CFX-Multiphase-12.0-WS07-Wall-Boiling

WS7-1ANSYS,Inc.Proprietary©2009ANSYS,Inc.Allrightsreserved.September1,2009Inventory#CFXMultiphase12.0Workshop7WallBoilingModelWS7:WallBoilingWS7-2ANSYS,Inc.Proprietary©2009ANSYS,Inc.Allrightsreserved.September1,2009Inventory#WorkshopSupplementSubcooledWallBoilingModel•Forsubcooledflowswithsuperheatedwalls,standardthermalphasechangemodelsforbulkboiling/condensationwillunderpredictrates-bubblesformattinynucleationcavitiesonwallsandgrow•TheRPIWallBoilingmodelprovidesamechanisticmodelforwalldrivenboiling-originallydevelopedbyPodowskiandco-workers•TheRPIwallboilingmodelisfullyreleasedinANSYSCFX12.0WS7:WallBoilingWS7-3ANSYS,Inc.Proprietary©2009ANSYS,Inc.Allrightsreserved.September1,2009Inventory#WorkshopSupplementBoilingFlowRegimessubcooledflowbubblyflowslugflowTsatTxwalltemperaturemeanfluidtemperaturesubcooledboilingnucleateboiling(saturatedboiling)annularflowsprayflowWS7:WallBoilingWS7-4ANSYS,Inc.Proprietary©2009ANSYS,Inc.Allrightsreserved.September1,2009Inventory#WorkshopSupplementWallHeatFluxPartitioning•Whenbubblesformataheatedwallinsubcooledboiling,therearedifferentmechanismsforheattransferfromthewalltothefluid:–ConvectiveHeatTransfer–QuenchingHeatTransfer–EvaporativeHeatTransferWS7:WallBoilingWS7-5ANSYS,Inc.Proprietary©2009ANSYS,Inc.Allrightsreserved.September1,2009Inventory#WorkshopSupplementEQFWallqqqqconvectiveheatflux1()FFWLqAhTTevaporationheatfluxEGLqm(hh)quenchingheatflux2()QQWLqAhTTut*m*my1A2A2AQuenchingheatflux*mConvectiveheatfluxMechanisticwallheatpartioningmodel:RPIWallBoilingModelWS7:WallBoilingWS7-6ANSYS,Inc.Proprietary©2009ANSYS,Inc.Allrightsreserved.September1,2009Inventory#WorkshopSupplement•A1=wallareafractionwhichdoesnotfeelthepresenceofthevaporphase–convectiveheatfluxsimilartosinglephaseturbulentflows:qF=A1hF(Tw–TL)[liquidheattransfer]•A2=wallareafractionaffectedbyvaporqE=m(hg–hL)qQ=A2hQ(TW–TL)[liquidheattransferbetweenbubbledepartureandnextbubble]WallHeatFluxPartitioning...WS7:WallBoilingWS7-7ANSYS,Inc.Proprietary©2009ANSYS,Inc.Allrightsreserved.September1,2009Inventory#WorkshopSupplementTestCase:Bartolomejetal.(1967)•VerticalPipe:D=15.4mmL=2m•qw=570,000W/m2•P=4.5MPa•G=900kg/m2/s•InletSubcooling=58.2K•Theentireouterradialwallofthepipeisheatedat570,000W/m2HeatedWallWS7:WallBoilingWS7-8ANSYS,Inc.Proprietary©2009ANSYS,Inc.Allrightsreserved.September1,2009Inventory#WorkshopSupplementImportingtheMesh•Tosavetime,anaxisymmetricmeshwithasingleelementinthethetadirectionwillbeused•StartCFX-Preandcreateanewsimulation(File/NewCase/General).IntheOutline,right-clickonMeshandselectImportMesh/CFXMesh,thenchoosepipemesh.gtmfromtheWorkshopexamplesfolderandclickOpenWS7:WallBoilingWS7-9ANSYS,Inc.Proprietary©2009ANSYS,Inc.Allrightsreserved.September1,2009Inventory#WorkshopSupplementComputationalMeshWS7:WallBoilingWS7-10ANSYS,Inc.Proprietary©2009ANSYS,Inc.Allrightsreserved.September1,2009Inventory#WorkshopSupplementFlowAnalysisI•NotethatFlowAnalysis1appearsintheOutlineTree.Clickonthe+signnexttothisentrytoexpanditandnotethataDefaultDomainhasbeencreatedforthemeshyouimportedWS7:WallBoilingWS7-11ANSYS,Inc.Proprietary©2009ANSYS,Inc.Allrightsreserved.September1,2009Inventory#WorkshopSupplementCCLFileImport•Inordertoshortentheset-uptimeforthistutorial,aCCLfilewhichsetsupexpressionsforvariousparametersintheRPImodelaswellasthedefinitionofsaturatedliquidandvaporwaterpropertiesat4.5MPawillbeimportedfromaCCLfile.•FromtheFilemenu,selectImportCCL,entertherpiexample.cclasthefilename(locatedintheinput-filesfolderforthiscourse),andclickOpen.•YouwillseeadditionstotheExpressionsandMaterialsentriesintheOutline.WS7:WallBoilingWS7-12ANSYS,Inc.Proprietary©2009ANSYS,Inc.Allrightsreserved.September1,2009Inventory#WorkshopSupplementImportedExpressionsEXPRESSIONS:Tsub1=-5.0[K]Tsub2=13.5[K]TsubMean=0.5*(Tsub1+Tsub2)TsubScale=4.0[K]SaturTemper=530.65[K]TsubL=SaturTemper-Liquid.TTanhArgum=(TsubL-TsubMean)/TsubScaleTanhBlend=1.0/(1.0+exp(TanhArgum))diam2=0.15E-3[m]diam1=2.00E-3[m]BubbleDiam=TanhBlend*(diam1-diam2)+diam2MinVFforArea=1.E-7ArDen1=6.0*max(Vapour.vfc,MinVFforArea)/BubbleDiamMaxVFforArea=0.8ArDen1Max=6.0*MaxVFforArea/BubbleDiamArDen2=ArDen1Max*max(1.0-Vapour.vfc,MinVFforArea)/(1.0-MaxVFforArea)BlendArDen=-2.0AreaDensity=(ArDen1^BlendArDen+ArDen2^BlendArDen)^(1.0/BlendArDen)CpGas=4.206E+3[Jkg^-1K^-1]CpLiq=4.922E+3[Jkg^-1K^-1]DenGasRef=22.696[kgm^-3]DenLiqRef=7.879E2[kgm^-3]kGas=0.05322[W/m/K]kLiq=0.606735[W/m/K]visGas=1.86E-5[kgm^-1s^-1]visLiq=1.07E-4[kgm^-1s^-1]MinVolFrac=1.E-15PressureLevel=4.5E+6[Pa]ReferEnthGas=1.6576e6[Jkg^-1]ReferEnthLiq=0.0[Jkg^-1]ReferTemper=SaturTemperSubcoolLiq=58.2[K]TemperGasIni=SaturTemperTemperLiqIni=SaturTemper-SubcoolLiqVfGasIni=MinVolFracVfLiqIni=1.0-VfGasInidTsub=Tsub2-Tsub1ENDWS7:WallBoilingWS7-13ANSYS,Inc.Proprietary©2009ANSYS,Inc.Allrightsreserved.September1,2009Inventory#WorkshopSupplementImportedMaterialsMATERIAL:liquidMaterialDescription=LiquidPhaseMaterialGroup=UserOption=PureSubstanceThermodynamicState=LiquidPROPERTIES:Option=GeneralMaterialThermalExpansivity=2.1E-04