Study of the effects of particle shape and base fluid type on density of nanofluids using ternary mixture formula: A molecular dynamics simulation

Ternary mixture formula with consideration of the effect of nanolayer formation is capable of predicting nanofluid density more accurately compared with the traditional mixture rule. The aim of this investigation is to study the effect of particle shape and type of base fluid on density of nanofluid based on the ternary mixture formula using molecular dynamics simulations. In this regard, two types of base fluids, i.e. water and liquid argon, as well as four different particle shapes, i.e. spherical, planar, block and rod-shaped with different aspect ratios are examined. The results showed that different particle shapes show different behaviors in attracting base fluid molecules and forming nanolayer. The thickness of nanolayer is assumed from the surface of nanoparticle to the place that the density fluctuations stay within a tolerance of 2% of the base fluid density. Accordingly, the thicknesses of nanolayers are 0.9 nm and 1.3 nm for silver-water and silver-liquid argon nanofluids, respectively. Moreover, it was found that the density of nanofluids containing planar nanoparticles as well as spherical nanoparticles decreases with increasing nanoparticle diameter and planar nanoparticle has the highest density of nanolayer among planar, spherical and rod-shaped particles. The comparison between the densities of three nanofluids containing equal volume nanoparticles with different shapes reveals that the ternary mixture formula has significant advantages over the traditional binary mixture. (C) 2020 Elsevier B.V. All rights reserved.