Solar salt system, mainly composed by 60 wt.% NaNO 3 and 40 wt.% KNO 3 , is the most optimized molten nitrates used for thermal energy storage. This paper aims to investigate the influence of the amount of impurity SO 4 2À on thermal performance of solar salt, including thermodynamic parameters like melting point, liquidus temperature, thermal decomposition temperature, thermal stability, and thermophysical properties such as density, viscosity at different temperature. The melting point and thermal decomposition temperature of the mixtures were measured by Differential Scanning Calorimeter (DSC) and Thermo-gravimetric (TG), respectively. The liquidus temperature was obtained by a cooling curve, and the density was determined with a homemade device based on the Archimedes principle. Additionally, viscosity measurements were obtained using a Dynamic Mechanical Analyzer. It was found that: SO 4 2À makes no negative influence on melting point, liquidus temperature and density. The results of viscosity show that controlling the SO 4 2À level within 0.1 wt.% in nitrates is necessary. For the thermal stability at 565°C, SO 4 2À increases the mass loss of nitrates a little more than pure nitrates, as well as easily forms insoluble compounds with cations, especially Na + . Meanwhile, the mass loss mechanisms was confirmed in especial by the vaporization of the nitrates, followed by the release of O 2 . In conclusion, it is critical to maintain SO 4 2À content below 0.01 wt.% for addressing flow problems and reducing instability at high temperature.

Stir casting process is the most important method in the aluminum matrix composites synthesis industry. In the stir casting process, the stability of the liquid aluminum surface and the highest shear force induced by the impellers are the two main factors for high quality of aluminum matrix composites synthesis. In this paper, a three‐dimensional CFD model validated on a water and air two‐phase flow system in a cold model was used to optimize the mixing string tank for aluminum matrix composites synthesis, coupling the volume of fluid (VOF) model, the k‐ϵ turbulence model, and the multiple reference frames (MRF) model. Important mixing parameters of the gas‐liquid two‐phase stirred tank such as rotation speed, type of baffles, and angle of rotating impellers were simulated and analyzed in detail. Varieties of speed were investigated to choose the best one. The best stirrer was chosen through analyzing the stability of liquid aluminum and shear force induced by impellers. The results showed that the optimal stirring speed was 180 rpm during studying the surface between liquid and gas. The best baffles with the lowest vortex were obtained through simulation, with dimensions of 50 mm × 20 mm × 350 mm. In order to get the lowest vortex between water and air and the strongest shear force, the blades should be installed at 15° with vertical direction.