NUMERICAL AND EXPERIMENTAL ASSESSMENT OF A THERMAL MANAGEMENT SYSTEM FOR METAL HYDRIDE HYDROGEN TANK

One of the most promising ways to store and reuse hydrogen is the usage of metal hydride tanks. During the charging process, i.e., absorption, heat is generated inside the hydride tank due to the exothermic nature of the absorption reaction. In contrast, the discharging process is endothermic, and heat should be supplied to the hydride tank. Thermal management is critical in metal hydride tanks (MHT), as overheating the tank during charging or supercooling during discharge significantly reduces the reaction rate and limits the amount of hydrogen stored/released to/from the tank. This study aims to design a water jacket for the thermal management of a metal hydride tank. For this purpose, preliminary parametric flow analyses were conducted for a 3D water jacket design to determine the suitable geometrical configurations that provide uniform convective currents around the tank with lower pressure drops. LaNi5 tank material is then implemented into the model, and the charging process was examined by varying the major hydrogen supply pressure from 10 to 25 bar. The model is developed in ANSYS-FLUENT software. A dedicated UDF code is implemented into the software to incorporate the reaction kinetics equation, the hydride's mass balance, and the hydride's energy source term. The validity of the developed procedure is assured by reproducing a recent numerical work from the literature, and comparative results showed a satisfactory agreement. The parametric analyses showed that increasing the hydrogen supply pressure from 10 to 25 bar reduces the charging time from 12 minutes to 6 minutes. In addition to the numerical survey, experiments are conducted for an HYDROSTIK metal hydride tank in water and air ambients. Based on the numerical simulations, a novel 4-port cooling jacket was produced with a 3D printer and the experiments were conducted under various hydrogen supply pressure. Results showed that in comparison to the reference condition inside stagnant air ambient, the implementation of a water jacket reduces the charging time from 6 hours to 30 minutes