Effects of Flow Channel Arrangement and Electrolyte Thickness on Thermal Stress for Planar Solid Oxide Fuel Cell Stacks

Typical operating temperature for a solid oxide fuel cell (SOFC) ranges from 700°C to 800°C. A large temperature gradient and thermal stress are induced by internal losses and electro-chemical reactions, resulting in significant structural damage and performance degradation of a SOFC stack, which has become a hindrance to its applications. In this study, a three-dimensional multi-physics CFD model is developed and employed to study the temperature and thermal stress distribution of a planar SOFC stack, then effects of the structure design parameters are investigated, including the flow channel arrangement (i.e., co- and cross-flow) and thickness of the electrolyte layer. The stack modeled is composed of three-unit cells, metallic interconnect layers, sealing components, and anode/cathode current collectors. The simulation results show that the temperature difference in the co-flow case is smaller and the thermal stress is lower than those predicted in the cross-flow. The overall performance of the stack improves as the thickness of the electrolyte layer decreases, but the temperature and its gradient inside the stack become higher. In addition, a large temperature gradient is observed inside the thin electrolyte layer, which leads to a significant increase of the thermal stress. The findings and the research methods in this study can be applied to design and optimize the stack structures by considering the temperature and the thermal stress distribution.