Research on water and heat management in the cold start process of proton exchange membrane fuel cell with expanded graphite bipolar plate

Abstract

Water storage space and heat capacity are important factors affecting the cold start ability of fuel cell, and heat capacity is affected by materials. In the present study, the lumped static model and two-dimensional dynamic prediction model of the fuel cell with expanded graphite bipolar plates were established. The relationship between water storage space, heat production, heat capacity and the maximum temperature rise is analyzed based on the theoretical calculation model, and the cold start ability is also predicted. The calculation results show that the heat capacity of the bipolar plate is 1.3 J/K·cm2, which accounts for the largest proportion of 34% of all components. With the help of the heat generated by the air compressor, the reactor can be started in 100 s at −30 ℃ and 1.2A/cm2. The temperature difference in the reactor during cold start-up is about 2℃, which proves the reasonability of the isothermal assumption in the static model. The dynamic impedance spectroscopy experiment results show that the super cooled water icing during the cold start will cause the gas transmission impedance to increase rapidly, indicating that the icing mainly occurs at the pores or interfaces inside the catalyst layer and the gas diffusion layer during the cold start.