On the relative influence of convection in serpentine flow fields of PEM fuel cells

In polymer electrolyte membrane fuel cells, power losses associated with slow reaction kinetics and mass-transport limits can be strongly nfluenced by convective flow characteristics. Specifically, convection in the form of channel bypass may be utilized to simultaneously increase eactant concentration and reduce product concentration in the catalyst layer, thus reducing the activation and mass-transport overpotentials. An nalytical model is developed here to predict the flow pattern and pressure field in general single-serpentine flow field geometries. The model redicts that a significant portion of the total flow through the fuel cell can occur as in-plane convective flow through the gas diffusion layer under ealistic operating conditions. Further, by comparing the in-plane rates of diffusive and convective transport it is found that the dominant mechanism epends on the geometric and material parameters of the flow field. In particular, it is found that the relative influence of convection depends highly n in-plane permeability of the gas diffusion layer and channel length, and is relatively independent of gas diffusion layer thickness. By designing uel cells to utilize enhanced in-plane convection, it is suggested that losses associated with low oxygen content as well as liquid water buildup in he catalyst layer can be reduced. 2006 Elsevier B.V. All rights reserved.