热电冷却-基本知识(半导体制冷片

1、Thermoelectric Cooling - The Basics1 IntroductionAlthough thermoelectric (TE) phenomena were discovered more than 150 years ago, thermoelectric devices (TE coolers) have only been applied commercially during recent decades. For some time, commercial TECs have been developing in parallel with two mai

2、nstream directions of technical progress electronics and photonics, particularly optoelectronics and laser techniques. Lately, a dramatic increase in the application of TE solutions in optoelectronic devices has been observed, such as diode lasers, superluminescent diodes (SLD), various photodetecto

3、rs, diode pumped solid state lasers (DPSS), charge-coupled devices (CCDs), focal plane arrays (FPA) and others.The progress in applications is provided by advantages of TE coolers they are solid state, have no moving parts and are miniature, highly reliable and flexible in design to meet particular

4、requirements.2 What is Thermoelectric Cooling?Thermoelectric cooling uses the Peltier effect to create a heat flux between the junctions of two different types of materials. A Peltier cooler, heater, or thermoelectric heat pump is a solid-state active heat pump which transfers heat from one side of

5、the device to the other side against the temperature gradient (from cold to hot), with consumption of electrical energy. Such an instrument is also called a Peltier device, Peltier heat pump, solid state refrigerator, or thermoelectric cooler (TEC). The Peltier device is a heat pump: when direct cur

6、rent runs through it, heat is moved from one side to the other. Therefore it can be used either for heating or for cooling (refrigeration), although in practice the main application is cooling. It can also be used as a temperature controller that either heats or cools.This technology is far less com

7、monly applied to refrigeration than vapor-compression refrigeration is. The main advantages of a Peltier cooler (compared to a vapor-compression refrigerator) are its lack of moving parts or circulating liquid, and its small size and flexible shape (form factor). Its main disadvantage is that it can

8、not simultaneously have low cost and high power efficiency. Many researchers and companies are trying to develop Peltier coolers that are both cheap and efficient. A Peltier cooler is the opposite of a thermoelectric generator. In a Peltier cooler, electric power is used to generate a temperature di

9、fference between the two sides of the device, while in a thermoelectric generator, a temperature difference between the two sides is used to generate electric power. The operation of both is closely related (both are manifestations of the thermoelectric effect), and therefore the devices are general

10、ly constructed from similar materials using similar designs.3 What is Thermoelectric Cooler?Thermoelectric cooler (TEC), or Peltier Cooler is a solid-state heat pump that uses the Peltier effect to move heat. The modern commercial TEC consists of a number of p- and n- type semiconductor couples conn

11、ected electrically in series and thermally in parallel. These couples are sandwiched between two thermally conductive and electrically insulated substrates. The heat pumping direction can be altered by altering the polarity of the charging DC current. TEC schematic is illustrated in Figure 1. The ty

12、pical materials used for constructing TEC are:1. Substrate: aluminum oxide (Al2O3), aluminum nitride (AlN), or barium oxide (BaO)2. Conductor: Copper3. Thermoelectric semiconductori. n-type: bismuth-telluride-selenium (BiTeSe) compoundii. p-type: bismuth-telluride-antimony (BiTeSb) compound4. Assemb

13、led and joined by solder.Figure 1. Thermoelectric Cooler SchematicThe TEC can be made in different shapes and sizes, but most common shape is a square or a rectangular substrate device. The practical size of a single stage TEC ranges from 3 mm x 3 mm up to 60 mm x 60 mm. The size limitation of 60 mm

14、 x 60 mm is due to the thermal stress. This stress comes from thermal expansion deformations between the cold and the hot junctions of the TEC. To obtain a larger temperature difference, a multistage TEC can be build. The multistage TEC is usually in cascade shape and 6 stages are the maximum practi

15、cal limit. Figure 2 depicts various sizes of TEC.Figure 2. Various Sizes of TEC4 When to consider TEC?TEC can be used in different application where cooling or temperature control of an object is required. In general, TEC is most often used when an object:1. Needs to be cooled below the ambient temp

16、erature, or 2. Requires to be maintained at a consist temperature under a fluctuating ambient temperature.TEC is perfect for cooling a small, low heat load object. Due to the low COP (Coefficient of Performance) compared with compressor cooling, TEC looses its advantage if the cooling load is higher

17、 than 200 watts. But, because TECs have no moving parts, they are lightweight and reliable; they create no electrical noise, and can be operated at any orientation or environment, in some instances TECs are used to cool kilowatts of heat.TEC is exceptionally suitable for a precision temperature cont

18、rol of an object such as a laser diode, CCD or other small objects. Paired with a DC power supply and an electronics proportional/integral (PI) controller packaged in a single chip device, TEC is able to control an object to +/- 0.1oC accuracy. Today, no other cooling method yet can provide such pre

19、cise, simple and convenient temperature control.5 Application of TECTEC is mainly used for cooling of electronic components, especially of optical devices, so as to improve the performance of electronic components, such as computer chips, infrared detectors, lasers and so on. These devices typically

20、 require less cooling power. U.S. Marlow Company has set up a laser cooling segment, and about one third of the personnel are engaged in this study area. TECs applications on the biology and medical. PCR instrument is known as temperature control device or gene amplification process instrument, whic

21、h can be used for the diagnosis of genetic diseases, infectious disease detection, and forensics test that its essence is a temperature circulator. The worlds most advanced PCR instrument is manufactured by using semiconductor refrigeration technology, for example, the British LEP company produced P

22、REM , the Swedish PHARMACIA company produced Gene ATAQ and the United States MJ company produced PTC-150 type PCR instrument. The ventilator pump is made use of semiconductor refrigeration technology, which has a simple structure, has no noise, high speed of condense and high condensing efficiency a

23、nd which is the most advanced respiratory pump, such as the production of 900-C ventilator by Siemens; Nd-YAG laser surgery devices were made by the semiconductor refrigeration technology, which has many characteristics such as small size, light weight, easy to use, sustainable to work, sophisticate

24、d temperature alarm device. For example, our country made H-100-IV-type Nd- YAG laser surgery devices by using semiconductor cooling technology, and application of semiconductor cooling technology also made the stage microscope, slice freezer, hot and cold acupuncture device, cold hats, and freezing

25、 therapy devices. TEC can be applied in the appliance industry. This industry is characterized by the application of portable and small volume cabinet for special occasions. For instance, the Chicago Thermopol Company produced M-50B-type military refrigerating devices, and Michigan Hylan Company pro

26、duced 46 liters thermoelectric refrigerator. Now the larger manufacturers are: Koolatron Corporation in Canada, Europe Elecriolux in Belgium, Supercool Corporation in Sweden, Far East Yams company in Hong Kong and Commander Highclass Electrical Corporation in Taiwan.TEC is applied in desiccant technology. Using this technology to produce the condensing mirror dew point meter is 2-standard equipment which measured condensing humidity. The semiconductor refrigeration technol