Modeling the impact of temperature-dependent thermal conductivity on hydrogen desorption from magnesium hydride

Hydrogen desorption from metal hydrides, especially magnesium hydrides, presents a major challenge in hydrogen storage applications due to their low thermal conductivity and high hydrogen release temperature. Efficient hydrogen release is crucial for operation, as thermal conductivity is key in heat transfer and desorption kinetics. Previous studies have largely assumed a constant thermal conductivity, but considering its temperature dependence is essential for accurate modeling and optimization of the process. In this study, a numerical evaluation of temperature-dependent thermal conductivity in hydrogen desorption from magnesium hydride was conducted using COMSOL Multiphysics and the finite element method (FEM). Two distinct methods, thermochemical storage systems (TCSS) and radial heat flux were investigated under slow and fast hydrogen release conditions. The results show that accounting for temperature-dependent thermal conductivity significantly reduces desorption time, shortening it by approximately 9 min in slow desorption processes and 0.6 min in fast desorption compared to constant thermal conductivity models. Furthermore, the temperature-dependent model enhanced heat distribution, leading to a lower equilibrium pressure of 1.96 MPa (MPa) compared to 2.09 MPa in constant models, and accelerated hydrogen release, as demonstrated by an increase in Darcy's velocity. The findings suggest that incorporating temperature-dependent thermal conductivity in hydrogen storage models is essential for improving heat transfer efficiency, optimizing desorption kinetics, and enhancing overall system performance. These insights will aid in the development of hydrogen storage in metal hydrides and contribute to more accurate predictions of hydrogen storage system performance.