Experimental investigation of effective parameters on MWCNT–TiO2/SAE50 hybrid nanofluid viscosity

In the present study, rheological behavior of multi-walled carbon nanotube (MWCNT) (30%)–TiO 2 (70%)/SAE50 hybrid nanofluid is investigated. Samples of nanofluid with nanoparticle concentrations of 0% up to 1% were prepared, and their dynamic viscosity was measured at temperatures between 25 and 50 °C and various shear rates using Brookfield viscometer. The relation between shear stress and shear rate of MWCNT–TiO 2 /SAE50 nanofluid showed its non-Newtonian behavior at all concentrations. In order to predict the viscosity, a comparison was done between the efficiency of different proposed empirical correlations in this prediction. Three empirical correlations were proposed, and two different independent variables were considered for each one. In all three cases, conformity of obtained results for viscosity was compared with experimentally obtained viscosities. Results revealed much better accuracy of proposed empirical correlations containing temperature as an independent variable compared with the other correlations not containing independent variable of temperature. Accuracy and efficiency of predicting correlations for relative viscosity was compared with efficiency of absolute viscosity prediction correlations and results indicated relatively equal accuracy of results and prediction values. Furthermore, viscosity changes of MWCNT (30%)–TiO 2 (70%)/SAE50 nanofluid were compared with other studies in order to prove its better performance.