InterPore2026

Modelling of gas flow regimes in anodic flow channels of PEMWE

22 May 2026, 10:20

1h 30m

Poster Presentation (MS17) Electrochemical Processes in Porous Media Poster

Speaker

Mr Ahmed Elewaily (Institute of Fluid Dynamics and Environmental Physics in Civil Engineering, Leibniz Universität Hannover)

Description

In proton exchange membrane water electrolysis (PEMWE), schematically illustrated in the attached figure, mass-transport processes in the anodic channels contribute significantly to performance losses. These channels carry liquid water and a gas phase mainly consisting of electrochemically generated oxygen, and the corresponding gas flow regimes strongly influence local mass-transport resistance and overall efficiency. Experimental studies have shown that annular flow and large gas slugs are associated with increased mass-transport losses and reduced efficiency [1–4]. These flow regimes depend on both operating conditions and the geometrical design of the channels, and their complex dependence on current density and flow rate makes modelling a valuable tool for identifying favourable designs and operating conditions.

In this work, we develop a two-phase CFD model that explicitly resolves the gas flow patterns in the anodic flow channels. To the best of our knowledge, no study has yet modelled the flow regimes over a range of current densities, flow rates, and flow-field designs. Two key modelling assumptions are introduced. First, gas evolution at the porous transport layer (PTL)-channel interface is represented by an array of injectors on the channel wall, which mimic detachment sites but avoid explicit modelling of the electrochemistry. The gas mass flow rate at each injector is calculated from Faraday’s law based on the applied current density. Second, fully wetted channel walls are imposed to maintain a continuous water film without film-refinement techniques or complex dynamic contact angle models.

The injector concept accounts for the influence of the PTL microstructure on gas emergence without resolving the porous medium itself. The spatial density of injectors is chosen according to the measured number of detachment sites per unit area at the PTL–channel interface reported by Wang et al. [5], such that the computational domain can be restricted to the channel flow fields. The simulations are performed with OpenFOAM, using a geometric Volume-of-Fluid (VOF) interface-capturing method for the water/gas system.

The model is validated in three steps: (i) bubble size generated from a single injector is compared to the experimental measurements of Li et al. [6] at different flow rates; (ii) flow regimes at different current densities are qualitatively validated against the high-speed visualisations of Wu et al. [7]; and (iii) regime changes and large-slug size with liquid flow rate, qualitatively compared with the experimental findings of Wang et al. [5]. The framework is then applied to three anode flow-field designs (single serpentine, parallel, and pin-type channels) to investigate the impact of channel design on the gas flow regimes.

The simulations show that the model can produce the formation of large bubbles and slugs and the transitions from dispersed bubbly flow to slug and annular flow under relevant operating conditions. At the same time, the present resolution and modelling assumptions limit the accurate representation of very small bubbles, particularly in the inlet segments of the channels. The resulting flow regimes from the model can provide a basis for understanding the link between operating conditions, gas flow patterns, and mass-transport losses in PEMWE anodes.