The segregated flow pattern

which occurs in a 26.1 mm diameter

horizontal

stainless steel test section

is investigated. Pressure gradient and

in situ

phase distribution data were obtained for different combinations of phase superficial velocities ranging from 0.05 m·s

-1

to 0.96 m·s

-1

. For the current small Eötvös number liquid-liquid system (

E

oD

=4.77)

the dominant effect of interfacial tension and wall-wetting properties of the liquids over the gravity is considered. The approach introduces the closure relationship for the case of turbulent flow in a rough pipe

and attempts to modify the two-fluid model to account for the curved interface. In present flow rates range

wave amplitudes were found small

while interfacial mixing was observed. An adjustable definition for hydraulic diameters of two fluids and interfacial friction factor is adopted. The predicted pressure gradient and

in situ

phase distri-bution data have been compared with present experimental data and those reported in the literature.