An empirical electrical conductivity assessment of Nanofluids comprising CuO nanoparticles water-based in different concentrations, particles size and various temperatures of Nanofluids has been carried out in this paper. These experimentations have been done in deionized water with nanoparticles sizes such as 89, 95, 100 and 112 nm and concentrations of 0.12 g/l, 0.14 g/l, 0.16 g/l and 0.18 g/l so Nanofluids obtain in temperatures such as 25oC, 35oC, 45oC and 50oC for investigation of their electrical conductivity. It is observed that, in water-based Nanofluids, the electrical conductivity increases with increasing in both Nanofluids temperatures and concentration respectively in the range 25-50oC and 0.12-0.18g/l. But in nanoparticles size rising in Nanofluids we observe that electrical conductivity has a few increase when nanoparticles have 95nm diameters, so decrease for biggest nanoparticles such as 100 and 112nm. It seems that there is an optimum in electrical conductivity with resize of nanoparticles.

Understanding the microscopic dispersion and aggregation of nanoparticles in nanoscale media has become an important challenge during the last decades. Molecular dynamics is one of the important techniques to tackle many of the complex problems faced by rheologists and engineers. Making progress in the investigations at nanoscale whether experimentally or computationally has helped understand the physical phenomena at the molecular scale. In addition, important developments have been made in predicting behavior of confined fluids and lubricants at nanoscale. In this review we will discuss on some progress made on the illustration of aggregation mechanisms in Nanofluids. Our main focus will be on the application of molecular modeling in the effect of aggregation on the nano-rheology of Nanofluids.

The influence of temperature, mean nanoparticle size and the nanoparticle concentration on the dynamic viscosities of Nanofluids are investigated in an analytical method followed by introduction of modified equations for calculating the Nanofluids’ viscosities. A new correlation is developed for effective viscosity based on the previous model where the Brownian movement of the nanoparticles is considered as the key mechanism. In previous studies, the proposed models were not appropriate for nanoparticles larger than 36 nm. They were also focused on low concentrations of nanoparticles up to 5%. The possibility of homogeneous dispersion of the nanoparticles and the Stokes law are observed here. This new model is explained in terms of temperature, mean nanoparticle diameter, nanoparticle volume concentration and both the nanoparticle and base fluid thermophysical characteristics for the effective viscosity of Nanofluids. A combined correction factor is introduced to take into account the simplification for a free stream boundary condition outside the boundary layer. A good agreement is observed between the effective viscosity obtained in this new model and those of recorded experiments conducted for different Nanofluids. The results show that the present model is valid for large volume concentration (0% < φ <11%), mean nanoparticle size (13 nm < dp < 95 nm), temperature variations (290 K