Effects of Fuel Cell Material Properties on Water Management Using CFD Simulation and Neutron Imaging

Effects of fuel cell material properties on water management were numerically investigated using Volume of Fluid (VOF) method in the FLUENT. The results show that the channel surface wettability is an important design variable for both serpentine and interdigitated flow channel configurations. In a serpentine air flow channel, hydrophilic surfaces could benefit the reactant transport to reaction sites by facilitating water transport along channel edges or on channel surfaces; however, the hydrophilic surfaces would also introduce significantly pressure drop as a penalty. For interdigitated air flow channel design, it is observable that liquid water exists only in the outlet channel; it is also observable that water distribution inside GDL is uneven due to the pressure distribution caused by interdigitated structure. An in-situ water measurement method, neutron imaging technique, was used to investigate the water behavior in a PEM fuel cell. The neutron imaging results of an operational PEM fuel shows that water content peak in the membrane was found close to catalyst layer for the low stoic case. The peak value increases with increasing current density and reaches its maximum at certain moderate current density then decreases due to heating effect at higher current density. Minimum water content can be observed inside GDLs, which is caused by the barriers from the hydrophobic nature of GDL pores. Finally, the PEMFC module in the FLUENT was used to build a PEM fuel cell model and preliminary model validation was performed using the previously obtained neutron results. It indicates that the current PEMFC module needs to be further improved to achieve better model predictabilities.