  Water management in a hydrogen polymer electrolyte membrane (PEM) fuel cell
is critical for performance. The impact of thermal conductivity and water vapor
diffusion coefficients in a gas diffusion layer (GDL) has been studied by a
mathematical model. The fraction of product water that is removed in the vapour
phase through the GDL as a function of GDL properties and operating conditions
has been calculated and discussed. Furthermore, the current model enables
identification of conditions when condensation occurs in each GDL component and
calculation of temperature gradient across the interface between different
layers, providing insight into the overall mechanism of water transport in a
given cell design. Water transport mode and condensation conditions in the GDL
components depend on the combination of water vapor diffusion coefficients and
thermal conductivities of the GDL components. Different types of GDL and water
removal scenarios have been identified and related to experimentally-determined
GDL properties.
