Experimental observations of the effects of shear rates and particle concentration on the viscosity of Fe2O3–deionized water nanofluids

We report here some experimental observations on the effects of the shear rates and particle volume fractions on the shear stress and the viscosity of Fe2O3–DW nanofluids with Polyvinylpyrrolidone (PVP) or Poly(ethylene oxide), PEO, as a dispersant. The measurements were performed using a Brookfield DV-II Pro Viscometer with a small sample adapter (SSA18/13RPY). The results reported here clearly demonstrate that these fluids had a yield stress and behaved as shear-thinning non-Newtonian fluids. The yield stress decreased to the Newtonian limit, as the particle volume fraction decreased and still existed even at very low particle volume fractions. It was observed that the prepared Fe2O3–DW-0.2% PVP nanofluids with particle volume fraction ϕ less than 0.02 still behaved as a Newtonian fluid. As the volume fraction was increased beyond 0.02, the fluid became non-Newtonian with shear-thinning behavior. Similar results were also observed when DW-0.2% PEO was used. The suspension, however, exhibited its non-Newtonian, shear-thinning behavior at ϕ as low as 0.02.