The effect of initial pressure and atomic concentration of iron nanoparticles on thermal behavior of sodium sulfate/magnesium chloride hexahydrate nanostructure by molecular dynamics simulation

Abstract

Thermal energy storage (TES) is one of the uses of phase change material (PCM). The primary factor contributing to this capability is the elevated latent heat of melting present in these materials. The current study investigates the effect of initial pressure (IP) (ranging from 1 to 5 bar), and atomic ratio (AR) of Iron nanoparticles (NPs) (Fe = 1, 2, 3, and 5 %) on the thermal behavior (TB) and phase transition process of sodium sulfate/Magnesium chloride hexahydrate (Na 2 SO 4 /MgCl 2 & sdot; 6H 2 O) nanostructures as PCMs using molecular dynamics (MD) simulation. The simulated PCM was positioned inside a spherical atomic channel composed of iron. The TB of simulated nanostructures was examined by reporting changes in viscosity (Vis), thermal conductivity (TC), and phase transition time (PTT). The results reveal that by increasing IP from 1 to 5 bar, the PTT reaches from 3.50 to 3.61 ns, and the TC decreases from 1.03 to 0.94 W/m.K. The results show that adding 3 % of Fe NPs was the optimal ratio to improve the TB of the Na 2 SO 4 /MgCl 2 & sdot; 6H 2 O-Fe NP. By raising the ratio of Fe NPs from 1 to 3 %, Vis slightly decreased from 4.31 to 4.22 mPa.s. In comparison, adding more Fe NPs with 5 % ratio raised the Vis to 4.30 mPa.s. According to the results, increasing the IP decreased the distance among the particles. So, the attraction among particles increased, leading to greater adhesion and Vis. By increasing the IP, the distance among atoms decreases, and the space between NPs and atoms in the simulation box decreases. Consequently, NP movement and fluctuations decrease, and collisions decrease. The results of this simulation will be effective in heating - cooling and ventilation systems, automotive industries, textile industries, and so on.