Fluid dynamics performance of different bipolar plates Part II. Flow through the diffusion layer

After studying the velocity and pressure fields inside bipolar plates with different geometries, the analysis has been extended to include the gas passage across the backing or gas diffusion layer (GDL). The gas flow emerging from the porous layer has been monitored using acetone vapor laser-induced fluorescence. The different configurations tested are a parallel commercial case, a set of parallel diagonal channels, a branching cascade-type, and a serpentine distribution of parallel channel blocks. The experimental results have been compared with the predictions obtained from a computational numerical simulation. This study has served to determine the most suitable topology among the tested ones, and has also revealed that knowing the velocity map inside the bipolar plate may not be sufficient to decide if the gas distribution over the catalyst is going to be homogeneous and if a fuel cell is going to operate in an efficient way.