Experimental Study of Two-Phase Normal Slug Flow in a Pipeline-Riser Pipe System

1981 ◽  
Vol 103 (1) ◽  
pp. 67-75 ◽  
Author(s):  
Zˇ. Schmidt ◽  
J. P. Brill ◽  
H. D. Beggs
Keyword(s):  
Experimental Study ◽  
Slug Flow ◽  
Production Facility ◽  
Two Phase ◽  
Flow Rates ◽  
Pipe System ◽  
Void Fractions ◽  
Riser Pipe ◽  
Measured Flow ◽  
Phase Normal

Slug flow was studied with air-kerosene flow in a 2-in. pipeline-riser pipe system consisting of a 100-ft pipeline and a 50-ft vertical riser. Pipeline inclinations of ± 5 deg, −2 deg, and horizontal were used. Pressures, flow rates, flow patterns and void fractions were measured. Flow pattern maps were developed and normal slug flow was modeled, permitting prediction of variables necessary to consider when designing a production facility operating under normal slug flow.

Severe Slugging in Offshore Pipeline Riser-Pipe Systems

1985 ◽  
Vol 25 (01) ◽  
pp. 27-38 ◽  
Author(s):  
Zelimir Schmidt ◽  
Dale R. Doty ◽  
Kunal Dutta-Roy
Keyword(s):  
Slug Flow ◽  
Offshore Platforms ◽  
Liquid Slug ◽  
Two Phase ◽  
Pipe System ◽  
Flow Capacity ◽  
Riser Pipe ◽  
Offshore Pipeline ◽  
Carry Over ◽  
The Cost

Abstract Severe slug flow (i.e., terrain-dominated slug flow) was studied in a simulated offshore pipeline riser-pipe system. Severe slug flow is characterized by extremely long liquid slugs generated at the base of the vertical riser. This phenomenon occurs at low gas and liquid flow rates and for negative pipeline inclinations. Slugging in some offshore platforms has required the use of operating procedures that drastically curtail production. Losses in flow capacity up to 50% have been reported. production. Losses in flow capacity up to 50% have been reported. A hydrodynamic model has been developed for severe slug flow. The model's predictions agree with experimental data. The model can be used to design predictions agree with experimental data. The model can be used to design new pipeline riser-pipe systems or to adjust the operation of existing systems to prevent the occurrence of severe slug flow. Also, a flow-regime map is presented for predicting the severe slug flow regime, where the boundaries are determined analytically. Finally, additional methods are proposed to prevent the flooding of separation facilities by riser-pipe proposed to prevent the flooding of separation facilities by riser-pipe generated slugs. This study is an extension of Ref. 1, in which severe slug flow was introduced and was only partially modeled. Introduction Two-phase flow in pipelines frequently involves the formation of liquid slugs. Processing of these slugs with separators can be extremely difficult if the size of the slugs becomes abnormally long. When a long liquid slug reaches a separator, it is possible for the liquid level in the separator to rise faster than the separator can purge the liquid, resulting in possible liquid carry-over into the gas stream. A technique often used for possible liquid carry-over into the gas stream. A technique often used for protecting separators from liquid slugs is to install an additional vessel protecting separators from liquid slugs is to install an additional vessel ahead of the separator, which usually is called a "slug catcher." The combined cost of the two smaller vessels is usually lower than the cost of a single large separator, which must be designed to process liquid slugs. However, the size of the slug catcher and/or separator must increase with increasing expected liquid slug sizes. The cost of installation of large separators and slug catchers, especially in the hostile environments found in Alaska, in swamps, or on offshore platforms, may be prohibitive. Therefore, it is desirable to have a technique that can predict and control both the occurrence and magnitude of liquid slugs so that separation facilities can be designed properly and their size decreased. Recently, studies have been performed that have increased dramatically the accuracy of both slug size and frequency predictions. Earlier studies, performed under laboratory conditions, indicated that slug lengths would performed under laboratory conditions, indicated that slug lengths would be no more than 100 ft [30.48 m]. However, recent studies performed on full-scale pipelines have indicated that slug lengths of more than 2,000 ft [609.6 m] are possible. In addition, it has been discovered that slug flow can be generated by several different mechanisms, each producing liquid slugs with different physical properties. Schmidt et al., in studying slug flow in a simulated offshore pipeline riser-pipe system, found two distinct slug flow patterns: normal (e.g., hydrodynamic) and severe (e.g., terrain-dominated) slug flow. Severe slug flow is characterized by the generation of liquid slugs at the base of the riser pipe, with the remainder of the pipeline in stratified flow. Normal slug flow is characterized by many liquid slugs being generated along the length of the pipeline and occurs at higher gas and liquid flow rates. The liquid slugs generated during severe slug flow were found to range in length from one to several riser-pipe heights, which, at the time this study was performed, generally exceeded the slug lengths associated with normal slug flow. Therefore, riser-pipe-generated slug flow was designated "severe" slug flow, in comparison to "normal" pipeline-generated slug flow. Severe slug flow was found to depend on the geometry of the pipeline riser-pipe system. The pipeline must be in stratified flow, as well as inclined negatively for the liquid slug to be generated at the base of the riser. Also, because of the mechanism by which severe slugs are generated, it was found that the degree of slug aeration for severe slugs was much lower than that associated with normal slug flow. Also, the study showed that the phenomena of severe and normal slug flow are mutually exclusive because normal pipeline slugs and bubbles will flow through the riser pipe nearly unchanged, excluding the possibility of a riser-generated slug. Finally, a hydrodynamic model was developed for severe slug flow. The model was formulated on basic physical principles and was limited to a description of how the liquid slug is generated at the base of the riser pipe. No attempt was made to model the full behavior of the severe slug pipe. No attempt was made to model the full behavior of the severe slug flow cycle. Bendiksen et al. developed a dynamic one-dimensional two-phase flow model for the Norwegian state oil company, Statoil. They gave the mass and momentum conservation equations for each phase, and solved them numerically by using finite difference techniques. SPEJ P. 27

Experimental Study of Severe Slugging in a Two-Phase-Flow Pipeline - Riser Pipe System

1980 ◽  
Vol 20 (05) ◽  
pp. 407-414 ◽  
Author(s):  
Z. Schmidt ◽  
J.P. Brill ◽  
H.D. Beggs
Keyword(s):  
Flow Pattern ◽  
Flow Rate ◽  
Liquid Flow ◽  
Test Section ◽  
Slug Flow ◽  
Pressure Fluctuations ◽  
Phase Flow ◽  
Two Phase ◽  
Pipe System ◽  
Riser Pipe

Abstract Slug flow was studied in a simulated, offshore, pipeline-riser pipe system. Two distinct slug flow patterns were identified: severe slugging and normal slug flow. Severe slugging, characterized by generation of slugs ranging in length from one to several riser pipe heights, occurs at low gas and liquid flow rates and for negative pipeline inclinations. A mathematical model was developed for severe slugging. Results agree well with experimental data. Choking was found to be an effective method of eliminating severe slugging. Introduction Gas and liquid frequently are transported simultaneously in pipes, such as in gas and oil fields, in refineries and process plants, and in steam injection and geothermal production systems. When two-phase flow occurs in a pipeline, the phases separate in the pipe into various flow patterns.When the flow pattern at the exit of a pipe consists of alternating slugs of gas and liquid, special operating procedures frequently are required.Slugging in some of these facilities has required the use of operating procedures which drastically curtail production. Yocum reported that flow capacity reductions up to 50% have been necessary to minimize slugging on offshore platforms. The reported losses occur when platform backpressure is increased until a flow regime is reached in which slugging and pressure fluctuations are reduced to levels which can be handled by gathering facilities.Cady used an existing vertical flow pattern map to determine the conditions under which slugging would occur in a riser. Schmidt et al. described a comprehensive review of slugging problems of this nature and proposed automatic choking as a means of alleviating slugging in risers.This study describes the generating of long liquid slugs in a pipeline-riser pipe system and develops a mathematical method to predict slug characteristics. In addition, it has been found that severe slug flow can be eliminated or minimized by careful choking which results in little or no change in either flow rate or pipeline pressure and in elimination of pressure fluctuations. Description of Equipment An experimental facility was designed and constructed to permit study of flow in a pipeline-riser pipe system. The fluids flowed through a 100-ft-long, 2-in.-diameter pipeline and then up a 50-ft-long, 2-in.-diameter vertical riser. All pipe was made of Lexan and was transparent. Both sections are supported by aluminum I-beams that can be pivoted at their free ends through angles of +/- 5 degrees, to the horizontal and vertical. This study was conducted at pipeline angles of −5, −2, 0, and +5 degrees, with the riser pipe vertical.The fluids used in the study, air and kerosene, were mixed at the entrance of the test section, At the end of the test section, the air/kerosene mixture was separated in a horizontal separator. The air was vented, and the kerosene was returned to a storage tank.Kerosene was pumped from the tank into the system by means of a single-stage Gould centrifugal pump. The liquid flow rate was metered with a Camco 4-in, orifice meter and a Brooks rotameter.The air was obtained from a Joy two-stage compressor with a maximum output capacity of 0.6 MMscf/D at 120 psig. A Camco 2-in. orifice meter and a 0.75-in. Daniel orifice meter were used to measure the air flow rates.On each test section there were two pressure taps separated by a 25-ft span. SPEJ P. 407＾

Development of an Efficient Phase Separator for Space and Ground Applications

2016 ◽  
Author(s):  
Xiongjun Wu ◽  
Greg Loraine ◽  
Chao-Tsung Hsiao ◽  
Georges L. Chahine
Keyword(s):  
Swirling Flow ◽  
Flow Behavior ◽  
Space Station ◽  
Low Flow ◽  
Design Parameters ◽  
Two Phase ◽  
Flow Rates ◽  
Void Fractions ◽  
Wide Range ◽  
Phase Separator

The limited amount of liquids and gases that can be carried to space makes it imperative to recycle and reuse these fluids for extended human operations. During recycling processes gas and liquid phases are often intermixed. In the absence of gravity, separating gases from liquids is challenging due to the absence of buoyancy. This paper discusses a phase separator that is capable of efficiently and reliably separating gas-liquid mixtures of both high and low void fractions in a wide range of flow rates that is applicable to reduced and zero gravity environments. The phase separator consists of two concentric cylindrical chambers. The fluid introduced in the space between the two cylinders enters the inner cylinder through tangential slots and generates a high intensity swirling flow. The geometric configuration is selected to make the vortex swirl intense enough to lead to early cavitation which forms a cylindrical vaporous core at the axis even at low flow rates. Taking advantage of swirl and cavitation, the phase separator can force gas out of the liquid into the central core of the vortex even at low void fraction. Gas is extracted from one end of the cylinder axial region and liquid is extracted from the other end. The phase separator has successfully demonstrated its capability to reduce mixture void fractions down to 10−8 and to accommodate incoming mixture gas volume fractions as high as 35% in both earth and reduced gravity flight tests. The phase separator is on track to be tested by NASA on the International Space Station (ISS). Additionally, the phase separator design exhibits excellent scalability. Phase separators of different dimensions, with inlet liquid flow rates that range from a couple of GPMs to a few tens of GPMs, have been built and tested successfully in the presence and absence of the gravity. Extensive ground experiments have been conducted to study the effects of main design parameters on the performance of the phase separator, such as the length and diameter of the inner cylinder; the size, location, and layout of injection slots and exit orifices, etc., on the swirling flow behavior, and on the gas extraction performance. In parallel, numerical simulations, utilizing a two-phase Navier-Stokes flow solver coupled with bubble dynamics, have been conducted extensively to facilitate the development of the phase separator. These simulations have enabled us to better understand the physics behind the phase separation and provided guideline for system parts optimization. This paper describes our efforts in developing the passive phase separator for both space and ground applications.

An Experimental Study on Air-Water Two-Phase Flow Patterns in Pebble Beds

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
Bai Bofeng ◽  
Liu Maolong ◽  
Su Wang ◽  
Zhang Xiaojie
Keyword(s):  
Experimental Study ◽  
Flow Pattern ◽  
Test Section ◽  
Slug Flow ◽  
Annular Flow ◽  
Two Phase Flow ◽  
Flow Patterns ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Pattern Transition

An experimental study was conducted on the air-water two-phase flow patterns in the bed of rectangular cross sections containing spheres of regular distribution. Three kinds of glass spheres with different diameters (3 mm, 6 mm, and 8 mm) were used for the establishment of the test section. By means of visual observations of the two-phase flow through the test section, it was discovered that five different flow patterns occurred within the experimental parameter ranges, namely, bubbly flow, bubbly-slug flow, slug flow, slug-annular flow, and annular flow. A correlation for the bubble and slug diameter in the packed beds was proposed, which was an extended expression of the Tung/Dhir model, Jamialahmadi’s model, and Schmidt’s model. Three correlations were proposed to calculate the void friction of the flow pattern transition in bubble flow, slug flow, and annular flow based on the bubble model in the pore region. The experimental result showed that the modified Tung and Dhir model of the flow pattern transition was in better agreement with the experimental data compared with Tung and Dhir’s model.

EXPERIMENTAL STUDY OF TWO-PHASE GAS-LIQUID SLUG FLOW WITH A SLIGHT DIRECTION CHANGE

2015 ◽  
Author(s):  
Rafael Fabricio Alves ◽  
Andressa Carolinne Del Monego ◽  
Cristiane Cozin ◽  
Fausto Arinos de Almeida Barbuto ◽  
Fábio Alencar Schneider ◽  
...  
Keyword(s):  
Experimental Study ◽  
Slug Flow ◽  
Liquid Slug ◽  
Two Phase ◽  
Direction Change

Experimental study of the characteristics of an upward two-phase slug flow in a vertical pipe

2018 ◽  
Vol 108 ◽  
pp. 428-437 ◽  
Author(s):  
Faiza Saidj ◽  
Abbas Hasan ◽  
Hiba Bouyahiaoui ◽  
Ammar Zeghloul ◽  
Abdelwahid Azzi
Keyword(s):  
Experimental Study ◽  
Slug Flow ◽  
Vertical Pipe ◽  
Two Phase

Experimental study and CFD modelling of a two-phase slug flow for an airlift tubular membrane

2009 ◽  
Vol 64 (16) ◽  
pp. 3576-3584 ◽  
Author(s):  
N. Ratkovich ◽  
C.C.V. Chan ◽  
P.R. Berube ◽  
I. Nopens
Keyword(s):  
Experimental Study ◽  
Slug Flow ◽  
Cfd Modelling ◽  
Two Phase ◽  
Tubular Membrane

Size Effect on Adiabatic Gas-Liquid Two-Phase Flow Map and Void Fraction in Micro-Channels

2006 ◽  
Author(s):  
Renqiang Xiong ◽  
J. N. Chung
Keyword(s):  
Linear Relationship ◽  
Flow Regime ◽  
Slug Flow ◽  
Phase Flow ◽  
Micro Channel ◽  
Two Phase ◽  
Void Fractions ◽  
Micro Channels ◽  
Mini Channels ◽  
Churn Flow

Adiabatic gas-liquid two-phase flow patterns and void fractions in micro-channels were experimentally investigated. Using nitrogen gas and water, experiments were conducted in near-square micro-channels with hydraulic diameters of 0.209mm, 0.412mm and 0.622 mm, respectively. The main objective was focused on the effects of micro-scale channel sizes. Gas and liquid superficial velocities were varied from 0.06-72.3 m/s and 0.02-7.13 m/s, respectively. Four defined flow patterns including bubbly-slug flow, slug-ring flow, dispersed-churn flow and annular flow were observed in both micro-channels of 0.412 mm and, 0.622 mm in hydraulic diameter. In the micro-channel of 0.209 mm, the bubbly-slug flow turned into the slug-flow and the dispersed-churn flow was not observed. The current flow regime maps showed that the transition lines shifted towards higher gas superficial velocity due to the stronger surface tension effect as the channel size was reduced. The micro-channel flow regime maps were found to be quite different from those of mini-channels. Measured time-averaged void fractions in our micro-channels held a non-linear relationship with the homogeneous void fraction as oppose to the relatively linear trend for the mini-channels. A new correlation was proposed to predict the non-linear relationship that fits most of the experimental data of the current three micro-channels and those of the 0.1 mm diameter tube reported by Kawahara et al. within ± 15%.

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