| 摘要 |
A fuel cell system is described having an active system for controlling local gas velocity in flow field channels by changing the gas channel cross sectional area depending on local relative humidity and state of water (i.e., vapor/liquid), thereby improving the removal of liquid water in a flow field channel. For example, a flow field channel is coated or otherwise provided with a material that swells in the presence of water vapor and/or liquid water, such as but not limited to super-absorbent materials. As the swelling continues, the channel gets narrower and the increased gas velocity leads to increased shear forces that improve the movement of the liquid water along the channel out of the cell. The water-uptake and swelling behavior is reversible and the channel will get wider as soon as the liquid is removed and/or the relative gas humidity is decreased.
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