Characterization of subregimes in two-phase slug flow

A new subdivision of the slug flow region, determined on the basis of different how features, is presented. The characteristic features of each subregime have been shown by diffusional analysis of experimental time series relative to intermittent flow. It is found that, at low values of the mixture velocity, V-m = j(L) + j(G), a subregime (elongated bubble with dispersed bubble, EDB) with structural characteristics different from those usually attributed to slug flow (slug, SL) exists. It is demonstrated that the application of slug flow models to the whole slug flow region may lead to errors in the estimation of flow parameters, especially in large-diameter pipes (industrial application). A modification of the existing models for the flow variables (slug translational velocity, slug length and slug void fraction) is proposed in the light of the results obtained and confirmed against present and existing data.