双层幕墙热工计算(En)

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1、ChrisChampagneAE597JHomework#1ComputationalFluidDynamicsandDoubleSkinFacadesIntroduction:IntheHVACfield,thereisaneedtovalidateaproposeddesigntoensureproperperformance.Oneoftwomethodsistypicallyused:experimentalornumerical.Althoughexperimentalvaluesareveryreliablewhenperformedinacontrolledenvironme

2、nt,thereareseveralmajordrawbackstothisapproach.Itisexpensiveandtimeconsuming.ComputationalFluidDynamics(CFD)isanumericalapproachthatisinformativewhilealsosavingtimeandmoney.Experimentscanberepeatedmorerapidlytoensureaccuracyandtoslightlyaltervariablestoseehowperformanceisaffected.Thethermalenviron

3、mentofaspacecanbedescribedusingthevelocity,temperature,pressureandsmokeconcentrationdiagramsthatCFDcanproduce.ThedrawbacksofCFDarethattheprogramsusedrequireacomputerwithlargeamountsofmemoryandprocessorspeedandtobetrulyaccurate,theCFDresultsmustbeverifiedexperimentally.DoubleSkinFacades:Thebuilding

4、thatIamstudyingformyseniorthesisistheManulifeFinancialU.S.OperationsHeadquartersinBoston,Massachusetts.Oneofthemostuniquefeaturesofthebuildingisitsexteriorfacade.Itisafullyglazed8"doubleskincurtinwallfaçade(alsoknownbyseveralothernamesincludingactivewallandventilatedcavitywall).Thistechniqueispopu

5、larinEuropebuthasnotusedveryoftenintheUnitedStates.Themainadvantageofaddingasecondsheetofglassbehindthedoubleglazingisthetemperaturedifferencesbetweentheairintheroomandthesurfaceoftheglasswallisreduced.Thisimprovesthethermalcomfortconditionsintheofficespaceneartheexteriorwallsandalsoreducesenergyc

6、ostsforheatinginwinterandcoolinginsummer.Theheatinsulationpropertiesarebetterthanthatofanormal,doubleglazing,becauseoftheextrainsulatingpropertiesoftheventilatedcavity.AnexampleofasimplifiedtypeofthisfacadecanbefoundinFigure1.CFDApplication:CFDcanbeusedtogaininsightintomultipleglazingperformancean

7、dalsooptimizethedesignandoperationofmultipleglazingsystemssuchasairflowwindowsordoubleskinfacadesintermsofenergyefficiencyandthermalcomfort(Gan,2001).Airflowandheattransfercanbedemonstrated.CFDcanbeusedtopredictt