Transport in PEMFC Stacks - DOE Hydrogen and Fuel Cells ...
Transport in PEMFC Stacks - DOE Hydrogen and Fuel Cells ...
Transport in PEMFC Stacks - DOE Hydrogen and Fuel Cells ...
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Achievements: New Materials: Diffusion Media<br />
• Ballard added to the<br />
program recently<br />
• Started with Toray<br />
Materials<br />
– Variable Wet-Proof<strong>in</strong>g<br />
– Microporous Layer<br />
• Ballard will provide more<br />
custom materials<br />
• Want to generate<br />
differences <strong>in</strong>:<br />
– MacMull<strong>in</strong> Number<br />
• Porosity<br />
• Tortuosity<br />
– Hydrophobicity<br />
•Tortuosity<br />
– Ratio of the actual path<br />
length through the pores to<br />
the shortest l<strong>in</strong>ear distance<br />
between two po<strong>in</strong>ts.<br />
•Porosity<br />
– Ratio of void volume (volume<br />
of pores) to the total volume.<br />
•MacMull<strong>in</strong> Number<br />
– Function of tortuosity <strong>and</strong><br />
pososity.<br />
N<br />
M<br />
L<br />
t<br />
V Pores<br />
V Total<br />
n<br />
τ<br />
= f ( τε , ) =<br />
m<br />
ε<br />
τ =<br />
L<br />
t<br />
V<br />
ε =<br />
V<br />
Pores<br />
Total<br />
This presentation does not conta<strong>in</strong> any proprietary, confidential,<br />
or otherwise restricted <strong>in</strong>formation<br />
12
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