Numerical analysis on pulverization and self-densification for hydrogen storage performance of a metal hydride tank

Abstract High and steady hydrogen absorption/desorption rates are essential for long-term services in the field of hydrogen energy. However, the absorption/desorption rates will be affected by the changes of heat and mass transfer characteristics caused by pulverization and self-densification phenomena. In this work, a novel simplified numerical model is proposed for describing the effects of pulverization and self-densification on hydrogen storage performance in a Ti0.98Zr0.02V0.43Fe0.09Cr0.05Mn1.5 (HWT5800) metal hydride tank. The model is conducted using the finite element method under different degrees of pulverization and self-densification, from which the results agree well with the experimental data in literatures. The hydrogen absorption rate will be enhanced after pulverization of particles due to the increased reaction rate constant. The hydrogen absorption time at 80% of maximum hydrogen capacity (t80%) can be shortened from 2191.98 to 1797.23 s when particle radius ratio (PR) is 0.2. The hydrogen absorption rate will be reduced after self-densification, which is mainly attributed to the lower thermal diffusivity. t80% can increase from 1851.26 to 2304.54 s after self-densification, when the porosity at the top and bottom of MH bed is 0.7 and 0.3, respectively.