Based on experiments with single air bubbles rising in stagnant non-Newtonian fluids, an innovative model containing the aspect ratio (E) and two parameters (alpha, beta) was proposed and proved to be capable of characterizing the bubble shape from spherical/ellipsoidal to prolate/oblate-tear with good accuracy. Several impacts on bubble deformation were investigated, involving the rheological properties of the fluids and different forces exerted on the bubble, which were quantified by multiple dimensionless numbers (e.g., Reynolds, Eotvos, and Deborah number). Within a wide range, the empirical correlations were obtained for parameter beta, and between alpha and beta. Together with the shape model, a complete system was set up for bubble shape characterization and prediction that will provide new ideas for future studies on bubble hydrodynamics.

Several studies report that dolphins, either captive or wild, can expel air from their blowhole to form ring bubbles. By means of an experimental setup consisting of an orifice coupled to a computer-controlled solenoid valve to simulate the dolphin's blowhole and a vessel as the lungs, we examined the formation mechanism of a ring bubble under varying experimental conditions. With a better record than the most talented dolphin, we show that two aspects were demonstrated as essential to the successful generation of a ring bubble in water: the valve's opening duration, and the pressure inside the vessel. The present findings suggest that during ring bubble production, dolphins are likely to anticipate their action by both adjusting a suitable air pressure inside their lungs and controlling their muscular flap for an adequate opening timing of their blowhole. This could provide some evidence in favour of suggested cetaceans' self-control capacities.

A vehicle in movement causes the re-suspension of particulate matter present on roads. Of concern in certain urban situations, this source of emission can become considerable in an industrial context or near industrial sites. The aim of the works performed in the framework of this study is to provide elements of response to the problem of road dust emissions caused by vehicle traffic in industrial situations. The technical solution to reduce the road dust dispersion proposed in this study is based on the collection particle by forced convection. Experiments performed under laboratory conditions using simplified configurations demonstrated the pertinence of this technique, with interesting collection efficiencies for a reference aerosol. According to the configurations studied, it was possible to capture up to 90% of an aerosol introduced downstream of the point of contact between the wheel and the ground. These observations were confirmed by tests carried out on an outdoor track with an industrial vehicle, even if the real operating conditions were not strictly similar with those applied at the laboratory.

This article, the second of a series, is devoted to the design of U-type ladder manifolds capable of exhibiting a close-to-uniform distribution of the flow between all the cross-channels. This article builds on the analytical and numerical results of the previous part but brings the geometric properties of the network in the foreground. Two situations are considered: the first being with constant channel diameters for which the diameter ratios of distributor and collector are sought which minimize the dispersion of the cross-flow distribution. The second situation considers tapering the distributor or collector diameter along their lengths, and the optimal tapering is sought.

The aim of the present study is the characterisation of the fine particle dispersion in the wake of an isolated wheel of vehicle. The work performed in this study lies within the description and the understanding of the transport of re-suspended road dust emissions induced by the circulation of vehicles. The behaviour of PM2.5 fraction in the field near to the wheel was investigated for two rotating velocities and two types of tyres, both experimentally and using Computational Fluid Dynamics (CFD). Experiments were carried out in a wind tunnel equipped by moving ground with carefully controlled aerodynamic conditions. CFD methods were used to calculate the velocity field of the air flow around a rotating wheel and to determine the trajectories for different particle sizes. The experiments reveal a strong impact of the nature of tyre both on the velocity field of the flow and the particle dispersion in the near wake of the wheel. In this simple case of an isolated wheel, the simulated flow was quite similar to the corresponding experimental results, although prediction of the flow located in the region of the point of contact between the wheel and the ground could be improved.

This article proposes a theoretical overview of the distribution of fluid flow through manifolds composed of parallel channels connected through T-junctions to a distributor and to a collector channel, thus composing a ladder-like network. Such networks are used in solar heaters, fuel cells, heat exchanger plates, and other engineering devices, one issue being to achieve a nearly uniform distribution. This first part focuses on the discrete mesoscopic momentum and energy balances governing the T-junctions, with particular attention to the empirical, flow-rate and geometry dependent, pressure change coefficients. By "mesoscopic", it is meant that the control volume for the balance equations includes the junction zone and that the local flow-field in that zone is not described. The existing results and correlations for these coefficients are reviewed, compared, and synthesized.In keeping with the discrete character of the channel network, the overall network relations are compacted as a single non-linear finite-difference equation relating the flow-rates in the different segments of the distributor. This formulation is suitable for convenient numerical resolution even when all the coefficients are allowed to vary with local conditions. The conditions for simplifications, such as assuming constancy of certain coefficients, are carefully investigated. A number of approximate analytical, semi-explicit or explicit solutions are constructed. In particular, an original view of the structure of these solutions is proposed, relying on an invariance property which is demonstrated, and on the analogy with the classical McCabe-Thiele construction in chemical engineering. These approximations are compared to exact numerical solutions.

The gas-liquid swirl flow in a gas-liquid cylindrical cyclone separator has been characterized first qualitatively by flow visualizations. The emerged findings were then confirmed quantitatively by Laser Doppler Velocimetry measurements. The vortex core presents a very complex hydrodynamics, characterized by an alternation between a laminar and a turbulent state. The laminar regime is associated with velocities pointing in the same direction as the mean flow, while the turbulent state induces velocities in the opposite direction, i.e. a flow reversal. These observations give a first understanding of the origin of the double flow reversal regime that is encountered in swirl flows. It is shown that this flow structure appears for high swirl intensities, and results from a frequent laminarization of the vortex core. Results show that, contrary to the commonly assumed hypothesis, this flow structure is associated with good separation performance of the cyclone. Accordingly, we propose the use of multiple tangential inlets to generate the swirl motion in the cyclone, which is supposed to favor the double flow reversal regime, and thus, improve the separation efficiency. (C) 2014 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

A swimming pool can be considered as a chemical reactor with specific hydraulic and macro-mixing characteristics. The nature of flow into the pool depends on various characteristics, such as water inlets and outlets (number and position), pool geometry, and flow rate. This study investigates how swimming pool design affects hydraulic behavior based on experimental and computational fluid dynamics studies (CFD). This paper does not describe the hydraulic behavior of all existing swimming pools, however the cases studied here are representative of pool designs widely used in Europe and the United States. The model developed, based on the principle of a stirred reactor, could be used as a first approach in describing the hydraulic behavior of regular pools. This model is suitable for the study of physical and chemical phenomena with long characteristic times. Other, more advanced, models were shown to be more suitable to the case of fast chemical processes.

The present work reports a multiscale approach to describe the dynamics of a chain of bubbles rising in non-Newtonian fluids. By means of the particle image velocimetry (PIV) and the lattice Boltzmann (LB) simulation, a deep understanding of the complex flow pattern around a single bubble is gained at microscale. The interactions and coalescences between bubbles rising in non-Newtonian fluids are experimentally investigated by the PIV measurements, birefringence, and rheological characterization for both an isolated bubble and a chain of bubbles formed from a submerged orifice. Two aspects are identified as central to interactions and coalescence: the stress creation by the passage of bubbles and their relaxation due to the fluid's memory. This competition between the creation and relaxation of stresses displays nonlinear complex dynamics. Along with the detailed knowledge around a single bubble, these fundamental mechanisms governing the bubbles' collective behavior in a train of bubbles at mesoscale leads to cognitive modeling on the basis of behavioral rules. By simulating bubbles as adaptive agents with the surrounding fluid via averaged residual stresses, model predictions for consecutive coalescence between a great number of bubbles compare very satisfactorily with the experimental investigation at macroscale.

This paper constitutes a preliminary study of the two-phase flow in a Gas-Liquid Cylindrical Cyclone (GLCC 1) separator. A GLCC consists in a vertical pipe with a downward inclined tangential inlet. The incoming flow forms a swirling motion producing a centrifugal force. The gas and liquid are thus separated due to both centrifugal and gravity forces. Therefore the separation efficiency is higher than for conventional vessel type separators, allowing more compactness.In this study, the aim is to better understand the swirling hydrodynamics of this separator via CFD simulations. Therefore, the single-phase hydrodynamics is calculated for swirling flows generated by means of tangential injection(s) in a straight pipe. Geometry and flow conditions are chosen according to the experimental study of Erdal (2001a), who performed local measurements of the axial and tangential velocities. BANS, URANS and LES simulations are carried out using different turbulence models and different near wall treatments.Among the Reynolds Averaged Navier-Stokes (RANS) models, the high-Reynolds realizable kappa-epsilon model performs the best for predicting the local mean axial and tangential velocities. Its results are as good as the LES ones when the fluid is injected through only one inlet, while LES predicted flow is closer to the experimental one for two inlets. Numerical results also show that, contrary to the common approximation of the literature, the radial velocity magnitude is not negligible. The vortex core precession is well predicted by the simulations, which show that its direction is the opposite of the swirl one. We think that the growth of the turbulence kinetic energy in the core of the flow is directly linked to this phenomenon. Finally computations are conducted to investigate the effect of the inlet geometry on the cyclone hydrodynamics. According to simulations, the rectangular inlet performs better than a circular one, since it reduces the vortex distortion, which is supposed to improve the separation efficiency. (C) 2011 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

Numerous sources of liquid aerosols are to be found in industrial environments. Such aerosols may, for instance, be cutting fluids, pesticides, etc., that are harmful or even toxic to humans. To control and reduce worker exposure to potentially toxic aerosols, these latter are usually filtered through fibrous filters. When non-saturated air traverses a clogged filter, however, the drops deposited on the fibers may evaporate. Consequently, workers are exposed to greater amounts of more concentrated vapors than the initial state of the filtered aerosol. Furthermore, exposure readings are distorted by an artifact that may be significant. This study offers an experimental approach to long-term monitoring of the evaporation of a semi-volatile n-hexadecane liquid aerosol deposited on filters of varying efficiency. Results were modeled using two semi-empirical models for identifying the basic parameters of liquid aerosol evaporation on fibers. For the first time ever it has been demonstrated that the Fick's first law, as previously suggested by models proposed in the literature, does not control evaporation kinetic.

In this paper, the idea of coupling constructal distributors/collectors with a mini crossflow heat exchanger (MCHE) to solve the problem of flow maldistribution is presented. After a brief description of the design and scaling laws of the constructal distributor, experimental and simulation results have been discussed to investigate relations among flow distribution, heat transfer and pressure drop. It is shown that the introduction of constructal distributors and/or collectors could improve the quality of fluid distribution and consequently lead to heat transfer intensification of the MCHE, but it also results in higher pressure drops. Different assembly configurations involving distributor, heat exchanger and collector have also been compared. The configuration where the inlet is equipped with a conventional pyramid distributor and the outlet is equipped with a constructal collector (Apec) shows a relatively higher thermal performance as well as low pressure drops in our cases considered.

A new diagnosis method for regime identification in bubble columns and airlift reactors based on a theoretical analysis of the auto-correlation function (ACF) of wall pressure fluctuations is proposed. It yields quantitative information, such as a characteristic time and a characteristic frequency of the two-phase flow, which are closely related to the flow structure in the prevailing regime. This method is shown to be simple, low-cost, reliable and efficient and has been applied successfully to a bubble column and an external loop airlift reactor. Experimental data on both reactors are shown to be in good agreement with theoretically predicted values. The order of magnitude of the characteristic time can be used for regime identification. Combined with an analysis of the cross-correlation function (CCF) of two signals recorded simultaneously, the method is also able to yield an estimate of the axial dimension of the flow structures. This analysis is, therefore, promising for regime identification and flow structure characterisation in industrial equipment.

The volumetric mass transfer coefficientkLa in gas—liquid contacting equipment is in most cases determined by the oxygen absorption or desorption technique; the hydrazine oxidation technique is an interesting alternative to these physical techniques; it has not been widely used, mainly because the available catalysts presented severe drawbacks. An original catalyst is proposed which allows the determination ofkLa with more or less coalescing liquids. The order of magnitude of the rate constant is determined at different catalyst concentrations, allowing the use of hydrazine oxidation by air as a chemical reaction which is slow in the mass transfer film but fast in the bulk of the liquid. Examples of determinations ofkLa in very different contactors are presented (liquid motivated ejector, centrifugal film absorber, cocurrent upflow packed-bed column).

Les modeles theoriques et correlations empiriques existants actuellement sont incapables de prevoir correctement ľinfluence de la pression sur le deplacement de la transition entre les regimes ruisselant et pulse (Trp) dans les reacteurs catalytiques a lit fixe arrose (Rclfa). Base sur les donnees disponibles a ce jour de la Trp a haute pression, le diagramme de Charpentier modifie que nous proposons ici, constitue un moyen direct pour quantifier ľeffet de la pression dans le cas de systemes non-moussants. The effect of pressure on transition displacement between trickle and pulsed regimes (TPR: trickle-pulsed transition) in catalytic trickle bed reactors (CTBR) is not properly predicted by existing theoretical models and empirical correlations. Based on high pressure TPR data available to date, a modified Charpentier diagram is proposed to quantify directly the effect of pressure in non-foaming systems.

The influence of pressure on gas-liquid interfacial area in cocurrent trickle flow fixed bed reactors is investigated. Interfacial areas have been determined from diethanolamine carbamation of aqueous more or less viscous solutions of ethylene glycol for pressures up to 3.1 MPa in a 0.395m-height and 23mm-ID column packed with hydrophilized polypropylene extrudates, porous carbon cylinders or glass beads. At gas superficial velocities less than 0.02m/s, interfacial areas are found to be pressure-independent, allowing for an acceptable estimation at atmospheric pressure. However, above this limit, even if the flow regime is still trickling, gas-liquid interfacial area increases with pressure for constant gas and liquid velocities. These findings are tentatively explained by the influence of gas inertia on break-up of bubbles trapped in the liquid films trickling over the particles.

The flow between eccentric rotating cylinders when either the outer or inner cylinder is stationary is analysed both for the creeping flow approximation and for the case when inertial effects are not negligible. Numerical solutions are obtained using a finite difference ADI scheme and a fine orthogonal bipolar coordinate grid. When the centres of the two cylinders are far enough, a two‐dimensional recirculation zone appears in the region where the gap spacing is greatest. On increasing the eccentricity, the recirculation zone becomes bigger and the separation and reattachment points move towards the region of narrowest gap. Further increase of the eccentricity results in the formation of a saddle point between the cylinders at the region of narrowest gap. As the Reynolds numbers increases, inertial effects modify slightly the recirculation region; the separation point moves upstream and the reattachment point moves downstream when either the inner or the outer cylinder rotate.

AIChE JournalVolume 37, Issue 7 p. 1109-1112 R & D Note Liquid saturation data in trickle beds operating under elevated pressure Faïcal Larachi, Faïcal Larachi Laboratoire des Sciences du Génie Chimique, CNRS-ENSIC-INPL, BP 451, 54001 Nancy cédex, FranceSearch for more papers by this authorAndré Laurent, André Laurent Laboratoire des Sciences du Génie Chimique, CNRS-ENSIC-INPL, BP 451, 54001 Nancy cédex, FranceSearch for more papers by this authorNoël Midoux, Noël Midoux Laboratoire des Sciences du Génie Chimique, CNRS-ENSIC-INPL, BP 451, 54001 Nancy cédex, FranceSearch for more papers by this authorGabriel Wild, Gabriel Wild Laboratoire des Sciences du Génie Chimique, CNRS-ENSIC-INPL, BP 451, 54001 Nancy cédex, FranceSearch for more papers by this author Faïcal Larachi, Faïcal Larachi Laboratoire des Sciences du Génie Chimique, CNRS-ENSIC-INPL, BP 451, 54001 Nancy cédex, FranceSearch for more papers by this authorAndré Laurent, André Laurent Laboratoire des Sciences du Génie Chimique, CNRS-ENSIC-INPL, BP 451, 54001 Nancy cédex, FranceSearch for more papers by this authorNoël Midoux, Noël Midoux Laboratoire des Sciences du Génie Chimique, CNRS-ENSIC-INPL, BP 451, 54001 Nancy cédex, FranceSearch for more papers by this authorGabriel Wild, Gabriel Wild Laboratoire des Sciences du Génie Chimique, CNRS-ENSIC-INPL, BP 451, 54001 Nancy cédex, FranceSearch for more papers by this author First published: July 1991 https://doi.org/10.1002/aic.690370717Citations: 10AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Literature Cited Abbott, M. D., G. R., Moore, and J. L. Ralph, Proc. ABG Conf., paper S4, (1967). Aris, R., “Notes on the Diffusion-Type Model for Longitudinal Mixing in Flow,” Chem. Eng. Sci., 9, 266 (1959). Blok, J. R., and A. A. H., Drinkenburg, “ Hydrodynamics and Mass Transfer in Pulsing Trickle-Bed Columns,” ACS Symp. Ser., No. 196, Chemical Reaction Engineering, Washington, DC, p. 393 (1982). Hasseni, W., A., Laurent, N. Midoux, and J. C. Charpentier, “Régimes d'Écoulement dans un Réacteur Catalytique à Lit Fixe Arrosé Fonctionnant à Cocourant de Gaz et de Liquide vers le Bas,” Entropie, 137/138, 127 (1987). Kohler, M., and W., Richarz, “Investigation of Liquid Holdup in Trickle-Bed Reactors,” Ger. Chem. Eng., 8, 295 (1985). Nauman, E. B., and B. A., Buffham, “ Mixing in Continuous Flow Systems,” Wiley Interscience (1983). Shah, Y. T., Gas-Liquid-Solid Reactor Design, McGraw-Hill, New York (1979). Wammes, W. J. A., S. J., Mechielsen, and K. R. Westerterp, “The Influence of the Reactor Pressure on the Hydrodynamics in a Cocurrent Gas-Liquid Trickle-Bed Reactor,” Chem. Eng. Sci., 45, 2247 (1990a). Wammes, W. J. A., S. J., Mechielsen, and K. R. Westerterp, “The Transition between Trickle Flow and Pulse Flow in a Cocurrent Gas-Liquid Trickle-Bed Reactor at Elevated Pressure,” Chem. Eng. Sci., 45, 3149 (1990b). Wammes, W. J. A., S. J., Mechielsen, and K. R. Westerterp, “The Influence of Pressure on the Liquid Hold-up in a Cocurrent Gas-Liquid Trickle-Bed Reactor Operating at Low Gas Velocities,” Chem. Eng. Sci., 46, 409 (1991). Citing Literature Volume37, Issue7July 1991Pages 1109-1112 ReferencesRelatedInformation

Chemie Ingenieur TechnikVolume 61, Issue 9 p. 733-736 Kurzmitteilungen Hydrodynamik und Wärmeübergang in zweiphasig im Aufstrom durchströmten Festbettreaktoren Dipl.-Ing. Stephan Gutsche, Dipl.-Ing. Stephan Gutsche Laboratoire des Sciences du Génie Chimique (LSGC) CNRS-ENSIC I.N.P.L., B.P. 451, 1 rue Grandville, F-54001 Nancy CEDEXSearch for more papers by this authorDr.-Ing. Gabriel Wild, Dr.-Ing. Gabriel Wild Laboratoire des Sciences du Génie Chimique (LSGC) CNRS-ENSIC I.N.P.L., B.P. 451, 1 rue Grandville, F-54001 Nancy CEDEXSearch for more papers by this authorProf. Dr. Noël Midoux, Prof. Dr. Noël Midoux Laboratoire des Sciences du Génie Chimique (LSGC) CNRS-ENSIC I.N.P.L., B.P. 451, 1 rue Grandville, F-54001 Nancy CEDEXSearch for more papers by this authorProf. Dr.-Ing. Holger Martin, Prof. Dr.-Ing. Holger Martin Institut für Thermische Verfahrenstechnik, Univ. Karlsruhe (TH), Kaiserstr. 12, 7500 KarlsruheSearch for more papers by this author Dipl.-Ing. Stephan Gutsche, Dipl.-Ing. Stephan Gutsche Laboratoire des Sciences du Génie Chimique (LSGC) CNRS-ENSIC I.N.P.L., B.P. 451, 1 rue Grandville, F-54001 Nancy CEDEXSearch for more papers by this authorDr.-Ing. Gabriel Wild, Dr.-Ing. Gabriel Wild Laboratoire des Sciences du Génie Chimique (LSGC) CNRS-ENSIC I.N.P.L., B.P. 451, 1 rue Grandville, F-54001 Nancy CEDEXSearch for more papers by this authorProf. Dr. Noël Midoux, Prof. Dr. Noël Midoux Laboratoire des Sciences du Génie Chimique (LSGC) CNRS-ENSIC I.N.P.L., B.P. 451, 1 rue Grandville, F-54001 Nancy CEDEXSearch for more papers by this authorProf. Dr.-Ing. Holger Martin, Prof. Dr.-Ing. Holger Martin Institut für Thermische Verfahrenstechnik, Univ. Karlsruhe (TH), Kaiserstr. 12, 7500 KarlsruheSearch for more papers by this author First published: 18 September 1989 https://doi.org/10.1002/cite.330610914Citations: 3AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat Literatur 1 Carslaw, H. J.; Jaeger, J. C.: Conduction of Heat in Solids, 2. Aufl., Oxford University Press, Oxford 1959. 2 Schlünder, E.-U.: Chem.-Ing.-Tech. 38 (1966) S. 1161. 3 Bauer, R.: VDI-Wärmeatlas, 4. Aufl., Abschn. De 10–19, VDI – Verlag, Düsseldorf 1984. 4 Zehner, P.; Schlünder, E.-U.: Chem.-Ing.-Tech. 45 (1973) S. 272. 5 Schlünder, E.-U.; Tsotsas, E.: Wärmeübertragung in Festbetten, durchmischten Schüttgütern und Wirbelschichten, Georg Thieme Verlag, Stuttgart – New York 1988. 6 Villermaux, J.: Génie de la Réaction Chimique, 2. Aufl., Technique & Documentation Lavoisier, Paris 1985. 7 Hashimoto, K.; Muroyama, K.; Fujiyoshi, K.; Nagata, N.: Heat Transfer Jpn. Res. 6 (1977) S. 44. Citing Literature Volume61, Issue918 September 1989Pages 733-736 ReferencesRelatedInformation

La désorption de gaz à partir de solutions sursaturées est un phénomène qui intervient très fréquemment dans les industries chimique, biochimique et alimentaire : détente de solutions saturées, fermentations, réactions entre composants liquides conduisant à des produits volatiles et peu solubles, électrolyses, réactions parasites lors d'électro-synthèse. La désorption peut avoir lieu de manière diffusionnelle (c'est-à-dire sans formation de bulles), ou de manière nucléée. Si le premier type a été étudié par plusieurs auteurs, le second n'a fait l'objet que de quelques rares travaux soit purement empiriques et non généralisables, soit théoriques et difficilement applicables. Les auteurs présentent l'état des connaissances dans ce domaine et indiquent quelques voies de recherche d'intérêt.