Flow regime development analysis in adiabatic upward two-phase flow in a vertical annulus

This work describes the application of an artificial neural network to process the signals measured by local conductivity probes and classify them into their corresponding global flow regimes. Experiments were performed in boiling upward two-phase flow in a vertical annulus. The inner and outer diameters of the annulus were 19.1 mm and 38.1 mm, respectively. The hydraulic diameter of the flow channel, DH, was 19.0 mm and the total length is 4.477 m. The test section was composed of an injection port and five instrumentation ports, the first three were in the heated section (z/DH = 52, 108 and 149 where z represents the axial position) and the upper ones in the unheated sections (z/DH = 189 and 230). Conductivity measurements were performed in nine radial positions for each of the five ports in order to measure the bubble chord length distribution for each flow condition. The measured experiment matrix comprised test cases at different inlet pressure, ranging from 200 kPa up to 950 kPa. A total number of 42 different flow conditions with superficial liquid velocities from 0.23 m/s to 2.5 m/s and superficial gas velocities from 0.002 m/s to 1.7 m/s and heat flux from 55 kW/m2 to 247 kW/m2 were measured in the five axial ports. The flow regime indicator has been chosen to be statistical parameters from the cumulative probability distribution function of the bubble chord length signals from the conductivity probes. Self-organized neural networks (SONN) have been used as the mapping system. The flow regime has been classified into three categories: bubbly, cap-slug and churn. A SONN has been first developed to map the local flow regime (LFR) of each radial position. The obtained LFR information, conveniently weighted with their corresponding significant area, was used to provide the global flow regime (GFR) classification. These final GFR classifications were then compared with different flow regime transition models.

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

Journal of Fluids Engineering ◽

10.1115/1.3059701 ◽

2009 ◽

Vol 131 (2) ◽

Cited By ~ 17

Author(s):

J. Enrique Julia ◽

Basar Ozar ◽

Abhinav Dixit ◽

Jae-Jun Jeong ◽

Takashi Hibiki ◽

...

Keyword(s):

Flow Regime ◽

Void Fraction ◽

Two Phase Flow ◽

Axial Position ◽

Phase Flow ◽

Regime Transition ◽

Two Phase ◽

Flow Regime Transition ◽

Vertical Annulus ◽

Axial Development

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 0.01 m/s<⟨jg⟩<30 m/s and 0.2 m/s<⟨jf⟩<3.5 m/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.

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Flow regime transition criteria for two-phase flow in a vertical annulus

International Journal of Heat and Fluid Flow ◽

10.1016/j.ijheatfluidflow.2011.06.001 ◽

2011 ◽

Vol 32 (5) ◽

pp. 993-1004 ◽

Cited By ~ 25

Author(s):

J. Enrique Julia ◽

Takashi Hibiki

Keyword(s):

Flow Regime ◽

Two Phase Flow ◽

Phase Flow ◽

Regime Transition ◽

Two Phase ◽

Flow Regime Transition ◽

Transition Criteria ◽

Vertical Annulus

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ESTIMATION OF MAJOR CORRELATIONS FOR FRICTIONAL PRESSURE DROP IN GAS-LIQUID TWO-PHASE FLOW IN HORIZONTAL PIPES USING PREDICTED FLOW REGIME INFORMATION

Multiphase Science and Technology ◽

10.1615/multscientechn.v12.i3-4.100 ◽

2000 ◽

Vol 12 (3-4) ◽

pp. 16 ◽

Cited By ~ 1

Author(s):

S. Momoki ◽

Avram Bar-Cohen ◽

Arthur E. Bergles

Keyword(s):

Pressure Drop ◽

Flow Regime ◽

Two Phase Flow ◽

Phase Flow ◽

Two Phase ◽

Horizontal Pipes ◽

Frictional Pressure Drop

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On Instabilities in Horizontal Two-Phase Flow

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19942595 ◽

1994 ◽

Vol 59 (12) ◽

pp. 2595-2603

Author(s):

Lothar Ebner ◽

Marie Fialová

Keyword(s):

Differential Equation ◽

Flow Regime ◽

Slug Flow ◽

Annular Flow ◽

Two Phase Flow ◽

Phase Flow ◽

Two Phase ◽

Annular Flows ◽

Flow Regime Maps

Two regions of instabilities in horizontal two-phase flow were detected. The first was found in the transition from slug to annular flow, the second between stratified and slug flow. The existence of oscillations between the slug and annular flows can explain the differences in the limitation of the slug flow in flow regime maps proposed by different authors. Coexistence of these two regimes is similar to bistable behaviour of some differential equation solutions.

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