An experimental investigation of rheological characteristics of non- Newtonian nanofluids

Rheological characteristics of Al2O3, CuO and TiO2 nano particles were investigated in oil as the base fluid at 1 and 2 wt.%. Constitutive relations for non-Newtonian fluid were discussed based on the power-law model. Measured viscosities of each nanofluid were used to evaluate the power-law and consistency index. Results indicated that the nanofluid viscosity decreased by increasing the concentration. Oil showed shear thickening behavior while nanofluids showed shear thinning behavior. An increase in nano-particle concentration caused a decrease in the power-law index beside an increase in the consistency index. Moreover, the present study showed that the effective viscosity of fluids would be decreased by nanoparticle addition at some wt.% and some shear rates. Furthermore, results showed that the classic models for nanofluid viscosity couldn’t predict their real values of nano fluid viscosity, as the measured values are less than the predicted ones.