Viscosity of carbon nanotubes water-based nanofluids: Influence of concentration and temperature

• Experimental viscosity of CNT nanofluids for temperature range 0–40 °C.
• Newtonian or shear-thinning behavior following particles volume content.
• Viscosity decreases with temperature.
• Viscosity enhancement due to nanoparticles aggregates.
• Relative viscosity at high shear rate well predicted by modified Maron–Pierce relation with aggregates.

Experimental results on the steady-state viscosity of carbon nanotubes water-based nanofluids are presented considering the influence of particle volume fraction and temperature ranging from 0 to 40 °C. The suspensions consist of multi-walled carbon nanotubes dispersed in de-ionized water and they are stabilized by a surfactant. The aspect ratio of nanotubes is close to 160 and the particle volume fraction varies between 0.0055% and 0.55%. It is shown that the nanofluids behave as shear-thinning materials for high particle content. For lower particle content, the nanofluids are quite Newtonian. It is also observed that the relative viscosity of nanofluids at high shear rate does not vary with temperature. Moreover, the evolution of relative viscosity at high shear rate is well predicted by the Maron–Pierce model considering the effect of nanoparticles agglomerates.