Research on mass and heat transfer phenomena in micro-channels under freezing condition in PEM fuel cells

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Research was made to identify the phenomena of water production in thin micro-channels under variety of conditions including freezing temperatures Experimental apparatus was developed to allow visual observation of the phenomena inside in the fuel cell. The result of the experiment showed that cell voltage dropped in shorter time with larger current density and the limiting current densities allowing no voltage drop were identified for temperature conditions. Increasing operating pressure promotes water production, and this works preferable for the dry gas operation hut it deteriorates performance under freezing temperatures. Visual observation showed production and flows of liquid water in separator channels, sod good correlation was found between cell voltage change and open areas free from water plugging in channels. The experiment also showed the importance of uniform binding pressure of the cell for the uniform reactions over the cell area. No difference in the visual observation was recognized in the cell before and after the cell voltage drop under freezing conditions, but some change was detected by thermal camera. The meaning of this change will he further investigated in the next research.