Effects of Surfactant and Water Concentrations on Pipeline Flow of Emulsions

New experimental results are presented on the effects of surfactant and water concentrations on pipeline flow of emulsions. For a fixed water concentration of 30% by volume, the flow behavior of water-in-oil emulsions containing eight different surfactant concentrations (0, 0.05, 0.1, 0.5, 0.75, 1, 1.5, and 2% by wt based on oil) was investigated in five different diameter horizontal pipes. The surfactant used was oil-soluble Emsorb 2503 (sorbitan trioleate). The influence of water concentration on the pipeline flow behavior of emulsions was determined by varying the water concentration from 30 to 80% by volume in increments of 5%. The emulsions were water-in-oil type until the water concentration was 40% by volume. Upon further increase in the water concentration, inversion of water-in-oil (W/O) emulsion to oil-in-water (O/W) emulsion occurred at a water concentration of 45% by volume. The unstable W/O emulsion without surfactant exhibits drag reduction behavior in turbulent flow; that is, the friction factor data fall well below the single-phase Blasius equation. With the addition of surfactant, the W/O emulsion becomes more homogeneous and the friction factor data fall close to the Blasius equation. However, the surfactant-stabilized W/O emulsions exhibit a significant delay in transition from laminar to turbulent regime. The delay in laminar to turbulent transition depends on the pipe diameter. The O/W emulsions obtained upon phase inversion of surfactant-stabilized W/O emulsion behave as truly homogeneous fluids in that there is no delay in transition and that the friction factor data follow the Blasius equation.