Effective Thermal Conductivity of Gas Diffusion Layers Used in PEMFC: Measured with Guarded-Hot-Plate Method and Predicted by a Fractal Model

An experimental setup to determine thermal conductivity and thickness of a gas diffusion layer (GDL) as a function of compression was developed and calibrated. The actual thermal conductivities, based on compressed thickness, of plain Toray TGP-H gas diffusion layer (GDL) at compression pressures of 0.04 to 1.5 MPa and over temperature range of 25 C to 75 C are reported in this paper. The thermal conductivity of TGP-H GDL was found to decrease with temperature and to increase with compression. An effort was made to numerically account for the effective thermal conductivity by using theoretical models. Krischer model was found to be able to match with the experimental data, but this model relied on a priori knowledge of the thermal properties of the solid matrix. A new analytical model based on fractal analysis of GDL microstructure is proposed to account for GDL thermal conductivity as well as its variation with compression without using any empirical parameter.