Multiphase flow model to study channel flow dynamics of PEM fuel cells: deformation and detachment of water droplets

摘要

Deformation and detachment conditions for a water droplet adhering to the surfaces of the cathode in PEM fuel cells are investigated. This problem is numerically modelled by considering the dynamic behaviour of a droplet located between two parallel plates. The numerical multiphase flow model is based on solving Navier-Stokes equations for Newtonian fluids in the channel. The study includes the effect of interfacial forces with constant surface tension. The volume-of-fluid method is used to numerically determine the deformation of free surfaces. Water droplet and channel fluid properties, inlet velocity and droplet size determine whether a droplet can separate from the surface or just deforms and remains stationary. The critical conditions for the droplet break-up are determined based on the Reynolds and Capillary numbers. Effects of droplet size relative to the channel width, density and viscosity ratios between the water droplet and oxidant fluid are addressed.