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(R) 6.0 with Gambit(R) 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) m(2) permeability of metal foam the value of average current density was 5943 A/m(2) while at 10(-11) m(2) permeability, the average current density was 8325 A/m(2). 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 x 10(-8) m(2) was 7019 A/m(2). 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/m(2). 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) m(2), 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. (C) 2002 Elsevier Science B.V. All rights reserved.