Enhancement of PEM fuel cell performance by flow channel indentation

• Performance enhancement of PEMFC by gas flow channel indentation (IND) is considered.
• Two types of dent arrangements of symmetric, zigzag and 4 dent shapes are considered.
• IND locally enriches O2 level & current density in CL regions over the dents.
• IND improves diffusion in high concentration loss regions.
• IND provides performance enhancements over 25% at some specific cases.

A three-dimensional, steady, single-phase flow of oxygen, nitrogen and water vapor mixture in the cathode of proton exchange membrane (PEM) fuel cell was numerically studied here. It was shown that the performance of the cell was enhanced by partial blockage of the flow channels in a parallel flow field. Since, channel indentation could increase oxygen content within the catalyst layer. It was observed that the influence of channel indentation in high current density regions was noticeable. Various types of blocks with profile shapes: square (SQ), semicircle (SC) and trapezoid (TR) were considered. Enhancements were compared with the no-dent (ND) called as the base case. The voltage to current relation was modeled using the Tafel equation. This provided the distribution of current density at a prescribed cell voltage. The computations were performed at 333 K, 100,000 Pa, water dew point temperature 313 K, and 50% utilization within the range of 0.2–0.8 V. It was predicted that the flow turns to be two-phase in high current density regions (say cell voltages less than 0.4 V). To push the condensate out of the flow field, adequate pressure gradient were required. This prerequisite was already taken into account in this study. A parametric study considering the influences of dent heights and arrangements, exchange current density, fluid viscous resistance and rib sizes were considered providing enhancements over 25% in the net power. The present study gives a very helpful guideline for flow field manufactures.