Enhancing water hydration in air-cooled proton exchange membrane fuel cell using a staggered tapered slotted flow field

Abstract

Air-cooled proton exchange membrane fuel cell (AC-PEMFC) is widely considered as a promising power source for unmanned aerial vehicles (UAVs) due to its merits such as high energy density, short refueling time, and simple auxiliary system. However, the performance of AC-PEMFC is not satisfactory due to the poor membrane hydration caused by the large air supply for heat dissipation demand. This study proposes a staggered tapered slotted flow field (STSF) configuration to address this issue, which has higher contact area between the airflow and the bipolar plate by arranging tapered and slotted sections in the channels along the airflow direction, aiming to enhance the cooling effect and improve the membrane water hydration. Utilizing a three-dimensional (3D) multiphase non-isothermal model verified against experimental data, it was found that the STSF configuration reduces the internal temperature of the cell by about 14.2–28.3 K and increases the water content in the membrane by about 35.1–85.7 % compared with traditional straight channels. In addition, the STSF configuration can enhance mass transfer by inducing cross-flow, reducing concentration losses, which takes more effect for UAVs working at high altitude. Moreover, the slotted sections reduced the volume and weight of the bipolar plates, contributing to an additional power density improvement. Finally, the pressure drop within the flow channels and net power was compared. Due to the increased contact area between the cooling airflow and the bipolar plates, the STSF configuration inevitably results in a higher pressure drop within the channels, but the net power of PEMFC with STSF still increased under severe conditions by 0.080 W.