Can MWCNT (20%)-MgO (80%)/10W40 nano-lubricant be used in industries? (Statistical analysis by focusing on economic factors and rheological behavior for best lubrication conditions)

Hybrid nanofluid (NF) is a new generation of NF that create different and sometimes desirable properties due to the combination of two or more nanoparticles (NPs). Also, they have higher physical properties than conventional NFs in terms of thermal conductivity (TC) and viscosity. In this study, the rheological behavior of MWCNT-MgO (20:80)/10 W40 hybrid NF using 174 experimental data in temperature conditions T = 5–55 °C, solid volume fractions SVF = 0.05–1% and the shear rate SR = 666.5–11997 s−1 was investigated. The results of the experiments show that increasing the temperature reduces the viscosity of the BF. It is observed that temperature changes have the greatest effect on the viscosity of NFs. To predict the viscosity of hybrid NF, an empirical relationship based on temperature, SVF, and SR parameters is proposed. Comparing the price-performance ratio of different hybrid NFs concerning price performance factor (PPF), the results of this comparison show that the relative viscosity may be higher than other NFs, but its PPF is lower. To fit the curve of this relationship, the step-by-step regression method with a determination coefficient of 0.9973 is used. The experimental data have an acceptable agreement with the predicted data.