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Research Papers

Flow, Transport, and Reactions in a Thin Layer Flow Cell

[+] Author and Article Information
Jürgen Fuhrmann1

 Weierstrass Institute for Applied Analysis and Stochastics, Mohrenstrasse 89, 10117 Berlin, Germanyfuhrmann@wias-berlin.de

Hong Zhao

 Weierstrass Institute for Applied Analysis and Stochastics, Mohrenstrasse 89, 10117 Berlin, Germanyzhao@wias-berlin.de

Ekkehard Holzbecher

 Weierstrass Institute for Applied Analysis and Stochastics, Mohrenstrasse 89, 10117 Berlin, Germanyholzbecher@wias-berlin.de

Hartmut Langmach

 Weierstrass Institute for Applied Analysis and Stochastics, Mohrenstrasse 89, 10117 Berlin, Germanylangmach@wias-berlin.de

1

Corresponding author.

J. Fuel Cell Sci. Technol 5(2), 021008 (Apr 11, 2008) (10 pages) doi:10.1115/1.2821598 History: Received July 19, 2007; Revised August 30, 2007; Published April 11, 2008

The performance of fuel cells depends on the rate parameters of the kinetic reactions between the involved species, among other conditions. The determination of these parameters is crucial for the understanding of the functionality of fuel cells. Differential electrochemical mass spectroscopy in thin layer flow cells is used as a tool to gain improved understanding of the heterogeneous catalytic reactions taking place in fuel cell catalytic layers. In this paper, we focus on the description of thin layer cells by numerical models based on partial differential equations and the extraction of kinetics parameters by inverse modeling. For the model setup, various software tools are used. The simulation of laminar free flow is performed by the commercial code COMSOL . A finite volume code is used for the simulation of the reactive transport. The latter is coupled with a Levenberg–Marquardt algorithm for the determination of kinetic constants. Two designs of thin layer flow cells are considered: a cylindrical and a rectangular design. A drawback of the cylindrical cell design is the highly inhomogeneous velocity field leading to spatial variations of the conditions for electrode reactions. In contrast, the rectangular cell design shows a homogeneous flow field in the vicinity of the catalyst. The rectangular cell design has the additional advantage that flow is essentially two dimensional and can be computed analytically, which simplifies the numerical approach. The inverse modeling procedure is demonstrated for a hydrogen-carbon monoxide system.

Copyright © 2008 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Cylindrical flow cell after Jusys (1)

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Figure 2

Flow cell described by Holzbecher (2)

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Figure 3

A control volume

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Figure 4

Pressure distribution (top) and streamlines (bottom) in the cylindrical flow cell

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Figure 5

Concentration distribution in the cylindrical flow cell

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Figure 6

Comparison between measured and simulated values for current in the cylindrical flow cell

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Figure 7

Pressure and velocity field in the rectangular flow cell

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Figure 8

x velocity component in rectangular cell (left) and analytical Hagen–Poiseuille profile (right)

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Figure 9

Cross section through the modeling domain

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Figure 10

Experimental and fitted values of the current density (top) and θCO (bottom)

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Figure 11

Distribution of cH2 (top) and cCO (bottom) in mol∕m3 in the flow region at t=200s

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Figure 12

Distribution of cH2 (top) and cCO (bottom) in mol∕m3 in the porous layer at t=200s

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Figure 13

Distribution of θH2 (top), θCO (middle), θPt (bottom), normalized values in the porous layer at t=200s

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Figure 14

Distribution of cH2 (top) and cCO (bottom) in mol∕m3 in the flow region at t=400s

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Figure 15

Distribution of cH2 (top) and cCO (bottom) in mol∕m3 in the porous layer at t=400s

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Figure 16

Distribution of θH2 (top), θCO (middle), θPt (bottom), normalized values in the porous layer at t=400s

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