GRAVITY EFFECT ON NATURAL CONVECTION MELTING INVESTIGATED WITH 2D AND 3D LATTICE BOLTZMANN METHODS
Solid-liquid phase change latent thermal energy storage system has been recommended to complicated aerospace systems for thermal control due to the prominent energy storage efficiency and constant phase change temperature. To explore the gravity effects on natural convection melting, two dimensional and three dimensional lattice Boltzmann model are established to solve the phase change heat transfer. Firstly, the average Nusselt number and total liquid fraction are examined under different gravity conditions. It is found that the increasing gravitational acceleration plays a positive effect on the natural convection effect, and results in the pronounced increment of melting rate. In addition, a three dimensional simulation of natural convection melting is performed, and the evolution of its temperature distribution shows similar trends with the two dimensional model. Moreover, the three dimensional effects during natural convection melting are discussed by the comparison of total liquid fraction with two dimensional lattice Boltzmann model. Numerical results show that a considerable difference exists in the two dimensional and three dimensional lattice Boltzmann models. It might be caused by the depressed natural convection in three dimensional lattice Boltzmann models where there are walls along z direction.