Numerical research on the thermal characteristics and mechanical properties of a molten-salt single tank storage system

Abstract

Single-tank thermal storage systems are an effective solution for enhancing the stability and continuity of solar power plants. The thermal characteristics and safety of the cycling process are essential indicators of single-tank performance. In this study, an integrated model of the finite volume method (FVM) and finite element method (FEM) is established for a molten-salt single tank system with a composite wall, and the effects of operating parameters and structural parameters on the cyclic dynamic thermal and mechanical characteristics are investigated. Our findings indicate that increasing the inlet flow rate reduces the heat storage capacity and increases thermal efficiency, while increasing the equivalent stress on the tank wall. However, increasing the inlet/outlet temperature difference enhances the thermal efficiency and the wall equivalent stress and reduces the heat storage capacity. Additionally, a reduction in the solid particle diameters improves the dynamic thermal properties of a single tank, and the thermal efficiency increases from 92.1 % to 94.1 % when the particle diameter decreases from 0.05 m to 0.01 m. In a composite wall structure, increasing the firebrick thickness improves the thermal efficiency and mechanical properties of the tank, while increasing the steel shell thickness improves the stress concentration on the tank wall. Therefore, to improve the thermal efficiency of a single tank and guarantee its security, the inlet flow rate and inlet/outlet temperature differences should be controlled within a certain range. Furthermore, the diameters of solid particles should be reduced, the thickness of the firebrick should be increased and the thickness of the steel shell layer should be controlled within a certain range.