Numerical Evaluation of Effective Gas Diffusivity - Saturation Dependence of Uncompressed and Compressed Gas Diffusion Media in PEFCs

V.P. Schulza, P.P. Mukherjeeb, J. Beckera, A. Wiegmanna, and C.-Y. Wangb
aFaunhofer ITWM, Kaiserslautern 67663, Germany
bElectrochemical Engine Center, Pennsylvania State University, University Park, Pennsylvania 16802, USA


In the current work, we present a comprehensive modeling
framework to predict the effective gas diffusivity, as a function of
liquid water saturation, based on realistic 3-D microstructures of
the uncompressed as well as compressed gas diffusion layer (GDL).
The presented approach combines the generation of a virtual
microscopic GDL and different physical modeling. We develop a
reduced model in order to simulate the compression of the GDL
layer since its compression has a strong impact on the material
properties such as the water transport or its gas diffusion. Then, we
determine the two-phase distribution of a non-wetting fluid, i.e.
water, and a wetting fluid, i.e. air, within the GDL for different
saturations. This is done using a full morphology (FM) model.
Finally, solving the Laplace equation for the partly saturated
medium we determine the relative gas diffusion, i.e. the gas
diffusion depending on the saturation. In the present work, our
approach is applied to a typical GDL medium, a SGL10BA carbon
paper.


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