An investigation into the effects of temperature on the rheological characteristics of hybrid nanofluids

Advisors: John Shelton.Committee members: Kyu Taek Cho; Robert Sinko.Includes illustrations.Includes bibliographical references.Over the past several decades, nanofluids have exhibited a great potential of enhanced heat transfer performance over conventional heat transfer fluids. These innovative nanofluids are synthesized through the dispersion of a variety of types of nanometer-sized materials throughout the base fluid that consists of either metal, metal-oxides, or non-metals particle suspensions. These nanoparticle suspensions play an important role in altering the intrinsic properties of a base fluid, and this especially true for its shear viscosity. Studies have shown that the rheological response of the base fluid under shear changes from a characteristic Newtonian behavior to non-Newtonian (shear thinning) behavior when there is an increase in particle suspension concentration. Other studies have shown that the dynamic viscosity of nanofluid increases with an augmentation of particle volume fraction (for a given temperature), but decreases with increasing temperature (for a given particle concentration). The Present study experimentally determines how the particle concentration, type of particle, and temperature affect the viscosity of hybrid nanofluids which is the main parameter that influences the rheological properties of a fluid based on range of shear rates for various concentrations while focusing primarily the effect of temperature on viscosity. The experiment determines the effect of temperature (25℗ʻC -- 80℗ʻC), nanoparticle type, and nanoparticle volumetric concentration (0.2% -- 1.5%) on viscosity of Al2O3, TiO2 and a mixture of Al2O3 -- TiO2 with paraffin oil as the base fluid. Brookfield Dv2T rotational viscometer with a cone (CPA--40Z) and plate apparatus is used to measure the viscosity and the temperature is varied by connecting a temperature bath to the viscometer externally. Results shows that the fluid behavior changes from Newtonian to non-Newtonian upon addition of nanoparticles, the nanofluid samples also followed the power law model with the consistency index and the flow behavior index obtained from the curve fitting of shear rate -- viscosity and shear rate -- temperature dependency.M.S. (Master of Science