Transport properties of gas diffusion layer of proton exchange membrane fuel cells: Effects of compression
Résumé
The gas diffusion layer (GDL) is an essential component for a proton
exchange membrane (PEM) fuel cell because it provides pathways for
different transport processes, including gas diffusion, liquid
permeation, and thermal/electrical conduction. However, the compact
pressure applied on the fuel cell stack can lead to GDL deformation and
thus a change of the transport properties. Therefore, this study
numerically estimated the effect of compression on different transport
properties of GDL. The anisotropic fibrous structure of GDL is first
reconstructed by a stochastic orientation method. Then, the compression
process is simulated by a finite element method to export a deformed GDL
geometry for transport models. The variations of stress, porosity, and
the transport properties with compression are validated. It is found
that the compression reduces the oxygen diffusivity and intrinsic
permeability, while improves the thermal and electrical conductivity of
GDL. The transport property changes are proved larger in the in-plane
direction than through-plane direction. By fitting the correlations of
compression ratio with the transport properties, several correction
factors are proposed. Furthermore, the sensitivity of different
transport properties to compression level is analyzed. These results
provide a deeper understanding and practical approach for the
modification of GDL and PEM fuel cells.