07_RegimeMaps_web - ENU 4134 Regime Maps D. Schubring Fall...

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Unformatted text preview: ENU 4134 Regime Maps D. Schubring Fall 2011 Learning Objectives I 1-f-i Characterize the various regimes of two-phase flow I 1-f-ii Use flow regime maps (empirical and model-based) to identify flow regime(s) present in two-phase system I 1-f-iii Identify the importance of coherent structures (waves, droplets, bubbles, etc.) in two-phase flow and in the differentiation among regimes Empirical Analysis of Two-Phase Fluid Mechanics Motivation: for many applications, the analytical two-phase parameters ( { } , S , etc.) from the first few lectures 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 (these slides) and (2) apply regime-specific models/correlations to predict quantities of interest ( dP / dz , etc.). The most important regimes (bubbly and annular) are given most of the regime-specific coverage. Bubbly is key in BWR cores and annular flow is key in SGs and some accident scenarios. 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 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 . In vertical flow, gravity acts parallel to the direction of flow. This adds an additional source of pressure drop ( m g ) and emphasizes the importance of { } , even when a regime-based model is used. Gravity also leads to strongly time-varying parameters ( e.g. , liquid that has negative velocities at times in churn 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 whats there....
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This note was uploaded on 10/22/2011 for the course ENU 4134 taught by Professor Schubring during the Fall '11 term at University of Florida.

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07_RegimeMaps_web - ENU 4134 Regime Maps D. Schubring Fall...

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