Flow Pattern, Holdup and Pressure Drop in Vertical and Near Vertical Two- and Three-Phase Upflow

Abstract

Two-phase, air and water near vertical upflow showed significant differences to vertical and other greater inclinations. New relations are presented for prediction of holdup and transitions between fiow regimes for the near vertical case. Three-phase, oil, water and air near vertical upflow exhibit two new flow regimes which were not found in + 90° vertical upflow; a regime possessing a clear water stratified layer and semi-annular curl flow. Flow regime maps are presented and there was a significant difference between the near vertical case and the vertical upflow map in the low gas flow region where the superficial gas velocity was below V¯SG = 10ms−1 and around the inversion point between water dominated and oil dominated flows at higher gas flow rates. Relations are presented for the transitions between water and oil dominated regimes and two annular regimes in the water dominant area. In general, the liquid holdup for near vertical flow was greater than for vertical upflow, the exception being at low liquid superficial velocities of under 0.06 ms−1 and high superficial gas velocities of over 20 ms−1. Here the liquid holdup varied being sometimes below and other times above the corresponding vertical value. These variations of liquid holdup were shown to depend on the fine structure of the flow patterns present. The total pressure drop and its component parts showed significantly different patterns of behaviour depending on whether the superficial gas velocity was above or below the rise velocity of a Taylor bubble. The total pressure drop generally was greater for near vertical flow compared to the vertical up flow case and reflected changes in the fine structure of the flow patterns.