InterPore2021

Modeling coupled porous media/free flow/drop interaction in a PEM fuel cell using a pore-network approach

3 Jun 2021, 14:55

15m

Oral Presentation (MS19) Electrochemical processes in porous media MS19

Speaker

Cynthia Michalkowski

Description

A sophisticated water management is crucial for improved operating conditions of a polymer electrolyte membrane fuel cell (PEM FC). Therefore, it is necessary to understand the transport mechanisms of water throughout the cell constituents, where the an intelligent use and drainage of the water buffer can be used to enhance performance of the fuel cell. Microscale modeling of diffusion layers and gas distributor has been established as a favorable technique to investigate the ongoing processes.
Investigating the interface between the GDL and gas distributor, a particular challenge is the combination and interaction of the multiphase flow in porous material of the GDL with the free flow in the gas distributor. Drops emerging from the porous domain at the interface have a strong influence on the exchange of mass, momentum and energy between the two flow regimes. Modeling drop-related processes on the pore-scale is usually computationally expensive.
In this talk, I present a computationally efficient approach to model pore-scale drop interface processes: A pore network model captures the pore-scale processes in the porous domain of the GDL. The free-flow domain of a PEM fuel cell gas distributor is reduced to a one-dimensional formulation including the coupled fluxes of the gas and liquid phases in rectangular micro-channels. For the interface, drop formation, growth and detachment are taken into account as well as transport of the components in the gas phase. The coupling of these domains allows an efficient computation of the main influencing phenomena on the pore-scale at the interface between porous medium and channel flow.
I investigate the influence of the reactions and production rates of water in the fuel cell on the interface processes between GDL and gas distributor. In a first scenario, the detached droplets are assumed to be transported away by the gas flux in the channels. In a second scenario, the detached droplets form a liquid film at the channel wall with a saturation dependent transmissibility for both phases.