofdecreasingtemperature.Cond

6、uctivityvaluesaresometimesgiveninotherunits,butconsistentunitsmustbeusedinEquation(1).(1)Thefundamentalequationforunsteady-stateconductioninsolidsorfluidsinwhichthereisnosubstantialmotioniswherethermaldiffusivityαistheratioλ/ρcp;λisthermalconductivity;ρ,density;andcp,specificheat.Ifα

7、islarge(highconductivity,lowdensityandspecificheat,orboth),heatwilldiffusefaster.Isthereanymistakes?Heattransferinvolvingmotioninafluidduetothedifferenceindensityandtheactionofgravityiscallednaturalconvectionorfreeconvection.Heattransfercoefficientsassociatedwithgasesfornaturalconvec

8、tionaregener