Modeling of polymer electrolyte membrane fuel cell with metal foam in the flow-field of the bipolar/end plates

A unified, three-dimensional, steady-state numerical mass-transfer single cell model for polymer electrolyte membrane fuel cell (PEMFC) was developed. The modeled fuel cell uses metal foam in the flow-field of the bipolar/end plates instead of the conventionally used rectangular channels. Transport equations formulated under the PEMFC conditions were solved using the commercial computational fluid dynamics software Fluent® 6.0 with Gambit® 2.0 as pre-processor. Simulations were performed for different permeability levels of the metal foam in the flow-field. Results showed a significant effect of permeability of the metal foam on the performance of the fuel cell. For example: at 10−6 m2 permeability of metal foam the value of average current density was 5943 A/m2 while at 10−11 m2 permeability, the average current density was 8325 A/m2. The average current density value for the multi-parallel flow-field channel design (channel width=0.0625 in., channel depth=0.0625 in. and land width=0.0625 in.), which corresponded to an equivalent permeability value of 4.4×10−8 m2 was 7019 A/m2. This value for the porous configuration with same permeability and under similar conditions of temperature, pressure and reactants flow rate was slightly lower at 6794 A/m2. The trend indicated that decreasing the permeability of the flow-field results in better performance from the cell. However, the permeability of the channel design can not be decreased below the value of around 10−8 m2, due to difficulty in machining thinner channels. Consequently, the use of metal foam flow-field is proposed in the bipolar/end plate. The developed model offers fuel cell developers a scope for improvement of the bipolar/end plates in the fuel cell, by switching over to the metal foam flow-field concept.