New experimental results are presented on the pipeline flow behavior of water-inoil (W/O) emulsions with and without a polymeric additive in the aqueous phase. The emulsions were prepared from three different oils of different viscosities (2.5 mPa s for EDM-244, 6 mPa s for EDM-Monarch, and 5.4 mPa s for Shell Pella, at 25°C). The W/O emulsions prepared from EDM-244 and EDM-Monarch oils (without any polymeric additive in the dispersed aqueous phase) exhibited drag reduction behavior in turbulent flow. The turbulent friction factor data of the emulsions fell well below the Blasius equation. The W/O emulsions prepared from EDM-244 oil exhibited stronger drag reduction as compared with the EDM-Monarch oil. The W/O emulsions prepared from Shell Pella oil exhibited negligible drag reduction in turbulent flow and their friction factor data followed the Blasius equation. The Shell Pella emulsions were more stable than the EDM-244 and EDM-Monarch emulsions. When left unstirred, the EDM-244 and EDM-Monarch emulsions quickly coalesced into separate oil and water phases whereas the Shell Pella emulsions took a significantly longer time to phase separate. The Shell Pella oil emulsions were also milkier than the EDM emulsions. The addition of a polymer to the dispersed aqueous phase of the W/O emulsions had a significant effect on the turbulent drag reduction behavior.

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 surfactantstabilized 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.

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