Design of Thermoelectric Modules for High Heat Flux Cooling

Abstract

Thermoelectric (TE) coolers work on the Seebeck effect, where an electrical current is used to drive a heat flux against a temperature gradient. They have applications for active cooling of electronic devices but have low coefficients of performance (COP < 1) at high heat fluxes (>10 W/cm2, dT = 15 K). While the active elements (TE material) in a TE cooling module lead to cooling, the nonactive elements, such as the electrical leads and headers, cause joule heating and decrease the coefficient of performance. A conventional module design uses purely horizontal leads and vertical active elements. In this work, we numerically investigate trapezoidal leads with angled active elements as a method to improve cooler performance in terms of lower parasitic resistance, higher packing fraction and higher reliability, for both supperlattice thinfilm and bulk TE materials. For source and sink side temperatures of 30 آ°C and 45 آ°C, we show that, for a constant packing fraction, defined as the ratio of active element area to the couple base area, trapezoidal leads decrease electrical losses but also increase thermal resistance. We also demonstrate that trapezoidal leads can be used to increase the packing fraction to values greater than one, leading to a two times increase in heat pumping capacity. Structural analysis shows a significant reduction in both tensile and shear stresses in the TE modules with trapezoidal leads. Thus, the present work provides a pathway to engineer more reliable thermoelectric coolers (TECs) and improve their efficiency by >30% at a two times higher heat flux as compared to the stateoftheart.