Investigation of nanoparticles shape that influence the thermal conductivity and viscosity in argon-based nanofluids: A molecular dynamics simulation

Abstract

The shape of nanoparticles plays an essential role in the thermophysical properties of nanofluids, yet their mechanisms and characteristics remain lacking in comprehensive studies. Molecular dynamics simulations of non-equilibrium molecular dynamics (NEMD) and reversing perturbation non-equilibrium molecular dynamics (RNEMD) calculation methods were used to study thermal conductivity and viscosity of Cu/Au-Argon based nanofluids, taking into account a variety of influencing factors, as well as nanoparticles shape and volume fraction. Through the analysis of the number density distribution, radial distribution function (RDF) and mean square displacement (MSD), the influences of nanoparticles shape (represented by the surface-to-volume ratio) were described and investigated: the highest value was 0.182 WK−1m−1 containing columnar particles of Au at 2% volume fraction, while the thermal conductivity of Cu nanofluids was 0.162 WK−1m−1 under the same conditions; the average values of viscosity had very close values of 2.82 × 10−4 Pa·s (Cu-Ar) and 2.86 × 10−4 Pa·s (Au-Ar) at 1.5% particle volume fraction for nanofluids containing spherical particles, respectively. Simulations of argon-based nanofluids containing five different shapes of Au nanoparticles indicate that the thermal conductivity improves with the growth of the surface-to-volume ratio. And the enhancement of the interfacial nanolayer density turns out to be the main factor that nanoparticles with higher S/V value facilitated the enhancement of the thermal conductivity of argon-based nanofluids. This study enriches the molecular dynamics studies of nanofluids and provides important insights for understanding the effect of nanoparticle's shape on the thermal properties of nanofluids.