Micron-scale experimental and numerical study of molten salt solidification process

Abstract

The solid-liquid phase transformation mechanism during solar salt solidification was investigated at the micron-scale via a combination of visualization experiment and numerical simulation with the phase-field method. The solidification process of solar salt particles was divided into three typical stages, with different phase transition patterns and solid-liquid phase boundary morphologies. In addition, the crystallized solar salt featured a typical dendritic morphology, and the initial crystallization site was random and significantly affected dendrite evolution in all directions. When the nucleation site was close to the center, the growths of the main dendrites in the different directions were more consistent, and consequently, the overall morphology featured good symmetry. Through phase-field simulation, the effects of three key phase-field parameters, namely the mode number of anisotropy j , the dimensionless latent heat K , and the strength of anisotropy δ , on the dendrites were explored via the controlled variable method. The model’s vital input parameters were further optimized according to the experimental results. The results showed that the numerical model could accurately simulate the crystal evolution of the actual solar salt particles at K = 2.4, j = 9, and δ = 0.01.