ASHRAE.4612-2003 Comparison of Four Models for Thermal Response Test Evaluation

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1、4612ComparisonofFourModelsforThermalResponseTestEvaluationSignhildE.A.GehlinGöranHellström,Ph.D.,P.E.AssociateMemberASHRAEABSTRACTSinceitsintroductionin1995-1996,thisin-situmethodhasspreadtomostcountrieswhereboreholesinthegroundareFourtwo-variableparameterestimati

2、onmodelsforeval-usedasaheatsource/sinkonalargerscale.Themethodservesuationofthermalresponsetestdataarecomparedwhenprimarilytoassessthegroundthermalconductivityandappliedonthesametemperatureresponsedata.Twomodelsperformanceofdifferentboreholeheatexchangerdesigns,ar

3、ebasedonline-sourcetheory,thethirdmodelisacylinder-whichareimportantforoptimaldesignandqualitycontrol.source-basedsolution,andthefourthisanumericalone-Themethodisdescribedinseveralpapers,e.g.,Gehlin(1998),dimensionalfinitedifferencemodel.ThedatasetscontainAustin(1

4、998),Austinetal.(2000),ShonderandBeck(2000),measuredtemperatureresponse,heatload,andundisturbedandKavanaughetal.(2000).Theprincipleofathermalgroundtemperaturefromthreethermalresponsetests,responsetestsetupisoutlinedinFigure1.togetherwithphysicaldataofthetestedbore

5、holeheatexchangers(BHE).ThemodelsestimategroundthermalTheboreholetemperatureresponseisthetemperatureconductivityandthermalresistanceoftheBHEandaredevelopmentovertimeoftheheatcarrierfluidcirculatingcomparedregardingtestlengthanddataintervalused.Forthethroughthebore

6、holeheatexchangerwhenaknownheatingorthreedefineddatasets,thelinesourceapproximationmodelcoolingloadisimposed.Byevaluatingtheincreasingfluidshowstheclosestagreementwiththemeasuredtemperatureresponse.Thecylindersourceandnumericalmodelsshowsensitivitytotheinclusionof

7、earlydata.Arecommendedmini-mumresponsetestdurationof50hoursisconcludedfromthemodelcomparison.INTRODUCTIONDuringathermalresponsetest,adefinedthermalloadisappliedtoaboreholeheatexchangerandthetemperaturedevelopmentoftheinletandoutlettemperaturesaremeasuredovertime.T

8、histemperatureresponseallowsextrapolationofthethermalbehaviorinfuturetime.Onepossibleconceptualmodelfortheinterpretationistoassumethegroundtobeaconducti