Thermal conductivity measurement of gas diffusion layer used in PEMFC

The objective of the present work is to develop an apparatus to measure the thermal conductivity of gas diffusion layer (GDL) as a function of temperature and compression, and also to develop an effective thermal conductivity (ETC) model to predict thermal conductivity of fibrous media as a function of compression. Thermal conductivity of GDL at different operating conditions is essential for accurate thermal modeling in a Proton exchange membrane (PEM) fuel cell stack. Steady state method of guarded hot plate method was used to perform the thermal conductivity measurements and the measurements were carried out on commercially available GDL samples - Toray and SGL (SIGRACET®). GDL thicknesses at different compressions were also measured to calculate the thermal conductivity of GDL at a given compression. Thermal conductivity of Toray was found to decrease with temperature while that of SGL was constant over temperature. Both Toray and SGL thermal conductivities were observed to increase with compression. Also, contact resistance between GDL-copper surfaces was found to decrease with compression for both Toray and SGL. Furthermore, the effective thermal conductivity model was used to estimate the thermal conductivity of the tested GDL samples at different compressions and was found to match pretty well with the experimentally determined thermal conductivity values