Experimental study and modeling the SiO2-MWCNT (30:70)/SAE40 hybrid nano-lubricant flow based on the response surface method to identify the optimal lubrication conditions

Viscosity of an enriched SAE40 engine oil by nanoparticles (SiO2 and MWCNT) is studied quantitatively and qualitatively based on the effective independent variables of temperature, the volume fraction of nanoparticles (φ), and shear rate (γ̇). It was found that the nano-lubricant flow regime is of pseudo-plastic non-Newtonian type. Statistical analysis shows that at φ = 1%, T = 45 °C and γ=̇ 6665 s−1, the hybrid nano-lubricant experiences the highest increase of 42.53%. Rheological analyzes are shown that the viscosity (μnf) is more affected by temperature than other factors. It was also found that the relationship between the viscosity with temperature, φ and γ̇ are direct, inverse, and direct, respectively. To predict the experimental data, the Response Surface Methodology (RSM) was used and three above mentioned parameters applied as independent variables. Based on results the accuracy of the mathematical model was high and the R-squared reported equal to 0.9986 and the margin of deviation (MOD) was −1.59% < MOD<1.99%. Based on sensitivity analysis the μnf sensitivity to volume fraction of nanoparticles increased with increasing φ. Using numerical simulation, it was found that with increasing the volume fraction of nanoparticles in the base fluid, has a direct relation with pressure loss and applied shear stress and will increase both mentioned parameters.