Thermal management of metal hydride hydrogen storage using elliptic cooling tubes under an external magnetic field

Abstract

A novel cooling system for hydrogen storage in metal hydride bed is proposed. The system consists of hybrid nanofluid under magnetic field effects and cooling elliptic tubes. Numerical study of the coupled system is considered by using finite element method for different values of magnetic field (MGF) strength (Hartmann number (Ha) between 0 and 60), elliptic tube aspect ratio (AR between 1 and 2.5) and material of metal hydride (MH) bed. Cooling performance is improved by using elliptic tubes with higher aspect ratio and lower isothermal temperature. Higher MGF leads to higher heat transfer from the channel and effect becomes more profound with lower temperatures of the elliptic tubes. At temperature difference (dT) of 0 and 5, absorbed hydrogen amount improvement becomes 15% and 6% at t = 4000 s while they are 25% and 13% at t = 2000 s. Higher aspect ratios of the cylinders lead to absorbed hydrogen increment by about 26% at t = 4000 s. The most important factor influencing the absorption characteristics is the material of MH bed. The highest amount of absorbed hydrogen is obtained when TiCr1.6Mn0.2 is used as the MH material, followed by Hydralloy C5 and MmNi4.6Al0.4 materials. When comparing the worst and best cooling channel options at t = 4000 s, enhancements in hydrogen storage of roughly 22%, 25% and 22% are obtained for MmNi4.6Al0.4, Hydralloy C5 and TiCr1.6Mn0.2, respectively. The MH material influences how effectively cooling works for hydrogen storage. The present results can be utilized for optimization and development of alternative thermal management methods for hydrogen storage in MH bed.