Numerical simulation of a metal hydride tank with LaNi4.25Al0.75 using a novel kinetic model at constant flows

Abstract

Tritium as the fuel of fusion reactor must be stored in a metal hydride (MH) tank at a desired absorbing rate. This requirement must be fulfilled by proper design of the MH tank, which can be assisted by numerical simulation. In this work, a numerical model is proposed to couple hydrogen absorption kinetics and the heat and mass transfer of the MH tank. A novel kinetic model at constant flows for the gas-solid reaction is developed to analyze the complex hydrogen absorption kinetics of a MH at different pressures, which is the core of the numerical model. Kinetic analysis is performed to obtain the hydrogen absorption rate equation of LaNi4.25Al0.75, which has two stages upon the increase of pressure. The numerical model, after being well verified by our experimental data, is used to predict the hydrogen absorption performance of a double-layered annulus MH tank filled by LaNi4.25Al0.75. The predicted results indicate that a thinner LaNi4.25Al0.75 layer and higher heat transfer fluid (HTF) velocity can improve the heat transfer of the MH tank effectively, thereby enhancing the hydrogen absorption performance. When the layer thickness and HTF velocity is 3 mm and 25 m s−1, the double-layered annulus MH tank can meet the target of absorbing 5 mol of hydrogen for 60 min at 1.87 NL min−1. This designed MH tank with LaNi4.25Al0.75 can provide a reference for tritium storage in fusion reactors.