美国N有关半导体热电制冷器TEC的ppt课件.ppt

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1、Presented ByEric W.GrobNASA Goddard Space Flight CenterEric.W.Grobnasa.govThermo-Electric Coolers NASA GSFCThermal&Fluids Analysis WorkshopTFAWS 2011August 15-19,2011NASA Langley Research CenterNewport News,VATFAWS Short Course 经营经营者提供商品或者服者提供商品或者服务务有欺有欺诈诈行行为为的，的，应应当按照消当按照消费费者的要求增加者的要求增加赔偿赔偿其受到的其受到的

2、损损失，增加失，增加赔偿赔偿的金的金额为额为消消费费者者购买购买商品的价款或接受服商品的价款或接受服务务的的费费用用OverviewIntroductionPrinciples of OperationSome background in semiconductorsDesign InformationDesign ConsiderationsWalk-through ExamplesReal Life ProjectsEarly Use on SatelliteHubbleST-8 LHPTFAWS August 15-19,20112 经营经营者提供商品或者服者提供商品或者服务务有欺有欺诈

3、诈行行为为的，的，应应当按照消当按照消费费者的要求增加者的要求增加赔偿赔偿其受到的其受到的损损失，增加失，增加赔偿赔偿的金的金额为额为消消费费者者购买购买商品的价款或接受服商品的价款或接受服务务的的费费用用AcknowledgmentsFundamental information on Thermo-Electric Coolers presented herein has been extracted from several sources,all of which are available in the public domain.A list of websites used is

4、 included in the references.TFAWS August 15-19,20113Many thanks go to Dr.Jentung Ku(NASA GSFC)for the information from his papers on this topic,and to David Steinfeld for his garage-built TEC“experiment”.经营经营者提供商品或者服者提供商品或者服务务有欺有欺诈诈行行为为的，的，应应当按照消当按照消费费者的要求增加者的要求增加赔偿赔偿其受到的其受到的损损失，增加失，增加赔偿赔偿的金的金额为额为消消

5、费费者者购买购买商品的价款或接受服商品的价款或接受服务务的的费费用用OverviewThe thermoelectric effect is the direct conversion of temperature differences to electric voltage and vice-versa.A thermoelectric device creates a voltage when a temperature difference is applied to it.Conversely,when a voltage is applied to it,it creates a

6、temperature difference.TFAWS August 15-19,20114 经营经营者提供商品或者服者提供商品或者服务务有欺有欺诈诈行行为为的，的，应应当按照消当按照消费费者的要求增加者的要求增加赔偿赔偿其受到的其受到的损损失，增加失，增加赔偿赔偿的金的金额为额为消消费费者者购买购买商品的价款或接受服商品的价款或接受服务务的的费费用用Why Use Them?Pros:Unlike common heat pumps(compression/expansion-based and Stirling cycle),these devices have no moving pa

7、rts and work in any orientationsimple,reliable,compact,low mass,and noiseless,vibration-less operation.Less maintenance-more than 100,000 hours of life for steady state operationFunction in environments that are too severe,too sensitive,or too small for conventional refrigerationContains no chlorofl

8、uorocarbons or other materials which may require periodic replenishmentTemperature control to within fractions of a degree using appropriate support circuitry.Low thermal mass and fast response time of TECs,when combined with an appropriate control loop,can provide precise temperature control.In rel

9、atively stable thermal sink environments,TECs achieve 0.01C temperature stability.Such extreme stability is difficult to achieve by other means.The direction of heat-pumping is fully reversible.Changing the polarity of the DC power supply causes heat to be pumped in the opposite direction,i.e.-a coo

10、ler can become a heater.Temperature differences:for a hot side around room temperature,temperature differences of about 72C and 125C can be achieved by single-stage and multistage TECs,respectively.In situations where the object being cooled generates little or no heat the combination of TE cooling

11、and thermal insulation can produce large temperature differences.Cons:structural integrity of bismuth telluride and soldered joints when subjected to differential thermal expansion stresses.relatively low COP,particularly with large temperature differences.this can be acceptable when the heat load i

12、s small.best suited to situations with modest heat loads,cold temperatures not below 150K,and hot-to-cold-side differences not exceeding 100C.not recommended for use below 130K because of their prohibitively low efficiencies.TFAWS August 15-19,20115 经营经营者提供商品或者服者提供商品或者服务务有欺有欺诈诈行行为为的，的，应应当按照消当按照消费费者的

13、要求增加者的要求增加赔偿赔偿其受到的其受到的损损失，增加失，增加赔偿赔偿的金的金额为额为消消费费者者购买购买商品的价款或接受服商品的价款或接受服务务的的费费用用Thermoelectric EffectsThree separate theories behind the operation of thermoelectric cooling first appeared in the 1800s.TFAWS August 15-19,20116Seebeck effect:Alessandro Volta and Thomas Johann Seebeck(1821)found that h

14、olding the junctions of two dissimilar conductors at different temperatures creates an electromotive force or voltage.This is the basis for thermocouples.Peltier effect:Jean-Charles Peltier discovered(1834)a heating/cooling effect when passing electric current through the junction of two conductors.

15、Thomson effect:William Thomson(Lord Kelvin)showed(1851)that over a temperature gradient,a single conductor with current flowing in it has reversible heating and cooling.Note that the Peltier effect is the inverse of the Seebeck effect.经营经营者提供商品或者服者提供商品或者服务务有欺有欺诈诈行行为为的，的，应应当按照消当按照消费费者的要求增加者的要求增加赔偿赔偿其

16、受到的其受到的损损失，增加失，增加赔偿赔偿的金的金额为额为消消费费者者购买购买商品的价款或接受服商品的价款或接受服务务的的费费用用So What Took So Long To Use Them-TEC EvolutionAlthough these principles were discovered in the 1800s,most early work was on metal alloys,not thermoelectric compounds.it wasnt until the introduction of semiconductor materials in the lat

17、e 1950s,that thermoelectric cooling became a viable technology for small cooling applications.The characteristics of TECs make them highly suitable for precise temperature control applications and where space limitations and reliability are paramount or refrigerants are not desired.TECs have several

18、 advantages over competing technologies,including:high reliability potentialnoise-free operationvibration-free operationscalabilityorientation-independence and compactness(high energy density).Based on these advantages,TECs now dominate certain applications,and new benefits continue to emerge.TECs i

19、n space have become relatively common;they provide temperature control for low noise amplifiers(LNAs),star trackers,and IR(infrared)sensors.TFAWS August 15-19,20117 经营经营者提供商品或者服者提供商品或者服务务有欺有欺诈诈行行为为的，的，应应当按照消当按照消费费者的要求增加者的要求增加赔偿赔偿其受到的其受到的损损失，增加失，增加赔偿赔偿的金的金额为额为消消费费者者购买购买商品的价款或接受服商品的价款或接受服务务的的费费用用Seebe

20、ck EffectThe voltage difference,V,produced across the terminals of an open circuit made from a pair of dissimilar metals,A and B,whose two junctions are held at different temperatures,is directly proportional to the difference between the hot and cold junction temperatures,THOT TCOLDV=(THOT-TCOLD)wh

21、ere =Seebeck coefficientThe temperature difference,produces an electric potential(voltage)that can drive an electric current in a closed circuit.Using the Seebeck effect,thermoelectric power generators convert heat to electricity.Very inefficientUsed when waste heat is readily available,or in remote

22、 areas where dependability overrides efficiencyTFAWS August 15-19,20118 经营经营者提供商品或者服者提供商品或者服务务有欺有欺诈诈行行为为的，的，应应当按照消当按照消费费者的要求增加者的要求增加赔偿赔偿其受到的其受到的损损失，增加失，增加赔偿赔偿的金的金额为额为消消费费者者购买购买商品的价款或接受服商品的价款或接受服务务的的费费用用Peltier EffectWhen an electric current flows through two dissimilar conductors,depending on the di

23、rection of the current flow,the junction of the two conductors will either absorb or release heat.The heat absorbed or released at the junction is proportional to the electrical current.The proportionality constant is known as the Peltier coefficient.Q=*Iwhere =Peltier coefficientand I=junction curr

24、entThomson(Lord Kelvin)showed the relationship between the Seebeck and Peltier coefficients as:=TT =temperature of the junction(K)=Seebeck Coefficient(V/K)Semiconductors are materials of choice for producing the Peltier effect.They are more easily optimized for pumping heatDesigner can control the t

25、ype of charge carrier employed within the conductorWith semiconductor advancements,thermoelectric modules can now be produced to deliver efficient solid state heat pumping for both heating and cooling.TFAWS August 15-19,20119 经营经营者提供商品或者服者提供商品或者服务务有欺有欺诈诈行行为为的，的，应应当按照消当按照消费费者的要求增加者的要求增加赔偿赔偿其受到的其受到的损损

26、失，增加失，增加赔偿赔偿的金的金额为额为消消费费者者购买购买商品的价款或接受服商品的价款或接受服务务的的费费用用But What Are These Coefficients?Remember that the Seebeck Effect-a voltage is produced when a temperature difference is applied across a junction of dissimilar materials.This applied temperature difference causes charged carriers in the materia

27、l,whether they are electrons or holes,to diffuse from the hot side to the cold side,similar to a gas that expands when heated.The efficiency with which a thermoelectric material generates electrical power depends on several material properties,of which perhaps the most important is the thermo-power,

28、or Seebeck coefficient().inversely related its carrier density-a higher results in decreased carrier concentration and decreased electrical conductivity.Therefore,insulators tend to have very high Seebeck coefficients,while metals have lower values.depends on the materials temperature,and crystal st

29、ructure and has units of V/K,or V/K.Typically metals have small coefficients because most have half-filled bands.Electrons(negative charges)and holes(positive charges)both contribute to the induced thermoelectric voltage thus canceling each others contribution to that voltage and making it small.Sup

30、erconductors have a zero coefficient because it is impossible to have a finite voltage across a superconductor,but can be doped with an excess amount of electrons or holes and thus can have large positive or negative coefficients,depending on the charge of the excess carriers.A larger induced thermo

31、electric voltage for a given temperature gradient will lead to a higher efficiency.There is an active research effort to find materials that could make cheaper and more efficient thermoelectric power generators.TFAWS August 15-19,201110 经营经营者提供商品或者服者提供商品或者服务务有欺有欺诈诈行行为为的，的，应应当按照消当按照消费费者的要求增加者的要求增加赔偿赔

32、偿其受到的其受到的损损失，增加失，增加赔偿赔偿的金的金额为额为消消费费者者购买购买商品的价款或接受服商品的价款或接受服务务的的费费用用Seebeck Coefficient-ExamplesBismuth telluride(Bi2Te3):287 V/K A gray powder that is a compound of bismuth and tellurium.It is a semiconductor which,when alloyed with antimony or selenium is an efficient thermoelectric material for re

33、frigeration or portable power generation.Furthermore,the Seebeck coefficient of bulk Bi2Te3 becomes compensated around room temperature,forcing the materials used in power generation devices to be an alloy of bismuth,antimony,tellurium,and selenium.Uranium dioxide(UO2):750 V/K also known as urania o

34、r uranous oxide,is an oxide of uranium,and is a black,radioactive,crystalline powder that occurs naturally.Used in nuclear fuel rods.A mixture of uranium and plutonium dioxides is used as MOX fuel.Prior to 1960 it was used as yellow and black color in ceramic glazes and glass.Perovskite-SrRuO3(Stron

35、tium/Ruthenate):36 V/KConstantan:35 V/KThallium tin telluride(Tl2SnTe5):270 V/KTFAWS August 15-19,201111 经营经营者提供商品或者服者提供商品或者服务务有欺有欺诈诈行行为为的，的，应应当按照消当按照消费费者的要求增加者的要求增加赔偿赔偿其受到的其受到的损损失，增加失，增加赔偿赔偿的金的金额为额为消消费费者者购买购买商品的价款或接受服商品的价款或接受服务务的的费费用用Making a SemiconductorOne process for forming crystalline wafers

36、is forming a cylindrical ingot of high purity monocrystalline silicon is formed by pulling a seed crystal from a melt.A wafer is a thin slice of semiconductor material from these ingots.Wafers are formed of highly pure(99.9999%purity),nearly defect-free single crystalline material.Dopants(impurity a

37、toms)such as boron or phosphorus can be added to the molten intrinsic silicon,thus changing it into n-type or p-type extrinsic silicon(more on this later).The wafer serves as the substrate for microelectronic devices built in and over the wafer and undergoes many microfabrication process steps such

38、as doping or ion implantation,etching,deposition of various materials,and photolithographic patterning.Finally the individual microcircuits are separated(dicing)and packaged.TFAWS August 15-19,201112 经营经营者提供商品或者服者提供商品或者服务务有欺有欺诈诈行行为为的，的，应应当按照消当按照消费费者的要求增加者的要求增加赔偿赔偿其受到的其受到的损损失，增加失，增加赔偿赔偿的金的金额为额为消消费费者者

39、购买购买商品的价款或接受服商品的价款或接受服务务的的费费用用Doping to Make P-or N-Type SemiconductorsSemiconductor doping was formally first developed by John Robert Woodyard working at Sperry Gyroscope Company during World War II.N-Type:Doping pure silicon with Group V elements(nitrogen(N),phosphorus(P),arsenic(As),antimony(Sb)

40、,bismuth(Bi),extra valence electrons are added that become unbonded from individual atoms and allow the compound to be an electrically conductive(N-Type).P-Type:Doping with Group III elements(boron(B),aluminum(Al),gallium(Ga),indium(In),thallium(Tl),which are missing the fourth valence electron,crea

41、tes broken bonds(holes)in the silicon lattice that are free to move.The result is an electrically conductive p-type semiconductor.TFAWS August 15-19,201113 经营经营者提供商品或者服者提供商品或者服务务有欺有欺诈诈行行为为的，的，应应当按照消当按照消费费者的要求增加者的要求增加赔偿赔偿其受到的其受到的损损失，增加失，增加赔偿赔偿的金的金额为额为消消费费者者购买购买商品的价款或接受服商品的价款或接受服务务的的费费用用Making a Semic

42、onductorSemiconductor device fabrication is the process used to create the integrated circuits that are present in everyday electrical and electronic,including thermoelectric,devices.Multiple-step sequence of photographic and chemical processing steps during which electronic circuits are gradually c

43、reated on a wafer made of pure semiconducting material.Silicon is almost always used,but various compound semiconductors are used for specialized applications.The entire manufacturing process,from start to packaged chips ready for shipment,takes six to eight weeks and is performed in highly speciali

44、zed facilities.When feature widths were far greater than about 10 microns,purity was not the issue that it is today in device manufacturing.As devices became more integrated,cleanrooms became even cleaner.The workers in a semiconductor fabrication facility are required to wear cleanroom suits to pro

45、tect the devices from human contamination.In an effort to increase profits,semiconductor device manufacturing has spread from Texas and California in the 1960s to the rest of the world,such as Europe,Middle East,and Asia.TFAWS August 15-19,201114 经营经营者提供商品或者服者提供商品或者服务务有欺有欺诈诈行行为为的，的，应应当按照消当按照消费费者的要求增

46、加者的要求增加赔偿赔偿其受到的其受到的损损失，增加失，增加赔偿赔偿的金的金额为额为消消费费者者购买购买商品的价款或接受服商品的价款或接受服务务的的费费用用Manufacturing a TECSemiconductor manufacturing process is beyond the scope of this course(and the instructors capability!),but an quick overview is shown below.TFAWS August 15-19,201115 经营经营者提供商品或者服者提供商品或者服务务有欺有欺诈诈行行为为的，的，应

47、应当按照消当按照消费费者的要求增加者的要求增加赔偿赔偿其受到的其受到的损损失，增加失，增加赔偿赔偿的金的金额为额为消消费费者者购买购买商品的价款或接受服商品的价款或接受服务务的的费费用用Cool PictureTFAWS August 15-19,201116 经营经营者提供商品或者服者提供商品或者服务务有欺有欺诈诈行行为为的，的，应应当按照消当按照消费费者的要求增加者的要求增加赔偿赔偿其受到的其受到的损损失，增加失，增加赔偿赔偿的金的金额为额为消消费费者者购买购买商品的价款或接受服商品的价款或接受服务务的的费费用用Heat Flow in TE ModuleThe simplest form

48、 of a thermoelectric module:a single semiconductor“pellet is soldered to electrically conductive material(plated copper)on each end.“N-Type”semiconductor material:electrons are repelled by the negative pole of the power supply and attracted by the positive pole.Electrons carry the heat“P-type”semico

49、nductor material:“holes”are repelled by the positive pole of the power supply and attracted by the negative pole.“Holes”carry the heat.It is the charge carriers inherent in the material structure that dictate the direction of the heat flow.This thermoelectric effect and its application in thermoelec

50、tric devices involves very complex physics at the subatomic level.TFAWS August 15-19,201117For you sub-atomic physicists out there,this is way outside the scope of this course.经营经营者提供商品或者服者提供商品或者服务务有欺有欺诈诈行行为为的，的，应应当按照消当按照消费费者的要求增加者的要求增加赔偿赔偿其受到的其受到的损损失，增加失，增加赔偿赔偿的金的金额为额为消消费费者者购买购买商品的价款或接受服商品的价款或接受服务务