Evaluation of porosity and thickness on effective diffusivity in gas diffusion layer

Porosity and thickness are two key properties of GDL and both affect the transport properties of porous media. This paper focuses on the influence of the GDL microstructure on its transport properties, which will be analyzed from different samples. The results show that thickness affects permeability through the principal flow direction more than through non-principal directions, thus it is necessary to increase the anisotropic characteristics of the material. Moreover, it is ascertained that permeability is more affected by the number of fibers than by the thickness. For the variable porosity sample groups, the simulation results are coincident with the fractal model in principal and non-principal flow directions, and water saturation inside the GDL samples has been evaluated. They are shown several cases of the GDL model to illustrate the fluid flow along through-plane and in-plane directions as well as the conditions at inlet and outlet boundaries. These results have a strong potential to gain deeper understanding of the microscopic flow phenomenon within the porous structures and to determine the influence the microstructure has on the macroscopic transport properties, thus leading to notable improvements of fuel cell performance. (C) 2016 Elsevier B.V. All rights reserved.