Metal hydride (MH) based hydrogen storage is one of the potential methods for achieving higher volumetric storage densities than conventional gaseous and liquid storage methods. However, its poor thermal conductivity limits heat transfer during exothermic hydriding and endothermic dehydriding processes. Hence, heat transfer augmentation is essential in MH reactors to speed up the charging and discharging of hydrogen. The present study proposes a novel flat coil tube heat exchanger with a spiral fin for heat transfer augmentation. It offered superior performance than conventional single and double helical tube heat exchangers, taking 35.3% and 16.7% less time for 90% storage time. Further, optimization of design parameters (pitch and fin thickness) is carried out considering several key parameters such as weight ratio (WR), gravimetric exergy output rate (GEOR), and energy efficiency (EE). The optimized reactor has been fabricated, and experimental investigations are carried out to examine the impact of different operational parameters.
Furthermore, a fin efficiency (FE) technique for optimizing fins in a conventional longitudinal finned tube MH reactor utilizing LaNi5 has been introduced. Given the complexities involved, analytically estimating FE presents challenges. As a solution, the authors have adopted a reverse engineering approach. This method uses temporal temperature profiles derived from simulated data to compute the FE. The optimization of the number of fins and their configuration is then performed based on this calculated FE.