Measuring Critical Velocity of Water Droplet Removal on Gas Diffusion Layers of Proton Exchange Membrane Fuel Cells

Abstract

The production of water on the cathode electrode of proton exchange membrane (PEM) fuel cells may cause problems with flooding or freezing of cell. Therefore, there is a need for water management. This study investigates water droplet removal on the gas diffusion layer by measuring critical velocity-the velocity needed to remove droplets formed above the GDL. A test apparatus was designed for this study, and the effects of droplet diameter, GDL thickness, and PTFE (polytetrafluoroethylene) loading on the critical velocity were studied. When droplet diameter and PTFE loading were increased, a decrease in critical velocity was observed. However, as GDL thickness increased, depending on the PTFE loading, either an increase or decrease in critical velocity was observed. Thus, it was concluded that increased droplet diameter and increased PTFE loading result in lower critical velocities, increasing thickness results in lower critical velocity for low PTFE loadings, and increasing thickness does not have a significant effect on the critical velocity for high PTFE loadings. This work increases the understanding of designing an optimum GDL in the fuel cell, while also providing insight on the critical velocity needed to remove water droplets from the GDL.