Two-phase Flow In Vertical Pipe Research Articles

An artificial neural network model for the prediction of entrained droplet fraction in annular gas-liquid two-phase flow in vertical pipes

An artificial neural network model for the prediction of entrained droplet fraction in annular gas-liquid two-phase flow in vertical pipes

Experimental Study of Pressure Losses in a Two-Phase Flow in Vertical Pipes

Experimental Study of Pressure Losses in a Two-Phase Flow in Vertical Pipes

Non-invasive measurement of oil-water two-phase flow in vertical pipe using ultrasonic Doppler sensor and gamma ray densitometer

Oil–water two-phase flow experiments were conducted in a vertical pipe to study the liquid–liquid flow measurement using a non-invasive ultrasound Doppler flow sensor and a gamma-ray densitometer. Tap water and a dyed mineral oil are used as test the fluids. A novel Doppler effect strategy is used to estimate the mixture flow velocity in a vertical pipe based on flow velocity measured by the ultrasound sensor and the shear flow velocity profile model. Drift-flux flow model was used in conjunction phase fractions to predict the superficial velocities of oil and water. The results indicate that the proposed method estimated oil-continuous flow and water-continuous flow have average relative errors of 5.2% and 4.5%; and superficial phase flow velocities of oil and of water have average relative errors of 4.5% and 5.9% respectively. These results demonstrate the potential for using ultrasonic Doppler sensor combined with gamma densitometer for oil–water measurement.

Analysis of liquid-liquid (water and oil) two-phase flow in vertical pipes, applying artificial intelligence techniques

Due to the precision of its results, the use of artificial intelligence technology for predictive models for multiphase flow description currently has a considerable impact on industrial applications. This work compares the results obtained in an adaptive neuro-fuzzy inference system with the results obtained in an artificial neural network to predict the holdup of oil in vertical pipes with a water and oil mixture. We use pipe diameter, fluid surface velocity, and oil viscosity as input parameters. The research was conducted using 722 experimental data and found that the best model is a model generated by an artificial neural network with a hidden layer consisting of 12 neurons and using the Levenberg Marquardt training function and the TanSig activation function. The results showed a root mean square error of 0.000049, the coefficient R2 was 0.99932, and the average absolute percentage error was 0.19%. The predictive model can be used to improve transportation processes in the oil and gas sector.

Numerical Prediction of Deposition in Two-Phase Flow in Vertical Pipes

Numerical Prediction of Deposition in Two-Phase Flow in Vertical Pipes

A New Model for Predicting Slug Flow Liquid Holdup in Vertical Pipes with Different Viscosities

The development of heavy oil has attracted attention in recent times. With increasing fluid viscosity, slug flow has become the most common flow pattern in oil and gas pipeline flow. The accurate prediction of slug flow parameters is an urgent problem to be solved in heavy oil development. In this paper, gas–liquid two-phase flow experiments with different viscosities were carried out in a 60-mm vertical pipe. The superficial velocity ranges of gas and liquid were 0.51–7.42 m/s and 0.08–0.21 m/s, respectively. Based on the measured data, the investigation revealed that liquid holdup increases with an increase in viscosity and superficial liquid velocity. This study presents a new liquid holdup model of slug flow for viscous two-phase flow in vertical pipes. Based on the statistical analysis, the proposed correlation accurately predicts the liquid holdup of slug flow in a vertical pipe for the present measured data and performs best in comparison with existing correlations.

Experimental investigations of kerosene-water two-phase flow in vertical pipe

Oil and water two-phase flow studies are important to the oil industries. This paper aims to determine the flow patterns, holdup, pressure losses, phase inversion, drift flux parameters and mixture properties in vertical upward kerosene and water flow. The experiment was conducted in a 26 mm i.d duct with phase velocities spanning from 0.1 to 1.0 m/s. The averaged holdup was measured using quick close valves in a 1.16 m long test section. The same test section was used to measure the pressure drop. A local impedance probe and high-speed films were used to determine the flow patterns. Six different flow patterns was identified: dispersed bubbly (DB), core annular (CA), bubbly (B), churn turbulent (CT), and elongated water drop (EWD). The kerosene holdup was highest for EWD, spanning from 0.8 to 0.9, followed by CT and CA, which spans from 0.35 to 0.75. The kerosene holdup for bubbly spans from 0.12 to 0.6, being the highest range for all patterns. The phase inversion occurs when the kerosene input fraction is βK = 0.35. There is no evidence of slippage between the dispersed and continuous phases. The drift velocity is due to the misalignment of the dispersed fraction and the mixture velocity profile and the distribution parameter is C0 = 1.10. The pressure loss showed a good agreement with Blasius correlation. The exception is for the bubbly and churn turbulent. The density was determined using the homogeneous model and five different mixture viscosity models were investigated. The pressure loss deviation using (Mukhaimer et al., 2015) mixture viscosity spans from 5 to 25%. The drift-flux correlation increase the predictive capability of the oil fractions in oil pipelines, which contribute to the operational security. In addition, a better pressure drop losses estimative provide in this study helps to a better oil pipeline design.

CFD modeling of liquid film reversal of two-phase flow in vertical pipes

The phenomenon of two-phase flows is characterized by its wide range of presence in nature and industrial applications. In gas and oil production, the simultaneous two-phase flow of gases and liquids often occurs in gas wells. The produced gases flow rate decreases over the years until reaching a critical flow rate when they lose their ability to lift the associated liquids upward and the liquid film reverses direction, which triggers liquid loading. Liquid loading causes the produced liquids to accumulate in the bottom of the wellbore, which causes a high back pressure that reduces the well production rate till production is ceased eventually. The critical gas velocity exists in the churn flow regime which is mainly characterized by the oscillatory behavior of the liquids flow field. This study employs CFD techniques to model the churn flow in a 3-inch-diameter vertical pipe near the critical gas flow rate for different liquid flow rates. This work utilizes the two-fluid Eulerian model along with the RNG (Re-Normalization Group) k-ε turbulence model to investigate the behavior of the flow field in a two-dimensional axisymmetric computational domain. Simulations were carried out using the commercial software ANSYS Fluent 18.2 with air and water as the two working fluids. The model results showed a good agreement with the experimental data and proved the mesh and time independence of the model. Oscillatory behaviors of the liquid film flow rate, shear stress, and pressure were observed along with the formation of interfacial waves. Detailed information about the velocity, shear stress, and pressure behaviors is presented. Accordingly, recommendations are suggested for future considerations.

Experimental study on entrained droplets in vertical two-phase churn and annular flows

In this paper, the air-water vertical two-phase pipe flow experiment was carried out at room temperature and pressure to study the characteristics of entrained droplets in churn and annular flows with the high-speed camera and phase Doppler anemometry. The results show that there are five kinds of droplet entrainment modes in churn and annular flows, namely shearing-off of waves, bag break-up of waves, ligament break-up of waves, droplet impacting liquid film, and burst of bubbles. With the flow pattern transition from churn flow to annular flow, the dominant droplet entrainment changes from shearing-off of waves to ligament break-up of waves. The gas superficial velocity plays a decisive role in determining the characteristics of entrained droplets, while the effect of the liquid superficial velocity can be neglected. In churn flow, the shearing-off of waves produces a small amount of entrained droplets with low sphericity and initial velocity. Large droplets tend to deposit, and small droplets undergo a certain degree of fragmentation and coalescence during the accelerated migrating in the gas core. In annular flow, the ligament break-up of waves produces a large amount of entrained droplets with high sphericity and initial velocity. Droplet size presents continuous distribution. The size of droplets increases slightly due to the coalescence of small droplets during the accelerated migrating in the gas core. Compared with churn flow, the momentum exchange between the gas phase and droplets is greater in annular flow, which leads to a significant increase in droplet momentum. The size distribution of the entrained droplets determines the momentum exchange between the gas core and the entrained droplets to a certain extent.

110th Anniversary: Numerical Simulations of Gas–Liquid Two-Phase Flow in Vertical Pipe Implementing Population Balance Modeling

Population balance modeling in a gas–liquid two-phase bubbly flow allows us to predict the bubble size distribution. The prediction of bubble size distribution is of utmost importance as it prevails the heat, mass, and momentum transport mechanisms. In the present work, numerical simulations of gas–liquid two-phase flow in a vertical pipe have been performed using population balance modeling. The effects of different coalescence and breakage models have been studied. The wall peak and core peak case in the bubbly flow regime is considered for the prediction of the radial distribution of the gas void fraction, interfacial area concentration, bubble size distribution, Sauter mean diameter, and gas and liquid velocities. Numerical simulations were performed with the Euler–Euler two-fluid model and the k–ω SST turbulence model. The population balance equation is solved using the traditional class method. The combination of Brownian coalescence and Ghadiri breakage model is recommended for the prediction of th...

Dynamics of two-phase flow in vertical pipes

In this study, a novel mathematical model was proposed for the dynamic analysis of two-phase flow in vertical pipes considering different two-phase flow models by including dissipative forces. To model the corresponding two-phase flow, common slip-ratio factors were utilized. The Galerkin discretization method and eigenvalue analysis were applied to solve the model equations. A detailed parametric analysis was also performed in order to elucidate the influence of various parameters such as volumetric gas fraction, flow velocity, structural damping and gravity parameter on dynamics of the system, critical flutter velocities and frequencies. The model was validated with experimental data and simulation results reported in the literature It was concluded that the pipes conveying two-phase flow are prone to experience several dynamic phenomena. Stability of the pipe structure was also examined for different two-phase flow models and the results indicated that the instability boundaries are significantly affected by the choice of the model. Furthermore, it was shown that the dynamical response of the pipe is substantially dependent on the volumetric gas fraction. Hence, the gas volume fraction can be introduced as a fundamental parameter for the vibration control of the two-phase flow systems. The results of this study would be beneficial for engineers to optimally design suitable structures for two-phase flow systems.

Effect of length-to-diameter ratio on axial velocity and hydrodynamic entrance length in air-water twophase flow in vertical pipes

Effect of length-to-diameter ratio on axial velocity and hydrodynamic entrance length in air-water twophase flow in vertical pipes

Computational Fluid Dynamics Simulations of the Air–Water Two-Phase Vertically Upward Bubbly Flow in Pipes

In this study, computational fluid dynamics (CFD) simulation of air–water two-phase flow in vertical pipe has been carried out. Wide ranges of superficial liquid and gas velocities, 0.376–3.53 and 0.0036–1.275 m/s, and dispersed phase holdup range from 0.3 to 38.74% is used in the simulation. In this study, for drag, lift, wall lubrication, and turbulent dispersion force the models of Grace, Tomiyama, Hosokawa, and Burns are used, respectively. The Eulerian–Eulerian multiphase approach with the k–ω shear stress transport (SST) turbulence model was used. Bubble diameter is an essential parameter to perform the Eulerian simulation. In the present study, we developed new correlation for bubble diameter and with this predicted bubble diameter simulations were performed. The developed CFD model is well capable of predicting gas void fraction, interfacial area concentration, pressure drop, gas/liquid velocity, and turbulent kinetic energy.

Flow patterns and heat transfer of oil-water two-phase upward flow in vertical pipe

In this paper, local heat transfer coefficients (HTC) and different flow patterns of oil-water two-phase flow in a vertical pipe were investigated. The test section was an 11 mm inner diameter (ID) copper pipe with a length to diameter ratio of 145. Water and kerosene (1.49 mPa s viscosity and 780 kg/m3 density) were selected as immiscible liquids and high speed photography technique was used for the flow pattern identification. The superficial Reynolds numbers ranged from 750 to 6000 for oil and 1000 to 11500 for water. The heat transfer experimental data showed a very strong dependency on the flow pattern. In addition, a heat transfer correlation was proposed for churn flow pattern. The experimental data were successfully correlated by the proposed heat transfer correlation with an average deviation of 10.6%, a standard deviation of 5.6%, and a deviation range of −20% to 3%.

Experimental Study on Pressure Drop of the Gas-Liquid Two-phase Flow in Vertical Pipes

In order to study how the pressure drop of gas-liquid flow in vertical pipes varies with flow parameters as well as its calculation method, we conducted experiments in key laboratory of oil and gas exploitation in the Yangtze university. The experimental conditions were as follows: the working pressure from 0 to 3.5 MPa,the superficial liquid velocity from 0.06 to 0.23 m/s, the pipe diameter of DN60, and the pressure drop measuring distance of 8.0m. Experimental results show that liquid velocity and gas liquid ratio affect the value of pressure drop. The classical Beggs-Brill correlation was chosen to predict the value of exit pressure with an average error of 26.20% and an uncertainty of 14.49%. With the further research on the Beggs-Brill correlation, it’s found that the coefficient of drag coefficient of the path is the major factor which influences pressure drop. Finally, the Beggs-Brill correlation is modified by using the method of numerical fitting in the coefficient of drag coefficient of the path, and an average error and uncertainty of the modified Beggs-Brill correlation to predict the value of exit pressure are 12.92% and 8.86% respectively, so we can use the modified Beggs-Brill correlation to calculate the pressure drop of gas-liquid flow in vertical pipes more accurately.

Effect of drops on turbulence of kerosene–water two-phase flow in vertical pipe

The effect of introducing kerosene drops on turbulence of kerosene–water two-phase in a vertical pipe is investigated experimentally. A hot-film and dual optical probes are used to measure the water velocity, turbulence fluctuation, drop relative velocity, volume fraction and drop diameter. Experiments are performed in a 78.8mm diameter vertical pipe for four average water velocities of 0.11, 0.29, 0.44 and 0.77m/s. The measurements were carried out for two area average volume fraction 〈α〉 of 4.6% and 9.2% as well as for water single phase flow to investigate the effect of introducing kerosene drops on two-phase flow turbulence. The kerosene–water mixture was generated by adding the kerosene to constant flow rates of water. The results indicate that drops induced turbulence is a function of the ratio of the drop Reynolds number (UrdB/ν) to the turbulence Reynolds number (u′Lt/ν) which decreased with higher water velocities. The results show that the Kolmogorov–Richardson scaling in the range of −4.5/3 to −6/3 for single phase flow which is replaced by −6/3 to −7/3 for two-phase flow. These values are less than −8/3 for air–water flow.

Measurement of Bubbly Two-phase Flow in Vertical Pipe Using Multiwave Ultrasonic Pulsed Dopller Method and Wire Mesh Tomography

Abstract Two measurement methods which are multiwave ultrasonic pulsed Doppler (multiwave UVP) method and wire mesh tomography (WMT) have been applied to the measurement of bubbly two-phase flow. Velocity profiles of bubbles and liquid have been measured using multiwave UVP. Simultaneously, cross-sectional void fraction distribution has been measured using WMT. As the result, a combination method has been set up. The measured parameters are indispensable in order to obtain detailed structures of two-phase flow. Multiwave UVP method exploits two basic ultrasonic frequencies which are 2 MHz and 8 MHz. Simultaneous measurement of velocity profiles of bubbles (using 2 MHz frequency) and those of liquid (using 8 MHz frequency), at the same position, is enabled. A multiwave ultrasonic transducer (multiwave TDX) which is able to emit and receive the two ultrasonic frequencies along the measurement line at the same time has been applied. The signal processing is based on the pulsed Doppler method. Using the combination method, first, instantaneous velocity profiles and void fraction distribution have been measured simultaneously for air-water counter-current bubbly flow in a vertical pipe. Flow structure has been clarified. Effect of initial condition on void fraction distribution has been confirmed. Next, measurements have been carried out for subcooled boiling bubbly flow in a vertical pipe. For measurement of subcooled boiling flow, a high temperature wire mesh sensor (WMS) has been developed. A method for separation of velocity profiles of bubbles with different sizes and velocities has been suggested.

Heat Transfer Correlation for Two-Phase Flow in Vertical Pipes Using Support Vector Machines

It has been shown by Tam and his coworkers [7] that the support vector machines (SVM) have excellent capability of handling complicated single-phase heat transfer problems. Therefore, it would be logical to extend the investigation to other flow situations, such as two-phase flow or flow in microtubes. In this study, SVM is used to correlate the two-phase, two-component flow data. Four sets of experimental data (a total of 255 data points) for vertical pipes used in this study were from Kim et al. [3]. They proposed a heat transfer correlation for turbulent gas–liquid flow in vertical pipes with different flow patterns and fluid combinations. Their correlation predicted the experimental data with a deviation range of –64.7% and 39.6%. Majority of the experimental data (245 data points or 96% of the data) were predicted within the ±30% range. A new correlation using SVM is developed in this study. The new correlation outperforms the traditional least-squares correlation and predicts the experimental data within the ±15% range.

An experimental study on characteristics of two-phase flows in vertical pipe

The characteristics of two-phase flow in a vertical pipe are investigated to provide information for understanding the excitation mechanisms of flow-induced vibration. An analytical model for two-phase flow in a pipe was developed by Sim et al. (2005), based on a power law for the distributions of flow parameters across the pipe diameter, such as gas velocity, liquid velocity and void fraction. An experimental study was undertaken to verify the model. The unsteady momentum flux impinging on a ‘turning tee’ (or a ‘circular plate’) has been measured at the exit of the pipe, using a force sensor. From the measured data, especially for slug flow, the predominant frequency and the RMS value of the unsteady momentum flux have been evaluated. It is found that the analytical method, given by Sim et al. for slug flow, can be used to predict the momentum flux.

Prediction of the entrained liquid fraction in vertical annular gas–liquid two-phase flow

The study considers the prediction of the entrained liquid fraction in adiabatic gas–liquid annular two-phase flow in vertical pipes. Nine empirical correlations have been tested against an experimental data bank drawn together in this study containing 1504 points for 8 different gas–liquid combinations and 19 different tube diameters from 5.00 mm to 57.1 mm. The correlation of Sawant, Ishii and Mishima and the one of Oliemans, Pots and Trompé were found to best reproduce the available data. A new correlating approach, derived from both physical intuition and dimensional analysis and capable of providing further physical insight into the liquid film atomization process, was proposed and worked better than any of the existing methods. This new correlation is based on the core flow Weber number that is also a controlling dimensionless group in determining the wall shear stress and associated frictional pressure gradient of annular flows.