Geometric Scale Effect of Flow Channels on Performance of Fuel Cells

Abstract

This paper studies the effect of flow channel scaling on fuel cell performance. In particular, the impact of dimensional scale on the order of 100 micrometers and below has been investigated. A model based on three-dimensional computational flow dynamics has been developed which predicts that very small channels result in significantly higher peak power densities compared to their larger counterparts. For experimental verification, microchannel flow structures fabricated with varying sizes in SU-8 photoepoxy have been tested with polymer electrolyte membrane electrode assemblies. The experimental results confirm the predicted outcome at relatively large scales. At especially small scales ͑Ͻ100 m͒, the model ͑which does not consider two-phase flow͒ disagrees with the measured data. Liquid water flooding at the small channel scale is hypothesized as a primary cause for this discrepancy.

Effect of anode and cathode flow field depths on the performance of liquid feed direct methanol fuel cells (DMFCs)

“…3 that the maximum performance is obtained with DMFC comprising anode and cathode flow field plates having a channel depth of 0.4 mm, which is primarily attributed to the fact that for the same flow rates of methanol solution and air, the corresponding Reynolds numbers, 185.3 and 920, respectively are much higher compared to 162.1 and 805.6, 144.1 and 716, and 129 and 644.5 for those with corresponding channel depths of 0.6, 0.8, and 1.0 mm, respectively. Higher liquid/air velocity enhances the mass transfer from the flow channel to the GDL, thereby improving the cell performance [18,19]. A further reduction in channel depth from 0.4 to 0.2 mm, however, causes the performance to decrease.…”

A lung-inspired approach to scalable and robust fuel cell design

“…The first approach is based on empirical alteration of the channel configurations (such as channel path length, 10 land width, 11,12 and land/channel ratio 13,14 ), whereas the second approach imitates the apparent structure of biological organisms. [15][16][17][18][19] The consensus to the first strategy is that the utilization of flow-fields with wider rib spacing, narrower and shorter channels and path length improves reactant distribution.…”

“…[15][16][17][18][19] The consensus to the first strategy is that the utilization of flow-fields with wider rib spacing, narrower and shorter channels and path length improves reactant distribution. 10,11,14 However, these modifications tend to result in lower membrane hydration and membrane conductivity, 13 a higher pressure drop 20 as well as ineffective water and heat management. 10 These drawbacks to the first strategy have led to the exploration of an alternative route, taking ''inspiration'' from biological systems.…”

An effective mesh strategy for CFD modelling of polymer electrolyte membrane fuel cells

“…As a reference mesh, a 0.05 × 0.05 × 0.05 mm 3 cubical element in the flow channels of Mesh 1 is purposely used. Such fine mesh has not been used anywhere else in the literature except in a micro-channel of a micro PEM fuel cell [23]- [26]. Keeping the mesh in the other two directions the same, the mesh in the porous layers are coarsened.…”