Electrical conductivity, viscosity, and density of different nanofluids: An experimental study

• In this study, the thermophysical properties of six different water base nanofluids were investigated.
• The results showed a considerable enhancement in electrical conductivity and viscosity of the base fluid with the addition of nanoparticles.
• The experimental density of the nanofluid can also be predicted accurately by the mixture law.
• With the surfactant addition to water, the electrical conductivity was increased significantly while nanofluid density and viscosity are mostly constant.

In this study, the thermophysical properties of water based nanofluids were investigated. Electrical conductivity, density and viscosity are the main important parameters which must be investigated before performance analysis for industrial application. The amount of these thermophysical properties considerably depends on the types of the nanofluids. The results showed a considerable enhancement in electrical conductivity and viscosity of the base fluid with the addition of nanoparticles. For all nanofluids except Multiwall Carbon Nanotube (MWCNT), the linear trends were observed between electrical conductivity and concentration. Sodium dodecyl sulfate (SDS) was applied as the surfactant and with the surfactant addition to water, the electrical conductivity was increased significantly while nanofluid density and viscosity are mostly constant. Based on the experimental results obtained, the Maxwell model cannot predict the enhancement in the electrical conductivity, thus correlations were developed for this condition. Viscosity of the nanofluid agreed well with the Einstein equation in low concentrations while as the concentration increased, this equation under predicted the experimental viscosity which may be attributed to the changes in behavior of the nanofluid. The experimental density of the nanofluid can also be predicted accurately by the mixture law.