Flow Distribution and Pressure Drop in Different Layout Configurations with Z-Type Arrangement

Abstract

Bipolar plates (BPs) are a key component in fuel cells, which supply fuel and oxidant to reactive sites, remove water and heat, collect current and provide support for the cells in the stack. BPs typically account for 60~85% of the weight and 20~60% of the total cost in a fuel cell stack. It is well-known that performance of a fuel cell is stable in relatively narrow window operational conditions of electrochemistry. A small non-uniformity of flow distribution may lead significant deviation of some channels from the narrow window. Non-uniform flow distribution leads non-uniform electrochemical reactions and causes critical issues of flooding, drying and hotspots. Flow field designs in BPs are central to ensure uniform flow distribution and low pressure drop and to tackle systematically these critical issues. In spite of all the industrial R & D efforts, the gas flow fields in BPs remain one of the most important issues. In this paper, the generalised and unified theory developed by Wang (Int. J. of Hydrogen Energy 2010; 35: 5498-550) was extended to different layout configurations with Z-type arrangement in flow field designs of BPs. The present generalised theory has unique capacities to compare directly, systematically and quantitatively different configurations, existing models and methodologies. The theory makes a step forward in flow field designs in BPs, and provides practical guideline and measures to ensure uniform flow distribution in various configurations of BPs. This type of rational yet tractable generalised theory can contribute to the shared goal of cutting the currently high cost of R & D of fuel cells and performance improvement for commercialisation of fuel cells, which is central to a fuel cell engineer’s “toolbox”. Key words: Bipolar plate; Fuel cell stack; Flow distribution; Manifold; Parallel channels; Pressure drop