Showing papers on "Slug flow published in 2001"
TL;DR: A multiphase microreactor based upon the use of slug flow through a narrow channel has been developed and the internal circulation, which is stimulated within the slugs by their passage along the channel, is responsible for a large enhancement in the interfacial mass transfer and the reaction rate.
Abstract: A multiphase microreactor based upon the use of slug flow through a narrow channel has been developed. The internal circulation, which is stimulated within the slugs by their passage along the channel, is responsible for a large enhancement in the interfacial mass transfer and the reaction rate. Mass transfer performance data has been obtained for a glass chip-based reactor in a 380 µm wide channel by monitoring the extraction of acetic acid from kerosene slugs as they moved along the reactor channel. Finally, the data was compared with that provided from other inter-phase contacting techniques.
524 citations
TL;DR: In this article, the characteristics of co-current upward air-water two-phase flow patterns in vertical equilateral triangular channels with hydraulic diameters of 2886, 1443 and 0866 mm were investigated experimentally.
247 citations
TL;DR: In this article, a wire-mesh sensor with a time resolution of 12 kHz was used to measure bubble size distributions in a gas-liquid flow, which is designed for a pipe of 512 mm diameter and consists of two electrode grids with 16 electrodes each, put in the flow direction behind each other.
231 citations
TL;DR: In this article, a two-phase flow pattern for refrigerant R-134a and air-water in horizontal tubes with inside diameter from 1.0 to 3.0 mm was performed.
186 citations
TL;DR: The results conclusively demonstrate that the neural network systems are appropriate classifiers of vertical flow regimes and the theoretical models and experimental databases used in the simulation are shown to be reliable.
148 citations
TL;DR: In this article, the evolution of hydrodynamic and statistical parameters along the pipe was studied experimentally in gas-liquid slug flow for various flow conditions and two pipe diameters.
103 citations
TL;DR: In this paper, the gas-liquid mass transfer of a monolith operating in the Taylor flow regime was compared with a literature model derived for single capillaries, and the comparison resulted in a prediction of the unit cell length ( gas bubble + liquid slug ).
91 citations
TL;DR: In this paper, a series of experiments using a test section with a specially constructed transparent liquid inlet is described, and high-speed video recordings show clearly the process of wave formation and analysis of the recordings gave data on wave frequencies and typical velocities.
58 citations
TL;DR: In this paper, the authors used an electromagnetic flowmeter and an impedance void-meter in an air-water two-phase experimental loop to measure the liquid velocity and the impedance of vertical slug flow.
55 citations
TL;DR: In this paper, the authors measured the velocity of sand particles at low concentration in horizontal and near horizontal pipes in air/water slug flow and found that particle velocity, VP is independent of pipe inclination in slug flow for pipe inclinations of up to three degrees.
48 citations
01 Jan 2001
TL;DR: In this paper, the results from simulations with active feedback control applied to severe slugging are compared against corresponding plots with feedback control, and the comparison is used to justify internal stability of the pipeline.
Abstract: Severe slugging in multiphase pipelines can cause serious and troublesome operational problems for downstream receiving production facilities. Recent results demonstrating the feasibility and the potential of applying dynamic feedback control to unstable multiphase flow like severe slugging and casing heading have been published (Refs. 4,9,1,5 and 2). This paper summarizes our findings on terrain -induced slug flow (Ref. 2). Results from field tests and as well as results from dynamic multiphase flow simulations are presented. The simulations were performed with the pipeline code OLGA2000. The controllers applied to all of these cases aim to stabilize the flow conditions by applying feedback control rather than coping with the slug flow in the downstream processing unit. The results from simulations with feedback control show in all cases stable process conditions both at the pipeline inlet and outlet, whereas without control severe slug flow is experienced. Pipeline profile plots of liquid volume fraction through a typical slug flow cycle are compared against corresponding plots with feedback control applied. The comparison is used to justify internal stability of the pipeline. Feedback control enables in many cases a reduced pipeline inlet pressure, which again means increased production rate. The paper summarizes the experience gained with active feedback control applied to severe slugging. Focus will be on extracting similarities and differences between the cases. The
TL;DR: In this paper, the presence of wire-coil inserts induces disturbance into gas and liquid flows so that the shape and motion of gas slug or bubbles in a wirecoil inserted tube are quite different from those observed in a smooth tube without insert.
TL;DR: Euler/Euler simulations are validated against experimental data acquired in a 2D rectangular column with 2 mm gap thickness, from bubbly to slug flow regimes, including the two hydrodynamic situations of stagnant and flowing liquid.
TL;DR: In this article, the authors describe some experiments performed on the BP Amoco 6-in. multiphase flow test facility located at Sunbury, Pennsylvania, which looked at the transport of field representative sand through a pipeline dip.
Abstract: Solids transport in multiphase systems falls under the umbrella of flow assurance. Unlike issues such as waxes and hydrates, solids transport has received relatively little attention to date. This is especially true for solids transport in high-viscosity fluids such as Venezuelan crude, where viscosities around the 300-400-cP mark are commonly encountered. This paper describes some experiments performed on the BP Amoco 6-in. multiphase flow test facility located at Sunbury. These looked at the transport of field representative sand through a pipeline dip. Several fluids were selected for these experiments to examine the influence of liquid viscosity on the results. These were water, oil, and two different carboxymethylcellulose solutions (150 and 300 cP). These experiments showed that, in slug flow, water and low-viscosity oil were able to transport tire sand uphill, whereas neither high-viscosity solution was able to transport the solids, This feature was examined in comparison to the model for solids transport in near-horizontal pipes discussed in this paper. Three-phase flow experiments (water-oil-air) were also performed to investigate the effect of oil or water prewetting of the solids on solids transport. If prewetted by water, the sand could not be moved by oil slugs. Once water was added to the system, the sand became increasingly mobile.
TL;DR: In this paper, an experimental study on the interaction between Taylor bubbles rising through a co-current flowing liquid in a vertical tube with 32 mm of internal diameter is reported.
Abstract: An experimental study on the interaction between Taylor bubbles rising through a co-current flowing liquid in a vertical tube with 32 mm of internal diameter is reported The flow pattern in the bubble's wake was turbulent and the flow regime in the liquid slug was either turbulent or laminar When the flow regime in the liquid slug is turbulent (i) the minimum distance between bubbles above which there is no interaction is 5D-6D; (ii) the bubble's rising velocity is in excellent agreement with the Nicklin relation; (iii) the experimental values of the bubble length compare well with theoretical predictions (Barnea 1990); (iv) the distance between consecutive bubbles varied from 13D to 16D and is insensitive to the liquid Reynolds number When the flow regime in the liquid slug is laminar (i) the wake length is about 5D-6D; (ii) the minimum distance between bubbles above which there is no interaction is higher than 25D; (iii) the bubble's rising velocity is significantly smaller than theoretical predictions These results were explained in the light of the findings of Pinto et al (1998) on coalescence of two Taylor bubbles rising through a co-current liquid
TL;DR: In this paper, a series of experiments on two-phase gas-liquid flow patterns in a test tube with a length of 356 mm and an inside diameter of 10 mm were performed aboard the Mir Space Station in August 1999.
TL;DR: In this article, a miniaturized four-sensor conductivity probe is designed to effectively minimize the reported limitations of the previous designs, which is capable of measuring both large and small bubbles, and a signal processing scheme is constructed for the probe in such a way that the two-phase parameters of different types of bubbles can be identified and categorized.
TL;DR: In this paper, a data reduction scheme using wavelet analysis combined with a phase-detection technique is used to discriminate the hot-film anemometer output signals into signals corresponding to different bubble size groups.
Abstract: A dual-probe hot-film anemometry technique has been developed to measure multiple gas-bubble velocities corresponding to different gas-bubble size groups in air–water flows. A data reduction scheme using wavelet analysis combined with a phase-detection technique is used to discriminate the hot-film anemometer output signals into signals corresponding to different bubble size groups. The phase and bubble size discrimination is based on the magnitude and time derivative of the signal, and the streamwise length of the gas bubbles. A cross-correlation between the discriminated signals from the two probes yields an average time difference of arrival of the gas bubbles at the two sensor locations. The velocities are estimated from the distance between the sensors and the time difference of arrival. The mean bubble size is estimated from the chord length distribution. Measurements performed in vertical-up air–water slug flow show the technique to be a viable method for obtaining bubble velocity and size information. The velocity measurements from the hot-film anemometry are corroborated using a high-speed quantitative flow visualization system.
TL;DR: In this article, a model was proposed to simulate and predict the effect of migrating bubbles on the reliability of hydrostatic level measurement systems (HLMSs), taking bubble formation, motion and mass diffusion of dissolved multi-component gases through the supersaturated liquid into consideration.
TL;DR: The effect of small upward inclinations on the transition from stratified to slug flow was studied in this paper, where the authors conducted experiments with air and water at atmospheric pressure, flowing in a pipe with a diameter of 00763 m and a length of 23 m, at upward inclined inclinations of 0°, 005°, 02°, 04° and 12°.
TL;DR: In this paper, the shape of the gas slug in tube is influenced by the diameter of tube, the flow rate and the inclination angle, and the length of gas slug increases with the superficial gas velocity.
TL;DR: In this paper, the stability of the governing differential equations for area averaged one-dimensional two-fluid model is analyzed in terms of gas and liquid momentum flux parameters, and the analysis results indicate that the use of momentum flux parameter is promising, since they reflect flow structure and help to stabilize the governing dynamic equations.
01 Jan 2001
TL;DR: In this paper, an experiment consisting of a glass annular heat exchanger was flown on NASA's KC-135 reduced gravity aircraft to study the effects of gravity on flow boiling.
Abstract: An experiment consisting of a glass annular heat exchanger was flown on NASA's KC-135 reduced gravity aircraft to study the effects of gravity on flow boiling. Visual data were taken to determine flow boiling regimes, which were then analyzed using five different flow regime maps. The flow regime maps enabled predictions of the quality, two-phase heat-transfer coefficients and wall temperatures in the axial direction during periods of reduced gravity. Results from this work illustrated the following trends: 1) less heat addition was needed to cause flow regime transitions in reduced gravity environments; 2) Earth-based flow regime maps did not correlate well with visual data or zero-g flow regime maps; 3) all of the zero-g flow regime maps produced similar results for calculations of quality, heat-transfer coefficient, and heat-exchanger temperature, indicating that all of them were acceptable for this application; and 4) that maximum heat transfer occurred at locations in the heat exchanger near the transition from bubble to slug flow.
TL;DR: The impact of introducing ‘slug’ flow into a tubular ‘in-to-out’ membrane bio-reactor is discussed and data are presented from both a theoretical hydrodynamic model of slug flow through a tube, and from a practical experiment which incorporates submerged and cross-flow membrane elements.
TL;DR: In this paper, the effects of gas velocity (0.6-1.2 m/s) and distribution geometry (opening area ratio, number of orifices and distributor types) on slug characteristics were determined.
Abstract: Pressure fluctuations in a fluidized bed (0.38 m-I.D.x4.4 m-high) of 1.23-mm polymer particles (LLDPE) were measured with different distributors. Slug characteristics (slug frequency and slug rising velocity) were determined by analyzing pressure fluctuations in the bed. The effects of gas velocity (0.6-1.2 m/s) and distributor geometry (opening area ratio, number of orifices and distributor types) on the slug characteristics were determined. The slug frequency decreases slightly with increasing gas velocity. However, slug rising velocity increases linearly with increasing excess fluidization velocity regardless of the distributors used.
TL;DR: In this paper, a semi-theoretical Weber number model is developed to include the shape influence on the slug-annular transition and the drift-flux model can predict well the observed boundary between bubble and slug flows.
Abstract: Experimental studies have been performed for horizontal two-phase air-water flows at normal and reduced gravity conditions in a square cross-section channel. The experiments at reduced gravity are conducted on board the Russian IL-76 reduced gravity airplane. Four flow patterns, namely bubble, slug, slug-annular transition and annular flows, are observed depending on the liquid and gas superficial velocities at both conditions. Semi-theoretical Weber number model is developed to include the shape influence on the slug-annular transition. It is shown that its prediction is in reasonable agreement with the experimental slug-annular transition under both conditions. For the case of two-phase gas-liquid flow with large value of the Froude number, the drift-flux model can predict well the observed boundary between bubble and slug flows.
TL;DR: In this paper, a model was developed to predict the liquid velocity field and bubble breakup in the recirculation region using the potential flow solution of the Hill's vortex, where the strength of the vortex was assumed to be directly proportional to the velocity of the annular wall jet.
TL;DR: A theoretical model for the computation of pressure drop in bubble-train flow inside capillaries of square cross-section was developed in this article, which is based on three contributions: hydrostatics, viscous pressure drop, and capillary pressure drop.