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Research Papers

Graduated Resistance to Gas Flow Through a GDL in an Unconventional PEM Stack

[+] Author and Article Information
Terry B. Caston, Kanthi L. Bhamidipati, Haley Carney

George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332

Tequila A. L. Harris1

George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332tequila.harris@me.gatech.edu

1

Corresponding author.

J. Fuel Cell Sci. Technol 8(1), 011003 (Nov 01, 2010) (8 pages) doi:10.1115/1.4002310 History: Received June 09, 2009; Revised July 14, 2010; Published November 01, 2010; Online November 01, 2010

The goal of this study is to design a gas diffusion layer (GDL) for a polymer electrolyte membrane (PEM) fuel cell with a graduated permeability and thereby graduating the resistance to flow throughout the GDL. It has been shown that in using conventional materials, the GDL exhibits a higher resistance in the through-plane direction due to the orientation of the small carbon fibers that make up the carbon paper or carbon cloth. In this study, a GDL is designed for an unconventional PEM fuel cell stack where the reactant gases are supplied through the side of the GDL rather than through flow field channels machined into a bipolar plate. The effects of changing in-plane permeability, through-plane permeability, GDL thickness, and oxygen utilization on the expected current density distribution at the catalyst layer are studied. Three different thicknesses and three different utilizations are investigated. It has been found that a thinner GDL with a lower utilization yields a higher current density on the electrode. A quantitative metric to measure uniformity of reactant distribution and the ratio of the standard deviation of the current density to the average current density was introduced, and it was found that while the uniformity of the reactant distribution is independent of thickness of the GDL, it is inversely proportional to utilization.

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Figures

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Figure 1

Unconventional stack design

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Figure 2

Unconventional GDL concept

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Figure 3

Side view of modeling domain

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Figure 4

Polarization curve

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Figure 5

Mass flux of oxygen into cathode catalyst layer versus position at 11.5 mm cross section

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Figure 6

Effects of varying permeability on current density distribution with a 0.4 mm thick GDL at 75% oxygen utilization: (a) case 1, (b) case 2, (c) case 3, and (d) case 4

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Figure 7

Average current density with standard deviation for a 0.4 mm thick GDL at 75% utilization

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Figure 8

Average current density versus GDL thickness at 75% utilization

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Figure 9

Average current density versus oxygen utilization at a GDL thickness of 0.4 mm

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