The Effect of Particle Disaggregation on Viscosity of Fe3O4 Ethylene Glycol-Water Nanofluid

This work aims to investigate the effect of particle disaggregation on viscosity of Fe3O4 ethylene glycol-water nanofluids. A modification of citric acid was used to cover the surfaces of Fe3O4 nanoparticles with carboxyl groups, which enabled particle disaggregation to be promoted by enhancing the surface potential of particles through rising up the pH value. After adding the modified particles to 1: 1 ethylene glycol-water mixture, all the nanofluids exhibited obvious shear thinning despite particle concentration. Einstein equation failed to predict the viscosity of the nanofluid. With promoting particle disaggregation, shear thinning became less apparent and the viscosity of the nanofluid was also reduced. When the particles were highly dispersed, all the nanofluids behaved as Newtonian fluids. The viscosity of the nanofluid was exactly consistent with Einstein equation.