Two zone model for mushy region of solid-liquid phase change based on Lattice Boltzmann method

摘要

The solid-liquid phase change technology has been widely used in the efficient use and controllable management of heat in engineering. It is important to reveal the transfer mechanism of phase change interface for the optimization of solid-liquid phase change technology. A composite model of heat transfer and fluid flow in mushy zone is established by using the modified enthalpy method based on the combination of porous medium flow and multiphase flow theory. Lattice Boltzmann Method is used to solve the transient model of multi-field coupling in mushy zone in pore scale. The transfer mechanism in solid-liquid phase change, especially at the solid-liquid interface in mushy zone is focused on in this paper. The numerical results show that the thickness of mushy region is directly related to the phase change temperature radius of the mushy region. A smaller phase change temperature radius of the mushy region leads to a thinner mushy region thickness. The results also indicate that the mushy region constant (C) and demarcation point (r(tr)) of high-low liquid fraction area, phase change materials and the structure of mushy region have a close relationship with each other. The dimensionless parameters (Pr, Ra, Ste) of phase change process have an obvious influence on the mushy region and the phase change process.