ML19122A309
| ML19122A309 | |
| Person / Time | |
|---|---|
| Issue date: | 02/19/2019 |
| From: | Stephen Bajorek, Beck F, Cheung F, Garrett G, Grant G, Hoxie C, Jin Y, Kirk Tien NRC/RES/DSA/CDB, Pennsylvania State Univ, University Park, PA |
| To: | |
| Tien K | |
| References | |
| Download: ML19122A309 (4) | |
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STEADYSTATEPREDICTIONSOFREFLOODCHARACTERISTICSINARODBUNDLEGrantR.Garrett,YueJin,FaithR.Becky,Fan-BillCheung,StephenM.Bajorekx,KirkTienx,ChrisL.HoxiexNuclearEngineeringDepartment,127ReberBuilding,UniversityPark,PA16803,grg5094@psu.edu,yuj118@psu.edu,fxc4@psu.eduyMechanicalEngineeringDepartment,127ReberBuilding,UniversityPark,PA16803,frb115@psu.eduxOceofNuclearRegulatoryResearch,UnitedStatesNuclearRegulatoryCommission,Washington,D.C.20555,stephen.bajorek@nrc.gov,chris.hoxie@nrc.gov,kirk.tien@nrc.govINTRODUCTIONAccuratepredictionsoftwo-phasewphenomenaob-servedinthePennStateUniversity(PSU)/UnitedStatesNu-clearRegulatoryCommission(NRC)RodBundleHeatTrans-fer(RBHT)facilityweremadebyperformingaorderanalysisfromfundamentalthermalhydraulicandheattransferrelations.ThecalculationsweremadefromadevelopedscriptforEngineeringEquationSolver(EES).Thecalculationsper-formedarepartofanongoingeortinmodeldevelopmentandcodevalidationforphenomenon.Inthispaper,resultsfromordercalculationsarecomparedtoexperimentaldatafromthePSU/NRCRBHTfacility.ThefacilityisdesignedtorepresentasectionofaPWRcore.FurtherdetailsregardingtheRBHTfacilityarecoveredinthefollowingsection.Thecalculationsmadebytheorderanalysiscom-paredwellwithexperimentaldata.Assumptionsmadeduringtheanalysis,anduncertaintyintheexperimentscontributemosttothedierencesbetweencalculatedresultsandexperi-mentalmeasurements.NRC/PSURBHTFACILITYThissectioncoversthedetailsofthePSU/NRCRBHTfacility.Furtherdetailscanbefoundinthe"RodBun-dleHeatTransferTestFacilityDescription"(Hochreiter,2012).Figure1providesanisometricviewoftheRBHTfacilityand2providesaP&IDoftheRBHTfacility.Thefacility,whichcontains49vertical,3.66m(12ft)longtestrods(fourunheatedcornerrodsand45heatedrods)withInconel600claddingina7x7geometry,havingtheroddiameters,rodpitchesandspacergridscomparabletothoseincommercialPWRs,wasdesignedtoobtainfundamentalwandheattransferdataduringtransients.The45non-cornerrodsareelectronicallyheatedbyaheatingcoilinsideeachoftheheatedrods.Theexperimentsareperformedbyintroducingpowertotheheatedrodsandheatingupthetestsectionwithnoliquidphasewaterpresent.ThesystempressureiscontrolledbyaPIDcontroller.Whenthedesiredinitialconditionsaremet,water,atacontrolledtemperatureandtestsectioninletvelocityispumpedthroughthetestsection.Theexperimentsareperformeduntiltherodbundlecompletelyquenchesoratimeafterasteadystateconditionisachieved.Fig.1.IsometricViewofRBHTFacility(Hochreiter,2012)Fig.2.RBHTFacilityP&ID(Hochreiter,2012)EESSCRIPTDEVELOPMENTThissectionreviewstheorderapproachusedtode-veloptheEngineeringEquationSolver(EES)scriptusedtomakesteadystateRBHTpredictions.ThescriptdevelopedinEESisusedtopredictthesteadystatequenchheightinthebundleandthevaportemperatureattheexitofthebundleforvariousRBHTexperiments.Physically,liquidphasewaterwillenterthebottomofthetestsectionthroughthelowerplenum.Asthecoolantrisesthroughthebundleitwillremovepowerfromtheheatedrodsandheatup.Oncethebulkcoolanttemperaturereachesitssaturationvalue,nucleateboilingwill occur.Asthecoolantcontinuestowthroughthefacilitymoreboilingwilloccuruntilnearlyalloftheliquidinthecoolantisvaporizedandthevaporissuperheated.Topredictthesteadystatequenchlocation,itwasas-sumedthatallofthepowerfromtheheatedrodsoftheRBHTfacilitywastransferredtotheliquidwuntilalloftheliq-uidphaseisvaporized.SincethepoweroftheRBHTfacilityisknown,thepowerrequiredtocompletelyvaporizealloftheliquidinthecoolantcanmatchwiththeintegratedpoweroftheRBHTfacilitytoacertainheight.Itisexpectedthatthesteadystatequenchlocationshouldbenearthislo-cationbecausewhenthereislittletonoliquidinthecoolant,therodsinthefacilitycannolongerbequenched.Tomakethisprediction,thepowertoheatthecoolantfromitsfacilityinletvaluetoitssaturationvalueiscalculatedandaddedtoacalculatedpowerrequiredtocompletelyvaporizealltheliquidinthecoolantonceithasreacheditssaturationtemperature.Equation1isimplementedintotheEESscriptandusedtodeterminethepower,qslrequiredtoraisethetemperatureofthecoolantfromitstemperature,Tinletatthetestsectioninlettoitssaturationtemperature,Tsat.Equation2isimplementedintothesameEESusedtodeterminethepower,qlvrequiredtocompletelyvaporizetheliquidinthecoolantafterithasreacheditsbulksaturationtemperature.Inequations1and2,misthemasswrateofthecoolant,-cpistheheat,andhlvisthelatentheatofvaporization.Equations1and2implementedandsolvedinEES,withpropertiestakenfromthe"STEAM_IAPWS"database.qsl=m-cp(TsatTinlet)(1)qlv=mhlv(2)TopredictthesteadystatevaportemperatureattheexitoftheRBHTtestsection,anenergybalanceapproach,similartothatusedinthepredictionofthesteadystatequenchfrontlocationwasused.Sincethetotalbundlepower,qbundleisknownandthepowertocompletelyvaporizethecoolantiscalculatedinthepredictionofthesteadystatequenchfrontlocation,theexcesspower,qexcessinthebundlethatremainsafterallliquidinthecoolanthasvaporizedcanbedeterminedbysubtractingthesetwovalues.Forthepredictionofthesteadystatevaportemperatureattheexitofthebundle,itisassumedthatalloftheexcesspowerremaininginthebundleaftervaporizingalloftheliquidinthecoolantistransferredtothevapor.Equations3and4providetheequationsfortheexcesspowerinthebundleaftercompletelyvaporizingalltheliquidandthevaportemperature,Tvattheexitofthetestsectionrespectively.Inequation4,cpvistheheatofthevapor,foundinthe"STEAM_IAPWS"database.qexcess=qbundleqslqlv(3)Tv=Tsat+qexcessmcpv(4)UsingtheEESscriptdevelopedaccordingtotheapproachdescribedinthissection,predictionsweremadeforthesteadystatequenchfrontlocationandthesteadystatevaportemper-atureattheexitofthetestsectionformultipleexperiments.Theexperimentalconditionsandcomparisonofresultsaredescribedbelow.RESULTSANDANALYSISThissectionprovidesacomparisonoftheexperimentalresultsandpredictionsmadeusingaorderapproachviaadevelopedEESscript.Twoexperimentsareusedinthecomparisonofresults,EXP8095andEXP8100.TableIprovidesthetestconditionsforEXP8095andEXP8100.TABLEI.RBHTExperiments8095and8100ConditionsParameterEXP8095EXP8100Pressure,kPa(psia)275(40)275(40)InletCoolantVelocities,cm/s(timeafterrs)7.62(0-15)5.08(15-30)2.54(30-45)1.32(45-1812)7.62(0-15)5.08(15-30)2.54(30-45)1.32(45-550)1.22(550-1920)PeakPower,kW/ft0.40.4InitialPeakBundleTemperature,K(F)1033(1400)1033(1400)TestSectionInletSubcooling,K(F)24(43)24(43)Figures3and4provideacomparisonofthepredictedandexperimentallymeasuredsteadystatequenchfrontheightforEXPs8095and8100respectively.Alsoincludedintheseareexperimentalquenchlocationsprecedingthesteadystatequenchfronttoshowitsprogressionthroughtimeasitapproachesitssteadystateheight.Figures3and4showthatthesteadystatepredictionsofthequenchfrontlocationagreeswellwiththeexperimentaldataforbothEXP8095andEXP8100.Experimentally,thequenchfrontwilloscillateslightlyduetooscillatingbound-aryconditions.Forexample,experimentallythepressureisnotperfectlycontrolled,andpressureoscillationswilloccurthatwillcauseandcondensing.Thiswillresultinoscillationsinthequenchfront.Similarly,oscillationsinthetestsectioninletvelocityoccurthatwillsubsequentlyresultinquenchfrontlocationoscillations.
Fig.3.EXP8095QuenchFrontLocationFig.4.EXP8100QuenchFrontLocationFigure5providesacomparisonofthepredictedandexper-imentallymeasuredsteadystatevaportemperaturesattheexitofthetestsectionforEXPs8095and8100.Figure5showsthatthepredictionofthevaportemperatureattheexitofthebundleagreeswell,butonaverageisslightlyhigherthantheexperimentaldata.Forthepredictions,itisassumedthatthetestsectionisperfectlyinsulated.AlthoughinsulationisusedintheRBHTfacility,somefractionofenergyisstillconductedthroughtheinsulationandnottransferredtothecoolant.Thevaportemperatureattheexitofthebundleissensitivetoanypowerthatisconductedthroughtheinsulation.Also,experi-mentallyliquidthatcondensesintheupperplenumhasbeenshowntoenterthetestsectionattheexitofthetestsectionandactasaheatsinktothevapor.Also,liquiddropletscancontactthevaportemperatureprobesandcauselarge,nearlyinstantaneousdropsinthemeasuredvaportemperature.Sinceasmallchangeinpowercausesamuchlargerchangeinthetemperatureofvapor,ascomparedtoliquidphasewater,thecombinationoftheeectsexplainedarelikelythecauseoftheover-predictionofthevaportemperatureattheexitofthetestsection.ThediscrepancyinpredictedvsexperimentallymeasuredvaportemperatureattheexitofthetestsectionislargerforEXP8095thanforEXP8100.ForEXP8095,thesteadystatequenchfrontisatalocationclosertothesteamtemperaturemeasurementprobes.Thiscausesmoreliquiddropletstobeinthewatthemeasurementprobelocations,anddropletswillimpingeonthesteamtemperatureprobesatahigheraveragefrequencythanforEXP8100.Dropletimpingementonthesteamtemperatureprobecanbeseenin5byobservingthelargedropsintemperaturethatapproachthesaturationtemperatureoftheHighenoughdropletimpingementonthetemperatureprobesprohibitthemfromreachingasteadystatetemperaturethemselvesandregisteringanaccurateread-ingforthesteamtemperature.Thiscanbeseenin5fortheexperimentallymeasuredvaportemperatureforEXP8095byexaminingregionsthatarebetweendropletimpingements.Theseregionsaresteadilyincreasing,butarenotabletoreachasteadystatetemperaturebeforeanotherdropletimpingesonthesurfaceofthemeasurementprobe.SincetheaveragefrequencyofdropletimpingementonthevapormeasurementprobesislessforEXP8100,thetemperatureprobeitselfis abletoreachasteadystatetemperatureforcertaintimes.Ad-ditionally,liquiddropletsinthewwillcoolthevaporduetointerfacialheattransfer.ThevaporattheexitofthetestsectionwillexperiencemoreinterfacialheattransferforEXP8095thanforEXP8100becausetheinterfacialheattransferareawillbelargerforEXP8095(moredroplets).Fig.5.EXP8095andEXP8100SteadyStateVaporTempera-turesatexitofTestSectionCONCLUSIONSAorderstudywasusedtopredictsteadystatebe-haviorintheNRC/PSURBHTfacility.TheRBHTfacilityisdesignedtomodelasectionofaPWRcoreandwascallydesignedtoobtainfundamentalwandheattransferdataduringtransients.AnEESscriptwasdevelopedthatpredictedthesteadystatequenchfrontlocationandva-portemperatureattheexitoftheRBHTtestsectionusinganenergybalanceapproach.Forthepredictionofthesteadystatequenchfrontloca-tion,anenergybalancewasperformedtodeterminethepowerrequiredtocompletelyvaporizealloftheliquidinthew,assumingallpowerfromthebundlewastransferredtotheliquidphase.SincethepoweroftheRBHTfacilityisknown,thepredictionofthesteadystatequenchlocationcanbemadebytheheightinthebundlethatcorrespondedtothesametotalintegratedpowerfromthetestsectioninletasthecalculatedpowertocompletelyvaporizealloftheliquidinthecoolant.Thepredictedresultsfromusingthisapproachagreedwellwiththeexperimentaldata.Theexperimentalsteadystatequenchfrontlocationsoscillatedaboutthepre-dictedvaluesforbothEXP8095andEXP8100.Oscillatingexperimentalvaluesarecausedbynotperfectlycontrolledboundaryconditions.TopredictthesteadystatevaportemperatureattheexitoftheRBHTtestsection,itwasassumedthattheexcesspowerinthebundleaftervaporizingalloftheliquidinthecoolantwascompletelytransferredtothevaporinthecoolant.Theexperi-mentalsteadystatevaportemperatureattheexitofthebundleoscillatedbelowthepredictedvaluesforbothEXPs8095and8100andwereonaverageafewdegreeslowerthanthepre-dictedvalues.Experimentally,afractionofthepowerfromthebundleisconductedthroughtheinsulationandnottrans-ferredtothecoolant.Thisfractionofenergyisnotaccountedforinthepredictions.Also,unintendedliquidenteringthesystemthroughtheupperplenumactsasaheatsinkforthesuperheatedvapor.Additionally,liquiddropletscancontactthevaportemperaturemeasurementprobes.Thesefactorsarenotaccountedforinthesteadystatepredictionsmade.Oscillatingexperimentalboundaryconditionscontributetotheoscillationsseenintheexperimentalvaportemperaturemeasurements.Overallthepredictionofthesteadystateva-portemperatureattheexitofthebundleagreeswellwiththeexperimentaldata.ACKNOWLEDGMENTSTheworkperformedatthePennsylvaniaStateUniversitywassupportedbytheU.S.NuclearRegulatoryCommissionunderContractNumber:NRC-HQ-60-16-T-0002.REFERENCESHochreiter,et.al.,(2012),"RBHTHeatTransferEx-perimentsDataandAnalysis,"ThePennsylvaniaStateUni-versity,U.S.NuclearRegulatoryCommission,NUREG/CR-6980.