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Article

# Flow Structures in a U-Shaped Fuel Cell Flow Channel: Quantitative Visualization Using Particle Image Velocimetry

[+] Author and Article Information
J. Martin, P. Oshkai, N. Djilali

Institute for Integrated Energy Systems and Department of Mechanical Engineering, University of Victoria, PO Box 3055 STN CSC, Victoria, BC V8W 3P6, Canada

J. Fuel Cell Sci. Technol 2(1), 70-80 (Aug 16, 2004) (11 pages) doi:10.1115/1.1843121 History: Received July 27, 2004; Revised August 15, 2004; Accepted August 16, 2004

## Abstract

Flow through an experimental model of a U-shaped fuel cell channel is used to investigate the fluid dynamic phenomena that occur within serpentine reactant transport channels of fuel cells. Achieving effective mixing within these channels can significantly improve the performance of the fuel cell and proper understanding and characterization of the underlying fluid dynamics is required. Classes of vortex formation within a U-shaped channel of square cross section are characterized using high-image-density particle image velocimetry. A range of Reynolds numbers, $109⩽Re⩽872$, corresponding to flow rates encountered in a fuel cell operating at low to medium current densities is investigated. The flow fields corresponding to two perpendicular cross sections of the channel are characterized in terms of the instantaneous and time-averaged representations of the velocity, streamline topology, and vorticity contours. The critical Reynolds number necessary for the onset of instability is determined, and the two perpendicular flow planes are compared in terms of absolute and averaged velocity values as well as Reynolds stress correlations. Generally, the flow undergoes a transition to a different regime when two recirculation zones, which originally develop in the U-bend region, merge into one separation region. This transition corresponds to generation of additional vortices in the secondary flow plane.

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## Figures

Figure 1

Schematic of a serpentine gas flow channel

Figure 2

Schematic of the experimental setup

Figure 3

Schematic of PIV setup for image acquisition in streamwise (a) and cross-flow (b) planes

Figure 4

Estimation of the radius of curvature of the channel

Figure 5

Instantaneous flow field at Re=109 in streamwise (a) and cross-flow (b) planes. Clockwise from top left: velocity vector field, velocity streamlines, velocity magnitude, and out-of-plane vorticity contours.

Figure 6

Instantaneous flow field at Re=382 in streamwise (a) and cross-flow (b) planes. Clockwise from top left: velocity vector field, velocity streamlines, velocity magnitude, and out-of-plane vorticity contours.

Figure 7

Streamwise plane: Instantaneous flow fields at Re=872. From top to bottom: velocity vector field, out-of-plane vorticity contours, velocity streamlines, and velocity magnitude.

Figure 8

Cross-flow plane: Instantaneous flow fields at Re=872. From top to bottom: velocity vector field, out-of-plane vorticity contours, velocity streamlines, and velocity magnitude.

Figure 9

Ratio of the maximum secondary velocity to the maximum primary velocity and ratio of the maximum secondary out-of-plane vorticity to the maximum primary out-of-plane vorticity as functions of Reynolds number

Figure 10

Patterns of root-mean-square velocity fluctuations in the streamwise plane

Figure 11

Patterns of root-mean-square velocity fluctuations in the cross-flow plane

Figure 12

Patterns of Reynolds stress correlation in the streamwise plane

Figure 13

Patterns of Reynolds stress correlation in the cross-flow plane

## Errata

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