Study of particle solidification growth evolution during slush hydrogen freeze-thaw process based on Phase Field-Lattice Boltzmann method

Abstract

The remarkable performance exhibited by slush hydrogen makes it a promising choice for cryogenic propellants. The freeze–thaw method is the most commonly used method producing slush hydrogen due to its simplicity and reliability. However, the mechanism of preparing slush hydrogen by freeze–thaw method is not clear. Therefore, in order to figure out mesoscopic evolution law of hydrogen particles, this paper develops a two-dimensional(2D) Phase Field-Lattice Boltzmann Method (PF-LBM) to investigate the evolutionary mechanization of solidification growth of slush hydrogen particles during freezing and thawing in a stagnant flow field. The model is validated using the Lipton–Glicksman–Kurz (LGK) theoretical model for tip velocity, showing strong agreement with the predictions. The dendrite grows symmetrically during the freezing process. As the initial subcooling degree increases, the driving force of dendrite growth also rises, the size of the dendrite crystal increases and the speed of dendrite tip growth accelerates. During the melting process, the size of the dendrite decreases with time. This mesoscopic numerical study reveals the aging mechanisms of hydrogen dendrite. The heat flux leads to an increase in temperature, which affects the morphology of the solid–liquid interface. Additionally, the shape of the dendrite evolves from hexagonal to circular under the effect of heat diffusion, with the overall development tending towards the minimum of interfacial energy. This study explores the growth and aging mechanisms of slush hydrogen particles, which can provide theoretical guidance for the preparation of high-quality slush hydrogen.