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1、SolvedwithCOMSOLMultiphysics4.3aCirculatingFluidizedBedIntroductionThismodelsimulatestheoperationofacirculatingfluidizedbed.Inthisapparatusthedispersedphase,consistingofsolidsphericalparticles,isfluidizedbyagasandtransportedthroughaverticalriser.Uponreachin
2、gtheoutlet,thedispersedphaseisre-injectedinthevicinityofthegasinletatthebottomofthebed.Tostudytheflowinthefluidizedbed,themodelusestheEuler-Eulermodel.ThephasepropertiesandmodelsetupfollowthoseinRef.1.ModelDefinitionFigure1displaysthegeometryofthefluidizedb
3、ed,andschematicallydescribesitsmeansofoperation.Thefluidphase,consistingofair,isinjectedatthebottomofthebed.Thedispersedphase,particleswithadiameterof54μm,arefluidizedbythegasflowandtransportedupwards.Attheoutlet,particlesandgasexitthebed.Theparticlesarefed
4、backintothebedthroughre-injectioninletsontheverticalwallsnearthegasinlet.Thedispersedphasefluxmatchesthatattheoutlet,creatingacirculatingfluidizedbed.Table1summarizesthebedgeometriesandthepropertiesofthephases.ThevaluescorrespondtothoseusedinRef.1.TABLE1:FL
5、UIDIZEDBEDPROPERTIESPROPERTYVALUEParticlediameter54μm3Particledensity930kg/m3Gasdensity(air)1.2kg/m-53Gasdynamicviscosity(air)1.8·10kg/mGasinletvelocity1.52m/sBedwidth0.09mBedheight10.6m©2012COMSOL1
6、CIRCULATINGFLUIDIZEDBEDSolvedwithCOMSOLMultiphysics4.3aOut
7、letSolid/GasSolid/Gasre-injectionre-injectionGasinletFigure1:Schematicofthecirculatingfluidizedbed.Thegeometryisnottoscale.GOVERNINGEQUATIONSUsetheEuler-Eulermodeltosolvefortheflowofthecontinuousanddispersedphase.Bothphasesarethenmodeledasinterpenetratingco
8、ntinuagovernedbyaseparatesetofNavier-Stokesequations.Themodelalsoincludesatransportequationforthedispersed-phasevolumefraction.Fordetailsoftheequationsandassumptionsused,seethesectionTheoryfortheEuler-EulerModel,LaminarFlowInterfaceintheCFDModuleReferenceGu
9、ide.Tospecifythetransportpropertiesofthefluidizedbed,applythesettingsbelow.Theviscosityofthedispersedphaseisdefinedas(Ref.1)μ=0.5φ(1)ddwhereφisthedispersed-phasevolumefraction.d2
10、CIRCULATINGFLUIDIZEDBE
