| Conceptual Reference Database for Building Envelope Research |
Prev Next |
| Essay:Peltier coolerThe other cooling method, which was the one adopted, is thermoelectric cooling of the bottom of the tank. A thermoelectric cooler (TEC), also called a Peltier cooler, is a device that uses the Peltier effect: the release of heat at the far junction between two dissimilar conductors when a voltage is applied to the near ends. The Peltier effect is the reverse of the Seebeck effect, which is the generation of a voltage between the ends of a pair of dissimilar wires joined at one end and exposed to a temperature gradient. This is the effect used in thermocouple thermometry.Practical thermoelectric devices are made with semiconducting alloys of bismuth, antimony and other semimetallic elements. Many alternations of the two materials are arranged in series with all the cold junctions fastened to one thin ceramic plate and the hot junctions arranged on an opposite ceramic plate. A typical assembly is 40 mm square by 4 mm thick. If the hot side is held at room temperature by a heat sink and the cold side is insulated it can reach about minus 40 degrees. At this point the heat transfer backwards through the device, combined with ordinary resistive heating, prevent further cooling. In practice it is feasible to cool a water tank thirty degrees below ambient, which gives atheoretical lower limit for absorption of water from air at 10 % RH. Since dewpointsensors use exactly the same technology this limit matches the measurement techniqueused in the chamber. Padfield, T., 1998 | ||||||||||