Performance analysis of a PEM fuel cell with indented flow channels under various operating conditions

Summary There are situations where using indented flow channels can enhance the Performance of Polymer Electrolyte Membrane Fuel Cells (PEMFCs). The present article aims to introduce and assess a new parameter that has a crucial role in determining these situations. As a novelty, the influence of the binary mass diffusivity of the species on the performance gain caused by indented channels is investigated. A numerical analysis is carried out using an in‐house finite volume code to simulate the cathode of a PEMFC with conventional and indented flow channels. An innovative implementation of the Mirroring Immersed Boundary (MIB) technique is employed to impose semi‐circular cross‐section dents on a fixed background Cartesian grid. The results demonstrate that the channel indentation boosts the cell performance just when the mass diffusion resistance towards the catalyst layer (CL) is high. That is, under high operating pressures, while the current density is also high. As an illustration of this point, under the operating pressure of 5 bar, channel indentation of the cathode side enhances the cell performance by 3.3%, whereas under the operating pressure of 1 bar, the indented bed not only does not improve the cell performance, but reduces it. The outcomes of the study highlight the role of the binary mass diffusivity coefficient of the species and show that the smaller the mass diffusivity coefficients, the more effective indented channels are in improving cell performance. Therefore, channel indentation on the anode side is not profitable since the mass diffusivity coefficient of hydrogen is typically large. This study indicates that the indentation of the PEM fuel cell flow channels at the cathode side affects the cell performance. However, its effectiveness for the studied configuration depends on the cell operating condition. The findings show that the species mass diffusivity plays an important role in this scenario. Channel indentation is profitable when the diffusion resistance is high. Thus, flow channel indentation on the anode side is not profitable since the diffusion resistance is small.