In situ Visualization of Water Droplets in Polymer Electrolyte Fuel Cell Cathode

A transparent optical cell for a polymer electrolyte fuel cell (PEFC) was used to measure the water distribution in the cathode during cell operation. The distribution of water droplets could be clearly observed in the cathode. The results show that the transition point to two-phase flow in the cathode flow field moved towards the cathode inlet when the cathode gas utilization rate was increased. This was compared with the results of a calculation based on a two-dimensional cell model and good agreement between the two was obtained. It was also observed that at high current densities, water droplets were swept away from the flow field by the shear force of the cathode gas.