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Title: Vertical upward flow patterns in small diameter tubes
Authors: Chen, L
Tian, YS
Karayiannis, TG
Keywords: Two-phase flow patterns;Small diameter tubes
Issue Date: 2005
Publisher: Committees of ExHFT-6
Citation: 6th World Conference on Experimental Heat Transfer, Fluid Mechanics and Thermodynamics, Matsushima, Miyagi, Japan, April 17-21, 2005
Abstract: Two-phase flow patterns were studied in vertical small diameter tubes using R134a as the working fluid. The observed flow patterns include bubbly, dispersed bubble, confined bubble, slug, churn, annular and mist flow. Twelve flow pattern maps, derived from four internal diameters (1.10, 2.01, 2.88 and 4.26 mm) and three different pressures (6, 10, 14 bar), are presented. The flow patterns exhibit strong “small tube characteristics” described in earlier studies when the tube diameter is 2 mm or less. Slug-churn and churn-annular boundaries depend on diameter and pressure. Dispersed bubble-churn and bubbly-slug are less affected. The transition boundaries are compared with existing models for normal size tubes showing poor agreement. Various coordinate systems were considered for the flow maps. The results show that the Lockhard-Martinelli Parameter and mass flow flux can account for the effect of fluid pressure on flow patterns.
Appears in Collections:Mechanical and Aerospace Engineering
Dept of Mechanical Aerospace and Civil Engineering Research Papers

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