Quasi-three-dimensional numerical simulation of a solid oxide fuel cell short stack: Effects of flow configurations including air-flow alternation

The effects of flow configuration in solid oxide fuel cell (SOFC) stacks are investigated using a quasi-three-dimensional numerical model. Flow configurations with alternated air flows in parallel and perpendicular to the fuel flows are considered in addition to the conventional co-, counter-, and cross-flow configurations. The stacks have eight cells with unity aspect ratio and an active area of 4900 mm(2) and are compared at fuel utilization of 0.193, 0.386, 0.579, and 0.772. The numerical model is capable of analyzing both the streamwise and spanwise directions of the cells. Although the counter-flow stack achieves the highest voltage efficiency among the stacks with the conventional flow configurations, it has the highest dispersion of the current density distribution on the cells. Air-flow alternation is effective to achieve uniform and high cell temperature and hence low dispersion of the current density. Alternate air flows parallel to the fuel flows achieve the highest voltage efficiency of 0.797 at a fuel utilization of 0.772, while alternate air flows perpendicular to the fuel flows reduce the risk of local fuel depletion as compared with the cross-flow stacks. Appropriate selection of the air-flow configuration within stacks allows operation at higher efficiency without fuel depletion.