The effect of internal manifold configuration on thermal and electrochemical distributions in commercial scale solid oxide fuel cell stacks fueled by hydrogen and hydrocarbon

Abstract

High operating temperatures and complex internal reactions of solid oxide fuel cell (SOFC) often lead to thermal non-uniformity and uneven electrochemical reaction distributions, which degrades performance and long-term durability. To reduce the non-uniformities and overcome degradation issues, this study investigates the effects of manifold configurations on the thermal, flow, and electrochemical reaction distributions within a commercial scale, cross-flow type SOFC stack under hydrogen and hydrocarbon operations. Using a high-fidelity three-dimensional numerical model, this research compares U-type (all manifolds at one end of the stack) and Z-type (incoming and outgoing manifolds at either end of the stack) manifold stacks. The Z-type configuration demonstrates significant improvements in vertical uniformity by increasing fuel and air flow to the upper repeating units, mitigating thermal gradients and enhancing chemical stability. Under hydrogen operation, the Z-type stack reduces the upper-layer hot zone temperature and alleviates hydrogen and oxygen depletion. Similar trends are observed under hydrocarbon operation, where endothermic reforming reactions lead to unique thermal characteristics, yet the Z-type manifold effectively improves flow uniformity (i.e., uniform mass flow rate of fuel and air to each repeating unit). While the U-type stack exhibits slightly higher power output, the Z-type manifold achieves more balanced distributions, highlighting its role in enhancing long-term operational stability by preventing localized degradation.