A Semi-Empirical Model for Predicting the Effective Dynamic Viscosity of Nanoparticle Suspensions

A semi-empirical model for predicting the effective dynamic viscosity of nanofluids, based on a single set of experimental data available in the literature for silica nanoparticles suspended into ethanol, is presented and discussed. The equation, which includes the overall effects of the friction at the solid-liquid interface, the nanoparticle colloidal interactions, and the formation of aggregates, expresses the ratio between the effective dynamic viscosity of the suspension and the dynamic viscosity of the pure base liquid as a function of the nanoparticle size and concentration. The predicted results are in rather good agreement with a wide variety of data relative to nanofluids consisting of several combinations of solid and liquid phases, extracted from different sources. The accuracy and ease of application of the proposed equation make it interesting from the engineering point of view, for both numerical simulation purposes and thermal design tasks.