Discrete geometry optimization for reducing flow non-uniformity, asymmetry, and parasitic minor loss pressure drops in Z-type configurations of fuel cells

Abstract

Parallel channel configurations, such as Z-type, used to distribute reagents in planar fuel cells provide lower overall pressure drop as compared to other channel designs. However, due to their inherent characteristics, flow maldistribution in parallel configurations is commonly observed and leads to starvation of reagents in middle channels. In addition, the Reynolds number dependent minor losses at branching tee junctions may cause asymmetric flow non-uniformity and reagent imbalance between the cathode and anode. Herein, we present a universal and simple optimization method to simultaneously reduce flow maldistribution, asymmetry, and parasitic pressure in Z-type parallel configurations of fuel cells or fuel cell stacks that has improved scalability relative to previous methods. A discrete model's governing equations were reduced to yield geometric ratios between headers. Increasing header widths to satisfy these ratios reduced flow maldistribution without modifying parallel channel geometry as validated by computation fluid dynamics (CFD) simulations. Furthermore, decreased Reynolds numbers throughout the headers reduced minor pressure drops and flow distribution asymmetry. We offer several methods to reduce the optimized geometry's footprint, including an adaptation of the discontinuous design.