Thermal study of sodium nitrate and potassium nitrate for thermal energy storage by molecular dynamic simulations

Dourna Jamshideasli, Jay M. Khodadadi, and Wenwen Ye

1418 Wiggins Hall, Department of Mechanical Engineering, Auburn University, AL 36849-5341, USA

Greater utilization of the concentrated solar power to compete with conventional power generation systems is strongly linked to updated and more accurate thermophysical property data for molten salts. In this study, nonequilibrium Molecular Dynamics (MD) simulations to model thermal transport phenomenon associated with sodium nitrate (NaNO3) and potassium nitrate (KNO3) in both solid and liquid states as high-temperature phase change materials for thermal energy storage systems were performed with the Large-scale Atomic/Molecular Massively Parallel Simulators. The Buckingham potential energy function (commonly referred to as the force field) that described the interaction potential as a function of a set of parameters and comprised both bonded and non-bonded interactions was employed. Particle-particle particle-mesh was used for the Coulombic interactions. The NPT ensemble was utilized. In this work, the time step was 0.5 fs. Moreover, for all thermostats and the barostat, the time constants were 0.05 ps and 0.5 ps, respectively. The crystal structures for melting and solidification and instantaneous movements of the constituents of the system were visualized by VMD. As a future work, a new potential field based on a more accurate basis set can be developed to improve the data. The current code can be extended to simulate the salts with carbon-based nanoadditives, specifically graphene nanoplatelets to realize the effect of alignment factor and the interfacial thermal conductance between the nanofiller and the salt matrix. The relevant MD predictions of the properties can be compared with simultaneous in-house experimental data under development and literature values.