Entropy analysis of thermoelectric heat pumps including multi-channel heat exchangers: design considerations

Abstract

This work aims to propose routes for thermoelectric heat pump design based on Entropy Generation Minimization (EGM). The system considered is composed of a thermoelectric module sandwiched between two parallel multi-channels heat exchangers. Co-optimization of the heat exchanger and the thermoelectric module designs are lead in order to increase the system performance, depending on realistic manufacturing constraints. The optimized variables considered in this study are: the thermoelectric leg number, their length and section; and the number of channels and their length and diameter in both heat exchangers. The following dissipative contributions are identified: thermal conduction and Joule effect in the thermoelectric module, and heat transfer and viscous dissipation in both heat exchangers. On the one hand, the thermoelectric module design has to respect optimal design ratios derived analytically to meet a given thermal power demand with maximum COP. On the other hand, dissipative contributions competition in the heat exchangers results in two distinct optimal designs, depending on the thermal power density. Taking into account manufacturing constraints, realistic system design is derived and discussed. Although the entropy generation in the heat exchangers is low compared to that in the thermoelectric module (dominated by Joule effect), the heat exchanger design highly impacts the global system performance.

Keywords

• Second law analysis,Entropy Generation Minimization (EGM); Energy conversion; Heat exchanger; viscous dissipation