Liquid Water Transport in Porous Metal Foam Flow-Field Fuel Cells: A Two-Phase Numerical Modelling and Ex-Situ Experimental Study

Abstract

Proton exchange membrane fuel cells (PEMFCs) using porous metallic foam flow-field plates have been demonstrated as an alternative to conventional rib and channel designs, showing high performance at high currents. However, the transport of liquid product water through metal foam flow-field plates in PEMFC conditions is not well understood, especially at the individual pore level. In this work, ex-situ experiments are conducted to visualise liquid water movement within a metal foam flow-field plate, considering hydrophobicity, foam pore size and air flow rate. A two-phase numerical model is then developed to further investigate the fundamental water transport behaviour in porous metal foam flow-field plates. Both the experimental and numerical work demonstrate that unlike conventional PEMFC channels, air flow rate does not have a strong influence on water removal due to the high surface tensions between the water and foam pore ligaments. A hydrophobic foam was seen to transport liquid water away from the initial injection point faster than a hydrophilic foam. In ex-situ tests, liquid water forms and maintains a random preferential pathway until the flow-field edge is reached. These results suggest that controlled foam hydrophobicity and pore size is the best way of managing water distribution in PEMFCs with porous flow-field plates.

Porous Flow Field for Next-Generation Proton Exchange Membrane Fuel Cells: Materials, Characterization, Design, and Challenges

“…Furthermore, Wu et al 282 compared the water mass in a metal foam flow field under compressions of 3%, 67%, and 69% using in-operando neutron radiography and found that compression improves convective liquid water removal. Fly et al 319 conducted an ex situ experiment to visualize liquid water transport in a metal foam flow field. These authors determined that the effect of the air flow rate on liquid water dynamics is negligible due to the surface tension and solid ligaments.…”

Oxygen transport in proton exchange membrane fuel cells with metal foam flow fields

“…In this study, we reconstruct a 150-μm-thick GDL structure with a fiber diameter of 10 μm and a porosity of 78%. The representative unit cell structure [49][50][51] is adopted to reconstruct the metal foam structures. In this study, the tetrakaidecahedron is selected as the representative unit cell.…”

Hydrogen-Based Energy Conversion: Polymer Electrolyte Fuel Cells and Electrolysis

“…Study on liquid water transport in porous metal foam flow-field using a twophase numerical modelling and an ex situ experimental study in proton exchange membrane fuel cells [10].…”