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.

In this study, the effect off adding SiO2 nanoparticles on the viscosity of base fluid is investigated experimentally. Base fluids are chosen among common heat transfer fluids such as ethylene glycol, transformer oil and water. In addition different volume percentages of ethylene glycol in water are used as ethylene glycol-water solution. In every base fluid different volume fractions of SiO2 nanoparticles is added. It is shown that the viscosity of solution enhance by adding nanoparticles. The effect of cooling and heating process on the viscosity of nanofluid is also discussed. The presented data show that as the temperature increases the viscosity of base fluid and nanofluid decrease. It is also revealed that there are very little differences between the viscosity of nanofluid in a specific temperature at cooling and heating cycles. According to the experimental results new correlations for predicting the viscosity of nanofluids is presented. These correlations relate the viscosity of nanofluid to the particle volume fraction and temperature.

A nanofluid is a dilute liquid suspension of particles with at least one critical dimension smaller than ~100 nm. Researches so far suggest that nanofluids offer excellent heat transfer enhancement over conventional base fluids. The enhancement depends on several factors such as particle shape, particle size distribution, volume fraction of nanoparticles, temperature, pH, and thermal conductivities of nanoparticles and base fluids.This paper presents an updated review on nanofluids with the emphasis on heat transfer enhancement including formulation, physical properties, biological and non-biological applications, stability, possible mechanisms for the enhancement of heat conduction, and numerical modelling of nanofluids. Based on the research findings, a number of challenges are emphasized in order to understand the underlying physics for future industrial take-up of the nanofluids technology. Further computational studies are also required in order to understand all of the factors affecting on the enhancement of thermal conductivity of nanaofluids.