The effects of the cathode flooding on the transient responses of a PEM fuel cell

Abstract

This study investigates the effects of the flooding of the gas diffusion layer (GDL), as a result of liquid water accumulation, on the performance of a proton exchange membrane fuel cell (PEMFC). The transient profiles of the current generated by the cell are obtained using the numerical resolution of the transport equation for the oxygen molar concentration in the unsteady state. The dynamics of the system are captured through the reduction of the effective porosity of the GDL by the liquid water which accumulates in the void space of the GDL. The effects of the GDL porosity, GDL thickness and mass transfer at the GDL-gas channel interface on the evolution with time of the averaged current density are reported. The effects of the current collector rib on the evolution of the molar concentration of oxygen are also examined in detail. r

Energy efficiency improvements by investigating the water flooding management on proton exchange membrane fuel cell (PEMFC)

“…The results show that CCL behaves similar to watershed in the fuel cell which helps to balance the opposite water flux across the membrane and cathode region outlet. Najjari et al [78] conducted experiments to observe the effects of water flooding on GDL because of the accumulation of water in the fuel cell and their results confirmed that excess liquid water affects fuel cell performance drastically. Najjari et al [78] concluded that a thinner GDL will result in a lower resistance for oxygen transport and liquid water is more likely to block the pores easily than vice-versa.…”

Parameter analysis of PEM fuel cell hysteresis effects for transient load use

“…PEMFC is a complex multi-physics system which can be described at different scales and can be established for different purposes: to design specific materials or devices [24], to conceive the stack control algorithm [25][26][27] or to assess the performances of the whole system (FC plants, HEV) [28]. The main objective of this section is to emphasize the key parameters of each subsystem in the global output voltage expression and more precisely on the hysteresis phenomena.…”

A study on current overshoot during start-ups and optimal start-up strategy of proton exchange membrane fuel cells

“…Mass transfer also played an important role on current overshoot behavior during start-up due to the formation of liquid water, which can reduce the effective porosity of gas diffusion layer. Najjari et al [19] developed a two-dimensional transient model for the cathode gas diffusion layer to examine the effects of correlative parameters of gas diffusion layer on transient behavior of average current density. With the increase of porosity, thickness and convective mass transfer coefficient of gas diffusion layer, the magnitude of current overshoot increased, and the maximum value of current overshoot decreased with the increase of shoulder width, indicating that both the oxygen transfer resistance and flooding played important roles in transient behavior of average current densities.…”