The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform
Kazuhiro Mae - One of the best experts on this subject based on the ideXlab platform.
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Gas−Liquid−Liquid Slug Flow for Improving Liquid−Liquid Extraction in Miniaturized Channels
Industrial & Engineering Chemistry Research, 2011Co-Authors: Nobuaki Aoki, Ryuichi Ando, Kazuhiro MaeAbstract:To increase the maximum flow rate that enables slug flow formation in miniaturized channels, gas-phase Slugs are added in a liquid−liquid slug flow to form a gas−liquid−liquid slug flow. Effects of...
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gas liquid liquid slug flow for improving liquid liquid extraction in miniaturized channels
Industrial & Engineering Chemistry Research, 2011Co-Authors: Nobuaki Aoki, Ryuichi Ando, Kazuhiro MaeAbstract:To increase the maximum flow rate that enables slug flow formation in miniaturized channels, gas-phase Slugs are added in a liquid−liquid slug flow to form a gas−liquid−liquid slug flow. Effects of...
Yehuda Taitel - One of the best experts on this subject based on the ideXlab platform.
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Prediction of Slug Length Distribution Along a Hilly Terrain Pipeline Using Slug Tracking Model
Journal of Energy Resources Technology, 2004Co-Authors: Eissa Al-safran, Yehuda Taitel, James P. BrillAbstract:Accurate prediction of slug length distribution and the maximum slug length in a hilly terrain pipeline is crucial for designing downstream separation facilities. A hilly terrain pipeline consists of interconnected uphill and downhill pipe sections, where Slugs can dissipate in the downhill sections and grow in the uphill sections. Furthermore, new Slugs can be generated at the dips (bottom elbows) and dissipate at the top elbows. Although existing steady-state models are capable of predicting the average slug length for pressure drop calculations and pipeline design, they are incapable of predicting detailed flow characteristics such as the maximum slug length expected at the exit of a hilly terrain pipeline. A transient slug tracking model based on a quasi-equilibrium formulation was developed to track the front and back of each individual slug, from which individual slug lengths are calculated. The model was verified with large-scale two-phase flow hilly terrain experimental data acquired at the Tulsa University Fluid Flow Projects (TUFFP). The results show a fairly accurate match between the model predictions and experimental data.
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Prediction of Slug Length Distribution Along a Hilly Terrain Pipeline Using Slug Tracking Model
Engineering Technology Conference on Energy Parts A and B, 2002Co-Authors: Eissa Al-safran, Yehuda Taitel, James P. BrillAbstract:Accurate prediction of slug length distribution and the maximum slug length in a hilly terrain pipeline is crucial for designing downstream separation facilities. A hilly terrain pipeline consists of interconnected uphill and downhill pipe sections, where Slugs can dissipate in the downhill sections and grow in the uphill sections. Furthermore, new Slugs can be generated at the dips (bottom elbows) and dissipate at the top elbows. Although existing steady-state models are capable of predicting the average slug length for pressure drop calculations and pipeline design, they are incapable of predicting detailed flow characteristics such as the maximum slug length expected at the exit of a hilly terrain pipeline. A transient slug tracking model based on a quasi-equilibrium formulation was developed to track the front and back of each individual slug, from which individual slug lengths are calculated. The model was verified with large-scale two-phase flow hilly terrain experimental data acquired at the Tulsa University Fluid Flow Projects (TUFFP). The results show a fairly accurate match between the model predictions and experimental data.Copyright © 2002 by ASME
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Slug-Tracking Model for Hilly Terrain Pipelines
SPE Journal, 2000Co-Authors: Yehuda Taitel, Dvora BarneaAbstract:Summary Slug flow is a very common occurrence in gas-liquid two-phase flow. Usually, it is an unfavorable flow pattern due to its unsteady nature, intermittency, and high-pressure drop. A hilly terrain pipeline consists of horizontal, uphill, and downhill sections. While slug flow is relatively well understood for any of the three configurations, there is a lack of understanding of how flow characteristics change when these configurations are interconnected, as in a hilly terrain pipeline. Almost all-previous slug flow studies assume a constant slug length once a slug is formed and developed into a stable slug. In reality, a slug can grow or shrink as it travels through a pipeline as a consequence of the hilly terrain configuration. In addition, Slugs can be generated at low "elbows" and dissipate at top "elbows." An experimental study conducted by Zheng et al.1 and Zheng2 clearly demonstrates the effect of hilly terrain pipeline configuration on slug characteristics. In the present work slug behavior in low and top elbows is simulated and studied. The effect of compressibility is included. Introduction In two-phase, gas-liquid flow in pipes, different forms of Slugs may occur. The most common Slugs are the "normal" Slugs or the "hydrodynamic" Slugs. These Slugs are generated at the inlet, or close to the inlet, as a result of the instability that does not allow the liquid to flow at the bottom and the gas on top of it. These Slugs are usually relatively short Slugs of the order of 20 to 40 pipe diameters near the entrance. Further downstream the Slugs can grow or shrink in length when the inclination angle is changed or due to compressibility effects. The second type of Slugs are terrain-induced Slugs. In this case, the flow is stratified in the downward inclined sections and liquid is accumulated in the lower elbows. As a result, very long Slugs can be developed in the low elbows. The gas is compressed upstream and, once the pressure upstream reaches a high value, it overcomes the hydrostatic pressure of the liquid in the upward sections and a chaotic blowout expansion occurs. This phenomenon is very complex and difficult to analyze. So far, successful analysis was achieved only for the restricted case of a single line and a single riser.3–8 The third kind of Slugs is the transient Slugs that can appear temporarily when the flow rate is changed or due to any transient process. For example, in the case of stratified flow one can develop a very long slug if liquid or gas flow rate increases suddenly. In this case, the liquid in the pipe is scooped ahead in the form of a long transient slug. Eventually, the flow ends in a form of normal slug flow. The analysis is based on quasiequilibrium formulation, which also indicates that it is completely compatible with the steady-state unit-cell formulation of slug flow modeling. Recent efforts were dedicated to develop the terrain slugging capability. Since compressibility effects are taken into account here, the model can handle the terrain slugging phenomenon. The analysis is much more general compared to the analysis in Zheng et al.1 as it takes into account compressibility, change of liquid holdup in the slug, true calculation of the film thickness in the film zone, and the possible variation of the translational velocity of the elongated bubble that follows the liquid slug. Slug-Tracking Model The present basic approach was presented first in Taitel and Barnea.9 Since then, some modifications were introduced. The modification includes the possibility of changing the inclination angle and the treatment of the flow at the top and bottom elbows. Also, the condition for terrain slugging was added and slug growth under such conditions was implemented. For the sake of completeness, the basic approach and formal equations used follow below. It should be stressed, however, that the complication lies primarily in the programing scheme. The number of possible events that can take place is enormous. For example: Slugs can move at different velocities and can be overtaken by Slugs behind; Slugs may or may not dissipate at pipes of downward inclination and form a series of films which can move at different velocities and may merge to form a continuous long film. Thus, in spite of the simplicity of the basic formulation, its translation into a working program is quite a complex and tedious job. A schematic geometry of the system is shown in Figs. 1 and 2. A typical slug unit consists of a liquid slug zone (that may contain gas bubbles) of length ls followed by a film (and gas) zone of length lf The liquid film is assumed to have a constant level equal to the equilibrium level. 6 The Slugs units are numbered from (1), the first slug, to (N), the last slug, that is, the slug that just enters the pipe. At the present, the model does not include mass transfer (evaporation or condensation). The location of each slug in the pipe is described by the position of the slug front, Xi and the tail of the slug, Yi (see Fig. 1). The slug front at X i propagates with a velocity vf, i while the slug tail, at Yi propagates at a velocity vt, i. The translational velocity vt, i depends on the mixture velocity in the slug, us, i The front of the liquid slug scoops the liquid film in front of it and the velocity of the slug front, vf, i, is determined from a liquid mass balance at the slug front. Figs. 2, 3, and 4 are schematic plots that show the different conditions that can take place in a hilly terrain pipeline. Fig. 2 shows that at the top elbow the liquid film is split into two parts that flow downward from the top elbow, leaving the top elbow dry. Slugs that pass through the dry zone decrease in length and, if they are short, they dissipate completely in the downward section. Fig. 3 describes the process in the lower elbow when Slugs approach the elbow. Once a slug passes the lower elbow the film behind the slug flows downward in both the upward and the downward sections. Thus, liquid is accumulated in the low elbow. Then, one of the two events can take place. A new slug can be generated, or the liquid accumulated is scooped by an upstream slug that approaches the low elbow. In this case, the slug length in the upward section after the elbow increases in length. Fig. 4 shows what can happen when stratified flow takes place in the downward section. In this case, normal hydrodynamic Slugs can be generated in the bottom elbow. The other possibility is that a long slug grows in the bottom elbow. This phenomenon takes place when the upward inclined pipe has a steep angle, and when the stratified pipe is sufficiently long such that gas is compressed and allows the generation of a long liquid slug that penetrates "backward" upstream into the inclined stratified section.
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Slug flow behavior in a hilly terrain pipeline
International Journal of Multiphase Flow, 1994Co-Authors: G. Zheng, James P. Brill, Yehuda TaitelAbstract:Abstract When Slugs flow in a hilly terrain pipeline that contains sections of different inclination they undergo a change of length as the Slugs move from section to section. In addition, Slugs can be generated at low elbows, dissipate at top elbows and shrink or grow in length as they travel along the pipe. In this work a slug-tracking model is proposed that follows the behavior of all individual Slugs and is capable of simulating the aforementioned processes. Two cases are considered: the case of steady slug flow, for which each slug maintains its identity as it flows from one section to another; and the more complex case, where new Slugs are generated and disappear, and the slug identity along the hilly terrain is not maintained. Comparisons with experimental data demonstrate the capability of this slug-tracking method and show that the proposed model is able to simulate correctly slug behavior in a hilly terrain pipeline.
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a model for slug length distribution in gas liquid slug flow
International Journal of Multiphase Flow, 1993Co-Authors: Dvora Barnea, Yehuda TaitelAbstract:Abstract Intermittent, or slug flow, is a very common occurrence in gas—liquid two-phase pipe flow. Usually slug flow is an undesirable flow pattern since the existence of long lumps of liquid Slugs that move at high speed is unfavorable to gas—liquid transportation. Considerable efforts have been devoted to the prediction of the slug hydrodynamic characteristics, primarily by considering an average slug length and calculating average parameters. This approach is useful, and in many cases it is adequate for many engineering calculations. There are, however, cases where this information is not sufficient and much more detailed information concerning the slug length distribution, the mean slug length and the maximum possible slug length is essential. This work presents a model that is able to calculate the slug length distribution at any desired position along the pipe. The model assumes a random distribution at the inlet of the pipe and it calculates the increase or decrease in each individual slug length, including the disappearance of the short Slugs, as they move downstream. The results of the calculation show that for the fully developed slug flow the mean slug length is about 1.5 times the minimum stable slug length and the maximum length is about 3 times the minimum stable slug length.
Ida Skaar - One of the best experts on this subject based on the ideXlab platform.
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effect of invasive slug populations arion vulgaris on grass silage
Animal Feed Science and Technology, 2015Co-Authors: A T Randby, Kristine Gismervik, Arild Andersen, Ida SkaarAbstract:Abstract This study aimed to explore how invasive slug populations of Arion vulgaris influence fermentation quality, in-silo losses and aerobic stability of grass silage, and the efficiency of silage additives and wilting to improve the quality of silages from slug contaminated crops. The effect of four levels, including control, of a slug contaminated grass crop, was evaluated in laboratory scale. The crop used was wilted to two dry matter (DM) levels: low (253 g DM/kg) and high (372 g DM/kg). Adult Slugs were applied to the low DM crop corresponding to 5 (low level), 10 (medium) and 20 (high level) 7-g sized A. vulgaris per m2 in an assumed harvested regrowth yield of 2.5 ton DM per ha. For the high DM crop, the applied slug levels corresponded to 6 (low level), 12 (medium) and 24 (high level) Slugs per m2. At low DM level, the effect of four additive treatments, control (C), inoculation with Lactobacillus plantarum (LP), a formic, propionic and benzoic acid mixture (ACID) and a chemical additive containing benzoic acid, NaNO2, hexamethylenetetramine and propionic acid (CHEM) were tested. Increasing slug contamination gave increasing quality reductions both in silages containing 253 and 372 g DM/kg. Compared with untreated silage, LP-treatment did not improve silage fermentation quality of contaminated crops. Treatment with ACID and CHEM, however, considerably improved the quality of heavily contaminated silages. The much higher crude protein concentration in Slugs compared to grass crop made Slugs a more “difficult-to-ensile” material. Wilting of the harvested crop to 372 g DM/kg was not sufficient to control silage fermentation of slug contaminated crop. With contamination levels from 138 to 553 g fresh slug weight/kg crop DM, efficient silage additives were able to ensure acceptable fermentation quality of grass silages.
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effect of invasive slug populations arion vulgaris on grass silage ii microbiological quality and feed safety
Animal Feed Science and Technology, 2015Co-Authors: Kristine Gismervik, Torkjel Bruheim, Liv Marit Rorvik, A T Randby, Arild Andersen, Marta Hernandez, Ida SkaarAbstract:Abstract This study aimed to explore how invasive slug populations of Arion vulgaris influenced the microbiological quality and animal feed safety of grass silage, and the efficiency of silage additives and wilting to control the microbiology of slug contaminated crops. The effect of four slug contamination levels, including control, of a grass crop harvested for silage production, was evaluated in laboratory scale. The crop was wilted to two dry matter (DM) levels: low (253 g DM/kg) and high (372 g DM/kg). Adult Slugs were applied to the low DM crop corresponding to 5 (low level), 10 (medium) and 20 (high level) seven-gram sized Arion vulgaris per m 2 in an assumed harvested regrowth yield of 2.5 ton DM/ha. For the high DM crop, slug weights corresponding to 6 (low level), 12 (medium) and 24 (high level) Slugs per m 2 were applied. At low DM level, the effect of four additive treatments; control (C), inoculation with Lactobacillus plantarum (LP), a formic, propionic and benzoic acid mixture (ACID) and a chemical additive containing benzoic acid, NaNO 2 , hexamethylenetetramine and propionic acid (CHEM) were tested. Slugs, slug feces, grass, soil and silages were analyzed for lactic acid bacteria (LAB), Enterobacteriaceae , Listeria monocytogenes , Clostridium tyrobutyricum , molds and yeasts by cultivation methods and Clostridium botulinum type C by real-time PCR analysis. Increasing slug contamination reduced the microbial quality of silages by increasing C. tyrobutyricum levels at both silage DM levels. Only silages without Slugs and silages treated with the nitrite containing additive CHEM had non-detectable mean levels of C. tyrobutyricum . Increasing slug contamination increased LAB enumerations in silages. No microbes of risk to human or animal health were detected in anaerobic silages even at the highest slug contamination.
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invasive slug populations arion vulgaris as potential vectors for clostridium botulinum
Acta Veterinaria Scandinavica, 2014Co-Authors: Kristine Gismervik, Torkjel Bruheim, Liv Marit Rorvik, Solveig Haukeland, Ida SkaarAbstract:Background: Norwegian meadows, including those for silage production, are recently found heavily invaded by the slug Arion vulgaris in exposed areas. As a consequence, large numbers of Slugs might contaminate grass silage and cause a possible threat to animal feed quality and safety. It is well known that silage contaminated by mammalian or avian carcasses can lead to severe outbreaks of botulism among livestock. Invertebrates, especially fly-larvae (Diptera), are considered important in the transfer of Clostridium botulinum type C and its toxins among birds in wetlands. C. botulinum form highly resistant spores that could easily be consumed by the Slugs during feeding. This study aimed to determine whether Arion vulgaris could hold viable C. botulinum and enrich them, which is essential knowledge for assessing the risk of botulism from slug-contaminated silage. Slug carcasses, slug feces and live Slugs were tested by a quantitative real-time PCR (qPCR) method after being fed ≅ 5.8 × 10 4 CFU C. botulinum type C spores/slug. Results: Low amounts of C. botulinum were detected by qPCR in six of 21 slug carcasses with an even spread throughout the 17 day long experiment. Declining amounts of C. botulinum were excreted in slug feces up to day four after the inoculated feed was given. C. botulinum was only quantified the first two days in the sampling of live Slugs. The viability of C. botulinum was confirmed for all three sample types (slug carcasses, slug feces and live Slugs) by visible growth in enrichment media combined with obtaining a higher quantification cycle (Cq) value than from the non-enriched samples. Conclusions: Neither dead nor live invasive Arion vulgaris Slugs were shown to enrich Clostridium botulinum containing the neurotoxin type C gene in this study. Slugs excreted viable C. botulinum in their feces up to day four, but in rapidly decreasing numbers. Arion vulgaris appear not to support enrichment of C. botulinum type C.
R V A Oliemans - One of the best experts on this subject based on the ideXlab platform.
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prediction of the transition from stratified to slug flow or roll waves in gas liquid horizontal pipes
International Journal of Multiphase Flow, 2009Co-Authors: Usama Kadri, R F Mudde, R V A Oliemans, M Bonizzi, Paolo AndreussiAbstract:Abstract In stratified gas–liquid horizontal pipe flow, growing long wavelength waves may reach the top of the pipe and form a slug flow, or evolve into roll-waves. At certain flow conditions, Slugs may grow to become extremely long, e.g. 500 pipe diameter. The existence of long Slugs may cause operational upsets and a reduction in the flow efficiency. Therefore, predicting the flow conditions at which the long Slugs appear contributes to a better design and management of the flow to maximize the flow efficiency. In this paper, we introduce a wave transition model from stratified flow to slug flow or roll-wave regimes. The model tracks the wave crest along the pipe. If the crest overtakes the downstream wave end before hitting the top of the pipe, a roll-wave is formed, otherwise a slug. For model validation we performed measurements in air–water horizontal pipe flow facilities with internal diameters of 0.052 and 0.06 m. Furthermore, we made numerical calculations using a transient one-dimensional multiphase flow simulator (MAST) which adopts a four-field model. The model presented in this paper successfully predicts the evolution of waves and their transition into either Slugs or roll-waves. It also predicts the formation time of Slugs and roll-waves with a satisfactory agreement.
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a growth model for dynamic Slugs in gas liquid horizontal pipes
International Journal of Multiphase Flow, 2009Co-Authors: Usama Kadri, M L Zoeteweij, R F Mudde, R V A OliemansAbstract:Long liquid Slugs, with sizes reaching 500 pipe diameters or more, may form in gas–liquid horizontal pipe flow at intermediate liquid loadings. Such Slugs cause serious operational upsets due to the strong fluctuations in flow supply and pressure. Therefore, predicting the transition from short (hydrodynamic) to long slug flow regimes may play a significant role in preventing or reducing the negative effects caused by the long Slugs. In this paper we introduce a growth model for calculating the average slug length in horizontal and near horizontal pipes. The model applies a volumetric balance between the front and tail of the slug in order to calculate the slug growth rate. The dynamic behaviour of the liquid at the tail is described by a linear kinematic relation between the slug downstream and the wave upstream. For the validation of the model we performed measurements in a 137 m length air–water horizontal pipe flow of an internal diameter (i.d.) of 0.052 m. The measurements provide a detailed flow map of the long slug regime and sub-regimes. Furthermore, we compared predictions by the model with available data for a range of 0.019–0.095 m i.d. pipes to investigate the effect of varying operation pressures, different inlet conditions, different fluid properties and slight inclinations. The model predicted the transitions from hydrodynamic to long Slugs with satisfactory agreements, however it underpredicts the average slug length at relatively large mixture velocities.
Usama Kadri - One of the best experts on this subject based on the ideXlab platform.
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prediction of the transition from stratified to slug flow or roll waves in gas liquid horizontal pipes
International Journal of Multiphase Flow, 2009Co-Authors: Usama Kadri, R F Mudde, R V A Oliemans, M Bonizzi, Paolo AndreussiAbstract:Abstract In stratified gas–liquid horizontal pipe flow, growing long wavelength waves may reach the top of the pipe and form a slug flow, or evolve into roll-waves. At certain flow conditions, Slugs may grow to become extremely long, e.g. 500 pipe diameter. The existence of long Slugs may cause operational upsets and a reduction in the flow efficiency. Therefore, predicting the flow conditions at which the long Slugs appear contributes to a better design and management of the flow to maximize the flow efficiency. In this paper, we introduce a wave transition model from stratified flow to slug flow or roll-wave regimes. The model tracks the wave crest along the pipe. If the crest overtakes the downstream wave end before hitting the top of the pipe, a roll-wave is formed, otherwise a slug. For model validation we performed measurements in air–water horizontal pipe flow facilities with internal diameters of 0.052 and 0.06 m. Furthermore, we made numerical calculations using a transient one-dimensional multiphase flow simulator (MAST) which adopts a four-field model. The model presented in this paper successfully predicts the evolution of waves and their transition into either Slugs or roll-waves. It also predicts the formation time of Slugs and roll-waves with a satisfactory agreement.
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Slugs, turbulence and the butterfly effect
2009Co-Authors: Usama Kadri, Robert F. Mudde, R. V. A. OliemensAbstract:In this paper we investigate the formation of slug flow in horizontal pipes. We found that a slug is characterized by the memory of the turbulent stresses that formed it. However, the history of other turbulent fluctuations downstream the pipe is destroyed by passing Slugs, preventing the formation of new Slugs during and after their passage. As a result, the frequency of slug formation downstream the pipe is reduced. A probabilistic model is provided by making use of integral scales of turbulence in pipe flow and probabilistic effects of the properties of slug formation along the pipe. The model can act as a fundamental scientific guideline towards the design of gas-liquid horizontal pipe flow. Predictions by the model were compared with slug frequency measurements found in literature. The agreement between the predictions and the measurements supports the idea that the turbulent fluctuations at the interface are responsible for the formation of Slugs.
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a growth model for dynamic Slugs in gas liquid horizontal pipes
International Journal of Multiphase Flow, 2009Co-Authors: Usama Kadri, M L Zoeteweij, R F Mudde, R V A OliemansAbstract:Long liquid Slugs, with sizes reaching 500 pipe diameters or more, may form in gas–liquid horizontal pipe flow at intermediate liquid loadings. Such Slugs cause serious operational upsets due to the strong fluctuations in flow supply and pressure. Therefore, predicting the transition from short (hydrodynamic) to long slug flow regimes may play a significant role in preventing or reducing the negative effects caused by the long Slugs. In this paper we introduce a growth model for calculating the average slug length in horizontal and near horizontal pipes. The model applies a volumetric balance between the front and tail of the slug in order to calculate the slug growth rate. The dynamic behaviour of the liquid at the tail is described by a linear kinematic relation between the slug downstream and the wave upstream. For the validation of the model we performed measurements in a 137 m length air–water horizontal pipe flow of an internal diameter (i.d.) of 0.052 m. The measurements provide a detailed flow map of the long slug regime and sub-regimes. Furthermore, we compared predictions by the model with available data for a range of 0.019–0.095 m i.d. pipes to investigate the effect of varying operation pressures, different inlet conditions, different fluid properties and slight inclinations. The model predicted the transitions from hydrodynamic to long Slugs with satisfactory agreements, however it underpredicts the average slug length at relatively large mixture velocities.
