Peclet number analysis of cross-flow in porous gas diffusion layer of polymer electrolyte membrane fuel cell (PEMFC)

Abstract

Adoption of hydrogen economy by means of using hydrogen fuel cells is one possible solution for energy crisis and climate change issues. Polymer electrolyte membrane (PEM) fuel cell, which is an important type of fuel cells, suffers from the problem of water management. Cross-flow is induced in some flow field designs to enhance the water removal. The presence of cross-flow in the serpentine and interdigitated flow fields makes them more effective in proper distribution of the reactants on the reaction layer and evacuation of water from the reaction layer than diffusion-based conventional parallel flow fields. However, too much of cross-flow leads to flow maldistribution in the channels, higher pressure drop, and membrane dehydration. In this study, an attempt has been made to quantify the amount of cross-flow required for effective distribution of reactants and removal of water in the gas diffusion layer. Unit cells containing two adjacent channels with gas diffusion layer (GDL) and catalyst layer at the bottom have been considered for the parallel, interdigitated, and serpentine flow patterns. Computational fluid dynamics-based simulations are carried out to study the reactant transport in under-the-rib area with cross-flow in the GDL. A new criterion based on the Peclet number is presented as a quantitative measure of cross-flow in the GDL. The study shows that a cross-flow Peclet number of the order of 2 is required for effective removal of water from the GDL. Estimates show that this much of cross-flow is not usually produced in the U-bends of Serpentine flow fields, making these areas prone to flooding.

Experimental study of dust deposition in dynamic granular filters

“…In addition, for a very small size of dust particulates, Brownian diffusion plays a key role. The Peclet number Pe can be defined as 30 where K is the Boltzmann constant and T is the absolute temperature. The collection efficiency could exceed 90% for Pe < 1000, which corresponds to particulates smaller than 0.1 μm.…”

Design and Modeling of Metallic Bipolar Plates for a Fuel Cell Range Extender

“…These examples are also documented in the supplementary information of this study. The serpentine shapes were chosen because they provide good under the rib convection as a result of the pressure difference of adjacent channel sections [64][65][66][67]. A detailed description of the pressure differences for the separate serpentine flow field can be found in the PhD thesis of Bendzulla [68].…”

An Engineering Toolbox for the Evaluation of Metallic Flow Field Plates

“…The driving force for this effect is the pressure difference between different sections of the long channels. The amount of this cross over flow depends on the permeability of the porous layer [53] and the pressure difference of the channel segments between two bends [25,[54][55][56][57][58].…”