2-D and 3-D modeling of proton exchange membrane fuel cells

In this study, 2-D and 3-D steady state, isothermal, and one-phase numerical models of a single Proton Exchange Membrane Fuel Cell were built by using COMSOL Multiphysics® software. A parallel-to-flow model of a single cell was used as the modeling domain. The model consisted of the delivery of electrical current in solid phase, transportation of gases in the flow channels, and transmission of water and ions in the polymer electrolyte membrane. The gas flow of the reactants in the channels was solved by incompressible Navier-Stokes equations with Brinkman equation while water and ion transportation was solved by generalized Maxwell-Stefan equations. The investigation was mainly focused on effects of the geometry and the effects of the parameters that are related with temperature, such as exchange current density, ionic conductivity and diffusivity values. To achieve that, 2-D and 3-D parallel-to-flow models with different exchange current density, ionic conductivity and diffusivity values and different geometries were solved. Mass fraction distribution of hydrogen, oxygen, and water were examined at different temperature and voltage values. It was pointed out from the results that increasing exchange current density, ionic conductivity and diffusivity values results in better performance. To determine the effect of geometry two models with different geometries were built and solved. One of the models has planar channel geometry while the other has cylindrical channel geometry. At middle cell potential values where the power density is high, the current density that is obtain from cylindrical model is between 0.58-0.93 A/cm2 at 25 ?C and 0.82-1.05 A/cm2 at 80 ?C. At same cell potential values, the current density that is obtain from planar model is between 0.54-0.84 A/cm2 at 25 ?C and 0.75-0.95 A/cm2 at 80 ?C.