Comparative rheological study on hybrid nanofluids with the same structure of MWCNT (50%)-ZnO(50%)/SAE XWX to select the best performance of nano-lubricants using response surface modeling

Abstract

In engineering topics, knowing about the behavior of fluids has always been important and can play an important role in advancing the industry. Therefore, in recent years, many scientific and research fields have addressed this issue. In this study, for the first time, the rheological behavior of hybrid nano-lubricants containing same percentage of ZnO and MWCNT nanoparticles in SAE50, SAE40 and 5W50 base fluids are statistically and comprehensively investigated. Analysis shows that the studied nano-lubricants follow non-Newtonian behavior in all conditions. By adding nanoparticles to 5W50 base oil at a volume fraction of φ = 1% (highest φ) and temperature of T = 5 °C, the viscosity increased about + 30%, which is the highest viscosity increase among the studied nano-lubricants. On the other hand, MWCNT-ZnO (50:50)/SAE50 nano-lubricant at T = 25 °C had a viscosity difference of − 43.10, which is a significant reduction in viscosity. In addition to the experimental results, the response surface methodology (RSM) applied and a Quartic model was used to model the viscosity behavior with an accuracy of R-Squared = 0.9996 in the form of a mathematical correlation. The range of deviation was − 3.82 % < MOD < 4.40 % and the 22.15 % highest sensitivity was occurred at φ = 1% and T = 50 °C. Competitive comparison and determination of one of the studied nano-lubricants as optimal and desirable nano-lubricants, can have applications such as cooling and lubrication in industries that are face with energy loss due to oil pumping, prevent friction between parts, and brings economic cost savings.