Study on Transmission Coefficients Anisotropy of Gas Diffusion Layer in a Proton Exchange Membrane Fuel Cell

Due to the internal fiber structure and extrusion in the assembly process of fuel cell, the gas diffusion layer presents various characteristics in different directions, which makes transmission coefficients show anisotropy and affects overall cell performance. In order to predict the performance and understand influence of coefficient anisotropy, a more accurate model should be found. In this work, a three-dimensional, non-isothermal, twophase agglomerate model considering the porosity difference of gas diffusion layer under rib and channel is established. The influence of conductivity, thermal conductivity, permeability and diffusion coefficient on overall cell performance is investigated by numerical simulation. The results show that diffusion coefficient anisotropy should be considered during numerical simulation when cell voltage is less than or equals to 0.5 V. The conductivity anisotropy should be taken into account when cell voltage is greater than 0.5 V. Compared with isotropic model, electron potential in cathode side increases and current density decreases for conductivity anisotropy model, cell temperature in thermal conductivity anisotropy model is higher, dissolved and liquid water content in permeability anisotropy model increase, local current density in diffusion coefficient anisotropy model is lower. The influence of each coefficient on cell characteristic is various at different voltages.