In this paper the transition boundaries between different flow regimes during cocurrent upflow of gas liquid two-phase mixture through concentric annuli has been predicted theoretically. On the basis of the experimental observations (Das et al., 1999), mechanistic models have been proposed to formulate mathematical equations of the regime boundaries as functions of the annulus dimensions, the physical properties, and velocities of the two phases. The analysis has yielded the bubbly-slug transition to occur at a limiting void fraction of 0.2, and the slug-churn transition to occur due to flooding of the liquid films by the Taylor bubbles. A comparison of the model predictions with experimental data corroborate the suitability of the proposed mechanisms.
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.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.