Geometric optimization of cathode flow fields for large-scale planar SOFC stacks

Three-dimensional computational fluid dynamics (CFD) calculations are performed to investigate the cathode flow distribution in large-scale planar solid oxide fuel cell (SOFC) stacks. The calculations are based on models with different geometric configurations. The effects of stack scale on air flow characteristics are first examined, followed by a specific evaluation of channel aspect ratios and manifold dimensions on flow uniformity and total pressure drop under the condition of constant total power. The CFD results demonstrate that flow uniformity deteriorates significantly as the stack scale expands from 22 to 88 layers. Among optimization strategies, the Elongated Channel Model (ECM) improves uniformity but causes excessive pressure drop, while the Widened Channel Model (WCM) offers marginal uniformity gain with slightly increased pressure drop. In contrast, the Combined Widening Model (CWM) is proven to be the optimal choice, achieving both high flow uniformity and low pressure drop. The physical mechanism regarding the resistance ratio between channels and manifolds is discussed to provide guidelines for the design of commercial-scale stacks.