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Membrane

Nafion® 115

Nafion® 115

Fig.l Photograph of 200 cm2 x 36-cell module.

RESULTS ANT) DISCUSSIONS

(1)Influence of air flow speed

Figure 2 shows relationship between cell voltage and air flow speed through the air channel of 200 cm2 single cells. When the relative air flow speed was less than 5, no cell voltage change was observed at (he air utilization of 20 %. But in case of air utilization of 46 %, higest voltage was obtained when the relative air flow speed was 5. It was considered that air channel closing by the product water was restricted by increasing the air flow speed. It was found that better cell performance was obtained even at high air utilization by increasing the air flow speed.

(2)Influence of Teflon® amount on the carbon backing paper

Figure 3 shows relationship between cell volrage and Teflon® amount on the carbon backing paper. When air utilization was 40 %, cell voltage tended to lower with increasing Teflon® amount on the carbon backing paper. Wetproofing property of the backing carbon paper becomes distinct when the Teflon® amount increases. However, excess wetproofing property leads to lower water drawing from the cathode. That seemed to be why the cell voltage with large Teflon® amount on the backing carbon paper lowered at air utilization of 40 %. It was found that less than 15 \vt% of Teflon® amount was desirable for the cathode backing carbon paper.

©Module operating test

Figure 4 shows the relationship between module voltage and air utilization. The dependence of air utilization on module voltage was remarkably improved and good performance was obtained even at- high air

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