Molecular Dynamics Simulation On Thermophysical Properties Of Melted Carbonate Of Energy Storage Materials

In the heat utilization of solar energy,the working medium for storing heat has attracted more and more attention.Among them,phase change materials are widely used in solar thermal power generation systems because of their high latent heat of phase change and low price.As a kind of phase change material,molten salt is widely used as a heat storage medium and heat transfer fluid because of its wide operating temperature range,low vapor pressure,and excellent heat transfer performance^[1-4].The macroscopic thermophysical properties of substances are one of the most basic and important characteristics in engineering applications.The physical parameters of the phase change material will have a great influence on the heat storage and heat release rate of the system.In order to reduce energy storage and release time and improve energy utilization efficiency,it is necessary to choose appropriate methods to study the thermophysical properties of phase change materials.This article combines theory and existing experimental analysis.The method of molecular dynamics simulation is used to study the thermophysical properties of molten carbonate.The temperature dependence of macroscopic properties is discussed from a microscopic point of view.In this study,based on an effective potential function model,combined with the Born-Mayer type of Coulomb term.The molecular models were constructed by taking molten alkali metal carbonates Na₂CO₃,K₂CO₃ and different ratios of Na₂CO₃/K₂CO₃ binary mixed salts as the research objects.Then use molecular dynamics methods to study.Combined with Materials studio,Packmol,Lammps and other software,with its assistance,the various density,thermal conductivity,viscosity,diffusion coefficient and other thermophysical properties of carbonate molten salt under high temperature conditions of 1100-1500K are studied.According to the calculation results,the expressions of Na₂CO₃ and K₂CO₃ with respect to temperature are fitted.The temperature dependence of macroscopic properties is discussed from a microscopic point of view.The results show that as the temperature increases,the molar volume increases,and the ability to resist shear deformation and vibration transfer between ions decreases.From the microscopic point of view,the macroscopic properties of the Na₂CO₃/K₂CO₃ binary mixed salt with different components are affected by the components,and all the simulation results are in good agreement with the existing experimental data.