Fractal permeability models for the microporous layer and gas diffusion layer of PEM fuel cell

In this investigation, a series fractal permeability model is developed to predict the gas permeability for the microporous layer (MPL) and gas diffusion layer of proton exchange membrane fuel cells. In addition to macroscopic flow, the model also considers gas molecules using the Adzumi equation. Parameters such as the maximum pore size, porosity, fractal area dimension and fractal tortuosity dimension, and the thickness of the sample are used to predict the permeability. From scanning electron microscopic images, the two fractal dimensions are determined by the box-counting method. This model is validated by comparison with experimental measurement results. Effects of compression pressure and MPL baking time are studied. Results show that the gas permeability decreases with increasing compression pressure. Longer MPL baking time increases gas permeability, and cell performance.