Heat and mass transfer during the storage of hydrogen in LaNi5-based metal hydride: 2D simulation results for a large scale, multi-pipes fixed-bed reactor

Abstract

In the current work, a two-dimensional mathematical model was developed to study the hydrogen absorption reaction and resulted heat and mass transport phenomena inside a large scale metal hydride storage reactor, i.e. of a multi-pipes fixed-bed form. The model was firstly validated through comparison with previous literature experimental data. An excellent fit of the experimental data has been obtained by our model. The sensitively of the bed-temperature and the metal hydrogenation degree to the variation of the thermal conductivity of the metal (λ), hydrogen pressure supply (P), reaction rate constant (Ca) and activation energy (Ea) has been shown. In all cases, the bed temperature increased suddenly up to maxima (after ∼100 s of filling) and then decreased exponentially up to attaining the ambient temperature. Simultaneously, the absorbed concentration of hydrogen showed an initial quick increase at the first 50 s and then the profile continuous linearly with much lower slope up to reaching complete hydrogenation of the metal. Increasing λ has not impacted the hydrogenation rate and the charging bed-temperature, but it accelerated the convective cooling of the bed reactor. Operating at higher hydrogen pressure supply has increased the hydrogenation rate as well as the bed temperature.