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Research Papers

Study of Water Droplet Removal on Etched-Metal Surfaces for Proton Exchange Membrane Fuel Cell Flow Channel

[+] Author and Article Information
S. Shimpalee

Department of Chemical Engineering,
University of South Carolina,
Columbia, SC 29208
e-mail: shimpale@cec.sc.edu

V. Lilavivat

National Metal and Materials Technology Center,
National Science and Technology Development Agency,
114 Thailand Science Park,
Pathum Thani 12120, Thailand

1Corresponding author.

Manuscript received November 4, 2015; final manuscript received March 7, 2016; published online April 5, 2016. Assoc. Editor: Matthew Mench.

J. Electrochem. En. Conv. Stor. 13(1), 011003 (Apr 05, 2016) (7 pages) Paper No: JEECS-15-1004; doi: 10.1115/1.4033098 History: Received November 04, 2015; Revised March 07, 2016

Within a proton exchange membrane fuel cell (PEMFC), the transport route of liquid water begins at the cathode catalyst layer, and then progresses into the gas diffusion layer (GDL) where it then goes into the flow channel. At times, significant accumulation of liquid droplets can be seen on either side of the membrane on the surface of the flow channel. In this work, liquid water and the flow dynamics within the transport channel were examined experimentally, with the channel acting as an optical window. Ex situ interpretations of the liquid water and flow patterns inside the channel were established. Liquid water droplet movements were analyzed by considering the change of the contact angle with different flow rates. Also, various surface roughness of stainless steel was used to determine the relationships between flow rate and the contact angles. When liquid water is found within the gas channels of PEMFCs, the channels' characteristic changes become more dominant and it becomes more of a necessity to monitor the effects. Physical motion of water droplets in the flow channels of PEMFCs is important. The surface roughness properties were used to describe the contact angle and the droplet removal force on the stainless steel flow channel.

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Figures

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Fig. 1

Schematic of contact angle of droplet wetted to surface

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Fig. 2

Photograph of the flow channel used in this study (channel width = 4 mm, channel depth = 2 mm, and channel length = 120 mm)

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Fig. 3

AFM images of cross sections and 3D of the sample's surfaces

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Fig. 4

Schematic of the drop in the flow channel used in this study

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Fig. 5

(a) Image of the droplet in the presence of air flow and (b) schematic view of control volume chosen for analysis

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Fig. 6

Static contact angle and height of 10 μl water droplet on stainless steel plate

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Fig. 7

Schematic illustration of the surface model with a series of uniform needles

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Fig. 8

Dynamic images of the water droplet on electrochemically etched stainless steel plate (Ra = 0.73 μm) at different Re

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Fig. 9

Water droplet profile at different Reynolds numbers: (a) Ra = 0.02 μm, (b) Ra = 0.27 μm, (c) Ra = 0.30 μm, (d) Ra = 0.41 μm, and (e) Ra = 0.73 μm. _____: RE = 0; ........: RE = 185, _ _ _ _ _ : RE = 370; _ . _.: RE = 555; __ __: RE= 740; __ . __: RE = 925.

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Fig. 10

The plot of pressure drop at critical point versus surface roughness (Ra)

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Fig. 11

Total drag force versus Reynolds number for different roughness surface

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Fig. 12

Relationship between the roughness factor times solid area fraction rf and the total drag force

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