Dynamic contact angle modeling of droplet reattachment at the gas channel wall in polymer electrolyte fuel cells

Abstract

Abstract Energy security, climate change and air pollution are all motivations for further development of fuel cells. Still, technical problems relating to water management, continue to hinder the marketability of polymer electrolyte fuel cells (PEFCs). The impact of dynamic contact angle (CA) boundary conditions, according to the Kistler model, is evaluated in this paper with the VOF approach, focusing on droplet reattachment at the gas channel wall. From this, it is clear that dynamic CA boundary conditions, compared to static CA boundary conditions, significantly influence the droplet reattachment characteristics, for example for the standard case with a gas velocity of 10 m/s, the first droplet awaits attachment to the channel wall on the side opposite the gas diffusion layer surface for a second droplet before merging and then moving out of the channel together, attached to the channel wall. The impact from dynamic CAs becomes even bigger for lower velocities (5 m/s in this case), where the droplet residence time increases significantly. It is clear that the channel dimensions, gas inlet velocity and value of CAs, as well as if a static or dynamic CA model is used, all have a significant impact on the droplet characteristics in PEFC GCs.