Designation:D4612−08StandardPracticeforCalculatingThermalDiffusivityofRocks1ThisstandardisissuedunderthefixeddesignationD4612;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.1.Scope*1.1Thispracticeinvolvescalculationofthethermaldiffu-sivityfrommeasuredvaluesofthemassdensity,thermalconductivity,andspecificheatatconstantpressure.Itisapplicableforanymaterialswherethesedatacanbedeter-mined.Thetemperaturerangecoveredbythispracticeis20to300°C.NOTE1—Thediffusivity,asdeterminedbythispractice,isintendedtobeavolumeaveragevalue,withtheaveragingvolumebeing$2×10−5m3(20cm3).Thisrequirementnecessitatestheuseofspecimenswithvolumesgreaterthantheminimumaveragingvolumeandprecludesuseofflashmethodsofmeasuringthermaldiffusivity,suchasthelaserpulsetechnique.NOTE2—Thispracticeiscloselylinkedtotheoveralltestprocedureusedinobtainingtheprimarydataondensity,specificheat,andconduc-tivity.Itcannotbeusedasa“standalone”practicebecausethethermaldiffusivityvaluescalculatedbythispracticearedependentonthenatureoftheprimarydatabase.Thepracticefurnishesgeneralguidelinesbutcannotbeconsideredtobeall-inclusive.1.2ThevaluesstatedinSIunitsaretoberegardedasthestandard.Thevaluesgiveninparenthesesaremathematicalconversionstoinch-poundunitsthatareprovidedforinforma-tiononlyandarenotconsideredstandard.1.3Thepracticeisintendedtoapplytoisotropicsamples;thatis,samplesinwhichthethermaltransportpropertiesdonotdependonthedirectionofheatflow.Ifthethermalconductiv-itydependsonthedirectionofheatflow,thenthediffusivityderivedbythispracticemustbeassociatedwiththesamedirectionasthatutilizedintheconductivitymeasurement.1.4Thethermalconductivity,specificheat,andmassden-sitymeasurementsmustbemadewithspecimensthatareasnearidenticalincompositionandwatercontentaspossible.1.5Thegenerallyinhomogeneousnatureofgeologi...
