Phase and velocity distributions and holdup in high-pressure steam/water stratified flow in a large diameter horizontal pipe

High-pressure (3–12 MPa) steam/water two-phase flow in a 180 mm i.d. horizontal pipe has been experimentally investigated with emphasis on the study of phase and velocity distributions and liquid holdup. The phase and velocity distributions measured along the vertical centerline of the pipe indicate clear separation of the phases across the wavy interface region. The dimensionless velocity profiles in the liquid phase follow the logarithmic distribution near the bottom of the pipe, but deviate away close to the wavy interface due to interfacial shear. The liquid holdup data can be satisfactorily correlated using a Martinelli parameter for mass velocities > 200 kg/m2ms. However, the condition at the outlet of the test section has a significant effect on holdup at mass velocities < 100 kg/m2s. When the water level in the tank, to which the test section discharges, is below the test section outlet, constant values of liquid holdup are obtained at low qualities which depend only on the liquid mass velocity. When the water level in the discharge tank is kept above the test section, the gravity head at the exit decelerates the liquid flow and significantly higher liquid holdup values are obtained. The holdup data at low mass velocities were correlated in terms of dimensionless flow rates for both cases.