An experimental investigation and new correlation of viscosity of ZnO-EG nanofluid at various temperatures and different solid volume fractions

This paper presents an experimental investigation on effects of temperature and particle volume concentration on the dynamic viscosity of ZnO-EG nanofluid. The viscosity of Zinc oxide nanoparticles with mean diameter of 18 nm dispersed in ethylene glycol was determined by using a 'Spindle-type' Brook-field commercial viscometer. The experiments were conducted for the temperatures ranging from room condition up to 50 C, while the nano-fluids and the particle volume fraction ranging from 0.25% to 5%. It has been found that, in general, the nanofluid dynamic viscosity increases considerably with particle volume fraction but does not significantly change (decrease) with increasing temperature. Two experimental correlations were developed based on the data, which relate the viscosity with particle volume fraction and the nanofluid temperature. The proposed models showed reasonably excellent agreement with the experimental results. The Data has also shown that the Einstein's formula and some other ones originated from the classical linear fluid theory seem to be limited to nanofluids of only low particle fractions. (C) 2014 Elsevier Inc. All rights reserved.