Flow pattern, holdup and pressure drop in vertical and near vertical two- and three-phase upflow

we-phase, air and water near vertical upflow showed significant differences to vertical and other greater inclinations. New relations are presented fo r prediction of holdup and transitions between flow regimes for the near ve rtical case. Three-phase, oil, water and air near vertical upflow exhibit two new flow r egimes which were nor found in +90 degrees vertical upflow, a regime posses sing 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) over bar(SG)=10 ms(-1) and arou nd the inversion point between water dominated and oil dominated flows at h igher gas how rates. Relations are presented for the transitions between wa ter 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 v ertical 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). H ere the liquid holdup varied being sometimes below and other times above th e corresponding vertical value. These variations of liquid holdup were show n to depend on the fine structure of the flow patterns present. The total p ressure drop and its component parts showed significantly different pattern s 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 compar ed to the vertical upflow case and reflected changes in the fine structure of the how patterns.