AnnularFlow_web - ENU 4134 – Annular Flow D Schubring...

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Unformatted text preview: ENU 4134 – Annular Flow D. Schubring September 30, 2009 Empirical Analysis of Two-Phase 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 Counter-current two-phase flow – 0.5 I Pressure drop models – 2.5 Annular Flow Topics I Description of the flow regime. I “Traditional” modeling approach. I Modeling of disturbance waves. I Pressure drop modeling. I Film thickness I Film behavior (including laminar vs. turbulent). Remark: the “enrichment” banner will appear on a fair number of slides. This means that the material will not be on a test or homework, and that you can do the project without it. Of course, some of it might make your project/correlations better. Description of Annular Flow Liquid – film (base film and waves), entrained droplets Gas – gas core (dominant) and entrained bubbles. Traditional Modeling Approach – Triangular Relationship A relation among three parameters is asserted: I (Average) film thickness I Film flow rate (entrained fraction) I Interfacial shear stress (pressure gradient) Given any two, the third can be computed (film flow rate comes from integral – y = 0 to y = δ in terms of shear). The link between film thickness and shear stress is termed the film roughness concept . This asserts that interfacial shear is enhanced by the film, which acts as a rough surface. Often ignored: the velocity profile within the film is not known. (Laminar vs. turbulent, unsteady vs. steady.) This an exceptionally challenging measurement. Traditional Modeling Approach – Excess Liquid Concept Liquid is divided between film and entrainment. By simple mass conservation, this is zero sum – more film flow rate means less entrainment....
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AnnularFlow_web - ENU 4134 – Annular Flow D Schubring...

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