Entropy generation analysis based on a three-dimensional agglomerate model of an anion exchange membrane fuel cell

Abstract

A three-dimensional agglomerate numerical model has been used to analyse entropy generation in an anion exchange membrane fuel cell. The effects of inlet relative humidity, platinum loading, carbon loading and ionomer volume fraction on entropy generation have been analysed in the present study. The reversible and irreversible heat have been identified as the main sources of entropy production for all the parameters tested. Even though the production of entropy due to Ohmic loss occurs due to both electronic and ionic potentials, the production of entropy as a result of the first is insignificant in comparison to the latter due to the fact that the electronic conductivity is significantly higher in comparison to the ionic diffusivity coefficient. A strong effect of the back diffusion of water has been found on the entropy production due to Ohmic loss, as the hydration of the membrane directly affects the anion transport through the membrane. Water condensation at the anode catalyst layer and gas diffusion layer has been observed in a few cases, giving rise to the entropy generation due to latent heat. Nevertheless, this has been observed to be 1 to 2 orders of magnitude lower in comparison to the entropy generated due to reversible, irreversible and Ohmic heats.