A Numerical Study of Pressure Distribution and Flow Cross- over through Gas Diffusion Layer in PEMFC Flow Plate Using Serpentine Channel with Trapezoidal Cross-section

摘要

It is common in a PEM fuel cell for the air to flow through serpentine channels with a square cross- section in the cathode side flow plate. There is a porous diffusion layer adjacent to the flow plate. Flow cross-over of air through the porous diffusion layer from one part of the channel to another can occur as a result of the pressure differences between different parts of the channel causing the flow rate through the channel to vary with the distance along the channel. The channel cross-sectional shape can influence both the pressure drop and the flow cross- over. A numerical study of the pressure distribution and flow cross-over through the gas diffusion layer in PEM fuel cell flow plates using a serpentine channel system has therefore been undertaken for the case where the channel has a trapezoidal cross- sectional shape, the trapezoidal channel cross- sectional shape having the potential to reduce the pressure drop and to augment the flow cross-over. The flow has been assumed to be three-dimensional, steady, incompressible, isothermal and single-phase. The flow through the porous diffusion layer has been described using the Darcy model. The governing equations have been written in dimensionless form and solved using the commercial CFD solver, FIDAP. The solution depends on the following parameters: (ⅰ) the Reynolds number, Re, based on the mean channel width and the mean velocity; (ⅱ) the dimensionless permeability of the gas diffusion layer (ⅲ) the geometry of the channel cross-section; (ⅳ) the flow channel configuration; (ⅴ) the dimensionless thickness of the gas diffusion layer. Results have been obtained for a range of Reynolds numbers and channel geometries for two dimensionless permeabilities and two flow channel configurations for a single value of the dimensionless diffusion layer thickness.