Two-phase Flow In Horizontal Pipe Research Articles

Drift flux modeling of transient high-viscosity-liquid and gas two-phase flow in horizontal pipes

The drift flux model was develop by using two mass conservation equation, a single mixture momentum equation, an algebraic slip relationship, and the new closure relationship for the drift velocity for the case of air and high-viscosity-oil in horizontal and near horizontal pipe. The Finite Volume Method (FVM) with staggered grid system was employed. The flux-splitting scheme was used for discretizing the flux term. The explicit Euler method with the consideration of Courant number. The model was solved using a hybrid shock capturing scheme often used for gas dynamics. Totally 31 transient cases were simulated and compared with the transient experimental result of air and high-viscosity oil data. It is the first time in this study to show that the drift flux model is capable of predicting the transient hydrodynamics of the air and high-viscosity oil cases. This model performed reasonably well with average relative error of 13.55% (Standard Deviation of 11.62%) with respect to experimental results.

Heat transfer correlation for two-component two-phase slug flow in horizontal pipes

Two-component gas-liquid two-phase slug flow in horizontal pipes occurs frequently in many industrial applications. The flow and heat transfer characteristics are complicated due to the intermittent flow structures. In view of the importance of predicting the heat transfer characteristics of the slug flow, this present study aims at developing a semi-theoretical heat transfer correlation for two-component two-phase slug flow based on the concept of Reynolds and Chilton-Colburn analogies. Firstly, an extensive literature review on existing databases and correlations of heat transfer coefficient for two-component two-phase slug flow was conducted. More than 500 experimental data and 8 heat transfer correlations were collected. The comparison between collected database and correlations indicated that none of the correlations could estimate the whole database satisfactorily. The relationship between heat transfer and pressure drop was investigated theoretically and an improved semi-theoretical heat transfer correlation was developed based on Reynolds and Chilton-Colburn analogies and the collected experimental results from 16 sources. The comparison analysis demonstrated that the newly-developed correlation achieved an excellent predictive capability with a wide range of test conditions. The newly developed correlation demonstrated that 91.5% of the data was predicted within ±30% error with the mean absolute relative deviation of 14.0%. In addition, the extension of the new correlation to other horizontal two-phase flow regimes was discussed. The newly-developed semi-theoretical correlation would be useful for predicting heat transfer coefficient of two-component two-phase flow in horizontal pipes.

Experimental study of vertical and horizontal two-phase pipe flow through double 90 degree elbows

This paper presents an experimental study of the characteristics of the two-phase flow through vertical and horizontal pipes connected using 90-degree elbows with an inner diameter of 101.6 mm. 66 flow conditions are performed in this experiment, covering bubbly, plug, slug, pseudo slug, and stratified flow for horizontal pipe, and bubbly, cap bubbly, churn turbulent, and falling film/annular flow for vertical pipe. A detailed flow regime analysis for both horizontal and vertical pipe flow are discussed. Flow regime maps for both horizontal flow and vertical downward flow agree with the existing maps (Mandhane et al., 1974; Qiao et al., 2017). The effect of the elbow on the flow regime transition is primarily discussed based on the experimental results and observations. The effect of elbow observed in this experiment mainly contributes to the large bubble breakup and the change of void distribution. Area averaged void fraction development is presented and the sharp drop of void fraction in vertical downward test section is observed which results from kinematic shock phenomenon. A frictional pressure drop analysis is also studied using Lockhart-Martinelli correlation and it is found that C = 40, 100, and 125 are correlated with the frictional pressure drop data for horizontal, vertical, and whole test sections with minimum differences. With the database, the drift flux model for vertical downward flow (Goda et al., 2003) is validated and the relative difference between model and data is 15.95%.

The development of image processing technique to study the interfacial behavior of air-water slug two-phase flow in horizontal pipes

The aim of the present paper is to propose an image processing technique in order to study the interfacial behavior of air-water slug two-phase flow in horizontal pipes. Here, the experiments were performed in two sets of transparent acrylic pipes with inner pipe diameters of 16mm and 50mm. To observe the interfacial behavior of slug flow, the liquid and gas superficial velocities were set to 0.2–0.77m/s and 0.7–2.83m/s, respectively. Visualization studies by using high speed video camera combined with image processing techniques were since it offered numerous advantages. Moreover, a sequential procedure was implemented for processing of each image. This technique has succeeded to enhance the image contrast and remove the uneven background. Next, a number of steps applied to binary image were also performed in order to remove the dispersed bubble attached on bubble tail which becomes one of the biggest challenges for the visualization studies of slug flow. As a result, the developed image processing technique was able to minimize the errors in order to produce the accurate measurement. Moreover, the processed image have been utilized to gather the quantitative information. It reveals the comprehensive characteristics of slug flow in horizontal pipes. Finally, a good agreement between the present and previous works proves the reliability of the developed technique.

A Study of Flow-Pattern Transitions in High-Viscosity Oil-and-Gas Two-Phase Flow in Horizontal Pipes

SummaryTwo-phase flow pattern is an important parameter for predicting pressure gradient and liquid holdup in mechanistic models, both of which are required to design and operate hydrocarbon production and transportation systems. Existing two-phase-flow mechanistic models have shown various degrees of discrepancy in predicting flow pattern and their transitions for immiscible laboratory-scale flows of gas and high-viscosity Newtonian liquids (mineral oil) caused by the additional complexity that a high liquid viscosity introduces to the two-phase flow behavior. The objective of this study is to improve the high-viscosity oil flow-pattern transition modeling in horizontal pipes for the stratified-smooth (SS)/stratified-wavy (SW) and intermittent/annular transitions. These two transitions were improved by introducing a liquid viscosity-dependent sheltering coefficient model, and a new high-viscosity liquid-level criterion, respectively. An additional objective is to investigate the existing inviscid Kelvin-Helmholtz (IKH), viscous Kelvin-Helmholtz (VKH), and Taitel and Dukler models for the stratified/nonstratified (S–NS) transition, and provide insights on their applications for high-viscosity oil-flow patterns. A validation study of the proposed transition models is carried out with four laboratory-scale two-phase gas/oil flow-pattern experimental data sets covering a wide range of oil viscosities. The validation study revealed that the proposed SS/SW, and intermittent/annular transition models predicted the considered high-viscosity, horizontal flow-pattern data with more accuracy than the Taitel and Dukler and Barnea VKH S/NS models. Furthermore, the validation and comparison of IKH, VKH, and Taitel and Dukler S/NS models show that the IKH model is the simplest one that sufficiently predicts stratified flow for high-viscosity oil, especially for liquid viscosity above 100 mPa·s.

The Finite Element Analysis for a Mini-Conductance Probe in Horizontal Oil-Water Two-Phase Flow.

Oil-water two-phase flow is widespread in petroleum industry processes. The study of oil-water two-phase flow in horizontal pipes and the liquid holdup measurement of oil-water two-phase flow are of great importance for the optimization of the oil production process. This paper presents a novel sensor, i.e., a mini-conductance probe (MCP) for measuring pure-water phase conductivity of oil-water segregated flow in horizontal pipes. The MCP solves the difficult problem of obtaining the pure-water correction for water holdup measurements by using a ring-shaped conductivity water-cut meter (RSCWCM). Firstly, using the finite element method (FEM), the spatial sensitivity field of the MCP is investigated and the optimized MCP geometry structure is determined in terms of the characteristic parameters. Then, the responses of the MCP for the oil-water segregated flow are calculated, and it is found that the MCP has better stability and sensitivity to the variation of water-layer thickness in the condition of high water holdup and low flow velocity. Finally, the static experiments for the oil-water segregated flow were carried out and a novel calibration method for pure-water phase conductivity measurements was presented. The validity of the pure-water phase conductivity measurement with segregated flow in horizontal pipes was verified by experimental results.

Study of liquid–gas two-phase flow in horizontal pipes using high speed filming and computational fluid dynamics

A study of liquid–gas two-phase flow in short horizontal pipes was carried out experimentally using a High Speed Filming (HSF) Analysis and numerical simulations. In the experiments, the flow pattern was determined and HSF were recorded for six experimental cases. Those films were analyzed using an image analysis tool that was developed, and, consequently, the void fraction as a function of time was obtained. Numerical simulations of the two-phase mixture inside the pipe were carried out with a commercial CFD software, using the Volume of Fluid (VOF) method. The void fraction and the flow pattern were thus determined. The results of the numerical simulations were compared in terms of flow pattern with the experimental data and in terms of void fraction with the HSF analysis. A good agreement was found in both cases, especially for annular and slug flow patterns.

Karakterisasi Aliran Uap-Kondensat pada Saluran Mendatar Berdasarkan Pengukuran Temperatur

The objective of the current investigation is to find out temperature distribution regimes in a horizontal pipe when condensation process is happened. The research was conducted at Pusat Studi Ilmu Teknik Universitas Gadjah Mada. The experiment apparatus consists of an inner annulus pipe made from copper (din = 17.2 mm, do = 19 mm) with the length of 1.8 m. The outer annulus pipe is a galvanized iron pipe (din = 108.3 mm, do = 114.3 mm) with the length of 1.6 m. Thermocouples type K 36 TT OMEGA with chromel (+) and alumel (-) materials were used as temperature sensors, to detect the spread of temperature in radial or axial direction along the pipe. The measurement ranged from -50 to 260 oC, with an accuracy of 0.01 °C. A data logger of RX 40 serial (OMRON, 20 Channels) was used to read and record temperature data with the sampling rate of 5 Hz. In the experiment, the water (H2O)was heated using a boiler to generate steam which was then flowed and condensed inside the annulus pipe to form a steam-condensate two-phase flow in horizontal pipe. On the other hand, the water was used as a coolant in the outer of annulus pipe. The results indicated that the temperature distribution regimes are influenced by axial posisition.The farther distances from the inlet the lower the temperatures being recorded which indicate the increase of film condensate thickness. Such phenomena can affect slugging in the location.

Laminar–turbulent transition and wave–turbulence interaction in stratified horizontal two-phase pipe flow

Stratified cocurrent flow of air and water was studied experimentally in a 5 cm diameter horizontal pipe. The velocity in the liquid phase was measured using planar particle image velocimetry, and the instantaneous interfacial profile was recorded using a separate camera. The resulting velocity fields extended from the pipe wall to the wavy interface. The principal aims of the study were to investigate the laminar–turbulent transition of the liquid phase in stratified gas–liquid flow, and to explore the interaction between the transition process and the interfacial waves. The boundaries of transition were determined in both the smooth and the wavy region. The occurrence of waves had the effect of increasing the Reynolds numbers at the end of transition. On the other hand, the transition to turbulence caused a change from the ‘2D small-amplitude’ to the ‘3D small-amplitude’ wave pattern, which were seen to correspond to the capillary–gravity and gravity–capillary solutions of the dispersion relationship respectively. In light of this, the flowmap of the wavy region was recast into Weber number–Froude number coordinates, which provided a physical interpretation of the interaction between the developing turbulence and the changing wave patterns.

Prediction of slug liquid holdup in high viscosity liquid and gas two-phase flow in horizontal pipes

Abstract Liquid holdup in slugs is a critical slug flow characteristic for predicting average liquid holdup and pressure gradient in two-phase pipeline systems and for designing downstream separation and process facilities. Liquid holdup in slugs for high viscosity two-phase pipe flow is poorly understood and inadequately predicted. The objective of this study is to experimentally investigate the effect of high liquid viscosity on slug liquid holdup in horizontal pipes and develop a physical explanation of the experimentally observed phenomenon. Viscous and inertia forces are found to govern the processes of the bubble entrainment, fragmentation and loss in the slug front. These processes, in turn, determine the slug liquid holdup. A new empirical closure relationship is proposed as a function of viscosity (viscous) and Froude (inertia) dimensionless numbers to predict the gas fraction in slugs for high viscosity liquid (180–587 mPa s) and gas flow in horizontal pipes. A validation and comparison study of the proposed empirical correlation with an independent data set showed improvement in accuracy with absolute average error and standard deviation of 11.35% and 9.59%, respectively, over the existing correlations.

Experimental investigation of oil–water two-phase flow in horizontal pipes: Pressure losses, liquid holdup and flow patterns

Abstract Flow experiments have been conducted for oil–water two-phase flow in a horizontal 5.08 cm ID flow loop at a length to diameter ratio of 1311. The fluids were light Malaysian waxy crude oil from the offshore Terengganu (ρo=818 kg/ m 3 , µo=1.75 mPa s and wax content=16.15 wt%) and synthetic formation water. The water-cut was varied between 10 to 90% at nine mixture flow rates of 2.0 to 16.2 cm3/s. Measuring the changes in pressure drop and liquid holdup at different flow rates of oil–water two-phase flow, a new flow pattern was identified. Strong dependence of the oil–water slippage on the minimum flow rate was observed. The highest pressure drop of 11.58 kPa was obtained at maximum flow rate of 16.21 cm3/s and oil fraction of 0.9; while the lowest pressure drop of 1.31 kPa was recorded at the lowest flow rate of 2.03 cm3/s and water fraction of 0.9. The experimental results could be used as a platform to understand better a more complex case of gas/oil/water concurrent flow in a pipeline.

Development and statistical characterization of slug in two-phase flow along horizontal pipeline

In many industrial processes, the presence of liquid and gas mixtures creates a slug flow. This kind of regime is observed when slug’s liquid blocks the whole pipeline and moves as a coherent mass downstream at a velocity approximately equal to the gas velocity. The aim of this study is to provide statistical information on slug in two-phase flow in horizontal pipe. Experiments were conducted in a pipe of 0.04 m diameter and a length of 14 m. First of all, a flow regime map is compiled for air/water two phase flows. Data on pressure gradient, slug frequency and liquid holdup are presented. It was found that mean slug frequency clearly increases as the superficial liquid velocity increases but it weakly depends on the superficial gas velocity.

Experimental Investigation of Horizontal Gas–Liquid Stratified and Annular Flow Using Wire-Mesh Sensor

Stratified and annular gas–liquid flow patterns are commonly encountered in many industrial applications, such as oil and gas transportation pipelines, heat exchangers, and process equipment. The measurement and visualization of two-phase flow characteristics are of great importance as two-phase flows persist in many fluids engineering applications. A wire-mesh sensor (WMS) technique based on conductance measurements has been applied to investigate two-phase horizontal pipe flow. The horizontal flow test section consisting of a 76.2 mm ID pipe, 18 m long was employed to generate stratified and annular flow conditions. Two 16 × 16 wire configuration sensors, installed 17 m from the inlet of the test section, are used to determine the void fraction within the cross section of the pipe and determine interface velocities between the gas and liquid. These physical flow parameters were extracted using signal processing and cross-correlation techniques. In this work, the principle of WMS and the methodology of flow parameter extraction are described. From the obtained raw data time series of void fraction, cross-sectional mean void fraction, time averaged void fraction profiles, interfacial structures, and velocities of the periodic structures are determined for different liquid and gas superficial velocities that ranged from 0.03 m/s to 0.2 m/s and from 9 m/s to 34 m/s, respectively. The effects of liquid viscosity on the measured parameters have also been investigated using three different viscosities.

PIV measurements of waves and turbulence in stratified horizontal two-phase pipe flow

Stratified two-phase pipe flow of air and water is studied in a horizontal transparent pipe of 50mm inner diameter with the goal of obtaining detailed velocity measurements and wave characteristics in the flowing liquid layer.The velocity field below the moving interface was measured by combining planar PIV and a profile capturing technique. Depending on the flow rates of air and water, the liquid layer can be laminar, transitional or turbulent, and the interface can be smooth or wavy. Conditional averaging based on the wave phase was applied in order to decompose the velocity field into three components: time-averaged velocity, wave-induced fluctuations and turbulence-induced fluctuations.Detailed interface statistics and phase-averaged velocity fields were obtained for laminar and turbulent wavy cases. The waves are shown to be asymmetric, with gravitational and capillary forces of similar magnitude. The linear wave theory provides a good approximation of the wave-induced velocity profiles. In the region close to the interface, however, the wave nonlinearity caused a deviation. In turbulent cases, a deviation was also observed close to the pipe wall, due to the existence of an oscillatory boundary layer. The separation of wavy and turbulent motion was only partly successful due to the wide range of wavelengths and heights occurring in all the wavy cases.

Experimental investigation of a developing two-phase bubbly flow in horizontal pipe

Experimental results for various water and air superficial velocities in developing adiabatic horizontal two-phase pipe flow are presented. Flow pattern maps derived from videos exhibit a new boundary line in intermittent regime. This transition from water dominant to water–gas coordinated regimes corresponds to a new transition criterion CT=2, derived from a generalized representation with the dimensionless coordinates of Taitel and Dukler.Velocity, turbulent kinetic energy and dissipation rate, void fraction and bubble size radial profiles measured at 40 pipe diameters for JL=4.42m/s by hot film velocimetry and optical probes confirm this transition: the gas influence is not continuous but strongly increases beyond JG=0.06m/s. The maximum dissipation rate, derived from spectra, is increased in two-phase flow by a factor 5 with respect to the single phase case.The axial evolution of the bubble intercept length histograms also reveal the flow organization in horizontal layers, driven by buoyancy effects. Bubble coalescence is attested by a maximum bubble intercept evolving from 2.5 to 4.5mm along the pipe. Turbulence generated by the bubbles is also manifest by the 4-fold increase of the maximum turbulent dissipation rate along the pipe.

A novel Lagrangian algebraic slip mixture model for two-phase flow in horizontal pipe

A novel Lagrangian algebraic slip mixture model (LASMM) has been developed to study multiphase flows. In this model, the slip velocity between continual and dispersed phases was developed through the bubble Lagrangian movement equation. According to the Lagrangian equation, the various interfacial forces at interface of the continual and dispersed phases were considered. Through the connection of the slip velocity, the Lagrangian equation was induced into the governing Eulerian equations of the two-phase mixture flow. This model therefore realized the connection between Eulerian model and Lagrangian model. Through the comparisons of the numerical simulations to the experiments in horizontal pipe, this model was validated.

High viscosity effects on characteristics of oil and gas two-phase flow in horizontal pipes

The flow characteristics of high viscosity oil and gas flow show several significant differences with those of low viscosity liquid. Effects of high viscosity oil on characteristics of oil and gas flow are identified. The present experiments are performed on the flow facility which consists of a test section of 26mm ID and a 5.5m long horizontal pipe. A range of liquid viscosity from 1000cP to 7500cP is investigated. The superficial oil and gas velocities vary from 0.06m/s to 0.5m/s and from 0.3m/s to 12.0m/s respectively. The resulting flow patterns are identified by Electrical Capacitance Tomography (ECT) and confirmed by videos recorded during the experiments. The pressure and liquid holdup data are obtained by using pressure transducers and ECT system. The experimental results are compared with existing models and show significant discrepancies between low and high viscosity liquid and gas flows.

Influence of gravity on gas–liquid two-phase flow in horizontal pipes

Based on volume of fluid (VOF) method, a three-dimensional unsteady mathematical model for gas–liquid two-phase flow in horizontal pipe under various gravities is developed. The flow patterns, void fraction distribution and fluctuation in circular pipes with diameters of 7mm and 10mm under various gravities of 10−4g0, 0.17g0, 0.38g0, and g0 (g0=9.8m/s2) are all presented. The quantitatively characterization for intermittent features of gas–liquid two-phase flow under various gravities is realized by using power spectral density (PSD) analysis to extract the dominant frequencies from massive void fraction fluctuation signals. The results indicate that the gravity plays a significant role in the flow pattern, void fraction distribution and void fraction fluctuation. The flow pattern transition appears as a result of the coalescence of bubbles/plugs induced by bubbles/plugs accumulation and gravity driven drainage of liquid film between coalescing bubbles/plugs with increasing gravity. Moreover, the thicker liquid film at the bottom of bubble/plug unit occurs with increasing gravity, resulting in a larger void fraction at the top layer of pipes and a longer region with zero void fraction at the bottom layer. And also with the increasing gravity, both the average peak value and dominant frequencies of void fraction fluctuation decrease. For the slip ratio, it not only increases with increasing gravity but also with increasing two-phase superficial velocity. However, the influence of gravity on the two-phase flow is weakened by the enhanced role of surface tension due to the reduction of diameter as well as the enhancement of inertial force due to the increase of two-phase velocity.

Numerical study on flow patterns and void fraction distribution in gas-liquid two-phase flow in horizontal pipe under different gravities

基于VOF方法建立了不同重力条件下水平管内气液两相流动的三维非稳态数学模型并进行了数值求解, 研究了10^-4g<SUB>0</SUB>, 0.17g<SUB>0</SUB>, 0.38g<SUB>0</SUB>, 1g<SUB>0</SUB> (g<SUB>0</SUB>=9.8m·s^-2)四种重力条件下水平管内气液两流型及变化规律, 比较了不同重力条件下管内截面空隙率的分布和波动规律. 研究结果表明, 该模型能够正确预测不同重力条件下水平管内气液两相流的流型、截面空隙率和滑速比等重要参数; 同一气液两相表观速度工况下, 随着重力水平的升高, 气相更容易在水平管的上部积聚合并, 致使流型发生变化, 同时, 气液两相滑速比增大, 截面空隙率波动峰值的平均值下降, 波动频率降低; 而随着气液两相表观速度的增大, 两相混合工质内惯性力作用也随之增强, 这将削弱重力变化的影响.

Experimental investigation of horizontal gas-liquid slug flow by means of wire-mesh sensor

The monitoring and visualization of two-phase flow is of great importance either from technical/practical point of view for process control and supervision or from scientific/theoretical point of view, for the understanding of physical phenomenon. A wire-mesh sensor was applied to experimentally investigate two-phase horizontal pipe flow. Furthermore, some physical flow parameters were extracted based on the raw measured data obtained by the sensor. In this article, first, the work principle of wire-mesh sensors is revised and, second, the methodology of flow parameter extraction is described. A horizontal flow test section comprising of a pipe of 26 mm i.d. 9 m long was employed to generate slug flows under controlled conditions. An 8 × 8 wire-mesh sensor installed at the end of the test section delivers cross-sectional images of void fraction. Based on the raw data, mean void fraction, time series of void fraction and characteristic slug frequency are extracted and analyzed for several experiments with different liquid and gas superficial velocities.