| A numerical study of the flow and pressure distributions in Polymer Electrolyte Membrane Fuel Cell (PEMFC) flow field plates (FFP) and the related flow cross-over through the adjacent porous gas diffusion layer (GDL) using a serpentine channel system has been performed. The objective of the present work was to study the effect of the FFP geometry, and of the GDL properties, especially the permeability, on the pressure distribution in the FFP channels. In the first stage of this study, the flow was assumed to be 3-D, steady, single-phase and incompressible. The solution domain consisted of the solid FFP, channel gas flow and porous GDL. The flow through the porous GDL has been described using Darcy model. The governing equations have been written in dimensionless form and solved by using the commercial Finite Element Method (FEM) software package, FIDAP. The solution depends on the parameters of (1) Reynolds number, (2) Prandtl number, (3) GDL permeability, (4) GDL thickness, (5) land width, (6) the channel cross-section geometry (square and trapezoidal), (7) channel length, (8) bend shape, (9) the flow channel configuration (single channel or two parallel channels with different numbers of passes). The obtained numerical results indicated that channel-to-channel flow cross-over through GDL has a significant influence on the pressure variation through the channel, tending to decrease the pressure drop across the channel. The trapezoidal cross-section shape of the channel can enhance the flow cross-over and decrease the pressure drop through the channel. In the second stage of this study, another numerical model was developed by taking the gas compressibility into account. The commercial Computational Fluid Dynamics (CFD) solver, FLUENT was used to solve the general governing equations, together with the ideal gas equation of state. Only single serpentine channel flow has been considered here. A comparison of the results from the compressible and incompressible models indicated that there are only small differences (within 6.8%) between the compressible and incompressible predictions of pressure drop through the channel for the situations considered in this study, and the total channel length and bend shape have significant effects on the pressure and Mach number distributions along the channel. |
