Walltemperaturemeasurementandheattransfercorrelationofturbulentsupercriticalcarbondioxideflowinverticalcircular/non-circulartubesOriginalResearchArticle

Experimentaldataarepresentedwhichdescribeheattransfercharacteristicsofturbulentsupercriticalcarbondioxideflowinverticaltubeswithcircular,triangular,andsquarecross-sections.Experimentsareconductedataconstantpressureof8MPaundervariousconditionssuchasinletbulktemperaturesrangingfrom15to32°C,imposedheatfluxesfrom3to180kW/m2,andmassvelocitiesfrom209to1230kg/m2s.ThecorrespondingReynoldsandGrashofnumbersareintherangeof3×104to1.4×105,and5×109to4×1011,respectively.Thetestsectioniscomposedofanentranceregionof0.6mlongandaheatingregionof1.2mlong.Walltemperaturesaremeasuredbythermocouplesinstalledattheoutersurfaceoftheheatingregion.Inordertoidentifytheeffectofthecross-sectionalshapeonthesupercriticalheattransfer,walltemperaturedistributionsinthestreamwisedirectionarecomparedatthesameheatfluxandmassvelocityconditions.Basedonthewalltemperaturedata,animprovedheattransfercorrelation,whichcanbeapplicabletobothforcedconvectionandmixedconvectionregimes,isproposed,andcomparedwithpreviousones.