Investigation of thermophysical properties of MWCNT-MgO (1:1)/10W40 hybrid nanofluid by focusing on the rheological behavior: Sensitivity analysis and price-performance investigation

The present study investigates the addition of MWCNT-MgO (1:1) nanoparticles (NPs) to 10 W40 oil to improve the viscosity. There are two parts of laboratory and modeling in this study. In the laboratory part, hybrid nanofluid (HNF) with solid volume fractions (SVFs) of 0.05, 0.1, 0.25, 0.5, 0.75 and 1% and different temperatures of T = 5 , 15 , 25 , 35 , 45 and 55 °C and different shear rates (SRs) are prepared. Power-law index and shear stress changes show that HNFs have non-Newtonian behavior of the shear-thinning type. Increasing the temperature from T = 5-55 °C shows that the viscosity of HNFs decreases significantly by 82%. In general, the addition of NPs increases the viscosity, but at low SVFs, such as 0.05%, the addition of NPs reduces the viscosity of HNF. The proposed modeling for viscosity and relative viscosity have correlation coefficients of 0.9963 and 0.9585, respectively. Deviation from the standard is also in the range of (−10%,+12%). MWCNT-MgO/10 W40 HNF had better economic performance compared to MWCNT-ZnO/10 W40 and MWCNT-TiO2 /10 W40 HNFs in SVF = 0.05%. In SVF = 1%, the greatest increase in sensitivity occurs.