GAS-LIQUID SLUG FLOW:

This contribution begins with a discussion of the occurrence and characteristics of slug flow. Slug flow results in high liquid velocities and hence high pressure gradients and large fluctuations in pressure gradient. However, it does provide a means of transporting large amounts of liquid. The most prevalent model of slug flow is the cell model in which a unit cell encompassing the slug and its associated stratified region is set up. To close this model, various relationships are required (slug velocity, void fraction in the slug, slug frequency etc.) and available relationships of this type are discussed. The mixing zone at the slug front is a particularly important one and is discussed in detail. Evaluation of the statistical characteristics of slug flow can be extremely useful in dealing with design problems (for example the maximum length of a slug which influences the separation equipment) and such distributions are discussed. Finally, the two-equation model for gas-liquid slug flow is presented.