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Showing papers on "Slug flow published in 1994"


Journal ArticleDOI
TL;DR: In this article, a four-year experimental study on carbon dioxide (CO2) corrosion of carbon (C) steel in two-phase flow was conducted in a gas and water loop that permitted control and regulation of relevant parameters.
Abstract: Results were presented from a four-year experimental study on carbon dioxide (CO2) corrosion of carbon (C) steel in two-phase flow. Tests were carried out in a gas and water loop that permitted control and regulation of relevant parameters. Flow rates of gas and water were regulated independently to obtain a number of two-phase flow regimes, such as bubble flow and slug flow. In more than 20 long-term experiments lasting from one to several weeks each, pH was varied from 4 to 7 while the temperature was held at 20°C, 40°C, 60°C, and 80°C in different experiments. Corrosion rates were monitored continuously in time with a radiation detection technique. Scanning electron microscopy analysis and x-ray analysis of the specimen surface and cross section were done on selected specimens after each experiment. It was found that, in cases where the formation of protective films is difficult, flow could have a “positive” role by eroding the iron carbide films that otherwise would accelerate corrosion by ga...

89 citations


Journal ArticleDOI
TL;DR: In this paper, a slug-tracking model is proposed that follows the behavior of all individual slugs and is capable of simulating the aforementioned processes in a hilly terrain pipeline, where slugs can be generated at low elbows, dissipate at top elbows and shrink or grow in length as they travel along the pipe.

68 citations


Journal ArticleDOI
TL;DR: In this article, a helically coiled tube (inside diameter, 19.8 mm; coil diameter, 1.17 m; helix angle, 7°27′) with a water-SF6 adiabatic mixture up-flow was measured for total mass flow rates from 500 to 3000 kg s−1 m−2 gas mass fractions.

49 citations


Journal ArticleDOI
TL;DR: In this article, the influence of a second immiscible liquid on gas-liquid slug flow has been investigated, and well-known models for the prediction of the slug frequency and pressure loss, as well as the flow pattern maps of two-phase flow, were extended for this special kind of multiphase flow.

47 citations


Proceedings ArticleDOI
01 Jan 1994

47 citations


Patent
26 Sep 1994
TL;DR: In this article, an apparatus and method for separating the liquid phase and the gas phase of a liquid/gas mixture and for substantially eliminating slug flow is provided, which includes a housing containing a separation table positioned in an inclined position within the housing.
Abstract: An apparatus and method for separating the liquid phase and the gas phase of a liquid/gas mixture and for substantially eliminating slug flow is provided. The apparatus includes a housing containing a separation table positioned in an inclined position within the housing. The liquid/gas mixture flows into the housing through an inlet and spreads over the surface of the separation table. As the mixture spreads over the table, entrained gas is released and the liquid is decelerated. The separated liquid and gas then pass through orifices in the separation table and are separately discharged from the housing. In a second version, a plurality of separation tables may be contained in the housing.

38 citations


Journal ArticleDOI
TL;DR: In this paper, the evolution of finite disturbances is studied by numerical simulations of the wave growth or decay using the method of characteristics, and three basic behaviors are identified: (1) the waves decay with time; (2) the wave amplitude grows until conditions of ill posedness at the wave crest is achieved and (3) the shape of wave is distorted and develops steep slopes that lead to wave break.

36 citations


Book ChapterDOI
TL;DR: In this article, the main results concerning the motion of long bubbles and liquid slugs are reviewed and conservation equations derived based on the assumptions of the unit cell model are derived for gas-liquid slug flow (also known as intermittent flow).
Abstract: This chapter describes gas-liquid slug flow (also known as intermittent flow) Conservation equations are derived based on the assumptions of the unit cell model The main results concerning the motion of long bubbles and liquid slugs are reviewed

30 citations


Journal ArticleDOI
TL;DR: In this article, an experimental study on the dispersed bubble to slug flow transition in a narrow tube is reported, which shows that the superficial liquid velocity is an increasing function of the superficial gas velocity along the transition boundary and that the transition always occurs at an average void fraction of 34%.

28 citations


Journal ArticleDOI
TL;DR: In this article, a flow regime map for the vertical downward air water system is proposed, and three distinguished flow regimes are observed: annular, slug, and bubbly, which are compared quantitatively with two other maps from the available literature.

28 citations


Journal ArticleDOI
TL;DR: In this article, an objective method for determining the flow pattern transition from bubble or plug flow to slug flow was found based on an RMS static pressure measurement. But the transition is accompanied by a clear and abrupt increase in the RMS pressure when plotted as a function of mass quality.
Abstract: Two-phase pressure drop and fluctuating static pressures were measured in a small horizontal rectangular channel (hydraulic diameter = 5.44 mm). The two-phase fluid was an air/water mixture at atmospheric pressure tested over a mass flux range of 50 to 2,000 kg/m[sup 2] [center dot] s. Two-phase flow patterns were identified and an objective method was found for determining the flow pattern transition from bubble or plug flow to slug flow. The method is based on an RMS static pressure measurement. In particular, it is shown that the transition is accompanied by a clear and abrupt increase in the RMS pressure when plotted as a function of mass quality. Use of the RMS pressure as a two-phase flow pattern transition indicator is shown to have advantages over pressure-versus-time trace evaluations reported in the literature. The transition is substantiated by a clear local change in slope in the curve of two-phase pressure drop plotted as a function of either Martinelli parameter of mass quality. For high mass fluxes, the change in slope is distinguished by a local peak. Some degree of substantiation was found in previous work for both of the results (the RMS static pressure change and the local pressure dropmore » change) at the transition to slug flow.« less

Proceedings ArticleDOI
01 Jan 1994

Journal ArticleDOI
TL;DR: An extended two-fluid model that includes bubble cluster formation and breakup was developed and used successfully to predict the bubbly/slug flow regime transition as mentioned in this paper, and it was found that an instability of the void wave associated with the bubble clusters triggered a bubble-slug transition.

Proceedings ArticleDOI
A.K. Vuppu1, W.P. Jepsom1
01 Jan 1994
TL;DR: In this article, a study to determine the corrosion rates and the type of deposits formed on the pipe surface under such multiphase flow conditions is described, and full pipe flow and slug flow conditions and the effect of a few inhibitors are studied.
Abstract: Sweet corrosion in carbon steel pipelines carrying oil-water mixtures has long been a problem in the oil industry. A study to determine the corrosion rates and the type of deposits formed on the pipe surface under such multiphase flow conditions is described. Full pipe flow and slug flow conditions and the effect of a few inhibitors is studied. Temperatures up to 60C and several pressures, flow rates, oil-water fractions are also studied.

Journal ArticleDOI
TL;DR: In this paper, the results of a study of slug flow dynamics in air injected milkline Clean-In-Place (CIP) systems are presented Experimental measurements of slug velocity, slug length, and air admission rate made on 48, 73, and 98 mm ID milklines are presented The air injector must be left open long enough for the slug to travel the entire milkline in order to ensure contact between the slug and all pipe surfaces.
Abstract: The results of a study of slug flow dynamics in air injected milkline Clean-In-Place (CIP) systems are presented Experimental measurements of slug velocity, slug length, and air admission rate made on 48, 73, and 98 mm ID milklines are presented The air injector must be left open long enough for the slug to travel the entire milkline in order to ensure contact between the slug and all pipe surfaces Optimal mechanical cleaning action is produced by slug velocities of 7 to 10 m/s The rate of air admission through the air injector should be controlled to produce superficial air velocity of 8 to 12 m/s to achieve these slug velocities

Journal ArticleDOI
TL;DR: In this paper, a model for estimating void fraction in countercurrent bubbly and slug flows in vertical systems, based on the drift-flux approach, is presented, and the parameter C 0 in the countercurrent bubble flow is 2.0, a value much higher than the generally accepted one of 1.2 for cocurrent flow.

Journal ArticleDOI
TL;DR: In this article, the experimental data of the countercurrent flow limitation for air and water in a bend between a horizontal pipe and a pipe inclined to the horizontal are investigated, and different mechanisms that lead to flooding and that are dependent on the water flow rate are observed.

Journal ArticleDOI
TL;DR: In this article, the propulsion of an isolated slug of liquid along a pipeline by an expanding gas was studied, where a body of liquid accumulates behind a closed valve in a piping system carrying a wet or condensing gas, and that valve is suddenly opened to expose the slug to a high-pressure gas.


Journal ArticleDOI
TL;DR: In this paper, the authors investigated the relations among gas bubble state, static pressure pulsation and flow noise caused by single gas bubble passing through the orifice, and found that the noise level increases twice while the gas bubble passes through an orifice.
Abstract: Presently, in our quest to develop low-noise air conditioning equipment, it is important to reduce the refrigerant flow noise. To date, this problem has been investigated on the basis of trial and error. Fundamental cause and mechanism of the flow noise must be analyzed before a drastic reduction of noise can be achieved. In this study, air-water two-phase flow was used to create a slug flow with single large gas bubble for the purpose of modeling the problem. We investigated the relations among gas bubble state, static pressure pulsation and flow noise caused by single gas bubble passing through the orifice, In the results, it is shown that the noise level increases twice while the gas bubble passes through the orifice and that there exist correlations among flow state, static pressure pulsation and flow noise.

Journal ArticleDOI
TL;DR: In this paper, a model of mass transfer during isothermal gas absorption in the presence of inert gas from a slug rising in a channel filled with liquid is suggested, which employs the approximation of a thin concentration boundary layer.

Journal ArticleDOI
TL;DR: In this article, the results of an experimental study of two-phase flow characteristics in dual-purpose milklines under milking conditions are presented, and the authors provide data for the revision of United States and international standards for sizing milklines in milking machine installations.
Abstract: The results of an experimental study of two-phase flow characteristics in dual-purpose milklines under milking conditions is presented. This project was undertaken to provide data for the revision of United States and international standards for sizing milklines in milking machine installations. The experimental setup and conditions are described. The key performance indicator of stratified flow is that vacuum in the milkline should not fall more than 2 kPa below the receiver vacuum during milking. Design criteria to meet this performance guideline should include milkline diameter and slope as well as expected peak milk flow, and steady and transient air flow rate per slope.


Patent
18 May 1994
TL;DR: In this article, a cyclone separator is used to separate a mixture of gas and liquid, and then the mixture is passed into a siphon to generate a slug or batch of liquid which flows through a flow meter.
Abstract: A multi-phase mixture of gas and liquid is passed into a cyclone separator 2 from which separated liquid is passed into a siphon chamber 6 where it enters the inlet to a siphon tube 7 while separated gas is passed into a line 4 and passes via line 10 to the outlet of the siphon tube 7 through a flap valve 11. Any gas from the siphon chamber 6 is also passed to the line 10 via line 8. As the siphon tube 7 fills with liquid separated gas flows via lines 4, 8 and 10 to the outlet of the siphon tube 7 where it can pass through a flow meter 12 such that the flow rate of the gas phase can be measured. When liquid reaches the top of the siphon tube 7 the siphon operates generating a slug or batch of liquid which flows through flow meter 12. The flap valve 11 is closed by the flow of liquid preventing the flow of gas into the outlet of the siphon tube. The gas now passes into the siphon chamber via line 8 such that the vacuum in the siphon chamber is relieved as the siphon operates. When the liquid in the siphon tube 7 is exhausted the siphon action ceases and a mainly gas flow is once again generated through the flow meter 12 as the siphon tube 7 refills.

Journal ArticleDOI
TL;DR: In this article, the transition to slug flow is predicted by the laws of wave growth in a closed channel and the authors test this proposition by examining the highest waves and the transition of slug flow for air and water, water with surface tension reduced by addition of surface active agents, air with increased viscosity by adding corn syrup and air and ethanol.
Abstract: It has been proposed by the authors that the transition to slug flow depends on the growth of waves in the two-phase flow and thus may be predicted if the laws of wave growth in closed channel are known. In this work, this proposition is tested by examining the highest waves and the transition to slug flow for air and water, air and water with surface tension reduced by addition of surface-active agents, air and water with increased viscosity by addition of corn syrup and air and ethanol. In each case it is found that the predicted transition to slug flow agrees well with experimental data. Neither a lower surface tension nor a higher viscosity has any effect on the transition to slug flow, but the use of surface active agents reduces the wave growth rate and causes the transition to slug flow to shift to higher gas velocities.

Patent
24 Jun 1994
TL;DR: In this article, a steam separator of small gas phase capacity and small size in which a water level is accurately detected and controlled by giving a two phase flow, if a slug flow, good gas liquid separation in a gas phase without causing liquid level change so that a gas-liquid separation pipe provided with a water-level detector has no liquid-level change with the heat of a load heater.
Abstract: PURPOSE:To construct a steam separator of small gas phase capacity and small size in which a water level is accurately detected and controlled by giving a two phase flow, if a slug flow, good gas-liquid separation in a gas phase without causing liquid level change so that a gas-liquid separation pipe provided with a water level detector has no liquid level change with the heat of a load heater. CONSTITUTION:A gas-liquid two phase flow, which runs while collecting reactive heat given from a CO transformer to transform carbon monoxide in reformed gas through reaction in a reformer and from a fuel cell stack to provide electric power by using reformed gas therethrough, is given gas-liquid separation by collision with the inside wall of a gas-liquid separation pipe 3A1 in a steam separator 3A, the gas-liquid separation is completed in a gas-liquid separation pipe 3A2, and steam required for the reformer and pressure water required to cool the CO transformer 1 and the fuel cell stack 2 are obtained. The gas- liquid separation pipe 3A1 is provided with a load heater 10 which consumes high power during low load and the gas-liquid separation pipe 3A2 is provided with a water level detector 7 which detects a pressure water level to keep the level constant by using a water supply pump 8.

Journal ArticleDOI
TL;DR: In this article, a transient two-fluid model has been used to develop a general relation for acoustic waves over the whole void fraction region, where flow pattern transitions from one flow regime to the other are assumed to occur at certain void fractions.
Abstract: The transient two-fluid model has been used to develop a general relation for acoustic waves. The analysis is valid in principle over the whole void fraction region. Flow pattern transitions from one flow regime to the other are assumed to occur at certain void fractions. Different correlations are used to calculate the interfacial area and interfacial drag force per unit mixture volume for bubbly flow, slug flow and annular flow respectively. The vapour-liquid interphase heat flux is derived from the one dimensional Fourier heat conduction equation to evaluate the interphase evaporation or condensation rate. Based on the present theory, a program has been carried out. Calculations are performed for pressure from 0.07 MPa to 16.0 MPa, void fractions from 0.0 to 1.0. The predicted sound speeds are compared with some experimental data for low pressures, good agreement has been achieved between sound speed predictions and experimental data.

Journal ArticleDOI
TL;DR: In this paper, an experimental investigation has been made on the flow separation characteristics of an air-warer two-phase slug flow into three successive capillary tubes with T-junctions.
Abstract: An experimental investigation has been made on the flow separation characteristics of an air-warer two-phase slug flow into three successive capillary tubes with T-junctions. The flow pattern in the main tube just upstream of the branches was mostly limited to the slug flow in the present experiments. It was clarified that uneven separation of both phases among the three branches became large with decrease of flow rate at the outlet main tube. It was also clarified that the time ratio of the existence of water at the entrance of the branches was the dominant factor controlling the distribution characteristics of two-phase mixture into the branches. In some flow conditions. The slug flow and the annular flow were observed to alternatively change with time.

01 Jan 1994
TL;DR: When gas and liquid flow in a pipe, the interface between the phases may take a variety ofdifferent patterns, the most fascinating and misunderstood being probably slug flow as mentioned in this paper, it is of interest for many practical problems involving flow instabilities and transientbehaviour.
Abstract: When gas and liquid flow in a pipe the interface between the phases may take a variety ofdifferent patterns, the most fascinating and misunderstood being probably slug flow. Asthis kind of flow occurs over a very wide range of intermediate flow rates of gas andliquid, it is of interest for many practical problems involving flow instabilities and transientbehaviour.