Vertical two‐phase flow: Part II. Holdup and pressure drop

Abstract

AbstractTwo‐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. Pressure drop, holdup and flow pattern data were successfully obtained simultaneously in the three vertical tubes, each 17.30 ft. long, for five different air‐liquid systems at about 25 psia and 50°F‐80°F over flow ranges of 0–700 lbm air/min‐ft2 and 140‐‐25300 lbm liquid/min‐ft2.Pressure drops and liquid holdups were plotted against gas volume flowrate with liquid flowrate as a parameter. From these plots it was found that for a combination of an increase in liquid viscosity and density, and a decrease in surface tension, the frictional pressure drop increased in down flow and decreased in upflow. Holdup, on the other hand, increased for both types of vertical flow with respect to the same combination of parameters.The Lockhart‐Martinelli scheme was satisfactory in correlating frictional pressure drop and holdup in all the flow regimes except the frothy‐slug regime in upflow. In downflow however, the Lockhart‐Martinelli scheme met with limited success because of a strong influence of liquid flowrate, physical properties and pipe orientation.Holdup in the falling film and falling bubbly film regimes in downflow were satisfactorily treated by the drift flux approach which emphasizes the relative motion of the two phases.