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Journal ArticleDOI: 10.1115/1.2795032

The Study of Dynamic Slug Flow Characteristics Using Digital Image Analysis—Part I: Flow Visualization

01 Jun 1998-Journal of Energy Resources Technology-transactions of The Asme (American Society of Mechanical Engineers)-Vol. 120, Iss: 2, pp 97-101
Abstract: This paper reports the application of novel, digital image analysis techniques in the study of slug flow characteristics, under dynamic conditions in two-phase gas-liquid mixtures. Water and an oil of viscosity 18 cP were used for the liquid phase and carbon dioxide was used for the gas phase. Flow in a 75-mm i.d., 10-m long acrylic pipeline system was studied. Images of slugs were recorded on video by S-VHS cameras, using an audio-visual mixer. Each image was then digitized frame -by-frame and analyzed on a SGI workstation. Detailed slug characteristics, including liquid film heights, slug translational velocity, mixing length, and, slug length, were obtained. more

Topics: Slug flow (74%), Two-phase flow (55%), Flow visualization (53%) more

Journal ArticleDOI: 10.1016/S0377-0273(03)00232-4
Abstract: At basaltic volcanoes, the sources of long-period and very-long-period seismicity and acoustic signals are frequently described in terms of fluid dynamic processes, in particular the formation and ascent of gas slugs within the magma column and their bursting at the surface. To investigate pressure changes associated with these processes, two-phase flow experiments have been carried out in vertical and inclined pipes with both single gas slugs and a continuously supplied gas phase. The ascent of individual gas slugs is accompanied by strong dynamic pressure variations resulting from the flow of liquid around the slug. These dynamic transients generate sub-static pressures below the ascending slug in viscosity-controlled systems, and produce super-static pressures when the slug reaches the surface and motion ceases in inertia-dominated systems. Conduit inclination promotes a change of regime from bubbly to slug flow and favours an increase in size and velocity of the slugs at the expense of their frequency of occurrence during continuously supplied two-phase flow. The experimental pressure data support previous theoretical analyses of oscillatory sources in ascending slugs as the slugs approach the surface and burst. Pressure oscillations are also observed during the release of gas slugs and in their wake region. more

Topics: Slug flow (69%), Gas slug (64%)

120 Citations

Journal ArticleDOI: 10.1021/CG401715E
Mo Jiang1, Zhilong Zhu1, Ernesto Jimenez1, Charles D. Papageorgiou2  +5 moreInstitutions (2)
Abstract: A novel continuous crystallizer design is described with the potential to provide improved control of crystal properties, improved process reproducibility, and reduced scale-up risk. Liquid and gas are introduced into one end of the tube at flow rates selected to spontaneously generate alternating slugs of liquid and gas that remain stable while cooling crystallization occurs in each liquid slug. Mixing within each stable self-circulating slug is maximized by controlling the slug aspect ratio through specification of liquid and gas flow rates. The crystallizer is designed so that nucleation and growth processes are decoupled to enhance the individual control of each phenomenon. Coaxial or radial mixers combine liquid streams to generate seed crystals immediately upstream of the growth zone where nucleation is minimized, and crystal growth is controlled by the varying temperature profile along the length of the tube. The slug-flow crystallizer design is experimentally demonstrated to generate large uniform... more

Topics: Slug flow (65%), Crystallization (52%), Nucleation (51%) more

74 Citations

Journal ArticleDOI: 10.1016/J.PETROL.2015.10.018
Jignesh Thaker1, Jyotirmay Banerjee1Institutions (1)
Abstract: Flow visualisation experiments are carried out to analyse the internal structure of different sub-regimes of slug flow. Five distinct slug flow sub-regimes are identified based on the visual observations. These sub-regimes correspond to slug at formation stage (onset of slug); less aerated slug; highly aerated slug; slug and plug; and slug and wavy. While superficial liquid velocity influences the formation of slug, it is observed that superficial gas velocity has a significant influence on the transition of sub-regimes. Maximum and minimum slug frequencies are observed in highly aerated zone and slug formation zone respectively. Highly aerated slug zone is extremely unstable and exhibits complex flow structure. Depending on superficial gas and liquid velocities, maximum value of slug frequency is observed at a distance between 30D and 60D from the pipe inlet. Slug frequency reduces along the length of the pipe due to viscous damping. An empirical correlation is developed for predicting the non-dimensional slug frequency (product of Strouhal number and Froude number) in terms of non-dimensional superficial liquid and gas velocities (represented by superficial Reynolds number of liquid ( Re SL ) and gas ( Re SG )) and length to diameter ratio ( L / D ). Identification of slug flow sub-regimes and their flow behaviour reported in this paper are of significant interest to oil production and transport processes where control of flow regime transitions is important in order to avoid severe unwanted jigging due to the formation and growth of slugs. more

Topics: Slug flow (82%), Flow visualization (51%)

37 Citations

Journal ArticleDOI: 10.1016/J.IJMULTIPHASEFLOW.2014.10.014
Abstract: Elongated bubbles were characterized experimentally for air–water flow in a horizontal pipe at nearly atmospheric conditions The range of flow rates employed covered regimes at the transition from elongated bubble to slug Ensemble-averaged digital image processing techniques were applied for detection of the liquid–gas interface with aid of a set of photo gates to synchronize bubble passage with image acquisition Quantitative data of front and tail parts of the bubbles were analysed for different mixture velocities and the results confirmed visual observations frequently reported in the literature Close to transition, a linear tendency of the bubble nose to move towards the pipe centerline position, for increasingly higher values of the Froude numbers, was observed and quantified Bubble tail shapes were quantified and the hydraulic jumps were shown to be dependent of Froude number, while the liquid film thicknesses were governed by the liquid volume fraction Changes on the bubbles characteristics are apparently linked to variations in the bubble velocities and seem to reflect a competition between viscous and inertia effects more

Topics: Slug flow (60%), Bubble (58%), Froude number (55%) more

30 Citations

Journal ArticleDOI: 10.1016/S0010-938X(02)00049-5
K. Sapre1, Sudipta Seal1, P. Jepson2, H.B Wang2  +2 moreInstitutions (2)
01 Jan 2003-Corrosion Science
Abstract: This communication reports into the effects of flow, fluid composition and the effectiveness of imidazoline inhibitors on the evolution and distribution of corrosion products on 1018 C-steel exposed to CO2 corrosion. Focused ion beam technique was used to measure the thickness of the corrosion product layer (CPL), in contrast to the conventional techniques used to observe the cross-section of specimens. Morphological analysis using scanning electron microscopy revealed topographical variations on the surface with the change in the multiphase environment. The CPL was found to be more porous in nature with the presence of oil in the multiphase environment. Electrochemical impedance spectroscopy was also used in the present study to measure the corrosion rates and was subsequently correlated to the CPL evolution for 1018 C-steel in multiphase environment. more

Topics: Corrosion (57%), Corrosion inhibitor (55%), Focused ion beam (50%)

15 Citations


Journal ArticleDOI: 10.1021/I160056A011
Abstract: Kase, S.. J. Appl. Polym. Sci., 18, 3279 (1974). Matovich. M. A,, Pearson, J. R. A,. Ind. Eng. Chem., Fundam., 8, 512 (1969). Miller, J. C., S.P.E. Trans., 3, 134 (1963). Nickell, R. E., Tanner, R. I., Caswell. E., J. FIMMech., 65, 189 (1974). Pearson. J. R. A,, Matovich. M. A,. Ind. Eng. Chem., Fundam., 8, 605 (1969). Pearson, J. R. A,, Shah, Y. T., Trans. SOC. Rheol., 16, 519 (1972). Pearson, J. R. A., Shah, Y. T.. Ind. Eng. Chem., Fundam., 13, 134 (1974). Shah, Y. T., Pearson, J. R. A.. Ind. Eng. Chem., Fundam.. 11, 150 (1972). Trouton, F. T.. Proc. Roy. SOC. Ser. A, 77, 426 (1906). Weinberger, C. B., Ph.D. Dissertation, University of Michigan, 1970 Weinberger, C. B., Goddard, J. D., Int. J. Multiphase Now, 1, 465 (1974). more

Topics: Slug flow (79%)

505 Citations

Journal ArticleDOI: 10.1002/CJCE.5450560601
M.K. Nicholson1, Khalid Aziz1, G.A. Gregory1Institutions (1)
Abstract: A semi-mechanistic model for two phase gas-liquid slug flow proposed recently by Dukler and Hubbard has been modified and extended to apply to the entire intermittent flow regime. Flow predictions of the model proposed in this paper are compared with detailed experimental data recently obtained for an air-oil system. The model requires the use of empirical correlations for the slug velocity and the in situ liquid volume fraction in the slug. In addition, either the slug frequencies or length corresponding to the given design conditions must be known. However, calculated values of average pressure gradient and in situ liquid volume fraction are relatively insensitive to these latter parameters, and in fact, good results are obtained assuming a constant slug length. The paper includes a discussion of the limitations of the proposed model and the expected direction of further study required to extend its mechanistic aspects. more

Topics: Slug flow (73%), Two-phase flow (55%)

180 Citations

Journal ArticleDOI: 10.1146/ANNUREV.FLUID.29.1.285
Abstract: ▪ Abstract The various tools for flow visualization have been significantly expanded over the past several years through the use of molecular scattering and molecular laser-induced fluorescence. These approaches have added the capability of sampling individual small volume elements within a flow, and by using cameras for detection, they are easily extended to sample lines and cross-sectional planes. This localized measurement capability means that these approaches can be made quantitative even in complex and/or unsteady flow fields. If the molecular species is naturally occurring, such as oxygen or nitrogen in air, then no seeding is required. Furthermore, in these applications, images of the flow can be frozen in time by using a short pulse laser for illumination. The distribution of the molecules reflects the true physics of the flow, so even raw images taken in this manner give an immediate understanding of flow field properties. With proper calibration, the images can be further analyzed to yield quan... more

133 Citations

Journal ArticleDOI: 10.1016/0301-9322(93)90057-2
Abstract: A flow regime map is compiled for the air/water two-phase flow in the Harwell 30 cm dia horizontal pipeline. The transitions differ substantially from those for small-diameter pipes and are not predicted accurately by any theoretical model. Data on slug frequency, length, holdup, translational velocity and pressure gradient are presented and compared with existing data. The results show that the pipe diameter has a large effect on all these properties. Several changes in the distribution of the phases in large-diameter pipes are reported. These are especially prominent in slug and annular flow. more

Topics: Slug flow (71%), Pressure gradient (51%)

86 Citations

Journal ArticleDOI: 10.1002/AIC.690431007
Xukun Luo1, Peijun Jiang1, Liang-Shih Fan1Institutions (1)
01 Oct 1997-Aiche Journal
Abstract: High-pressure operations are common in industrial applications of gas-liquid-solid fluidized-bed reactors for resid hydrotreating, Fischer-Tropsch synthesis, coal methanation, methanol synthesis, polymerization, and other reactions. The phase holdups and the heat-transfer behavior were studied experimentally in three-phase fluidized beds over a pressure range of 0.1--15.6 MPa. Bubble characteristics in the bed are examined by direct flow visualization. Pressure effects on the bubble coalescence and breakup are analyzed mechanistically. The study indicates that the pressure affects the hydrodynamics and heat-transfer properties of a three-phase fluidized bed significantly. The average bubble size decreases and the bubble-size distribution becomes narrower with an increase in pressure. The bubble-size reduction leads to an increase in the transition gas velocity from the dispersed bubble regime to the coalesced bubble regime, an increase in the gas holdup, and a decrease in the liquid and solids holdups. The pressure effect is insignificant above 6 MPa. The heat-transfer coefficient between an immersed surface and the bed increases to a maximum at pressure 6--8 MPa and then decreases with an increase in pressure at a given gas and liquid flow rate. This variation is attributed to the pressure effects on phase holdups and physical properties of the gas and liquid phases.more » A mechanistic analysis revealed that the major heat-transfer resistance in high-pressure three-phase fluidized beds resides in a liquid film surrounding the heat-0transfer surface. An empirical correlation is proposed to predict the heat-transfer coefficient under high-pressure conditions.« less more

Topics: Fluidized bed (58%), Bubble (56%), Chemical reactor (53%) more

66 Citations

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