Polymer electrolyte fuel cells (PEFCs) have water management issues such as the flooding where condensate blocks the pores of the gas-diffusion-layer (GDL), and the plugging where condensate blocks the gas channels. Many researchers have studied these issues on the cathode side using a visualization technique, and have introduced the water repellency processing to the gas channel and GDL to solve these issues. We also confirmed by two-pole simultaneous image measurements that if water generated was transported from the cathode to the anode through the membrane, the flooding/plugging phenomena in the anode gas channel was caused in the comparison low humidity conditions [1]. The cell with the AB-CT configuration (the anode inlet was located at the bottom and the cathode inlet was located at the top) was able to maintain a uniform water distribution in the cell by water transportation through the membrane. Although most researchers confirmed these phenomena using a single cell, cannot confirm them in PEFC stack yet. The PEFC stack has peculiar issues such as flow rate distribution to each cell and temperature distribution in the stack. The supply flow rate to each cell of the stack is decided by the channel loss of each cell, and the temperature of the stack midrange become higher by the exothermic reaction (cell reaction). Moreover, even if only one cell of the stack decreased the cell performance, the cell performance of each cell influences other cells, and causes the performance deterioration of the stack. Therefore, the produced water distribution of the cell in the stack must be different from that of the single cell. However, the gas channel in the stack cannot be directly observed with a usual video camera like the single cell because the thickness of separator for the stack is so thin. Moreover, the resistance of the clear-walled cell (viewing entire gas channel) is elevated because this visualization cell was composed of the heater plate with the observation window and the current collector carved the gas channel. I-V performance of the clear-walled cell was lower than that of the solid-walled cell (the standard cell). For this reason, the results obtained by the clear-walled cell may not correctly express an actual phenomenon. We were able to observe the behavior of the plugging water in a practical PEFC using the visualization cell with three pinpoint windows [2]. We aim to observe the water distribution of each cell in the stack by applying this visualization technique to the PEFC short-stack.
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