A NUMERICAL STUDY OF THE EFFECT OF FLOW PLATE GEOMETRY ON THE PRESSURE DISTRIBUTION AND CHANNEL-TO-CHANNEL FLOW CROSS-OVER IN A PEM FUEL CELL USING A SERPENTINE FLOW CHANNEL SYSTEM

摘要

It is common in a PEM fuel cell to have the air flow through serpentine channels with a rectangular cross-sectional shape in a flow plate. There is a porous diffusion layer adjacent to this 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, and it causes the flow rate through the channel to vary with distance along the channel and also has an influence on the pressure distribution along the channel. These changes in the pressure distribution as a result of cross-over can effect the fuel cell performance. In the present study the conditions under which cross-over occurs and the effects of the cross-over on the pressure distribution and local channel flow rates have been examined by numerically solving for the flow through the plate-porous layer assembly. Two flow channel arrangements have been considered: (ⅰ) a single serpentine channel flow system with different land widths between the channel sections (ⅱ) a two-channel parallel serpentine flow system. A single phase flow has been considered. The governing equations have been written in dimensionless form using the channel width as the length scale and the mean velocity in the channel as the velocity scale. The resultant set of dimensionless equations has been numerically solved using a commercial finite element code, FIDAP. The solution was obtained by simultaneously numerically solving the dimensionless governing equations for the flow in the channels and for the flow through the porous gas diffusion layer. The numerical calculations were obtained using a commercial finite element code, FIDAP.