Flow Pattern Transition During Gas Liquid Upflow Through Vertical Concentric Annuli—Part I: Experimental Investigations

Abstract

In the present work, extensive experiments have been carried out on air-water upflow through concentric annuli to identify the distribution of the two phases in the bubbly, slug, and churn flow regimes. A parallel plate type conductivity probe has been indigenously designed and constructed from a unique material for this purpose. The probability density function analysis of the probe signals has been performed for a better appraisal of the flow situation. The unique design of the probe and its extensive use at different axial and azimuthal positions have enabled us to note the asymmetric phase distribution in the slug flow regime. Based on the experimental results, an insight has been obtained into the physical mechanism underlying the transitions between different flow regimes. This has enabled the development of mechanistic models for the transition boundaries between the bubbly-slug and the slug-churn flow regimes. They have been reported in a subsequent paper.