On the evaluation of the dynamic viscosity of non-Newtonian oil based nanofluids Experimental investigation, predicting, and data assessment

The present study has evaluated the rheological behavior of an oil-based (5W50) hybrid nanofluid [magnesium oxide (65%)-multi-walled carbon nanotubes (35%)]. MgO nanoparticles with a diameter of 50 nm and multi-walled carbon nanotube nanoparticles with a diameter of 3-5 nm were selected as dispersed particles in the oil base fluid. Viscosity of nanofliud was examined at the temperature range of 5-55 degrees C (6 cases) and concentration of 0.05-1% (6 cases). The effect of these two parameters (temperature and volume fraction) on the viscosity was studied. The results of the curve fitting on the experimental results and achieving the proper coefficient of determination (R-2) showed non-Newtonian behavior of nanofluid in all volume fractions. The impact of shear rate changes in the range of 665.5-11,997 s(-1) on the viscosity was studied. A new experimental correlation was proposed in order to predict the viscosity at different temperatures, volume fractions, and shear rates. The R-squared value was 0.999, which shows the precision of the proposed correlation.