简介:Microcalorimetrywasdevelopedtodeterminethermalconductivities(λ)ofthermalinsulatorswithhollowcylindricalshapes,Aspecialdeviceofspecimentwithresistancethreadswrappedonitssurfaceandelectricheaterplacedinitsholewasdesignedtomeettheneedsofdeterminingλwithoutusingstandardsubstancestocalibratetheinstrument.Aformulaforcalculatingthevalueofλwasderived.Byheatingintheholeandonthesurfaceofthespecimenrespectively,thevaluesofλcanbeobtainedconvenientlybythistechnique.Themethodwastestedwithteflon,plexiglass,quartzglassandp[olyethylene.Theexperimentalvaluesofλforthefoursubstancesagreewellwiththeliteraturesones.Erroranalysiswasalsomadeontheexperimentaldata.Itwasfounrthatthemainfactorsaffectingvaluesofλare:(1)Theerroreofdeterminingthevaluesofheatcumulatedinspecimenandmaterialsinthespacearounditand(2)theerroreofdeterminingthevaluesofinnerandouterradiiofcylindricalspecimen.λ
简介:Theeffectivethermalconductivityofcompositeswithellipsoidalfillersisanalyzedbyusingahomogenizationmethodthatisabletorepresentthemicrostructureprecisely.Inthisstudy,variousparameterssuchasthevolumefraction,shape,anddistributionofthefillerarequantitativelyestimatedtounderstandthemechanismsofheattransferinthecomposite.First,thermalboundaryresistancebetweenresinandfillerisimportantforobtainingcompositeswithhigherthermalconductivity.Second,theanisotropyoftheeffectivethermalconductivityarisesfromcontactbetweenfillerinthecaseofellipsoidalfillerandproduceslowerthermalresistance.Finally,thefillernetworkandthermalresistanceareessentialfortheheattransferincompositesbecausethepathofthermalconductionisimprovedbycontactbetweenneighboringfillerparticles.
简介:AdsorptionequilibriumexperimentsofphenolontheNKAIIresinareseparatelyconductedinthepresenceandabsenceofultrasoundatambienttemperature.Theisothermofphenolonthepolymeradsorbentinthepresenceofultrasonicfieldisfirstlyreported.Resultsindicatedthattheisothermofphenoldeterminedinthepresenceofultrasoundislowerthanthatintheabsenceofultrasound.Inaddition,experimentsalsoshowthattheuseofultrasoundtotheadsorptionsystemofthephenolaqueoussolutionandNKAⅡresincouldcausetherisingofthetemperatureofthesystemintheorderof6^-C.TheeffectofultrasoundontheisothermofthephenolontheNKAⅡresinmostlyascribestothethermaleffectandthenon-thermaleffectofultrasonicfield.andtheroleofthelaterisgreaterthanthatoftheformer.
简介:Residualstressevolutionregularityinthermalbarrierceramiccoatings(TBCs)underdifferentcyclesofthermalshockloadingof1100℃wasinvestigatedbythemicroscopicdigitalimagecorrelation(DIC)andmicro-Ramanspectroscopy,respectively.Theobtainedresultsshowedthat,asthecyclenumberofthethermalshockloadingincreases,theevolutionoftheresidualstressundergoesthreedistinctstages:asharpincrease,agradualchange,andareduction.TheextensionstressneartheTBCsurfaceisfasttransformedtocompressiveonethroughjustonethermalcycle.Afterdifferentthermalshockcycleswithpeaktemperatureof1100℃,phasetransformationinTBCdoesnothappen,whereasthegeneration,development,evolutionofthethermallygrownoxide(TGO)layerandmicro-cracksarethemainreasonscausingtheevolutionregularityoftheresidualstress.
简介:Acomprehensivetreatmentoffractureoffunctionallygradedmaterials(FGMs)isprovided.Itisassumedthatthematerialpropertiesdependonlyonthecoordinateperpendiculartothecracksurfacesandvarycontinuouslyalongthecrackfaces.Byusingalaminatedcompositeplatemodeltosimulatethema-terialnon-homogeneity,analgorithmforsolvingthesystembasedonLaplacetransformandFouriertransformtechniquesispresented.Unlikeearlierstudiesthatconsideredcertainassumedpropertydistributionsandasinglecrackproblem,thecurrentinvestigationstudiesmultiplecrackproblemintheFGMswitharbitrarilyvaryingmaterialproperties.Transientthermalstressesarepresented.
简介:Thethermalprotectionperformanceofsuperalloyhoneycombstructureinhigh-temperatureenvironmentsareimportantforthermalprotectiondesignofhigh-speedaircrafts.Byusingaself-developedtransientaerodynamicthermalsimulationsystem,thethermalprotectionperformanceofsuperalloyhoneycombpanelwastestedinthispaperatdifferenttransientheatingratesrangingfrom5℃/sto30℃/s,withthemaximuminstantaneoustemperaturereaching950℃.Furthermore,thethermalprotectionperformanceofsuperalloyhoneycombstructureundersimulatedthermalenvironmentswascomputedfordifferenthighheatingratesbyusing3Dfiniteelementmethod,andacomparisonbetweencalculationalandexperimentalresultswascarriedout.Theresultsofthisresearchprovideanimportantreferenceforthedesignofthermalprotectionsystemscomprisingsuperalloyhoneycombpanel.
简介:由测试melt索引(MI),张力的力量;碎延期比率,polyoxymethylene(POM)的热变老率被分析;比较。表面形态学;POM表面的功能组的类型被观察;由SEM分析了;XPS。结果证明MI在120°C与变老的时间逐渐地珍视增加,显示热氧化分解occurrs慢慢地。在张力的力量上的20天的热变老的效果;打破POM的延期比率不是明显的,证明变老POM是相当一个长过程。在以后105天,裂开的热变老;POM表面上的搽粉的occurr。XPS决心以前显示出样品的C1s系列;在变老以后,包括C-C的二座山峰;公司,当在变老以后C-C的内容减少时;公司的内容增加,显示POM的热变老主要是碎;C-C债券分解。原来的样品的O1s/C1s比率是56.98%;在105天的热变老以后,比率是72.92%。
简介:Anoveltheoreticalmodelofthermaldiffusionhasbeenestablishedtostudythermalinteractionbetweentwoneighboringdiodsinsemiconductorlaserarrays.Themaincauseoftheocurrenceofthethermalinteractionbetweentwoneighboringdiodesinarraydevicesistheheatconductionthroughheatsink.Weholdthatasthedevicesmusyhaveheatsinktodiffuseheat,thiskindofinteractioninthearraywouldalwaysexist.However,whenthepitchbetweentwoneighboringdiodesinthearrayisreasonablydefined,thistroublesomethermalinteractioncanbesimplyreducedbyusingourmodel.Basedontheindividualdiodeswithleakywaveguidestructure,weexperimentallysucceededinfabricating2D4×4arrays.Thethermalinteractionbetweenupperandlowerdiodesinthe2Darrayisalsoconsideredaswellasthefunctionoftheheatsink.Themeasuredresultsshowthatthepulsepeakoutputpowerofthe2D4×4arrayishighupto11W.
简介:Transientmagneticcircuitmethodisadoptedtocalculatethepowerlossinwindingandshadingcoil.BasedontheanalysisofheattransferprocessinACcontactor,athermalmodelisproposedandthetemperaturefielddistributionissimulatedwith3-DFEMofANSYS.Comparisonofsimulationresultswithmeasurementsshowsthattheproposedmethodiseffective.
简介:ThethermalstabilityofNewZealandculturerabbitmusclealdolasewasinvestigatedbydifferentialscanningcalorimetryinthewatercontentrange0.23-3.70gwaterpergprotein.Theexperimentalresultsshowedthatatwatercontentsbelow0.47g/g,anendothermicpeakwasobservedandatwatercontentsabove0.57g/g,anendothermicandanexothermicpeakwerebothobservedonDSCthermogram.Thermaldenaturationresultoftheenzymeandtherelationshipbetweentwotransitiontemperaturesandwatercontentswerefirstreportedinthispaper.Uptonowwehavenotseenanysimilarreportsconcerningtheexothermictransition.
简介:Toensureareliableoperationofthe2.5MWgasturbineengine(GTE-2.5)withtheinletgastemperatureTIT=1623K,studieswereperformedoverthethermalstateofthenozzleguidevanesandrotorbladeswiththetemperatures,ratesandflowsoftheworkingmediaandcoolingairsimulatingallthepotentialturbinestageoperatingduties.Thesteadystateandthermal-cyclictestshavingbeenaccomplished,therewasnovisibledefectontherotorbladesandthenozzlevanes.Afterwards,theysurvivedtheendurancetestsattheratedcooling.Therefore,thefunctionalityoftheshellthin-wallhybridnozzlevanesandrotorbladesunderthevariableoperatingdutiesofthegasturbineatthe'shock'and'cyclic'loadsoftheworkingmediatemperaturevariationshasbeendemonstrated.
简介:Thelocalthermalconductivityofpolycrystallinealuminumnitride(AlN)ceramicsismeasuredandimagedbyusingascanningthermalmicroscope(SThM)andcomplementaryscanningelectronmicroscope(SEM)basedtechniquesatroomtemperature.ThequantitativethermalconductivityfortheAlNsampleisgainedbyusingaSThMwithaspatialresolutionofsub-micrometerscalethroughusingthe3ωmethod.Athermalconductivityof308W/m·Kwithingrainscorrespondingtothatofhigh-puritysinglecrystalAlNisobtained.Theslightdifferencesinthermalconductionbetweentheadjacentgrainsarefoundtoresultfromcrystallographicmisorientations,asdemonstratedintheelectronbackscattereddiffraction.Amuchlowerthermalconductivityatthegrainboundaryisduetoimpuritiesanddefectsenrichedinthesesites,asindicatedbyenergydispersiveX-rayspectroscopy.
简介:Asimplifiedmathematicalmodelwascreatedformeasurementofthermalexpansioncoefficientsofthinsheetmaterialswithholographictechnique.Experimentalset-upscorrespondingtothemathematicalmodelweredesignedandbuiltforbothtestsaboveroomtemperatureandatlowtemperatures.Afringecontroltechniquewasintroducedforlowtemperaturemeasurementstocompensaterigidbodymovement,THinsheetspecimensofsiliconandaluminumalloy(7075)weretestedwiththedevelopedtechnique.Thetestedresultsareingoodagreementwithreporteddataandthusverifythevalidityofthedevelopedtechnique.TheThermalexpansioncoefficientsofthetestedmaterialsrangedfrom2.5×10^-60C^-1to23.6×10^-6oC^-1.