Visualisation study of water flooding in a model fuel cell

In order to gain more insight into the water transport in the Gas Diffusion Layer/Gas Flow Channel assembly of PEMFC, a dedicated test bench was designed and realised. It represents a model fuel cell only constituted of a GFC and a GDL. No polymer membrane and electrochemical reaction are needed as the set-up generates water flow through the GDL using a hydraulic generator, see figure 1. The quantity of water being pushed through the GDL may be varied in time to simulate charge load variations in PEMFC. The temperature of water being pushed through the GDL can be set independently of the temperature and relative humidity of the incoming air. Transparent plexiglass plates are used to cover the set-up in order to ensure homogeneous temperature all over the GDL/GFC surface and to allow flow visualisations. The innovative idea in this set-up is to be able to fix independently the air flow rate in regard of the water flow rate which is a limit when investigating water transport phenomena in real electrochemical conditions. The experimental set-up composed of the model cell and the accompanying equipments (gas handlings, hydraulic generator, heating system, video and lighting set-up) will be presented. The basic configuration composed of a GDL and a single straight channel is considered here. Some of the different GDL configurations that have been tested will be presented to highlight that gas by-pass phenomena may occur preventing a proper simulation of the water and gas transport in the model cell. The first visualisations obtained in the single straight channel configuration, see figure 1(b) will be presented focusing on some of the effects of air stoichiometry on water transport in the GDL/GFC arrangement for different values of inlet gas relative humidity. Finally, will be presented interesting transport phenomena that have been observed during experimentations and that are currently under investigation.