Melting evolution of phase change material in square cavity by lattice Boltzmann method

Abstract

Most numerical simulations for solid–liquid phase change problems are based on the melting point of phase change materials (PCMs) as the initial condition, while research with an initial temperature below the melting point is relatively scarce. In this paper, an enthalpy-based thermal lattice Boltzmann method is employed to investigate the solid–liquid melting process in a square cavity, and various factors including ambient temperature (θa= 0.0, 0.1, and 0.2), saturation temperature (θs = 0.0–0.9), Rayleigh number (Ra = 103, 104, and 105), Stefan number (Ste= 0.025, 0.05, and 0.1), and Prandtl number (Pr= 0.025, 0.05, and 0.1) of the PCMs are systematically examined for their effects on the phase change process at saturated and unsaturated conditions. The simulation results indicate that, first, increasing the ambient temperature or decreasing the saturation temperature results in an accelerated melting rate. Moreover, when the system approaches the saturated condition, achieving complete melting becomes easier. Second, an increase in the Rayleigh number has a dual effect: it enhances convective heat transfer and simultaneously accelerates the melting rate. This effect is particularly pronounced under saturated conditions. Similarly, the Stefan number plays a crucial role in promoting the melting rate, although its impact on convective intensity is minimal. Finally, increasing the Prandtl number not only intensifies convective heat transfer and accelerates the melting rate but also reduces convective disturbances.