A slack flow model with moving regime boundaries onepetro. Notes on twophase flow, boiling heat transfer, and boiling. The measurement is used to calculate dryness fraction, void fraction, and possibly flow rate in the pipe, and should be independent of temperature. He also selects a mean flow velocity of 2 fps for the test. Shashi menon, in transmission pipeline calculations and simulations manual, 2015. The method can provide continual monitoring and be installed into piping in areas of limited pipe runs. Mist flow is a flow regime of twophase gasliquid flow. Pressure drop during twophase flow of refrigerants in.
In order to analyze the motion characteristics of slack line flow, this study divides the control volume in stratified flow into several sections, and then carries out a mechanical analysis of the. Sensitivity study for leak detection in slack line conditions. Pressure drop during two phase flow of refrigerants in horizontal smooth tubes a. Nov 06, 2018 the segment of interest is located in an area where the pipeline is normally operated with vapor present slack line flow conditions due to the large change in elevation. Gasliquid two phase flow simulation in spipe youtube. In the appendix a of the api rp 14e two other criteria are also mentioned for sizing flow line piping. Identify two phase separated flow regimes in horizontal and vertical pipe flows.
Eq1718, section 17, gpsa engineering data book, eleventh edition, 1998 where. The effects of reattaching and detaching of flow lines, which are common in pipelines, are considered in this study. Hydraulic transients induced by pigging operation in pipeline. It corresponds to the level that water would reach in a vertical pipe connected to the pipeline. Fluidflow is easytouse and equips you with all the tools needed to design or analyze safe, reliable and energy efficient pipe flow systems. Two phase pressure drop across a straight test pipe was experimentally determined for reynolds number re steam flow of a flow quality of 0. Laminar flow is characterized by little mixing of the flowing fluid and a parabolic velocity profile. This video contains designing of the domain,discretization,and simulation of the result. Modeling slack flow in hydraulic pipelines by means of a consistent. Online, continuous, twophase flow measurement is often necessary, particularly in the oil and gas industry.
All these flow regimes may occur in a horizontal pipe flow. Many phenomena in pipeline operations exhibit two phase characteristics, such as slack line, liquid formation, wet gas operation, separation processes, etc. Twophase flow in vertical line pipelines, piping and fluid. Slack line flow occurs only during abnormal pipeline operations. The size distribution of the dispersed droplets is important because it has a very significant effect upon flow conditions mixture viscosity, pressure drop and equipment performance, such as in liquidliquid contactors or phase separators. Study improves control of slack line flow request pdf. Review of the api rp 14e erosional velocity equation. Mar 02, 2017 besides this, the pressure drop in a two phase flow can be up to 10 times higher than the single phase flow coker, 2007. Liquid pipelines through mountainous terrain often experience slack flow. Actually, the terms two component flow and twophase flow are often used rather loosely in the literature to mean liquidgas flow and liquidvapor flow respectively. A study on the causes and the treatment measures of slack line.
Validating a singlephase flow pipeline simulation model. Before steady flow was achieved, due to this compression, no product arrived to the destination for around 30 minutes. Three phase flows of gas and two liquid phases often occur during production of oil. The techniques most commonly used in the design of two phase flow pipeline can be classified into three categories. The prediction capabilities of existing flow regime maps were shown to be inadequate. Slack line flow behavior is of interest to pipeline operators for a number of reasons. The transient involves starting the pipeline at tight line conditions. Route optimization of pipeline in gasliquid twophase.
In order to access the capability of the model to properly describe the slack line flow, a numerical example is presented for an airwater mixture flowing in a simple pipeline arrangement made of two segments of straight pipes which go sequentially uphill and downhill. The actual flow regime will depend on fluid velocities and properties. The transportation of oil and its derivatives are mostly conducted through pipelines that connect production fa. Liquid free surface an overview sciencedirect topics. Two phase flow is a difficult problem as there are many variables.
As long as two phase flow exists in the pipeline, the pipeline is defined as two phase pipeline. His research activities include complex fluid flow, rheology, viscoelastic fluids, turbulent drag reduction, heat and mass transfer, emergency relief design, multi phase flow, and electrochemical engineering. Figure 2 vapor in the high points of the pipeline slack line flow. The large cavity of water vapor and air was in the downslope pipe following the peak and slack line flow that exited for a long period of time. Application of local instant formulation to two phase flow problems 46 1. In the present work, a flow induced vibration analysis fiv is performed on a horizontal pipe that transports waterair two phase flow. As oil is extracted from the reservoir, the formation water beneath may flow into the well, due to its easier motion through the rock pores. Pressure data that was recorded by the pipelines data acquisition system indicated a pressure surge occurred when the line was restarted. Enthalpy and mass flowrate measurements for twophase. There are situations in which are economically advantageous to transport both a gas and a liquid in a single pipeline simultaneously.
This paper will outline the two phase model used on the transalaska pipeline and provide comparisons to slack he data provided by the alyeska pipeline service company. Twophase saline water containing 2 % by volume silica at 30 c is considered as the studied fluid. In this article, we describe some of the commercially most important techniques for gasliquid, gassolid, liquidsolid, and liquidliquid flows, and provide associated illustrative sketches and regime maps. Twophase annular flow prevails throughout the length of the tube, but. Argonwater is an instance of two phase two component flow. Electrical capacitance tomography ect is a novel technology that can deal with the complexity of two phase gasoil flow measurement by explicitly deriving the component distributions on two adjacent planes along a pipeline. Flow quality flow rate flow regime low low and intermediate bubbly high dispersed bubbly. Modeling and simulation of erosioncorrosion in disturbed two. A study on the causes and the treatment measures of slack. If he needs a test section of 10 ft of fully developed flow, what should be the minimum. An appropriate starting point is a phenomenological description of the geometric distributions or. To get a better picture of this flow phenomenon, it is worthwhile to report to the modified piezometric head h. In this study, an attempt has been made to analyze two serious.
In batched pipelines, slack line flow will cause intermingling of batches, which. Request pdf study improves control of slack line flow new research has improved control of slack line flow slf in steep slope liquids pipelines, whether. Depending upon the flow regime, the liquid in a two phase flow system can be accelerated to velocities approaching or exceeding vapour velocities. Benzene, kerosene, water and various kinds of 1 oils were used as the test liquids while air was used as the gas phase.
Consider liquid, gas, two phase, slurry or nonnewtonian fluids from a single solution. Pigging in pipelines basically performs operations for five reasons including cleaning the pipe interior, batching or separating dissimilar products, displacement, measurement, and internal inspection. Abstract to explore the problem of the slack flow and waterhead having a huge impact on the. As pressure changes occur within a throttling valve, it is possible to produce 2phase flow at the valves outlet for either a liquid or gasvapor at the inlet. Q flow rate of gas, m3day at standard conditions ts standard temperature 288. In order to validate the developed model, the predicted results are compared with experimental data in a practical geometry. In some cases these velocities are higher than desirable for a process piping system. The guideline states that flow lines, production manifolds, process headers and other lines transporting gas and liquid in two phase flow should be sized primarily based on flow. Slack line formation is a twophase phenomenon in the actual pipeline. Improving operational safety in oil pipelines pipeline technology. Study improves control of slack line flow pipeline transport scribd. Within each of these groups are subcategories that are based on the general characteristics of the. Types of phase flows and gas liquid system piping guide.
Airwater is an example of two phase multi component flow. Twophase flow involving phase change between the liquid and vapor phases of a single substance is of particular interest to the heat transfer community and to practicing engineers. Abstract many phenomena in pipeline operations exhibit two phase characteristics, such as slack line, liquid formation, wet gas operation. Based on the analysis, the equations of the gasliquid twophase volume and. Depending upon the flow regime, the liquid in a twophase flow system can be accelerated to velocities approaching or exceeding vapour velocities. These techniques involve venturi pressure drop, coriolis. The piezometric line allows visualizing the evolution of the water pressure all along the pipelines. Slack line regions significantly change the hydraulics of the pipeline operations. Two phase flow analysis of water and air, it is a two dimensional analysis.
Module 2 principles and sizing of a gravity fed pipeline. Water fractions in the output stream increase materially during the producing life of a well and many wells exist from which economic production can still persist with water volume fractions in the liquid phase in excess of 90%. Frictional pressure drop estimation of twophase gasliquid. Let us have a look at what these differences mean in practice. The first step is to gather important fluid properties for both phases. Introduction gas liquid two phase flow in pipes is a common occurrence in the petroleum industry production and transportation of oil and gas. A model has been proposed for the dynamic simulation of the pigging process after water pressure testing in a long slope pipeline. Take a total system design approach with the most comprehensive and easy to use pipe flow software available. Twophase gasliquid pipe flow and relief sizing aiche. Frictional pressure drop is calculated for dispersed, annular, stratified and slug flow patterns. A method for the measurement of two phase flow has been tested, with the ability to provide continual monitoring of two phase flow in geothermal or other pipelines. Drag force acting on a spherical particle in a very slow stream 46 1. For transmission pipelines, slack line operations are usually connected with very large elevation changes and associated pipeline design limitations. An example of the second case is seen in a geothermal well, where water boils which in turn increases the amount of steam in the pipe.
Theoretical evaluation of twophase flow in a horizontal. External boundary conditions and contact angle 43 1. Thus we recognize that there is a complicated two way coupling between the. Experiments and modelling of twophase transient flow during. This webinar covers methods for identifying flow regimes and determining friction loss in two phase distributed and homogeneous gasliquid pipe flows and sizing relief valves for frozen and flashing homogeneous two phase flow. Numerical analysis of two phase flow patterns in vertical. Project standards and specifications piping systems rev01. Schneider electrics simsuite pipeline is a highly accurate, realtime, twophase rttm targeting liquid pipelines that transport any fluid composition and accurately handle twophase flow, drag reducing agent dra injections, shutin monitoring, and pipeline transients. Flow model and thermophysical properties the flow in the tube is modelled as onedimensional single or two phase flow where there is a strong coupling between the gas and the liquid, such that they travel at a common velocity.
In an oilgas mixture transportation pipeline, the oilgas ratio may vary a lot in different parts. The testing described was been performed in order to reduce uncertainties associated with the effects of two. Figure 1 vapor in the high points of the pipeline no flow figure 2 vapor in the high points of the pipeline slack line flow because of this situation, every time operation began, part of the vapor started to get compressed and changed into liquid phase. It is also commonly called slackline flow, column separation, and vapor pockets. Electrical capacitance tomography twophase oilgas pipe.
Modeling of two phase flow and slug flow characteristics in horizontalinclined pipelines using cfd, conference paper pdf available october 2007 with 779 reads how we measure reads. Figure 2 vapor in the high points of the pipeline slack line flow because of this situation, every time operation began, part of the vapor started to get compressed and changed into liquid phase. Twophase flow in pipelines and heat exchangers duncan. Two phase flow in vertical line katmar chemical 11 jun 08. Coffield 1999 investigated two phase flow pressure drop of high quality steam. Line sizing and pressure drop calculation for two phase fluid flowing through a horizontal pipe. The measured two phase heattransfer coefficients varied by a factor of approximately, the two phase frictional pressure drop ranged from small negative values in slug flow to.
Studies of three phase oilwatergas flow in pipelines. Hydraulic transients induced by pigging operation in. Fluid flow is classified into two basic fluid states at the inlet. Study on oilwater twophase flow in horizontal pipelines. Modeling slack flow in hydraulic pipelines by means of a. Two phase flow in pipeline simulation slack line condition in. The correlation is based on 11 2 pressure profiles cons isting of 960 field measured pressure losses 340 tests for horizontal, 500 for vertical and 120 for. A typical oil and gas reservoir contains gas, oil and water. The chemical tracer flow test tft technique for two phase mass flow rate measurement has been in use since 1992 and is now employed routinely in the major geothermal fields of. The higher pipeline size is preferred to lower down pressure drop and thus to achieve higher available npsh at pump suction port. Pdf liquid holdup correlation for horizontal, vertical. Besides, this paper analyzes the phenomenon of slack line flow from the perspectives of thermodynamics, structural mechanics and fluid mechanics. Product pipeline with large elevation changes and prominent slack flow.
Two phase flow in pipelines and heat exchangers chisholm, d on. The purpose of this study is to simulate two phase gasliquid flow using cfd models for 2d and 3d in smooth and rough pipes. Pdf oilwater twophase flow characteristics in horizontal. Gasliquid twophase flow develops in pipe sections caught in the slack condition. Twophase flow, which involves fluid flow of a mixture of two phases, can be 1 liquidvapor flow, 2 liquidliquid, 3 liquidsolid particles, and 4 gassolid particles. Two phase flow in pipeline simulation slack line condition in transalaska crude oil pipeline. One of the earliest studies in two phase airwater flow was conducted by. He selects a 1inchdiameter pipe and uses a glycerinwater mixture as the fluid, which has a kinematics viscosity equal to i04 ft2s. Twophase cocurrent flow in inclined pipe sciencedirect.
On one, slack line flow existed almost all of the time. Oil and gas pipeline design, maintenance and repair. The simultaneous flow of oil and water in pipelines is a common occurrence in the petroleum industry. It occurs at very high flow rates and very high flow quality. Pressures in the pipeline are then reduced to create slack line conditions. If we draw the pressure line during the flow, we obtain the dynamic head profile dynamic piezometric level. The quality is determined as a function of pressure by an energy balance on the fluid along the flow path. Such high velocities can cause a phenomenon known as erosion corrosion in equipment and piping systems. The authors classified two phase flow observations. Request pdf studies of three phase oilwatergas flow in pipelines the prediction of three phase gasliquidliquid flows is of central importance. This conditions causes, that liquid film flowing on the channel wall is thinned by the shear of the gas core on the interface until it becomes unstable and is destroyed. The engineers developed the terminology rather than the chemists.
In drainage pipes of oilgas separators, the flowing liquid is basically crude oil, but along the pressure drop some dissolved gas would come out. Request pdf modeling slack flow in hydraulic pipelines by means of a consistent thermodynamic. Pdf two phase flow induced vibration analysis in an. Source terms from twophase flow in long pipelines following. In the study, a fluidstructure interaction transient model. Edwards, methodology for sizing relief valves for twophase gasliquid flow, proceedings of the process plant. It includes the traditional simplified and mechanistic models, moreover, principles of the drift flux model and the. The subscripts g and f indicate the vapor and liquid phase at saturation, respectively. Volumes international pipeline conference american. It used by engineers in over 75 countries worldwide, to model pipe systems where the flow rates, pressure losses, and pumping requirements of the system need to be calculated. Frictional head loss in slack regions is much greater than in tight line regions.
Accurate prediction of the flow pattern, pressure drop and liquid holdup is imperative. Route optimization of pipeline in gasliquid twophase flow. If we draw the pressure line during the flow, we obtain the dynamic head profile dynamic piezometric. New research has improved control of slack line flow slf in steep slope liquids pipelines, whether during commissioning, steady operations, or in the wake of an accident. There are two basic flow regimes for flow of a single phase fluid. To start the test, a manual valve was controlled at the delivery station in order to. The model proposed for the pigging process was employed to understand the flow dynamics in the pipeline and to obtain transient pressures for the two accidents and the field trial. In addition, full equilibrium in pressure, temperature and chemical potential is assumed.
Pipe flow expert user guide pipe flow software for pipe. Notes on twophase flow, boiling heat transfer, and. Slack line flow occurs occasionally during normal pipeline operations. Similarly in other pipelines, the pressure drop due to sudden change in the flow direction or the reduction of the line size, hot liquid vaporization takes place which generates vapor bubbles inside the pipeline.
Experiences installing real time simulation software on a number of liquid pipelines over the last 15 years have included the following. This can happen when pressure drops at constant enthalpy and water boils to form steam. The simplest way to classify pipe flow models is probably by specifying how many separate fluids they can deal with simultaneously single phase, two phase or three phase, and by whether they are able to describe timedependent phenomena transient or purely steadystate. Two phase flow in pipeline simulation slack line condition. Making a bladeless wooden fan scrapwood challenge ep38 duration. Project standards and specifications piping systems. Engineering data book iii two phase pressure drops 4. The complexity of this twoway coupling presents a major challenge in the study of multiphase.
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