SteadyState Thermal（稳态热）.pptx

SteadyState Thermal（稳态热）.pptx

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ThermalAnalysis,ChapterSix,ANSYSWorkbenchSi,TrainingManual,ThermalAnalysis,ChapterOverview,Inthischapter,performingsteady-stateandtransientthermalanalysesinSimulationwillbecovered:

GeometryAssembliesSolidBodyContactHeatLoadsSolutionOptionsResultsandPostprocessingWorkshop6.1ThermalTransientSetupTransientSettingsTransientLoadsTransientResultsWorkshop6.2,ThecapabilitiesdescribedinthissectionaregenerallyapplicabletoANSYSDesignSpaceEntralicensesandabove,exceptforanANSYSStructurallicense.,TrainingManual,ThermalAnalysis,BasicsofSteady-StateHeatTransfer,Forasteady-state（static）thermalanalysisinSimulation,thetemperaturesTaresolvedforinthematrixbelow:

Assumptions:

Notransienteffectsareconsideredinasteady-stateanalysisKcanbeconstantorafunctionoftemperatureQcanbeconstantorafunctionoftemperatureANSYSWorkbenchSi,TrainingManual,ThermalAnalysis,BasicsofSteady-StateHeatTransfer,FouriersLawprovidesthebasisofthepreviousequation:

Heatflowwithinasolid（FouriersLaw）isthebasisofKHeatflux,heatflowrate,andconvectionaretreatedasboundaryconditionsonthesystemQConvectionistreatedasaboundaryconditionalthoughtemperature-dependentfilmcoefficientsarepossibleItisimportanttoremembertheseassumptionsrelAaNteSdYtSoWorkbenchSiperformingthermalanalysesinSimulation.,ANSYSWorkbenchSi,TrainingManual,ThermalAnalysis,PhysicsFilters,Ifathermal-onlysolutionistobeperformedthePhysicsFiltercanbeusedtofiltertheGUIUnder“ViewmenuPhysicsFilter,”unselectthe“Structural”and“Electromagnetic”optionsThisappliestooptionsinthe“Environment”and“Solution”levelsonly,Ifathermal-stresssimulationistobeperformed,donotturn,offthestructuralphysicsfilter,TrainingManual,ThermalAnalysis,A.Geometry,Inthermalanalyses,alltypesofbodiessupportedbySimulationmaybeused.Solid,surface,andlinebodiesaresupportedForsurfacebodies,thicknessmustbeinputintheDetailsviewoftheGeometrybranchLinebodiecross-sectionandorientationisdefinedwithinDesignModeler,Cross-sectionandorientationinformationresultsinAaNnSYSWorkbenchSi,effectivethermalcross-sectionOnlytemperatureresultsareavailableforlinebodiesThe“PointMass”featureisnotavailableinthermalanalyses,TrainingManual,ThermalAnalysis,Geometry,Shellandlinebodyassumptions:

Forshellbodiesthrough-thicknesstemperaturegradientsarenotavailable.ShellsassumetemperaturesontopandbottomofsurfacearethesameForlinebodiesthroughthicknessvariationinthetemperatureisnotavailable.Linebodiesassumethetemperatureisconstantacrossthecross-sectionTemperaturevariationwillstillbeconsideredalongthelinebodyANSYSWorkbenchSi,ANSYSWorkbenchSi,TrainingManual,ThermalAnalysis,MaterialProperties,ThermalConductivityisinputintheEngineeringDataapplicationTemperature-dependentthermalconductivityisinputasatable,Ifanytemperature-dependentmaterialpropertiesexist,thiswillresultinanonlinearsolution.,Theonlyrequiredmaterialpropertyisthermalconductivity,ANSYS,WorkbenchSi,TrainingManual,ThermalAnalysis,B.AssembliesSolidBodyContact,Whenimportingassembliesofsolidparts,contactregionsareautomaticallycreatedbetweenthesolidbodiesenablingheattransferbetweenpartsinanassembly,ModelshownisfromasampleInventorassembly.,TrainingManual,ThermalAnalysis,AssembliesContactRegionNoheatspreadingisconsideredinthecontact/targetinterface,HeatflowwithinthecontactregionisinthecontactnormaldirectiononlyHeatflowsonlyifatargetelementispresentinthenormaldirectionofacontactelement,Inthefigureontheleft,thesolid,greendouble-aArroNwsSinYdiScateWorkbenchSiheatflowwithinthecontactregion.Heatflowonlyoccursifatargetsurfaceisnormaltoacontactsurface.Thelight,dottedgreenarrowsindicatethatnoheattransferwilloccurbetweenparts.,TrainingManual,ThermalAnalysis,AssembliesContactRegion,Ifthepartsareinitiallyincontactheattransferwilloccurbetweentheparts.IfthepartsareinitiallyoutofcontactnoheattransfertakesplaceSummary:

ANSYSWorkbenchSiThepinballregiondetermineswhencontactoccursandisautomaticallydefinedandsettoarelativelysmallvaluetoaccommodatesmallgapsinthemodel,ANSYSWorkbench,Si,TrainingManual,ThermalAnalysis,AssembliesContactRegion,Ifthecontactisbondedornoseparation,thenheattransferwilloccur（solidgreenlines）whenthesurfacesarewithinthepinballradius,Inthisfigureontheright,thegapbetweenthetwopartsisbiggerthanthepinballregion,sonoheattransferwilloccurbetweentheparts,PinballRadius,ANSYSWorkbenchSi,TrainingManual,ThermalAnalysis,AssembliesThermalConductanceTheamountofheatflowbetweentwopartsisdefinedbythecontactheatfluxq:

whereTcontactisthetemperatureofacontact“node”andTtargetisthetemperatureofthecorrespondingtarget“node”Bydefault,TCCissettoarelativelyhighvaluebasedonthelargestmaterialconductivitydefinedinthemodelKXXandthediagonaloftheoverallgeometryboundingbox,ASMDIAG.,Thisessentiallyprovidesperfectconductancebetweenparts.,ANSYSWor,kbenchSi,TrainingManual,ThermalAnalysis,AssembliesThermalConductance,PerfectthermalcontactconductancebetweenpartsmeansthatnotemperaturedropisassumedattheinterfaceOnemaywanttoincludefinitethermalconductanceinsteadThecontactconductancecanbeinfluencedbymanyfactors:

surfaceflatnesssurfacefinishoxidesentrappedfluidscontactpressuresurfacetemperatureuseofconductivegrease,DT,T,x,ANSYSW,orkbenchSi,TrainingManual,ThermalAnalysis,AssembliesThermalConductance,InANSYSProfessionallicensesandabove,theusermaydefineafinitethermalcontactconductance（TCC）ifthePurePenaltyorAugmentedLagrangeFormulationisusedThethermalcontactconductanceperunitareaisinputforeachcontactregionintheDetailsviewIfthermalcontactresistanceisknowninvertthisvalueanddividebythecontactingareatoobtainTCCvalue,If“ThermalConductance”isleftat“ProgramChosen,”near-perfectthermalcontactconductancewillbedefined.thermalcontactconductancecanbeinputwhichisthesameasincludingthermalcontactresistanceatacontactinterface.,ANSYSWorkbenchSi,TrainingManual,ThermalAnalysis,AssembliesThermalConductance,ThermalContactNotes:

ForsymmetriccontacttheuserdoesnotneedtoaccountforadoublethermalcontactresistanceMPCbondedcontactallowsforperfectthermalcontactconductance,ANSYSWorkbench,Si,TrainingManual,ThermalAnalysis,AssembliesSurfaceBodyContact,Edgecontactisasubsetofgeneralcontact:

ForcontactincludingshellfacesorsolidedgesonlybondedornoseparationbehaviorisallowedForcontactinvolvingshelledgesonlybondedbehaviorusingMPCformulationisallowed:

Theusercansetthesearchdirectionaseitherthetargetnormalorpinballregion.Ifagapexiststhepinballregioncanbeusedforthesearchdirectiontodetectcontactbeyondagap,ANSYSWor,kbenchSi,TrainingManual,ThermalAnalysis,AssembliesSpotWeld,Spotweldsprovidediscreetheattransferpoints:

SpotwelddefinitionisdoneintheCADsoftware（currentlyonlyDesignModelerandUnigraphics）SpotweldscanbecreatedinSimulationmanuallyatvertices,TrainingManual,ThermalAnalysis,C.HeatLoads,HeatFlow:

Aheatflowratecanbeappliedtoavertex,edge,orsurface.TheloadgetsdistributedformultipleselectionsHeatflowhasunitsofenergy/timeHeatFlux:

AheatfluxcanbeappliedtosurfacesonlyHeatfluxhasunitsofenergy/time/area,InternalHeatGeneration:

ANSYSWorkbenchSiAninternalheatgenerationratecanbeappliedtobodiesonly.Heatgenerationhasunitsofenergy/time/volume,Apositivevalueforheatloadwilladdenergytothesystem.,TrainingManual,ThermalAnalysis,AdiabaticConditions,PerfectlyInsulated:

PerfectlyinsulatedconditionisappliedtosurfacesThisisthedefaultconditioninthermalanalyseswhennoloadisapplied:

ThisloadtypeisusedasawaytoremoveloadingonspecifiedsurfacesForexample,itmaybeeasierforausertoapplyheatfluxorconvectiononanentirepart,thenusetheperfectlyinsulatedconditiontoselectivelyremovetheloadingonsomesurfacesANSYSWorkbenchSi,ANSYSWorkbenchSi,TrainingManual,ThermalAnalysis,ThermalBoundaryConditions,Temperature,ConvectionandRadiation:

AtleastonetypeofthermalboundaryconditionmustbepresenttopreventthethermalequivalentofrigidbodymotionGivenTemperatureorConvectionloadshouldnotbeappliedonsurfacesthatalreadyhaveanotherheatloadorthermalboundaryconditionappliedtoitPerfectinsulationwilloverridethermalboundaryconditionsGivenTemperature:

Imposesatemperatureonvertices,edges,surfacesorbodiesTemperatureisthedegreeoffreedomsolvedfor,ANSYSWorkbenchSi,TrainingManual,ThermalAnalysis,ThermalBoundaryConditions,Convection:

Appliedtosurfacesonly（edgesin2Danalyses）Convectionqisrelatedtoafilmcoefficienth,thesurfaceareaA,andthedifferenceinthesurfacetemperatureTsurface&ambienttemperatureTbulk,“h”and“Tbulk”areuser-inputvaluesThefilmcoefficienthcanbeconstantortemperaturedependent,ANSYSWorkben,chSi,TrainingManual,ThermalAnalysis,ThermalBoundaryConditionsTemperature-DependentConvection:

Select“NewConvection”fortheCorrelationThe“EngineeringData”tabwillopenandtheCoefficientTypecanthenbedefinedfortheconvectionloadDeterminewhattemperatureisusedforh（T）:

AveragefilmtemperatureT=（Tsurface+Tbulk）/2SurfacetemperatureT=TsurfaceBulktemperatureT=TbulkDifferenceofsurfaceandbulktemperaturesT=（Tsurface-Tbulk）,Selectthetemperature-dependencyfromthepull-downmenu,ANSYSWorkbenchSi,TrainingManual,ThermalAnalysis,ThermalBoundaryConditions,Tempera