Development of a fluorescence imaging method to measure void fractions of gas–liquid two-phase flows in a small tube-window for transparent fluids

Abstract In order to investigate the characteristics of gas-liquid two-phase flows in horizontal mini circular tubes with inner diameters of 3.14 and 6.68 mm, a prism is adopted to improve the light path in the visualization experimental setup. The front and top views of air-water two-phase flow patterns in two tubes are captured synchronously based on the improved method. Three-dimensional gas-liquid interfaces, flow pattern maps, and void fraction are obtained. The experimental results show that tube diameters have significant effects on flow patterns transition lines in the flow pattern maps, but the void fractions are independent on channel sizes. The effect of gravity gradually decreases with decreasing tube diameter, while that of surface tension is enhanced. As a consequence, the proportion of annular flow in flow pattern map increases in mini tubes, while the reverse is true for the stratified flow whose proportion decreases dramatically in mini channels. The void fraction increases with increasing gas quality. Experimental void fractions obtained using the three-dimensional gas-liquid interfaces fit well with correlations in the open literature. The shape of PDF distributions varies with flow patterns, which could be used to identify flow patterns in industrial applications.

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Pressure drops and void fractions in horizontal two-phase flows of potassium

AIChE Journal ◽

10.1002/aic.690120112 ◽

1966 ◽

Vol 12 (1) ◽

pp. 50-58 ◽

Cited By ~ 4

Author(s):

Lowell R. Smith ◽

M. Rasin Tek ◽

Richard E. Balzhiser

Keyword(s):

Two Phase Flows ◽

Two Phase ◽

Pressure Drops ◽

Void Fractions

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Streamwise Fluidelastic Instability of Tube Arrays in Two-Phase Cross Flow

Volume 4A: Dynamics, Vibration, and Control ◽

10.1115/imece2014-39234 ◽

2014 ◽

Cited By ~ 1

Author(s):

Stephen Olala ◽

Njuki W. Mureithi

Keyword(s):

Nuclear Power ◽

Single Phase ◽

Cross Flow ◽

Force Measurements ◽

Two Phase Flows ◽

Two Phase ◽

Fluid Force ◽

Void Fractions ◽

Tube Arrays ◽

Fluidelastic Instability

In-plane instability of tube arrays has not been a major concern to steam generator designers until recently following observations of streamwise tube failure in a nuclear power plant in U.S.A. However, modeling of fluidelastic instability in two-phase flows still remains a challenge. In the present work, detailed steady fluid force measurements for a kernel of an array of tubes in a rotated triangular tube array of P/D=1.5 subjected to air-water two-phase flows for a series of void fractions and a Reynolds number (based on the pitch velocity), Re = 7.2 × 104 has been conducted. The measured steady fluid force coefficients and their derivatives, with respect to streamwise static displacements of the central tube, are employed in the quasi-steady model [1, 2], originally developed for single phase flows, to analyze in-plane fluidelastic instability of multiple flexible arrays in two-phase flows. The results are consistent with dynamic stability tests [3].

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Development of a New Void Fraction Correlation for Modeling Two-Phase Flow in Producing Geothermal Wells Using Artificial Neural Networks

Volume 5: Energy Systems Analysis, Thermodynamics and Sustainability; NanoEngineering for Energy; Engineering to Address Climate Change, Parts A and B ◽

10.1115/imece2010-40444 ◽

2010 ◽

Author(s):

A. A´lvarez del Castillo ◽

E. Santoyo ◽

O. Garci´a-Valladares

Keyword(s):

Transfer Function ◽

Void Fraction ◽

Input Data ◽

Field Data ◽

Empirical Correlation ◽

Two Phase Flows ◽

Two Phase ◽

Void Fractions ◽

Geothermal Wells ◽

Artificial Neural

An artificial neural network (ANN) was used to develop a new empirical correlation to estimate void fractions for modeling two-phase flows in geothermal wells. Flowing pressure, wellbore diameter, steam quality, fluid density and viscosity, and Reynolds numbers were used as input data. An explicit relationship among the input data was obtained from an ANN model. A computational architecture based on, the Levenberg-Marquardt optimization algorithm, the hyperbolic tangent sigmoid transfer-function, and the linear transfer-function, was designed. A geothermal database containing thirty-two data sets logged in production well tests were used both to train and to validate the ANN. The best training results were obtained for an ANN architecture of five neurons in the hidden layer, which made possible to predict void fractions with a satisfactory efficiency (R2 = 0.992). From this ANN training pattern, a new empirical correlation was developed and coupled into a wellbore simulator for modeling two-phase flows in other geothermal wells (to avoid bias). Four well-known engineering correlations for calculating the void fraction were simultaneous evaluated. The simulated results (obtained with the five void fraction correlations) were statistically compared with measured field data. A better agreement between simulated and field data was systematically obtained for the new ANN correlation with matching errors less than 3%. These results suggest that the new empirical correlation can be reliable used to estimate void fractions in two-phase geothermal wellbores.

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Numerical Modeling of Two-Phase Flows Using Advanced Two Fluid Systems

10th International Conference on Nuclear Engineering, Volume 3 ◽

10.1115/icone10-22346 ◽

2002 ◽

Cited By ~ 8

Author(s):

Anela Kumbaro ◽

Imad Toumi ◽

Vincent Seignole

Keyword(s):

Fluid Model ◽

Interfacial Area ◽

Group Model ◽

Two Phase Flows ◽

State Equations ◽

Two Phase ◽

Interfacial Area Concentration ◽

Void Fractions ◽

Two Fluid Model ◽

Two Fluid

The purpose of this paper is to report on the development and assessment of approximate Riemann solver methods for the discretization of non-linear non-conservative systems arising in the simulation of two-phase flows. These methods are able to treat general two-phase flow systems with realistic state equations and are flexible enough to be applied on any mesh type, structured as well as unstructured. We will detail models that go from the basic 6 equation two-fluid model to the coupling of this system with one or more transport equations, for instance on volumetric interfacial area concentration, or on partial void fractions of groups of bubbles (MUlti-Size-Group model). This kind of transport equation is useful to predict at a finer level the interfacial patterns or bubble size distribution and takes account of coalescence or breakup rates of inclusions. We make a glimpse at the choices made regarding this aspect. Different physico-numerical benchmarks are provided in order to illustrate the numerical and physical modeling. Confrontation with experimental or analytical reference data are performed whenever possible. Computer simulations are performed using OVAP, a new multidimensional CFD code.

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An Improved Scaling Model of Buffeting Lift Forces in Air-Water Flows

Journal of Pressure Vessel Technology ◽

10.1115/1.4002803 ◽

2011 ◽

Vol 133 (2) ◽

Author(s):

Sylviane Pascal-Ribot ◽

Yves Blanchet

Keyword(s):

Cross Flow ◽

Tube Diameter ◽

Two Phase Flows ◽

Two Phase ◽

Scaling Model ◽

Void Fractions ◽

Precise Knowledge ◽

Series Of Experiments ◽

Lift Forces ◽

Different Diameters

This paper presents the results of a series of experiments to study the influence of diameter on the loading of a single rigid cylinder subjected to air-water cross-flow. Five rigid cylinders of same length and different diameters (12.15×10−3 m to 31.9×10−3 m) were tested over void fractions ranging from 10% to 80%. The fluctuating lift forces on the cylinder are measured and represented in the form of power spectral density. A scaling model of these forces previously developed from one series of experiments with one tube diameter (12.15×10−3 m) is tested on these new results by investigating the effect of tube diameter D. Unlike single phase results where the force spectra vary as D3, it is shown that for two-phase flows, the force spectra vary as D2. The experimental data collapse remarkably well. Both local void fraction and flow regime appear to be sensitive parameters. It confirms the importance of a precise knowledge of the local characteristics of two-phase flows in the study of buffeting forces mechanisms.

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Fluidelastic Instability of Flexible Tubular Cylinders Subjected to Two-Phase Internal Flow

Flow-Induced Vibration ◽

10.1115/pvp2003-2091 ◽

2003 ◽

Cited By ~ 1

Author(s):

Christine Monette ◽

Michel J. Pettigrew

Keyword(s):

Internal Flow ◽

Gas Flows ◽

Two Phase Flows ◽

Two Phase ◽

Void Fractions ◽

Fluidelastic Instability ◽

Piping Systems ◽

Phase Liquid ◽

Series Of Experiments ◽

Different Diameters

The fluidelastic instability behaviour of flexible cylinders subjected to internal single-phase (liquid or gas) flows is now reasonably well understood. Although many piping systems operate in two-phase flows, so far very little work has been done to study their dynamic behaviour under such flows. This paper presents the results of a series of experiments to study the fluidelastic instability behaviour of flexible tubular cylinders subjected to two-phase internal flow. Several flexible cylinders of different diameters, lengths and flexural rigidities were tested over a broad range of flow velocities and void fractions in an air-water loop to simulate two-phase flows. Well-defined fluidelastic instabilities were observed in two-phase flows. The existing theory to formulate the fluidelastic behaviour under internal flow was developed further to take into account two-phase flow. The agreement between the experimental results and the modified theory is remarkably good. However, it depends on using an appropriate model to formulate the characteristics of the two-phase flows.

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An Improved Scaling Model of Buffeting Lift Forces in Air-Water Flows

Volume 4: Fluid-Structure Interaction ◽

10.1115/pvp2007-26118 ◽

2007 ◽

Author(s):

Sylviane Pascal-Ribot ◽

Yves Blanchet

Keyword(s):

Cross Flow ◽

Tube Diameter ◽

Two Phase Flows ◽

Two Phase ◽

Scaling Model ◽

Void Fractions ◽

Precise Knowledge ◽

Series Of Experiments ◽

Lift Forces ◽

Different Diameters

This paper presents the results of a series of experiments to study the loading of a single rigid cylinder subjected to air-water cross-flow. Five rigid cylinders of same length and different diameters (12.15×10−3 m to 31.9×10−3 m) were tested over void fractions ranging from 10% to 80%. The fluctuating lift forces on the cylinder are measured and represented in the form of power spectral density. A scaling model of these forces previously developed from one series of experiments with one tube diameter (12.15×10−3 m) is tested on these new results by investigating the effect of tube diameter D. Unlike single phase results where the force spectra vary as D3, it is shown that for two-phase flows the force spectra vary as D2. The experimental data collapse remarkably well. Both local void fraction and flow regime appear to be sensitive parameters. It confirms the importance of a precise knowledge of the local characteristics of two-phase flows in the study of buffeting forces mechanisms.

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