In this study, the effects of incorporatingMWCNTs nanoparticles on paraffin liquid-based viscosity behaviorwere examined. Viscosity of the prepared samples ofMWCNTs-liquid paraffin is measured within the temperature of 5–65 °C at volume fractions of 0.005, 0.01, 0.05, 0.1, 0.5, 1 and 5%. Experiment results showed that nanofluid of MWCNTs-liquid paraffin should be characterized as a fluid with non-Newtonian behavior (shear-thinning). The behavior of the consistency index is such that it tends to decrease with increasing temperature and decreasing volume fraction. Itwas observed thatwith increasing volume fraction or temperature, fluid behavior deviates more fromNewtonian behavior (decreasing power-lawindex). Temperature and volumefraction are two important and effective parameters on nanofluid viscosity. Increasing the temperature strengthens the effect of the volume fraction on the viscosity, but increasing the volume fraction weakens the effect of temperature on the viscosity. Due to the increase in volume fraction, the maximum intensification in viscosity was calculated to be 12.66%. Finally, two correlations were derived to calculate the consistency index and power-law index, respectively.
