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1、JoumalofFoodEngineering14(1991)71-82EvaluationofthePrecisionoftheModifiedFitchMethodforThermalConductivityMeasurementofFoodsMd.ShafiurRahmanDepartmentofFoodScienceandTechnology,TheUniversityofNewSouthWales,POBox1,Kensington,NSW2033,Australia(Received23May1990;revisedversionreceived1October1990;accep
2、ted10October1990)ABSTRACTAdevicewasdevelopedformeasurementofthermalconductivityofsolidfoodmaterialsaboveandbelowfreezing.ThesystemisamodtficationoftheFitchapparatus.Adisc-shapedsamplewithaconstantthicknessisplacedinthecompartmentbetweenacopperrodandacopperdisc.Thediscandrodactasaheatsourceandsink.Th
3、einstrumentwastestedandcalibratedbymeasuringthethermalconductivityofice,frozenchickenmeat(white),freshpotatoandapple.NOTATIONAContactareaofsampleanddiscs(m*)CSpecificheat(J/kgC)DSamplediameter(m)kThermalconductivityofsample(W/mC)1Compartmentthickness(m)MMass(kg)sF;p;;ithelineIn[(TO-T,)/(T-T,)]versus
4、ttTTemperature(C)oPercentageerrorSubscriptsCopperFModifiedFitchmethod71JournalofFoodEngineering0260-8774/91/$03.50-01991ElsevierSciencePublishersLtd,England.PrintedinGreatBritain72Md.S.Rahmun0InitialpProbemethodsSurfaceofthecopperrodINTRODUCTIONMeasurementofthermalconductivitypresentsmoreofachalleng
5、ethanmeasurementofotherthermalpropertiesbecausethermalconductivitydependsonthestructureorphysicalarrangementofthesample(voids,inhomogeneities,particle-to-particlecontact,etc.)aswellasonthechemicalcomposition.ManymeasurementtechniqueshavebeendiscussedbyMohsenin(1980),ReidyandRippen(1971)andMurakamian
6、dOkos(1989).Somewell-establishedstandardtechniques,suchastheguardedhotplate,workwellfornon-biologicalmaterials,butarenotwellsuitedforfoodsbecauseoflongtemperatureequilibrationtimes,moisturemigrationinthesampleandthelargesamplesizerequired(Sweat,1986).Thelineheat-sourcethermalconductivityprobeisrecom
7、mendedformostfoodapplication.Itissimpleandfastandrequiresrelativelysmallsamplesizes.But,itrequiresafairlysophisticateddataacquisitionsystem(Sweat,1986).Forthelinesourcemethod,asampleofatleastdiameter1
