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David W Agar - One of the best experts on this subject based on the ideXlab platform.
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Hydrodynamics of liquid-liquid Slug Flow capillary microreactor: Flow regimes, Slug size and pressure
2016Co-Authors: M N Kashid, David W AgarAbstract:The use of liquid-liquid Slug Flow in the capillary microreactor is a promising technique for intensifying heat and mass transfer in liquid-liquid reactions. Although the concept has so far been exploited without much reference to the detailed hydrodynamics involved, these are nevertheless inherently crucial to its potential for providing well-defined reaction conditions and identifying asymptotic performance limits and thus a worthwhile subject for more rigorous analysis. In this work, the effect of various operating conditions on the Slug size and pressure drop has been investigated. Experiments were carried out to determine these parameters using a Y-shaped mixing element with various downstream capillaries. The experimentally measured pressure drops are in reasonably good agreement with the theoretically predicted values. The capillary dimensions exhibit a significant effect on Slug size and pressure drop. Notation: A Cross sectional area of the microreactor, m2 ID Internal diameter of capillary, m L Length of the microreactor, m l Length of the Slug, m P Pressure, kPa ∆P Pressure drop, kPa Q volumetric Flow rate, m3/s r Radius of capillary, m V Slug Flow velocity, m/s Greek symbols γ Interfacial surface tension, N/m θ Contact angl
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liquid liquid Slug Flow capillary microreactor
Chemical Engineering & Technology, 2011Co-Authors: Andreas Ufer, Matthias Mendorf, Aras Ghaini, David W AgarAbstract:The liquid-liquid Slug Flow capillary microreactor offers an excellent mass transfer performance for extraction and biphasic reactions. In combination with a simple phase separator based on wettability discrimination between the two liquids, it provides a powerful tool for process intensification and microscale processing. By new visualization techniques, the interfacial surface and Slug vortex structures dictating inter- and intraphase mass transfer have been revealed to be more complex than previously assumed. Suspending fine catalyst particles in one phase of a two-phase Slug Flow is an effective technique for using heterogeneous catalysts in microreactors, owing to the very good mass transfer characteristics and because catalyst recovery becomes simply a matter of separating the catalyst carrier phase from the reaction medium. To exploit the performance attributes of capillary microreactors at higher throughputs, distributor and control strategies for parallelisation were developed to provide a Flow distribution uniform to within 1 % or less.
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on the hydrodynamics of liquid liquid Slug Flow capillary microreactors
Asia-Pacific Journal of Chemical Engineering, 2008Co-Authors: M N Kashid, David W Agar, Fernandez D Rivas, Stefan TurekAbstract:Microreactor technology is an important method of process intensification. Liquid–liquid Slug Flow capillary microreactors have been used to intensify the reactions with heat and mass transfer limitations. In this type of reactor, either two liquids Flow alternate to each other in a capillary or one liquid Flows as a continuous Flow while the other Flows in the form of enclosed drops (Slugs) depending on the interfacial tension between two liquids and liquid adhesion with the solid walls. The enhanced mass transfer is due to the internal circulations within the Slugs, which rise due to the shearing action between the Slug axis and the capillary wall or continuous phase. The Slug size and the intensity of internal circulations depend on the type of mixing element and physical properties of the liquids. The proper understanding of physical behaviour of fluids at the microscale is a challenging issue for the growing microreactor application demands. This article highlights the hydrodynamic characteristics of the liquid–liquid Slug Flow capillary microreactor. Experimental results on Flow regime, Slug size and particle image velocimetry along with corresponding complementary state-of-the-art computational fluid dynamics (CFD) simulations are discussed in detail
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cfd modelling of mass transfer with and without chemical reaction in the liquid liquid Slug Flow microreactor
Chemical Engineering Science, 2007Co-Authors: M N Kashid, David W Agar, Stefan TurekAbstract:A finite element based computational fluid dynamics (CFD) model was developed to study the Flow patterns within the Slugs and mass transfer with and without superimposed chemical reaction between two consecutive Slugs in the liquid–liquid Slug Flow capillary microreactor. Since the Slug Flow is a series of alternate Slugs of one phase separated by the other, a single element consisting of a Slug of each phase was considered. The two Slugs in a single domain were distinguished by two kinematic viscosities. The effects of various operating conditions on circulation patterns, mass transfer and reaction are discussed in detail. Finally, the results are compared with data from the literature.
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hydrodynamics of liquid liquid Slug Flow capillary microreactor Flow regimes Slug size and pressure drop
Chemical Engineering Journal, 2007Co-Authors: M N Kashid, David W AgarAbstract:Abstract The use of liquid–liquid Slug Flow in the capillary microreactor is a promising technique for intensifying heat and mass transfer in liquid–liquid reactions. Although the concept has so far been exploited without much reference to the detailed hydrodynamics involved, these are nevertheless inherently crucial to its potential for providing well-defined reaction conditions and identifying asymptotic performance limits and thus a worthwhile subject for more rigorous analysis. In this work, the effect of various operating conditions on the Flow regimes, Slug size, interfacial area and pressure drop has been investigated. Experiments were carried out to determine these parameters using different Y-junction mixing elements with various downstream capillaries. The pressure drop was measured across the Y-shaped mixing element and along the length of the downstream capillaries. Since the Slug Flow is comprised of alternating segments of two immiscible phases, the experimentally measured pressure drop along the length of the downstream capillary was compared with a simplified theoretical prediction based on capillary pressure and hydrodynamic pressure drop of the two individual phases. As the comparison showed considerable discrepancies, the model was modified to include the formation of a thin wall film by one of the phases. The pressure drop model taking the presence of a thin film of the organic phase into account is found to be in good agreement with experimental results. The power required for generating interfacial area was ascertained from the pressure losses over the Y-junction. The results of interfacial area and power requirement calculations indicate that the Slug Flow capillary microreactor is far superior to conventional equipment in terms of the specific energy, power input per unit interfacial area generated.
M N Kashid - One of the best experts on this subject based on the ideXlab platform.
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Hydrodynamics of liquid-liquid Slug Flow capillary microreactor: Flow regimes, Slug size and pressure
2016Co-Authors: M N Kashid, David W AgarAbstract:The use of liquid-liquid Slug Flow in the capillary microreactor is a promising technique for intensifying heat and mass transfer in liquid-liquid reactions. Although the concept has so far been exploited without much reference to the detailed hydrodynamics involved, these are nevertheless inherently crucial to its potential for providing well-defined reaction conditions and identifying asymptotic performance limits and thus a worthwhile subject for more rigorous analysis. In this work, the effect of various operating conditions on the Slug size and pressure drop has been investigated. Experiments were carried out to determine these parameters using a Y-shaped mixing element with various downstream capillaries. The experimentally measured pressure drops are in reasonably good agreement with the theoretically predicted values. The capillary dimensions exhibit a significant effect on Slug size and pressure drop. Notation: A Cross sectional area of the microreactor, m2 ID Internal diameter of capillary, m L Length of the microreactor, m l Length of the Slug, m P Pressure, kPa ∆P Pressure drop, kPa Q volumetric Flow rate, m3/s r Radius of capillary, m V Slug Flow velocity, m/s Greek symbols γ Interfacial surface tension, N/m θ Contact angl
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cfd modelling of liquid liquid multiphase microstructured reactor Slug Flow generation
Chemical Engineering Research & Design, 2010Co-Authors: M N Kashid, A Renken, Lioubov KiwiminskerAbstract:Microreactor technology, an important method of process intensification, offers numerous potential benefits for the process industries. Fluid–fluid reactions with mass transfer limitations have already been advantageously carried out in small-scale geometries. In liquid–liquid microstructured reactors (MSR), alternating uniform Slugs of the twophase reaction mixture exhibit well-defined interfacial mass transfer areas and Flow patterns. The improved control of highly exothermic and hazardous reactions is also of technical relevance for large-scale production reactors. Two basic mass transfer mechanisms arise: convection within the individual liquid Slugs and diffusion between adjacent Slugs. The Slug size in liquid–liquid MSR defines the interfacial area available for mass transfer and thus the performance of the reactor. There are two possibilities in a Slug Flow MSR depending on the interaction of the liquids with the solid wall material: a dispersed phase Flow in the form of an enclosed Slug in the continuous phase (with film—complete wetting of the continuous phase) and an alternate Flow of two liquids (without film—partial wetting of the continuous phase). In the present work, a computational fluid dynamics (CFD) methodology is developed to simulate the Slug Flow in the MSR for both types of Flow systems. The results were validated with the experimental results of Tice et al. (J.D. Tice, A.D. Lyon and R.F. Ismagilov, Effects of viscosity on droplet formation and mixing in microfluidic channels, Analytica Chimica Acta 507 (1) (2004), pp. 73–77.).
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on the hydrodynamics of liquid liquid Slug Flow capillary microreactors
Asia-Pacific Journal of Chemical Engineering, 2008Co-Authors: M N Kashid, David W Agar, Fernandez D Rivas, Stefan TurekAbstract:Microreactor technology is an important method of process intensification. Liquid–liquid Slug Flow capillary microreactors have been used to intensify the reactions with heat and mass transfer limitations. In this type of reactor, either two liquids Flow alternate to each other in a capillary or one liquid Flows as a continuous Flow while the other Flows in the form of enclosed drops (Slugs) depending on the interfacial tension between two liquids and liquid adhesion with the solid walls. The enhanced mass transfer is due to the internal circulations within the Slugs, which rise due to the shearing action between the Slug axis and the capillary wall or continuous phase. The Slug size and the intensity of internal circulations depend on the type of mixing element and physical properties of the liquids. The proper understanding of physical behaviour of fluids at the microscale is a challenging issue for the growing microreactor application demands. This article highlights the hydrodynamic characteristics of the liquid–liquid Slug Flow capillary microreactor. Experimental results on Flow regime, Slug size and particle image velocimetry along with corresponding complementary state-of-the-art computational fluid dynamics (CFD) simulations are discussed in detail
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cfd modelling of mass transfer with and without chemical reaction in the liquid liquid Slug Flow microreactor
Chemical Engineering Science, 2007Co-Authors: M N Kashid, David W Agar, Stefan TurekAbstract:A finite element based computational fluid dynamics (CFD) model was developed to study the Flow patterns within the Slugs and mass transfer with and without superimposed chemical reaction between two consecutive Slugs in the liquid–liquid Slug Flow capillary microreactor. Since the Slug Flow is a series of alternate Slugs of one phase separated by the other, a single element consisting of a Slug of each phase was considered. The two Slugs in a single domain were distinguished by two kinematic viscosities. The effects of various operating conditions on circulation patterns, mass transfer and reaction are discussed in detail. Finally, the results are compared with data from the literature.
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hydrodynamics of liquid liquid Slug Flow capillary microreactor Flow regimes Slug size and pressure drop
Chemical Engineering Journal, 2007Co-Authors: M N Kashid, David W AgarAbstract:Abstract The use of liquid–liquid Slug Flow in the capillary microreactor is a promising technique for intensifying heat and mass transfer in liquid–liquid reactions. Although the concept has so far been exploited without much reference to the detailed hydrodynamics involved, these are nevertheless inherently crucial to its potential for providing well-defined reaction conditions and identifying asymptotic performance limits and thus a worthwhile subject for more rigorous analysis. In this work, the effect of various operating conditions on the Flow regimes, Slug size, interfacial area and pressure drop has been investigated. Experiments were carried out to determine these parameters using different Y-junction mixing elements with various downstream capillaries. The pressure drop was measured across the Y-shaped mixing element and along the length of the downstream capillaries. Since the Slug Flow is comprised of alternating segments of two immiscible phases, the experimentally measured pressure drop along the length of the downstream capillary was compared with a simplified theoretical prediction based on capillary pressure and hydrodynamic pressure drop of the two individual phases. As the comparison showed considerable discrepancies, the model was modified to include the formation of a thin wall film by one of the phases. The pressure drop model taking the presence of a thin film of the organic phase into account is found to be in good agreement with experimental results. The power required for generating interfacial area was ascertained from the pressure losses over the Y-junction. The results of interfacial area and power requirement calculations indicate that the Slug Flow capillary microreactor is far superior to conventional equipment in terms of the specific energy, power input per unit interfacial area generated.
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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enhanced production of ethyl pyruvate using gas liquid Slug Flow in microchannel
Chemical Engineering Journal, 2011Co-Authors: Toshiya Yasukawa, Nobuaki Aoki, Wataru Ninomiya, Ken Ooyachi, Kazuhiro MaeAbstract:Abstract The use of a gas–liquid Slug Flow in a microreactor has several advantages such as a large surface area for contacting gas and liquid phases and circulation Flow inside Slugs. These advantages accelerate the mass transfer between the two phases, resulting in a high concentration of dissolved gas. The enhanced mass transfer is useful in carrying out liquid phase oxidation that uses oxygen gas as the oxidizing agent. The gas–liquid Slug Flow in a microreactor system is applied to the oxidation of ethyl lactate using an oxy-vanadium species for producing ethyl pyruvate. The reactor system includes two T-shaped micromixers: one for mixing the substrate with a catalyst solution and the other for generating Slug Flow by the addition of oxygen. The oxidation reaction proceeds right after the Slug Flow is generated in the second mixer, because the substrate and the catalyst mix rapidly in the first micromixer. Moreover, a high concentration of dissolved oxygen due to improved mass transfer in Slug Flow increases the oxidation reaction rate. Therefore, compared to a batch reaction, the synthesis using Slug Flow provides high yields of ethyl pyruvate per unit time and achieves satisfactory productivity at the reaction temperature of 323 K, which is lower than that employed in conventional syntheses. The proposed system enables the production of ethyl pyruvate using a simple reactor setup with reduced energy consumption.
J Jaap C Schouten - One of the best experts on this subject based on the ideXlab platform.
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liquid liquid Slug Flow separation in a slit shaped micro device
Chemical Engineering Journal, 2012Co-Authors: W A Gaakeer, M H J M De Croon, J Van Der Schaaf, J Jaap C SchoutenAbstract:Abstract As micro reactors are more and more used in research and production, the need for micro work-up facilities like separators for organic and aqueous Slug Flow is growing. Numerous examples of these capillary force based separators are presented in literature. The disadvantage of these devices is that at higher Flow rates, the hydraulic pressure exceeds the capillary pressure which results in breakthrough. In this paper we present a micro separator for liquid–liquid Slug Flow with hydrophobic and hydrophilic rectangular capillaries (height: 0.1–2 mm, length: 5 mm and width: 10 mm) to prevent this. The narrow height of the capillary provides a large capillary pressure and the large width a low hydraulic pressure. Separation efficiencies of 99.5% for Flow rates of 30–50 ml min −1 are obtained. The ratio between the capillary pressure and the hydraulic pressure is a good predictor of the separation efficiency and must have the value 2 or higher to prevent breakthrough.
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liquid liquid Slug Flow hydrodynamics and pressure drop
Chemical Engineering Science, 2011Co-Authors: J Jovanovic, Wenya Zhou, Evgeny V. Rebrov, T.a. Nijhuis, Volker Hessel, J Jaap C SchoutenAbstract:Abstract In this paper, the hydrodynamics and the pressure drop of liquid–liquid Slug Flow in round microcapillaries are presented. Two liquid–liquid Flow systems are considered, viz. water-toluene and ethylene glycol/water-toluene. The Slug lengths of the alternating continuous and dispersed phases were measured as a function of the Slug velocity (0.03–0.5 m/s), the organic-to-aqueous Flow ratio (0.1–4.0), and the microcapillary internal diameter (248 and 498 μm). The pressure drop is modeled as the sum of two contributions: the frictional and the interface pressure drop. Two models are presented, viz. the stagnant film model and the moving film model. Both models account for the presence of a thin liquid film between the dispersed phase Slug and the capillary wall. It is found that the film velocity is of negligible influence on the pressure drop. Therefore, the stagnant film model is adequate to accurately predict the liquid–liquid Slug Flow pressure drop. The influence of inertia and the consequent change of the Slug cap curvature are accounted for by modifying Bretherton’s curvature parameter in the interface pressure drop equation. The stagnant film model is in good agreement with experimental data with a mean relative error of less than 7%.
Philipp Rudolf Von Rohr - One of the best experts on this subject based on the ideXlab platform.
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pressure drop of two phase liquid liquid Slug Flow in square microchannels
Chemical Engineering Science, 2018Co-Authors: Agnieszka ładosz, Philipp Rudolf Von RohrAbstract:Abstract Networks of microdevices can be used to form, sort, split and recombine droplets by varying the fluidic resistance of the channels. To facilitate design of such systems we propose two models to calculate pressure drop of liquid-liquid Slug Flow in square microchannels. By approximating a droplet surrounded by liquid film as annular Flow, the moving film model includes the velocity profile in the lubricating layer. In the no-film model, the presence of liquid film is neglected. Pressure drop measurements of water-toluene and water-silicone oil Slug Flow generated in glass/silicon devices of 200 and 400 μ m width serve to validate these two models. We found that the droplet viscosity influences the applicability of the models. Good agreement is obtained for water-toluene Slug Flow, with the average error of 15–20% between the measured and calculated values for both models, proving that the presence of the lubricating film may be neglected for Flows with similar viscosities of both phases. On the contrary, both predictions agree poorly with experiments for silicon oil-water Flow which we attribute to the lower than expected liquid film thickness around the silicon oil droplets. Therefore we use the moving film model to estimate the thickness of the lubricating layer which we find to lie between 0.5% and 0.75% of the channel width, lower than the assumed 2%. Finally we compare the performance of our models against two correlations adapted from literature. We thus demonstrate that our approach allows reliable pressure drop prediction for liquids with similar viscosities and delivers important information on Flow hydrodynamics.
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pressure drop of three phase liquid liquid gas Slug Flow in round microchannels
Microfluidics and Nanofluidics, 2016Co-Authors: Agnieszka ładosz, Eugen Rigger, Philipp Rudolf Von RohrAbstract:In this paper we present a model for the calculation of pressure drop of three-phase liquid–liquid–gas Slug Flow in microcapillaries of a circular cross section. Introduced models consist of terms attributing for frictional and interfacial pressure drop, incorporating the presence of a stagnant thin film at the wall of the channel. Different formulations of the interfacial pressure drop equation were employed, using expressions developed by Bretherton (J Fluid Mech 10:166–188, 1961), Warnier et al. (Microfluid Nanofluid 8:33–45, 2010) or Ratulowski and Chang (Phys Fluids A 1:1642–1655, 1989). Models were validated experimentally using oleic acid–water–nitrogen and heptane–water–nitrogen three-phase Flows in round Teflon or Radel R microchannels of 254- and 508-µm nominal inner diameter, for capillary numbers Cab between 10−4 and 4.9 × 10−1 and Reynolds numbers Re between 0.095 and 300. Best agreement between measured and calculated values of pressure drop, with relative error between −22 and 19 % or −20 and 16 %, is reached for Warnier’s or Ratulowski and Chang’s interfacial pressure drop equation, respectively. The results prove that three-phase Slug Flow pressure drop can be successfully predicted by extending existing two-phase Slug Flow correlations. Good agreement of Bretherton’s equation was reached only at lower Ca numbers, indicating that an extension of the interfacial pressure drop equation as performed by Warnier et al. (Microfluid Nanofluid 8:33–45, 2010) or Ratulowski and Chang (Phys Fluids A 1:1642–1655, 1989) for higher capillary numbers is necessary. Additionally it was demonstrated that pressure drop increases substantially if dry Slug Flow occurs or if microchannels with significant surface roughness are employed. Those influences were not accounted for in the models presented.