Two-phase flow in horizontal and inclined pipelines cancause significant practical operating problems. When slugsflow in a horizontal pipeline that contains sections of differentinclinations they undergo a change of length and slug flowcharacteristics as the slug move from section to section. Inaddition, slugs can be generated at low elbows, dissipate at topelbows and shrink or grow in length as they travel along thepipe.A mathematical model and a computer program weredeveloped to simulate these phenomena. The model was basedon the sink/source concept at the pipeline connections. Aconnection between two pipeline sections of different slopeswas conveniently called elbow. An elbow accumulates liquidas a sink, and releases liquid as a source. The sink/source has acharacteristic capacity of its own. This capacity is positive ifthe liquid can indeed be accumulated at the elbow or negativeif the liquid is actually drained away from the elbow. This typeof treatment effectively isolates the flow upstream from anelbow from that downstream, while still allowing flowinteractions between two detailed pipeline sections. Thehydrodynamic flow model was also used to calculate the filmliquid holdup in horizontal and inclined pipelines. The modelcan successfully predict the liquid film holdup if the liquidfilm height is assumed to be uniform through the gas pocket.Many other models were used to calculate all the neededparameters to perform the sink/source model.The overall effect of horizontal and inclined pipelines onslug flow depends on the operating flow rates and pipelineconfigurations. For special case of near constant slugfrequency corresponding to moderately high superficial liquidand gas velocities, this effect was found to be small. Thechanges in the film characteristics between two adjacentpipeline sections were found to be mostly responsible for the pseudo-slug generation, slug growth and dissipation in thedownstream pipeline sections. The film liquid holdupdecreased with increasing pipe diameter. The unit slug lengthincreased at the upstream inclined pipes and decreased at thedownstream inclined pipes with increasing pipe diameter. Thepossibility of pseudo-slug generation was increased at largepipe diameters even at high sink capacities. At low sinkcapacities, no pseudo-slugs were generated at high superficialvelocities. The slug flow characteristics were more affected bylow superficial gas and liquid velocities, large pipe diametersand shallow pipeline inclinations.
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