制冷技术(英文版)Ch4-090530.docVIP

Part 2. The Principles of Refrigeration ( 80-90 pages) Chapter 4. Methods of Decreasing Temperature ( II ) Relative to solid refrigerants 4-1）Decreasing temperature by Thermo-Electric Peltier Effect ) Thermo-electric refrigeration （热电制冷） Seebeck effect (塞贝克效应) ： If two different metals (or a metal and a semiconductor) are joined and the two junctions are kept at different temperatures, an electromotive force (e.m.f.) is developed in the circuit. This is, and the circuit constitutes a thermocouple. Peltier effect （珀耳帖效应） In 1834 J. Peltier discovered that when an electric current passes around a circuit composed of two different metals，one junction became cool and the other became warm. Peltier effect is the converse of the Seebeck effect. Larger temperature differences are produced with metal-semiconductor junctions than with metal-metal junctions （故又称半导体制冷）. . A practical thermoelectric cooler usually consists of several modules （模块） of semiconductor material that are connected electrically in series and thermally in parallel. There is no compressor and no fluid flow involved. The thermoelectric cooler has the advantages of being compact, simple, quiet, and reliable. Its refrigerating capacity can be simply controlled by input voltage of DC power. However the efficiency of the thermaoelectric refrigeration is quite low compared with vapor compression refrigeration. Up to now the applications of thermal-electric refrigeration are mainly found in special situations where require small refrigeration load in restricted space, for example, Calorie meter, CPU cooler, cold water machine, dehumidifier, refrigerators of drugs, beer, cosmetics, mini-refrigerator for vehicle, mini-coolers for laser and infrared equipment and sensors, electronic switch board cooling and aviation black box cooling, and many other instruments. Future applications of thermal-electric refrigeration will mainly depend on the new development of thermal-electric materials。 Fig.