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Technical Briefs

Critique and Improvement of a One-Dimensional Semianalytical Model of a Direct Methanol Fuel Cell

[+] Author and Article Information
C. C. Kuo

Department of Mechanical and Aerospace Engineering,  University of Florida, Gainesville, FL 32611s222174@ufl.edu School of Engineering, University of North Florida, Jacksonville, FL 32224s222174@ufl.edu

W. E. Lear

Department of Mechanical and Aerospace Engineering,  University of Florida, Gainesville, FL 32611lear@ufl.edu School of Engineering, University of North Florida, Jacksonville, FL 32224lear@ufl.edu

J. H. Fletcher

Department of Mechanical and Aerospace Engineering,  University of Florida, Gainesville, FL 32611jfletche@unf.edu School of Engineering, University of North Florida, Jacksonville, FL 32224jfletche@unf.edu

O. D. Crisalle1

Department of Chemical Engineering,  University of Florida, Gainesville, FL 32611crisalle@che.ufl.edu

1

Corresponding author.

J. Fuel Cell Sci. Technol 9(5), 054501 (Aug 17, 2012) (11 pages) doi:10.1115/1.4006842 History: Received May 05, 2011; Revised April 11, 2012; Accepted May 02, 2012; Published August 17, 2012; Online August 17, 2012

A constructive critique and a suite of proposed improvements for a recent one-dimensional semianalytical model of a direct methanol fuel cell are presented for the purpose of improving the predictive ability of the modeling approach. The model produces a polarization curve for a fuel cell system comprised of a single membrane-electrode assembly, based on a semianalytical one-dimensional solution of the steady-state methanol concentration profile across relevant layers of the membrane electrode assembly. The first improvement proposed is a more precise numerical solution method for an implicit equation that describes the overall current density, leading to better convergence properties. A second improvement is a new technique for identifying the maximum achievable current density, an important piece of information necessary to avoid divergence of the implicit-equation solver. Third, a modeling improvement is introduced through the adoption of a linear ion-conductivity model that enhances the ability to better match experimental polarization-curve data at high current densities. Fourth, a systematic method is advanced for extracting anodic and cathodic transfer-coefficient parameters from experimental data via a least-squares regression procedure, eliminating a potentially significant parameter estimation error. Finally, this study determines that the methanol concentration boundary condition imposed on the membrane side of the membrane-cathode interface plays a critical role in the model’s ability to predict the limiting current density. Furthermore, the study argues for the need to carry out additional experimental work to identify more meaningful boundary concentration values realized by the cell.

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Copyright © 2012 by American Society of Mechanical Engineers
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References

Figures

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Figure 2

Polarization curves for different methanol concentrations after convergence versus the experimental data of [14]. The discrepancies at high current density region are displayed for all cases. The dashed line represents the result of the premature interruption of numerical iterations.

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Figure 3

Polarization curves after applying the modeling refinements proposed and the standard MEM/CCL boundary condition CIIIM=0

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Figure 4

Modeled methanol concentration profiles through the MEA for three MEM/CCL concentration boundary conditions at a bulk methanol concentration of 0.5M

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Figure 5

Modeled polarization curves for three MEM/CCL concentration boundary conditions at a bulk methanol concentration of 0.5M

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Figure 1

Schematic of the simulation domain of a DMFC

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