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|Type:||Artigo de periódico|
|Title:||Stability Parameter For Two-phase Vertical Annular Flow|
|Abstract:||A good theory of stability is essential to the prediction of flow pattern transition; therefore, it is crucial to the design of two-phase flow systems, since the behavior and performance of such systems (flow rate versus driving head) is inherently dependent on the actual pattern that occurs in the flow (bubbles, slugs, annular, stratified etc.). The objective of this work is to analyze the stability of two-phase vertical annular flow, and to identify a parameter that governs the transition to slug or churn flow. Previous theoretical investigations, found in the literature, were inconclusive or showed results inconsistent with experimental data. Briefly, for those studies, the paradox of vertical annular flow was: `the flow is unstable, therefore it should not exist... but it does'. In the present work the analysis is conducted through two methods - the first method uses a transient simulator, that models the two phases separately; the second method uses linear analysis akin to Kelvin-Helmholtz analysis. For both methods, the effect of the gas compressibility is included. The gas compressibility was neglected by most of the previous studies. The results demonstrate that the gas compressibility is the main governing parameter of stability. Calculations of stable conditions showed very good agreement with the experimental maps of two-phase flow patterns, for pipe inclinations of 5°, 15°, 30°, and 90° (vertical).|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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