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.

Experimental Study of Rheological Behavior of MWCNT-Al2O3/SAE50 Hybrid Nanofluid to Provide the Best Nano-lubrication Conditions.

In this study, MWCNT-Al2O3 hybrid nanoparticles with a composition ratio of 50:50 in SAE50 base oil are used. This paper aims to describe the rheological behavior of hybrid nanofluid based on temperature, shear rate ([Formula: see text] and volume fraction of nanoparticles ([Formula: see text]) to present an experimental correlation model. Flowmetric methods confirm the non-Newtonian behavior of the hybrid nanofluid. The highest increase and decrease in viscosity ([Formula: see text]) in the studied conditions are measured as 24% and - 17%, respectively. To predict the experimental data, the five-point-three-variable model is used in the response surface methodology with a coefficient of determination of 0.9979. Margin deviation (MOD) of the data is determined to be within the permissible limit of - 4.66% < MOD < 5.25%. Sensitivity analysis shows that with a 10% increase in [Formula: see text] at [Formula: see text] 1%, the highest increase in [Formula: see text] of 34.92% is obtained.

The effect of different parameters on ability of the proposed correlations for the rheological behavior of SiO2 -MWCNT (90:10)/SAE40 oil-based hybrid nano-lubricant and presenting five new correlations.

In this study, after investigating the rheological behavior and viscosity of SiO2-MWCNT (90:10)/SAE40 oil-based hybrid nano-lubricant, the theory was studied by response surface methodology (RSM). Experimental results show that viscosity enhancement decreases significantly at a concentration of 0.0625% to -9.22% and at a concentration of 1% with + 48.23% the highest increase of viscosity enhancement is observed. But the main purpose of this study is to present the new two- and three-variable correlation relationships and compare them with each other. The effectiveness of the experimental correlation for predicting the viscosity is investigated. According to the results of the RSM method, in the relations of two variables, the presence of an independent variable of temperature with the volume fraction (φ) has a greater effect compared to using the variable of shear rate (SR) along the φ and increases the accuracy of the mathematical relation.

Adsorption of free radical TEMPO onto Al2O3 nanoparticles and evaluation of radical scavenging activity.

This study describes the adsorption of free radical TEMPO onto Al2O3 nanoparticles in the solvents with different polarities including DMF, methanol, acetone, THF, petroleum ether and n-hexane at ambient temperature to evaluate the radical scavenging activity. The adsorption percentage of radical is calculated by measuring the maximum adsorption intensity of the ultraviolet (UV) absorption spectrum of TEMPO in the presence and the absence of Al2O3 nanoparticles. The morphology of Al2O3 nanoparticles before and after adsorption of TEMPO is studied using transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier-transform infrared (FT-IR) spectroscopy. The adsorption energy and other thermochemical data for the adsorption of TEMPO over different active sites of Al2O3 are estimated via dispersion corrected density functional theory (DFT + Disp). The donor-acceptor interactions between Al2O3 and TEMPO are calculated using natural bond orbital (NBO) theory. It is found that Al2O3 nanoparticles have efficient radical scavenging activity (RSA) in the range of 50-72%. Approximately, a linear relationship between dielectric constant of solvent and the absorption percentage of TEMPO over Al2O3 nanoparticles is achieved. So that with decreasing the polarity of solvent, the adsorption of TEMPO onto Al2O3 nanoparticles is increased. The adsorption of TEMPO over Lewis acidic sites of Al2O3 is more favored than Brønsted acidic and basic sites. The comparison between experimental and calculated IR spectra of TEMPO/Al2O3 complexes provides the good evidence for the adsorption of TEMPO onto the surface of Al2O3 nanoparticles.