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Laboratory techniques to evaluate thermal conductivity for some soils

导热系数,热物理性质

HeatandMassTransfer39(2003)119–123DOI10.1007/s00231-002-0295-x

Laboratory techniques to evaluate thermal conductivity for some soils

Laboratory techniques to evaluate thermal conductivity for some soils

Laboratorytechniquestoevaluatethermalconductivityforsomesoils

O.K.Nusier,N.H.Abu-Hamdeh

119

AbstractThethermalconductivityoftwosoilswasin-vestigatedthroughlaboratorystudies.Theselaboratoryexperimentsusedthesingleprobeanddualprobemeth-odstomeasureandcomparethermalconductivities.Thesoilsusedwereclassi edassandandloam.Thermal

conductivitymeasuredusingsingleprobemethodrangedfrom0.95to2.11forsandandfrom0.49to0.76W/mKforloam.Thermalconductivitymeasuredusingdualprobemethodrangedfrom0.98to2.17forsandandfrom0.51to0.78W/mKforloam.Finally,itwasfoundthatsandhadhighervaluesofthermalconductivitythanloamforallsoilconditionsstudied.

DTmqc

maximumtemperaturechangeatadistancerfromtheheater,K

volumetricheatcapacity,J/m3K

Greeksymbolskthermalconductivityofthematerial

surroundingthelinesource,W/mK

jthermaldiffusivity,m2/s

1

Introduction

NomenclatureSoilthermalpropertiesarerequiredinmanyareasof

engineering,agronomy,andsoilscience,andinrecentdconstantperatureduringcoolingafter

yearsconsiderableefforthasgoneintodevelopingtech-–Ei(-x)exponentialintegral

niquestodeterminetheseproperties.Thermalconduc-Icurrentinthelinesource,A

tivityisconsideredoneofthemostimportantthermalq¢energyinputperunitlengthofheaterper

propertiesofplantenvironment.Itisconsideredastheunittime,W/m

propertythatcontrolsheat owthroughmaterialsofRspeci cresistanceofthewire,X/m

differenttypes.rdistancebetweenelectrodes,m

Thethermalconductivityofasoildependsonseveral

Sslopeofthestraight-lineportionofthe

factors.Thesefactorscanbearrangedintotwobroad

temperatureriseorfallversusln(t)

groups,thosewhichareinherenttothesoilitself,and

Tsensortemperature,C°thosewhichcanbemanagedorcontrolled,atleasttoaToinitialtemperature,C°certainextentbyhumanmanagement.Thosefactorsorttime,secondspropertiesthatareinherenttothesoilitselfincludethethheatingtimeafterwhichcoolingwouldstart,textureandmineralogicalcompositionofthesoil.Factors

secondsin uencingasoil’sthermalconductivitythatcanbe

toheatpulseduration,secondsmanagedexternallyincludewatercontentandsoilbulktmtimeatwhichDTmisrecorded,secondsdensity.Thewayasoilismanagedwillplayanimportant

partindeterminingitsthermalconductivity.Anypracticeorprocesswhichtendstocausesoilcompactionwillin-Received:28November2000creasebulkdensityanddecreaseporosityofasoil.ThisinPublishedonline:17April2002turnwillhaveasigni canteffectonthermalconductivity.ÓSpringer-Verlag2002

Acertainsoilwillnotnecessarilyhaveagivenvalueofthermalconductivityunlessallofthefactorsareap-O.K.Nusier

proximatelythesamewheneverthemeasurementsareAssistantprofessor.CivilEngineeringDepartment.,

taken.JordanUniversityofScienceandTechnology,

P.O.Box3030,Irbid,JordanThermalpropertiescanbedeterminedindirectlybyE-mailaddress:nosama@just.edu.jomeasuringtheriseorfalloftemperatureinresponseto

heatinputtoalinesourceatthepointofinterest[1,2,3,4,N.H.Abu-Hamdeh(&)

Associateprofessor.AgriculturalEngineeringandTechnology5].DeVries[6,7]developedmodelsthatallowestimationDepartment.,JordanUniversityofScienceandTechnology,ofthermalconductivityandvolumetricheatcapacityofP.O.Box3030,Irbid,Jordan

soilsfromthevolumefractionsoftheirconstituentsandE-mail:nidal@just.edu.jo

theshapeofthesoilparticles.Thedual-probeheat-pulsetechnique[8,9,10,11]hasalsobeenusedtomakeCorrespondenceto:NidalH.Abu-Hamdeh

measurementsofsoilthermalproperties.ItconsistsoftwoPostalCode21110,

P.O.Box422,Irbid-Jordanparallelneedleprobesseparatedbyadistance(r).One

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