Visualization and quantification of cathode channel flooding in PEM fuel cells

An understanding of two-phase flow mechanisms in micro-channels is critical to water management in fuel cell applications. In this work, an in situ visualization study of cathode flooding in an operating fuel cell is presented. Gas relative humidities of 26%, 42% and 66%, current densities of 0.2, 0.5 and 0.8 A cm−2and flow stoichiometries ranging from 2 to 4 are used in this study which represent typical operating conditions for automotive applications. Results are presented in the form of a flow map depicting various two-phase flow patterns. The impact of flooding is also presented in terms of measurable parameters like two-phase pressure drop coefficient and voltage loss. A new parameter called wetted area ratio is introduced to characterize channel flooding and liquid water coverage on a gas diffusion layer, and its repeatability with multiple tests is demonstrated.