Numerical investigation on the improved reactant mass transport with depth-dependent flow fields in polymer electrolyte fuel cell under inhomogeneous gas diffusion layer compression

Author(s):  
Pranav Padavu ◽  
Poornesh K. Koorata ◽  
Santoshkumar D. Bhat
Author(s):  
M. Vynnycky ◽  
A. Gordon

An anomaly in the modelling of two-phase flow in the porous cathode gas diffusion layer (GDL) of a polymer electrolyte fuel cell is investigated asymptotically and numerically. Although not commented on previously in literature, the generalized Darcy model used most commonly leads to the surprising prediction that a hydrophilic GDL can lead to better cell performance, in terms of current density, than a hydrophobic one. By analysing a reduced one-dimensional steady-state model and identifying the capillary number as a small dimensionless parameter, we find a potential flaw in the original model, associated with the constitutive relation linking the capillary pressure and the pressures of the wetting and non-wetting phases. Correcting this, we find that, whereas a hydrophilic GDL can sustain a two-phase (gas/liquid) region near the water-producing catalytic layer and gas phase only region further away, a hydrophobic GDL cannot; furthermore, hydrophobic GDLs are found to lead to better cell performance than hydrophilic GDLs, as is indeed experimentally the case.


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