TheoreticalcalculationofannularupwardflowinanarrowannuliwithbilateralheatingOriginalResearchArticle

Basedonseparatedflow,atheoreticalthree-fluidsmodelpredictingforannularupwardflowinaverticalnarrowannuliwithbilateralheatinghasbeendevelopedinpresentpaper.Thetheoreticalmodelisbasedonfundamentalconservationprinciples:themass,momentum,andenergyconservationequationsofliquidfilmsandthemomentumconservationequationofvaporcore.Throughnumericallysolvingtheequations,liquidfilmthickness,radialvelocity,andtemperaturedistributioninliquidfilms,heattransfercoefficientofinnerandoutertubesandaxialpressuregradientareobtained.Thepredictedresultsarecomparedwiththeexperimentaldataandgoodagreementsbetweenthemarefound.Withsamemassflowrateandheatflux,thethicknessofliquidfilmintheannularnarrowchannelwilldecreasewithdecreasingtheannulargap.Thetwo-phaseheattransfercoefficientwillincreasewiththeincreaseofheatfluxandthedecreaseoftheannulargap.Thatis,theheattransferwillbeenhancedwithsmallannulargap.Theeffectsofouterwallheatfluxonvelocityandtemperatureintheouterliquidlayer,thicknessofouterliquidfilmandouterwallheattransfercoefficientareclearandobvious.Theeffectsofouterwallheatfluxonvelocityandtemperatureintheinnerliquidlayer,thicknessofinnerliquidfilmandtheinnerwallheattransfercoefficientareverysmall;thesimilareffectsoftheinnerwallheatfluxarefound.Astheapplicationsofthepresentmodel,thecriticalheatfluxandcriticalqualityarecalculated.