Analysis on heat and mass transfer characteristics of metal hydride reactors during adsorption

The two-dimensional multi-physics model of a cylindrical metal hydride reactor during adsorption was presented to study heat and mass transfer characteristics of metal hydride reactors. In this model, the effects of velocity and temperature changes of heat transfer fluid on the hydrogen adsorption process were considered. The model was numerically solved using the COMSOL Multiphysics V3.5a, and the effects of some important parameters on the reactor performance were discussed. The results show that the hydrogen adsorption reaction is faster near the heat exchanger tube wall where the bed temperature is lower. Moreover, the reacted fraction of the bed near the heat transfer fluid inlet is higher than that near the outlet. Both reducing the thermal contact resistance between the hydride bed and the heat exchanger tube wall and increasing the effective thermal conductivity of the hydride bed can improve the heat transfer performance and accelerate the adsorption process. When the thermal contact resistance decreases from 0.002 m ²·K/W to 0.0005 m ²·K/W, the hydriding time drops by about 15.5%. For metal hydride reactors, adopting heat transfer enhancement measures can reduce the hydriding time and increase the average power.