An experimental study on rheological behavior of non-Newtonian hybrid nano-coolant for application in cooling and heating systems

In this paper, the rheological behavior of COOH functionalized MWCNTs-SiO2/EG-water hybrid nano-coolant for application in cooling systems at temperatures ranging from 27.5 °C to 50 °C has been examined. Stable and homogeneous suspensions, with solid volume fractions ranging from 0.0625% to 2% were prepared by dispersing dry MWCNTs and SiO2 nanoparticles (50:50 vol.%) in a specified amount of a binary mixture of EG-water (50:50 vol.%). Viscosity measurements were performed at the shear rate range of 0.612 s−1 to 122.3 s−1 for each nano-coolant sample. Results showed that the base fluid exhibits Newtonian behavior and the nano-coolant samples exhibit a pseudoplastic rheological behavior with a power law index of less than unity (n < 1). The results also revealed that the apparent viscosity generally increases with an increase in the solid volume fraction and decreases with increasing temperature.