Research Papers: Multiphase Flows

Axial Development of Flow Regime in Adiabatic Upward Two-Phase Flow in a Vertical Annulus

[+] Author and Article Information
J. Enrique Julia

Departamento de Ingeniería Mecánica y Construcción, Campus de Riu Sec, Universitat Jaume I, Castellon 12071, Spainbolivar@emc.uji.es

Basar Ozar, Abhinav Dixit, Takashi Hibiki

School of Nuclear Engineering, Purdue University, 400 Central Drive, West Lafayette, IN 47907-2017

Jae-Jun Jeong

 Korea Atomic Energy Research Institute, 150 Dukjin, Yuseong, Daejeon 305-353, Republic of Korea

Mamoru Ishii1

School of Nuclear Engineering, Purdue University, 400 Central Drive, West Lafayette, IN 47907-2017


Corresponding author.

J. Fluids Eng 131(2), 021302 (Jan 12, 2009) (11 pages) doi:10.1115/1.3059701 History: Received June 25, 2008; Revised November 24, 2008; Published January 12, 2009

This study has investigated the axial development of flow regime of adiabatic upward air-water two-phase flow in a vertical annulus. The inner and outer diameters of the annulus are 19.1 mm and 38.1 mm, respectively. The hydraulic diameter of the flow channel, DH, is 19.0 mm and the total length is 4.37 m. The flow regime map includes 72 flow conditions within a range of 0.01m/s<jg<30m/s and 0.2m/s<jf<3.5m/s, where jg and jf are, respectively, superficial gas and liquid velocities. The flow regime has been classified into four categories: bubbly, cap-slug, churn, and annular flows. In order to study the axial development of flow regime, area-averaged void fraction measurements have been performed using impedance void meters at three axial positions corresponding to z/DH=52, 149, and 230 simultaneously, where z represents the axial position. The flow regime indicator has been chosen to be statistical parameters from the probability distribution function of the area-averaged void fraction signals from the impedance meters, and self-organized neural networks have been used as the mapping system. This information has been used to analyze the axial development of flow regime as well as to check the predictions given by the existing flow regime transition models. The axial development of flow regime is quantified using the superficial gas velocity and void fraction values where the flow regime transition takes place. The predictions of the models are compared for each flow regime transition. In the current test conditions, the axial development of flow regime occurs in the bubbly to cap-slug (low superficial liquid velocities) and cap-slug to churn (high superficial liquid velocities) flow regime transition zones.

Copyright © 2009 by American Society of Mechanical Engineers
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Figure 1

Flow regime definitions: (a) bubbly flow, (b) cap-slug flow, (c) churn flow, and (d) annular flow

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Figure 2

Two-phase flow loop

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Figure 3

(a) Air-water mixing unit and (b) measurement port unit

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Figure 4

Flow regime identification methodology

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Figure 5

Flow regime identification results

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Figure 6

Flow regime transitions and critical void fraction dependences with the axial distance: ((a) and (d)) bubbly-to-cap-slug, ((b) and (e)) cap-slug-to-churn, and ((c) and (f)) churn-to-annular flow transitions

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Figure 7

Comparison of flow regime identification results with published flow regime transition models and flow regime concurrence ratio dependence with z/DH: ((a) and (d)) Mishima–Ishii, ((b) and (e)) Kelessidis and Dukler, and ((c) and (f)) Das




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