Evolution of natural convection melting inside cavity heated from different sides using enthalpy based lattice Boltzmann method

Abstract

Melting coupled with natural convection in cavity has always been a hot topic. In this paper, natural convection melting in cavity heated from different sides are numerically simulated using the enthalpy based lattice Boltzmann method. The cavity model of one heated side and three adiabatic sides is employed to achieve totally melting. The dimensionless numbers are: Pr = 0.02, St = 0.01, Ra = 25,000 and Ra = 50,000. Melting when heated from top is conduction melting, melting when heated from right is omitted due to its symmetry with the case when heated from left. The heat transfer and flow characteristics when heated from left and bottom are mainly investigated. Results indicate that, when heated from left and bottom, the melted region always enlarges but the growth of flow velocity is suppressed. In the final stage of melting, the temperature distribution tends to be uniform and the flow inside cavity gradually vanishes. Moreover, the melting efficiency when heated from bottom is significantly decreased by its first stage of conduction melting. As Ra increases, that stage is obviously shortened, the melting efficiency is promoted rapidly. And the melting efficiency when heated from bottom exceeds the efficiency when heated from left at around Ra = 25,000. Besides, melting from different sides are actually the problems of different angles between the heat flux out of the boundary and gravity. The effect of more different angles on the melting efficiency is further discussed. As the angle increases, the average dimensionless velocity also increases. Natural convection inside the cavity becomes stronger, and the melting efficiency gets higher.