Numerical investigation of liquid water dynamics in wave-like gas channels of PEMFCs

Abstract

Summary For the air feed in proton exchange membrane fuel cells (PEMFCs), the wave‐like gas channel (GC) shows obvious advantages over the straight GC because the former enhances collision of secondary flow and diffusion in the gas diffusion layer (GDL). However, it is prone to water flooding, which brings greater pressure drop, larger pressure oscillation, and blocking of reaction area. In the present study, numerical models of the water dynamic processes, including water droplets emerging from micropores on the GDL surface and removing through the GC, are established based on the volume of fluid (VOF) method. Water coverage ratio and pressure drop are calculated to evaluate the water flooding. The effects of the dimensional parameters of wave‐like GC and contact angle of channel walls on the water accumulation are studied. The emergence and removal of liquid water is a quasiperiodic and oscillating process. Multicycle simulations show that channel pressure drop increases linearly with greater growth rate than channel length. The equilibrium position of water droplet is strongly dependent on the relative wettability of the GDL and bipolar plate (BPP) surfaces. And the geometric parameters of GC have a significant impact on the pressure, water removal behavior and detachment time. Smaller bent angle brings bigger pressure drop, and larger cycle length is helpful for relieving the oscillation of pressure.

Numerical Investigation of Liquid Water Transport Dynamics in Novel Hybrid Sinusoidal Flow Channel Designs for PEMFC

“…Design 1 has a smaller amplitude of 0.1 mm while Design 2 has an amplitude of 0.2 mm, and as such, this is responsible for the variance in pressure drop and velocity magnitude. This result agrees with the findings of Xu et al [22] on the significant influence that geometric configurations have on flows in wave-like channels. They opined that the geometric parameters of wave-like channels have a considerable impact on the pressure drop, water removal behaviour and detachment time.…”

“…This is as a result of the dual-pitched arrangement with the shorter pitch responsible for improved fluid velocity magnitude while the long pitch relieves the excess pressure oscillation. However, Designs 1 and 2 proved to be much superior in terms of quick water expulsion, and this goes on to show the significant influence of channel architecture on flow behaviour [22].…”

“…Their investigative study showed the significance of channel geometry on water expulsion in channels. Recently, Xu et al [22] investigated the dynamics of droplet emergence and removal in a wavelike flow channel through computational fluid dynamics (CFD) simulation in association with the VOF method. The effects of contact angle and geometric parameters were also considered in their work.…”

Numerical and Experimental Investigation of the Asymmetric Humidification and Dynamic Temperature in Proton Exchange Membrane Fuel Cell

“…The thermal transfer caused by thermal conduction and convection in the whole PEM fuel cells system can be quantified by the heat transfer rate equation [26][27][28].…”

“…Nevertheless, this would dehydrate the membranes more quickly. Therefore, it can be seen that relative humidity need to satisfy certain range just like dynamic temperature, and the relative humidity is inextricably linked with dynamic temperature and heat .…”