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Unformatted text preview: Thermoelectric Cooling FAQ 1 2006,Tellurex Corporation 1462 International Drive Traverse City, Michigan 49684 231-947-0110 www.tellurex.com The Most Frequently Asked Questions About Thermoelectric Cooling 1.Howdoesthistechnologywork? The basic concept behind thermoelectric (TE) technology is the Peltier effecta phenomenon Frst discovered in the early 19th century. The Peltier effect occurs whenever electrical current ows through two dissimilar conductors; depending on the direction of current ow, the junction of the two conductors will either absorb or release heat. Explaining the Peltier effect and its operation in thermoelectric devices, is a very challenging proposition because it ultimately keys on some very complex physics at the sub-atomic level. Here we will attempt to approach it from a conceptual perspective with the goal of giving readers an intuitive grasp of this technology (i.e., without getting too bogged down in the minutia). In the world of thermoelectric technology, semiconductors (usually Bismuth Telluride) are the material of choice for producing the Peltier effectin part because they can be more easily optimized for pumping heat, but also because designers can control the type of charge carrier employed within the conductor (the importance of this will be explained later). Using this type of material, a Peltier device (i.e., thermoelectric module) can be constructedin its simplest formaround a single semiconductor pellet which is soldered to electrically-conductive material on each end (usually plated copper). In this stripped-down conFguration (see right), the second dissimilar material required for the Peltier effect, is actually the copper connection paths to the power supply. It is important to note that the heat will be moved (or pumped) in the direction of charge carrier movement throughout the circuit (actually, it is the charge carriers that transfer the heat). In Figure 1 N-type semiconductor material is used to fabricate the pellet so that electrons (with a negative charge) will be the charge carrier employed to create the bulk of the Peltier effect. With a DC voltage source connected as shown, electrons will be repelled by the negative pole and attracted by the positive pole of the supply; this forces electron ow in a clockwise direction (as shown in the drawing). With the electrons owing through the N- type material from bottom to top, heat is absorbed at the bottom junction and actively transferred to the top junctionit is effectively pumped by the charge carriers through the semiconductor pellet. In the thermoelectric industry, P-type semiconductor pellets are also employed. P- type pellets are manufactured so that the charge carriers in the material are positive (known in electronics as holes). These holes enhance the electrical conductivity of the P-type crystaline structure, allowing electrons to ow more freely through the material when...
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