Experimental study on factors influencing viscosity of nanofluids

Taking the nanofluids as an object of study, which are respectively prepared with SiO₂ nanoparticles suspended in deionized water, ethylene glycol (EG) and the mixture of above two matters, factors influencing viscosity of the nanofluids were analyzed, such as the particle size, temperature, base fluid composition and the volumetric fraction of nanoparticles etc. Results show that in the same base fluid, the viscosity increases with reducing particle size; the higher the volumetric fraction of EG in the base fluid, the more obvious the effect of temperature on the viscosity; the law governing variation of viscosity with volumetric fraction of nanoparticles agrees well with the modified Krieger & Dougherty formula. However, if the concentration of nanoparticles is higher than 1%, the viscosity of nanofluids using mixed base fluid (50% volumetric fraction of EG) will be much higher than the predictive value, due to different aggregation degrees of nanoparticles.