关键词: 熔盐, 相变, 多孔介质, 自然对流, 传热

Abstract:

The phase change heat storage technology shows many advantages, such as large energy storage density, low cost and etc. However, the property of low thermal conductivity of the phase change material limits its wide application. As a new heat transfer enhancement material, foam metal has relatively higher thermal conductivity and higher specific area. The molten salt heat storage experiment was carried out and the physical model of phase change thermal storage was constructed. A two-dimensional axisymmetric, transient solid-liquid phase transition mathematical model of the thermal storage vessel was established. The phase transition process was simulated using the solidification & melting model, and the phase transition region was based on the Boussinesq approximation. Numerical simulation results of thermal storage conditions of pure nitrate and thermal storage conditions after adding foam metal were compared. The heat transfer enhancement effect with the application of foam metal in the molten salt thermal storage process was analyzed by experiments and numerical simulation. Results showed that foam metal can effectively improve the heat transfer rate of the molten salt. Foam metal with relatively smaller porosity or higher thermal conductivity can generate a better enhanced heat storage effect. In the later stage of the heat storage process, natural convection heat transfer was the main heat transfer mode and foam metal severely inhibited natural convection. Comparing different filling positions of the foam metal, it was found from this paper that the filling position was closer to the center of the container, natural convection was weakened and the corresponding heat storage performance was worse.

Key words: molten salt, phase change, porous media, natural convection, heat transfer