Experimental study of the thermal and power performances of a proton exchange membrane fuel cell stack affected by the coolant temperature

The optimization of thermal management (i.e. improving heat generation and dissipation) in a proton exchange membrane fuel cell (PEMFC) is a vital method to enhance its energy conversion efficiency. However, few studies have focused on the temperature uniformity in a massive PEMFC stack with a coolant flow channel. The aim of this study is to investigate the temperature characteristics and power performance affected by the inlet coolant condition in a massive PEMFC stack and establish a correlation of the temperature uniformity with the affected inlet coolant temperature for thermal management and power performance improvements in PEMFCs. The power density of a massive PEMFC stack with an active area of 326 cm2 (302 mm x 108 mm) of the designed stack cells with a coolant flow channel were experimentally evaluated, and the thermal characteristics were also analyzed using monitored temperatures inside specific stack cells by considering the different inlet coolant temperatures of 50 degrees C, 60 degrees C and 70 degrees C. It was found that the stack had the greatest power performance and minimum temperature increment of the inlet coolant at a temperature of 70 degrees C. The water phase transition heat transfer inside the stack was found to play a significant role in the thermal balance. The temperature distribution of the stack cell had a symmetrical convex curve from the center to the margin. The temperature gradient of the stack cell along the coolant flow direction was introduced to characterize the temperature uniformity. The linear development between the temperature gradient and the current density was determined adequately using a curve fitting. In addition, a lower fitting linear slope was obtained for a higher inlet coolant temperature, and this signified that a higher inlet coolant temperature could improve the temperature uniformity and power performance of PEMFCs.