|
| ||
|
|
||
Bubble Size Distribution (bubble + size_distribution)
Selected AbstractsAir Inclusion Into a Model Cake Batter Using a Pressure Whisk: Development of Gas Hold-up and Bubble Size DistributionJOURNAL OF FOOD SCIENCE, Issue 8 2001A.H. Massey ABSTRACT: This paper investigates the development of gas hold-up (that is, gas volume fraction) and bubble size distribution in a model cake batter, which is aerated in a pressure whisk. With increasing aeration time, the hold-up was found to pass through a maximum before approaching a uniform steady state value. A mathematical model that describes this profile has been developed. Bubble size distribution was found to be adequately described by a log normal distribution function with mean size varying between 20 and 50 ,m. Higher pressures were found to increase hold-up and mean bubble size, whereas higher whisk speeds reduced the time required to achieve a given hold-up and the final mean bubble size. [source] Bubble Size Distribution in Oil-Based Bubble ColumnsCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 11 2008S.-S. Homayouni Abstract A practical population balance model was used to evaluate the bubble size distribution in a bubble column. In addition, the bubble size distribution in the bubble column was measured at different gas velocities by photography and analysis of the pictures. Four types of liquid, i.e., water and three petroleum-based liquids, were used in the experiments. The gas phase was air. It was found that the existing models in the literature are not able to satisfactorily predict the experimentally measured bubble size distribution. The model can be corrected by applying a correction factor to the energy dissipation rate. The corrected model fits the experimental bubble size distribution considerably better than the existing models. The variation of this correction factor is reported for different systems at different gas velocities. [source] Air Inclusion Into a Model Cake Batter Using a Pressure Whisk: Development of Gas Hold-up and Bubble Size DistributionJOURNAL OF FOOD SCIENCE, Issue 8 2001A.H. Massey ABSTRACT: This paper investigates the development of gas hold-up (that is, gas volume fraction) and bubble size distribution in a model cake batter, which is aerated in a pressure whisk. With increasing aeration time, the hold-up was found to pass through a maximum before approaching a uniform steady state value. A mathematical model that describes this profile has been developed. Bubble size distribution was found to be adequately described by a log normal distribution function with mean size varying between 20 and 50 ,m. Higher pressures were found to increase hold-up and mean bubble size, whereas higher whisk speeds reduced the time required to achieve a given hold-up and the final mean bubble size. [source] Bubble size distribution modeling in stirred gas,liquid reactors with QMOM augmented by a new correction algorithmAICHE JOURNAL, Issue 1 2010Miriam Petitti Abstract Local gas hold-up and bubbles size distributions have been modeled and validated against experimental data in a stirred gas,liquid reactor, considering two different spargers. An Eulerian multifluid approach coupled with a population balance model (PBM) has been employed to describe the evolution of the bubble size distribution due to break-up and coalescence. The PBM has been solved by resorting to the quadrature method of moments, implemented through user defined functions in the commercial computational fluid dynamics code Fluent v. 6.2. To overcome divergence issues caused by moments corruption, due to numerical problems, a correction scheme for the moments has been implemented; simulation results prove that it plays a crucial role for the stability and the accuracy of the overall approach. Very good agreements between experimental data and simulations predictions are obtained, for a unique set of break-up and coalescence kinetic constants, in a wide range of operating conditions. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] Air Inclusion Into a Model Cake Batter Using a Pressure Whisk: Development of Gas Hold-up and Bubble Size DistributionJOURNAL OF FOOD SCIENCE, Issue 8 2001A.H. Massey ABSTRACT: This paper investigates the development of gas hold-up (that is, gas volume fraction) and bubble size distribution in a model cake batter, which is aerated in a pressure whisk. With increasing aeration time, the hold-up was found to pass through a maximum before approaching a uniform steady state value. A mathematical model that describes this profile has been developed. Bubble size distribution was found to be adequately described by a log normal distribution function with mean size varying between 20 and 50 ,m. Higher pressures were found to increase hold-up and mean bubble size, whereas higher whisk speeds reduced the time required to achieve a given hold-up and the final mean bubble size. [source] Bubble size distribution modeling in stirred gas,liquid reactors with QMOM augmented by a new correction algorithmAICHE JOURNAL, Issue 1 2010Miriam Petitti Abstract Local gas hold-up and bubbles size distributions have been modeled and validated against experimental data in a stirred gas,liquid reactor, considering two different spargers. An Eulerian multifluid approach coupled with a population balance model (PBM) has been employed to describe the evolution of the bubble size distribution due to break-up and coalescence. The PBM has been solved by resorting to the quadrature method of moments, implemented through user defined functions in the commercial computational fluid dynamics code Fluent v. 6.2. To overcome divergence issues caused by moments corruption, due to numerical problems, a correction scheme for the moments has been implemented; simulation results prove that it plays a crucial role for the stability and the accuracy of the overall approach. Very good agreements between experimental data and simulations predictions are obtained, for a unique set of break-up and coalescence kinetic constants, in a wide range of operating conditions. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] A CFD,PBM coupled model for gas,liquid flowsAICHE JOURNAL, Issue 1 2006Tiefeng Wang Abstract A computational fluid dynamics,population balance model (CFD-PBM) coupled model was developed that combines the advantages of CFD to calculate the entire flow field and of the PBM to calculate the local bubble size distribution. Bubble coalescence and breakup were taken into account to determine the evolution of the bubble size. Different bubble breakup and coalescence models were compared. An algorithm was proposed for computing the parameters based on the bubble size distribution, including the drag force, transverse lift force, wall lubrication force, turbulent dispersion force, and bubble-induced turbulence. With the bubble breakup and coalescence models and the interphase force formulations in this work, the CFD-PBM coupled model can give a unified description for both the homogeneous and the heterogeneous regimes. Good agreement was obtained with the experimental results for the gas holdup, liquid velocity, and bubble size distribution. © 2005 American Institute of Chemical Engineers AIChE J, 2006 [source] Simulations of Bubble Column Reactors Using a Volume of Fluid Approach: Effect of Air DistributorTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2007M. Abid Akhtar Abstract Two- and three-dimensional numerical simulations have been performed on a laboratory scale bubble column reactor using a volume-of-fluid approach. The effect of hole-size and superficial gas velocity on the bubble size distribution and their trajectories has been investigated on a 20 cm diameter and 1 m high cylindrical reactor. All simulations were performed in a transient manner using a FLUENT solver. Surface tension between two phases has been modelled as a body force with a constant value. Turbulence was modelled using the k-, turbulence approach. A comparison between simulation predictions and the reported experimental studies has shown a good agreement. On a effectué des simulations numériques bi et tridimensionnelles dans un réacteur à colonne à bulles à l'échelle de laboratoire à l'aide d'une approche volume-de-fluide. L'effet de la taille du trou et de la vitesse de gaz superficielle sur la distribution de tailles des bulles et leurs trajectoires a été étudié dans un réacteur cylindrique de 20 cm de diamètre et de 1 m de hauteur. Toutes les simulations ont été réalisées selon un mode transitoire à l'aide du logiciel FLUENT. La tension de surface entre deux phases a été modélisée comme une force volumique avec une valeur constante. La turbulence a été modélisée par la méthode de turbulence k-,. Une comparaison entre les prédictions des simulations et les études expérimentales mentionnées montre un bon accord. [source] Combined PIV/PTV-Measurements for the Analysis of Bubble Interactions and Coalescence in a Turbulent FlowTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 3-4 2003Dirk Bröder Abstract In order to allow more reliable modeling of coalescence processes in turbulent bubbly flows, detailed experiments in a double loop reactor were performed. Narrow and essentially monomodal bubble size distributions in the range of 2 to 4 mm were created. For simultaneous measurements of bubble size, bubble velocity and liquid velocity a combined system of PIV and PTV was developed and applied. It was possible to determine bubble size distributions and mean, as well as fluctuating velocities for both phases. The spatial changes of the bubble size distribution, due to the influence of bubble coalescence, was analyzed and coalescence rates were calculated. Afin d'améliorer la fiabilité de la modélisation des procédés de coalescence dans les écoulements bouillonnants turbulents, des expériences poussées ont été menées dans un réacteur à double boucle. Des distributions de taille des bulles étroites, essentiellement monodisperses, dans la gamme de 2 à 4 mm, ont été créées. Pour les mesures simultanées de la taille des bulles, de la vitesse des bulles et de la vitesse du liquide, on a mis au point et appliqué un système combiné de PIV et PTV. Il a été possible de déterminer les distributions de taille des bulles et la moyenne mais également les vitesses fluctuantes pour les deux phases. Les changements spatiaux de la distribution de la taille des bulles dus à l'influence de la coalescence des bulles ont été analysés et les vitesses de coalescence ont été calculées. [source] Numerical Simulation of Absorbing CO2 with Ionic LiquidsCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 10 2010X. Wang Abstract Although separating CO2 from flue gas with ionic liquids has been regarded as a new and effective method, the mass transfer properties of CO2 absorption in these solvents have not been researched. In this paper, a coupled computational fluid dynamic (CFD) model and population balance model (PBM) was applied to study the mass transfer properties for capturing CO2 with ionic liquids solvents. The numerical simulation was performed using the Fluent code. Considering the unique properties of ionic liquids, the Eulerian-Eulerian two-flow model with a new drag coefficient correlation was employed for the gas-liquid fluid dynamic simulation. The gas holdup, interfacial area, and bubble size distribution in the bubble column reactor were predicted. The mass transfer coefficients were estimated with Higbie's penetration model. Furthermore, the velocity field and pressure field in the reactor were also predicted in this paper. [source] Bubble Size Distribution in Oil-Based Bubble ColumnsCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 11 2008S.-S. Homayouni Abstract A practical population balance model was used to evaluate the bubble size distribution in a bubble column. In addition, the bubble size distribution in the bubble column was measured at different gas velocities by photography and analysis of the pictures. Four types of liquid, i.e., water and three petroleum-based liquids, were used in the experiments. The gas phase was air. It was found that the existing models in the literature are not able to satisfactorily predict the experimentally measured bubble size distribution. The model can be corrected by applying a correction factor to the energy dissipation rate. The corrected model fits the experimental bubble size distribution considerably better than the existing models. The variation of this correction factor is reported for different systems at different gas velocities. [source] Effect of Suspended Liposomes on Hydrodynamic and Oxygen Transfer Properties in a Mini-Scale External Loop Airlift Bubble ColumnCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 9 2006M. Yoshimoto Abstract The circulating liquid velocity, gas holdup, bubble size distribution, and liquid phase oxygen transfer coefficient were measured in a mini-scale external loop airlift bubble column (MELBC) with the liquid volume suspending enzyme-free liposomes of varying diameters. These values were compared to those for liposome-free MELBC, normal bubble column (NBC), and a larger scale airlift column. The liposomes suspended in the MELBC are incorporated into the liquid film around the bubbles, leading to the development of a foam layer, where the incorporated liposomes exert negligible effect on the oxygen transfer in the film. [source] Applications of Defocusing DPIV to Bubbly Flow MeasurementPARTICLE & PARTICLE SYSTEMS CHARACTERIZATION, Issue 3 2003David Jeon Abstract Defocusing digital particle image velocimetry (DDPIV) was used to investigate a bubbly flow in the wake of a hydrofoil. DDPIV is a three component volumetric velocimetry technique that operates at full video rate. Complex, three-dimensional, and time-dependent flows can be measured. To measure the bubble sizes, an extension to DDPIV was made to infer bubble sizes from their intensities. Both bubble size distributions and bubble velocity fields were simultaneously measured. Results indicate that DDPIV can reliably measure bubble sizes in the range of 100,microns, as well as resolving their aggregate motion. [source] Combined PIV/PTV-Measurements for the Analysis of Bubble Interactions and Coalescence in a Turbulent FlowTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 3-4 2003Dirk Bröder Abstract In order to allow more reliable modeling of coalescence processes in turbulent bubbly flows, detailed experiments in a double loop reactor were performed. Narrow and essentially monomodal bubble size distributions in the range of 2 to 4 mm were created. For simultaneous measurements of bubble size, bubble velocity and liquid velocity a combined system of PIV and PTV was developed and applied. It was possible to determine bubble size distributions and mean, as well as fluctuating velocities for both phases. The spatial changes of the bubble size distribution, due to the influence of bubble coalescence, was analyzed and coalescence rates were calculated. Afin d'améliorer la fiabilité de la modélisation des procédés de coalescence dans les écoulements bouillonnants turbulents, des expériences poussées ont été menées dans un réacteur à double boucle. Des distributions de taille des bulles étroites, essentiellement monodisperses, dans la gamme de 2 à 4 mm, ont été créées. Pour les mesures simultanées de la taille des bulles, de la vitesse des bulles et de la vitesse du liquide, on a mis au point et appliqué un système combiné de PIV et PTV. Il a été possible de déterminer les distributions de taille des bulles et la moyenne mais également les vitesses fluctuantes pour les deux phases. Les changements spatiaux de la distribution de la taille des bulles dus à l'influence de la coalescence des bulles ont été analysés et les vitesses de coalescence ont été calculées. [source] | ||||||||||