Volume 68

Effect of dynamic structural evolution of reaction beds on heat and mass transfer and hydrogen absorption performance in metal hydride reactors Lei Qiao, Shengguan Liu, Tinghao Zhang, Danming Cao, Xiaoshuai Bai, Zeyuan Wang, Zhihua Zhai

Abstract

Sustaining rapid and stable reaction kinetics in metal hydride (MH) reactors during cyclic hydrogen absorption and desorption is essential for practical deployment, yet bed expansion and particle pulverization severely effect the cyclic reaction efficiency. Current mathematical models cannot fully capture their coupled effects, limiting long-term performance prediction and structural optimization of MH reactors. This study presents a novel mathematical model coupling bed expansion and particle pulverization with heat and mass transfer during hydrogen absorption. To reflect realistic bed evolution, the model incorporates dynamic changes in void fraction, particle size, thermal conductivity, permeability, and kinetic constants. Validated against experimental data, the model demonstrates high accuracy. Simulations indicate that bed expansion reduces the hydrogen absorption rate; neglecting this factor leads to a 6.7% overestimation of the average absorption rate. Additionally, a lower particle pulverization ratio (PR) reduces average particle size and accelerates reaction kinetics. Specifically, reaching 90% saturation takes only 1177 s at PR=0.238, representing a 40.6% time reduction relative to PR=0.714.

Keywords Metal hydride reactor, Hydrogen storage, Mathematical model, MH bed expansion, Particle pulverization