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

Extensive energy consumption has brought a huge amount of waste heat emission. Liquid-state thermo-electrochemical cells (TECs) as a device that can convert waste heat to electricity through a thermogalvanic effect have attracted increasing attention in the past decades. However, the TEC involves complex physical–chemical processes including electrochemical reaction, ion transport, heat transfer, and fluid flow. The interactions and nonlinearities among these processes make it rather difficult to understand the fundamental issues in the TEC. In this paper, a multiphysics model is constructed to provide a deeper understanding of the interplays between heat/mass transport and electrochemical reaction in the TEC. The results reveal strong interplays among heat transfer, electrolyte flow, ion transport, and electrochemical reactions, which synergistically determine the overall performance of the TEC. The effect of TEC orientation, gravitational acceleration, and the porosity of the electrode/membrane on the performance of TEC is comprehensively studied. The results show that the horizontal orientation and a larger porosity/gravitational acceleration can remarkably improve ion transport between anode and cathode, consequently enhancing the power generation of the TEC. However, a strong natural flow also facilitates the heat flux across the terminals of the TEC, adversely lowering the conversion efficiency. These results suggest a tradeoff between the enhancement of ion transport and the inhibition of heat transfer between anode and cathode; an optimal design should be considered in practical applications. Overall, this study provides theoretical guidance for the design of cell architectures and electrode for thermo-electrochemical conversion in TECs.