Simplified models for predicting the onset of liquid water droplet instability at the gas diffusion layer/gas flow channel interface

2005 ◽  
Vol 29 (12) ◽  
pp. 1113-1132 ◽  
Author(s):  
Ken S. Chen ◽  
Michael A. Hickner ◽  
David R. Noble
Keyword(s):  
Diffusion Layer ◽  
Liquid Water ◽  
Water Droplet ◽  
Gas Flow ◽  
Gas Diffusion Layer ◽  
Gas Diffusion ◽  
Flow Channel ◽  
Simplified Models

Experimental Studies of Liquid Water Droplet Growth and Instability at the Gas Diffusion Layer/Gas Flow Channel Interface

2005 ◽  
Author(s):  
Michael A. Hickner ◽  
Ken S. Chen
Keyword(s):  
Contact Angle ◽  
Diffusion Layer ◽  
Liquid Water ◽  
Water Droplet ◽  
Gas Flow ◽  
Contact Angle Hysteresis ◽  
Gas Diffusion Layer ◽  
Gas Diffusion ◽  
Flow Channel ◽  
Water Droplets

Experimental investigations were carried out to visualize the dynamic behavior (contact angle hysteresis and droplet shape) of liquid water droplets on carbon paper gas diffusion layers that are typically employed in proton exchange membrane fuel cells (PEMFCs). The experimental technique mimicks the generation of liquid water and formation of droplets in an air shear flow at the gas diffusion layer – gas flow channel interface of a simulated PEMFC cathode. Images obtained of growing liquid water droplets yield information on the contact angle hysteresis and droplet height, which were subsequently used to map droplet “instability” diagrams. These instability diagrams provide quantitative guidance on liquid water droplet removal at the gas diffusion layer/gas flow channel interface under the conditions of interest. The experimentally mapped droplet diagrams are compared with those predicted using a simplified model based on a macroscopic force balance and reasonably good agreement is obtained.

A Review of Models for Water Droplet Detachment From the Gas Diffusion Layer-Gas Flow Channel Interface in PEMFCs

2007 ◽  
Author(s):  
Charles H. Schillberg ◽  
Satish G. Kandlikar
Keyword(s):  
Diffusion Layer ◽  
Water Droplet ◽  
Gas Flow ◽  
Proton Exchange Membrane ◽  
Gas Diffusion Layer ◽  
Gas Diffusion ◽  
Channel Length ◽  
Flow Channel ◽  
Proton Exchange ◽  
Droplet Detachment

Understanding the fundamental mechanisms of water transport in proton exchange membrane fuel cells (PEMFCs) is necessary for effective management of product water. Among the transport mechanisms affecting the performance of PEMFCs are droplet formation, growth, and detachment at the gas diffusion layer (GDL)-gas flow channel interface. The presence of water droplets on the GDL blocks the access of gases to the reaction sites, increases channel pressure drop, and creates inconsistencies in the gas velocity fields down the channel length, all resulting in performance deterioration. In order to gain an insight into controlling droplets, an in-depth review of PEMFC water droplet detachment models published in the literature is presented here. Summaries of supporting data, modeling techniques, and conclusions are also presented.

Modeling of Flooding Phenomena in Hydrophobic Gas Diffusion Layer of PEFC

2007 ◽  
Author(s):  
Kazuhiko Kudo ◽  
Akiyoshi Kuroda ◽  
Shougo Takeoka ◽  
Yosuke Shimazu
Keyword(s):  
Diffusion Layer ◽  
Liquid Water ◽  
Air Flow ◽  
Gas Diffusion Layer ◽  
Gas Diffusion ◽  
Flow Channel ◽  
Cathode Side ◽  
Model Following ◽  
Condensed Water ◽  
Different Diameters

The mechanism of liquid water removal, water vapor diffusion and oxygen diffusion in cathode side gas diffusion layer (GDL) of PEFC is studied by modeling the GDL as a hydrophobic flat plate with many straight holes with different diameters. As the results of the consideration using the model, following results are obtained. The spots where liquid water condensation is taken place between GDL-MEA gap are limited to the inlets of holes with larger diameters, and the condensed water is drained to air flow channel only through the larger holes. Other holes with smaller diameters are free of liquid water, and oxygen diffuses from the air flow channel to the catalyst surface through such holes. The reduction of output voltage of fuel cell due to the increase in the current density may be caused by the reduction of the oxygen concentration in GDL-MEA gap. The condensate tends to penetrate into larger holes instead of filling the gap of GDL and MEA.

Effect of Gas Diffusion Layer Surface Wettability Gradient on Water Behavior in a Serpentine Gas Flow Channel of Proton Exchange Membrane Fuel Cell

2018 ◽  
Vol 140 (8) ◽  
Author(s):  
Sneha Malhotra ◽  
Sumana Ghosh
Keyword(s):  
Fuel Cell ◽  
Diffusion Layer ◽  
Gas Flow ◽  
Proton Exchange Membrane ◽  
Gas Diffusion Layer ◽  
Gas Diffusion ◽  
Flow Channel ◽  
Proton Exchange ◽  
Surface Wettability ◽  
Exchange Membrane

Water removal and behavior, in proton exchange membrane fuel cell (PEMFC) gas flow channel has been investigated in this work. Single serpentine gas flow channel has been simulated. Hydrodynamics of water drops in a serpentine channel are studied as a function of nature of gas diffusion layer (GDL) surface wettability. In one case, the surface becomes gradually hydrophobic starting from 90 deg to 170 deg. In this second case, the value of contact angle reduces to 10 deg. A three-dimensional model has been developed by using cfd software. Two different drop of diameter 0.2 mm and 0.4 mm are simulated for all the cases. It is observed that, water coverage is always lesser for a gradual hydrophobic surface. Also at low air velocity and gradual hydrophobic GDL surface results in lesser pressure drop as well as water coverage.

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