Numerical quantification of water saturation, back diffusion, electro-osmotic drag and water generation in polymer electrolyte membrane fuel cells

Författare

Munir Khan
Bengt Sundén
Jinliang Yuan

Summary, in English

A 3D unit cell has been simulated numerically using a commercial software

in order to evaluate and quantify various water related phenomena,

i.e., electro-osmotic drag, back diffusion, electro-chemical water generation

and the saturation effects in the porous media. The water saturation

effects were noticed to be more pronounced in the GDL of the cathode

as compared to the catalyst layer due to greater pore dimensions. Also,

a comparison of the water saturation effects were studied at different operating

voltages of 0.7, 0.5 and 0.3 V. In case of 0.7 and 0.5 V, it was

seen that the saturation effects were found to be located in the far region

of the inlet because of the decreasing ability of air to accommodate more

water. But, at the lower voltage of 0.3, the saturation effects started to

appear in the inlet region too due to strong electro-osmotic drag and water

generation due to electro-chemical reactions. The transfer of water from

the cathode via back diffusion also increased accordingly by lowering the

operating voltage. Additionally, the transfer rate of water due to the back

diffusion was observed to be larger than the water addition due to both

the electro-osmotic drag and the electro-chemical generation.

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