MEASUREMENTS OF THE LOCAL RELATIVE VELOCITY AND THE PROFILE EFFECTS ON PREDICTION OF THE AREA-AVERAGED RELATIVE VELOCITY

摘要

Measurements of the local relative velocity in vertical air/water two-phase bubbly, cap-bubbly, and slug flows at 10 and 32 pipe diameters from the inlet are investigated. The measurements were performed conducted in an acrylic vertical pipe with an inner diameter of 50 mm and a height of 3.2 m. A four-sensor conductivity probe was used to measure the local gas-phase velocities and void fractions. The void fraction profiles are presented to illustrate the flow structure. These profiles along with a high-speed imaging system were used to classify the flow regimes. A particle image velocime-try system was employed to measure the local liquid-phase velocities. To perform this measurement, the planar laser-induced fluorescence technique and an image pre-processing scheme were used to separate the liquid-phase information from that of the gas phase. The local experimental data are used to investigate the effects of area averaging and to directly calculate the area-averaged relative velocity and the two-phase distribution parameter of the drift-flux model, and then the results are compared with correlations provided in the literature. In addition, the local axial relative velocity obtained from these local gas- and liquid-phase measurements will be useful in benchmarking interfacial momentum transfer models.