Numerical study of vapor behavior in high temperature PEM fuel cell under key material and operating parameters

The water issue of high-temperature proton exchange membrane fuel cell (HT-PEMFC) is rarely studied in the previous work. However, the different water vapor behaviors might greatly influence both cell performance and stability. In order to gain a fundamental understanding of the vapor behaviors in HT-PEMFC, a 3D computational fluid dynamics model and a 2D transient model were developed to investigate the effects of materials properties and operating parameters on the vapor behavior. Temperature, membrane materials, and phosphoric acid doping degrees are examined. The results show that higher temperature and phosphoric acid doping degrees with PBI membrane would lead to a significant increase of water vapor generation at cathode. For the transient model, the dynamics of vapor accumulation were observed with the dead-end anode. It is revealed that vapor transport and distribution get adapted to a dynamic equilibrium after 18 sec. According to these results, a periodic purging at anode with optimized purging time is still needed to remove the accumulated water vapor. The findings of this paper can be further applied in the design of fuel cell controller.