Vertical two-phase flow part I. Flow pattern correlations

Two-phase gas-liquid flow has been investigated in a 1-inch internal diameter vertical tube coil containing two risers and a downcomer all connected by “U” bends. Flow pattern data were obtained in the three vertical tubes, each 17.30 ft. long, for five different air-liquid systems at about 25 psia over flow ranges of 0–700 lb_m air/min-ft² and 140–25300 lb_m liquid/min-ft². Liquid phase viscosities ranged from 1 to 12 cp. A flow pattern classification with six regimes including coring-bubble, bubbly-slug, falling film, falling bubbly-film, froth and annular flow regimes was established for downflow. Flow patterns in the bends were also classified. Data from the present investigation were used to formulate an empirical flow pattern graphical correlation for both upflow and downflow which is based upon the coordinates (R_v)^1/2 and Fr_TP/A, where R_v is the delivered gas-to-liquid volume ratio, Fr_TP is the mixture Froude number, and A = μ_s/(S_L^σ_s³)^1/4 in which μ_s, S_L, σ_s are specific viscosity, specific density and specific surface tension respectively of the liquid with reference to water. The correlation was satisfactorily tested with independent literature data for upflow systems, including air-water, steam-water at various pressures, nitrogen-mercury and air-heptane, and data from flowing gas-oil wells. No independent literature data appear to be available for testing the correlation for downflow systems, but it is anticipated that the correlation will prove to be generally applicable. The coring phenomenon in downward bubble flow was examined by means of high speed motion photography and is explained by the development of a lift force on a bubble.