In our previous study, we have developed a hybrid pattern gas flow channel design, where a serpentine flow channel is placed between interdigitated flow channels for polymer electrolyte fuel cells (PEFCs). In the present paper, using this flow channel design, we investigate the effects of gas flow direction on the output voltage under non-humidified cathode condition. As a result, we find a gas flow pattern that causes partial flooding by product water accumulation due to the gravity. Moreover, counter flow in the serpentine channel is found to increase the water content in the membrane, so that the fluctuation of the output voltages is suppressed. On the other hand, when the cathode outlet is downside, the above partial flooding is prevented. In addition to choosing this outlet, the counter flow of the serpentine and interdigitated flows is found to be effective to increase average output voltage and to suppress the fluctuation of the output voltage. In this case, the cathode outlet faces the inlet of the anode serpentine channel, where flow velocity is the highest in the anode flow channels. This gas flow pattern leads to sufficient supply of the product water at the cathode outlet to the anode side channels by the back-diffusion. Thus, the fluctuation of the output voltage is also minimized.
