Rheological Behavior and Thermal Conductivity of Graphite-Ethylene Glycol Nanofluid

The rheological behavior and thermal conductivity of graphite-ethylene glycol (EG) nanofluid is investigated in this research work. The nanofluid is prepared by two-step method using polyvinylpyrrolidone as surfactant. Volume concentration (vol. %) of 0.2, 0.8, and 2 % graphite-EG nanofluid are prepared by ultrasonicating for 5 h. Initially, the effect of temperature variation from 25 degrees C to 60 degrees C (with a difference of every 2.5 degrees C) on the viscosity of prepared nanofluid for different volume concentrations is studied at a fixed shear rate of 25 s(-1). The effect of shear rate from 0.1 to 100 s(-1) on the viscosity of nanofluid is tested at a fixed temperature of 25 degrees C. The nanoparticle size considered for analysis of viscosity is <50 nm. Viscoelastic behavior of the nanofluid with respet to change in amplitude and frequency is investigated for 0.2 vol. %. The viscosity analysis is carried out considering graphite nanoparticles of size <50 nm. Later, the thermal conductivity of prepared nanofluid is investigated at a constant temperature (25 degrees C) for nanoparticle sizes of <50 and <100 nm. Finally, from this complete investigation it is concluded that the viscosity of nanofluid increased slightly from 17 to 19 cP with an increase in volume concentration but decreased by 58 % with an increase in temperature. The thermal conductivity for 2 vol. % nanofluid with nanoparticle size <50 nm is found to increase by 16.3 % compared with nanoparticle size <100 nm.