Effects of flow pattern and hydrogen recirculation on consistency of current density distribution in a self-humidified polymer electrolyte membrane fuel cell analyzed by a segmented model

Distributions of water and oxygen concentration are the two main factors that influence the consistency of current density in a polymer electrolyte membrane fuel cell. While the former type is relevant to the ohmic loss, the latter one associated with the mass transfer loss. In a self-humidified condition, higher demand for water management is requested as membrane drying often appears. To investigate the effects of flow pattern and hydrogen recirculation on the consistency of current density, the cell is tested under five different conditions, and a quasi-three-dimensional transient non-isothermal model is developed to explain different experimental phenomena in this study. Differences of distributions of current density, resistance and reaction gases are examined by comparing co-flow with counter-flow conditions, humidified with self-humidified conditions and dead-ended anode with hydrogen recirculation conditions. The results show that consistency re-duces with the cell current density increasing, and gas humification is significantly beneficial. In co-flow configurations, the standard deviation of local current density in-creases from 0.02 at 0.2 A cm(-2) to 0.14 at 1.2 A cm(-2) under the humidified condition, increasing from 0.38 at 0.2 A cm(-2) to 0.26 at 1.2 A cm(-2) under the self-humidified condition. The water distribution of the cell in counter-flow configuration is more uniform than that in the co-flow configuration under the whole current density conditions. Hydrogen recirculation can improve the water content of segments near the inlet gas channel in the anode, and the consistency is the best when the current density is larger than 0.4 A cm(-2.) (C) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

Water and oxygen distribution are key factors affecting the consistency of current density in polymer electrolyte membrane fuel cells, with flow patterns and hydrogen recirculation also playing significant roles in cell performance.