Multiphysics Modeling of Mass and Heat Transfer in a Thermo-Electrochemical Cell

Extensive energy consumption has brought a huge amountof wasteheat emission. Liquid-state thermo-electrochemical cells (TECs) asa device that can convert waste heat to electricity through a thermogalvaniceffect have attracted increasing attention in the past decades. However,the TEC involves complex physical-chemical processes includingelectrochemical reaction, ion transport, heat transfer, and fluidflow. The interactions and nonlinearities among these processes makeit rather difficult to understand the fundamental issues in the TEC.In this paper, a multiphysics model is constructed to provide a deeperunderstanding of the interplays between heat/mass transport and electrochemicalreaction in the TEC. The results reveal strong interplays among heattransfer, electrolyte flow, ion transport, and electrochemical reactions,which synergistically determine the overall performance of the TEC.The effect of TEC orientation, gravitational acceleration, and theporosity of the electrode/membrane on the performance of TEC is comprehensivelystudied. The results show that the horizontal orientation and a largerporosity/gravitational acceleration can remarkably improve ion transportbetween anode and cathode, consequently enhancing the power generationof the TEC. However, a strong natural flow also facilitates the heatflux across the terminals of the TEC, adversely lowering the conversionefficiency. These results suggest a tradeoff between the enhancementof ion transport and the inhibition of heat transfer between anodeand cathode; an optimal design should be considered in practical applications.Overall, this study provides theoretical guidance for the design ofcell architectures and electrode for thermo-electrochemical conversionin TECs.