Improvement of water discharge from gas diffusion layer to gas channel with obliquely-directed micro-grooves arranged inside channel walls

Polymer electrolyte fuel cell (PEFC) is expected to be used with the power sources for the automobile and the cogeneration power source for home and so forth. At the cathode-side of a PEFC, oxygen is transported as the reactant gas from gas channel through gas diffusion layer (GDL) to the catalyst layer. However, the large quantity of moisture is generated under the situation of the high power generation. Since, as a result, the moisture blocks transporting oxygen, the cell voltage falls off drastically. The objective of this study is to improve the management of moisture from GDL in gas channels of separator for PEFC. The oblique micro-grooves are manufactured inside gas channel walls. Water from GDL is discharged through the micro-grooves to upper-side of gas channel by surface tension and shearing force generated by air flow. Velocity of water flowing in the micro-grooves was measured by using the laser induced fluorescence method. It was confirmed experimentally that micro-grooves manufactured inside gas channel worked properly, that is, water discharge from GDL to upper-side of channel was succeeded. The water velocity and effective length of micro-grooves to remove water from GDL surface increased with the decrease in inclination angle θ of micro-grooves in this experimental range of θ =20~40 ° . It was shown that the effective length of approximately 200mm, which was overall length of experimental apparatus, was attained.