The purpose of this research is to investigate the dependence of the viscosity of nanofluids consisting of zirconia nanoparticles dispersed in ethylene glycol on shear rate, temperature, and nanoparticle volume fraction. To the best of our knowledge, this is the first research on the rheological properties of nanofluids of zirconia nanoparticles and ethylene glycol. The measured viscosity for the nanofluids was in general much higher than for pure base fluid. In addition, the measured results demonstrate that the viscosity of nanofluids increases with increasing the particle volume fraction and decreases with increasing temperature as well as shear rate. Our results showed that the nanofluids are non-Newtonian shear-thinning and their shear viscosity depends strongly on temperature. Furthermore, the experimental results were compared with some theoretical models. The nanoparticle suspensions of zirconia in ethylene glycol exhibit that measured values of viscosity of nanofluids are underestimated by the theoretical models.

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