Investigation of gravity effect on phase change heat transfer using the lattice Boltzmann method

Abstract

Phase change material (PCM) has been recommended to complicated aerospace systems due to the excellent ability of storing thermal energy in recent years. To better understand the effect of gravity on the solid-liquid phase change process, in this paper, the temperature and flow fields under different gravity accelerations are investigated with the help of lattice Boltzmann method (LBM). Firstly, it is found that the clockwise circulation, caused by the temperature gradient, leads to the inhomogeneous distribution of liquid-solid interface along vertical direction, and accelerates the motion velocity of liquid-solid interface. Secondly, with the increase of gravity from 0 g to 1 g, natural convection appears to be more and more significant, and the dominant heat transfer mechanism transits from conduction to convection. Finally, the average Nusselt number under 0 g, 0.01 g and 0.1 g are 48.0%, 48.3% and 56.9% respectively of that under 1 g at Fo = 30. It indicates that reduced gravity restrains the natural convection effect, and results in the pronounced reduction of average Nusselt number and melting rate.