Heattransferintwo-componentinternalmistcooling:PartI.ExperimentalinvestigationOriginalResearchArticle

Anexperimentalinvestigationwasconductedtoexaminesteady,internal,nozzle-generated,gas/liquidmistcoolinginverticalchannels.Theidealprimarycoolingmechanisminthissituationissurfaceevaporationofanultra-thin,subcooledliquidfilmthatformsontheheatedsurface.Theaimwastoquantifytheeffectsofvariousoperatinganddesignparametersonthecoolingeffectiveness.Parameterstestedincludedtheliquidatomizationnozzledesign,inletflowcondition(liquidmassfraction;carriergasvelocity,temperatureandhumidity;liquidtemperature;liquiddropletsizedistribution;andgas/liquidcombination),channelcharacteristics(cross-sectiongeometry,lengthandsurfacewettability),andflowdirection.Interestinthisresearchhasbeenmotivatedbytheneedforahighlyefficientcoolingmechanisminhigh-powerlasersforinertialfusionreactorapplications.Afullyinstrumentedexperimentaltestfacilitythatincludedthreecylindricalandtworectangularelectricallyheatedtestsectionswithdifferentcross-sectionsandunheatedentrylengthswasused.Thechannelhydraulicdiameterscoveredtherange16–26.7mm,andtheheatedlength-to-hydraulic-diameterratiovariedintherangefrom23.3to51.Waterwasusedasthemistliquid,withairorheliumasthecarriergas.Threetypesofmistgeneratingnozzleswithsignificantlydifferentspraycharacteristicswereused.Localheattransfercoefficients,definedbasedonthetemperaturedifferencebetweentheheatedsurfaceandthebulkgas,wereobtainedalongthechannelsforawiderangeofoperatingconditions.Thedataindicatethatmistcoolingcanincreasetheheattransfercoefficientbymorethananorderofmagnitudecomparedtoforcedconvectionusingonlythecarriergas.