What is the rheological behavior of MWCNT-MgO(30:70)/SAE50 hybrid nanolubricant? (Focusing on viscosity sensitivity investigation using numerical simulation)

In this paper, the rheological behavior of MWCNT-MgO (30:70)/SAE50 hybrid nanofluid (HNF) is studied experimentally in volume fraction of nanoparticles (NPs) range of φ= 0–1%, temperature range of 25–50 °C and shear rate range of γ̇=666–7998 s−1. Effects of temperature, φ and γ̇on viscosity (μnf) are investigated. Morphology and stability of HNFs are determined with TEM and XRD analysis. Results show that the diameter of NPs is in the range of 30–40 nm. An interesting result is a viscosity reduction (7% maximum) in φ= 0.0625% and T = 40 °C. But at higher φ, μnf is enhanced, as in φ = 1% and T = 25 °C, the maximum growth in μnf has occurred that is 15%. Viscosity reduction at low φ and little increase in μnfin higher φ show that this HNF can have applications other than lubrication. Finally, an empirical correlation consisting of independent characteristics that are not affected by temperature, φ and γ̇are presented for the prediction of relative viscosity of HNF (μr=μnf/μbf). Results show that the deviation of correlation from experimental data was mostly less than 5%. R2 and maximum MOD in the proposed correlation for μrprediction are 0.9619% and 5%, respectively. [Display omitted] •The diameter of the nanoparticles is between 30 and 40 nm.•The highest viscosity reduction (−7%) occurred in a volume fraction of 0.0625%.•A comparison was performed between the viscosity enhancement of different nanofluids.•The viscosity sensitivity analysis for temperature and volume fraction has been performed.