Improvement in hydrogen desorption performances of magnesium based metal hydride reactor by incorporating helical coil heat exchanger

Mg-based metal hydride has been viewed as one of the most promising materials for hydrogen storage. However, large amount of reaction heat during the hydrogen absorption/desorption cycles negatively affects the heat and mass transfer, thus leading to poor performances. In this work, helical coil heat exchanger (HCHE) is proposed to be inserted into Mg-based metal hydride reactor for improving the heat and mass transfer. The models on pressure-composition-temperature properties and hydrogen desorption kinetics of Mg-based reactor are firstly established for the simulation through experiments. The comparison of hydrogen desorption performances for the reactors incorporating the conventional straight tube, finned tube and new helical coil heat exchangers is conducted based on numerical simulation. The comparison results show that the HCHE has the best effects on improving the heat and mass transfer characteristics of reactor among the three heat exchangers, due to its secondary circulation. Besides, it is suggested that the influence of hydrogen pressure gradient should be considered for the prediction of the performance of Mg-based metal hydride reactor with HCHE. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.