Molecular dynamics simulation study on thermophysical properties of carbon nanotube-enhanced lithium fluoride as a high-temperature phase change material

Abstract

Lithium fluoride is combined with single-walled carbon nanotubes to enhance its performance as a phase change material for using the latent heat thermal energy storage approach in concentrated solar power systems. Molecular dynamics simulation using Large-scale Atomic/Molecular Massively Parallel Simulator is employed to evaluate thermophysical properties, including density, melting point, enthalpy, specific heat capacity, thermal conductivity, diffusion coefficients, and viscosity, across both solid and liquid phases. The addition of single-walled carbon nanotube increases the density by 3.11–6.35% in the system containing 704 carbon atoms and 5.47–10.26% in the system containing 1024 carbon atoms, while enhancing the thermal conductivity by 2.76–29.42% and 17.06–33.53% in the respective systems, thereby improving volumetric energy storage and heat transfer. A reduction in melting temperature and a minor enhancement in specific heat capacity, up to 2.6% at higher carbon concentration, are also observed. Diffusion coefficients are reduced by up to 33% and viscosity by up to 35% at higher SWCNT concentrations, demonstrating the material’s suitability for stationary thermal energy storage systems. Figure of merit analysis indicates that the composite phase change material with 1024 carbon atoms exhibits the best overall performance. These findings highlight the potential of single-walled carbon nanotube-enhanced lithium fluoride as a composite phase change material for thermal energy storage applications, validating the effectiveness of molecular dynamics simulations for high-temperature composite phase change material optimization in concentrated solar power systems.