Annular Flow In Horizontal Pipes Research Articles

Specialist system in flow pattern identification using artificial neural Networks

In this work, an application of artificial intelligence in the oils & gas industry is developed to identify flow patterns in horizontal and vertical pipes of two-phase flow of oil and water, normalizing the word information and converting it to numerical values through the development of an artificial neural network, whose input layer is composed of the surface velocities of each fluid, the velocity of the mixture, the volumetric fraction of the substances, diameter and the inclination of pipelines and the oil viscosity. The Artificial Neural Networks (ANN) has two hidden layers composed of 45 neurons. The database with which the model was trained, validated, and tested has 6993 rows of information corresponding to the inputs of the intelligent system and particular-ized for annular flow in horizontal pipes and DO/W in vertical pipelines. Notice that the information was obtained after re-engineering the information presented by 12 and 18 authors for horizontal and vertical piping, respectively. Finally, the mean square error obtained by the model was around 1.38%, with a maximum coefficient of determination of 0.79.

A new two-fluid model for flow rate measurement of annular flow in horizontal pipe

Non-separation measurement is a research difficulty and hotspot in multiphase flow. In this paper, the multimodal ultrasonic sensors and differential pressure transmitter combined with two-fluid model are used to measure the wet gas flow rates under non-separation state. Firstly, a modeling measurement system is built. The liquid film thickness and pressure drop are obtained by using ultrasonic sensor and differential pressure transmitter. Based on the steady-state one-dimensional two-fluid model and the limitations of existing models, a new prediction model is proposed. Comparing the pressure drop data obtained by new two-fluid model with the experimental data, the errors are within ±30%. Then, wet gas flow rates measurement system is constructed. The liquid film thickness and gas velocity are measured by using multimodal ultrasonic sensors. Combined this new two-fluid model, the wet gas flow rates are obtained. The measurement errors of gas and liquid flow rate are within ±10% and ±15%.

A new model for viscous oil-water eccentric core annular flow in horizontal pipes

Eccentric core-annular flow is encountered in water-lubricated transport of highly viscous oil in horizontal pipes. The core eccentricity results from the tendency of the phases to stratify due to a buoyant force that results from their different densities, whereby a shape of a circular core may not be maintained. To model such a flow configuration, a new three-zone model is proposed based on the Two-Fluid approach. The model's performance was examined by comparing its predictions with a large data set of pressure gradient and water holdup values obtained under different experimental conditions. It is shown that the proposed model enables better agreement with the data compared to other models available in the literature. Thus, the proposed approach appears to be a useful framework for modeling viscous oil-water eccentric core-annular flows. It can also be applied for other types of Newtonian/non-Newtonian or non-Newtonian/non-Newtonian liquid-liquid core flows encountered in industrial applications.

Evaluation of Velocity Impact on Sand Particles in Two-Phase Annular Flow in Horizontal Pipes

Experimental investigations on sand particles in annular flow in horizontal pipes were presented. The aim is to enhance the knowledge related to sand transportation in the oil and gas industry. More so, to add values in facilitating the optimum design of oil and gas production systems where annular flow is often encountered. The experimental investigations were conducted using a closed-loop consisting of a horizontal pipe with an internal diameter of 2-inch (0.0504m). The experimental investigations covered both: water/sand flow and water/air/sand annular flow. The water/sand flow experiments were carried out to establish sand transport regime in liquid such as sand saltation, sand streak, and sand suspension. While, water/air/sand annular flow experiments revealed that the only the only sand transport regime in annular flow are saltation and suspension. Sand concentration profile in the annular flows were also estimated by using the sampling method. It was found that the bigger the sand particle size (500microns) leads to higher concentration of sand being transported at the bottom of the pipe because of gravity effect, while the smaller the sand particle size (212microns), leads to the higher sand concentration. Also, the sand concentration increased at the gas core as the superficial gas velocity increases.

A Simplified Calibration of Liquid Hold-Up and Film Thickness in Annular Flow in Horizontal Pipe

Annular flow is majorly encountered in petroleum industry, where gas and liquid are conveyed from gas wells or oil wells (dominated by gas) to the surface through the transport lines. A simplified annular flow bench calibration for liquid hold-up and film thickness in horizontal pipe was conducted using water/air in a 2-inch (50mm) Plexiglas pipe test tube with a length of 154mm. The calibration was achieved using five different acryl plastic rods inserts of 49mm, 48mm, 47mm, 46mm and 45mm with a length of 153mm respectively. The 2-inch (50mm) plexiglass test tube was installed with two pairs of conductivity ring sensors for liquid hold-up and the flush-mounted conductance probe sensor for liquid film thickness. The acts of measuring, recording and transmitting the data to a usable state were achieved using a digital data acquistion system (Labview). The conductivity ring sensors C1 and C2 results which were for the liquid hold-up in the calibration gave R-factors of 0.9962 and 0.9947 respectively, while the conductance probe sensor for the liquid film thickness presented an R-factor of 0.9949.

Evaluation of Wave Characteristics in Annular Flow in Horizontal Pipes

Annular flow experiments in horizontal flow in pipes were conducted with emphasis on wave characteristics (wave velocity, wave frequency) and liquid film thickness. The experiments were conducted using water/air in a 0.0504m pipe diameter with a total flow loop length of 28.68m. Liquid film thickness in all the flow matrix in this study, were observed to be decreasing with increase in gas velocity while increasing with increase in liquid velocity. The decreasing tendency with superficial gas velocity was because of liquid entrainments which were accounted. Pan and Hanratty correlation for liquid entrainment was chosen because it gave the most realistic results among other correlations from the experimental data. Wave velocity and wave frequency were presented to be increasing with increase in superficial gas velocity in annular flow. For wave frequency, it was observed that both superficial liquid and gas velocities have great impact on it. In annular flow in horizontal pipe, it was also observed that the lower the superficial liquid velocity, the lower the amplitude and the higher the wave frequency. This indicates that at low liquid velocity, more ripple waves occurred and at this time more energy were dissipated which resulted to the high frequency observed in this study. However, several correlations where compared with the obtained wave frequency in this study, but [2] preferably matched better as the superficial liquid velocity increases from 0.0903m/s to 0.1851m/s.

Evaluation of Liquid Film Thickness in Gas-Liquid Annular Flow in Horizontal Pipes Using Three Methods

Experimental investigations on annular flow film thickness were conducted using a closed-loop horizontal pipe with an internal diameter of 2-inch (0.0504m). The aim is to progress the understanding of such flow and facilitate the optimum design of hydrocarbon production systems were such flow is encountered. Liquid film thickness was extensively investigated using three methods: the conductance probe sensors installed at the bottom of the pipe, conductivity ring sensors and triangular relationship model. From these methods, liquid film thickness was proven to decrease with increase in superficial gas velocity, while increases with increase in superficial liquid velocity. In comparison, the predicted triangular relationship liquid film thickness matched better with the liquid film thickness obtained from conductance probe sensors at all the flow conditions in the experiments, while the conductivity ring sensor results matched closely at superficial liquid velocity of 0.0505m/s and 0.0714m/s but overestimated at superficial liquid velocity of 0.0903m/s and 0.1851m/s. This has shown the impact of high superficial gas velocity on conductivity ring sensors in accounting for liquid film thickness.

Flow patterns and pressure gradient correlation for oil–water core–annular flow in horizontal pipes

The water-lubricated transportation of heavy oil seems to be an attractive method for crude oil production with significant savings in pumping power. With oil surrounded by water along the pipe, oil–water core–annular flow forms. In this paper, the characteristics of oil–water core–annular flow in a horizontal acrylic pipe were investigated. Plexiglas pipes (internal diameter = 14 mm and length = 7.5 m) and two types of white oil (viscosity = 0.237 and 0.456 Pa·s) were used. Flow patterns were observed with a high-speed camera and rules of flow pattern transition were discussed. A pressure loss model was modified by changing the friction coefficient formula with empirical value added. Totally 224 groups of experimental data were used to evaluate pressure loss theoretical models. It was found the modified model has been improved significantly in terms of precision compared to the original one. With 87.4% of the data fallen within the deviation of ± 15%, the new model performed best among the five models.

Bubble mapping: three-dimensional visualisation of gas–liquid flow regimes using electrical tomography

It is well known that electrical tomography is capable of ‘seeing’ through opaque pipe walls and flow media. However, due to the relatively low spatial resolution, electrical tomograms are ineffective on visualisation of small bubbles or sharp interfaces between large bubbles and the liquid. These limitations give rise to ambiguity in human and/or machine perception of flow dynamics from presenting bubble cluster and blurry boundaries of large bubbles in faint colour or grey. In this paper, a binary approach, called bubble mapping, is proposed to enhance the visibility of flow regime in gas–liquid pipeline flows. With the input gas concentration tomograms reconstructed by an electrical tomography, the method takes the major visual characteristics of typical flow regimes in common recognition as a prior knowledge and replaces the conventional colour mapping with a number of bubbles and their mergence with a thresholding value. With this approach, a stack of cross-sectional tomograms by electrical tomography is transformed and displayed as a collection of individual gas bubbles. The transformation is done with the help of a lookup table indexed by bubble size and an enhanced isosurface algorithm for vivid three-dimensional visualisation. This new approach has been applied to a gas-in-water flow rig and its performance is compared with photo images taken by a high-speed camera. Reasonable agreements have been obtained for common flow regimes including bubbly flow, stratified flow, plug flow, slug flow and annular flow in horizontal pipe and bubbly flow, slug flow and annular flow in vertical pipe. Results evidence the method can provide a photorealistic flow visualisation and therefore enhance the visibility of electrical tomograms for visual identification of flow regime, particularly for opaque media in industrial flows.

Effects of Liquid Velocity on Pressure Gradient, Slip and Interfacial Friction Factor in Annular Flow in Horizontal Pipe

Experimental investigations on annular flow behaviour in two-phase (air/water) flow in horizontal pipe were conducted using 2-inch (0.0504m) with a total length of 28.68m closed loop system. The emphasis from the experiments were on pressure gradient, slip and interfacial friction factor in annular flow. For interfacial friction factor, the entrainment, gas quality, the droplets and slip mixture density values were obtained through the experimental results which were substituted to determine it. In all, effects of liquid velocity were felt, as increase in superficial liquid velocity, increases the interfacial friction factor and pressure gradient in annular flow in horizontal pipes. More so, increase in superficial gas velocity, reduces the interfacial friction factor. Thus, interfacial friction factor decreases with increases in superficial gas velocity, while the pressure gradient increases with increase in superficial liquid velocity. The lower the superficial liquid velocity, the higher the slip but the lower the pressure gradient. Likewise, the lower the superficial liquid velocity, the more ripple waves obtained while the higher the superficial liquid velocity, the more disturbance waves in annular flow in horizontal pipe from the experiments.

Effects of Liquid Velocity on Pressure Gradient, Slip and Interfacial Friction Factor in Annular Flow in Horizontal Pipe

Experimental investigations on annular flow behaviour in two-phase (air/water) flow in horizontal pipe were conducted using 2-inch (0.0504m) with a total length of 28.68m closed loop system. The emphasis from the experiments were on pressure gradient, slip and interfacial friction factor in annular flow. For interfacial friction factor, the entrainment, gas quality, the droplets and slip mixture density values were obtained through the experimental results which were substituted to determine it. In all, effects of liquid velocity were felt, as increase in superficial liquid velocity, increases the interfacial friction factor and pressure gradient in annular flow in horizontal pipes. More so, increase in superficial gas velocity, reduces the interfacial friction factor. Thus, interfacial friction factor decreases with increases in superficial gas velocity, while the pressure gradient increases with increase in superficial liquid velocity. The lower the superficial liquid velocity, the higher the slip but the lower the pressure gradient. Likewise, the lower the superficial liquid velocity, the more ripple waves obtained while the higher the superficial liquid velocity, the more disturbance waves in annular flow in horizontal pipe from the experiments.

Development of droplet entrainment and deposition models for horizontal flow

Abstract Models for the rate of atomization and deposition of droplets for stratified and annular flow in horizontal pipes are presented. The entrained fraction is the result of a balance between the rate of atomization of the liquid layer that is in contact with air and the rate of deposition of droplets. The rate of deposition is strongly affected by gravity in horizontal pipes. The gravitational settling of droplets is influenced by droplet size: heavier droplets deposit more rapidly. Model calculation and simulation results are compared with experimental data from various diameter pipes. Validation for the suggested models was performed by comparing the Safety and Performance Analysis Code for Nuclear Power Plants calculation results with the droplet experimental data obtained in various diameter horizontal pipes.

Full 3D Simulations of Two-Phase Core–Annular Flow in Horizontal Pipe Using Level Set Method

Simulating core---annular flow is an important task in the oil industry. Many attempts have been made to simulate vertical upflow or downflow. However, in the case of horizontal pipes, simulation is likely to succeed when the effect of gravity is ignored, because the motion of the fluid is no longer axisymmetric. This gravity-ignoring simulation is acceptable when the density of oil is almost similar to that of water, but in most cases, density-matching does not occur in reality. A few attempts have been made to simulate flow in horizontal pipes (Ooms et al. in Phys Fluids 25:032102, 2013), but these attempts used 2D cross-sectional simulation or 3D simulation of a specific moment. This paper discusses several results for core---annular flow in horizontal pipes with gravity effect, using full 3D simulation. Using a level set method, we express the interface of core---annular flow and compare different cases with different parameters.

Further Conversation on ‘Correlation of Entrainment for Annular Flow in Horizontal Pipes’, by Pan, L. and Hanratty, T.J., Int. J. Multiphase Flow, 28(3), (2002), pp. 385–408. by A. Al-Sarkhi and C. Sarica

Further Conversation on ‘Correlation of Entrainment for Annular Flow in Horizontal Pipes’, by Pan, L. and Hanratty, T.J., Int. J. Multiphase Flow, 28(3), (2002), pp. 385–408. by A. Al-Sarkhi and C. Sarica

Concentration profiles of droplets and prediction of the transition from stratified to annular flow in horizontal pipes

Concentration profiles of droplets and prediction of the transition from stratified to annular flow in horizontal pipes

Correlation of entrainment for annular flow in horizontal pipes

Two correlations of measurements of entrainment for annular flow in horizontal pipes are presented for liquids with viscosities close to that of water. Entrainment is considered to result from a balance between the rate of atomization of the liquid layer flowing along the pipe wall and the rate of deposition of drops. At low gas velocities, gravitational settling controls the rate of deposition. At high gas velocities, droplet turbulence controls deposition. The first approach uses an empirical relation for entrainment in horizontal pipes at low gas velocities and an empirical relation for entrainment in vertical pipes at high gas velocities. The second uses a theoretical analysis for the rate of deposition that is valid both for high and low gas velocities. Present practice has been to use correlations that have been developed for vertical annular flows. They are faulty because they do not directly include the effects of gravitational settling.

Flow mechanism of two‐phase annular flow

AbstractA mechanism which accounts for the formation and maintenance of two‐phase annular flow in horizontal pipes is proposed and tested experimentally. Time‐average circumferential and axial components of the film velocity were measured.Dispersion of liquid in the circumferential and axial directions and the interchange of droplets between the liquid film and gas core was studied. A pseudo steady state model was derived to describe the dispersion processes.This model was used to predict the distribution of salt downstream from a point source of salt solution located in the annular film. Experimental measurements of salt conntration using an electrical conductivity probe were in cord with values predicted by the model.