Numerical determination of the effective thermal conductivity of fibrous materials. Application to proton exchange membrane fuel cell gas diffusion layers

The knowledge of physical properties, such as the thermal conductivity, plays an important role in the management of the heat transfer in fibrous materials like PEFC gas diffusion layers. Measurement of thermal conductivity by experimental means is not easy (due to the anisotropy and the high porosity), therefore the availability of experimental data is rather limited. In this paper, the numerical determination of the effective thermal conductivity of fibrous materials is investigated using a three-dimensional approach. Two different fiber geometries were studied with randomly generated fiber structures with overlapping and non-overlapping fibers. The corresponding anisotropic thermal conductivities are computed through the solution of the energy transport equation. The results were validated through a comparison with existing experimental data and the influence of different parameters such as fiber orientation, fiber diameter and binding material were investigated.