Comprehensive analysis of dispersion and aggregation morphology of nanoparticles on the thermophysical properties of water-based nanofluids using molecular dynamics simulation

Abstract

BackgroundIn recent decades, using nanofluids (NFs) to improve the thermal properties of the NFs was widely considered. MethodsIn the current study, molecular dynamics (MD) simulation was used to examine the effects of dispersion and morphology of nanoparticle aggregation (NA), solid volume fraction (SVF), temperature (Temp), nanoparticle size (NS), and nanoparticle shape on the thermal properties of water/Nickel nanofluid (NF). The thermophysical properties of the NFs were simulated and studied using MD simulation, which was a common computational method because of the high cost and limitations of experimental approaches, particularly at molecular dimensions. LAMMPS software package, and the EAM potential function were used to simulate the structure. In the present simulation, three NF samples containing Ni with SVF of 1, 2, and 3% with two shape of spherical (SN) and cylindrical (CN) and in two different Temp of 313 to 358 K were considered. Also, the nanoparticles (NPs) with the radii of 8, 10, and 12 Å were considered in the simulation box. The results show that by increasing Temp and SVF, the diffusion coefficient (Dnf) of NFs would increase and decrease, respectively. From a numerical point of view, by increasing Temp from 313 K to358 K in 1% SVF, thermal conductivity (knf) and Dnf increased from 0.25656 to 0.99688 W/mK and 0.34786075 to 0.68396948, respectively. Moreover, by increasing SVF and T, the viscosity (µnf) of NF increased and decreased, respectively. Significant findingsAs the radius of NPs increased, the Dnf of the water-based NFs increased. This is because larger NPs can provide more surface area for water molecules to interact with, which can increase the overall mobility of water molecules and enhance the Dnf. Also, the µnf decreased. This is because larger NPs can reduce the overall µnf of the NF by increasing the mobility of water molecules and reducing the degree of hydrogen bonding between water molecules. Besides, NFs containing CN had a lower Dnf than NFs created by SN. On the other hand, suspensions containing CN had a greater µnf and knf.