Investigating the rheological behavior of a hybrid nanofluid (HNF) to present to the industry

Hybrid nanofluids (HNFs) are potential fluids that have higher thermophysical properties than conventional nanofluids of heat transfer and viscosity. HNF is a new generation of nanofluid that is produced by dispersing two or more types of dissimilar nanoparticles (NPs) in the base fluid. In this study, the rheological behavior of MWCNT (25%)-MgO (75%)/SAE40 HNF was investigated experimentally, statistically and numerically. Temperature conditions are in the range of T = 50-25 °C, solid volume fractions (SVFs) are in the range of SVF = 0.0625-1% and shear rate (SR) is in the range of SR = 666.5-7998 s^-1. This study aims to identify the rheological behavior of HNF based on the effective factors of temperature, SR, and SVF. Various methods show that HNFs exhibit non-Newtonian behavior. The numerical values of the power-law index (n) at T = 50 °C and SVF = 0.75% show the strongest non-Newtonian behavior of HNF and n = 0.9233 is reported. Using laboratory findings, the maximum and minimum viscosities of the base oil increase and decrease by 24% and -8.50%, respectively. Using the response surface methodology (RSM), the relationship between experimental data and modeled data is determined. A quadratic three-variable model with R² = 0.9994 is used to predict the data.