3D experimental visualization of water flooding in proton exchange membrane fuel cells

Abstract

In Proton Exchange Membrane Fuel Cell (PEMFC) heat and water are generated as a side production. The accumulated water leads to a decrease in PEMFCs' efficiency. Hence, water has to be removed in order to prevent flooding inside the cell. In this study, by using experimental transparent Gas Diffusion Layer (GDL) water transport in PEMFC is visualized, and the capillary fingering mechanisms are studied. The effect of adding Micro Porous Layer (MPL) on water flooding inside the GDL is also examined. The images of high-speed camera confirmed the characteristics of capillary fingering in the GDL. It is observed that lateral flow on the surface of Catalyst Layer (CL) leads to an increase in water flooding in GDL while PEMFC efficiency is decreased. By using the MPL and increasing its thickness, the amount of lateral flow on the CL is decreased, and the generated fingers are entered into the GDL at specific discrete locations on the surface of the MPL. In this condition, the fingers choose straight paths to reach the gas channel (GC). Adding the MPL, with a maximum thickness of 2 cm, leads to a 51.5% reduction in the expansion length of the penetrating fluid inside the GDL in comparison with the GDL without MPL. Also, at the end of the test, the residual volume of the non-wetting fluid inside the GDL and MPL layers is measured. By employing the MPL and increasing its thickness, the volume of the non-wetting fluid inside the cell is reduced down to 38% which causes a decrease in saturation level of water in the GDL, and the cell performance is also improved.