Design principles and analysis of manifold design in a large-scale PEMFC stack

The implementation of large-scale PEMFC stacks faces challenges related to flow uniformity and a lack of detailed design principles. Flow uniformity is influenced by resistance distribution and pressure recovery. In this work, we propose a multi-level flow principle and use an analytical model to couple and evaluate manifold flow and velocity variation. By discussing the effect of channel number, gas architecture, and manifold geometry on the mass transfer characteristics, we have established design principles for the manifold, which can be used to guide the design of the PEMFC. As the number of channels increases, the non-uniformity of reactant distribution significantly increases. By analyzing U-shape and Z-shape in terms of reactant flow uniformity, findings indicate that the Z-shape configuration provides higher pressure and more even reactant distribution. The ratio of the height of headers to cell length and the height ratio of inlet to outlet headers are discussed to determine the most optimal ratios. The pressure recovery phenomenon is observed in the inlet header and becomes more pronounced with an increase in the inlet height. Results show that a specific height of headers to cell length ratio of 0.15 improves output performance and uniformity. Unequal inlet and outlet heights also demonstrate effectiveness, with the minimal height ratio of inlet to outlet headers of 1.5 achieving the best uniformity among the cases studied.