An Experimental Study on the Rheological Behavior of Carbon Black-Boron Nitride Hybrid Nanofluids and Development of a New Correlation.

Hybrid nanofluids, a new class of nanofluid has the ability to further enhance the thermo-physical properties by balancing the benefits of both kinds of nanomaterials as compared with nanofluids synthesized using only one kind of material. In this work, water-based nanofluids containing suspensions of carbon black (CB)-boron nitride (BN) (mass ratio = 50:50) nanoparticles are synthesized and studied for its rheological properties. The viscosity of CB-BN nanofluids are measured at temperatures between 30 °C-60 °C for volume concentrations 0.25 to 2 vol.%. The viscosity shows an increase with increasing particle concentration and decreases with temperature. A non-Newtonian nature with a dilatant behavior in the shear rate range of 5.4 s-1 to 130 s-1 is observed for all concentrations and temperatures. Also, it follows a power law model and its parameters, i.e., power index and consistency index are obtained by the curve fitting method. The non-Newtonian nature intensifies at low temperatures and concentrations. A new correlation is developed to predict the viscosity of CB-BN hybrid nanofluids.