Effect of interface layer on the cooling performance of a single thermoelement

Abstract

The resultant thermoelectric (TE) figure of merit Z, the coefficient of performance (COP), the heat pumping capacity per unit area ( Q c/ S) were derived analytically as functions of l 0, ρ c, κ c and s c for a single thermoelement (STE) by taking into account the interface layers, where l 0 is a length of a TE material, ρ c the electrical interface resistivity, κ c the thermal interface conductivity and s c the ratio of the Seebeck coefficient of an interface layer to that of a TE material. As a result, it was first revealed that the increase in Z 0 T of a TE material is not necessarily reflected in the increase in ZT of an STE as long as the interface layers are present. The COP and Q c/ S are lowered remarkably for s c = 0 and κ c ⩽ 10 4 W/m 2 K. However, it was clarified that even for low values of κ c, the COP and Q c/ S return to the original high values (obtained for κ c ⩾ 10 5 W/m 2 K) at s c = 0.45 and 0.90, respectively. The definite criterion of s c whether or not the boundary Seebeck coefficient has an effect on the enhancement of the cooling performance was indicated quantitatively for an STE with interface layers.