The ohmic loss is one of the causes increasing irreversibility of Polymer Electrolyte Fuel Cell (PEFC) and result from electrical resistance of membrane and interface between gas diffusion media (GDM) and bipolar plate. The contact resistance is extremely large at slight contact condition because of surface roughness effect, so it is very necessary to assemble PEFC with high clamping pressure. While compression reduce contact resistance, it contract GDM and hence hamper species transport. Therefore, there is trade-off between mass transport and ohmic loss, and it is significant to find suitable pressure value and obtain a good understanding of how compression effects on PEFC.
Experimental and numerical studies have been achieved to investigate the effect of clamping pressure on PEFC. Single cell test has been performed and the experimental results indicate how performance characteristics change with increasing compression. Also, the properties of GDM - thickness, porosity, electrical resistance and gas permeability - have been measured at various compression levels. Based on the measurement works, numerical analysis of PEFC has been carried out to study transport phenomena and electrochemical reactions. The computational works account simultaneously for velocity field, diffusion phenomena and electrochemical reactions in the fully three-dimensional geometry. The predicted performance curves were validated against single cell experimental results with good agreement. The computational results show that contraction of GDM due to compression influence strongly on species transport and current density distribution.
