Hydrodynamic analysis of a novel circular, split-serpentine planar flow field

Planar flow fields are used in a number of clean energy applications such as fuel cells, flow batteries and electrolysers wherein the reactants are made to flow over an electrochemically active surface to enable direct generation of electrical power (or hydrogen in case of electrolysers). A number of these electrochemical cells are stacked in series to make a kilowatt-scale power unit. While fuel cells are traditionally operated at slightly above ambient pressures, new energy storage applications require high pressure operation. A circular planar flow field is more suitable in such conditions as it can be fitted with cylindrical feed chambers. An essential requirement of flow fields is enabling uniform (or desired) distribution over the cell area over a range of flow rates while having low pressure drop. Many flow fields have been proposed for rectangular configurations. Based on detailed computational fluid dynamics (CFD) studies, we propose a novel, sector-wise split serpentine flow field design for a circular plate. The design features an annular, tapered inlet header and a radial outlet with six serpentine flow paths, each covering a sector of about 60 degrees, and which together provide irrigation over the entire area. Fine-grained laminar flow CFD simulations show that the large pressure gradient in the outlet section ensures uniform distribution of the fluid over all the six sectors over a range of Reynolds numbers typical of electrolyser applications. The shapes of the inlet and the outlet headers have been optimized to minimize cell pressure drop while maintaining flow uniformity.