Development and experimental validation of a dynamic thermal and water distribution model of an open cathode proton exchange membrane fuel cell

Water concentration in proton exchange membrane (PEM) fuel cells strongly influences performance and durability which demands for fundamental understanding of water transport mechanisms. The system effi ciency can be significantly improved with greater understanding of water flux dynamics through the mem brane and its dependence on the internal conditions of the fuel cell. Therefore, a two-dimensional, non-isothermal, dynamic model of a 100 W open cathode, self-humidified PEM fuel cell syst em has been developed, that is capable of representing system specific control mechanisms for water and thermal management . The model consists of three coupled sub models based on energy, momentum and water mass balance of the system. The work is based on experimental observations of the investigated fuel cell stack, for which the crucial coeffi cients for water transport, namely the diffusion and the electroosmotic drag (EOD) coeffi cient have been determined. The diffusivity of water vapor through the MEA at 30 ◦ C was determined to be 3.3× 10 −8 m 2 s −1 and increases by 3× 10 −10 m 2 s −1 per ◦ C up to 50 ◦ C stack temperature. The EOD coeffi cient was measured as 0.47 to 0.48 water molecules per proton at stack currents from 1 to 3 A. Validation of the steady state and the dynamic model by using experimental data, directly obtained from laboratory tests, has shown that the model predictions match the experimental data well.