Molecular Dynamics Simulation Of Thermophysical Properties Of Alkali Metal Chloride Molten Salt-Based Nanofluids

The utilization of energy plays a key role in the development of human society.The power generation process not only consumes traditional energy but also pollutes the environment.Therefore,the research on renewable energy power generation technology is particularly important.Among the renewable energy power generation technologies,concentrated solar power technology（CSP）has received special attention,in which molten salt is an important heat transfer and heat storage medium in the CSP system.The specific heat capacity determines how much heat a given amount of thermal energy storage material（TES）can store.To increase the specific heat capacity of molten salts,nanomaterials are often doped into molten salts.In this paper,alkali metal chloride molten salts and nanofluids doped with Si O₂nanoparticles are taken as research objects,and their thermal properties and internal mechanisms are analyzed by molecular dynamics（MD）simulation.The main work and research contents of this paper are as follows:（1）The Buckingham potential was derived from the Born-Mayer-Huggins（BMH）potential parameter to express the interaction within the alkali metal chloride molten salt,and compared with the BMH potential.（2）The accuracy of Buckingham potential for calculating the structural parameters and thermophysical properties of alkali metal chloride molten salts is verified.The RDF,coordination number,density,specific heat capacity,viscosity,self-diffusion coefficient and MSD of elemental molten salts（KCl,Na Cl,Li Cl）were simulated respectively.The results show that the Buckingham potential parameter has high accuracy in calculating the structural parameters and thermophysical properties of the three chloride molten salts.Among them,the errors of the simulated values of density,specific heat capacity,and self-diffusion coefficient compared with the experimental values are 9.0%,3.8%,and 6.11%,respectively.The average errors of viscosity of KCl,Na Cl,and Li Cl molten salt are 6.21%,0.92%,and 4.53%,respectively.And Buckingham potential had better accuracy in calculating specific heat capacity,viscosity and self-diffusion coefficient,and the simulation results of thermophysical properties of Na Cl and Li Cl are closer to the experimental values than BMH potential.（3）Molecular dynamics simulation of the specific heat capacity of molten salt-based nanofluids formed by adding a small amount of Si O₂ nanoparticles.The results show that the specific heat capacity of the three nanofluids increases first and then decreases with the increase of the Si O₂ doping ratio,and reaches the maximum value at 1wt%.（4）The radial distribution function,energy,coordination number,relative number density and local relative number density of the nanofluidic system were calculated.The findings suggest that the increase in specific heat capacity of molten salt-based nanofluids can be explained by energy changes and the formation of"compression layers".And found the anion and cation layering phenomenon in the compressed layer around the surface of Si O₂ nanoparticle;the relative number density and local relative number density analysis can better explain this phenomenon.The results and findings of this work allow for a more efficient design of molten salt nanocomposites,providing an important foundation for future research in thermal energy storage.