Viscosity and rheological properties of antifreeze based nanofluid containing hybrid nano-powders of MWCNTs and TiO2 under different temperature conditions

In the present study, rheological behavior of MWCNTs-TiO2(20%-80%)/Water-EG(70%-30%) nanofluid has been experimentally investigated. Nanofluid samples were stable and homogeneous with volume fractions of 0.05%, 0.45% and 0.85% using physical methods. Viscosity measurements have been done by employing DV3T-Brockfield viscometer. According to the results, the nanofluid studied in volume fractions of 0%, 0.05% and 0.45% and at temperatures of 10, 30 and 50 degrees C has a behavior close to the Newtonian fluids. The experimental results showed that the nanofluid viscosity in solid volume fraction of 0.85% and the temperature of 10 degrees C increased by 83%. In this study, the highest sensitivity (6.5%) was founded at solid volume fraction of 0.85%. As a result, in low solid volume fractions, adding 10% excess nanoparticles has no effect on the viscosity of the nanofluid, which this issue can be take into account as an important achievement in the industrial and engineering applications. Also results showed that the shear rate versus shear stress is linear in concentration of 0.5% and 0.45%, which indicates the Newtonian behavior of the fluid. But in volume fraction of 0.85% the graph behavior is nonlinear, which indicates the non-Newtonian behavior of the nanofluid. A new experimental correlation is also proposed to predict the viscosity of the nanofluid in accordance with the experimental results. The R-2 for the stated correlation is 0.9913, which indicates the accuracy of the experimental correlation provided to predict the viscosity of the nanofluid in the temperature and concentration range. (C) 2018 Published by Elsevier B.V.