The Experts below are selected from a list of 282 Experts worldwide ranked by ideXlab platform
Martin Van Sint Annaland - One of the best experts on this subject based on the ideXlab platform.
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Discrete particle simulations of bubble-to-Emulsion Phase mass transfer in single-bubble fluidized beds
Particuology, 2017Co-Authors: L Lianghui Tan, I Ivo Roghair, Martin Van Sint AnnalandAbstract:A classical Euler–Lagrangian model for gas–solid flows was extended with gas component mass conservation equations and used to obtain fundamental insights into bubble-to-Emulsion Phase mass transfer in bubbling gas–solid fluidized beds. Simulations of injected single rising bubbles under incipient fluidization conditions were carried out, using Geldart-A and -B particles. Phenomena observed in the simulations and those of various theoretical models used to derive phenomenological models were compared to challenge the assumptions underlying the phenomenological models. The bubble-to-Emulsion Phase mass transfer coefficients calculated for the simulations using Geldart-B particles were in a good agreement with predictions made using the Davidson and Harrison (1963) model. The bubble-to-Emulsion Phase mass transfer coefficients for Geldart-A particles were, however, much smaller than the predictions obtained from theoretical models (e.g. Chiba and Kobayashi (1970)). The newly developed model allows a detailed analysis of various hydrodynamic aspects and their effects on the mass transfer characteristics in and around rising bubbles in fluidized beds.
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Determination of the bubble-to-Emulsion Phase mass transfer coefficient in gas-solid fluidized beds using a non-invasive infra-red technique
Chemical Engineering Journal, 2017Co-Authors: J.a. Medrano, Fausto Gallucci, F. Boccia, N. Alfano, Martin Van Sint AnnalandAbstract:The theoretical approach for the bubble-to-Emulsion Phase mass exchange in bubbling gas-solid fluidized beds developed by Davidson and Harrison in the early 60’s is still widely applied in phenomenological models, mainly because of lack of more detailed experimental data to improve the description. In this study a novel infrared transmission technique that allows the direct and non-invasive measurement of gas concentration profiles inside bubbles with a high temporal resolution has been used for the validation of the theoretical description for the gas exchange. At first, the experimental technique has been further improved concerning the selective removal of particles raining through the bubbles, as well as the reconstruction of tracer gas concentration profiles throughout the gas bubble. The bubble-to-Emulsion Phase mass transfer coefficients have been measured by injecting tracer gas bubbles into incipiently fluidized beds and beds at freely-bubbling conditions, for beds consisting of glass beads of different particle size and with different injected bubble diameters. The results show that the Davidson and Harrison approach can reasonably well describe the mass exchange for isolated bubbles injected into a bed at minimum fluidization conditions. However, experiments carried out in a freely bubbling bed have shown that the mass exchange rate is considerably enhanced due to the increased gas through-flow through the bubbles. An empirical correlation (with deviations within only 20%) for the volumetric bubble-to-Emulsion Phase mass transfer coefficient has been developed based on the bubble size and superficial gas velocity, where it is noted that in this work the convective contribution in the mass exchange is dominant.
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Development of a Novel Infrared Camera for Gas Exchange from Bubble-to-Emulsion Phase in Gas-Solid Fluidized Beds
2013Co-Authors: Nhi Dang, Fausto Gallucci, T Tom Kolkman, Martin Van Sint AnnalandAbstract:Gas exchange from bubble-to-Emulsion Phase has been measured by the development of a novel infrared camera combined with a visual high speed camera and the Digital Image Analysis, non-invasively. Experimental findings indicate that the concentration inside the bubble is non-uniform and being diluted at the bottom and in the centre of the bubbles. The gas exchange coefficient is determined from the single Phase model and dominated by the convective flow.
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Novel phenomenological discrete bubble model of freely bubbling dense gas-solid fluidized beds : application to two-dimensional beds
AIChE Journal, 2012Co-Authors: Salman Movahedirad, Martin Van Sint Annaland, Asghar Molaei Dehkordi, Ng Niels Deen, J.a.m. KuipersAbstract:A phenomenological discrete bubble model has been developed for freely bubbling dense gas–solid fluidized beds and validated for a pseudo-two-dimensional fluidized bed. In this model, bubbles are treated as distinct elements and their trajectories are tracked by integrating Newton's equation of motion. The effect of bubble–bubble interactions was taken into account via a modification of the bubble velocity. The Emulsion Phase velocity was obtained as a superposition of the motion induced by individual bubbles, taking into account bubble–bubble interaction. This novel model predicts the bubble size evolution and the pattern of Emulsion Phase circulation satisfactorily. Moreover, the effects of the superficial gas velocity, bubble–bubble interactions, initial bubble diameter, and the bed aspect ratio have been carefully investigated. The simulation results indicate that bubble–bubble interactions have profound influence on both the bubble and Emulsion Phase characteristics. Furthermore, this novel model may become a valuable tool in the design and optimization of fluidized-bed reactors. © 2012 American Institute of Chemical Engineers AIChE J, 2012
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Investigation into the hydrodynamics of gas–solid fluidized beds using particle image velocimetry coupled with digital image analysis
The Canadian Journal of Chemical Engineering, 2008Co-Authors: Jan Albert Laverman, I Ivo Roghair, Martin Van Sint Annaland, Hans KuipersAbstract:The hydrodynamics of a freely bubbling, pseudo 2-D fluidized bed has been investigated experimentally for different bed aspect ratios at different superficial gas velocities by using Particle Image Velocimetry (PIV) combined with Digital Image Analysis (DIA). Coupling of both non-invasive measuring techniques allows us to obtain information on both the bubble behaviour and Emulsion Phase circulation patterns simultaneously. In particular, the combination of DIA with PIV allows to correct for the influence of particle raining through the roof of the bubbles on the time-averaged Emulsion Phase velocity profiles.
Howard N. Richmond - One of the best experts on this subject based on the ideXlab platform.
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The Application of a Mixed Nonionic Surfactant Theory to Transitional Emulsion Phase Inversion
Journal of Colloid and Interface Science, 1994Co-Authors: Brian W. Brooks, Howard N. RichmondAbstract:Abstract Transitional Emulsion Phase inversion in nonionic-surfactant-oil-water systems (nSOW) is brought about by changing the surfactant's affinity for the oil and water Phases. In this paper an analysis is given to explain the linearity and gradient variation of transitional inversion lines (i.e., surfactant affinity difference vs volume fraction of water) in systems containing distributed nonionic surfactants. A simple surfactant partitioning model is derived which can be applied to isothermal transitional inversions where the surfactant's affinity is altered by changing the ratio of a lipophilic and a hydrophilic surfactant in the system. The model describes the partitioning of surfactant between oil, water, and a pseudosurfactant Phase, which represents surfactant at oil-water interfaces. The surfactants used in this study had a distribution of chain lengths; this paper discusses when surfactants of this type may be regarded as single components. In these cases lumped parameters can be used to describe the surfactant's partitioning between the three Phases. The model is applied to a number of nSOW systems and the effect of changing surfactant concentration is examined. A method of obtaining CMCs for mixed lipophilic surfactants is indicated.
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The Application of a Mixed Nonionic Surfactant Theory to Transitional Emulsion Phase Inversion: 2. The Relationship between Surfactant Partitioning and Transitional Inversion—A Thermodynamic Treatment
Journal of Colloid and Interface Science, 1994Co-Authors: Brian W. Brooks, Howard N. RichmondAbstract:Abstract Emulsion Phase inversion in nonionic-surfactant-oil-water systems (nSOW) is directly related to the system's Phase behavior. A transitional inversion occurs when the surfactant's affinity for oil and water is balanced and the system is 3 Phase. The surfactant partitioning model, derived in part 1, is applied to transitional inversion in a number of different nSOW systems at a number of different temperatures. The surfactant partitioning results are used to show how nSOW Phase behaviour and Emulsion types can be related to thermodynamic parameters. It is further shown that transitional inversion points in nSOW systems at different temperatures are dependent on specific values of Δ H and Δ S , the enthalpy and entropy of Phase transfer of the surfactant from bulk to interface respectively; these values depend on the surfactant type. The relationship between the ethyleneoxide chain length of interfacial surfactant and the Phase inversion temperature is discussed also.
Edward K. Levy - One of the best experts on this subject based on the ideXlab platform.
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Solids exchange between the bubble wake and the Emulsion Phase in a two-dimensional gas-fluidized bed
Powder Technology, 1992Co-Authors: E.a. Basesme, Edward K. LevyAbstract:Abstract Information on the rates of solids exchange between the bubble wake and the Emulsion Phase in a gas-fluidized bed is needed in modeling solids mixing and segregation patterns. Experimental data are presented for two-dimensional bubbles, giving wake exchange rate as a function of minimum fluidization velocity and bubble diameter. Comparisons are made with recent theoretical models for wake exchange.
Jamal Chaouki - One of the best experts on this subject based on the ideXlab platform.
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Local characterization of a gas–solid fluidized bed in the presence of thermally induced interparticle forces
Chemical Engineering Science, 2014Co-Authors: Jaber Shabanian, Jamal ChaoukiAbstract:Abstract This article reports the results obtained from an extensive experimental campaign aimed at investigating the effect of interparticle forces (IPFs) on the local flow structure of a gas–solid fluidized bed. A polymer coating approach was used to enhance and control the degree of cohesive IPFs in a gas–solid fluidized bed. In this work, the local transient solids concentration (bed voidage) was carefully measured with the help of an accurate optical fiber probe at different temperatures and gas velocities covering both bubbling and turbulent fluidization regimes. Also, the Radioactive Particle Tracking (RPT) technique was employed to track the trajectory of a tracer mimicking the behavior of solid particles in two systems, one with the least amount of IPFs in the bubbling regime and the other with the highest amount. Experimental results showed that by increasing the level of IPFs in the bed the fixed bed and Emulsion Phase voidage in the bubbling regime increased and demonstrated higher capacities in holding gas inside their structures. In addition, the Emulsion Phase fraction increased, the tendency of the fluidizing gas passing through the bed in the Emulsion Phase enhanced in the bubbling regime, the frequency of the bubble/Emulsion Phase cycle decreased, and the meso-scale transition from bubbling to turbulent fluidization regime delayed until reaching higher superficial gas velocities.
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Characterization of dynamic gas–solid distribution in fluidized beds
Chemical Engineering Journal, 2000Co-Authors: Heping Cui, Navid Mostoufi, Jamal ChaoukiAbstract:Abstract A probability distribution model of the local voidage was proposed to describe and simulate dynamic gas–solid distribution in the bubbling and turbulent fluidized bed reactors. Experiments were carried out in an air-fluidized bed. The bed materials were FCC particles (Geldart A) and irregular sand particles (Geldart B). A cross-optical fiber probe was employed to measure dynamic voidage. The minimum probability method was introduced to identify the division between the Emulsion Phase and the bubble Phase. The statistical analysis indicated that the two particle types employed have extremely different dynamic behaviors corresponding to different gas–solid distributions and the interaction between the bubble and Emulsion Phases. For the FCC particles, the voidage of the Emulsion Phase is very close to that at the minimum fluidization with little effect from the formation and motion of bubbles in bubbling regime, and deviates a little from emf in turbulent regime. For the sand particles, the voidage of the Emulsion Phase differs far from that at the minimum fluidization, and the bubble Phase gradually becomes more dilute from bubbling to turbulent regime. However, for both particles the dynamic voidage fluctuations in the Emulsion Phase and the bubble Phase followed beta distribution under various operating conditions. The probability density functions of the local voidage from emf to 1 showed the continuous double-peak phenomena, one peak for the Emulsion Phase and another for the bubble Phase, and evolved with changing operating conditions and bed position. A particular distribution, called coupled beta distribution, was developed to describe and simulate such probability density function with double peaks and its complex evolution from bubbling to turbulent regime. The quantification of the probability density function then statistically introduced the spatiotemporal two-Phase flow structure.
David Julian Mcclements - One of the best experts on this subject based on the ideXlab platform.
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vitamin e enriched nanoEmulsions formed by Emulsion Phase inversion factors influencing droplet size and stability
Journal of Colloid and Interface Science, 2013Co-Authors: Sinja Mayer, Jochen Weiss, David Julian McclementsAbstract:Abstract There is considerable interest in using nanoEmulsions as delivery systems for lipophilic bioactive ingredients, such as oil-soluble vitamins. NanoEmulsions can be fabricated using either high-energy or low-energy methods, but the latter offer advantages in terms of low cost, higher energy efficiency, and simplicity of implementation. In this study, the Emulsion Phase inversion (EPI) method was used to produce food-grade nanoEmulsions enriched with vitamin E acetate. The EPI method simply involves titrating water into a mixture containing oil and surfactant, which initially leads to the formation of a water-in-oil Emulsion that then inverts into an oil-in-water Emulsion. Oil composition, surfactant type, and surfactant-to-oil ratio (SOR) were all found to influence the particle size distribution of the systems produced. NanoEmulsions with a mean particle diameter of 40 nm could be produced at a final system composition of 2 wt% MCT, 8 wt% vitamin E acetate, and 20 wt% Tween 80. The EPI method was shown to be unsuitable for producing nanoEmulsions from label-friendly surfactants, such as Quillaja saponin, whey protein, casein, and sucrose monoesters. The EPI method was more effective at producing nanoEmulsions at high SOR than microfluidization, but much less effective at low SOR.
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low energy formation of edible nanoEmulsions factors influencing droplet size produced by Emulsion Phase inversion
Journal of Colloid and Interface Science, 2012Co-Authors: Felix Ostertag, Jochen Weiss, David Julian McclementsAbstract:NanoEmulsions can be used for the encapsulation and oral delivery of bioactive lipophilic components, such as nutraceuticals and pharmaceuticals. There is growing interest in the utilization of low-energy methods to produce edible nanoEmulsions. In this study, we examined the influence of system composition and preparation conditions on the formation of edible nanoEmulsions by the Emulsion Phase inversion (EPI) method. The EPI method involves titrating an aqueous Phase (water) into an organic Phase (oil+hydrophilic surfactant). The influence of oil type, surfactant type, surfactant-to-oil ratio (SOR), and initial surfactant location on the particle size distributions of the Emulsions was studied. The droplet size produced by this method depended on: (i) oil type: medium chain triglycerides (MCT)
triglycerides (olive, grape, sesame, peanut and canola oils); (ii) surfactant type: Tween 80 surfactant concentration: smaller droplets were produced at higher SOR; (iv) surfactant location: surfactant initially in oil<surfactant initially in water. The low energy method (EPI) was also compared to a high energy method (microfluidization). Small droplets (d<160 nm) could be produced by both methods, but much less surfactant was needed for the high energy method (SOR≥0.1) than the low energy method (SOR≥0.7). -
Low-energy formation of edible nanoEmulsions: Factors influencing droplet size produced by Emulsion Phase inversion
Journal of colloid and interface science, 2012Co-Authors: Felix Ostertag, Jochen Weiss, David Julian McclementsAbstract:NanoEmulsions can be used for the encapsulation and oral delivery of bioactive lipophilic components, such as nutraceuticals and pharmaceuticals. There is growing interest in the utilization of low-energy methods to produce edible nanoEmulsions. In this study, we examined the influence of system composition and preparation conditions on the formation of edible nanoEmulsions by the Emulsion Phase inversion (EPI) method. The EPI method involves titrating an aqueous Phase (water) into an organic Phase (oil+hydrophilic surfactant). The influence of oil type, surfactant type, surfactant-to-oil ratio (SOR), and initial surfactant location on the particle size distributions of the Emulsions was studied. The droplet size produced by this method depended on: (i) oil type: medium chain triglycerides (MCT)