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

Ashley Fly,Kyoungyoun Kim,Daniel Butcher,Rui Chen,John Gordon

doi:10.3390/en12071186

Ashley Fly, Kyoungyoun Kim + Show 3 more

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https://doi.org/10.3390/en12071186

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Journal: Energies	Publication Date: Mar 27, 2019
Citations: 15	License type: CC BY 4.0

Affiliation: Loughborough University, Hanbat National University

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.

Highlights

IntroductionThe flow-field plate in a proton exchange membrane fuel cell (PEMFC), often referred to as the flow-field, must effectively serve multiple functions simultaneously to achieve good cell performance
The liquid water droplets are airflow visualised isosurface of α = in Initially, liquid to water moved in the direction of the (a),using beforethe suddenly decreasing velocity (b),the moving the moved in the direction of the airflow (a), before suddenly decreasing in velocity (b), moving to the opposite direction of flow (c), and adhering to adjacent metal foam (d), before the droplet size opposite direction of flow (c), and adhering to adjacent metal foam (d), before the droplet size increased (e)
Liquid water transport in a porous metal foam flow-field has been investigated through ex-situ visualisation and two-phase numerical modelling with application to Proton exchange membrane fuel cells (PEMFCs)

Summary

Introduction

The flow-field plate in a proton exchange membrane fuel cell (PEMFC), often referred to as the flow-field, must effectively serve multiple functions simultaneously to achieve good cell performance. The ideal flow-field plate should have a high electrical and thermal conductivity for electron and heat transport, have good mechanical and chemical stability, provide even reactant distribution across the cell active area and maintain membrane humidity whilst facilitating the removal of product water [1]. The channel area allows for reactant gas distribution and product water removal, whereas the rib area is in contact with the gas diffusion layer (GDL) to provide mechanical strength and electron transport to the external circuit. The design of traditional flow channels has received significant attention in the literature, with many numerical and experimental studies focusing on flow channel layout [2], shape [3] and wall hydrophobicity [4].

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