A slug is created from wavy stratified flow regime when the gas velocity is increased, which causes the waves in the liquid film to grow and bridge the top of the pipe. The slug then overruns the slower moving liquid film, and a mixing vortex is created called the mixing zone. Pulses of bubbles are formed within the mixing zone and are shot toward the bottom of the pipe where they may impact and collapse. The collapse of the bubbles on the bottom of the pipe is believed to reduce the efficiency of the corrosion inhibitors and increase the corrosion rate. Experiments have been carried out to determine the liquid holdup within the mixing zone of the slug. Five axial measurements were taken at each radial distance into the slug. The liquid holdup was then integrated across the cross section of the pipe to obtain an average liquid holdup for each radial distance. Four fluids have been studied at a temperature of 40 degree C and a pressure of 0.136 MPa. The fluids used were water, LVT and a 10.9 cP mixture and a 16.6 cP mixture of LVT and Britol, with nitrogen as the gas phase. The effect of the height of the liquid film on liquid holdup was also studied by using three different nondimensional liquid film heights of 0.28, 0.33, and 0.40. The results show that the liquid holdup begins at the liquid holdup of the liquid film before the slug and then increases until the end of the mixing zone is reached. Once past the mixing zone of the slug, the gas becomes uniformly distributed and the liquid holdup becomes constant. Therefore, as the height of the liquid film increases so does the liquid holdup at any given film Froude number. The results also show that as the viscosity of the liquid increases so does the liquid holdup at any given film Froude number. As the film Froude number is increased, the results show that more gas is entrained into the slug at greater distances into the slug. Since the liquid holdup becomes constant once past the mixing zone of the slug, the length of the mixing zone was determined for each film Froude number studied. The results show that the film Froude number increases linearly with the film Froude number and is independent of the viscosity of the liquid in the slug.
Liquid holdup in large diameter horizontal multiphase pipelines
1998
Seiten
Aufsatz (Konferenz)
Datenträger
Englisch
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