Experimental investigation of the effects of temperature and mass fraction on the dynamic viscosity of CuO-paraffin nanofluid

In this study the effects of mass fraction of CuO nanoparticles and temperature was investigated on the dynamic viscosity of liquid paraffin based nanofluid. For this purpose, CuO nanoparticles were prepared by using precipitation method in which Cu(NO3)2·3H2O was used as a precursor. Moreover, in order to assess the morphology and stability of nanoparticles, TEM and DLS analysis as well as zeta potential test were performed on CuO nanoparticles. The results of TEM analysis indicated that the average nanoparticles diameter was ranged from 15 to 30 nm. In addition, the results of experiments indicated that with the enhancement of nanoparticles load the ratio of the dynamic viscosity of nanofluid to basefluid increases and with the increase of temperature the viscosity of nanofluid declines significantly. Moreover it was concluded that dynamic viscosity of nanofluid increases at the condition where CuO mass fraction was chosen to be above 1.5 wt% while at the condition below 1.5 wt% the change in viscosity is not highly tangible. Finally, a unique empirical correlation including temperature and mass fraction of CuO nanoparticles was obtained based on regression analysis and used for calculating the relative viscosity of nanofluid. The results of regression analysis exhibited that the deviation of the data obtained by correlation from the experimental values was mostly less than 5% and the results of sensitivity analysis showed that the nanofluid viscosity is more sensitive to nanoparticles mass fraction in comparison with the temperature.