Fractal Model For Material Property Of Gas Diffusion Layer In PEM Fuel Cell

Gas diffusion layer (GDL) is one of the most important electrode components in proton exchange membrane fuel cell (PEMFC). Its structure and material parameters influence the overall performance of the PEM fuel cell significantly. The material parameters (such as permeability, effective thermal conductivity and effective diffusion coefficient) have close connection with microstructure characteristic, and they are the foundation of simulation. Research indicates that GDL have characteristics of randomness, irregularity and self-similarity. Fractal geometry has been broadly used in the fields of random structure and multi-scale physical problem, especially to the description of complex structure. The author of this paper applies the fractal theory to study the fractal character of GDL based on mercury porosimetry and scanning electron microscope (SEM), uses the fractal dimensions to describe the GDL microstructures and lucubrates the material parameters of GDL. Research achievements and innovations as bellow:Mercury porosimetry is taken to get pore distributions for pure TGP-H-060 carbon paper and the carbon paper treated by 30wt% PTFE. The author applies fractal method to analyze the experimental data. It shows that pore structures of two samples have obvious fractal characteristic, so fractal method can be used in the research of GDL. And it's also a foundation of this work.The curve and pore area fractal dimensions are introduced for GDL of PEMFC. The study on five fractal dimension computation methods (box-counting method, differential box-counting method, peleg-blanket covering method, fractal Brownian increment random field model and variation) is based on the scanning electron microscope images of pure TGP-H-060 carbon paper and the carbon paper treated by 30wt% PTFE. Because of the precise result from the simplest box-counting method, quick calculation and its universality, box-counting method is chosen in the fractal dimension computation of GDL. And then the curve and pore area fractal dimensions are determined by this method.