Regulating Melting Process in the Energy Storage of Solid-Liquid PCM based on Double MRT-LBM Simulation

The melting process of solid-liquid phase change materials (PCM) has a significant impact on their energy storage performance. To more effectively apply solid-liquid PCM for energy storage, it is crucial to study the regulation of melting process of solid-liquid PCM, which is numerically investigated based on double multiple relaxation time lattice Boltzmann method (MRT-LBM) in this work. In this work we pay more attention to the effects of different Stefan numbers (Ste) and Rayleigh numbers (Ra) on the melting process. The results indicate that the PCM melting is greatly influenced by the Ste number and Ra number, which can be divided into the heat conduction dominant stage and the convection dominant stage, according to the onset time of convection Fo_C. In order to describe the contribution of the heat conduction dominant stage to the whole melting process quantitatively, we firstly propose the ratio of the heat conduction dominant stage R_pc, which can be defined as the ratio of Fo_C to the complete melting time Fo_M. R_pc gradually decreases as the Ra number increases, and when the Ste number rises: R_pc=90.0% when Ste=1.0 and Ra=1×10⁵, R_pc=39.6% when Ste=0.1 and Ra=1×10⁵, and R_pc=14.0% when Ste=1.0 and Ra=1×10⁷. A regime map about the effects of different Ste numbers and Ra numbers on R_pc has been further summarized. The discovered findings would be helpful in regulating melting process in the energy storage of solid-liquid PCM.