Experimental study of air-water interaction in presence of powdered wax inside simulated gas distribution channel of a proton exchange membrane fuel cell

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Low temperature fuel cells such as proton exchange membrane fuel cells are being currently developed to run cars and buses. Water management in these fuel cells is a key issue that needs to be adequately addressed for rapid development of the technology. The fuel cell reaction creates water that is typically carried away by the incoming air. However, at part load operations when the required air supply is lower, water droplets may fully block the air supply channels, leading to inefficient fuel cell operation. A solution to this problem is proposed taking a cue from tiny insects known as aphids that live inside plants. They excrete a watery substance called honeydew and get rid of this water using wax by encapsulating it into tiny droplets. In the present study, air-water interaction in a minichannel is studied in the presence of powdered wax. Air is forced into the channel inlet and water is pumped through a hole on the top wall of the channel. The movement of water inside the channel at different air velocities and water flow rates is recorded using a high-speed camera. Results indicate that the water droplets and slugs formed inside the channel are removed more rapidly in the presence of powdered wax. At the highest water flow rate and lowest air velocity used in this study the unwaxed channel gets completely flooded while the slugs of water continued to move forward in the waxed channel. Different two-phase flow regimes have been identified and plotted in both the waxed and unwaxed channels. Copyright © 2009 by ASME.

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Journal of Fuel Cell Science and Technology