美国N有关半导体热电制冷器TEC的PPT

[e-mail]-ElectricCoolersNASAGSFCThermal&FluidsAnalysisWorkshopTFAWS2011August15-19,2011NASALangleyResearchCenterNewportNews,VATFAWSShortCourseOverview•Introduction•PrinciplesofOperation–Somebackgroundinsemiconductors•DesignInformation–DesignConsiderations–Walk-throughExamples•RealLifeProjects–EarlyUseonSatellite–Hubble–ST-8LHPTFAWS–August15-19,20112Acknowledgments•FundamentalinformationonThermo-ElectricCoolerspresentedhereinhasbeenextractedfromseveralsources,allofwhichareavailableinthepublicdomain.Alistofwebsitesusedisincludedinthereferences.TFAWS–August15-19,20113ManythanksgotoDr.JentungKu(NASAGSFC)fortheinformationfromhispapersonthistopic,andtoDavidSteinfeldforhisgarage-builtTEC“experiment”.Overview•Thethermoelectriceffectisthedirectconversionoftemperaturedifferencestoelectricvoltageandvice-versa.–Athermoelectricdevicecreatesavoltagewhenatemperaturedifferenceisappliedtoit.–Conversely,whenavoltageisappliedtoit,itcreatesatemperaturedifference.TFAWS–August15-19,20114WhyUseThem?•Pros:–Unlikecommonheatpumps(compression/expansion-basedandStirlingcycle),thesedeviceshavenomovingpartsandworkinanyorientation•simple,reliable,compact,lowmass,andnoiseless,vibration-lessoperation.–Lessmaintenance-morethan100,000hoursoflifeforsteadystateoperation–Functioninenvironmentsthataretoosevere,toosensitive,ortoosmallforconventionalrefrigeration–Containsnochlorofluorocarbonsorothermaterialswhichmayrequireperiodicreplenishment•Temperaturecontroltowithinfractionsofadegreeusingappropriatesupportcircuitry.–LowthermalmassandfastresponsetimeofTECs,whencombinedwithanappropriatecontrolloop,canprovideprecisetemperaturecontrol.Inrelativelystablethermalsinkenvironments,TECsachieve0.01°Ctemperaturestability.Suchextremestabilityisdifficulttoachievebyothermeans.–Thedirectionofheat-pumpingisfullyreversible.ChangingthepolarityoftheDCpowersupplycausesheattobepumpedintheoppositedirection,i.e.-acoolercanbecomeaheater.–Temperaturedifferences:•forahotsidearoundroomtemperature,temperaturedifferencesofabout72°Cand125°Ccanbeachievedbysingle-stageandmultistageTECs,respectively.•InsituationswheretheobjectbeingcooledgenerateslittleornoheatthecombinationofTEcoolingandthermalinsulationcanproducelargetemperaturedifferences.•Cons:–structuralintegrityofbismuthtellurideandsolderedjointswhensubjectedtodifferentialthermalexpansionstresses.–relativelylowCOP,particularlywithlargetemperaturedifferences.•thiscanbeacceptablewhentheheatloadissmall.•bestsuitedtosituationswithmodestheatloads,coldtemperaturesnotbelow150°K,andhot-to-cold-sidedifferencesnotexceeding100°C.•notrecommendedforusebelow130°Kbecauseoftheirprohibitivelylowefficiencies.TFAWS–August15-19,20115ThermoelectricEffects•Threeseparatetheoriesbehindtheoperationofthermoelectriccoolingfirstappearedinthe1800s.TFAWS–August15-19,20116•Seebeckeffect:AlessandroVoltaandThomasJohannSeebeck(1821)foundthatholdingthejunctionsoftwodissimilarconductorsatdifferenttemperaturescreatesanelectromotiveforceorvoltage.Thisisthebasisforthermocouples.•Peltiereffect:Jean-CharlesPeltierdiscovered(1834)aheating/coolingeffectwhenpassingelectriccurrentthroughthejunctionoftwoconductors.•Thomsoneffect:WilliamThomson(LordKelvin)showed(1851)thatoveratemperaturegradient,asingleconductorwithcurrentflowinginithasreversibleheatingandcooling.NotethatthePeltiereffectistheinverseoftheSeebeckeffect.SoWhatTookSoLongToUseThem-TECEvolution•Althoughtheseprincipleswerediscoveredinthe1800’s,mostearlyworkwasonmetalalloys,notthermoelectriccompounds.itwasn’tuntiltheintroductionofsemiconductormaterialsinthelate1950’s,thatthermoelectriccoolingbecameaviabletechnologyfor[small]coolingapplications.•ThecharacteristicsofTECsmakethemhighlysuitableforprecisetemperaturecontrolapplicationsandwherespacelimitationsandreliabilityareparamountorrefrigerantsarenotdesired.•TECshaveseveraladvantagesovercompetingtechnologies,including:–highreliabilitypotential–noise-freeoperation–vibration-freeoperation–scalability–orientation-independenceandcompactness(highenergydensity).•Basedontheseadvantages,TECsnowdominatecertainapplications,andnewbenefitscontinuetoemerge.•TECsinspacehavebecomerelativelycommon;theyprovidetemperaturecontrolforlownoiseamplifiers(LNAs),startrackers,andIR(infrared)sensors.TFAWS–August15-19,20117SeebeckEffect•Thevoltagedifference,V,producedacrosstheterminalsofanopencircuitmadefromapairofdissimilarmetals,AandB,whosetwojunctionsareheldatdifferenttemperatures,isdirectlyproportionaltothedifferencebetweenthehotandcoldjunctiontemperatures,THOT–TCOLDV=α(THOT-TCOLD)whereα=Seebeckcoefficient•Thetemperaturedifference,producesanelectricpotential(voltage)thatcandriveanelectriccurrentinaclosedcircuit.•UsingtheSeebeckeffect,thermoelectricpowergeneratorsconvertheattoelectricity.–Veryinefficient–Usedwhenwasteheatisreadilyavailable,orinremoteareaswheredependabilityoverridesefficiencyTFAWS–August15-19,20118PeltierEffect•Whenanelectriccurrentflowsthroughtwodissimilarconductors,dependingonthedirectionofthecurrentfl