Numerical Studies of Effective Diffusivity in Fibrous Porous Media

Abstract

Current modelling of effective diffusivity in the Gas Diffusion Layer (GDL) of the Polymer Exchange Membrane Fuel Cell (PEMFC), often relies on semi-empirical equations with limited accuracy. In particular, there is a need to develop models incorporating the microscopic structure of the porous GDL when performing flow simulations. The objective of this thesis is to obtain a simulation program to calculate the effective diffusivity of realistic scanned porous media with random walk simulations. This approach has the advantage of not making any assumption about the material, and various aspects of the material can thus be investigated. The simulation program is validated with literature data of the effective diffusivity of continuous random fibres, defined by point and direction. This present study however is performing random walks in uniform grids where voxels are either void or solid. A qualitative simulation program was developed and the validation results showed an relative error of 50% compared to the Bosanquet formula, thus more work needs to be done.