A novel flow field with controllable pressure gradient to enhance mass transport and water removal of PEM fuel cells

Abstract

An easily machined novel flow field with controllable pressure gradient across adjacent channels was designed and a two dimensional, across-the-channel, twophase model was developed to study the gas transport and water removal of the novel configuration. The effect of channel-rib width ratio, GDL thickness and pressure gradient on the profiles of oxygen concentration and water saturation within the GDL were investigated. Special attention was paid to the mechanisms of the promoted mass transport and water removal rates under a pressure gradient. The model was validated by experiments with various channel-rib ratios and GDL thicknesses at different operating pressure. The results revealed that, oxygen concentration was increased, and the water saturation was reduced under the rib with a pressure gradient generated across the adjacent channels. The optimal pressure gradient is between 0.1 to 0.2 atm for the studied channel geometry and configuration. The mechanisms of the improved cell performance were elucidated. K E Y W O R D S bipolar plates, novel flow fields, PEM fuel cells, pressure gradient, water removal

Reinforcement of proton‐exchange membrane fuel cell performance through a novel flow field design with auxiliary channels and a hole array

“…Flow field plates, also known as bipolar plates in fuel cell stacks, are one of the crucial components of PEM fuel cells, which account for over 60% of the mass and around 30% of the cost 6–8 . Since reactant gas is supplied and the produced water is removed from the flow channels grooved on the flow field plate, a better design of the flow field plate strongly affects the performance and uniformity of the current density of the cell 9–11 …”

“…This novel flow field design can boost the under‐rib mass transport and water removal, thus ultimately improving the overall performance of fuel cells with a small pressure drop 37 . Another example is the novel flow field with a controllable pressure gradient across the adjacent channels, 11 in which an extra set of parallel channels operated with different pressure was deployed. This easily machined novel flow field reinforced the convective transport of reactant gas and water through the rib, achieved an improved cell performance and more uniform current distribution.…”

A segmented fuel cell unit with functionally graded distributions of platinum loading and operating temperature

“…where 0 ij D (m 2 s -1 ) is the intrinsic binary diffusivity of species i and j, ε is the electrode porosity and s is the water saturation, defined as the volume fraction of liquid water within the porous electrode, which is calculated by the following equation based on the volume of fluid (VOF) method [38]. where c D (m 2 s -1 ) is the capillary diffusion coefficient, p k (m 2 ) is the permeability of the porous electrode, w M (kg mol -1 ) is the molecular weight of water, g w µ , l w µ and g µ (Pa s) are the viscosity of vapor, liquid water and gas mixture, respectively, l w S (mol m -3 s -1 ) is the source term of liquid water.…”

Combining Baffles and Secondary Porous Layers for Performance Enhancement of Proton Exchange Membrane Fuel Cells

“…Therefore, it is reasonable to believe that it is possible to enhance the performance of the cell with a relatively simple flow field design by manipulating heat and mass transfer without the necessity of using complex and costly flow fields, e.g., Toyota 3D fine-mesh structure. For example, Xing et al [8] modified the parallel flow field by enabling adjacent channels to operate at different pressures. This novel flow field reinforced the reactant mass transport and reduced the water accumulation under the rib.…”