CFD simulation of heat and mass transfer processes in a metal hydride hydrogen storage system, taking into account changes in the bed structure

• Published in: International journal of hydrogen energy
• Main Authors: Minko, Konstantin B., Lototskyy, Mykhaylo V., Bessarabskaya, Irina E., Tarasov, Boris P.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-05-2024
• Subjects: bed structure; heat and mass transfer; hydrogen storage; metal hydride; modelling; metal hydride; bed structure; heat and mass transfer; modelling; hydrogen storage
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2024.05.083

CFD modelling of heat-and-mass transfer in metal hydride (MH) beds is an important step in the development and optimisation of MH reactors for hydrogen storage, compression and separation / purification. In the existing models, the mass conservation equation includes the density of solid in the non-hydrogenated (ρs) and hydrogen-saturated (ρss) states. To provide constant porosity of the MH bed during H2 absorption / desorption, assumption ρs<ρss is typically taken. However, this assumption contradicts to well-known fact that hydrogenation of hydride-forming alloys is accompanied by the expansion of crystal lattice of the metallic matrix and, therefore, by the decrease of the solid density by 15–25%.
This work presents results of the modelling which takes this effect into account. The model assumes that the density of the MH changes linearly as the starting hydride-forming alloy is saturated with hydrogen, while the volume of the MH bed remains constant. The last assumption is a limiting estimation because it provides the maximum possible reduction in the porosity during H2 absorption process.
The model was validated using published experimental data on a cylindrical MH reactor filled with 422 g of LaNi5. It was shown that accounting the realistic changes in the MH density can significantly affect the simulation results.
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•Simulation of heat and mass transfer in MH bed accounting the real changes of MH density•It is well-known that the MH density decreases upon hydrogen saturation•As a result, the bed porosity decreases and its effective thermal conductivity increases•The above changes significantly affect the simulation results•The work considers the limiting case when the volume of the MH bed does not change