Thermoelectricity theory has stated that both, heat absorbed and rejected at the cold and hot sides of a thermoelectric pair by Peltier effect only depends on the thermoelectric properties of the semiconductors, the absolute temperature in the unions, and the electrical current through the pair. However, the irreversible phenomena, Joule and Fourier effect, are volumetric effects. That is to say, they can be affected by the geometry of the pellets, and furthermore, they have an influence on the temperature at the surfaces where the Peltier effect takes place. As consequence, the net heat power pumped by a thermoelectric pair can be modified when non-constant cross section pellets are used. In this paper, variable cross section pellets are studied, analysing the influence on the heat power absorbed, and on the coefficient of performance. Firstly the study of the effect just on the irreversible phenomena, and secondly, taking into account the influence on the irreversible effects together with Peltier effect. This problem has been conveniently studied fixing the volume of the pellets and when the lateral surfaces of pellet are not adiabatic. In this paper the problem has been analysed on a different way. Different geometrical characteristics of the pellets are analysed in order to improve the exchange of heat power at the ends of the pellets evaluating the effect produced in other variables, specially in the volume of the pellets. The lateral surfaces are considered adiabatic taking into account the efforts done by the manufactures of commercial thermoelectric modules to reduce these thermal losses. The results are compared with typical values obtained using constant cross sections. The conclusions obtained in this work can be of interest in the design of thermoelectric pairs in applications where the size of the pellets allows for the use of variable cross sections, or the thermolectric properties are extremely sensitive to temperature variations.
Palabras clave: Thermoelectricity, Optimal Design, Pellets
7th European Workshop on Thermoelectrics, Poster #26, Pamplona, Navarra (España). 03 octubre 2002
Fecha de publicación: octubre 2002.
A. Arenas, J. Vázquez, R. Palacios, Performance analysis of thermoelectric Pellets with non-constant cross sections, 7th European Workshop on Thermoelectrics, Poster #26. Pamplona, España, 03-04 Octubre 2002