Performance investigation of metal hydride reactor equipped with helically coiled heat exchanger during hydrogen absorption and desorption

A three-dimensional model was established for a metal hydride (MH) reactor incorporating a helically coiled heat exchanger (HCHE). Influences of different operation parameters on the MH reactor's performance were explored at different stages of hydrogen absorption and desorption. Simulation results showed that hydrogen absorption or desorption reaction was induced mainly by the hydrogen supply pressure (pin) or outlet pressure (pout) during the initial stage (stage A or C). Beyond the initial stage (stage B or D), hydrogen absorption or desorption process was determined mainly by heat transfer rate. Hydrogen absorption process could be improved by reducing the inlet temperature (Tin) of heat transfer fluid (HTF) and the thermal resistance between the MH and HCHE (Rth) and by elevating pin and flow rate of the HTF (qf). Besides, in the central zone of the reactor, both temperature and reacted fraction were observed to plateau. Finally, sensitivity analysis was performed on the specific heating power of the four parameters during absorption, and the sensitivity sequence from large to small is pin, Tin, Rth and qf.