Impact of Fin Configuration on the Thermal Efficiency of Helical Coil Heat Exchangers in Metal Hydride Hydrogen Storage Systems

Abstract

Abstract. The transportation and storage of hydrogen, particularly in automotive applications, remain significant challenges to its widespread utilization. Among the various methods explored, metal hydride (MH)-based storage of hydrogen is gaining momentum due to its unique characteristics, making it well-suited for stationary and automotive applications. An efficient MH storage system requires an effective heat exchange mechanism, as the ab/desorption kinetics involve exothermic and endothermic reactions. This study developed a comprehensive mathematical model to capture the kinetics, mass transfer, and heat transfer processes in an MH system. The validated model was subsequently employed to examine how adding fins to the surface of a helical coil heat exchanger influences hydrogen storage capacity and heat transfer efficiency. The findings reveal that adding fins to the helical coil significantly enhances heat transfer and absorption rates. Notably, the duration needed to reach 90% saturation of the MH bed's maximum storage capacity is reduced by 11.11%. A comprehensive study was conducted to investigate the influence of fin dimensions on the performance of MH bed. The rate of achieving 90% hydrogen storage improves by 17.64% when the fin width increases from 3 mm to 6 mm. Similarly, it improves by 16.6% when the thickness of the fin increases from 0.5 mm to 2 mm. However, further increases in the fin dimensions do not yield significant improvements, attributing to the inherently poor heat conduction capability of the metal powder.