Theory of Nernst Generators and Refrigerators

Abstract

Formulas for efficiency and coefficient of performance are derived for devices based on the Nernst and Ettingshausen effects. The equations reduce to those of Harman and Honig in the limits of small figure of merit and refrigerator current, but they do not approach the Carnot limits. To obtain a better device theory, one must solve a two‐dimensional partial differential equation in which the current density is allowed to vary with position. A crude maximization procedure for the figure of merit is shown for a one‐band nondegenerate semi‐conductor in a weak magnetic field. Experimental data indicate that Hg_xCd_1−x Te alloys are perhaps the best materials for such devices at present.