Fundamental Understanding of Water Movement in Gas Diffusion Layer under Different Arrangements Using Combination of Direct Modeling and Experimental Visualization

Abstract

In this paper, direct-modeling-based Lattice Boltzmann Method (LBM) combined with in-situ flow visualization, is used to explore fundamentally the transport of liquid-water inside the gas-diffusion layers (GDLs) used in polymer electrolyte fuel cells. Studies of the water evolution, water saturation, and breakthrough pressure inside a GDL with single and multiple injection points under land and channel geometries are explored. The model and experiment demonstrate good agreement between geometries of GDLs provided in this study which were obtained by a three-dimensional (3-D), reconstructed micro-structure from micro X-ray computed tomography (CT). The overall predictions of water evolution within the GDL agree well with the data visualized from the X-ray CT experiment for all cases studied. It also reveals that the liquid-water saturation profiles inside the GDL and breakthrough pressure are different when the location of the water injection point is altered, thereby providing analysis as to the impact of microporous layers or catalyst-layer functioning. Moreover, the uncompressed GDL undergoes a significantly different mechanism of water transport than that of the compressed GDL. Furthermore, the predictions show that the wettability variation is one of the key factors of the saturation characteristics.

Two-phase flow and oxygen transport in the perforated gas diffusion layer of proton exchange membrane fuel cell

“…We compared the symmetry and no-slip boundary conditions in our simulation, and found almost the same predictions. In addition, because of the asymmetry in GDL it is preferred to adopt the no-slip boundary at the GDL sides for large GDL samples [54]. The size of present study (the cross section 800 lm  800 lm) is nearly four times of previous studies and large enough to exclude the effects of the GDL sides [36,39,43,44].…”

“…In this study, the details of gas flow in the flow channel are not specified to better focus on the internal two-phase flow in the microstructures of GDL. This simplification has been widely accepted in the two-phase models of reconstructed GDLs [36,39,[43][44][45][46][47][48]53,54]. In practical PEMFC operation, a number of perforations are usually manufactured in the GDL under the flow channel.…”

“…In this study, only liquid water intrusion is studied. In addition, the assumption of constant contact angle has been widely used to study two-phase flows in GDLs [35][36][37][38][39][40][41][42][43][44][45][46][47][48]53,54,56].…”

Two-Phase Flow in Porous Electrodes of Proton Exchange Membrane Fuel Cell

“…(1) X-CT [12][13][14][15] (2) Stochastic model [16][17][18] (1) Effects of GDL materials [69][70][71], porosities [10,72,73], and PTFE treatment [74][75][76][77][78][79] (2) GDL structural modification: MPL [8], groove, and perforation [80][81][82][83][84][85][86][87][88] (3) Structural deformation: compression [91][92][93][94][95][96][97][98] effect was whether the sample was cracked. In addition, the relationship between capillary pressure and saturation was measured.…”

“…Third, the effects of structural deformation on water management were investigated. During preloading and assembly, the GDL suffered deformation due to the clamping pressure [91][92][93][94][95][96][97][98]. The compression of the GDL reduced the porosity.…”