Apparent Viscosity of Oil-Water (Coarse) Emulsion and Its Rheological Characterization During the Phase Inversion Region

Abstract

A series of oil and water (coarse) emulsions has been systematically studied in order to obtain more knowledge about the flow characteristics. Experimental measurements were conducted using Rheo Stress 6000 from Therm O Haake. Several factors such as shear rate, oil volume fraction, temperature, emulsifying agent, and stirring time on the rheological characteristics of emulsions were investigated. The emulsions without emulsifying agent are discussed by Ostwald de Waele model, Casson model, and Bingham model, respectively, according to different oil volume fractions. Sixteen models of the apparent viscosity were evaluated to predict these emulsions. The results show that existing models of the apparent viscosity exhibit large deviations from the experimental data over the range of low and middle oil volume fractions (ϵo < 0.5) due to the droplets fast flocculation, and but can give a good prediction at high oil volume fractions (ϵo > 0.6). Furthermore, emulsifying agent and shear rate have few influences on the phase inversion point and the maximum value of the apparent viscosity appears around ϵo = 0.6. At the phase inversion point, the viscoelastic behavior of the emulsions were also analyzed by shear stress sweeps and frequency sweeps, respectively. These findings are helpful to improve the pipeline transportation of an immiscible oil and water two-phase dispersed flow.