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Unformatted text preview: ENU 4134 – Regime Maps D. Schubring October 2, 2009 Empirical Analysis of TwoPhase Fluid Mechanics Motivation: for many applications, the analytical twophase parameters ( { α } , S , etc.) from the first block are hard/impossible to evaluate. It is often easier to develop empirical models based on a particular flow regime, in which certain effects are expected to be dominant. Such an approach proceeds in two stages: (1) identify or model or otherwise determine the flow regime and (2) apply regimespecific models/correlations to predict quantities of interest ( dP / dz , etc.). This block includes 7 class periods. However, it’s wrapped around Exam 1 and (yet another) UF holiday, so it will take 3 weeks. Empirical Analysis of TwoPhase Fluid Mechanics Schedule I Flow Regime Maps – 1 I Annular Flow – 1.5 I Bubbly Flow – 0.75 I Other flow regimes (intermittent and horizontal) – 0.75 I Countercurrent twophase flow – 0.5 I Pressure drop models – 2.5 The emphasis on bubbly flow is due to its importance for nuclear applications. The emphasis on annular flow is due to its importance (steam generators, BWR’s) and to Project #1. Flow Regime Maps I Outline of horizontal and vertical flow regimes seen in these maps. I Mapping coordinates. I Example horizontal and vertical maps. I Vertical flow map of Taitel et al. – theoretically determined transitions. I Flows with phase change and concluding remarks. Horizontal vs. Vertical Flow In horizontal flow, gravity acts perpendicular to the direction of flow As a result, parameters in horizontal flow (local velocity, void fraction, wall shear, etc., etc.) are often functions of θ . In vertical flow, gravity acts parallel to the direction of flow. This adds an additional “source” of pressure drop ( ρ m g ) and emphasizes the importance of { α } , even when a regimebased model is used. Gravity also leads to strongly timevarying parameters ( e.g. , liquid that has negative velocities at times in slug flow). Flow Regimes in Vertical Flow – Hewitt and Hall Taylor Bubbly, slug, churn, annular Flow Regimes in Horizontal Flow – Barnea Regime Identification Subjective – clear tube and see what’s there....
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This note was uploaded on 07/14/2011 for the course ENU 4133 taught by Professor Schubring during the Spring '11 term at University of Florida.
 Spring '11
 Schubring

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