Abstract:

The Lattice Boltzmann method is used to simulate the natural convective melting in a triangular cavity. The effects of the Rayleigh number Ra, local heat source size L, and location S on its phase change heat transfer and energy storage characteristics are analyzed. The numerical results show that the full melting time in the triangular cavity with a full thermal boundary initially increases then decreases with the increase of the convective strength. The inflection point is at 31000. The melting process and the convective effect show a positive correlation when Ra > 31000. In contrast, a negative correlation is observed when Ra < 31000. Moreover, when the local heating size L is small, the melting time of the middle heat source is the shortest, and the energy storage efficiency is the highest. The melting time of the uppermost heat source is the longest. In addition, due to the different influence of the cold inclined the total melting time of the upper heat source increases with the convective effect enhancement wall. By contrast, the total melting time of the lower heat source shortens, while that of the intermediate heat source first increases then decreases with a critical value of Ra=19000. Meanwhile, when L≥0.5, the lowest heating becomes the best melting position, and the energy storage time is the shortest. As the convective intensity increases, the total melting time of the upper, middle, and lower local heating schemes first increases and then decreases, and the critical Ra values increase with the heating length increase. Furthermore, the change of the heating size in different positions has different effects on the energy storage process. This work will be helpful in providing theoretical basis and technical guidance for the optimal design and efficient energy storage of the actual phase change heat exchange equipment.

Key words: Lattice Boltzmann method, phase change energy storage, natural convection melting process, triangular cavity