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Sample records for bubble column reactors

  1. Fluid dynamic modelling of bubble column reactors

    OpenAIRE

    Khan, Khurram Imran

    2014-01-01

    Numerical simulations of rectangular shape bubble column reactors (BCR) are validated starting from preliminary simulations aimed at identifying proper simulation parameters for a given system and resulting up to the numerical simulation with mass transfer and chemical reactions. The transient, three dimensional simulations are carried out using FLUENT software and the results obtained for a system with low gas flow rate (48 L/h) indicated that we need enough fine mesh grid and appropriate cl...

  2. Hydrodynamic models for slurry bubble column reactors

    Energy Technology Data Exchange (ETDEWEB)

    Gidaspow, D. [IIT Center, Chicago, IL (United States)

    1995-12-31

    The objective of this investigation is to convert a {open_quotes}learning gas-solid-liquid{close_quotes} fluidization model into a predictive design model. This model is capable of predicting local gas, liquid and solids hold-ups and the basic flow regimes: the uniform bubbling, the industrially practical churn-turbulent (bubble coalescence) and the slugging regimes. Current reactor models incorrectly assume that the gas and the particle hold-ups (volume fractions) are uniform in the reactor. They must be given in terms of empirical correlations determined under conditions that radically differ from reactor operation. In the proposed hydrodynamic approach these hold-ups are computed from separate phase momentum balances. Furthermore, the kinetic theory approach computes the high slurry viscosities from collisions of the catalyst particles. Thus particle rheology is not an input into the model.

  3. ENGINEERING DEVELOPMENT OF SLURRY BUBBLE COLUMN REACTOR (SBCR) TECHNOLOGY

    Energy Technology Data Exchange (ETDEWEB)

    Bernard A. Toseland, Ph.D.

    1999-01-01

    The major technical objectives of this program are threefold: (1) to develop the design tools and a fundamental understanding of the fluid dynamics of a slurry bubble column reactor to maximize reactor productivity, (2) to develop the mathematical reactor design models and gain an understanding of the hydrodynamic fundamentals under industrially relevant process conditions, and (3) to develop an understanding of the hydrodynamics and their interaction with the chemistries occurring in the bubble column reactor. Successful completion of these objectives will permit more efficient usage of the reactor column and tighter design criteria, increase overall reactor efficiency, and ensure a design that leads to stable reactor behavior when scaling up to large diameter reactors.

  4. ENGINEERING DEVELOPMENT OF SLURRY BUBBLE COLUMN REACTOR (SBCR) TECHNOLOGY

    International Nuclear Information System (INIS)

    The major technical objectives of this program are threefold: (1) to develop the design tools and a fundamental understanding of the fluid dynamics of a slurry bubble column reactor to maximize reactor productivity, (2) to develop the mathematical reactor design models and gain an understanding of the hydrodynamic fundamentals under industrially relevant process conditions, and (3) to develop an understanding of the hydrodynamics and their interaction with the chemistries occurring in the bubble column reactor. Successful completion of these objectives will permit more efficient usage of the reactor column and tighter design criteria, increase overall reactor efficiency, and ensure a design that leads to stable reactor behavior when scaling up to large diameter reactors

  5. ENGINEERING DEVELOPMENT OF SLURRY BUBBLE COLUMN REACTOR (SBCR) TECHNOLOGY

    Energy Technology Data Exchange (ETDEWEB)

    Bernard A. Toseland, Ph.D.

    2002-01-01

    The major technical objectives of this program are threefold: (1) to develop the design tools and a fundamental understanding of the fluid dynamics of a slurry bubble column reactor to maximize reactor productivity, (2) to develop the mathematical reactor design models and gain an understanding of the hydrodynamic fundamentals under industrially relevant process conditions, and (3) to develop an understanding of the hydrodynamics and their interaction with the chemistries occurring in the bubble column reactor. Successful completion of these objectives will permit more efficient usage of the reactor column and tighter design criteria, increase overall reactor efficiency, and ensure a design that leads to stable reactor behavior when scaling up to large diameter reactors.

  6. ENGINEERING DEVELOPMENT OF SLURRY BUBBLE COLUMN REACTOR (SBCR) TECHNOLOGY

    Energy Technology Data Exchange (ETDEWEB)

    Bernard A. Toseland

    2002-09-30

    The major technical objectives of this program are threefold: (1) to develop the design tools and a fundamental understanding of the fluid dynamics of a slurry bubble column reactor to maximize reactor productivity, (2) to develop the mathematical reactor design models and gain an understanding of the hydrodynamic fundamentals under industrially relevant process conditions, and (3) to develop an understanding of the hydrodynamics and their interaction with the chemistries occurring in the bubble column reactor. Successful completion of these objectives will permit more efficient usage of the reactor column and tighter design criteria, increase overall reactor efficiency, and ensure a design that leads to stable reactor behavior when scaling up to large diameter reactors.

  7. ENGINEERING DEVELOPMENT OF SLURRY BUBBLE COLUMN REACTOR (SBCR) TECHNOLOGY

    Energy Technology Data Exchange (ETDEWEB)

    Bernard A. Toseland

    2000-06-30

    The major technical objectives of this program are threefold: (1) to develop the design tools and a fundamental understanding of the fluid dynamics of a slurry bubble column reactor to maximize reactor productivity, (2) to develop the mathematical reactor design models and gain an understanding of the hydrodynamic fundamentals under industrially relevant process conditions, and (3) to develop an understanding of the hydrodynamics and their interaction with the chemistries occurring in the bubble column reactor. Successful completion of these objectives will permit more efficient usage of the reactor column and tighter design criteria, increase overall reactor efficiency, and ensure a design that leads to stable reactor behavior when scaling up to large diameter reactors.

  8. Engineering Development of Slurry Bubble Column Reactor (SBCR) Technology

    Energy Technology Data Exchange (ETDEWEB)

    Toseland, B.A.

    1998-10-29

    The major technical objectives of this program are threefold: (1) to develop the design tools and a fundamental understanding of the fluid dynamics of a slurry bubble column reactor to maximize reactor productivity, (2) to develop the mathematical reactor design models and gain an understanding of the hydrodynamic fundamentals under industrially relevant process conditions, and (3) to develop an understanding of the hydrodynamics and their interaction with the chemistries occurring in the bubble column reactor. Successful completion of these objectives will permit more efficient usage of the reactor column and tighter design criteria, increase overall reactor efficiency, and ensure a design that leads to stable reactor behavior when scaling up to large diameter reactors.

  9. Axial and Radial Gas Holdup in Bubble Column Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Wagh, Sameer M.; Ansari, Mohashin E Alan; Kene, Pragati T. [RTMNU Nagpur, Nagpur (India)

    2014-06-15

    Bubble column reactors are considered the reactor of choice for numerous applications including oxidation, hydrogenation, waste water treatment, and Fischer-Tropsch (FT) synthesis. They are widely used in a variety of industrial applications for carrying out gas-liquid and gas-liquid-solid reactions. In this paper, the computational fluid dynamics (CFD) model is used for predicting the gas holdup and its distribution along radial and axial direction are presented. Gas holdup increases linearly with increase in gas velocity. Gas bubbles tends to concentrate more towards the center of the column and follows a wavy path.

  10. An Axial Dispersion Model for Evaporating Bubble Column Reactor

    Institute of Scientific and Technical Information of China (English)

    谢刚; 李希

    2004-01-01

    Evaporating bubble column reactor (EBCR) is a kind of aerated reactor in which the reaction heat is removed by the evaporation of volatile reaction mixture. In this paper, a mathematical model that accounts for the gas-liquid exothermic reaction and axial dispersions of both gas and liquid phase is employed to study the performance of EBCR for the process of p-xylene(PX) oxidation. The computational results show that there are remarkable concentration and temperature gradients in EBCR for high ratio of height to diameter (H/DT). The temperature is lower at the bottom of column and higher at the top, due to rapid evaporation induced by the feed gas near the bottom. The concentration profiles in the gas phase are more nonuniform than those (except PX) in the liquid phase, which causes more solvent burning consumption at high H/DT ratio. For p-xylene oxidation, theo ptimal H/DT is around 5.

  11. Conservation of bubble size distribution during gas reactive absorption in bubble column reactors

    Directory of Open Access Journals (Sweden)

    P. L.C. LAGE

    1999-12-01

    Full Text Available Conservation of the bubble size distribution function was applied to the reactive absorption of carbon dioxide in a bubble column reactor. The model developed was solved by the method of characteristics and by a Monte Carlo method. Simulations were carried out using simplified models for the liquid phase and for the gas-liquid mass transfer. Predictions of gas holdup and outlet gas composition showed that the concept of a mean bubble diameter is not applicable when the bubble size distribution is reasonably polydispersed. In these cases, the mass mean velocity and the numerical mean velocity of the bubbles are very different. Therefore, quantification of the polydispersion of bubbles was shown to be essential to gas-phase hydrodynamics modeling.

  12. COMPUTATIONAL AND EXPERIMENTAL MODELING OF SLURRY BUBBLE COLUMN REACTORS

    Energy Technology Data Exchange (ETDEWEB)

    Paul C.K. Lam; Isaac K. Gamwo; Dimitri Gidaspow

    2002-05-01

    The objective of this study was to develop a predictive experimentally verified computational fluid dynamics (CFD) model for gas-liquid-solid flow. A three dimensional transient computer code for the coupled Navier-Stokes equations for each phase was developed and is appended in this report. The principal input into the model is the viscosity of the particulate phase which was determined from a measurement of the random kinetic energy of the 800 micron glass beads and a Brookfield viscometer. The details are presented in the attached paper titled ''CFD Simulation of Flow and Turbulence in a Slurry Bubble Column''. This phase of the work is in press in a referred journal (AIChE Journal, 2002) and was presented at the Fourth International Conference on Multiphase Flow (ICMF 2001) in New Orleans, May 27-June 1, 2001 (Paper No. 909). The computed time averaged particle velocities and concentrations agree with Particle Image Velocimetry (PIV) measurements of velocities and concentrations, obtained using a combination of gamma-ray and X-ray densitometers, in a slurry bubble column, operated in the bubbly-coalesced fluidization regime with continuous flow of water. Both the experiment and the simulation show a down-flow of particles in the center of the column and up-flow near the walls and nearly uniform particle concentration. Normal and shear Reynolds stresses were constructed from the computed instantaneous particle velocities. The PIV measurement and the simulation produced instantaneous particle velocities. The PIV measurement and the simulation produced similar nearly flat horizontal profiles of turbulent kinetic energy of particles. To better understand turbulence we studied fluidization in a liquid-solid bed. This work was also presented at the Fourth International Conference on Multiphase Flow (ICMF 2001, Paper No. 910). To understand turbulence in risers, measurements were done in the IIT riser with 530 micron glass beads using a PIV

  13. Engineering development of slurry bubble column reactor (SBCR) technology. Quarterly report, January 1--March 31, 1996

    Energy Technology Data Exchange (ETDEWEB)

    Toseland, B.A.; Tischer, R.E.

    1997-12-31

    The major technical objectives of this program are threefold: (1) to develop the design tools and a fundamental understanding of the fluid dynamics of a slurry bubble column reactor to maximize reactor productivity; (2) to develop the mathematical reactor design models and gain an understanding of the hydrodynamic fundamentals under industrially relevant process conditions; and (3) to develop an understanding of the hydrodynamics and their interaction with the chemistries occurring in the bubble column reactor. Successful completion of these objectives will permit more efficient usage of the reactor column and tighter design criteria, increase overall reactor efficiency, and ensure a design that leads to stable reactor behavior when scaling up to large diameter reactors. The main part of this report describes tracer studies of slurry bubble column hydrodynamics during methanol synthesis.

  14. COMPUTATIONAL AND EXPERIMENTAL MODELING OF SLURRY BUBBLE COLUMN REACTORS

    Energy Technology Data Exchange (ETDEWEB)

    Paul Lam; Dimitri Gidaspow

    2000-09-01

    The objective if this study was to develop a predictive experimentally verified computational fluid dynamics (CFD) model for gas-liquid-solid flow. A three dimensional transient computer code for the coupled Navier-Stokes equations for each phase was developed. The principal input into the model is the viscosity of the particulate phase which was determined from a measurement of the random kinetic energy of the 800 micron glass beads and a Brookfield viscometer. The computed time averaged particle velocities and concentrations agree with PIV measurements of velocities and concentrations, obtained using a combination of gamma-ray and X-ray densitometers, in a slurry bubble column, operated in the bubbly-coalesced fluidization regime with continuous flow of water. Both the experiment and the simulation show a down-flow of particles in the center of the column and up-flow near the walls and nearly uniform particle concentration. Normal and shear Reynolds stresses were constructed from the computed instantaneous particle velocities. The PIV measurement and the simulation produced instantaneous particle velocities. The PIV measurement and the simulation produced similar nearly flat horizontal profiles of turbulent kinetic energy of particles. This phase of the work was presented at the Chemical Reaction Engineering VIII: Computational Fluid Dynamics, August 6-11, 2000 in Quebec City, Canada. To understand turbulence in risers, measurements were done in the IIT riser with 530 micron glass beads using a PIV technique. The results together with simulations will be presented at the annual meeting of AIChE in November 2000.

  15. Gas-Liquid Mass Transfer in a Slurry Bubble Column Reactor under High Temperature and

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The gas-liquid mass transfer of H2 and CO in a high temperature and high-pressure three-phase slurry bubble column reactor is studied. The gas-liquid volumetric mass transfer coefficients κLα are obtained by measuring the dissolution rate of H2 and CO. The influences of the main operation conditions, such as temperature, pressure, superficial gas velocity and solid concentration, are studied systematically. Two empirical correlations are proposed to predict κLα values for H2 and CO in liquid paraffin/solid particles slurry bubble column reactors.

  16. Modeling of Bubble Column Slurry Reactor for Dimethyl Ether Synthesis from Syngas

    Institute of Scientific and Technical Information of China (English)

    张海涛; 应卫勇; 房鼎业

    2005-01-01

    A mathematical model for a bubble column slurry reactor is presented for dimethyl ether synthesis from syngas. Methanol synthesis from carbon monoxide and carbon dioxide by hydrogenation and the methanol dehydration are considered as independent reactions, in which methanol, dimethyl ether and carbon dioxide are the key components. In this model, the gas phase is considered to be in plug flow and the liquid phase to be in partly back mixing with axial distribution of solid catalyst. The simulation results show that the axial dispersion of solid catalysts, the operational height of the slurry phase in the bubble column slurry reactor, and the reaction results are influenced by the reaction temperature and pressure, which are the basic data for the scale-up of reactor.

  17. ADVANCED DIAGNOSTIC TECHNIQUES FOR THREE-PHASE SLURRY BUBBLE COLUMN REACTORS (SBCR)

    Energy Technology Data Exchange (ETDEWEB)

    M.H. Al-Dahhan; M.P. Dudukovic; L.S. Fan

    2001-07-25

    This report summarizes the accomplishment made during the second year of this cooperative research effort between Washington University, Ohio State University and Air Products and Chemicals. The technical difficulties that were encountered in implementing Computer Automated Radioactive Particle Tracking (CARPT) in high pressure SBCR have been successfully resolved. New strategies for data acquisition and calibration procedure have been implemented. These have been performed as a part of other projects supported by Industrial Consortium and DOE via contract DE-2295PC95051 which are executed in parallel with this grant. CARPT and Computed Tomography (CT) experiments have been performed using air-water-glass beads in 6 inch high pressure stainless steel slurry bubble column reactor at selected conditions. Data processing of this work is in progress. The overall gas holdup and the hydrodynamic parameters are measured by Laser Doppler Anemometry (LDA) in 2 inch slurry bubble column using Norpar 15 that mimic at room temperature the Fischer Tropsch wax at FT reaction conditions of high pressure and temperature. To improve the design and scale-up of bubble column, new correlations have been developed to predict the radial gas holdup and the time averaged axial liquid recirculation velocity profiles in bubble columns.

  18. Simple correlations for bubble columns and draft tube airlift reactors with dilute alcohol solutions

    OpenAIRE

    Kojić Predrag S.; Tokić Milenko S.; Čolović Radmilo R.; Šijački Ivana M.

    2009-01-01

    Simple empirical correlations were developed to predict gas holdup, liquid circulation time, downcomer liquid velocity and volumetric mass transfer coefficient in dilute alcohol solutions in bubble columns and draft tube airlift reactors with single orifice sparger. Also, new experiments were conducted with diluted alcohol solutions to n-octanol, expanding the experimental data from C1 up to C8. The proposed empirical correlations include, beside the superficial gas velocity, the alcohol chai...

  19. Numerical Modeling of Air-Water Flows in Bubble Columns and Airlift Reactors

    OpenAIRE

    Studley, Allison F

    2010-01-01

    Bubble columns and airlift reactors were modeled numerically to better understand the hydrodynamics and analyze the mixing characteristics for each configuration. An Eulerian-Eulerian approach was used to model air as the dispersed phase within a continuous phase of water using the commercial software FLUENT. The Schiller-Naumann drag model was employed along with virtual mass and the standard k-e turbulence model. The equations were discretized using the QUICK scheme and solved with the SIMP...

  20. Radiotracer study in a bubble column reactor (visbreaker)

    International Nuclear Information System (INIS)

    Radiotracer technique was used to measure residence time distribution (RTD) of fuel oil in a pilot-plant visbreaker with an objective to investigate hydrodynamic behaviour at different operating conditions. Bromine-82 as dibromobiphenyle was used as a tracer to measure RTD of the fuel oil. Mean residence times were determined from the measured RTD data. Tanks-in-series with backmixing model was used to simulate the measured RTD data. The results of simulation indicated that the visbreaker did not behave as a plug flow reactor as desired for visbreaking process. The presence of internals i.e. baffles inside the visbreaker decreases the mean residence time and backmixing. Thus, the designed internals have shown promising effect in terms of reduced backmixing in the visbreaker. (author)

  1. Bubble column reactor fluid dynamic study at pilot plant scale for residue and extra heavy crude oil upgrading technology

    Energy Technology Data Exchange (ETDEWEB)

    Sardella, R.; Medina, H. [Infrastructure and Upgrading Department PDVSA-Intevep (Venezuela); Zacarias, L.; Paiva, M. [Refining Department. PDVSA-Intevep (Venezuela)

    2011-07-01

    Bubble column reactors are used in several applications because of their simplicity and low cost; a new technology was developed to convert extra heavy crude oil into upgraded crude using a bubble column reactor. To design this kind of reactor, a lot of parameters like flow regime, gas hold up and dispersion coefficient have to be taken into account. This study aimed at determining the fluid dynamic behaviour of a bubble column working under Aquaconversion operating conditions. Experiments were undertaken on air-tap water and air-light oil systems under atmospheric conditions with various gas superficial velocities and liquid flowrates. Results showed that gas hold up increases with superficial gas velocity but is independent of liquid flowrate and that both systems tested work at the same flow regimes. This paper showed that under the experimental conditions used, this reactor tends to be a complete mixing reactor.

  2. Simple correlations for bubble columns and draft tube airlift reactors with dilute alcohol solutions

    Directory of Open Access Journals (Sweden)

    Kojić Predrag S.

    2009-01-01

    Full Text Available Simple empirical correlations were developed to predict gas holdup, liquid circulation time, downcomer liquid velocity and volumetric mass transfer coefficient in dilute alcohol solutions in bubble columns and draft tube airlift reactors with single orifice sparger. Also, new experiments were conducted with diluted alcohol solutions to n-octanol, expanding the experimental data from C1 up to C8. The proposed empirical correlations include, beside the superficial gas velocity, the alcohol chain length as the only factor to characterize the liquid phase. The suggested correlations have shown good agreement between the calculated and the experimental data.

  3. Flow patterns in a slurry-bubble-column reactor under reaction conditions

    Energy Technology Data Exchange (ETDEWEB)

    Toselane, B.A.; Brown, D.M.; Zou, B.S.; Dudukovic, M.P. [Washington Univ., St. Louis, MO (United States)

    1995-12-31

    The gas and liquid radioactive tracer response curves obtained in an industrial bubble column reactor of height to diameter ratio of 10 are analyzed and the suitability of the axial dispersion model for interpretation of the results is discussed. The relationship between the tracer concentration distribution and measured detector response of the soluble gas tracer (Ar-41) is possibly dominated by the dissolved gas. The one dimensional axial dispersion model cannot match all the experimental observations well and the flow pattern of the undissolved gas cannot be determined with certainty.

  4. CO{sub 2} capture by aqueous solutions of glucosamine in a bubble column reactor

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Abuin, A.; Gomez-Diaz, D.; Navaza, J.M.; Vidal-Tato, I. [University of Santiago de Compostela, Santiago De Compostela (Spain)

    2010-08-01

    The present work analyses the carbon dioxide (CO{sub 2}) capture process by means of absorption with chemical reaction with glucosamine aqueous solutions, using a bubble column reactor (BCR). Experimental results indicate that this reagent has a similar behaviour to other common amines (i.e. monoethanolamine, widely used in CO{sub 2} capture), as regarding the capture rate of this acidic gas. The value of the mass transfer coefficient corresponding to the liquid phase has been determined, and the effect of different operation conditions upon the value of that coefficient has also been analysed (amine concentration, pH and gas flow-rate).

  5. ADVANCED DIAGNOSTIC TECHNIQUES FOR THREE-PHASE SLURRY BUBBLE COLUMN REACTORS(SBCR)

    Energy Technology Data Exchange (ETDEWEB)

    M.H. Al-Dahhan; L.S. Fan; M.P. Dudukovic

    2002-07-25

    This report summarizes the accomplishment made during the third year of this cooperative research effort between Washington University, Ohio State University and Air Products and Chemicals. Data processing of the performed Computer Automated Radioactive Particle Tracking (CARPT) experiments in 6 inch column using air-water-glass beads (150 {micro}m) system has been completed. Experimental investigation of time averaged three phases distribution in air-Therminol LT-glass beads (150 {micro}m) system in 6 inch column has been executed. Data processing and analysis of all the performed Computed Tomography (CT) experiments have been completed, using the newly proposed CT/Overall gas holdup methodology. The hydrodynamics of air-Norpar 15-glass beads (150 {micro}m) have been investigated in 2 inch slurry bubble column using Dynamic Gas Disengagement (DGD), Pressure Drop fluctuations, and Fiber Optic Probe. To improve the design and scale-up of bubble column reactors, a correlation for overall gas holdup has been proposed based on Artificial Neural Network and Dimensional Analysis.

  6. Two-Bubble Class Model for Churn-Turbulent Regime in a Bubble Column Slurry Reactor of Fischer-Tropsch Synthesis

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A model for a bubble column slurry reactor is developed based on the experiment of Rhenpreussen Koppers demonstration plant for slurry phase Fischer-Tropsch synthesis reported by Koelble et al. This model is applicable to the operation in the churn-turbulent regime and incorporates the information on the bubble size. The axial dispersion model is adopted to describe the flow characteristics of the Fischer-Tropsch slurry reactor. With the model developed, simulations are performed to identify the steady state behavior of a Fischer-Tropsch slurry reactor of commercial size. Predictions of the two-bubble class model is compared with that of the conventional single- bubble class model. The results show that under a variety of conditions, the two-bubble class model gives results different from those for the single-bubble class model.

  7. Gas-Liquid Mass Transfer in a Slurry Bubble Column Reactor under High Temperature andHigh Pressure

    Institute of Scientific and Technical Information of China (English)

    杨卫国; 王金福; 金涌

    2001-01-01

    The gas-liquid mass transfer of H2 and CO in a high temperature and high-pressure three-phase slurry bubble column reactor is studied. The gas-liquid volumetric mass transfer coefficients kLa are obtained by measuring the dissolution rate of H2 and CO. The influences of the main operation conditions, such as temperature, pressure,superficial gas velocity and solid concentration, are studied systematically. Two empirical correlations are proposed to predict kLa values for H2 and CO in liquid paraffln/solid particles slurry bubble column reactors.

  8. PROGRESS TOWARDS MODELING OF FISCHER TROPSCH SYNTHESIS IN A SLURRY BUBBLE COLUMN REACTOR

    Energy Technology Data Exchange (ETDEWEB)

    Donna Post Guillen; Tami Grimmett; Anastasia M. Gandrik; Steven P. Antal

    2010-11-01

    The Hybrid Energy Systems Testing (HYTEST) Laboratory is being established at the Idaho National Laboratory to develop and test hybrid energy systems with the principal objective to safeguard U.S. Energy Security by reducing dependence on foreign petroleum. A central component of the HYTEST is the slurry bubble column reactor (SBCR) in which the gas-to-liquid reactions will be performed to synthesize transportation fuels using the Fischer Tropsch (FT) process. SBCRs are cylindrical vessels in which gaseous reactants (for example, synthesis gas or syngas) is sparged into a slurry of liquid reaction products and finely dispersed catalyst particles. The catalyst particles are suspended in the slurry by the rising gas bubbles and serve to promote the chemical reaction that converts syngas to a spectrum of longer chain hydrocarbon products, which can be upgraded to gasoline, diesel or jet fuel. These SBCRs operate in the churn-turbulent flow regime which is characterized by complex hydrodynamics, coupled with reacting flow chemistry and heat transfer, that effect reactor performance. The purpose of this work is to develop a computational multiphase fluid dynamic (CMFD) model to aid in understanding the physico-chemical processes occurring in the SBCR. Our team is developing a robust methodology to couple reaction kinetics and mass transfer into a four-field model (consisting of the bulk liquid, small bubbles, large bubbles and solid catalyst particles) that includes twelve species: (1) CO reactant, (2) H2 reactant, (3) hydrocarbon product, and (4) H2O product in small bubbles, large bubbles, and the bulk fluid. Properties of the hydrocarbon product were specified by vapor liquid equilibrium calculations. The absorption and kinetic models, specifically changes in species concentrations, have been incorporated into the mass continuity equation. The reaction rate is determined based on the macrokinetic model for a cobalt catalyst developed by Yates and Satterfield [1]. The

  9. Effect of hydrodynamics on kinetics of gluconic acid enzymatic production in bubble column reactor

    Directory of Open Access Journals (Sweden)

    Ramezani Mohammad

    2013-01-01

    Full Text Available Oxidation of glucose by homogeneous glucose oxidase was performed in rectangular bubble column reactor at 40°C, ambient pressure and pH of 5.5 while superficial gas (oxygen velocity was varied in the homogeneous and transition regime in the range of 0.0014 - 0.0112 m s-1. Effect of superficial gas (oxygen velocity on the apparent reaction rate and its parameters was determined and it was observed that the apparent reaction rate on the basis of volume of the liquid increased with increasing the superficial gas (oxygen velocity. The apparent reaction rate was assumed to be in the form of Michaelis-Menten equation and its apparent kinetic parameters were evaluated by the nonlinear regression method.

  10. Non-catalytic alcoholysis process for production of biodiesel fuel by using bubble column reactor

    Science.gov (United States)

    Hagiwara, S.; Nabetani, H.; Nakajima, M.

    2015-04-01

    -edible lipids by use of the SMV reactor has not been examined yet. Therefore, this study aims to investigate the productivity of biodiesel produced from waste vegetable oils using the SMV reactor. Biodiesel fuel is a replacement for diesel as a fuel produced from biomass resources. It is generally produced as a FAME derived from vegetable oil by using alkaline catalyzed alcoholysis process. This alkaline method requires deacidification process prior to the reaction process and the alkaline catalyst removal process after the reaction. Those process increases the total cost of biodiesel fuel production. In order to solve the problems in the conventional alkaline catalyzed alcoholysis process, the authors proposed a non-catalytic alcoholysis process called the Superheated Methanol Vapor (SMV) method with bubble column reactor. So, this study aims to investigate the productivity of biodiesel produced from vegetable oils and other lipids using the SMV method with bubble column reactor.

  11. Molten salt rolling bubble column, reactors utilizing same and related methods

    Science.gov (United States)

    Turner, Terry D.; Benefiel, Bradley C.; Bingham, Dennis N.; Klinger, Kerry M.; Wilding, Bruce M.

    2015-11-17

    Reactors for carrying out a chemical reaction, as well as related components, systems and methods are provided. In accordance with one embodiment, a reactor is provided that includes a furnace and a crucible positioned for heating by the furnace. The crucible may contain a molten salt bath. A downtube is disposed at least partially within the interior crucible along an axis. The downtube includes a conduit having a first end in communication with a carbon source and an outlet at a second end of the conduit for introducing the carbon material into the crucible. At least one opening is formed in the conduit between the first end and the second end to enable circulation of reaction components contained within the crucible through the conduit. An oxidizing material may be introduced through a bottom portion of the crucible in the form of gas bubbles to react with the other materials.

  12. DEVELOPMENT OF A COMPUTATIONAL MULTIPHASE FLOW MODEL FOR FISCHER TROPSCH SYNTHESIS IN A SLURRY BUBBLE COLUMN REACTOR

    Energy Technology Data Exchange (ETDEWEB)

    Donna Post Guillen; Tami Grimmett; Anastasia M. Gribik; Steven P. Antal

    2010-09-01

    The Hybrid Energy Systems Testing (HYTEST) Laboratory is being established at the Idaho National Laboratory to develop and test hybrid energy systems with the principal objective to safeguard U.S. Energy Security by reducing dependence on foreign petroleum. A central component of the HYTEST is the slurry bubble column reactor (SBCR) in which the gas-to-liquid reactions will be performed to synthesize transportation fuels using the Fischer Tropsch (FT) process. SBCRs are cylindrical vessels in which gaseous reactants (for example, synthesis gas or syngas) is sparged into a slurry of liquid reaction products and finely dispersed catalyst particles. The catalyst particles are suspended in the slurry by the rising gas bubbles and serve to promote the chemical reaction that converts syngas to a spectrum of longer chain hydrocarbon products, which can be upgraded to gasoline, diesel or jet fuel. These SBCRs operate in the churn-turbulent flow regime which is characterized by complex hydrodynamics, coupled with reacting flow chemistry and heat transfer, that effect reactor performance. The purpose of this work is to develop a computational multiphase fluid dynamic (CMFD) model to aid in understanding the physico-chemical processes occurring in the SBCR. Our team is developing a robust methodology to couple reaction kinetics and mass transfer into a four-field model (consisting of the bulk liquid, small bubbles, large bubbles and solid catalyst particles) that includes twelve species: (1) CO reactant, (2) H2 reactant, (3) hydrocarbon product, and (4) H2O product in small bubbles, large bubbles, and the bulk fluid. Properties of the hydrocarbon product were specified by vapor liquid equilibrium calculations. The absorption and kinetic models, specifically changes in species concentrations, have been incorporated into the mass continuity equation. The reaction rate is determined based on the macrokinetic model for a cobalt catalyst developed by Yates and Satterfield [1]. The

  13. Incorporation of Reaction Kinetics into a Multiphase, Hydrodynamic Model of a Fischer Tropsch Slurry Bubble Column Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Donna Guillen, PhD; Anastasia Gribik; Daniel Ginosar, PhD; Steven P. Antal, PhD

    2008-11-01

    This paper describes the development of a computational multiphase fluid dynamics (CMFD) model of the Fischer Tropsch (FT) process in a Slurry Bubble Column Reactor (SBCR). The CMFD model is fundamentally based which allows it to be applied to different industrial processes and reactor geometries. The NPHASE CMFD solver [1] is used as the robust computational platform. Results from the CMFD model include gas distribution, species concentration profiles, and local temperatures within the SBCR. This type of model can provide valuable information for process design, operations and troubleshooting of FT plants. An ensemble-averaged, turbulent, multi-fluid solution algorithm for the multiphase, reacting flow with heat transfer was employed. Mechanistic models applicable to churn turbulent flow have been developed to provide a fundamentally based closure set for the equations. In this four-field model formulation, two of the fields are used to track the gas phase (i.e., small spherical and large slug/cap bubbles), and the other two fields are used for the liquid and catalyst particles. Reaction kinetics for a cobalt catalyst is based upon values reported in the published literature. An initial, reaction kinetics model has been developed and exercised to demonstrate viability of the overall solution scheme. The model will continue to be developed with improved physics added in stages.

  14. Conversion of low H/sub 2//CO ratio synthesis gas to hydrocarbons: Final report, October 1, 1981-September 30, 1986. [Bubble-column reactor

    Energy Technology Data Exchange (ETDEWEB)

    Bell, A.T.; Heinemann, H.

    1986-01-01

    The objectives of this project have been twofold: (1) to develop a theoretical model for designing bubble-column reactors and assessing their performance and (2) to characterize the performance of a laboratory-scale bubble-column reactor. The theoretical part of the project has focused the effects of gas-liquid mass transfer; axial dispersion of gas, liquid, and catalyst; ad the interplay between the kinetics of Fischer-Tropsch synthesis and the water-gas-shift reaction. The experimental portion of the project has focused the effects of reaction conditions on product distribution and, in particular, the conditions under which gas-liquid mass transfer becomes important. Any independent set of experiments was undertaken to investigate the chemistry of carbonaceous deposits formed during Fischer-Tropsch synthesis. 8 refs.

  15. CFD Simulation of Residence Time Distribution in Airlift Reactor and Bubble Column

    Czech Academy of Sciences Publication Activity Database

    Šimčík, Miroslav; Mota, A.; Havlica, Jaromír; Růžička, Marek; Vincente, A.; Teixeira, J.

    Bratislava: Slovak University of Technology, 2009 - (Markoš, J.), s. 352 ISBN 978-80-227-3072-3. [International Conference of Slovak Society of Chemical Engineering /36./. Tatranské Matliare (SK), 25.05.2009-29.05.2009] R&D Projects: GA ČR GA104/07/1110 Institutional research plan: CEZ:AV0Z40720504 Keywords : simulations * experiments * airlift reactor Subject RIV: CI - Industrial Chemistry, Chemical Engineering

  16. Regeneration of barium carbonate from barium sulphide in a pilot-scale bubbling column reactor and utilization for acid mine drainage.

    Science.gov (United States)

    Mulopo, J; Zvimba, J N; Swanepoel, H; Bologo, L T; Maree, J

    2012-01-01

    Batch regeneration of barium carbonate (BaCO(3)) from barium sulphide (BaS) slurries by passing CO(2) gas into a pilot-scale bubbling column reactor under ambient conditions was used to assess the technical feasibility of BaCO(3) recovery in the Alkali Barium Calcium (ABC) desalination process and its use for sulphate removal from high sulphate Acid Mine Drainage (AMD). The effect of key process parameters, such as BaS slurry concentration and CO(2) flow rate on the carbonation, as well as the extent of sulphate removal from AMD using the recovered BaCO(3) were investigated. It was observed that the carbonation reaction rate for BaCO(3) regeneration in a bubbling column reactor significantly increased with increase in carbon dioxide (CO(2)) flow rate whereas the BaS slurry content within the range 5-10% slurry content did not significantly affect the carbonation rate. The CO(2) flow rate also had an impact on the BaCO(3) morphology. The BaCO(3) recovered from the pilot-scale bubbling column reactor demonstrated effective sulphate removal ability during AMD treatment compared with commercial BaCO(3). PMID:22233912

  17. Performance of a modified multi-stage bubble column reactor for lead(II) and biological oxygen demand removal from wastewater using activated rice husk

    International Nuclear Information System (INIS)

    The excessive release of wastewater into the environment is a major concern worldwide. Adsorption is the one of the most effective technique for treatment of wastewater. In this work activated carbon prepared from rice husk has been used as an adsorbent. In the present investigation a three phase modified multi-stage bubble column reactor (MMBCR) has been designed to remove lead and biochemical oxygen demand (BOD) from wastewater by means of its adsorption onto the surface of activated rice husk. The multi-staging has been achieved by hydrodynamically induced continuous bubble generation, breakup and regeneration. Under optimum conditions, maximum lead and BOD reduction achieved using activated rice husk was 77.15% and 19.05%, respectively. Results showed MMBCR offered appreciated potential benefits for lead removal from wastewater and BOD removal, even this extent of removal is encouraging and the MMBCR can be used a pretreatment unit before subjecting the wastewater to biological treatment

  18. CFD simulation of bubble column

    Energy Technology Data Exchange (ETDEWEB)

    Ekambara, K., E-mail: ekambara@ualberta.c [Department of Chemical and Materials Engineering, University of Alberta, 536 CME Building, Edmonton, AB, T6G 2G6 (Canada); Dhotre, M.T. [Thermal-Hydraulics Laboratory, Nuclear Energy and Safety Department, Paul Scherrer Institute, CH-5232 Villigen PSI (Switzerland)

    2010-05-15

    Three-dimensional simulations of gas-liquid flow in the bubble column using the Euler-Euler approach is presented. The attempt is made to assess the performance and applicability of different turbulence models namely, k-epsilon, k-epsilon RNG, k-omega, Reynolds stress model (RSM) and large eddy simulation (LES) using a commercial code (ANSYS-CFX). For this purpose, the predictions are compared against the experimental data of . Performance of the turbulence models is assessed on basis of comparison of axial liquid velocity, fractional gas hold-up, turbulent kinetic energy and turbulent eddy dissipation rate. All the non-drag (turbulent dispersion, virtual mass and lift force) and drag force were incorporated in the model. The low-Reynolds number treatment of the k-omega yields a better qualitative prediction than the k-epsilon model. The RSM predictions are comparable with LES results and seemed to give better prediction near the sparger, where the flow is more anisotropic and gives a clue why RANS approaches fails to predict the flow in this region. However, the large eddy simulations showed good agreement with the experimental data, but requires higher computational time than RSM.

  19. REVIEW OF EXPERIMENTAL CAPABILITIES AND HYDRODYNAMIC DATA FOR VALIDATION OF CFD BASED PREDICTIONS FOR SLURRY BUBBLE COLUMN REACTORS

    Energy Technology Data Exchange (ETDEWEB)

    Donna Post Guillen; Daniel S. Wendt

    2007-11-01

    The purpose of this paper is to document the review of several open-literature sources of both experimental capabilities and published hydrodynamic data to aid in the validation of a Computational Fluid Dynamics (CFD) based model of a slurry bubble column (SBC). The review included searching the Web of Science, ISI Proceedings, and Inspec databases, internet searches as well as other open literature sources. The goal of this study was to identify available experimental facilities and relevant data. Integral (i.e., pertaining to the SBC system), as well as fundamental (i.e., separate effects are considered), data are included in the scope of this effort. The fundamental data is needed to validate the individual mechanistic models or closure laws used in a Computational Multiphase Fluid Dynamics (CMFD) simulation of a SBC. The fundamental data is generally focused on simple geometries (i.e., flow between parallel plates or cylindrical pipes) or custom-designed tests to focus on selected interfacial phenomena. Integral data covers the operation of a SBC as a system with coupled effects. This work highlights selected experimental capabilities and data for the purpose of SBC model validation, and is not meant to be an exhaustive summary.

  20. REVIEW OF EXPERIMENTAL CAPABILITIES AND HYDRODYNAMIC DATA FOR VALIDATION OF CFD-BASED PREDICTIONS FOR SLURRY BUBBLE COLUMN REACTORS

    Energy Technology Data Exchange (ETDEWEB)

    Donna Post Guillen; Daniel S. Wendt; Steven P. Antal; Michael Z. Podowski

    2007-11-01

    The purpose of this paper is to document the review of several open-literature sources of both experimental capabilities and published hydrodynamic data to aid in the validation of a Computational Fluid Dynamics (CFD) based model of a slurry bubble column (SBC). The review included searching the Web of Science, ISI Proceedings, and Inspec databases, internet searches as well as other open literature sources. The goal of this study was to identify available experimental facilities and relevant data. Integral (i.e., pertaining to the SBC system), as well as fundamental (i.e., separate effects are considered), data are included in the scope of this effort. The fundamental data is needed to validate the individual mechanistic models or closure laws used in a Computational Multiphase Fluid Dynamics (CMFD) simulation of a SBC. The fundamental data is generally focused on simple geometries (i.e., flow between parallel plates or cylindrical pipes) or custom-designed tests to focus on selected interfacial phenomena. Integral data covers the operation of a SBC as a system with coupled effects. This work highlights selected experimental capabilities and data for the purpose of SBC model validation, and is not meant to be an exhaustive summary.

  1. Investigation of Gas Holdup in a Vibrating Bubble Column

    Science.gov (United States)

    Mohagheghian, Shahrouz; Elbing, Brian

    2015-11-01

    Synthetic fuels are part of the solution to the world's energy crisis and climate change. Liquefaction of coal during the Fischer-Tropsch process in a bubble column reactor (BCR) is a key step in production of synthetic fuel. It is known from the 1960's that vibration improves mass transfer in bubble column. The current study experimentally investigates the effect that vibration frequency and amplitude has on gas holdup and bubble size distribution within a bubble column. Air (disperse phase) was injected into water (continuous phase) through a needle shape injector near the bottom of the column, which was open to atmospheric pressure. The air volumetric flow rate was measured with a variable area flow meter. Vibrations were generated with a custom-made shaker table, which oscillated the entire column with independently specified amplitude and frequency (0-30 Hz). Geometric dependencies can be investigated with four cast acrylic columns with aspect ratios ranging from 4.36 to 24, and injector needle internal diameters between 0.32 and 1.59 mm. The gas holdup within the column was measured with a flow visualization system, and a PIV system was used to measure phase velocities. Preliminary results for the non-vibrating and vibrating cases will be presented.

  2. Novel techniques for slurry bubble column hydrodynamics

    Energy Technology Data Exchange (ETDEWEB)

    Dudukovic, M.P.

    1999-05-14

    The objective of this cooperative research effort between Washington University, Ohio State University and Exxon Research Engineering Company was to improve the knowledge base for scale-up and operation of slurry bubble column reactors for syngas conversion and other coal conversion processes by increased reliance on experimentally verified hydrodynamic models. During the first year (July 1, 1995--June 30, 1996) of this three year program novel experimental tools (computer aided radioactive particle tracking (CARPT), particle image velocimetry (PIV), heat probe, optical fiber probe and gamma ray tomography) were developed and tuned for measurement of pertinent hydrodynamic quantities, such as velocity field, holdup distribution, heat transfer and bubble size. The accomplishments were delineated in the First Technical Annual Report. The second year (July, 1996--June 30, 1997) was spent on further development and tuning of the novel experimental tools (e.g., development of Monte Carlo calibration for CARPT, optical probe development), building up the hydrodynamic data base using these tools and comparison of the two techniques (PIV and CARPT) for determination of liquid velocities. A phenomenological model for gas and liquid backmixing was also developed. All accomplishments were summarized in the Second Annual Technical Report. During the third and final year of the program (July 1, 1997--June 30, 1998) and during the nine months no cost extension, the high pressure facility was completed and a set of data was taken at high pressure conditions. Both PIV, CT and CARPT were used. More fundamental hydrodynamic modeling was also undertaken and model predictions were compared to data. The accomplishments for this period are summarized in this report.

  3. On Stability of a Bubble Column

    Czech Academy of Sciences Publication Activity Database

    Růžička, Marek

    2013-01-01

    Roč. 91, č. 2 (2013), s. 191-203. ISSN 0263-8762 R&D Projects: GA ČR GA104/07/1110 Institutional support: RVO:67985858 Keywords : bubble column * flow regimes * steady solution Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 2.281, year: 2013

  4. Modeling of Bubble Column Slurry Reactor for Dimethyl Ether Synthesis from Syngas%合成气制二甲醚三相淤浆床反应器的数学模型研究

    Institute of Scientific and Technical Information of China (English)

    张海涛; 应卫勇; 房鼎业

    2005-01-01

    A mathematical model for a bubble column slurry reactor is presented for dimethyl ether synthesis from syngas. Methanol synthesis from carbon monoxide and carbon dioxide by hydrogenation and the methanol dehydration are considered as independent reactions, in which methanol, dimethyl ether and carbon dioxide are the key components. In this model, the gas phase is considered to be in plug flow and the liquid phase to be in partly back mixing with axial distribution of solid catalyst. The simulation results show that the axial dispersion of solid catalysts, the operational height of the slurry phase in the bubble column slurry reactor, and the reaction results are influenced by the reaction temperature and pressure, which are the basic data for the scale-up of reactor.

  5. Computational analysis of ozonation in bubble columns

    International Nuclear Information System (INIS)

    This paper presents a new computational ozonation model based on the principle of computational fluid dynamics along with the kinetics of ozone decay and microbial inactivation to predict the performance of ozone disinfection in fine bubble columns. The model can be represented using a mixture two-phase flow model to simulate the hydrodynamics of the water flow and using two transport equations to track the concentration profiles of ozone and microorganisms along the height of the column, respectively. The applicability of this model was then demonstrated by comparing the simulated ozone concentrations with experimental measurements obtained from a pilot scale fine bubble column. One distinct advantage of this approach is that it does not require the prerequisite assumptions such as plug flow condition, perfect mixing, tanks-in-series, uniform radial or longitudinal dispersion in predicting the performance of disinfection contactors without carrying out expensive and tedious tracer studies. (author)

  6. HYDRODYNAMIC MODELS FOR SLURRY BUBBLE COLUMN REACTORS. FINAL TECHNICAL REPORT ALSO INCLUDES THE QUARTERLY TECHNICAL REPORT FOR THE PERIOD 01/01/1997 - 03/31/1997.

    Energy Technology Data Exchange (ETDEWEB)

    DIMITRI GIDASPOW

    1997-08-15

    The objective of this study is to develop a predictive experimentally verified computational fluid dynamic (CFD) three phase model. It predicts the gas, liquid and solid hold-ups (volume fractions) and flow patterns in the industrially important bubble-coalesced (churn-turbulent) regime. The input into the model can be either particulate viscosities as measured with a Brookfield viscometer or effective restitution coefficient for particles. A combination of x-ray and {gamma}-ray densitometers was used to measure solid and liquid volume fractions. There is a fair agreement between the theory and the experiment. A CCD camera was used to measure instantaneous particle velocities. There is a good agreement between the computed time average velocities and the measurements. There is an excellent agreement between the viscosity of 800 {micro}m glass beads obtained from measurement of granular temperature (random kinetic energy of particles) and the measurement using a Brookfield viscometer. A relation between particle Reynolds stresses and granular temperature was found for developed flow. Such measurement and computations gave a restitution coefficient for a methanol catalyst to be about 0.9. A transient, two-dimensional hydrodynamic model for production of methanol from syn-gas in an Air Products/DOE LaPorte slurry bubble column reactor was developed. The model predicts downflow of catalyst at the walls and oscillatory particle and gas flow at the center, with a frequency of about 0.7 Hertz. The computed temperature variation in the rector with heat exchangers was only about 5 K, indicating good thermal management. The computed slurry height, the gas holdup and the rate of methanol production agree with LaPorte's reported data. Unlike the previous models in the literature, this model computes the gas and the particle holdups and the particle rheology. The only adjustable parameter in the model is the effective particle restitution coefficient.

  7. Multi-scale and multi-fractal analysis of pressure fluctuation in slurry bubble column bed reactor

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The Daubechies second order wavelet was applied to decompose pressure fluctuation signals with the gas flux varying from 0.18 to 0.90 m3/h and the solid mass fraction from 0 to 20% and scales 1-9 detail signals and the 9th scale approximation signals. The pressure signals were studied by multi-scale and R/S analysis method. Hurst analysis method was applied to analyze multi-fractal characteristics of different scale signals. The results show that the characteristics of mono-fractal under scale 1 and scale 2, and bi-fractal under scale 3-9 are effective in deducing the hydrodynamics in slurry bubbling flow system. The measured pressure signals are decomposed to micro-scale signals, meso-scale signals and macro-scale signals. Micro-scale and macro-scale signals are of mono-fractal characteristics, and meso-scale signals are of bi-fractal characteristics. By analyzing energy distribution of different scale signals, it is shown that pressure fluctuations mainly reflects meso-scale interaction between the particles and the bubble.

  8. Production of Diacylglycerol-enriched Oil by Glycerolysis of Soybean Oil using a Bubble Column Reactor in a Solvent-free System.

    Science.gov (United States)

    Zhang, Ning; Yang, Xue; Fu, Junning; Chen, Qiong; Song, Ziliang; Wang, Yong

    2016-03-01

    In this study, diacylglycerol-enriched soybean oil (DESO) was synthesized through Lipozyme 435-catalyzed glycerolysis of soybean oil (SO) in a solvent-free system using a modified bubble column reactor. The effects of enzyme load, mole ratio of glycerol to soybean oil, reaction temperature, gas flow and reaction time on DAG production were investigated. The selected conditions were established as being enzyme load of 4 wt% (mass of substrates), glycerol/soybean oil mole ratio of 20:1, reaction temperature of 80°C, gas flow of 10.6 cm/min, and a reaction time of 2.5 h, obtaining the DAG content of 49.4±0.5 wt%. The reusability of Lipozyme 435 was evaluated by monitoring the contents of DAG, monoacylglycerol (MAG) and triacylglycerol (TAG) in 10 consecutive runs. After purified by one-step molecular distillation, the DAG content of 63.5±0.3 wt% was achieved in DESO. The mole ratio of 1, 3-DAG to 1, 2-DAG was 2:1 and the fatty acid composition had no significant difference from that of soybean oil. However, the thermal properties of DESO and SO had considerable differences. Polymorphic form of DESO were mainly the β form and minor amounts of the β' form. Granular aggregation and round-shaped crystals were detected in DESO. PMID:26876674

  9. Optimization of C/N Ratio and Inducers for Wastewater Paper Industry Treatment Using Trametes versicolor Immobilized in Bubble Column Reactor

    Directory of Open Access Journals (Sweden)

    Aura M. Pedroza-Rodríguez

    2013-01-01

    Full Text Available C/N ratio and MnSO4 and CuSO4 concentrations were optimized for decolorization and chemical oxygen demand (COD removal of bleached Kraft pulp mill effluent by Trametes versicolor immobilized in polyurethane foam. Statistical differences (P<0.0001 at high C/N ratios (169, 2 mM CuSO4, and 0.071 mM MnSO4 were determined. Decolorization of 60.5%, COD removal of 55%, laccase (LAC 60 U/L, and manganese peroxidase (MnP 8.4 U/L were obtained. Maximum of decolorization (82%, COD removal (83%, LAC (443.5 U/L, and MnP (18 U/L activities at C/N ratio of 405 (6.75 mM CuSO4 and 0.22 mM MnSO4 was achieved in step 7 at 4 d. Positive correlation between the decolorization, COD removal, and enzymatic activity was found (P<0.0001. T. versicolor bioremediation capacity was evaluated in bubble column reactor during 8 d. Effluent was adjusted according to optimized parameters and treated at 25°C and air flow of 800 mL/min. Heterotrophic bacteria growth was not inhibited by fungus. After 4 d, 82% of COD reduction and 80% decolorization were recorded. Additionally, enzymatic activity of LAC (345 U/L and MnP (78 U/L was observed. The COD reduction and decolorization correlated positively (P<0.0001 with enzymatic activity. Chlorophenol removal was 98% of pentachlorophenol (PCP, 92% of 2,4,5-trichlorophenol (2,4,5-TCP, 90% of 3,4-dichlorophenol (3,4-DCP, and 99% of 4-chlorophenols (4CP.

  10. Ultrasonic technique for void fraction measurement in a bubbly column

    International Nuclear Information System (INIS)

    The measurement of the void fraction in a bubbly flow is important for modeling two-phase gas-liquid flow for the safety of nuclear reactors and thermal-hydraulics analysis. In this work, a non-invasive ultrasonic technique was developed for the measurement of the void fraction by correlating it with the amplitude of the ultrasonic pulse reflected from the opposite wall of the tube. The technique was applied in a test section made of 52.9 mm internal diameter glass column which makes possible the visualization of the bubble flow. A special ultrasonic methodology was developed for the processing of the ultrasonic signals generated by a transducer of 10 MHz frequency and 1/2 inch diameter. (author)

  11. Determination of size distribution of bubbles in a bubbly column two phase flows by ultrasound and neural networks

    Energy Technology Data Exchange (ETDEWEB)

    Baroni, Douglas B.; Lamy, Carlos A.; Bittencourt, Marcelo S.Q.; Pereira, Claudio M.N.A., E-mail: douglasbaroni@ien.gov.b, E-mail: lamy@ien.gov.b, E-mail: bittenc@ien.gov.b, E-mail: cmnap@ien.gov.b [Instituto de Engenharia Nuclear (IEN/CNEN-RJ), Rio de Janeiro, RJ (Brazil); Cunha Filho, Jurandyr S. [Escola Tecnica Estadual Visconde de Maua (ETEVM/RJ), Rio de Janeiro, RJ (Brazil); Motta, Mauricio S., E-mail: mmotta@cefet-rj.b [Centro Federal de Educacao Tecnologica Celso Suckow da Fonseca (CEFET/RJ), Rio de Janeiro, RJ (Brazil)

    2011-07-01

    The development of advanced nuclear reactor conceptions depends largely on the amount of available data to the designer. Non invasive ultrasonic techniques can contribute to the evaluation of gas-liquid two-phase regimes in the nuclear thermo-hydraulic circuits. A key-point for success of those techniques is the interpretation of the ultrasonic signal. In this work, a methodology based in artificial neural networks (ANN) is proposed to predict size distribution of bubbles in a bubbly flow. To accomplish that, an air feed system control was used to obtain specific bubbly flows in an experimental system utilizing a Plexiglas vertical bubbly column. Four different size distribution of bubbles were generated. The bubbles were photographed and measured. To evaluate the different size distribution of bubbles it was used the ultrasonic reflected echo on the opposite wall of the column. Then, an ANN has been developed for predicting size distribution of bubbles by using the frequency spectra of the ultrasonic signal as input. A trained artificial neural network using ultrasonic signal in the frequency domain can evaluate with a good precision the size distribution of bubbles generated in this system. (author)

  12. Closure relations for CFD simulation of bubble columns

    OpenAIRE

    Ziegenhein, Thomas; Lucas, Dirk; Rzehak, Roland; Krepper, Eckhard

    2014-01-01

    This paper describes the modelling of bubbly flow in a bubble column considering non-drag forces, polydispersity and bubble induced turbulence using the Eulerian two-fluid approach. The set of used closure models describing the momentum exchange between the phases was chosen on basis of broad experiences in modelling bubbly flows at the Helmholtz-Zentrum Dresden-Rossendorf. Polydispersity is modeled using the inhomogeneous multiple size group (iMUSIG) model, which was developed...

  13. Biodiesel fuels from palm oil via the non-catalytic transesterification in a bubble column reactor at atmospheric pressure: A kinetic study

    Energy Technology Data Exchange (ETDEWEB)

    Joelianingsih [National Food Research Institute, 2-1-12 Kannondai, Tsukuba, Ibaraki 305 8642 (Japan); Department of Chemical Engineering, Institut Teknologi Indonesia, Jl. Raya Puspiptek Serpong, Tangerang 15320 (Indonesia); Department of Global Agricultural Sciences, The University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo 113 8657 (Japan); Graduate School, Agricultural Engineering Science, Bogor Agricultural University, Darmaga Campus, P.O. Box 220, Bogor 16002 (Indonesia); Maeda, Hitoshi [National Food Research Institute, 2-1-12 Kannondai, Tsukuba, Ibaraki 305 8642 (Japan); Department of Global Agricultural Sciences, The University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo 113 8657 (Japan); Hagiwara, Shoji; Nabetani, Hiroshi [National Food Research Institute, 2-1-12 Kannondai, Tsukuba, Ibaraki 305 8642 (Japan); Sagara, Yasuyuki [Department of Global Agricultural Sciences, The University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo 113 8657 (Japan); Soerawidjaya, Tatang H. [Department of Chemical Engineering, Institut Teknologi Bandung, LABTEK X, Jl. Ganesha No. 10 Bandung 40132 (Indonesia); Tambunan, Armansyah H.; Abdullah, Kamaruddin [Graduate School, Agricultural Engineering Science, Bogor Agricultural University, Darmaga Campus, P.O. Box 220, Bogor 16002 (Indonesia)

    2008-07-15

    Biodiesel has become more attractive recently because of its environmental benefits and the fact that it is made from renewable resources. Transesterification of vegetable oils with short-chain alcohol has long been a preferred method for producing biodiesel fuel. A new reactor was developed to produce fatty acid methyl esters (FAME) by blowing bubbles of superheated methanol vapor continuously into vegetable oil without using any catalysts. A kinetic study on the non-catalytic transesterification of palm oil was made in a reactor without stirring at atmospheric pressure. The effects of reaction temperatures (523, 543, and 563 K) on the rate constant, conversion, yield of methyl esters (ME) and composition of the reaction product under semi-batch mode operation are investigated. The activation energy and the frequency factor values of the transesterification reaction obtained in this experiment are 31 kJ/mol and 4.2, respectively. The optimum reaction temperature which gives the highest ME content (95.17% w/w) in the reaction product is 523 K, while the rate constant of the total system increased with reaction temperature. (author)

  14. Studies on modelling of bubble driven flows in chemical reactors

    Energy Technology Data Exchange (ETDEWEB)

    Grevskott, Sverre

    1997-12-31

    Multiphase reactors are widely used in the process industry, especially in the petrochemical industry. They very often are characterized by very good thermal control and high heat transfer coefficients against heating and cooling surfaces. This thesis first reviews recent advances in bubble column modelling, focusing on the fundamental flow equations, drag forces, transversal forces and added mass forces. The mathematical equations for the bubble column reactor are developed, using an Eulerian description for the continuous and dispersed phase in tensor notation. Conservation equations for mass, momentum, energy and chemical species are given, and the k-{epsilon} and Rice-Geary models for turbulence are described. The different algebraic solvers used in the model are described, as are relaxation procedures. Simulation results are presented and compared with experimental values. Attention is focused on the modelling of void fractions and gas velocities in the column. The energy conservation equation has been included in the bubble column model in order to model temperature distributions in a heated reactor. The conservation equation of chemical species has been included to simulate absorption of CO{sub 2}. Simulated axial and radial mass fraction profiles for CO{sub 2} in the gas phase are compared with measured values. Simulations of the dynamic behaviour of the column are also presented. 189 refs., 124 figs., 1 tab.

  15. Acoustic and Visul Study of Bubble Formation Processes in Bubble Columns Staged with Fibrous Catalytic Layers

    Czech Academy of Sciences Publication Activity Database

    Höller, V.; Růžička, Marek; Drahoš, Jiří; Kiwi-Minsker, L.; Renken, A.

    79-80, - (2003), s. 151-157. ISSN 0920-5861 Institutional research plan: CEZ:AV0Z4072921 Keywords : bubble formation * fibrous catalytic layers * staged bubble column Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 2.627, year: 2003

  16. Scales and structures in bubbly flows. Experimental analysis of the flow in bubble columns and in bubbling fluidized beds

    NARCIS (Netherlands)

    Groen, J.S.

    2004-01-01

    In this project a detailed experimental analysis was performed of the dynamic flow field in bubbly flows, with the purpose of determining local hydrodynamics and scale effects. Measurements were done in gas-liquid systems (air-water bubble columns) and in gas-solid systems (air-sand bubbing fluidize

  17. Performance evaluation and effect of biogas circulation rate of a bubble column for biological desulfurization.

    Science.gov (United States)

    Kobayashi, Takuro; Xu, Kai-Qin; Li, Yu-You; Inamori, Yuhei

    2012-01-01

    Biological desulfurization using a bubble column reactor was investigated in a continuous biogas treatment. Rapid biogas circulation between the digester and the bubble column for biological desulfurization was used to stimulate the gas-liquid mass transfer of H(2)S. A positive correlation between the biogas circulation rate and H(2)S removal rate was observed. Moreover, the increase in the circulation rate stimulated the O(2) mass transfer, eventually translating into an increase in sulfate production from the oxidation of H(2)S. Throughout the continuous experiment, the reactor retained sufficient levels of sulfide-oxidizing bacteria. A comparison of the results of the continuous biogas treatment and batch tests suggests that the gas-liquid mass transfer rate of H(2)S was the rate-limiting step in the biological desulfurization in the reactor, indicating that the mass transfer efficiency of H(2)S needs to be improved to enhance the desulfurization performance. PMID:22925864

  18. Measurements of Heat Transfer Coefficients to Cylinders in Shallow Bubble Columns

    OpenAIRE

    Tow, Emily W.; Lienhard, John H.

    2014-01-01

    High heat transfer coefficients and large interfacial areas make bubble columns ideal for dehumidification. However, the effect of geometry on the heat transfer coefficients outside cooling coils in shallow bubble columns, such as those used in multi-stage bubble column dehumidifiers, is poorly understood. The generally-overlooked entry and coalescing regions become important in shallow bubble columns, and there is disagreement on the effects of the coil and column diameters. In this paper, a...

  19. The terminal rise velocity of bubble in a liquid column

    International Nuclear Information System (INIS)

    Full text of publication follows: As it is know, buoyancy and drag forces govern bubble rising velocity in a liquid column. These forces strongly depend on fluid proprieties and gravity as well as bubble equivalent diameter. The present work reports about a set of experiments bubble rising velocity in a liquid column using liquid with different kinematics viscosity. Records of terminal velocity were obtained, over a wide range of dynamic viscosity. The results show that the terminal rise velocity of bubble is strongly influenced by the effect of kinematics viscosity. The interpretation of physical phenomenon is considered. The set data permit to have a game of terminal velocities of 7.96 - 32.86 cm.s-1 with Reynolds number of 0.8 - 7491. The bubble movement is recorded with a camera video, which will be presented. Our aim goal is to present an original set data and the results are discussed in light of theory of two-phase flow. Prediction of bubble terminal velocity is discussed, so as, the range of applicability. (author)

  20. Study of droplet entrainment from bubbling surface in a bubble column

    International Nuclear Information System (INIS)

    In a bubble column droplets are ejected from the free surface by bubble bursting or splashing. Depending on their size, the droplets are partly carried away by the streaming gas or fall back to the bubbling surface by gravity force. Experiments have been carried out to determine the void fraction in the column by means of an optical probe. In the interfacial zone the bubble bursting process was captured with a high-speed video camera. Simultaneous measurements were made of size and velocity of droplets at several distances from the bubbling surface with a Phase-Doppler Anemometry. The bubble column can be divided into three regions: A lower zone with a flat profile of the local void fraction, a central zone where the flow regime is steady and an upper zone where the local void fraction grows rapidly. A two-parameter log-normal distribution function was proposed in order to describe the polydisperse distribution of droplet-size. Results were obtained concerning the entrainment, concentration, volume fraction and interfacial area of droplets. Finally, it was found that the turbulence intensity affects the droplet terminal velocity for droplets smaller than the Kolmogorov microscale

  1. Bubble column apparatus for gas-liquid heterogeneous chemistry studies

    Energy Technology Data Exchange (ETDEWEB)

    Shorter, J.A.; De Bruyn, W.J.; Hu, J.; Swartz, E.; Davidovits, P. [Boston College, Chestnut Hill, MA (United States); Worsnop, D.R.; Zahniser, M.S.; Kolb, C.E. [Aerodyne Research, Inc., Billerica, MA (United States)

    1995-05-01

    A bubble column apparatus has been designed to conduct time-resolved gas-liquid interaction studies of interest in atmospheric chemistry. In the apparatus, a low pressure gas flow, carrying trace gas diluted in helium carrier gas, is `bubbled` through a flask containing 3.5 L of temperature-controlled liquid. The outlet gas flow is then sampled by a differentially pumped mass spectrometer. The position of the bubble injector, which determines the gas-liquid contact time, is computer controlled by means of a stepping motor. Modeling of the gas uptake and the validation of the apparatus performance are described. The apparatus in the present configuration can measure Henry`s law coefficients (H) for nonreactive species in the range 0.01-2.0 M/atm. For reactive species (reaction rate k) the apparatus measures Hk{sup $HLF} values in the range 0.08-100 (M/atm) s{sup -HLF}. 43 refs., 8 figs.

  2. Xanthane production in the bubble column bioreactor; Xanthanproduktion im Blasensaeulen-Bioreaktor

    Energy Technology Data Exchange (ETDEWEB)

    II-Soon Suh

    1992-05-14

    The industrial production of xanthane occurs in batch operation in stirred boiler reactors. The enrichment of the product in the culture medium causes an extreme increase of viscosity during strongly pseudoplastic flow behavior. Because of inhomogeneous distribution of the shear gradient in the stirred boiler, local deviations from the optimal fermentation conditions can occur (temperature, pH, oxygen supply); even stagnant regions may form at the walls. The suitability of tower reactors for xanthane production was investigated in the dissertation. The bubble column is by far superior to other reactor types (airlift, three-phase fluidized bed, stirred boiler, immersion-type beam reactor) with regard to good mixing of highly viscous culture broths of Xanthomonas campestris. The rise of the large bubbles which fill almost the entire column cross-section practically leads to intensive mixing. This not only makes the bubble column suitable for production but allow also the establishment of dependable fundamentals for model formation. (orig./EF). [Deutsch] Die industrielle Herstellung von Xanthan erfolgt satzweise in Ruehrkesselreaktoren. Die Anreicherung des Produkts im Kulturmedium bewirkt einen extremen Anstieg der Viskositaet bei einem stark pseudoplastischen Fliessverhalten. Wegen der inhomogenen Verteilung des Schergefaelles im Ruehrkessel koennen lokale Abweichungen von den optimalen Fermentationsbedingungen (Temperatur, pH-Wert, Sauerstoffversorgung) auftreten; schliesslich bilden sich an den Waenden sogar stagnante Zonen aus. In dieser Arbeit sollte die Eignung von Turmreaktoren zur Xanthanproduktion untersucht werden. Die Blasensaeule erwies sich gegenueber anderen Reaktortypen (Airlift, Dreiphasenfliessbett, Ruehrkessel, Tauchstrahlreaktor) hinsichtlich der guten Vermischung hochviskoser Kulturbruehen von Xanthomonas campestris als deutlich ueberlegen. Der Aufstieg der Grossblasen, die praktisch den gesamten Saeulenquerschnitt erfassen, fuehrt zu einer

  3. Interpretation of CFD-Generated Bubble Swarms Oscillation for Bubble Column Bioreactor Performance Analysis

    Czech Academy of Sciences Publication Activity Database

    Fialová, Marie; Staykov, P.; Vlaev, S. D.

    Praha: Process Engineering Publisher, 2008, s. 859. ISBN 978-80-02-02050-9. [18th International Congress of Chemical and Process Engineering CHISA 2008. Praha (CZ), 24.08.2008-28.08.2008] R&D Projects: GA ČR GA104/07/1110 Institutional research plan: CEZ:AV0Z40720504 Keywords : bubble column bioreactor * gas holdup * cfd Subject RIV: CI - Industrial Chemistry, Chemical Engineering

  4. Effect of Surfactant on Homogeneous Regime Stability in Bubble Column.

    Czech Academy of Sciences Publication Activity Database

    Růžička, Marek; Večeř, Marek; Orvalho, Sandra; Drahoš, Jiří

    2008-01-01

    Roč. 63, 4 (2008) , s. 951– 967. ISSN 0009-2509 R&D Projects: GA ČR(CZ) GA104/05/2566; GA ČR GA104/06/1418; GA ČR GP104/06/P287; GA ČR(CZ) GA104/07/1110 Institutional research plan: CEZ:AV0Z40720504 Keywords : bubble column * gas holdup * surfactant Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 1.884, year: 2008

  5. Heat transfer to a horizontal cylinder in a shallow bubble column

    OpenAIRE

    Tow, Emily W.; Lienhard, John H.

    2014-01-01

    Heat transfer coefficient correlations for tall bubble columns are unable to predict heat transfer in shallow bubble columns, which have unique geometry and fluid dynamics. In this work, the heat transfer coefficient is measured on the surface of a horizontal cylinder immersed in a shallow air–water bubble column. Superficial velocity, liquid depth, and cylinder height and horizontal position with respect to the sparger orifices are varied. The heat transfer coefficient is found to increase w...

  6. Interfacial area concentration in bubble column and forced convective bubbly flow

    International Nuclear Information System (INIS)

    Although gas-liquid bubbly flows are encountered in various engineering fields, there are very few established theoretical foundations on the interfacial area concentration, which have been supported by extensive experimental data. From this point of view, a simple equation for the interfacial area concentration has been derived from the interfacial area transport equation. The derived theoretical equation has been modified to obtain experimentally supported predictive correlation. The obtained interfacial area correlation was validated by 459 data sets measured in bubble columns and forced convective bubbly flows under various conditions. These data sets covered extensive loop and flow conditions such as channel geometry (circular or rectangular channel), channel hydraulic equivalent diameter (9.0 mm ∼ 5500 mm), flow direction (vertical or horizontal flow), superficial gas velocity (0.000788 m/s ∼ 4.87 m/s), and superficial liquid velocity (0.00 m/s ∼ 6.55 m/s). The extensive database also covered wide ranges of physical properties such as liquid density (684 kg/m3 ∼ 1594 kg/m3), liquid viscosity (0.410 mPa·s ∼ 21.1 mPa·s), and surface tension (20.0 mN/m ∼ 75.0 mN/m). An excellent agreement was obtained between the developed semi-theoretical correlation and 459 data within an average relative deviation of ±22.0 %

  7. The Bubble Transport Mechanism: Indications for a bubble-mediated transfer of microorganisms from the sediment into the water column

    Science.gov (United States)

    Schmale, Oliver; Stolle, Christian; Schneider von Deimling, Jens; Leifer, Ira; Kießlich, Katrin; Krause, Stefan; Frahm, Andreas; Treude, Tina

    2015-04-01

    Gas releasing seep areas are known to impact the methane biogeochemistry in the surrounding sediment and water column. Due to microbial processes most of the methane is oxidized under anaerobic and aerobic conditions before the greenhouse gas can escape into the atmosphere. However, methane gas bubbles can largely bypass this microbial filter mechanism, enabling highly efficient transport of methane from the sediment towards the sea surface. Studies in the water column surrounding hydrocarbon seeps indicated an elevated abundance of methanotrophic microorganism in the near field of gas bubble plumes. The enhanced methane concentration in the seep-affected water column stimulates the activity of methane oxidizers and leads to a rapid rise in the abundance of methane-oxidizing microorganisms in the aging plume water. In our study we hypothesized that a bubble-mediated transport mechanisms between the benthic and pelagic habitats represents an exchange process, which transfers methanotrophic microorganisms from the sediment into the water column, a process we termed the "Bubble Transport Mechanism". This mechanism could eventually influence the pelagic methanotrophic community, thereby indirectly providing feedback mechanisms for dissolved methane concentrations in the water column and thus impacting the sea/atmosphere methane flux. To test our hypothesis, field studies were conducted at the "Rostocker Seep" site (Coal Oil Point seep area, California, USA). Catalyzed Reporter Deposition Fluorescence In Situ Hybridization (CARD-FISH) analyzes were performed to determine the abundance of aerobic and anaerobic methanotrophic microorganisms. Aerobic methane oxidizing bacteria were detected in the sediment and the water column, whereas anaerobic methanotrophs were detected exclusively in the sediment. The key device of the project was a newly developed "Bubble Catcher" used to collect naturally emanating gas bubbles at the sea floor together with particles attached to the

  8. Comparison between Airlift Photobioreactor and Bubble Column for Skeletonema Costatum Cultivation

    OpenAIRE

    Prasert Pavasant; Sorawit Powtongsook; Saranya Monkonsit

    2011-01-01

    The cultivation of diatom Skeletonema costatum was achieved in airlift photobioreactor and the system performance was compared to that of bubble column. The standard F/2 medium (Guillard’s medium) for typical diatom cultivation could only yield the best growth character when the silicon concentration increased 4 times the normal value. In terms of cell growth, the airlift photobioreactor provided better performance than the bubble column where the maximum cell concentration, specific growth r...

  9. Ultrasonic measurements of bubble shape and liquid film thickness of a Taylor bubble rising in a stagnant water column

    International Nuclear Information System (INIS)

    The present paper reports a preliminary study of direct measurement of the equilibrium thickness of the falling film around a Taylor bubble in a stagnant water column, using the pulse-echo ultrasonic technique. The experiments were conducted in an acrylic tube of 1.8 m long with inner diameter of 25.21 mm and wall thickness of 6.8 mm. A Taylor bubble was formed by the invertion of the pipe, sealed at the ends and partially filled with water to leave an air pocket of length L0. The rising Taylor bubble was detected by a transducer located 400 mm from the top of the pipe. Ten measurements were made for each of the four channels of the ultrasonic system, using the same settings of the system parameters, totaling 40 measured bubbles. A simplified Brown's model for the thickness around a Taylor bubble was used to calculate a reference value of the parameter being measured. We found that the values directly measured by the ultrasonic technique were in good agreement with the reference value calculated and thus conclude that the pulse-echo ultrasonic technique can be applied to directly measure the thickness of the falling film around the Taylor bubbles in acrylic tubes. The errors between the experimental and the reference values were in the order of 10%. (author)

  10. Distribution characteristics of holdups in a multi-stage bubble column using electrical resistance tomography

    Institute of Scientific and Technical Information of China (English)

    Haibo Jin; Yicheng Lian; Yujian Qin; Suohe Yang; Guangxiang He

    2013-01-01

    Based on the principle of chemical reaction engineering,the addition of perforated plates can improve the performance of conventional bubble column and decrease the backmixing behaviors.The distribution characteristics of gas holdup in a multi-stage bubble column embedded with five types of sieve plates and three types of tongue plates were studied using electrical resistance tomography (ERT).The effects of superficial gas velocity and the geometric design of perforated plates on the gas holdup and its radial distribution above and below the plates of the bubble column were discussed.Experimental results show ERT is suitable as an online monitoring tool to provide useful information on the hydrodynamic parameters of multi-stage bubble columns.With increasing superficial gas velocity,local gas holdup increases,and gas holdup below the plate increases with decrease of free area (%FA),hole diameters or angle of tongue plates.ERT technique facilitates noninvasive and nonintrusive visualization of cross-sectional distribution of gas holdup in a bubble column.

  11. Numerical investigation on hydrodynamic performance of liquid lead lithium bubble column using population balance model

    International Nuclear Information System (INIS)

    Highlights: • Flow behaviors with H and Vg were simulated using CFD coupled with PBM. • Bubble size and gas holdup are mainly determined by vortical flow. • Interfacial area enhanced by increasing Vg and H, but the enhancement effect is not obvious while the Vg is too fast. - Abstract: Using bubble column to extract tritium from lead lithium (Pb–17Li) eutectic is an effective way in the process of tritium extraction in liquid blanket system, where the hydrodynamic characteristics of the gas–liquid two-phase flow in the columns play a very important role. In order to understand the two-phase flow details and investigate the influence factors on the hydrodynamic performance, in this paper the flow behaviors in the cylindrical bubble columns with different heights and purge gas inlet velocities using computational fluid dynamics coupled with population balance model were simulated. Liquid flow field, bubble Sauter mean diameter, time-averaged gas holdup and two-phase interfacial area for the different cases were obtained and compared. The simulation results showed good agreement with previous studies, and which indicated that bubble size and gas holdup formation are mainly determined by vortical flow. In addition, interfacial area can be enhanced by increasing the purge gas inlet velocity and column height. However, the enhancement effect will trail away when the gas inlet velocity is too fast, and the contribution of column height is relatively small

  12. Ozonation of acid yellow 17 dye in a semi-batch bubble column

    International Nuclear Information System (INIS)

    A semi-batch bubble column was used to evaluate the effect of ozonation on the removal of acid yellow 17 dye from water. Results indicate that ozonation is very effective at removing acid yellow 17 dye from synthetic textile wastewater. The ozone consumed to apparent dye removal ratio ranged from 2 to 15,000 mg ozone per mg of dye decolorized and was dependent on both ozonation time and apparent dye concentration. The biodegradability of the dye wastewater was evaluated by monitoring changes in 5-day biochemical oxygen demand (BOD5) with respect to chemical oxygen demand (COD). Results indicate that the wastewater biodegradability increased with an increase in ozonation time. Film theory was used to kinetically model the gas-liquid reactions occurring in the reactor. Modeling results indicated that during the first 10-15 min of ozonation, the system could be characterized by a fast, pseudo-first-order regime. With continued ozonation, system kinetics transitioned through a moderate then to a slow regime. Successful modeling of this period required use of a kinetic equation corresponding to a more inclusive condition. Model results are presented

  13. The influence of polymeric membrane gas spargers on hydrodynamics and mass transfer in bubble column bioreactors

    DEFF Research Database (Denmark)

    Tirunehe, Gossay; Norddahl, B.

    2016-01-01

    Gas sparging performances of a flat sheet and tubular polymeric membranes were investigated in 3.1 m bubble column bioreactor operated in a semi batch mode. Air–water and air–CMC (Carboxymethyl cellulose) solutions of 0.5, 0.75 and 1.0 % w/w were used as interacting gas–liquid mediums. CMC....../s. The study indicated that the tubular membrane sparger produced the highest gas holdup and densely populated fine bubbles with narrow size distribution. An increase in liquid viscosity promoted a shift in bubble size distribution to large stable bubbles and smaller specific interfacial area. The tubular...... membrane sparger achieved greater interfacial area and an enhanced overall mass transfer coefficient (KLa) by a factor of 1.2–1.9 compared to the flat sheet membrane....

  14. Gas-Liquid Interfacial Area, Bubble Size and Liquid-Phase Mass Transfer Coefficient in a Three-Phase External Loop Airlift Bubble Column

    OpenAIRE

    Yoshimoto, M; Suenaga, S.; Furumoto, K.; Fukunaga, K.; Nakao, Katsumi

    2007-01-01

    The interfacial area a was measured by the sulfite oxidation method in a three-phase external loop airlift bubble column suspending completely the different concentrations of ion exchange resin particles in aqueous carboxymethyl cellulose (CMC) solutions with a wide range of viscosity. The column had been previously studied for the circulating liquid velocity UL, gas holdup G and volumetric gas-liquid oxygen transfer coefficient kLa in the two- and three-phase systems. The average bubble siz...

  15. The influence of polymeric membrane gas spargers on hydrodynamics and mass transfer in bubble column bioreactors.

    Science.gov (United States)

    Tirunehe, Gossaye; Norddahl, B

    2016-04-01

    Gas sparging performances of a flat sheet and tubular polymeric membranes were investigated in 3.1 m bubble column bioreactor operated in a semi batch mode. Air-water and air-CMC (Carboxymethyl cellulose) solutions of 0.5, 0.75 and 1.0 % w/w were used as interacting gas-liquid mediums. CMC solutions were employed in the study to simulate rheological properties of bioreactor broth. Gas holdup, bubble size distribution, interfacial area and gas-liquid mass transfer were studied in the homogeneous bubbly flow hydrodynamic regime with superficial gas velocity (U G) range of 0.0004-0.0025 m/s. The study indicated that the tubular membrane sparger produced the highest gas holdup and densely populated fine bubbles with narrow size distribution. An increase in liquid viscosity promoted a shift in bubble size distribution to large stable bubbles and smaller specific interfacial area. The tubular membrane sparger achieved greater interfacial area and an enhanced overall mass transfer coefficient (K La) by a factor of 1.2-1.9 compared to the flat sheet membrane. PMID:26857370

  16. Gas-Liquid Mass Transfer Characteristics in a Gas-Liquid-Solid Bubble Column under Elevated Pressure and Temperature

    Institute of Scientific and Technical Information of China (English)

    Haibo Jin; Suohe Yang; Guangxiang He; Delin Liu; Zemin Tong; Jianhua Zhu

    2014-01-01

    abstract The volumetric mass transfer coefficient kLa of gases (H2, CO, CO2) and mass transfer coefficient kL on liquid par-affin side were studied using the dynamic absorption method in slurry bubble column reactors under elevated temperature and elevated pressure. Meanwhile, gas-holdup and gas-liquid interfacial area a were obtained. The effects of temperature, pressure, superficial gas velocity and solid concentration on the mass transfer coeffi-cient were discussed. Experimental results show that the gas-liquid volumetric mass transfer coefficient kLa and interfacial area a increased with the increase of pressure, temperature, and superficial gas velocity, and decreased with the slurry concentration. The mass transfer coefficient kL increased with increasing superficial gas velocity and temperature and decreased with higher slurry concentration, while it changed slightly with pressure. Ac-cording to analysis of experimental data, an empirical correlation is obtained to calculate the values of kLa for H2 (CO, CO2) in the gas-paraffin-quartz system in a bubble column under elevated temperature and elevated pressure.

  17. Characterization of velocity and shape of rising bubbles in a stagnant liquid vertical column by ultrasonic and visualization techniques

    International Nuclear Information System (INIS)

    The present paper reports a preliminary study of velocities of rising bubbles in a stagnant water vertical column. Rising bubble velocities were measure by using the pulse-echo ultrasonic technique and high speed digital camera visualization technique, which have been used in previous studies of two-phase gas-liquid flow in horizontal and slightly inclined circular tubes. Four types of rising bubbles were identified by flow visualization. We found that velocities of three types of rising bubbles agree reasonably well with available correlations, while velocities of one type of rising bubbles differ significantly from correlations. (author)

  18. Technical Note: Detection of gas bubble leakage via correlation of water column multibeam images

    Directory of Open Access Journals (Sweden)

    J. Schneider von Deimling

    2012-03-01

    Full Text Available Hydroacoustic detection of natural gas release from the seafloor has been conducted in the past by using singlebeam echosounders. In contrast, modern multibeam swath mapping systems allow much wider coverage, higher resolution, and offer 3-D spatial correlation. Up to the present, the extremely high data rate hampers water column backscatter investigations and more sophisticated visualization and processing techniques are needed. Here, we present water column backscatter data acquired with a 50 kHz prototype multibeam system over a period of 75 seconds. Display types are of swath-images as well as of a "re-sorted" singlebeam presentation. Thus, individual and/or groups of gas bubbles rising from the 24 m deep seafloor clearly emerge in the acoustic images, making it possible to estimate rise velocities. A sophisticated processing scheme is introduced to identify those rising gas bubbles in the hydroacoustic data. We apply a cross-correlation technique adapted from particle imaging velocimetry (PIV to the acoustic backscatter images. Temporal and spatial drift patterns of the bubbles are assessed and are shown to match very well to measured and theoretical rise patterns. The application of this processing to our field data gives clear results with respect to unambiguous bubble detection and remote bubble rise velocimetry. The method can identify and exclude the main source of misinterpretations, i.e. fish-mediated echoes. Although image-based cross-correlation techniques are well known in the field of fluid mechanics for high resolution and non-inversive current flow field analysis, we present the first application of this technique as an acoustic bubble detector.

  19. Gas holdup in cyclone-static micro-bubble flotation column.

    Science.gov (United States)

    Li, Xiaobing; Zhu, Wei; Liu, Jiongtian; Zhang, Jian; Xu, Hongxiang; Deng, Xiaowei

    2016-04-01

    The present work has been carried out to investigate the effect of process variables on gas holdup and develop an empirical equation and a neural network model for online process control of the gas holdup based on the operating variables. In this study, the effect of process variables (nozzle diameter, circulation pressure, aeration rate, and frother dosage) on gas holdup in a cyclone-static micro-bubble flotation column of an air/oily wastewater system was investigated. Gas holdup was estimated using a pressure difference method and an empirical equation was proposed to predict gas holdup. A general regression neural network (GRNN) model was also introduced to predict gas holdup for the cyclone-static micro-bubble flotation column. The predictions from the empirical equation and the GRNN are in good agreement with the experiment data for gas holdup, while the GRNN provides higher accuracy and stability compared with that of the empirical equation. PMID:26293176

  20. A novel closed system bubble column photobioreactor for detailed characterisation of micro and macroalgal growth

    OpenAIRE

    Holdt, Susan Løvstad; Christensen, L; Iversen, J.J.L.

    2013-01-01

    Growth of the marine microalgae Tetraselmis striata Butcher and macroalgae Chondrus crispus Stackhouse was investigated in batch cultures in a closed system bubble column photobioreactor. A laboratory cultivation system was constructed that allowed on-line monitoring of temperature, pH and dissolved oxygen tension and was intended for characterization of photoautotrophic growth. Regulation of temperature was done by cooling and carbon dioxide additions regulated pH. The carbon dioxide additio...

  1. Comparison between Airlift Photobioreactor and Bubble Column for Skeletonema Costatum Cultivation

    Directory of Open Access Journals (Sweden)

    Prasert Pavasant

    2011-10-01

    Full Text Available The cultivation of diatom Skeletonema costatum was achieved in airlift photobioreactor and the system performance was compared to that of bubble column. The standard F/2 medium (Guillard’s medium for typical diatom cultivation could only yield the best growth character when the silicon concentration increased 4 times the normal value. In terms of cell growth, the airlift photobioreactor provided better performance than the bubble column where the maximum cell concentration, specific growth rate, and productivity in the airlift were 4.6 x 106 cell mL-1, 0.07 h-1, and 6.4 x 104 cell s-1 compared with 1.8 x 106 cell mL-1, 0.04 h-1, and 2.2 x 104 cell s-1 in the bubble column of the same size (3L and operated at the same aeration rate (superficial velocity = 1.5 cm s-1 and light intensity (34 μmol photons m−2 s−1. This was because the airlift photobioreactor allowed circulatory flow in the system which helps prevent cell precipitation and enhance light utilization efficiency. The optimal operating conditions in the airlift system which was found most optimal to cell growth were: the ratio between downcomer and riser cross sectional area (Ad:Ar of 3.27, superficial gas velocity 1.5 cm s−1 and the light intensity 34 μmol photons m−2 s−1. Preliminary economical assessment on the cultivation of S. costatum in airlift system compared with that in bubble column was carried out, whereas the analysis for nutritional values of the obtained biomass indicated relatively high protein content.

  2. Effect of Solids on Flow Regime Transition in Three-Phase Bubble Columns

    Czech Academy of Sciences Publication Activity Database

    Mena, P. C.; Rocha, F. A.; Teixeira, J. A.; Drahoš, Jiří; Růžička, Marek

    Praha : Process Engineering Publisher, 2004, s. 1103. ISBN 80-86059-40-5. [International Congress of Chemical and Process Engineering CHISA 2004 /16./. Praha (CZ), 22.08.2004-26.08.2004] Grant ostatní: HPMT(XE) CT/2000/00074 Institutional research plan: CEZ:AV0Z4072921 Keywords : flow regime * bubble columns * transition Subject RIV: CI - Industrial Chemistry, Chemical Engineering

  3. Global and Local Hydrodynamics of Bubble Columns – Effect of Gas Distributor.

    Czech Academy of Sciences Publication Activity Database

    Sharaf, S.; Zedníková, Mária; Růžička, Marek; Azzopardi, B.J.

    2016-01-01

    Roč. 288, MAR 15 (2016), s. 489-504. ISSN 1385-8947 R&D Projects: GA MŠk(CZ) LD13018 Grant ostatní: EPSRC(GB) EP/F016050/1 Institutional support: RVO:67985858 Keywords : bubble columns * wire mesh sensor * void fraction Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 4.321, year: 2014

  4. Preliminary Assessments of Combined Effects of Surface Tension and Viscosity on Bubble Column Hydrodynamics

    Czech Academy of Sciences Publication Activity Database

    Olivieri, G.; Grillo, S.; D’Errico, G.; Marzocchella, A.; Růžička, Marek; Salatino, P.

    Vol. Part 2. Milan o: Aidic Servizi, 2013 - (Pierucci, S.; Klemeš, J.), 1579-1584-6 ISBN 978-88-95608-23-5. ISSN 1974-9791. [International Conference on Chemical and Process Engineering /11./. Milan (IT), 02.06.2013-05.06.2013] Institutional support: RVO:67985858 Keywords : bubble column hydrodynamics * viscosity * sodium Subject RIV: CI - Industrial Chemistry, Chemical Engineering http://www.aidic.it/cet/13/32/programma.html#264.pdf

  5. ANALYSIS OF TRICKLE BED AND PACKED BUBBLE COLUMN BIOREACTORS FOR COMBINED CARBON OXIDATION AND NITRIFICATION

    Directory of Open Access Journals (Sweden)

    Iliuta I.

    2002-01-01

    Full Text Available Biological removal of nitrogen and carbon by combined nitrification-oxidation in gas-liquid trickle-bed reactors (TBRs and packed bubble columns (PBCs was analyzed theoretically using a transient two-dimensional model. The model describes TBR and PBC performances at steady state as well as their transient response to a pulse or step increase in inlet methanol and NH4+-nitrogen concentrations. The hydrodynamic parameters were determined from residence time distribution measurements, using an imperfect pulse method for time-domain analysis of nonideal pulse tracer response. A transient diffusion model of the tracer in the porous particle coupled with the piston-dispersion-exchange model was used to interpret the residence time distribution curves obtained. Gas-liquid mass transfer parameters were determined by a stationary method based on the least-squares fit of the calculated concentration profiles in gas phase to the experimental values. Analysis of steady-state performances showed that under like operating conditions, the TBR outperforms the PBC in terms of conversions. A pulse change in the inlet methanol or NH4+-nitrogen concentration causes a negligible transient change in the outlet methanol concentration and a negligible or high transient change in the outlet NH4+-nitrogen concentration. A step change in the inlet methanol concentration causes the negligible transient change in the methanol outlet concentration and a relatively important transient change in the NH4+-nitrogen outlet concentration. A step increase in the NH4+-nitrogen inlet concentration induces a drastic transient change in the NH4+-nitrogen outlet concentration but a negligible transient change in the methanol outlet concentration.

  6. Experimental investigation of the effect of liquid viscosity on slug flow in small diameter bubble column

    Directory of Open Access Journals (Sweden)

    Azzopardi Barry John

    2012-04-01

    Full Text Available The effect of liquid viscosity on slug flow in a 50 mm diameter bubble column was investigated experimentally using air-silicone oil as operating fluid with silicone oil of viscosities 5, 100, 1000 and 5000 mPa.s. Data was collected using Electrical Capacitance Tomography (ECT, a non-intrusive advanced instrumentation measuring technique and the high Speed Video Camera, through which the slug parameters such as length of Taylor bubbles and liquid slug, void fraction in Taylor bubbles and liquid slug, slug frequency, film thickness and pressure gradient in the slug, were measured and analyzed. The analysis was done using the void fraction time series, probability density function and power spectral density plots. Superficial gas velocities of 0.02≤Ugs≤0.361 m/s were used in the experiment. It was also observed that as viscosity increases, slug frequency, structure velocity, length of liquid slug, void fraction in liquid slug and void fraction in Taylor bubbles decreases; while the length of Taylor bubble, film thickness and pressure gradient in the slug increases.

  7. Bubble Shuttle: A newly discovered transport mechanism, which transfers microorganisms from the sediment into the water column

    Science.gov (United States)

    Schmale, O.; Stolle, C.; Leifer, I.; Schneider von Deimling, J.; Kiesslich, K.; Krause, S.; Frahm, A.; Treude, T.

    2013-12-01

    The diversity and abundance of methanotrophic microorganisms is well studied in the aquatic environment, indicating their importance in biogeochemical cycling of methane in the sediment and the water column. However, whether methanotrophs are distinct populations in these habitats or are exchanged between benthic and pelagic environments, remains an open question. Therefore, field studies were conducted at the 'Rostocker Seep' site (Coal Oil Point seep area, California, USA) to test our hypothesis that methane-oxidizing microorganisms can be transported by gas bubbles from the sediment into the water column. The natural methane emanating location 'Rostocker Seep' showed a strong surface water oversaturation in methane with respect to the atmospheric equilibrium. Catalyzed Reporter Deposition Fluorescence In Situ Hybridization (CARD-FISH) analyzes were performed to determine the abundance of aerobic and anaerobic methanotrophic microorganisms. Aerobic methane oxidizing bacteria were detected in the sediment and the water column, whereas anaerobic methanotrophs were detected exclusively in the sediment. The key device of the project was the newly developed "Bubble Catcher" used to collect naturally emanating gas bubbles at the sea floor together with particles attached to the bubble surface rim. Bubble Catcher experiments were carried out directly above a natural bubble release spot and on a reference site at which artificially released gas bubbles were caught, which had no contact with the sediment. CARD-FISH analyzes showed that aerobic methane oxidizing bacteria were transported by gas bubbles from the sediment into the water column. In contrast anaerobic methanotrophs were not detected in the bubble catcher. Further results indicate that this newly discovered Bubble Shuttle transport mechanism might influence the distribution pattern of methanotrophic microorganisms in the water column and even at the air-sea interface. Methane seep areas are often characterized

  8. Heat Transfer in Bubble Columns with High Viscous and Low Surface Tension Media

    International Nuclear Information System (INIS)

    Axial and overall heat transfer coefficients were investigated in a bubble column with relatively high viscous and low surface tension media. Effects of superficial gas velocity (0.02-0.1 m/s), liquid viscosity (0.1-3 Pa·s) and surface tension (66.1-72.9x10-3 N/m) on the local and overall heat transfer coefficients were examined. The heat transfer field was composed of the immersed heater and the bubble column; a vertical heater was installed at the center of the column coaxially. The heat transfer coefficient was determined by measuring the temperature differences continuously between the heater surface and the column which was bubbling in a given operating condition, with the knowledge of heat supply to the heater. The local heat transfer coefficient increased with increasing superficial gas velocity but decreased with increasing axial distance from the gas distributor and liquid surface tension. The overall heat transfer coefficient increased with increasing superficial gas velocity but decreased with increasing liquid viscosity or surface tension. The overall heat transfer coefficient was well correlated in terms of operating variables such as superficial gas velocity, liquid surface tension and liquid viscosity with a correlation coefficient of 0.91, and in terms of dimensionless groups such as Nusselt, Reynolds, Prandtl and Weber numbers with a correlation of 0.92; h=2502UG0.236L-0.250L-0.028 Nu=3.25Re0.180Pr-0.067We0.028

  9. Heat Transfer in Bubble Columns with High Viscous and Low Surface Tension Media

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Wan Tae; Lim, Dae Ho; Kang, Yong [Chungnam National University, Daejeon (Korea, Republic of)

    2014-08-15

    Axial and overall heat transfer coefficients were investigated in a bubble column with relatively high viscous and low surface tension media. Effects of superficial gas velocity (0.02-0.1 m/s), liquid viscosity (0.1-3 Pa·s) and surface tension (66.1-72.9x10{sup -3} N/m) on the local and overall heat transfer coefficients were examined. The heat transfer field was composed of the immersed heater and the bubble column; a vertical heater was installed at the center of the column coaxially. The heat transfer coefficient was determined by measuring the temperature differences continuously between the heater surface and the column which was bubbling in a given operating condition, with the knowledge of heat supply to the heater. The local heat transfer coefficient increased with increasing superficial gas velocity but decreased with increasing axial distance from the gas distributor and liquid surface tension. The overall heat transfer coefficient increased with increasing superficial gas velocity but decreased with increasing liquid viscosity or surface tension. The overall heat transfer coefficient was well correlated in terms of operating variables such as superficial gas velocity, liquid surface tension and liquid viscosity with a correlation coefficient of 0.91, and in terms of dimensionless groups such as Nusselt, Reynolds, Prandtl and Weber numbers with a correlation of 0.92; h=2502U{sub G}{sup 0.236}{sub L}{sup -0.250}{sub L}{sup -}0{sup .028} Nu=3.25Re{sup 0.180}Pr{sup -0.067}We{sup 0.028}.

  10. Contactless measurement of phase and concentration distributions in bubble columns using positron emitting radionuclides

    International Nuclear Information System (INIS)

    Positron emission tomography (PET) is a well-established method for studying metabolic processes in humans and in use as a medical diagnostic procedure (metabolism, blood perfusion, metastasis detection). The present project was dedicated to a nonmedical application of this imaging method, namely to the development and use of a PET tomograph for studying the behaviour of foam in bubble columns on the ''SchaumPET'' test stand. This paper deals in particular with the technical realisation of the project and the image acquisition methods used. The capacity of positron emission tomography to detect the accumulation of a surfactant in a foam layer is demonstrated for the example of sodium capronate

  11. Pico-nano bubble column flotation using static mixer-venturi tube for Pittsburgh No. 8 coal seam

    Institute of Scientific and Technical Information of China (English)

    Peng Felicia F.; Yu Xiong

    2015-01-01

    The flotation process is a particle-hydrophobic surface-based separation technique. To improve the essential flotation steps of collision and attachment probabilities, and reduce the step of detachment probabilities between air bubbles and hydrophobic particles, a selectively designed cavitation venturi tube combined with a static mixer can be used to generate very high numbers of pico and nano bubbles in a flotation column. Fully embraced by those high numbers of tiny bubbles, hydrophobic particles readily attract the tiny bubbles to their surfaces. The results of column flotation of Pittsburgh No. 8 seam coal are obtained in a 5.08 cm ID and 162 cm height flotation column equipped with a static mixer and cavitation venturi tube, using kerosene as collector and MIBC as frother. Design of the experimental procedure is combined with a statistical two-stepwise analysis to determine the optimal operating conditions for maximum recovery at a specified grade. The effect of independent variables on the responses has been explained. Combustible material recovery of 85–90% at clean coal product of 10–11%ash is obtained from feed of 29.6%ash, with a much-reduced amount of frother and collector than that used in conventional column flotation. The column flotation process utilizing pico and nano bubbles can also be extended to the lower limit and upper limit of particle size ranges, minus 75 lm and 300–600 lm, respectively, for better recovery.

  12. Hydrodynamic and Mass Transfer Properties in a Three Phase External Loop Airlift Compared with a Three Phase Internal Loop Airlift and a Slurry Bubble Column

    OpenAIRE

    Nakao, K; Suenaga, S.; Furumoto, K.; Yoshimoto, M; Fukunaga, K.

    2007-01-01

    The effects of suspended solid particles on the hydrodynamic and mass transfer properties were experimentally studied in a wide range of the superficial gas velocity, solid particle property and liquid viscosity in an external loop airlift bubble column in comparison with those in an internal loop airlift bubble column as well as a normal bubble column. The circulating liquid velocities UL, gas holdups G and volumetric gas liquid oxygen transfer coefficients kLa in the riser of the external ...

  13. Bubbles

    DEFF Research Database (Denmark)

    Dholakia, Nikhilesh; Turcan, Romeo V.

    2013-01-01

    A goal of our ongoing research stream is to develop a multidisciplinary metatheory of bubbles. In this viewpoint paper we put forward a typology of bubbles by comparing four types of assets – entertainment, commodities, financial securities (stocks), and housing properties – where bubbles could and...... do form occasionally. Cutting across and comparing such varied asset types provides some rich insights into the nature of bubbles – and offers an inductive way to arrive at the typology of bubbles....

  14. A bubble column evaporator with basic flat-plate condenser for brackish and seawater desalination.

    Science.gov (United States)

    Schmack, Mario; Ho, Goen; Anda, Martin

    2016-01-01

    This paper describes the development and experimental evaluation of a novel bubble column-based humidification-dehumidification system, for small-scale desalination of saline groundwater or seawater in remote regions. A bubble evaporator prototype was built and matched with a simple flat-plate type condenser for concept assessment. Consistent bubble evaporation rates of between 80 and 88 ml per hour were demonstrated. Particular focus was on the performance of the simple condenser prototype, manufactured from rectangular polyvinylchlorid plastic pipe and copper sheet, a material with a high thermal conductivity that quickly allows for conduction of the heat energy. Under laboratory conditions, a long narrow condenser model of 1500 mm length and 100 mm width achieved condensate recovery rates of around 73%, without the need for external cooling. The condenser prototype was assessed under a range of different physical conditions, that is, external water cooling, partial insulation and aspects of air circulation, via implementing an internal honeycomb screen structure. Estimated by extrapolation, an up-scaled bubble desalination system with a 1 m2 condenser may produce around 19 l of distilled water per day. Sodium chloride salt removal was found to be highly effective with condensate salt concentrations between 70 and 135 µS. Based on findings and with the intent to reduce material cost of the system, a shorter condenser length of 750 mm for the non-cooled (passive) condenser and of 500 mm for the water-cooled condenser was considered to be equally efficient as the experimentally evaluated prototype of 1500 mm length. PMID:26086612

  15. Heat transition and effective shear gradient in bubble column bioreactors with xanthane solutions. Waermeuebergang und effektives Schergefaelle in Blasensaeulen-Bioreaktoren mit Xanthan-Loesungen

    Energy Technology Data Exchange (ETDEWEB)

    Zaidi, A.; Bourziza, H.; Echihabi, L.

    1987-01-01

    In a ventilated bubble column reactor of the diameter 10 centimeters and the dispersion height 160 centimeters, operated with highly pseudoplastic xanthane solutions, heat transition figures were measured. The ..cap alpha..-values obtained were correlated. In this process the wide range of variation of the index of fluid flow (1-1.18) permitted to establish an effective shear gradient, for which different approaches have been reported in literature. The informative value of the correlation established was verified by a comparison with other relationships known from literature.

  16. Numerical investigation of a bubble-column photo-bioreactor design for biodiesel production from microalgae

    Energy Technology Data Exchange (ETDEWEB)

    Seo, I.H.; Lee, I.B.; Hwang, H.S.; Hong, S.W.; Bitog, J.P.; Kwon, K.S.; Choi, J.S.; Song, S.H. [Seoul National Univ., Seoul (Korea, Democratic People' s Republic of). Dept. of Rural Systems Engineering and Research Inst. for Agriculture and Life Sciences

    2010-07-01

    Biodiesel made from vegetable oil is among the most desirable of renewable energy sources because it can be a substitute for diesel oil. However, biodiesel from soybean or corn can be confronted with a food crisis. Microalgae is a new biodiesel source which contains high oil lipids with a high growth rate, and which also offers value-added products from the residue, such as cosmetics, health functional food or pharmaceuticals. Microalgae are best cultivated in photo-bioreactors (PBRs) where light, nutrients, carbon dioxide and temperature can be controlled. Despite the current availability of PBRs, only a few can be practically used for mass production. Computational fluid dynamics (CFD) was used in this study to design an optimum bubble-column PBR for mass production of microalgae. Multi-phase models including bubble movement, meshes and time step independent tests were considered to develop the 3-dimensional CFD model. Particle Image Velocimetry (PIV) tests were used to enhance and validate the model. Different types of PBRs were simulated and compared quantitatively with the microalgae's growth model.

  17. A method for predicting the number of active bubbles in sonochemical reactors.

    Science.gov (United States)

    Merouani, Slimane; Ferkous, Hamza; Hamdaoui, Oualid; Rezgui, Yacine; Guemini, Miloud

    2015-01-01

    Knowledge of the number of active bubbles in acoustic cavitation field is very important for the prediction of the performance of ultrasonic reactors toward most chemical processes induced by ultrasound. The literature in this field is scarce, probably due to the complicated nature of the phenomena. We introduce here a relatively simple semi-empirical method for predicting the number of active bubbles in an acoustic cavitation field. By coupling the bubble dynamics in an acoustical field with chemical kinetics occurring in the bubble during oscillation, the amount of the radical species OH and HO2 and molecular H2O2 released by a single bubble was estimated. Knowing that the H2O2 measured experimentally during sonication of water comes from the recombination of hydroxyl (OH) and perhydroxyl (HO2) radicals in the liquid phase and assuming that in sonochemistry applications, the cavitation is transient and the bubble fragments at the first collapse, the number of bubbles formed per unit time per unit volume is then easily determined using material balances for H2O2, OH and HO2 in the liquid phase. The effect of ultrasonic frequency on the number of active bubbles was examined. It was shown that increasing ultrasonic frequency leads to a substantial increase in the number of bubbles formed in the reactor. PMID:25127247

  18. Detached eddy simulations of Taylor bubbles rising in stagnant liquid columns

    Science.gov (United States)

    Shaban, Hassan; Tavoularis, Stavros

    2015-11-01

    The rise of a single air Taylor bubble in a vertical circular tube filled with stagnant water was investigated numerically using the Volume Of Fluid (VOF) method to model the phase distribution and the Detached Eddy Simulation (DES) method for turbulence modelling. The predictions were in good quantitative agreement with previous experimental results. The simulation results provided insight into bubble shedding in the wake of the Taylor bubble, frictional pressure drop along the tube and scalar dispersion caused by the passage of the Taylor bubble. The interaction between adjacent Taylor bubbles and the process of Taylor bubble coalescence were also examined in detail. Supported by NSERC and UNENE.

  19. Benchmarking of the construct of dimensionless correlations regarding batch bubble columns with suspended solids: Performance of the Pressure Transform Approach

    CERN Document Server

    Hristov, Jordan

    2010-01-01

    Benchmark of dimensionless data correlations pertinent to batch bubble columns (BC) with suspended solids has been performed by the pressure transform approach (PTA). The main efforts have addressed the correct definition of dimensionless groups referring to the fact that solids dynamics and the bubble dynamics have different velocity and length scales. The correct definition of the initial set of variable in the classical dimensional analysis depends mainly on the experience of the investigator while the pressure transform approach (PTA) avoids errors at this initial stage. PTA addresses the physics of the phenomena occurring in complex systems involving many phases and allows straightforward definitions of dimensionless numbers.

  20. Hydrolysis of Olive Oil with Immobilized Lipase in a Tapered Column Reactor

    Institute of Scientific and Technical Information of China (English)

    杨伯伦; 赵国胜; 林宏业

    2003-01-01

    Lipase was immobilized in ion exchange resin and then used in the hydrolysis of olive oil to produce fatty acids and glycerol. The time course of hydrolysis of olive oil was investigated in a stirred tank reactor using both of the free and immobilized lipases to find the yield of activity of immobilized enzyme. Continuous hydrolysis of olive oil was also carried out in a tapered column reactor and a cylindrical column reactor with a bottom ID of 10 mm at different upward flow rates. It can be known from experimental results that the degree of hydrolysis of olive oil in the tapered column reactor is moderately better than that in the cylindrical column reactor, the pressure drop in the tapered column reactor is much smaller than that in the cylindrical column reactor.

  1. EFFECT OF PHOTOPERIODICITY ON CO2 FIXATION BY Chlorella vulgaris Buitenzorg IN BUBBLE COLUMN PHOTOBIOREACTOR FOR FOOD SUPPLEMENT PRODUCTION

    Directory of Open Access Journals (Sweden)

    Roekmijati Widaningroem Soemantojo

    2004-08-01

    Full Text Available To reduce the level of CO2 content in air, effort on converting CO2 to useful products is required. One of the alternatives includes CO2 fixation to produce biomass using Chlorella vulgaris Buitenzorg. Chlorella vulgaris Buitenzorg is applied for production of food supplement. Chlorella vulgaris Buitenzorg is also easy to handle due to its superior adaptation. Currently, Chlorella vulgaris Buitenzorg has been analyzed by some experts for its cellular composition, its ability to produce high quality biomass and the content of essential nutrition. A series of experiments was conducted by culturing Chlorella vulgaris Buitenzorg using Beneck medium in bubbling column photobioreactor. The main variation in this experiment was photoperiodicity, where growth of Chlorella vulgaris Buitenzorg was examined during photoperiodicity condition. The difference between CO2 gas concentration of inlet and outlet of the reactor during operational period, was compared to the same experiment under continuous illumination. Under photoperiodicity of 8 and 9 h/d, the culture cell densities (N were approximately 40 % higher than under continuous illumination. Final biomass density of Chlorella vulgaris Buitenzorg at 9 h/d illumination was 1.43 g/dm3, around 46% higher than under continuous illumination. Specific carbon dioxide transfer rate (qCO2 in photoperiodicity was 50-80% higher than under continuous illumination. These experiments showed that photoperiodicity affects the growth of Chlorella vulgaris Buitenzorg The specific growth rate (μ by photoperiodicity was higher than that by continuous ilumination while the growth period was two times longer. Based on the experiments, it can be concluded that photoperiodicity might save light energy consumption. The prediction of kinetic model under continuous illumination as well as under photoperiodicity illumination showed that Haldane model became the fitted kinetic model.

  2. Eulerian-Lagrangian simulation of a bubbling fluidized bed reactor: Assessment of drag force correlations

    Directory of Open Access Journals (Sweden)

    Ku Xiao-Ke

    2012-01-01

    Full Text Available An Eulerian-Lagrangian approach is developed within the OpenFOAM framework to investigate the effects of three well-known inter-phase drag force correlations on the fluidization behavior in a bubbling fluidized bed reactor. The results show a strong dependency on the restitution coefficient and the friction coefficient and no occurrence of bubbling and slugging for the ideal-collision case. The mean pressure drops predicted by the three models agree quite well with each other.

  3. Quantifying Methane Flux from a Prominent Seafloor Crater with Water Column Imagery Filtering and Bubble Quantification Techniques

    Science.gov (United States)

    Mitchell, G. A.; Gharib, J. J.; Doolittle, D. F.

    2015-12-01

    Methane gas flux from the seafloor to atmosphere is an important variable for global carbon cycle and climate models, yet is poorly constrained. Methodologies used to estimate seafloor gas flux commonly employ a combination of acoustic and optical techniques. These techniques often use hull-mounted multibeam echosounders (MBES) to quickly ensonify large volumes of the water column for acoustic backscatter anomalies indicative of gas bubble plumes. Detection of these water column anomalies with a MBES provides information on the lateral distribution of the plumes, the midwater dimensions of the plumes, and their positions on the seafloor. Seafloor plume locations are targeted for visual investigations using a remotely operated vehicle (ROV) to determine bubble emission rates, venting behaviors, bubble sizes, and ascent velocities. Once these variables are measured in-situ, an extrapolation of gas flux is made over the survey area using the number of remotely-mapped flares. This methodology was applied to a geophysical survey conducted in 2013 over a large seafloor crater that developed in response to an oil well blowout in 1983 offshore Papua New Guinea. The site was investigated by multibeam and sidescan mapping, sub-bottom profiling, 2-D high-resolution multi-channel seismic reflection, and ROV video and coring operations. Numerous water column plumes were detected in the data suggesting vigorously active vents within and near the seafloor crater (Figure 1). This study uses dual-frequency MBES datasets (Reson 7125, 200/400 kHz) and ROV video imagery of the active hydrocarbon seeps to estimate total gas flux from the crater. Plumes of bubbles were extracted from the water column data using threshold filtering techniques. Analysis of video images of the seep emission sites within the crater provided estimates on bubble size, expulsion frequency, and ascent velocity. The average gas flux characteristics made from ROV video observations is extrapolated over the number

  4. Multidimensional two-fluid model numerical simulation of bubbly column flow in a water pool with obstacle

    International Nuclear Information System (INIS)

    Investigation of two-phase flow around obstacles is important for thermal-hydraulic design and safety analyses of various equipments in nuclear power plants. The examples of obstacles are spacers in nuclear fuel rod bundles or in steam generator tube bundles, as well as perforated plates submerged in two-phase mixture in order to equalize void fraction and swell level spatial distribution in large volumes. In this paper the numerical simulation of a bubble column flow in a rectangular water pool is performed. The gas is injected in form of bubbles near the pool bottom through the short perforated pipe. A horizontal plate with a slit is introduced at the half-length of the pool and it forms an obstacle to the bubble column flow. The simulation is performed with the multidimensional transient two-fluid model. The model is based on the mass and momentum balance equations for the liquid and gas phase. The model is numerically solved with the application of the SIMPLE type algorithm developed for the conditions of two-phase flow. Obtained results show the ability of the applied modelling approach to simulate complex liquid and gas flow conditions around obstacles. The bubble column rise along the pool and passing through the plate slit is shown, together with the recirculation of water below and above the horizontal plate. The problem of achieving symmetric velocity and void fraction fields for symmetric rectangular pool geometry and boundary conditions is encountered. The simulations without and with the lateral force are performed, showing the importance of lateral force inclusion in the momentum balance equations. (author)

  5. Modeling and simulation of a pseudo-two-phase gas-liquid column reactor for thermal hydrocracking of petroleum heavy fractions

    OpenAIRE

    E.M. Matos; R. Guirardello

    2002-01-01

    This work presents a model to predict the behavior of velocity, gas holdup and local concentration fields in a pseudo-two-phase gas-liquid column reactor applied for thermal hydrocracking of petroleum heavy fractions. The model is based on the momentum and mass balances for the system, using an Eulerian-Eulerian approach. Using the k-epsilon model,fluid dynamics accounts for both laminar and turbulent flows, with discrete small bubbles (hydrogen) flowing in a continuous pseudohomogeneous liqu...

  6. Mathematical modelling of a continuous biomass torrefaction reactor: TORSPYDTM column

    International Nuclear Information System (INIS)

    Torrefaction is a soft thermal process usually applied to cocoa or coffee beans to obtain the Maillard reaction to produce aromatics and enhance the flavour. In the case of biomass the main interest of torrefaction it is to break the fibers. To do so, Thermya company has developed and patented a biomass torrefaction/depolymerisation process called TORSPYDTM. It is a homogeneous 'soft' thermal process that takes place in an inert atmosphere. The process progressively eliminates the biomass water content transforms a portion of the biomass organic matter and breaks the biomass structure by depolymerisation of the fibers. This produces a high performance solid fuel, called Biocoal, which offers a range of benefits over and above that of normal biomass fuel. To develop such a process, this company has developed two main tools: - a continuous torrefaction laboratory pilot with a capacity to produce 3 - 8 kg/h of torrefied biomass; - a mathematical model dedicated to the design and optimisation of the TORSPYD reactor. The mathematical model is able to describe the chemical and physical processes that take place in the torrefaction column at two different scales, namely: the particle, and the surrounding gas. The model enables the gas temperature profiles inside the column to be predicted, and the results of the model are then validated through experiment in the laboratory pilot. The model also allows us to estimate the thermal power necessary to torrefy any type of biomass for a given moisture content. -- Highlights: → We model a patented torrefaction/depolymerisation biomass process: TORPSPYD. → We compare simulated results to experimental data obtained from our torrefaction pilot plant. → We describe phenomenon that occurs in our torrefaction reactor and discuss about the influence of moisture of the input biomass.

  7. Gas-Liquid flow characterization in bubble columns with various gas-liquid using electrical resistance tomography

    Science.gov (United States)

    Jin, Haibo; Yuhuan, Han; Suohe, Yang

    2009-02-01

    Electrical resistance tomography (ERT) is an advanced and new detecting technique that can measure and monitor the parameters of two-phase flow on line, such as gas-liquid bubble column. It is fit for the industrial process where the conductible medium serves as the disperse phase to present the key bubble flow characteristics in multi-phase medium. Radial variation of the gas holdup and mean holdups are investigated in a 0.160 m i. d. bubble column using ERT with two axial locations (Plane 1 and Plane 2). In all the experiments, air was used as the gas phase, tap water as liquid phase, and a series of experiments were done by adding KCl, ethanol, oil sodium, and glycerol to change liquid conductivity, liquid surface tension and viscosity. The superficial gas velocity was varied from 0.02 to 0.2 m/s. The effect of conductivity, surface tension, viscosity on the mean holdups and radial gas holdup distribution is discussed. The results showed that the gas holdup decrease with the increase of surface tension and increase with the increase of viscosity. Meanwhile, the settings of initial liquid conductivity slightly influence the gas holdup values, and the experimental data increases with the increase of the initial setting values in the same conditions.

  8. Gas-Liquid flow characterization in bubble columns with various gas-liquid using electrical resistance tomography

    International Nuclear Information System (INIS)

    Electrical resistance tomography (ERT) is an advanced and new detecting technique that can measure and monitor the parameters of two-phase flow on line, such as gas-liquid bubble column. It is fit for the industrial process where the conductible medium serves as the disperse phase to present the key bubble flow characteristics in multi-phase medium. Radial variation of the gas holdup and mean holdups are investigated in a 0.160 m i. d. bubble column using ERT with two axial locations (Plane 1 and Plane 2). In all the experiments, air was used as the gas phase, tap water as liquid phase, and a series of experiments were done by adding KCl, ethanol, oil sodium, and glycerol to change liquid conductivity, liquid surface tension and viscosity. The superficial gas velocity was varied from 0.02 to 0.2 m/s. The effect of conductivity, surface tension, viscosity on the mean holdups and radial gas holdup distribution is discussed. The results showed that the gas holdup decrease with the increase of surface tension and increase with the increase of viscosity. Meanwhile, the settings of initial liquid conductivity slightly influence the gas holdup values, and the experimental data increases with the increase of the initial setting values in the same conditions.

  9. Transient simulation of gas bubble in a medium sized lead cooled fast reactor

    International Nuclear Information System (INIS)

    A common problem for many liquid metal cooled fast reactor designs is the positive void worth of the coolant. In this context, an advantage of lead cooled fast reactors is the high temperature of coolant boiling. In contrast to sodium cooled fast reactors this, in practice, precludes coolant boiling. However, partial voiding of the core could result from e.g. gas bubbles entering the core from below. This would introduce a positive reactivity, and if the bubble is large enough. In this paper we model this type of event using a point kinetics code coupled to a heat transport code. The reactivity parameters are obtained from a Monte Carlo code. The 300 MWth reactor design Alfred is used as a test case. We show that in general the reactor design studied is robust in such events, and we conclude that small bubbles a measurable Power oscillation would occur. For very large bubbles there exist a possibility of core damage. The cladding is the most sensitive part. (author)

  10. Investigation of bubble effect in microfluidic fuel cells by a simplified microfluidic reactor

    International Nuclear Information System (INIS)

    This study experimentally examines the influence of two-phase flow on the fluid flow in membraneless microfluidic fuel cells. The gas production rate from such fuel cell is firstly estimated via corresponding electrochemical equations and stoichiometry from the published measured current-voltage curves in the literature to identify the existence of gas bubble. It is observed that O2 bubble is likely to be generated in Hasegawa's experiment when the current density exceeds 30 mA cm-2 and 3 mA cm-2 for volumetric flow rates of 100 μL min-1 and 10 μL min-1, respectively. Besides, CO2 bubble is also likely to be presented in the Jayashree's experiment at a current density above 110 mA cm-2 at their operating volumetric liquid flow rate, 0.3 mL min-1. Secondly, a 1000-μm-width and 50-μm-depth platinum-deposited microfluidic reactor is fabricated and tested to estimate the gas bubble effect on the mixing in the similar microchannel at different volumetric flow rates. Analysis of the mixing along with the flow visualization confirm that the membraneless fuel cell should be free from any bubble, since the mixing index of the two inlet streams with bubble generation is almost five times higher than that without any bubble at the downstream.

  11. Dispersed bubble reactor for enhanced gas-liquid-solids contact and mass transfer

    Energy Technology Data Exchange (ETDEWEB)

    Vimalchand, Pannalal; Liu, Guohai; Peng, WanWang; Bonsu, Alexander

    2016-01-26

    An apparatus to promote gas-liquid contact and facilitate enhanced mass transfer. The dispersed bubble reactor (DBR) operates in the dispersed bubble flow regime to selectively absorb gas phase constituents into the liquid phase. The dispersion is achieved by shearing the large inlet gas bubbles into fine bubbles with circulating liquid and additional pumped liquid solvent when necessary. The DBR is capable of handling precipitates that may form during absorption or fine catalysts that may be necessary to promote liquid phase reactions. The DBR can be configured with multistage counter current flow sections by inserting concentric cylindrical sections into the riser to facilitate annular flow. While the DBR can absorb CO.sub.2 in liquid solvents that may lead to precipitates at high loadings, it is equally capable of handling many different types of chemical processes involving solids (precipitates/catalysts) along with gas and liquid phases.

  12. Experimental investigation of a pilot-scale jet bubbling reactor for wet flue gas desulphurisation

    DEFF Research Database (Denmark)

    Zheng, Yuanjing; Kiil, Søren; Johnsson, Jan Erik

    2003-01-01

    In the present work, an experimental parameter study was conducted in a pilot-scale jet bubbling reactor for wet flue gas desulphurisation (FGD). The pilot plant is downscaled from a limestone-based, gypsum producing full-scale wet FGD plant. Important process parameters, such as slurry pH, inlet...

  13. A Phase-Field Approach to Modeling Hydrate Formation on Methane Gas Bubbles in a Water Column

    Science.gov (United States)

    Fu, X.; Cueto-Felgueroso, L.; Waite, W. F.; Ruppel, C. D.; Juanes, R.

    2014-12-01

    Methane hydrates are water-based crystalline solids, where gas molecules are trapped inside the lattice structure formed by water. Most commonly found in deep ocean floors where low temperature and high pressure are primal conditions for hydrate to form, gas hydrates contain most of the world's mobile carbon and yet it remains an important and open question how methane leakage from gas hydrate impacts ocean and the atmosphere. While current work focus on the breakdown of gas hydrate in marine environment and the the release of methane from seafloor, few studies explore the fate of a single or a plume of methane bubbles when entering the water column after the release. We propose to study the fate of an individual and a series of methane bubbles through mathematical modeling, specifically using a phase-field approach. Phase-field modeling is a mathematical framework that describes systems that are out of thermodynamic equilibrium. First introduced in the context of solidification process and phase transitions, it has since been adopted in the field of multiphase flow. In this work, we present a new phase-field formulation for multiphase/multicomponent flows that allows us to model the fate of methane bubbles in the water system as a nonequilibrium process.

  14. Evaluation of a subsurface oxygenation technique using colloidal gas aphron injections into packed column reactors

    International Nuclear Information System (INIS)

    Bioremediation may be a remedial technology capable of decontaminating subsurface environments. The objective of this research was to evaluate the use of colloidal gas aphron (CGA) injection, which is the injection of micrometer-size air bubbles in an aqueous surfactant solution, as a subsurface oxygenation technique to create optimal growth conditions for aerobic bacteria. Along with this, the capability of CGAs to act as a soil-washing agent and free organic components from a coal tar-contaminated matrix was examined. Injection of CGAs may be useful for remediation of underground coal gasification (UCG) sites. Because of this, bacteria and solid material from a UCG site located in northeastern Wyoming were used in this research. Colloidal gas aphrons were generated and pumped through packed column reactors (PCRS) containing post-burn core materials. For comparison, PCRs containing sand were also studied. Bacteria from this site were tested for their capability to degrade phenol, a major contaminant at the UCG site, and were also used to bioaugment the PCR systems. In this study we examined: (1) the effect of CGA injection on dissolved oxygen concentrations in the PCR effluents, (2) the effect of CGA, H2O2, and phenol injections on bacterial populations, (3) the stability and transport of CGAs over distance, and (4) CGA injection versus H2O2 injection as an oxygenation technique

  15. Effect of Contaminants on Mass Transfer Coefficients in Bubble Column and Airlift Contactors.

    Czech Academy of Sciences Publication Activity Database

    Vasconcelos, J.M.T.; Rodrigues, J.L.M.; Orvalho, Sandra; Alves, S. S.; Mendes, R.L.; Reis, A.

    2003-01-01

    Roč. 58, 8 (2003) , s. 1431-1440. ISSN 0009-2509 Institutional research plan: CEZ:AV0Z4072921 Keywords : mass transfer * bubble * surfactant Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 1.562, year: 2003

  16. Time-series measurements of bubble plume variability and water column methane distribution above Southern Hydrate Ridge, Oregon

    Science.gov (United States)

    Philip, Brendan T.; Denny, Alden R.; Solomon, Evan A.; Kelley, Deborah S.

    2016-03-01

    An estimated 500-2500 gigatons of methane carbon is sequestered in gas hydrate at continental margins and some of these deposits are associated with overlying methane seeps. To constrain the impact that seeps have on methane concentrations in overlying ocean waters and to characterize the bubble plumes that transport methane vertically into the ocean, water samples and time-series acoustic images were collected above Southern Hydrate Ridge (SHR), a well-studied hydrate-bearing seep site ˜90 km west of Newport, Oregon. These data were coregistered with robotic vehicle observations to determine the origin of the seeps, the plume rise heights above the seafloor, and the temporal variability in bubble emissions. Results show that the locations of seep activity and bubble release remained unchanged over the 3 year time-series investigation, however, the magnitude of gas release was highly variable on hourly time scales. Bubble plumes were detected to depths of 320-620 m below sea level (mbsl), in several cases exceeding the upper limit of hydrate stability by ˜190 m. For the first time, sustained gas release was imaged at the Pinnacle site and in-between the Pinnacle and the Summit area of venting, indicating that the subseafloor transport of fluid and gas is not restricted to the Summit at SHR, requiring a revision of fluid-flow models. Dissolved methane concentrations above background levels from 100 to 300 mbsl are consistent with long-term seep gas transport into the upper water column, which may lead to the build-up of seep-derived carbon in regional subsurface waters and to increases in associated biological activity.

  17. Monitoring neutrons from spent reactor fuel by bubble detectors

    CERN Document Server

    Tam, N C; Lakosi, L

    1999-01-01

    In order to eliminate the strong temperature-dependence of bubble detectors used for spent fuel assay, a simple way could be to keep them in the water pond but far from fuel assemblies before exposure for about 20 min, until the detectors warm up. Fast neutrons from fuel assemblies in the Paks Nuclear Power Plant, Hungary, were detected by BD-100R type detectors at 28 deg. C (in winter) and at 35 deg. C in summer). Calibration was performed by a standard sup 2 sup 5 sup 2 Cf source in borated water. Burnup monitoring inside fuel assemblies can be provided by smaller diameter detectors prepared from BD-100R type ones.

  18. Simulation of coalescence, break up and mass transfer in bubble columns by using the Conditional Quadrature Method of Moments in OpenFOAM

    OpenAIRE

    Buffo, Antonio; Marchisio, Daniele,; Vanni, Marco

    2013-01-01

    The evaluation of the mass transfer rates and the fluid-dynamics aspects of bubble columns are strongly affected by the intrinsic poly-dispersity of the gas phase, namely the different dispersed bubbles are usually distributed over a certain range of size and chemical composition values. In our previous work, gas-liquid systems were investigated by coupling Computational Fluid Dynamics with mono-variate population balance models (PBM) solved by using the quadrature method of moments (QMOM). S...

  19. Xe bubbles formation in materials for use in nuclear reactors studied by slow positrons

    International Nuclear Information System (INIS)

    Materials (UO2 and ZrC) for use in nuclear reactors implanted with 800-keV Xe-ions were studied by means of slow positron beam (SPB) spectroscopy. Doppler broadening of annihilation gamma-line technique was used to measure the momentum density distribution (MDD) of annihilating positron electron pairs in two sets of samples implanted at fluences of 1×1016 Xe cm−2. The sensitivity of the MDD shape parameter S to discriminate single Xe atoms and Xe bubbles was discussed. Common trends in Xe bubbles formation as a result of the Xe fluence and/or post-implantation annealing in both materials were described. Positron spectroscopy on SPB was demonstrated to be an excellent complementary technique to secondary ion mass spectroscopy for studying the formation and evolution of Xe-bubbles, and Xe retention. PACS codes: 28.90.+i

  20. A comparative study of two-phase flow models relevant to bubble column dynamics

    Science.gov (United States)

    Minev, P. D.; Lange, U.; Nandakumar, K.

    1999-09-01

    Multiphase flow modelling is still a major challenge in fluid dynamics and, although many different models have been derived, there is no clear evidence of their relevance to certain flow situations. That is particularly valid for bubbly flows, because most of the studies have considered the case of fluidized beds. In the present study we give a general formulation to five existing models and study their relevance to bubbly flows. The results of the linear analysis of those models clearly show that only two of them are applicable to that case. They both show a very similar qualitative linear stability behaviour. In the subsequent asymptotic analysis we derive an equation hierarchy which describes the weakly nonlinear stability of the models. Their qualitative behaviour up to first order with respect to the small parameter is again identical. A permanent-wave solution of the first two equations of the hierarchy is found. It is shown, however, that the permanent-wave (soliton) solution is very unlikely to occur for the most common case of gas bubbles in water. The reason is that the weakly nonlinear equations are unstable due to the low magnitude of the bulk modulus of elasticity. Physically relevant stabilization can eventually be achieved using some available experimental data. Finally, a necessary condition for existence of a fully nonlinear soliton is derived.

  1. Towards the Characterization of the Bubble Presence in Liquid Sodium of Sodium Cooled Fast Reactors

    International Nuclear Information System (INIS)

    In a Sodium cooled Fast Reactors (SFR), different phenomena such as gas entrainment or nucleation can lead to gaseous micro-bubbles presence in the liquid sodium of the primary vessel. Although this free gas presence has no direct impact on the core neutronics, the French Atomic Energy and Alternative Energies Commission (CEA) currently works on its characterization to, among others, check the absence of risk of large gas pocket formation and to assess the induced modifications of the sodium acoustic properties. The main objective is to evaluate the void fraction values (volume fraction of free gas) and the radii histogram of the bubbles present in liquid sodium. Acoustics and electromagnetic techniques are currently developed at CEA: - The low-frequency speed of sound measurement, which allows us to link - thanks to Wood's model - the measured speed of sound to the actual void fraction. - The nonlinear mixing of two frequencies, based on the nonlinear resonance behavior of a bubble. This technique allows knowing the radius histogram associated to a bubble cloud. Two different mixing techniques are presented in this paper: the mixing of two high frequencies and the mixing of a high and a low frequency. - The Eddy-current flowmeter (ECFM), the output signal of which is perturbed by free gas presence and in consequence allows detecting bubbles. For each technique, initial results are presented. Some of them are really promising. So far, acoustic experiments have been led with an air-water experimental set-up. Micro-bubbles clouds are generated with a dissolved air flotation device and monitored by an optical device which provides reference measurements. Generated bubbles have radii range from few micrometers to several tens of micrometers. Present and future air/water experiments are presented. Furthermore, a development plan of in-sodium tests is presented in terms of a device set-up, instrumentation, modeling tools and experiments. (authors)

  2. Bubble Plumes at NW Rota-1 Submarine Volcano, Mariana Arc: Visualization and Analysis of Multibeam Water Column Data

    Science.gov (United States)

    Merle, S. G.; Chadwick, W. W.; Embley, R. W.; Doucet, M.

    2012-12-01

    During a March 2010 expedition to NW Rota-1 submarine volcano in the Mariana arc a new EM122 multibeam sonar system on the R/V Kilo Moana was used to repeatedly image bubble plumes in the water column over the volcano. The EM122 (12 kHz) system collects seafloor bathymetry and backscatter data, as well as acoustic return water column data. Previous expeditions to NW Rota-1 have included seafloor mapping / CTD tow-yo surveys and remotely operated vehicle (ROV) dives in 2004, 2005, 2006 and 2009. Much of the focus has been on the one main eruptive vent, Brimstone, located on the south side of the summit at a depth of ~440m, which has been persistently active during all ROV visits. Extensive degassing of CO2 bubbles have been observed by the ROV during frequent eruptive bursts from the vent. Between expeditions in April 2009 and March 2010 a major eruption and landslide occurred at NW Rota-1. ROV dives in 2010 revealed that after the landslide the eruptive vent had been reorganized from a single site to a line of vents. Brimstone vent was still active, but 4 other new eruptive vents had also emerged in a NW/SE line below the summit extending ~100 m from the westernmost to easternmost vents. During the ROV dives, the eruptive vents were observed to turn on and off from day to day and hour to hour. Throughout the 2010 expedition numerous passes were made over the volcano summit to image the bubble plumes above the eruptive vents in the water column, in order to capture the variability of the plumes over time and to relate them to the eruptive output of the volcano. The mid-water sonar data set totals >95 hours of observations over a 12-day period. Generally, the ship drove repeatedly over the eruptive vents at a range of ship speeds (0.5-4 knots) and headings. In addition, some mid-water data was collected during three ROV dives when the ship was stationary over the vents. We used the FMMidwater software program (part of QPS Fledermaus) to visualize and analyze the data

  3. Velocity distribution of the flow field in the cyclonic zone of cyclone-static micro-bubble flotation column

    Institute of Scientific and Technical Information of China (English)

    Deng Xiao-wei; Liu Jiong-tian; Wang Yong-tian; Cao Yi-jun

    2013-01-01

    Laboratory experiments have been conducted to study the flow field in a cyclone static micro-bubble flotation column.The method of Particle Image Velocimetry (PIV) was used.The flow field velocity distribution in both cross section and longitudinal section within cyclonic zone was studied for different circulating volumes.The cross sectional vortex was also analyzed.The results show that in cross section as the circulating volume increases from 0.187 to 0.350 m3/h,the flow velocity ranges from 0 to 0.68 m/s.The flow field is mainly a non-vortex potential flow that forms a free vortex without outside energy input.In the cyclonic region the vortex deviates from the center of the flotation column because a single tangential opening introduces circulating fluid into the column.The tangential component of the velocity plays a defining role in the cross section.In the longitudinal section the velocity ranges from 0 to 0.08 m/s.The flow velocity increases as does the circulating volume.Advantageous mineral separation conditions arise from the combined effects of cyclonic flow in cross and longitudinal section.

  4. Influence of structured packing on gas holdup in a three-phase bubble column

    DEFF Research Database (Denmark)

    Monsalvo, Matias Alfonso; Böhm, Ursula

    2007-01-01

    . The influence of structured packing on the total gas holdup for different superficial gas velocities was found to be similar with and without suspended solids. Therefore, the results obtained in this work were analysed on the basis of correlations derived earlier for gas-liquid dispersions. Excepting......In this work, the influence of structured packing on gas holdup in gas-liquid-solid dispersions has been studied. The experiments were carried out in an empty column and in column containing structured packing operating under identical conditions. Glass beads and silicon carbide particles were used...

  5. Pilot-scale bubble column photobioreactor culture of a marine dinoflagellate microalga illuminated with light emission diodes.

    Science.gov (United States)

    López-Rosales, L; García-Camacho, F; Sánchez-Mirón, A; Martín Beato, E; Chisti, Yusuf; Molina Grima, E

    2016-09-01

    Production of biomass of the shear-sensitive marine algal dinoflagellate Karlodinium veneficum was successfully scaled-up to 80L using a bubble column photobioreactor. The scale factor exceeded 28,500. Light-emission diodes were used as the light source. The diel irradiance profile mimicked the outdoor profile of natural sunlight. The final cell concentration in the absence of nutrient limitation in the scaled-up photobioreactor was nearly 12×10(5)cellsmL(-1), or the same as in laboratory culture systems. The pH-controlled culture (pH=8.5) was always carbon-sufficient. The culture was mixed pneumatically by using a superficial air velocity of 1.9×10(-3)ms(-1) and the temperature was controlled at 21±1°C. PMID:27318163

  6. Quantitative calculation of reaction performance in sonochemical reactor by bubble dynamics

    Institute of Scientific and Technical Information of China (English)

    徐峥; 安田启司; 刘晓峻

    2015-01-01

    In order to design a sonochemical reactor with high reaction efficiency, it is important to clarify the size and intensity of the sonochemical reaction field. In this study, the reaction field in a sonochemical reactor is estimated from the distribution of pressure above the threshold for cavitation. The quantitation of hydroxide radical in a sonochemical reactor is obtained from the calculation of bubble dynamics and reaction equations. The distribution of the reaction field of the numerical simulation is consistent with that of the sonochemical luminescence. The sound absorption coefficient of liquid in the sonochemical reactor is much larger than that attributed to classical contributions which are heat conduction and shear viscosity. Under the dual irradiation, the reaction field becomes extensive and intensive because the acoustic pressure amplitude is intensified by the interference of two ultrasonic waves.

  7. Experimental investigations of steam bubble entrainment in the down-flow cavity of a natural circulation heat only reactor

    International Nuclear Information System (INIS)

    The ZHM-2 (Zittauer Heizreaktormodell, Zittau Heat Only Reactor Model) experimental facility is described. This facility is used for studying entrainment of gas bubbles during 1800 flow inversion from the up-flow into the down-flow cavity of a natural circulation heat only reactor. Volume gas content, bubble speed, and bubble size can be determined using a special conductivity probe. The gas portion entrained in the down-flow cavity PSI is presented as a function of water level, gas content distribution in the up-flow cavity, and geometry of the upper inverting region. (author)

  8. Voronoi analysis of bubbly flows via ultrafast X-ray tomographic imaging

    Energy Technology Data Exchange (ETDEWEB)

    Lau, Yuk Man; Mueller, Karolin; Azizi, Salar; Schubert, Markus [Helmholtz-Zentrum Dresden-Rossendorf e.V., Institute of Fluid Dynamics, Dresden (Germany)

    2016-03-15

    Although clustering of bubbles plays a significant role in bubble column reactors regarding the heat and mass transfer due to bubble-bubble and flow field interactions, it has yet to be fully understood. Contrary to flows in bubble columns, most literature studies on clustering report numerical and experimental results on dilute or micro-bubbly flows. In this paper, clustering of bubbles in a cylindrical bubble column of 100 mm diameter is experimentally investigated. Ultrafast X-ray tomographic imaging is used to obtain the bubble positions within a hybrid Eulerian framework. By means of Voronoi analysis, the clustering behavior of bubbles is investigated. Experiments are performed with different superficial gas velocities, where Voronoi diagrams are constructed at several column heights. From the PDFs of the Voronoi diagrams, it is shown that the bubble structuring in terms of Voronoi cell volumes develops slower than the bubble size distribution. The latter reaches a steady state earlier with increasing column height. The measured PDFs are compared with the PDF of randomly distributed points, which showed that the amount of bubbles as part of clusters (Voronoi cells < V/ anti V{sub cluster}) as well as bubbles as part of voids (Voronoi cells > V/ anti V{sub void}) increases with the superficial gas velocity. It is found that all experiments have an approximate cluster limit V/ anti V{sub cluster} of 0.63, while the void limit V/ anti V{sub void} varies between 1.5 and 3.0. (orig.)

  9. Simulation of emulsion copolymerization reactions in a continuous pulsed sieve-plate column reactor

    Directory of Open Access Journals (Sweden)

    C. Sayer

    2004-09-01

    Full Text Available This work addressed the viability of using a pulsed sieve-plate column reactor to carry out continuous vinyl acetate/butyl acrylate emulsion copolymerization reactions. A rigorous mathematical model of emulsion copolymerization reactions in a tubular reactor with axial dispersion was used for this purpose. Operational conditions were defined to attain high monomer conversions at the reactor outlet in a relatively short residence time and, at the same time, produce a copolymer with a more homogeneous composition.

  10. Simulation of emulsion copolymerization reactions in a continuous pulsed sieve-plate column reactor

    OpenAIRE

    Sayer C.; Giudici R.

    2004-01-01

    This work addressed the viability of using a pulsed sieve-plate column reactor to carry out continuous vinyl acetate/butyl acrylate emulsion copolymerization reactions. A rigorous mathematical model of emulsion copolymerization reactions in a tubular reactor with axial dispersion was used for this purpose. Operational conditions were defined to attain high monomer conversions at the reactor outlet in a relatively short residence time and, at the same time, produce a copolymer with a more homo...

  11. Steady Thermal Field Simulation of Forced Air-cooled Column-type Air-core Reactor

    Institute of Scientific and Technical Information of China (English)

    DENG Qiu; LI Zhenbiao; YIN Xiaogen; YUAN Zhao

    2013-01-01

    Modeling the steady thermal field of the column-type air-core reactor,and further analyzing its distribution regularity,will help optimizing reactor design as well as improving its quality.The operation mechanism and inner insulation structure of a novel current limiting column-type air-core reactor is introduced in this paper.The finite element model of five encapsulation forced air-cooled column type air-core reactor is constructed using Fluent.Most importantly,this paper present a new method that,the steady thermal field of reactor working under forced air-cooled condition is simulated without arbitrarily defining the convection heat transfer coefficient for the initial condition; The result of the thermal field distribution shows that,the maximum steady temperature rise of forced air-cooled columntype air-core reactor happens approximately 5% to its top.The law of temperature distribution indicates:In the 1/3part of the reactor to its bottom,the temperature will rise rapidly to the increasing of height,yet the gradient rate is gradually decreasing; In the 5 % part of the reactor to its top,the temperature will drop rapidly to the increasing of height; In the part between,the temperature will rise slowly to the increasing of height.The conclusion draws that more thermal withstand capacity should be considered at the 5 % part of the reactor to its top to achieve optimal design solution.

  12. Design of Multi Bubble Sonoluminescence Reactor for Low Frequency Pressure Radiation

    International Nuclear Information System (INIS)

    Sonoluminescence phenomenon has been intensively studied due to its extraordinary capability to produce very high temperature and pressure within micro bubbles exposed by the pressure radiation. In general, it has been widely used for the chemical treatment including dissociation of the toxics and synthesis of functional materials such as nano catalysis. As for the nuclear applications, some of researchers tried to realization of the bubble fusion and change of the decay constant. Unfortunately applications to the nuclear industry are very skeptically accepted in the academic society. In spite of all such skepticism, the studies on sonoluminescence still have the room to be explored. In the present study, we investigated the relation among the reactor size, power and frequency of the pressure radiation. Main motivation of the present study came from some mismatch in the degradation rate of TCE in the multibubble sonoluminescence reactors (MBSL reactor) between Lee et al (2011) and Oh and Lee (2010). Both studies utilized horn type ultrasound source with the frequency of 20 kHz. However, the shape and volume of the reactors were different form each other. In the present study, we simply measured the light emission from the luminol solution in the reactors to evaluate the effectiveness of the MBSL. As noted in the study of Lee et al, the hot spot of MBSL dissociate water molecules into OH radicals which dissociate luminol in the solution to emit radiation. Therefore, the intensity and distribution of the radiation of luminol dissociation in the reactor are key index of the population of hot spots. Results and discussions are made by comparing the light emission intensity with different operating powers

  13. Modeling of reaction kinetics in bubbling fluidized bed biomass gasification reactor

    Energy Technology Data Exchange (ETDEWEB)

    Thapa, R.K.; Halvorsen, B.M. [Telemark University College, Kjolnes ring 56, P.O. Box 203, 3901 Porsgrunn (Norway); Pfeifer, C. [University of Natural Resources and Life Sciences, Vienna (Austria)

    2013-07-01

    Bubbling fluidized beds are widely used as biomass gasification reactors as at the biomass gasification plant in Gussing, Austria. The reactor in the plant is a dual circulating bubbling fluidized bed gasification reactor. The plant produces 2MW electricity and 4.5MW heat from the gasification of biomass. Wood chips as biomass and olivine particles as hot bed materials are fluidized with high temperature steam in the reactor. As a result, biomass undergoes endothermic chemical reaction to produce a mixture of combustible gases in addition to some carbon-dioxide (CO2). The combustible gases are mainly hydrogen (H2), carbon monoxide (CO) and methane (CH4). The gas is used to produce electricity and heat via utilization in a gas engine. Alternatively, the gas is further processed for gaseous or liquid fuels, but still on the process of development level. Composition and quality of the gas determine the efficiency of the reactor. A computational model has been developed for the study of reaction kinetics in the gasification rector. The simulation is performed using commercial software Barracuda virtual reactor, VR15. Eulerian-Lagrangian approach in coupling of gas-solid flow has been implemented. Fluid phase is treated with an Eulerian formulation. Discrete phase is treated with a Lagrangian formulation. Particle-particle and particle-wall interactions and inter-phase heat and mass transfer have been taken into account. Series of simulations have been performed to study model prediction of the gas composition. The composition is compared with data from the gasifier at the CHP plant in Güssing, Austria. The model prediction of the composition of gases has good agreements with the result of the operating plant.

  14. Hydrodynamics and mass transfer in bubble column: Influence of liquid phase surface tension

    OpenAIRE

    Chaumat, Hélène; Billet, Anne-Marie; Delmas, Henri

    2007-01-01

    According to literature, few experiments are performed in organic solvents which are mostly used in commercial gas–liquid reactors. However, it is commonly accepted that data obtained in aqueous solution allow to predict the surface tension effects, and to model the behaviour of organic solvents. In this work, we examine the validity of this approximation. In this objective, the flows observed in two pure media having similar viscosity but different surface tension—respectively, water (ref...

  15. Simulation of a steam bubble transport in the primary system of the pool type lead cooled fast reactors

    International Nuclear Information System (INIS)

    Pool-type design makes Lead cooled Fast Reactor (LFR) economically competitive with other advanced reactor designs considered under the Generation IV framework. However, close proximity of steam generator to the core increases the risks associated with Steam Generator Tube Rupture/Leakage (SGTR/SGTL) such as voiding of the core and resulting reactivity insertion and/or local damage (burnout) of fuel rod cladding. Analysis of consequences of SGTL provided in present paper suggests that small bubbles of steam can be dragged by the turbulent coolant flow into the core region. Trajectories of the bubbles are determined by location of the leak, bubbles size and turbulent flow field of lead coolant. The influence of epistemic uncertainty in drag coefficient on prediction of the fraction of bubbles that can reach the core and accumulate in the primary coolant system is discussed in the paper. (author)

  16. Thermal neutron flux distribution in ET-RR-2 reactor thermal column

    Directory of Open Access Journals (Sweden)

    Imam Mahmoud M.

    2002-01-01

    Full Text Available The thermal column in the ET-RR-2 reactor is intended to promote a thermal neutron field of high intensity and purity to be used for following tasks: (a to provide a thermal neutron flux in the neutron transmutation silicon doping, (b to provide a thermal flux in the neutron activation analysis position, and (c to provide a thermal neutron flux of high intensity to the head of one of the beam tubes leading to the room specified for boron thermal neutron capture therapy. It was, therefore, necessary to determine the thermal neutron flux at above mentioned positions. In the present work, the neutron flux in the ET-RR-2 reactor system was calculated by applying the three dimensional diffusion depletion code TRITON. According to these calculations, the reactor system is composed of the core, surrounding external irradiation grid, beryllium block, thermal column and the water reflector in the reactor tank next to the tank wall. As a result of these calculations, the thermal neutron fluxes within the thermal column and at irradiation positions within the thermal column were obtained. Apart from this, the burn up results for the start up core calculated according to the TRITION code were compared with those given by the reactor designer.

  17. A new post-column reactor-laser induced fluorescence detector for capillary electrophoresis

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Liling

    1996-01-02

    Capillary zone electrophoresis (CZE), a powerful separation method based on the differential migration of charged species under the influence of an electric field, has been widely used for separations covering from small ions to big biomolecules. Chapter 1 describes the method, then discusses detection of the separated analytes by laser induced fluorescence and by chemical derivatization, and the use of O-phthaldialdehyde (OPA) as a post-column reagent. Chapter 2 describes a post-column reactor which uses two narrow bore capillaries connected coaxially. This reactor differs from other coaxial reactors in terms of capillary dimensions, reagent flow control, ease of construction and most importantly, better limits of detection. The derivatization reagent is electroosmotically driven into the reaction capillary and the reagent flow rate is independently controlled by a high voltage power supply. Amino acids, amines and proteins, derivatized by OPA/2-mercaptoethanol using this post-column reactor coupled with LIF detection, show low attomole mass limits of detection, and for the first time, the authors demonstrate single cell capability with a post-column derivatization scheme. The single cell capability shows that this reactor could find applications in assaying non-fluorescent or electrochemically inactive components in individual biological cells in the future.

  18. Gas Hold-Up, Mixing Time and Circulation Time in Internal Loop Airlift Bubble Column

    Directory of Open Access Journals (Sweden)

    Ali Abdul Rahman–Al Ezzi

    2014-01-01

    Full Text Available The effects of superficial gas in the riser (Vgr and liquid phase properties on the gas hold-up(ɛg , mixing time (Tm and circulation time (TC were studied in 8 liter internal air lift loop reactor (down comer-to-riser crosssectional area ratio = 0.249. Air was used as a gas phase. Water and four aqueous solutions of 10% concentration methanol, ethanol, (were used to simulate the behavior of non-coalescing organic liquids 50% glycerol and 2% Carboxy Methyl Cellulose (CMC were used to simulate the behavior of coalescing viscous liquids. Polyethylene-non-porous-solid particles with a concentration of (50 Kg/m3 were used as solid phase. Superficial gas velocity varied from 0.01 m/s to 0.1 m/s and air dispersed into the center of the draught tube by using a porous gas distributor. The results showed that (εg increased with increasing gas velocity and coalescence inhibition of liquid, while Tm and Tc decrease with increasing gas velocity. It was found that increasing liquid viscosity and coalescence reduces (εg but increases (Tm and (Tc. The gas holdup was correlated with dimensionless groups and independent parameter with correlation coefficient is 0.967, the following correlation is obtained.

  19. Treatment of Copper Contaminated Municipal Wastewater by Using UASB Reactor and Sand-Chemically Carbonized Rubber Wood Sawdust Column

    OpenAIRE

    Swarup Biswas; Umesh Mishra

    2016-01-01

    The performance of a laboratory scale upflow anaerobic sludge blanket (UASB) reactor and its posttreatment unit of sand-chemically carbonized rubber wood sawdust (CCRWSD) column system for the treatment of a metal contaminated municipal wastewater was investigated. Copper ion contaminated municipal wastewater was introduced to a laboratory scale UASB reactor and the effluent from UASB reactor was then followed by treatment with sand-CCRWSD column system. The laboratory scale UASB reactor and ...

  20. Modifications of the Cornell University TRIGA reactor thermal column

    International Nuclear Information System (INIS)

    Full text: The thermal column has been modified to provide a horizontal beam suitable for neutron radiography. A hole of circular cross-section was cut along the axis of the thermal column through graphite and lead from the outer surface of the 'sliding block' to a point about 10 cm short of the curved end of the thermal column. The section through the sliding block is 15.2 cm in diameter and the remaining section is 10.2 cm in diameter. The outer or 15.2-cm section is lined with a 6-mm thick Boral sleeve, and the inner or 10.2-cm section contains a tapered collimator of Pd-Cd alloy inside a 3-mm thick Boral sleeve, a defining aperture formed by a 2.5-cm diameter hole in a 6-mm Boral plate, and, at the core end, a 5.1-cm thick bismuth absorber disk. All of these components are enclosed in an aluminum housing. From the sliding block outwards - a distance of 122 cm across the hohlraum and through the graphite at the exit end, plus another 122 cm through the rolling door - no drilling was necessary since removable plugs could be taken out to form a tapered hole of square cross section with stepped widths of 30.5, 33.0, and 38.1 cm. An aluminum housing fitting snugly in this hole is lined with Boral or a gadolinium-bearing paint and is joined with a rubber gasket to the inner housing, so that the entire length can be purged with helium. This system provides an l/d ratio of 1/140 and a useful beam area at the exposure point of 38 cm x 38 cm. At 480 kW, the neutron flux there is 106 n/cm2 sec and the gamma flux is 17 R/hr. Figure 2 is a reproduction of the first radiograph taken with the facility. (author)

  1. Impact of structured packing on bubble column mass transfer characteristics evaluation: Študija vpliva struktuiranega polnila na transportne lastnosti v koloni z mehurčki:

    OpenAIRE

    Lakota, Ana

    2003-01-01

    Based on the available concentration profiles the present work discusses the sensitivity of volumetric mass transfer coefficient on axial dispersion coefficient. The calculations were performed for a bubble column without internals, the parameters of ADM were determined with nonlinear regression. The volumetric mass transfer coefficient shows a slight dependence on the axial dispersion coefficient which leads to the conclusion that ADM provides reasonable values for kLa whenever more or less ...

  2. Conceptual design of epithermal neutron beam for BNCT in the thermalizing column of TRIGA reactor

    International Nuclear Information System (INIS)

    The Monte Carlo feasibility study of development of the epithermal neutron beam for BNCT clinical trials in thermalising column (TC) of TRIGA reactor is presented. The investigation of the possible use of fission converter as well as the set-up of TRIGA reactor core is performed. The optimization of the irradiation facility components is carried out and the configuration with the most favorable cost/performance ratio is proposed. The results prove, that a BNCT irradiation facility with performances, comparable to existing beams throughout the world, could be installed in TC/DC of the TRIGA reactor, quite suitable for the clinical treatments of human patients.(author)

  3. A computational fluid dynamics study of hydrogen bubbles in an electrochemical reactor

    Directory of Open Access Journals (Sweden)

    Renata da Silva Cavalcanti

    2005-06-01

    Full Text Available Most electrochemical reactors present reactions with the growth and departure of gas bubbles which influence on the reactor hydrodynamics and this study is usually complex, representing a vast field for research. The present paper had as objective to study a bi-phase (gas-liquid system aiming to foresee the influence of departure of hydrogen bubbles generated on effective electrode surface situated on cathodic semi-cell. Nevertheless, it was idealized that the gas was injected into the semi cell, through the effective electrode surface With this hypothesis, it was possible to study, and numerically analyze, the hydrodynamic behavior of the hydrogen bubbles in the interior of the study domain, applying concepts of computational fluid dynamics by using the computational applicative CFX-4 for the application of the MUSIG ("MUltiple-SIze-Group" model, taking into consideration the phenomena of coalescence and the distribution of the diameter of the bubbles.A maioria dos reatores eletroquímicos apresenta reações com crescimento e desprendimento de bolhas de gás influenciando na hidrodinâmica dos reatores e seu estudo é, geralmente, complexo representando um campo amplo para pesquisas. O presente artigo teve por objetivo estudar um sistema bifásico (gás-líquido visando prever a influência do desprendimento das bolhas de hidrogênio geradas na superfície específica do eletrodo localizada na semicélula catódica. No entanto, foi idealizado que o gás fora injetado no interior da semicélula através da superfície específica do eletrodo. Com esta hipótese, foi possível estudar e analisar numericamente o comportamento hidrodinâmico das bolhas de hidrogênio no interior do domínio de estudo, aplicando-se os conceitos de fluidodinâmica computacional usando o aplicativo computacional CFX-4 para aplicação do modelo MUSIG ("Multiple-size-group" levando em consideração os fenômenos da coalescência e da distribuição do diâmetro das

  4. A computational model for dissolved gas and bubble behavior in the primary coolant system of sodium-cooled fast reactor

    International Nuclear Information System (INIS)

    Full text of publication follows: A computational code has been developed for inert gas behavior in the primary system of sodium cooled fast reactor (SFR). The inert gas exists in the circulating coolant sodium as resolved gas or free gas bubbles. The primary coolant system of the SFR has free surfaces which are covered by argon gas. The cover gas system is slightly pressurized above the atmospheric pressure. Therefore, the argon cover gas would dissolve in the liquid sodium and dispersed in the primary coolant system by diffusion and convection. In addition, helium gas is generated in the control rods of the reactor core and is emitted as small bubbles from the B4C pellet. Another source of gas bubbles is gas entrainment at the free surface of the reactor vessel if the sodium flow velocity at the free surface is large enough. From the viewpoint of design and safety of the SFR, the gas in the primary system may cause disturbance in reactivity, nucleation site for boiling and cavitation, flow instability, and/or influence on heat transfer. In the present method, the concentration distribution of the dissolved gas and free gas bubble are evaluated for steady state and transient conditions according to the mass and heat transfer in the cooling system. The bubble diameter is assumed to follow the lognormal distribution and discretized into numbers of representative diameters. Physical modeling of the gas behavior is described in the following. In the intermediate heat exchanger, nucleation of bubbles caused by the temperature decrease is evaluated at the heat transfer tube surface. The bubbles on the tube surface are detached from the wall according to the balance of drag, surface tension and buoyancy forces. At the gas liquid interface (free surface and bubble surface), evaporation, dissolution and diffusion are calculated. Bubbles traveling the primary system would break up at turbulent region such as core fuel assembly and mechanical coolant pump. At the free

  5. Experimental verification of fast reactor safety analysis code SIMMER-III for transient bubble behavior with condensation

    International Nuclear Information System (INIS)

    Experimental verification of a reactor safety analysis code, SIMMER-III, was performed for transient behaviors of large-scale bubbles with condensation. The objective of the present study is to verify the code for numerical simulations of relatively short-time-scale multi-phase, multi-component hydraulic problems, among which vaporization and condensation, or simultaneous heat and mass transfer, play an important role. In this study, a series of transient bubble behavior experiments, which are dedicated to condensation phenomena with noncondensable gases, was performed. In the experiments, pressurized mixture of noncondensable gas and steam was discharged as a large-scale single bubble into a cylindrical pool filled with stagnant subcooled water. Concentration of noncondensable gas was taken as an experimental parameter as well as species of noncondensable gas. The characteristics of transient behavior of large-scale bubbles with condensation observed in the experiments were estimated through experimental analyses using SIMMER-III. In the experiments with steam condensation, dispersion of the gas mixture discharged into the liquid pool was accompanied by the vapor condensation at the bubble surface. SIMMER-III simulations suggest that the noncondensable gas has less inhibiting effect on condensation of large-scale bubbles. This is a characteristic different from quasi-steady condensation of small-scale bubbles observed in our previous experiments. (author)

  6. Advanced pebble bed high temperature reactor with central graphite column for future applications

    International Nuclear Information System (INIS)

    Design evaluations of the advanced pebble bed high temperature reactor, AHTR, with central graphite column are given. This reactor, as a nuclear heat source, is suitable for coal refinement as well as for electricity generation with closed gas turbine primary helium circuit. With this design of the central graphite column, it is possible to limit the core temperatures under the required value of about 1600deg C in case of accident conditions, even with higher thermal power and higher core inlet and outlet temperatures. The designs of core internals are described. The after heat removal system is integrated in the prestressed concrete reactor pressure vessel, which is based on the principals of natural convection. Research work is being carried out, whereby the sphencal fuel elements are coated with a layer of silicon carbide, to improve the corrosion resistance as well as the effectiveness of the fission products barrier. (orig.)

  7. A CFD approach on the effect of particle size on char entrainment in bubbling fluidised bed reactors

    International Nuclear Information System (INIS)

    The fluid - particle interaction inside a 41.7 mg s-1 fluidised bed reactor is modelled. Three char particles of sizes 500 μm, 250 μm, and 100 μm are injected into the fluidised bed and the momentum transport from the fluidising gas and fluidised sand is modelled. Due to the fluidising conditions and reactor design the char particles will either be entrained from the reactor or remain inside the bubbling bed. The particle size is the factor that differentiates the particle motion inside the reactor and their efficient entrainment out of it. A 3-Dimensional simulation has been performed with a completele revised momentum transport model for bubble three-phase flow according to the literature as an extension to the commercial finite volume code FLUENT 6.2.

  8. Design concept of a cryogenic distillation column cascade for a ITER scale fusion reactor

    International Nuclear Information System (INIS)

    A column cascade has been proposed for the fuel cycle of a ITER scale fusion reactor. The proposed cascade consists of three columns and has significant features: either top or bottom product is prior to the other for each column: it is avoided to withdraw side streams as products or feeds of down stream columns: and there is no recycle steam between the columns. In addition, the product purity of the cascade can be maintained against the changes of flow rates and compositions of feed streams just by adjusting the top and bottom flow rates. The control system has been designed for each column in the cascade. A key component in the prior product stream was selected, and the analysis method of this key component was proposed. The designed control system never brings instability as long as the concentration of the key component is measured with negligible time lag. The time lag for the measurement considerably affects the stability of the control system. A significant conclusion by the simulation in this work is that permissible time for the measurement is about 0.5 hour to obtain stable control. Hence, the analysis system using the gas chromatography is valid for control of the columns. (author)

  9. Treatment of arsenic contaminated water in a laboratory scale up-flow bio-column reactor

    International Nuclear Information System (INIS)

    The present paper describes the observations on the treatment of arsenic contaminated synthetic industrial effluent in a bio-column reactor. Ralstonia eutropha MTCC 2487 has been immobilized on the granular activated carbon (GAC) bed in the column reactor. The synthetic water sample containing As(T) (As(III):As(V) = 1:1), Fe, Mn, Cu and Zn at the initial concentrations of 25, 10, 2, 5, 10 ppm, respectively, was used. Concentrations of all the elements have been found to be reduced below their permissible limits in the treated water. The significant effect of empty bed contact time (EBCT) and bed height on the arsenic removal was observed in the initial stage. However, after some time of operation (approximately 3-4 days) no such effect was observed. Removal of As(III) and As(V) was almost similar after ∼2 days of operation. However, at the initial stage As(V) removal was slightly more than that of As(III). In absence of washing, after ∼4-5 days of operation, the bio-column reactor was observed to act as a GAC column reactor based on physico-chemical adsorption. Like arsenic, the percent removals of Fe, Mn, Cu and Zn also attained minimum after ∼1 day and increased significantly to the optimum value within 3-4 days of operation. Dissolved oxygen (DO) has been found to decrease along with the increasing bed height from the bottom. The pH of the solution in the reactor has increased slightly and oxidation-reduction potential (ORP) has decreased with the time of operation

  10. Effects of Pipe Bundles on the Sparger Zone Development in Bubble Columns%列管束内构件对鼓泡塔流动发展的影响

    Institute of Scientific and Technical Information of China (English)

    赵远方; 李兆奇; 管小平; 王丽军; 成有为; 李希

    2015-01-01

    在Φ500 mm×4000 mm的大型冷模实验装置内考察了列管束内构件对鼓泡塔流动发展的影响。以空气-水为工作体系,分别采用电导探针和Pavlov管测量了有、无列管的鼓泡塔内不同轴向高度的气含率和液体流速径向分布。实验表明,在安装密集列管束的鼓泡塔内也存在一个充分发展段。与空塔不同的是,列管束的存在使分布器影响区显著延长,从空塔的约两倍塔径高度增至约四倍塔径高度,在冷模装置中占据塔体积的50%以上。在实验条件下,鼓泡塔高径比或液位高度对分布器影响区大小没有明显影响。%Bubble column reactors with pipe bundle heat exchangers are of importance in industrial application. Study on the effect of pipe bundles on flow development was conducted in a bubble column of 0.5 m diameter with 40 vertical pipes. Radial distributions of gas hold-up and liquid velocity at different heights were measured with conductivity probe and Pavlov tube respectively. Results show that a fully developed zone is existed in the column with pipe bundles. Comparing with the column without pipes, the size of the sparger zone is remarkably extended from 2 diameter height to 4 diameter height, which accounts for more than 50% of the column volume. The liquid level height has no significant impact on the existence and development of the sparger zone.

  11. Modeling and simulation of a pseudo-two-phase gas-liquid column reactor for thermal hydrocracking of petroleum heavy fractions

    Directory of Open Access Journals (Sweden)

    E.M. Matos

    2002-07-01

    Full Text Available This work presents a model to predict the behavior of velocity, gas holdup and local concentration fields in a pseudo-two-phase gas-liquid column reactor applied for thermal hydrocracking of petroleum heavy fractions. The model is based on the momentum and mass balances for the system, using an Eulerian-Eulerian approach. Using the k-epsilon model,fluid dynamics accounts for both laminar and turbulent flows, with discrete small bubbles (hydrogen flowing in a continuous pseudohomogeneous liquid phase (oil and catalyst particles. The petroleum is assumed to be a mixture of pseudocomponents, grouped by similar chemical structural properties, and the thermal hydrocracking is taken into account using a kinetic network based on these pseudocomponents.

  12. Three-phase gas-liquid-solid foaming bubble reactors and self-lubricated transport of bitumen froth

    Science.gov (United States)

    Mata, Clara E.

    Two distinct topics in multi-phase flow of interest of the oil industry are considered in this thesis. Studies of three-phase gas-liquid-solid foaming bubble reactors and self-lubricated transport of bitumen froth are reported. Applications of foams and foaming are found in many industrial processes such as flotation of minerals, enhanced oil recovery, drilling in oil reservoirs, and refining processes. However the physics of foaming and defoaming are not fully understood. Foams trap gas and are not desirable in some processes such as oil refining. Previously, it has been found that foaming may be strongly suppressed in a cold slit bubble reactor by fluidizing hydrophilic particles in the bubbly mixture below the foam. In this work, we fluidized hydrophobic and hydrophilic versions of two different sands in a cold slit foaming bubble reactor. We found that the hydrophobic sands suppress the foam substantially better than their hydrophilic counterparts. To study the capacity of foams to carry particles, we built a new slit foaming bubble reactor, which can be continuously fed with solid particles. Global gas, liquid, and solid holdups were measured for given gas and liquid velocities and solid flow rates. This research provides the fundamental ground work for the identification of flow types in a slit three-phase foaming bubble reactor with continuous injection of particles. Bitumen froth is produced from the oil sands of Athabasca, Canada. When transported in a pipeline, water present in the froth is released in regions of high shear (at the pipe wall). This results in a lubricating layer of water that allows bitumen froth pumping at greatly reduced pressures and hence the potential for savings in pumping energy consumption. Experimental results establishing the features of this self lubrication phenomenon are presented. The pressure gradient of lubricated flows closely follow the empirical law of Blasius for turbulent pipe flow with a constant of proportionality

  13. Safety Evaluation for Packaging for onsite Transfer of plutonium recycle test reactor ion exchange columns

    International Nuclear Information System (INIS)

    The purpose of this Safety Evaluation for Packaging (SEP) is to authorize the use of three U.S. Department of Transportation (DOT) 7A, Type A metal boxes (Capital Industries Part No. S 0600-0600-1080- 0104) to package 12 Plutonium Recycle Test Reactor (PRTR) ion exchange columns as low-level waste (LLW). The packages will be transferred from the 309 Building in the 300 Area to low level waste burial in the 200 West Area. Revision 1 of WHC-SD-TP-SEP-035 (per ECN No. 621467) documents that the boxes containing ion exchange columns and grout will maintain the payload under normal conditions of transport if transferred without the box lids

  14. Contribution of nonlinear acoustic to the characterization of micro-bubbles clouds in liquid sodium. Application to the generation IV nuclear reactors

    International Nuclear Information System (INIS)

    The SFR system chosen (Sodium Fast Reactor: fast neutron reactors cooled by liquid sodium) by France led to a fourth-generation prototype named ASTRID. The development of this kind of reactors presents several challenges, particularly in terms of improving the safety and monitoring operation. This involves, among other things, characterization of the bubbles presence in liquid sodium. The characterization of the bubbles presence is the subject of this thesis. It involves the determination of void fraction (gas volume fraction) and histogram of the radii of bubbles. The bibliographic work done has shown that linear acoustic techniques for the characterization of bubble clouds are inadequate to achieve this. However promising leads have been identified by studying nonlinear acoustic techniques. This last idea has therefore been explored. An experimental water bench for the generation and optical control of micro-bubbles cloud allowed us to validate finely the reconstruction of histograms of radii through a technique of nonlinear mixing of a high frequency with a low frequency. The potential of the mixing of two high frequencies, more interesting for the industrial point of view has also been demonstrated. Finally, the bases of the transposition of an original technique of nonlinear resonance spectroscopy applied to a bubbles cloud were explored through the introduction of acoustic resonators. The results offer many interesting opportunities, both in terms of industrial applications and for more fundamental understanding of non-linear behavior of a bubble excited by multiple frequencies and of bubbles clouds excited at low frequency. (author)

  15. Thermal neutron flux distribution in ET-RR-2 reactor thermal column

    OpenAIRE

    Imam Mahmoud M.; Roushdy Hassan

    2002-01-01

    The thermal column in the ET-RR-2 reactor is intended to promote a thermal neutron field of high intensity and purity to be used for following tasks: (a) to provide a thermal neutron flux in the neutron transmutation silicon doping, (b) to provide a thermal flux in the neutron activation analysis position, and (c) to provide a thermal neutron flux of high intensity to the head of one of the beam tubes leading to the room specified for boron thermal neutron capture therapy. It was, therefore, ...

  16. Design of gamma radiation equipment for studying a bubbling gas fluidized bed. Determination of a radial void fraction profile and bubble velocities in a 0.40 m column

    International Nuclear Information System (INIS)

    In this work the possibility of the use of gamma radiation in investigating bubbles in a large three dimensional gas-fluidised bed was examined. A measuring system was designed based upon the absorption of gamma radiation. As high energy (>100 keV) gamma radiation penetrates deeply into matter, it can be used to scan through a gas-solid fluidised bed. The attenuation of a beam of mono-energetic photons is related to the amount of solid particles in the path of the beam. With the gamma absorption technique two parameters can be determined: The void fraction and the bubble velocity. With one narrow beam of gamma radiation a chordal void fraction can be measured in the homogeneous part of the bed. An optimalisation procedure for the void fraction determination led to the choice of Cs-137 as radiation source. This optimalisation procedure concerned minimizing of the standard deviation in the determined chordal void fraction as a function of the energy of gamma radiation. With two narrow parallel beams placed at a distance of 12 cm above each other a bubble velocity can be obtained. A cross-correlation between the two detector responses gives the time shift between the two responses. The system was designed for velocity measurements in the non-homogeneous part of the column. A simulation of the two beam measurement method for an air fluidized bed, 0.40 m in diameter, of polystyrene particles led to the choice of 100 mCi for the source strength for each of the two Cs-137 sources. For a 100 mCi Cs-137 source a shielding of 8 cm of lead is necessary to comply with safety regulations, concerning the use of radioactive materials. A source holder was designed, containing two encapsulated 100 mCi Cs-137 sources, in accordance with the regulations in the licence of the Delft University of Technology for the use of encapsulated sources. (orig.)

  17. Oxidative pyrolysis of kraft lignin in a bubbling fluidized bed reactor with air

    International Nuclear Information System (INIS)

    Fast pyrolysis of kraft lignin with partial (air) oxidation was studied in a bubbling fluidized bed reactor at reaction temperatures of 773 and 823 K. The bio-oil vapors were fractionated using a series of three condensers maintained at desired temperatures, providing a dry bio-oil with less than 1% water and over 96% of the total bio-oil energy. Oxygen feed was varied to study its effect on yield, composition, and energy recovery in the gas, char and oil products. The addition of oxygen to the pyrolysis process increased the production of gases such as CO and CO2. It also changed the dry bio-oil properties, reducing its heating value, increasing its oxygen content, reducing its average molecular weight and tar concentration, while increasing its phenolics concentration. The lower reaction temperature of 773 K was preferred for both dry bio-oil yield and quality. Autothermal operation of the pyrolysis process was achieved with an oxygen feed of 72 or 54 g per kg of biomass at the reaction temperatures of 773 and 823 K, respectively. Autothermal operation reduced both yield and total energy content of the dry bio-oil, with relative reductions of 24 and 20% for the yield, 28 and 23% for the energy content, at 773 and 823 K. - Highlights: • Autothermal pyrolysis of Kraft lignin is possible with introduction of air. • Under autothermal conditions, 24% of the dry bio-oil chemicals are lost at 773 K. • Partial oxidation helps produce more simple phenols and less pyrolytic lignin. • Bio-oil from lignin pyrolysis has a very high phenolics concentration

  18. Decaffeination process characteristic of Robusta coffee in single column reactor using ethyl acetate solvent

    Directory of Open Access Journals (Sweden)

    Sukrisno Widyotomo

    2009-08-01

    Full Text Available Consumers drink coffee not as nutrition source, but as refreshment drink. For coffee consumers who have high tolerance for caffeine, coffee may warm up and refresh their bodies. High caffeine content in coffee beans may cause several complaints to consumers who are susceptible to caffeine. One of the efforts, for coffee market expansion is product diversification to decaffeinated coffee. Decaffeination process is one of process to reduce caffeine content from agricultural products. Indonesian Coffee and Cocoa Research Institute in collaboration with Bogor Agricultural University has developed a single column reactor for coffee beans decaffeination. The aim of this research is to study process characteristic of coffee decaffeination in single column reactor using ethyl acetate (C4H8O2 solvent. Treatments applicated in the research were time and temperature process. Temperature treatment were 50—60OC, 60—70OC, 70—80OC, 80—90OC and 90—100OC. Time treatment were 2 h, 4 h, 6 h, 8 h, 10 h, and 12 h Size of Robusta coffee beans used were less than 5.5 mm (A4, between 5.5 mm and 6.5 mm (A3, between 6.5 mm and 7.5 mm (A2, and more than 7.5 mm (A1. The result showed that decaffeination process with ethyl acetate solvent will be faster when its temperature was higher and smaller bean size. For bean size less than 5,5 mm, decaffeination process by 10% ethyl acetat can be done 8—10 hours in 90—100OC solvent temperature or 12 hours in 60—70OC solvent temperature for 0.3% caffein content. Organoleptic test showed that 90—100OC temperature solvent treatment decreased coffee flavor, which aroma, bitterness and body values were 1.9 each . Key words : Coffee, caffeine, decaffeination, quality, single column.

  19. Demonstration of two-phase Direct Numerical Simulation (DNS) methods potentiality to give information to averaged models: application to bubbles column

    International Nuclear Information System (INIS)

    This work is a part of a long term project that aims at using two-phase Direct Numerical Simulation (DNS) in order to give information to averaged models. For now, it is limited to isothermal bubbly flows with no phase change. It could be subdivided in two parts: Firstly, theoretical developments are made in order to build an equivalent of Large Eddy Simulation (LES) for two phase flows called Interfaces and Sub-grid Scales (ISS). After the implementation of the ISS model in our code called TrioU, a set of various cases is used to validate this model. Then, special test are made in order to optimize the model for our particular bubbly flows. Thus we showed the capacity of the ISS model to produce a cheap pertinent solution. Secondly, we use the ISS model to perform simulations of bubbly flows in column. Results of these simulations are averaged to obtain quantities that appear in mass, momentum and interfacial area density balances. Thus, we processed to an a priori test of a complete one dimensional averaged model.We showed that this model predicts well the simplest flows (laminar and monodisperse). Moreover, the hypothesis of one pressure, which is often made in averaged model like CATHARE, NEPTUNE and RELAP5, is satisfied in such flows. At the opposite, without a polydisperse model, the drag is over-predicted and the uncorrelated Ai flux needs a closure law. Finally, we showed that in turbulent flows, fluctuations of velocity and pressure in the liquid phase are not represented by the tested averaged model. (author)

  20. A Laboratory Experiment To Measure Henry's Law Constants of Volatile Organic Compounds with a Bubble Column and a Gas Chromatography Flame Ionization Detector (GC-FID)

    Science.gov (United States)

    Lee, Shan-Hu; Mukherjee, Souptik; Brewer, Brittany; Ryan, Raphael; Yu, Huan; Gangoda, Mahinda

    2013-01-01

    An undergraduate laboratory experiment is described to measure Henry's law constants of organic compounds using a bubble column and gas chromatography flame ionization detector (GC-FID). This experiment is designed for upper-division undergraduate laboratory courses and can be implemented in conjunction with physical chemistry, analytical…

  1. Numerical simulation of the nonlinear ultrasonic pressure wave propagation in a cavitating bubbly liquid inside a sonochemical reactor.

    Science.gov (United States)

    Dogan, Hakan; Popov, Viktor

    2016-05-01

    We investigate the acoustic wave propagation in bubbly liquid inside a pilot sonochemical reactor which aims to produce antibacterial medical textile fabrics by coating the textile with ZnO or CuO nanoparticles. Computational models on acoustic propagation are developed in order to aid the design procedures. The acoustic pressure wave propagation in the sonoreactor is simulated by solving the Helmholtz equation using a meshless numerical method. The paper implements both the state-of-the-art linear model and a nonlinear wave propagation model recently introduced by Louisnard (2012), and presents a novel iterative solution procedure for the nonlinear propagation model which can be implemented using any numerical method and/or programming tool. Comparative results regarding both the linear and the nonlinear wave propagation are shown. Effects of bubble size distribution and bubble volume fraction on the acoustic wave propagation are discussed in detail. The simulations demonstrate that the nonlinear model successfully captures the realistic spatial distribution of the cavitation zones and the associated acoustic pressure amplitudes. PMID:26611813

  2. Design of Mixed Batch Reactor and Column Studies at Oak Ridge National Laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Weimin [Stanford Univ., CA (United States); Criddle, Craig S. [Stanford Univ., CA (United States)

    2015-11-16

    We (the Stanford research team) were invited as external collaborators to contribute expertise in environmental engineering and field research at the ORNL IFRC, Oak Ridge, TN, for projects carried out at the Argonne National Laboratory and funded by US DOE. Specifically, we assisted in the design of batch and column reactors using ORNL IFRC materials to ensure the experiments were relevant to field conditions. During the funded research period, we characterized ORNL IFRC groundwater and sediments in batch microcosm and column experiments conducted at ANL, and we communicated with ANL team members through email and conference calls and face-to-face meetings at the annual ERSP PI meeting and national meetings. Microcosm test results demonstrated that U(VI) in sediments was reduced to U(IV) when amended with ethanol. The reduced products were not uraninite but unknown U(IV) complexes associated with Fe. Fe(III) in solid phase was only partially reduced. Due to budget reductions at ANL, Stanford contributions ended in 2011.

  3. Design of Mixed Batch Reactor and Column Studies at Oak Ridge National Laboratory

    International Nuclear Information System (INIS)

    We (the Stanford research team) were invited as external collaborators to contribute expertise in environmental engineering and field research at the ORNL IFRC, Oak Ridge, TN, for projects carried out at the Argonne National Laboratory and funded by US DOE. Specifically, we assisted in the design of batch and column reactors using ORNL IFRC materials to ensure the experiments were relevant to field conditions. During the funded research period, we characterized ORNL IFRC groundwater and sediments in batch microcosm and column experiments conducted at ANL, and we communicated with ANL team members through email and conference calls and face-to-face meetings at the annual ERSP PI meeting and national meetings. Microcosm test results demonstrated that U(VI) in sediments was reduced to U(IV) when amended with ethanol. The reduced products were not uraninite but unknown U(IV) complexes associated with Fe. Fe(III) in solid phase was only partially reduced. Due to budget reductions at ANL, Stanford contributions ended in 2011.

  4. Monte Carlo simulation of the thermal column and beam tube of the TRIGA Mark II research reactor

    Energy Technology Data Exchange (ETDEWEB)

    Khan, R., E-mail: rustamzia@yahoo.com [Atominstitute (ATI), Vienna University of Technology (TU Wien), Stadion allee 2, A-1020 Vienna (Austria); Karimzadeh, S.; Stummer, T.; Boeck, H. [Atominstitute (ATI), Vienna University of Technology (TU Wien), Stadion allee 2, A-1020 Vienna (Austria)

    2011-08-15

    Highlights: > Neutronics parameters of the reactor shielding. > Biological shielding of the TRIGA reactor. > Thermal flux measurement in the thermal column and BT-A. > MCNP model validation. - Abstract: The Monet Carlo simulation of the TRIGA Mark II research reactor core has been performed employing the radiation transport computer code MCNP5. The model has been confirmed experimentally in the PhD research work at the Atominstitute (ATI) of the Vienna University of Technology. The MCNP model has been extended to complete biological shielding of the reactor including the thermal column, radiographic collimator and four beam tubes. This paper presents the MCNP simulated results in the thermal column and one of the beam tubes (beam tube A) of the reactor. To validate these theoretical results, thermal neutron flux density measurements using the gold foil activation method have been performed in the thermal column and beam tube A (BT-A). In the thermal column, the theoretical and experimental results are in fairly good agreement i.e. maximum thermal flux density in the centre decreases in radial direction. Further, it is also agreed that thermal flux densities in the lower part is greater than the upper part of the thermal column. In the BT-A experiment, the thermal flux density distribution is measured using gold foil. The experimental and theoretical diffusion lengths have been determined as 10.77 cm and 9.36 cm respectively with only 13% difference, reflecting good agreement between the experimental and simulated results. To save the computational cost and to incorporate the accurate and complete information of each individual Monte Carlo MC particle tracks, the surface source writing capability of MCNP has been utilized to the TRIGA shielding model. The variance reduction techniques have been applied to improve the statistics of the problem and to save computational efforts.

  5. Monte Carlo simulation of the thermal column and beam tube of the TRIGA Mark II research reactor

    International Nuclear Information System (INIS)

    Highlights: → Neutronics parameters of the reactor shielding. → Biological shielding of the TRIGA reactor. → Thermal flux measurement in the thermal column and BT-A. → MCNP model validation. - Abstract: The Monet Carlo simulation of the TRIGA Mark II research reactor core has been performed employing the radiation transport computer code MCNP5. The model has been confirmed experimentally in the PhD research work at the Atominstitute (ATI) of the Vienna University of Technology. The MCNP model has been extended to complete biological shielding of the reactor including the thermal column, radiographic collimator and four beam tubes. This paper presents the MCNP simulated results in the thermal column and one of the beam tubes (beam tube A) of the reactor. To validate these theoretical results, thermal neutron flux density measurements using the gold foil activation method have been performed in the thermal column and beam tube A (BT-A). In the thermal column, the theoretical and experimental results are in fairly good agreement i.e. maximum thermal flux density in the centre decreases in radial direction. Further, it is also agreed that thermal flux densities in the lower part is greater than the upper part of the thermal column. In the BT-A experiment, the thermal flux density distribution is measured using gold foil. The experimental and theoretical diffusion lengths have been determined as 10.77 cm and 9.36 cm respectively with only 13% difference, reflecting good agreement between the experimental and simulated results. To save the computational cost and to incorporate the accurate and complete information of each individual Monte Carlo MC particle tracks, the surface source writing capability of MCNP has been utilized to the TRIGA shielding model. The variance reduction techniques have been applied to improve the statistics of the problem and to save computational efforts.

  6. Neutron flux measurement in the thermal column of the Malaysian TRIGA mark II reactor with MCNP verification

    International Nuclear Information System (INIS)

    A study of the thermal column of the Malaysian TRIGA Mark II reactor, forming part of a feasibility study for BNCT was proposed in 2001. In the current study, pure metals were used to measure the neutron flux at selected points in the thermal column and the neutron flux determined using SAND-II. Monte Carlo simulation of the thermal column was also carried out. The reactor core was homogenized and calculations of the neutron flux through the graphite stringers performed using MCNP5. The results show good agreement between the measured flux and the MCNP calculated flux. An obvious extension from this is that the MCNP neutron flux output can be utilized as an input spectrum for SAND-II for the flux iteration. (author)

  7. Burn-Up Dependence of Bubble Morphology of Uranium Silicide Dispersion Fuels Used in Research Reactor

    International Nuclear Information System (INIS)

    Burn-up dependence of fission gas bubble morphology of U3Si2-Al and U3Si-Al dispersion fuels are reviewed with the data of ANL(Argonne Nation Laboratory) and KAERI(Korea Atomic Energy Research Institute

  8. Studies on hydrodynamics of turbulent slurry bubble column ( Ⅴ )Modeling of bubble column with multi-layer screens%湍动浆态床流体力学研究(Ⅴ)带多层水平网格构件的浆态床流体力学模型

    Institute of Scientific and Technical Information of China (English)

    张煜; 李兆奇; 李红波; 王丽军; 李希

    2012-01-01

    Screen is one of the simplest resistance internals for improving the radial profile of axial velocity in a bubble column. In this paper the profiles of axial liquid velocity and gas hold up along the radius of φ500 mm X 5000 mm bubble column with multi-layer screens were measured by Pavlov tube and conductivity probe respectively. The experimental observations showed that the lateral screen internals could remarkably reduce the ascending liquid velocity in the core region, resulting in improvement of flow profiles. The smaller the screen hole, the more remarkable the resistance effect, and the higher the average gas hold up. A one dimensional CFD model similar to that of pipe bundle internals was developed, and the damping effect of screen internals on the liquid was regarded as the volumetric source of momentum, turbulent kinetic energy and dissipation. The values of parameters in the turbulent energy dissipation equation were different from the model of pipe bundle internals, and they were estimated as c3 =2. 0, c4 = 1. 3 by comparison with experimental data. The present model provided an effective tool in simulation of damping effect of multi-layer screens internals in bubble columns.%水平布置的多层筛网是最简单的阻尼型内构件,用于改善流动分布.在安装多层筛网的(φ)500 mm×5000mm鼓泡塔冷模装置中进行了流速分布与气含率分布测定.实验表明,网格型内构件可以有效抑制塔中心区过快上升的流速,改善其分布.网孔越小,流动阻尼效果越明显,同时平均气含率也会有所增大.提出了与列管内构件相似的一维流体力学模型,将网格型内构件对流体的阻尼效果作为体积源来考虑,湍流耗散方程中的参数值c3=2.0、c4 =1.3,与列管束内构件略有不同.模型计算与实验数据符合良好,能够定量描述网格型阻尼内构件对流场的影响.

  9. Modelling of microalgal growth and lipid production in Dunaliella tertiolecta using nitrogen-phosphorus-potassium fertilizer medium in sintered disk chromatographic glass bubble column.

    Science.gov (United States)

    Kumar, Anup; Guria, Chandan; Chitres, G; Chakraborty, Arunangshu; Pathak, A K

    2016-10-01

    A comprehensive mathematical model involving NPK-10:26:26 fertilizer, NaCl, NaHCO3, light and temperature operating variables for Dunaliella tertiolecta cultivation is formulated to predict microalgae-biomass and lipid productivity. Proposed model includes Monod/Andrews kinetics for the absorption of essential nutrients into algae-biomass and Droop model involving internal nutrient cell quota for microalgae growth, assuming algae-biomass is composed of sugar, functional-pool and neutral-lipid. Biokinetic model parameters are determined by minimizing the residual-sum-of-square-errors between experimental and computed microalgae-biomass and lipid productivity using genetic algorithm. Developed model is validated with the experiments of Dunaliella tertiolecta cultivation using air-agitated sintered-disk chromatographic glass-bubble column and the effects of operating variables on microalgae-biomass and lipid productivity is investigated. Finally, parametric sensitivity analysis is carried out to know the sensitivity of model parameters on the obtained results in the input parameter space. Proposed model may be helpful in scale-up studies and implementation of model-based control strategy in large-scale algal cultivation. PMID:27450983

  10. Solar Upgrade of Methane Using Dry Reforming In Direct Contact Bubble Reactor

    OpenAIRE

    Al-Ali, Khalid; Kodama, Satoshi; Kaneko, Hiroshi; Sekiguchi, Hidetoshi; Tamaura, Yutaka; Chiesa, Matteo

    2012-01-01

    The reforming behavior of a direct contact bubbling CH4-CO2 mixture, was quantitatively investigated, in an alkali carbonate based molten salt system containing suspended Ni-Al2O3 catalyst. A thermodynamical process of a solar reformer of dry methane reforming was proposed to operate in a temperature range of 600-800oC. The selectivity of the thermal fluid have been validated according to specific requirements including lower melting point, thermal and chemical stability, acting simultaneousl...

  11. The Use of the Ideal and Non-ideal Dynamic Pressure Step Method for kLa Measurement and Effect of Electrolyte Addition on Gas Holdup and kLa in Bubble Column

    Czech Academy of Sciences Publication Activity Database

    Fialová, Marie; Orvalho, Sandra; Zedníková, Mária; Růžička, Marek; Drahoš, Jiří

    Praha : Process Engineering Publisher, 2008, s. 858. ISBN 978-80-02-02050-9. [18th International Congress of Chemical and Process Engineering CHISA 2008. Praha (CZ), 24.08.2008-28.08.2008] R&D Projects: GA ČR GA104/07/1110 Institutional research plan: CEZ:AV0Z40720504 Keywords : bubble column * volumetric mass transfer coefficient * gas holdup Subject RIV: CI - Industrial Chemistry, Chemical Engineering

  12. Determination of the fluence profile in three dimension for the thermal column of the TRIGA Mark III reactor

    International Nuclear Information System (INIS)

    In this work the results of the dosimetric properties of the lithium carbonate are presented (detecting), before the thermal neutrons. The process consists on irradiating samples of lithium carbonate in the installation of the thermal column of the TRIGA Mark III reactor, with a controlled period and with time intervals of 20 hours of irradiation. It is necessary to mention that the detectors were placed in different internal positions of the thermal column. With the purpose of being used these results for future studies, like it is the fluence profile in the thermal column. To use the BNCT technique (Boron Neutron Capture Therapy). Which is a binary technique that requires the simultaneous presence of a neutron flux with appropriate energy and a neutron captor (10B), those which interacting to attack to the tumor cells without producing significant damage to the tissues when both agents are separated. (Author)

  13. Continuous Production of 6-amino Penicillanic Acid (6-APA) by Agarose Immobilized Penicillin Acylase in a Packed Column Reactor

    OpenAIRE

    Banerjee, S.; Debnath, M.

    2007-01-01

    Penicillin acylase, an industrially important biocatalyst catalyzes the conversion of penicillins to 6-amino penicillanic acid (6-APA) which is the main precursor for the production of semi-synthetic -lactam antibiotics. The present work involves the continuous production of 6-APA in a packed column reactor by using agarose immobilized penicillin acylase as a block polymer. The strain Escherichia coli ATCC 11105 was used as enzyme source and penicillin G as substrate. The acidic nature of 6-A...

  14. Continuous production of L-phenylalanine by Rhodotorula glutinis immobilized cells using a column reactor.

    Science.gov (United States)

    El-Batal, Ahmed I

    2002-01-01

    Studies have been conducted on L-phenylalanine (L-Phe) production and phenylalanine ammonia lyase (PAL) stabilization in the presence of several optimum effectors and reducing agents under bioconversion of transcinnamic acid (t-CA) conditions during repeated batch operations. L-Phe production was maximized and reuseability of PAL catalyst was extended to eight consecutive cycles (repeated batches) in the presence of optimum effectors (glutamic acid, polyethylene glycol and glycerol), thioglycolic acid and sparging with nitrogen gas. These best optimum bioconversion conditions desensitize the PAL catalyst to substantially elevated higher substrate t-CA concentrations and inhibit inactivation of PAL enzyme over longer reaction periods compared to the control. The fed batch mode operation of bioconversion of total t-CA (300 mM) to L-Phe was superior (65.2%, conversion), comparing with conventional batch and repeated batch (58.4%, conversion) operations after 120 h. Gamma irradiation process was employed to polymerize and crosslink polyvinyl alcohol (PVA) with N,N'-methylene-bisacrylamide (BIS) agent. The use of immobilized PAL biocatalyst containing cells in PVA-BIS copolymer gel carrier produced by radiation polymerization is obviously advantageous with regards to the yield of L-Phe which was increased in average 1.2-fold when compare to those obtained with free cells during optimum bioconversion process. When comparing the magnitudes of gamma irradiation effects on immobilized entrapped yeast cells in PVA-BIS copolymer gel carrier using scanning electron microscopy it was show that yeast cells were protected and capable to overcome these conditions and had normal shape and other features as free (unirradiated) intact yeast cells. Optimum conditions for continuous production of L-Phe by PVA-BIS copolymer carrier entrapped yeast cells in a packed bed column reactor in recycle fed-batch mode were investigated. Under these optimum conditions L-Phe accumulated to

  15. Process simulation of biomass gasification in a bubbling fluidized bed reactor

    International Nuclear Information System (INIS)

    Highlights: • Bubbling fluidized bed gasification of biomass is studied by computer simulation. • The effect of some critical parameters on gasification performance is studied. • The performance of air–steam gasification of wood chips is analyzed. • Model predictions are compared against available data from the literature. • The optimum operating conditions for the gasification are found. - Abstract: A detailed process model was developed to simulate the air–steam gasification of biomass in a bubbling fluidized bed for hydrogen and syngas production by coupling Aspen Plus simulator and dedicated FORTRAN subroutines. Effects of critical parameters, including gasification temperature, steam/biomass ratio (SBR), equivalence ratio (ER), and biomass particle size (BPS) on the composition of fuel gas were discussed. The results indicate that the high temperature is more favorable for production of useful syngas (H2 and CO) and hydrogen yield (HY). The simulation results also demonstrate that ER is the most important factor in the process; higher ER contributed to higher carbon conversion, tar reforming, and gas yield, however, it lowered gas caloric value and cold gas efficiency. However, steam injection recognized as a key factor to produce more hydrogen rich gas in the SBR range studied, but had a major effect on CO2 formation. The model is validated by experimental data and found relatively to be in good agreement

  16. Co-Fuelling of Peat with Meat and Bone Meal in a Pilot Scale Bubbling Bed Reactor

    Directory of Open Access Journals (Sweden)

    Markku Orjala

    2010-07-01

    Full Text Available Co-combustion performance trials of Meat and Bone Meal (MBM and peat were conducted using a bubbling fluidized bed (BFB reactor. In the combustion performance trials the effects of the co-combustion of MBM and peat on flue gas emissions, bed fluidization, ash agglomeration tendency in the bed and the composition and quality of the ash were studied. MBM was mixed with peat at 6 levels between 15% and 100%. Emissions were predominantly below regulatory limits. CO concentrations in the flue gas only exceeded the 100 mg/m3 limit upon combustion of pure MBM. SO2 emissions were found to be over the limit of 50 mg/m3, while in all trials NOx emissions were below the limit of 300 mg/m3. The HCl content of the flue gases was found to vary near the limit of 30 mg/m3. VOCs however were within their limits. The problem of bed agglomeration was avoided when the bed temperature was about 850 °C and only 20% MBM was co-combusted. This study indicates that a pilot scale BFB reactor can, under optimum conditions, be operated within emission limits when MBM is used as a co-fuel with peat. This can provide a basis for further scale-up development work in industrial scale BFB applications.

  17. Effect of helium on separation performance of cryogenic distillation column cascade for fusion reactor

    International Nuclear Information System (INIS)

    The effect of helium in the feed stream on separation performance of the cryogenic distillation columns was discussed in a probable case. The column cascade at Los Alamos National Laboratory was chosen in the present study. The new data for solubility of helium in liquid hydrogen isotopes was used in the present study. Column (2) is mainly affected by the presence of helium in the fuel stream. If the helium percentage in the feed stream is 1%, the column performance can be assured by increasing the condenser load: a larger inner diameter of the column; larger flow rate of the refrigerant gas; and larger heat transfer area at the condenser should be considered. If the percentage is 5%, both the column pressure and condenser load must be doubled in the steady-state operation. These results qualitatively agreed with the simulation results by Kinoshita in which the old data for solubility of helium were used. (author)

  18. VELOCITY AND CONCENTRATION OF BUBBLES IN OZONIZATION COLUMNS WITH CROSS SECTIONS OF DIFFERENT SIZES VELOCIDAD Y CONCENTRACIÓN DE BURBUJAS EN COLUMNAS DE OZONIZACIÓN CON SECCIÓN TRANSVERSAL DE TAMAÑOS DIVERSOS

    Directory of Open Access Journals (Sweden)

    Marcio Ricardo Salla

    2008-12-01

    Full Text Available The size of the cross section of an ozonization column influences its hydrodynamic characteristics, which, on its turn, has effects on phenomena that depend on the relative movement between gas bubbles and liquid. To observe the influence of the cross sectional area on gas concentration and bubbles velocity, two columns were used. The first column had a square cross section with side of 0.19m and the second had a circular cross section with diameter of 0.10 m. The ascendant velocities of the bubbles and their concentration were measured in both columns and compared. The transversal spread of the plumes of bubbles was also quantified. The results show that the increase of the cross section of the column, in the proportion studied here, does not result in a similar increase of the cross section of the ascending plume of bubbles. Furthermore, the results of average velocities and concentrations obtained for the smallest cross section resulted independent of the liquid level in the column, while the results for the largest cross section showed to be dependent of this level. The ratio between the cross sectional areas of the larger and the smaller plumes of bubbles decreases for higher distances to the bottom of the columns.La sección transversal de una columna de ozonización posee influencia directa sobre las características hidrodinámicas de esa columna, lo que se refleja en los fenómenos que dependen de la transferencia de masa en la interfase gas-líquido. En este estudio se utilizaron dos columnas con secciones transversales diferentes cuanto a la forma y al tamaño. La primera con sección transversal cuadrada de 0,19m y la segunda con sección transversal circular de 0,10 m de diámetro. Se midieron las velocidades ascensionales de las burbujas y su concentración. Los resultados obtenidos muestran que el aumento de la sección transversal en la proporción aquí estudiada no conlleva un aumento semejante de la sección transversal de la

  19. 多级鼓泡塔内液体速度分布的实验研究%Experimental study on liquid velocity distribution in multi-stage bubble column

    Institute of Scientific and Technical Information of China (English)

    樊亚超; 靳海波; 秦岭; 杨索和; 何广湘

    2011-01-01

    液体循环流动是多级鼓泡塔重要流体力学特征之一,文中在内径为282 mm,高2000 mm的鼓泡塔内,采用不同类型的筛板将普通鼓泡塔分割成双级气液鼓泡塔.采用Pavlov管测液速的方法考察了不同筛板、不同表观气速下该鼓泡塔中上下二侧的液体速度分布.根据实验结果得出了液体速度在塔中心处最大,且与表观气速有关,随着表观气速的增大而增大;气液鼓泡塔内液速分布呈半抛物线状,在量纲一径向位置0.7左右处,液体速度方向发生改变;加入筛板后,径向速度区发生改变,转折点的位置与筛板的类型有关;同时筛板的加入对鼓泡塔的湍流会有一定程度的抑制,筛板对鼓泡塔上侧液速径向分布的影响明显大于对鼓泡塔下侧液速径向分布的影响.%The characteristic of liquid circulation flow is an important feature of hydrodynamics in multi-stage bubble columns. A bubble column of 282 mm in diameter and 2000 mm in height was selected, and various kinds of sieve plates were introduced to divide a conventional gas-liquid column into a two-stage gas-liquid bubble column. The effects of sieve plate and superficial gas velocity on the liquid velocity distribution in the upper and the lower of the multi-stage gas-liquid bubble column were studied by the method of Pavlov tube. The experimental results show that the maximum liquid velocity appears in the center of the bubble column, and increases with an increase of superficial gas velocity. The curves of liquid velocity distribution are half-parabolic in a gas-liquid bubble column, and liquid velocity direction is changed at around 0. 7 of dimensional-one radial direction. Meanwhile, the introduction of sieve plate suppresses the liquid turbulent flow, and affects the inversion point of liquid velocity. Moreover, the value of inversion point changes with the difference of sieve plate structure. The radial distribution of liquid velocity on the

  20. Hydrodynamic causes and effects of air bubbles rising in very viscous media

    CERN Document Server

    Ravinuthala, Sharad Chand

    2013-01-01

    Detailed understanding of two-phase gas liquid flows is imperative for developing efficient multi-phase reactors through precise control of mixing and reaction kinetics. The bubble column is a good apparatus for elementary studies of such flows. In the current study experiments are conducted to assess the effect of liquid viscosity on flow dynamics inside a bubble column. Corn oil and water are used as the continuous media, and air was the dispersed media. The objective of this effort is to use the results for a qualitative validation of the numerical simulations.

  1. Determination of Imidacloprid and metabolites by liquid chromatography with an electrochemical detector and post column photochemical reactor

    International Nuclear Information System (INIS)

    A procedure for the determination of Imidacloprid and its main metabolites was set up by means of liquid chromatography with an electrochemical detector and post-column photochemical reactor (LC-hν-ED). Sample clean-up was developed for bees, filter paper and maize leaves. Chromatographic conditions were based on a reversed-phase C-18 column operated by phosphate buffer 50 mM/CH3CN (80/20, v/v) at pH 2.9. Detection of Imidacloprid and its metabolites was performed at a potential of 800 mV after photoactivation at 254 nm. Compared to conventional techniques such as gas chromatography/mass spectrometry (GC/MS) or LC coupled to other detectors, the present method allows simultaneous trace-level determination of both Imidacloprid (0.6 ng ml-1) and its main metabolites (2.4 ng ml-1)

  2. Parameters measurement for the thermal neutron beam in the thermal column hole of Xi’an pulse reactor

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The distribution of the neutron spectra in the thermal column hole of Xi’an pulse reactor was measured with the time-of-flight method.Compared with the thermal Maxwellian theory neutron spectra,the thermal neutron spectra measured is a little softer,and the average neutron energy of the experimental spectra is about 0.042±0.01 eV.The thermal neutron fluence rate at the front end of thermal column hole,measured with gold foil activation techniques,is about 1.18×105 cm-2 s-1.The standard uncertainty of the measured thermal neutron fluence is about 3%.The spectra-averaged cross section of 197Au(n,γ) determined by the experimental thermal neutron spectra is(92.8±0.93) ×10-24 cm2.

  3. Measurement of bromate in bread by liquid chromatography with post-column flow reactor detection.

    Science.gov (United States)

    Himata, K; Noda, M; Ando, S; Yamada, Y

    2000-01-01

    This method is suitable for the determination of bromate residues in a variety of baked goods. The peer-verified method trial was performed on white bread, multigrain bread, and coffee cake spiked with known levels of potassium bromate. The analytical portion is extracted with deionized water to remove bromate from the bulk of the baked product. The aqueous extract is carried through a series of steps to remove co-extractives that would interfere with the liquid chromatography (LC) in the determinative step or hasten the deterioration of the LC column. The extract is filtered before passing it through a reversed-phase solid-phase extraction (SPE) column and a cation-exchange column in the silver form to remove lipids and chloride, respectively. Ultrafiltration is then used to remove proteins with molecular weights of >30,000 daltons. Finally, a cation-exchange column in the sodium form is used to remove silver ions from the extract. The determinative step uses LC with a reversed-phase column and an ion-pairing agent in the mobile phase. Detection is based on the post-column reaction of bromate with o-dianisidine to form an oxidation product that is quantitated spectrophotometrically at 450 nm. Overall agreement between the submitting and peer laboratories was quite good. For bromate levels of 10-52 ppb, overall mean recoveries were 76.9 and 78.8% for the submitting and peer laboratories, respectively. The standard deviations were higher for the results of the peer laboratory, probably because of the generally higher level of baseline noise present in the chromatograms. The results demonstrate that the method provides adequate accuracy with low-fat as well as high-fat foods. Bromate at levels as low as 5 ppb (ng/g) can be detected with the method. PMID:10772172

  4. 射流鼓泡反应器的混合特性%Mixing characteristics in jet bubbling reactor

    Institute of Scientific and Technical Information of China (English)

    郭天琪; 黄正梁; 王靖岱; 蒋斌波; 阳永荣

    2015-01-01

    射流鼓泡反应器以液体射流代替搅拌实现液相混合,具有结构简单、制造及维护费用低等诸多优点,研究其混合特性对于反应器的设计、优化及放大具有重要意义。以空气-水作为模拟介质,采用KCl电解质溶液为示踪剂考察了表观气速和射流Reynolds数的大小对液相宏观混合时间的影响,并从能量输入的角度对射流鼓泡反应器的混合机制进行分析。研究发现,在实验条件下(表观气速变化范围为0.0006~0.0343 m·s−1,射流Reynolds数的变化范围为1.75×104~7.00×104),鼓泡的加入使得均相射流反应器内的液相混合得到改善;随着表观气速增大,液相宏观混合时间先缩短后延长;当气体输入功率或液体输入功率不变时,混合时间随总输入功率的增大而缩短。通过对多组实验数据的回归分析,提出了液相宏观混合时间与液体输入功率和气体输入功率的经验关联式,计算值与实际值吻合较好。最后基于提出的关联式,发现当总输入功率一定时,混合时间随气体输入功率的增加先缩短后延长,临界转变点在气体输入功率为总功率的61%处,此时气液两相协同作用最强。%The jet bubbling reactor uses liquid jet to achieve the liquid mixing instead of mechanical stirring, which brings several advantages such as simple structure and low cost of maintenance and manufacturing. The research of its mixing characteristics plays a significant role in the design, optimization and scaling up of the reactor. Based on the air-water system, the electrolyte tracer (KCl solution) method was applied to investigate the influences of gas velocity and jet Reynolds number on the liquid mixing time with the cold model experimental apparatus. The mixing mechanism in jet bubbling reactor had also been analyzed from the perspective of power input. The results showed that within the experimental range (ugfrom 0

  5. Neutron flux measurements with Monte Carlo verification at the thermal column of a TRIGA MARK II reactor: Feasibility study for a BNCT facility

    International Nuclear Information System (INIS)

    The treatment of the malignant brain tumor through Boron Neutron Capture Therapy (BNCT) requires a high-flux neutron source. The Malaysian TRIGA Mark II reactor was investigated for a proposed BNCT facility. The neutron flux was measured along the central stringer of the thermal column and the outermost positions of the other stringers. The unfolding foil method was applied here. We have used Al, As, Au, Co, In, Mo, Ni and Re foils and Cd as a cover with 19 useful reactions in this study. The infinitely diluted foil activity was calculated and used in the SAND-II code (Spectrum Analysis by Neutron Detectors) to calculate the neutron flux. The reactor was also simulated using Monte Carlo code (MCNP5) and the neutron flux was calculated along the thermal column. The measured and calculated neutron flux along the thermal column show good agreement. The minimum epithermal neutron intensity required for BNCT is achieved up to position 22 with a mixed neutron-gamma beam. A suggested MCNP simulated modification of the reactor thermal column increased the neutron flux at distant positions from the reactor core but the epithermal neutron part was below the minimum requirement for a BNCT facility. The photon flux calculations along the thermal column show relatively high results which should be filtered. The calculation of the neutron and gamma dose in a head phantom (water) indicated that the available neutron spectrum requires modifications to increase the epithermal part of the neutrons and filter the gamma ray contamination. (author)

  6. Dynamic Modeling and Control Studies of a Two-Stage Bubbling Fluidized Bed Adsorber-Reactor for Solid-Sorbent CO{sub 2} Capture

    Energy Technology Data Exchange (ETDEWEB)

    Modekurti, Srinivasarao; Bhattacharyya, Debangsu; Zitney, Stephen E.

    2013-07-31

    A one-dimensional, non-isothermal, pressure-driven dynamic model has been developed for a two-stage bubbling fluidized bed (BFB) adsorber-reactor for solid-sorbent carbon dioxide (CO{sub 2}) capture using Aspen Custom Modeler® (ACM). The BFB model for the flow of gas through a continuous phase of downward moving solids considers three regions: emulsion, bubble, and cloud-wake. Both the upper and lower reactor stages are of overflow-type configuration, i.e., the solids leave from the top of each stage. In addition, dynamic models have been developed for the downcomer that transfers solids between the stages and the exit hopper that removes solids from the bottom of the bed. The models of all auxiliary equipment such as valves and gas distributor have been integrated with the main model of the two-stage adsorber reactor. Using the developed dynamic model, the transient responses of various process variables such as CO{sub 2} capture rate and flue gas outlet temperatures have been studied by simulating typical disturbances such as change in the temperature, flowrate, and composition of the incoming flue gas from pulverized coal-fired power plants. In control studies, the performance of a proportional-integral-derivative (PID) controller, feedback-augmented feedforward controller, and linear model predictive controller (LMPC) are evaluated for maintaining the overall CO{sub 2} capture rate at a desired level in the face of typical disturbances.

  7. The role of acid incubation in rapid immobilization of hydrogen-producing culture in anaerobic upflow column reactors

    International Nuclear Information System (INIS)

    An approach of acidification was examined on formation of hydrogen-producing granules and biofilms in upflow column-shaped reactors. The reactors were fed with synthetic glucose wastewater and operated at 37 C and pH 5.5. The acclimated anaerobic culture was inoculated in four reactors designated R1, R2, R3 and R4, with R3 and R4 filled with granular activated carbon as support medium. To unveil the roles of acidification, microbial culture in R2 and R3 was subject to an acid incubation for 24 h by shifting the culture pH from 5.5 to 2.0. The experimental results suggested that the acidification substantially accelerated microbial granulation, but not biofilm formation. Microbial activities were inhibited by the acid incubation for about 78 h, resulting in the retarded formation of biofilms of the acidified culture. Reducing culture pH resulted in improvement in cell surface physicochemical properties favoring microbial adhesion and immobilization. Zeta potential increased from -25.3 mV to 11.9 mV, hydrophobicity in terms of contact angle improved from 31 to 38 and production of extracellular polymers increased from 66 mg/g-VSS to 136 mg/g-VSS. As a result of the formation of granules and biofilms, high hydrogen production rates of 6.98 and 7.49 L/L h were achieved in granule-based and biofilm-based reactors, respectively. It is concluded that acid incubation is an efficient means to initiate the rapid formation of granules by regulating the surface characteristics of microbial culture. The use of support media as starting nuclei may result in rapid formation of biofilms without the acidification. (author)

  8. Chaotic behavior of water column oscillator simulating pressure balanced injection system in passive safety reactor

    International Nuclear Information System (INIS)

    Japan Atomic Energy Research Institute (JAERI) proposed a passive safety reactor called the System-integrated Pressurized Water Reactor (SPWR). In a loss of coolant accident, the Pressurizing Line (PL) and the Injection Line (IL) are passively opened. Vapor generated by residual heat pushes down the water level in the Reactor Vessel (RV). When the level is lower than the inlet of the PL, the vapor is ejected into the Containment Vessel (CV) through the PL. Then boronized water in the CV is injected into the RV through the IL by the static head. In an experiment using a simple apparatus, gas ejection and water injection were found to occur alternately under certain conditions. The gas ejection interval was observed to fluctuate considerably. Though stochastic noise affected the interval, the experimental results suggested that the large fluctuation was produced by an inherent character in the system. A set of piecewise linear differential equations was derived to describe the experimental result. The large fluctuation was reproduced in the analytical solution. Thus it was shown to occur even in a deterministic system without any source of stochastic noise. Though the derived equations simulated the experiment well, they had ten independent parameters governing the behavior of the solution. There appeared chaotic features and bifurcation, but the analytical model was too complicated to examine the features and mechanism of bifurcation. In this study, a new simple model is proposed which consists of a set of piecewise linear ordinary differential equations with only four independent parameters. (authors)

  9. Catalytic hydrogenation reactors for the fine chemicals industries. Their design and operation.

    OpenAIRE

    Westerterp, K.R.; Molga, E.J.; Gelder, van, M.

    1997-01-01

    The design and operation of reactors for catalytic, hydrogenation in the fine chemical industries are discussed. The requirements for a good multiproduct catalytic hydrogenation unit as well as the choice of the reactor type are considered. Packed bed bubble column reactors operated without hydrogen recycle are recommended as the best choice to obtain a flexible reactor with good selectivities. The results of an experimental study of the catalytic hydrogenation of 2,4-dinitrotoluene in a mini...

  10. Heat and masstransfer in bubble column at high pressure%高压下鼓泡塔中的热量和能量传递

    Institute of Scientific and Technical Information of China (English)

    吴元欣; Al-Dahhan.M.H.

    2002-01-01

    Bubble comumn and slurry bubble comumn are used in a wide range of industrial applications including processing of hydrocabons,FT synthesis and direct coal liquefaction due to the fact that bubble comumns are simple in their construction and operation.However a major problem that continues to limit their industrial application involves difficulties in scale up the results from small laboratory equipment to large industrial significant units.Often results from the smallscale test units cannot be achieved when the plant size is increased.Hence,their design and scaleup still is a difficult task.The heat and mass transfer properties,which cause the scaleup problem,are important factors to affect the performance of bublle coumns.In this review,the literature published in recent years involving heattransfer and mass transfer in bubble comumn/slurry bubble comumn at high pressure is revisited.%由于其结构简单和操作方便, 鼓泡塔和浆态鼓泡塔广泛应用于各种工业过程,如加成、羰基合成、煤的直接液化等.不过,由于放大过程中的问题不能很好地解决,一直限制着这类反应的应用,经常的问题是小试的结果不能在放大的过程中实现.热量和质量的传递问题是放大过程中需要考虑的重要因素,因为热量和质量等传递问题正是引起放大问题的根源所在.本文总结了近年来发表在公开文献中有关高压下鼓泡塔和浆态鼓泡塔中热量和能量传递的研究结果并给予了评论.

  11. Science Bubbles

    DEFF Research Database (Denmark)

    Hendricks, Vincent Fella; Pedersen, David Budtz

    2013-01-01

    Much like the trade and trait sof bubbles in financial markets,similar bubbles appear on the science market. When economic bubbles burst, the drop in prices causes the crash of unsustainable investments leading to an investor confidence crisis possibly followed by a financial panic. But when...... bubbles appear in science, truth and reliability are the first victims. This paper explores how fashions in research funding and research management may turn science into something like a bubble economy....

  12. Reactor column and neutron absorber and method of manufacturing the same

    International Nuclear Information System (INIS)

    The present invention concerns a neutron absorbing member of a pulse column for use in purification of highly level radioactive solutions generated in a spent fuel reprocessing plant. The neutron absorbing member comprises a cylindrical member supported by a large-diameter cylindrical portion and a core comprising a neutron moderator contained in the inside. The cylindrical member consists of a neutron absorber, and a neutron absorbing layer having a highly neutron absorbing performance is disposed between the neutron absorber. Since the cylindrical member is constituted by disposing neutron absorbing layer between the neutron absorbers, neutrons generated from the liquid in the inside are absorbed by the absorbing layer, and since neutrons not absorbed are absorbed by the neutron absorbing member after being moderated by the core, the neutron absorbing performance can be improved. The neutron moderating performance can be improved by constituting the core with polyethylene, and since it is light in weight, the cost for the construction of the fixed structural members can be reduced. In addition, if cadmium is used, the performance can be further improved. (N.H.)

  13. Reaction of dissolved ozone in hydrogen peroxide produced during ozonization of an alkaline medium in a bubble column - doi: 10.4025/actascitechnol.v36i1.11834

    Directory of Open Access Journals (Sweden)

    Marco Aurélio Cremasco

    2014-01-01

    Full Text Available The effect of a reaction of dissolved ozone in an alkaline water solution with hydrogen peroxide was evaluated. Assays were conducted in a bubble column with a gaseous ozone concentration (mixed with oxygen at 21 and 27 g m-3. Concentration curve of dissolved ozone in the liquid revealed an ozone concentration peak in the liquid phase, subsequent decreasing concentration and constant maintenance in the stationary phase. Highest concentration was not detected for the lowest ozone concentration in the gaseous phase. Peak was due to the self-decomposition of ozone in the liquid phase and the production of hydrogen peroxide. The latter reacted with molecular dissolved ozone and decreased ozone concentration after maximum concentration.

  14. Effects of reactor type and mass transfer on the morphology of CuS and ZnS crystals

    NARCIS (Netherlands)

    Al-Tarazi, M.; Heesink, A. Bert M.; Versteeg, G. F.

    2005-01-01

    For the precipitation of CuS and ZnS, the effects of the reactor/precipitator type, mass transfer and process conditions on crystal morphology were studied. Either H2S gas or a S2- solution were applied. Three different types of reactors have been tested, namely a laminar jet, a bubble column and an

  15. Bubble dielectrophoresis

    Science.gov (United States)

    Jones, T. B.; Bliss, G. W.

    1977-01-01

    The theoretical principles related to bubble dielectrophoresis are examined, taking into account the polarization force, aspects of bubble deformation, the electrostatic bubble levitation theorem, and the equation of motion. The measurement of the dielectrophoretic force on static and dynamic bubbles represents a convenient experimental method for the study of the general problem of dielectrophoresis. The experiments reported include static-force measurements, static-levitation experiments, and dynamic-force measurements.

  16. Development of post-column enzymic reactors with immobilized alcohol oxidase for use in the high-performance liquid chromatographic assay of alcohols with electrochemical detection.

    Science.gov (United States)

    Tagliaro, F; Schiavon, G; Dorizzi, R; Marigo, M

    1991-01-18

    The development of a very sensitive, direct injection high-performance liquid chromatographic method, using a post-column reactor with immobilized alcohol oxidase, was undertaken with the aim of determining methanol and ethanol levels in microlitre volumes of biological samples. After reversed-phase chromatography to separate methanol and ethanol, the analytes were enzymically converted into the respective aldehydes with formation of stoichiometric amounts of hydrogen peroxide, which could be measured via electrochemical oxidation at a platinum electrode. Some problems were encountered in the development of solid-phase enzymic reactors, using a delicate enzyme, that is prone to lose activity, such as alcohol oxidase. Owing to the slightly alkaline pH required for the optimum activity of alcohol oxidase, polymeric columns seemed to be preferable for the chromatography. HEMA copolymer was chosen as the stationary phase, but the methanol and ethanol peaks eluted close together and posed severe problems of limiting post-column band spreading. Reactors based on coarse supports for enzyme immobilization gave unacceptable band spreading, causing the methanol and ethanol peaks to overlap. On the other hand high-performance liquid chromatographic packings maintained the efficiency of the chromatographic separation, quite independently of the reactor volume. Polymeric supports proved superior to silicas in maintaining the enzyme activity. However, relevant changes in the enzyme substrate specificity were observed after immobilization. PMID:2061376

  17. Bubble rupture in bubble electrospinning

    Directory of Open Access Journals (Sweden)

    Chen Rouxi

    2015-01-01

    Full Text Available As the distinctive properties and different applications of nanofibers, the demand of nanofibers increased sharply in recently years. Bubble electrospinning is one of the most effective and industrialized methods for nanofiber production. To optimize the set-up of bubble electrospinning and improve its mass production, the dynamic properties of un-charged and charged bubbles are studied experimentally, the growth and rupture process of a bubble are also discussed in this paper.

  18. A Bubble Detection Algorithm Based on Sparse and Redundant Image Processing

    Directory of Open Access Journals (Sweden)

    Ye Tian

    2013-06-01

    Full Text Available Deinked pulp flotation column has been applied in wastepaper recycling. Bubble size in deinked pulp flotation column is very important during the flotation process. In this paper, bubble images of deinked pulp flotation column were first caught by digital camera, and then the bubbles were detected by using a detection algorithm based on sparse and redundant image processing. The results show the algorithms are very practical and effective on bubble detection in deinked pulp flotation column.

  19. Simple Model for Gas Holdup and Liquid Velocity of Annular Photocatalytic External-Loop Airlift Reactor Under both Bubble and Developing Slug Flow

    Institute of Scientific and Technical Information of China (English)

    王一平; 陈为强; 黄群武; 冯加和; 崔勇

    2016-01-01

    Based on the momentum conservation approach, a theoretical model was developed to predict the su-perficial liquid velocity, and a correlation equation was established to calculate the gas holdup of an annular exter-nal-loop airlift reactor(AELAR)in the bubble flow and developing slug flow pattern. Experiments were performed by using tap-water and silicone oil with the viscosity of 2.0 mm2/s(2cs-SiO)and 5.0 mm2/s(5cs-SiO)as liquid phases. The effects of liquid viscosity and flow pattern on the AELAR performance were investigated. The predic-tions of the proposed model were in good agreement with the experimental results of the AELAR. In addition, the comparison of the experimental results shows that the proposed model has good accuracy and could be used to pre-dict the gas holdup and liquid velocity of an AELAR operating in bubble and developing flow pattern.

  20. Simultaneous measurement of local particle movement, solids concentrations and bubble properties in fluidized bed reactors using a novel fiber optical technique

    Energy Technology Data Exchange (ETDEWEB)

    Tayebi, Davoud

    1998-12-31

    This thesis develops a new method for simultaneous measurements of local flow properties in highly concentrated multiphase flow systems such as gas-solid fluidized bed reactors. The method is based on fiber optical technique and tracer particles. A particle present in the measuring volume in front of the probe is marked with a fluorescent dye. A light source illuminates the particles and the detecting fibres receive reflected light from uncoated particles and fluorescent light from the tracer particle. Using optical filters, the fluorescent light can be distinguished and together with a small fraction of background light from uncoated particles can be used for determination of local flow properties. Using this method, one can simultaneously measure the local movement of a single tracer particle, local bubble properties and the local solids volume fractions in different positions in the bed. The method is independent of the physical properties of the tracer particles. It is also independent of the local solids concentrations in the range of 0 to 60 vol.-%, but is mainly designed for highly concentrated flow systems. A computer programme that uses good signals from at least three sensors simultaneously to calculate the tracer particle velocity in two dimensions have been developed. It also calculates the bubble properties and local solids volume fractions from the same time series. 251 refs., 150 figs., 5 tabs.

  1. A five years experience of pulse columns extraction cycles for the reprocessing of fast breeder reactor fuels at the Marcoule pilot plant (SAP)

    International Nuclear Information System (INIS)

    The reprocessing of Phenix fast breeder reactor started at the MARCOULE PILOT PLANT in 1977 with the enriched UO2 first core (2.3 tons U) followed by several campaigns of UO2-PuO2 Phenix-core II (6.5 tons U-Pu). After a short description of the Pilot Plant, characteristics of the pulse columns extraction flow-sheets are presented. Pulse columns are used for extraction and scrubbing of uranium and plutonium and for uranium backwashing whilst plutonium stripping and U-Pu partition are carried out in mixer settlers with HAN and in-line electrolytic U IV generation. Performances of pulsed columns including recovery yields and decontamination factors are discussed: they show a good β γ decontamination can be reached with two cycles and partition carried out at the second cycle. (author)

  2. A five years experience of pulse columns extraction cycles for the reprocessing of fast breeder reactor fuels at the Marcoule pilot plant (SAP)

    International Nuclear Information System (INIS)

    The reprocessing of Phenix fast breeder reactor started at the Marcoule Pilot Plant in 1977 with the enriched UO2 first core (2.3 tons U) followed by several campaigns of UO2-PuO2 Phenix-core II (6.5 tons U-Pu). After a short description of the Pilot Plant, characteristics of the pulse columns extraction flow-sheets are presented. Pulse columns are used for extraction and scrubbing of uranium and plutonium and for uranium backwashing whilst plutonium stripping and U-Pu partition are carried out in mixer settlers with HAN and in-line electrolytic U IV generation. Performances of pulsed columns including recovery yields and decontamination factors are discussed: they show a good β γ decontamination can be reached with two cycles and partition carried out at the second cycle

  3. Computational Modeling and Simulations of Hydrodynamics for Air-Water External Loop Airlift Reactors

    OpenAIRE

    Law, Deify

    2010-01-01

    External loop airlift reactors are widely used for biochemical applications such as syngas fermentation and wastewater treatment. To further understand the inherent gas-liquid flow physics within the reactors, computational modeling and simulations of hydrodynamics for air-water external loop airlift reactors were investigated. The gas-liquid flow dynamics in a bubble column were simulated using a FORTRAN code developed by Los Alamos National Laboratory, CFDLib, which employs an Eulerian-Eule...

  4. Experimental evaluation of the oxygen transfer in bubble aeration systems. Full scale experiences in lengthened activated sludge reactors

    International Nuclear Information System (INIS)

    The results of some full-scale oxygen transfer measurements conduced at the lengthened activate sludge tanks of two WWTPs of Trentino Region, are presented and discussed. As far at the tests in clean water are concerned, the non-liner regression method seems non accurate; important conclusion on the correlation between oxygen transfer process and typical parameters (i.e., fine-bubble diffusers, specific air flux) are derived. As far as the test in the wastewater is concerned, an increase of α-value from the inlet to the end of aeration tanks has been observed in the 'Andalo' WWTP

  5. Hydrodynamics in a swarm of rising bubbles

    International Nuclear Information System (INIS)

    In many applications, bubbles are used to agitate a liquid in order to enhance mixing and transfer. This work is devoted to the study of the hydrodynamics in a stable bubble column. Experimentally, we have determined the properties of the velocity fluctuations inside and behind a homogeneous swarm of rising bubbles for different bubble sizes and gas volume fractions α: self-similarity in α0,4, spectrum in k-3 and integral length scale controlled by buoyancy. Numerically, we have reproduced these properties by means of large-scale simulations, the bubbles being modeled by volume-forces. This confirms that the dynamics is controlled by wake interactions. (author)

  6. Bubble systems

    CERN Document Server

    Avdeev, Alexander A

    2016-01-01

    This monograph presents a systematic analysis of bubble system mathematics, using the mechanics of two-phase systems in non-equilibrium as the scope of analysis. The author introduces the thermodynamic foundations of bubble systems, ranging from the fundamental starting points to current research challenges. This book addresses a range of topics, including description methods of multi-phase systems, boundary and initial conditions as well as coupling requirements at the phase boundary. Moreover, it presents a detailed study of the basic problems of bubble dynamics in a liquid mass: growth (dynamically and thermally controlled), collapse, bubble pulsations, bubble rise and breakup. Special emphasis is placed on bubble dynamics in turbulent flows. The analysis results are used to write integral equations governing the rate of vapor generation (condensation) in non-equilibrium flows, thus creating a basis for solving a number of practical problems. This book is the first to present a comprehensive theory of boil...

  7. Bubble Combustion

    Science.gov (United States)

    Corrigan, Jackie

    2004-01-01

    A method of energy production that is capable of low pollutant emissions is fundamental to one of the four pillars of NASA s Aeronautics Blueprint: Revolutionary Vehicles. Bubble combustion, a new engine technology currently being developed at Glenn Research Center promises to provide low emissions combustion in support of NASA s vision under the Emissions Element because it generates power, while minimizing the production of carbon dioxide (CO2) and nitrous oxides (NOx), both known to be Greenhouse gases. and allows the use of alternative fuels such as corn oil, low-grade fuels, and even used motor oil. Bubble combustion is analogous to the inverse of spray combustion: the difference between bubble and spray combustion is that spray combustion is spraying a liquid in to a gas to form droplets, whereas bubble combustion involves injecting a gas into a liquid to form gaseous bubbles. In bubble combustion, the process for the ignition of the bubbles takes place on a time scale of less than a nanosecond and begins with acoustic waves perturbing each bubble. This perturbation causes the local pressure to drop below the vapor pressure of the liquid thus producing cavitation in which the bubble diameter grows, and upon reversal of the oscillating pressure field, the bubble then collapses rapidly with the aid of the high surface tension forces acting on the wall of the bubble. The rapid and violent collapse causes the temperatures inside the bubbles to soar as a result of adiabatic heating. As the temperatures rise, the gaseous contents of the bubble ignite with the bubble itself serving as its own combustion chamber. After ignition, this is the time in the bubble s life cycle where power is generated, and CO2, and NOx among other species, are produced. However, the pollutants CO2 and NOx are absorbed into the surrounding liquid. The importance of bubble combustion is that it generates power using a simple and compact device. We conducted a parametric study using CAVCHEM

  8. Maximization of organic acids production by Aspergillus niger in a bubble column bioreactor for V and Ni recovery enhancement from power plant residual ash in spent-medium bioleaching experiments.

    Science.gov (United States)

    Rasoulnia, P; Mousavi, S M

    2016-09-01

    Spent-medium bioleaching of V and Ni from a power plant residual ash (PPR ash) was conducted using organic acids produced by Aspergillus niger. The production of organic acids in a bubble column bioreactor was optimized through selecting three most influencing factors. Under optimum condition of aeration rate of 762.5(ml/min), sucrose concentration of 101.9(g/l) and inoculum size of 40(ml/l), respectively 17,185, 4539, 1042 and 502(ppm) of oxalic, gluconic, citric and malic acids were produced. Leaching experiments were carried out using biogenic produced organic acids under leaching environment temperature of 60°C and rotary shaking speed of 135rpm, with various pulp densities of 1, 2, 3, 5, 7 and 9(%w/v). The results showed that biogenic produced organic acids leached V much more efficiently than Ni so that even at high pulp density of 9(%w/v), 83% of V was recovered while Ni recovery yield was 30%. PMID:27295250

  9. Mathematical modeling of a slurry reactor for DME direct synthesis from syngas

    Institute of Scientific and Technical Information of China (English)

    Sadegh Papari; Mohammad Kazemeini; Moslem Fattahi

    2012-01-01

    In this paper,an axial dispersion mathematical model is developed to simulate a three-phase slurry bubble column reactor for direct synthesis of dimethyl ether (DME) from syngas.This large-scale reactor is modeled using mass and energy balances,catalyst sedimentation and single-bubble as well as two-bubbles class flow hydrodynamics.A comparison between the two hydrodynamic models through pilot plant experimental data from the literature shows that heterogeneous two-bubbles flow model is in better agreement with the experimental data than homogeneous single-bubble gas flow model.Also,by investigating the heterogeneous gas flow and axial dispersion model for small bubbles as well as the large bubbles and slurry (i.e.including paraffins and the catalyst) phase,the temperature profile along the reactor is obtained.A comparison between isothermal and non-isothermal reactors reveals no obvious performance difference between them.The optimum values of reactor diameter and height were obtained at 7 m and 50 m,respectively.The effects of operating variables on the axial catalyst distribution,DME productivity and CO conversion are also investigated in this research.

  10. Bubble puzzles

    NARCIS (Netherlands)

    Lohse, Detlef

    2003-01-01

    With their ubiquitous occurrence in a multitude of fluid systems, bubbles occupy an important place in contemporary science and technology. One can readily cite several examples: the production and transport of oil, in which bubbles are purposely injected to help lift heavy oil to the surface; energ

  11. Ultrasonics - a new method of bubble detection and level measuring in the main coolant lines of PWR reactors

    International Nuclear Information System (INIS)

    According to many experts, level measurements in the pressurizer do not give reliable information on the coolant level for all accident conditions. In PWR reactors, ultrasonic measurement at right angles to the flow direction using a piezoelectric ultrasonic transducer acting intermittently as transmitter and receiver is the most appropriate method. (orig./GL)

  12. Bubble, Bubble, Toil and Trouble.

    Science.gov (United States)

    Journal of Chemical Education, 2001

    2001-01-01

    Bubbles are a fun way to introduce the concepts of surface tension, intermolecular forces, and the use of surfactants. Presents two activities in which students add chemicals to liquid dishwashing detergent with water in order to create longer lasting bubbles. (ASK)

  13. A Bubble Detection Algorithm Based on Sparse and Redundant Image Processing

    OpenAIRE

    Ye Tian(University of South Carolina); Change Zheng; Qiuhong Ke

    2013-01-01

    Deinked pulp flotation column has been applied in wastepaper recycling. Bubble size in deinked pulp flotation column is very important during the flotation process. In this paper, bubble images of deinked pulp flotation column were first caught by digital camera, and then the bubbles were detected by using a detection algorithm based on sparse and redundant image processing. The results show the algorithms are very practical and effective on bubble detection in deinked pulp flotation co...

  14. Experimental and numerical study of the migration of gas bubbles through an interface between two liquids

    International Nuclear Information System (INIS)

    In order to predict the evolution of a hypothetical accident in pressurized water nuclear reactors, this study aims to understand the dynamics of gas bubbles ascending in a stratified mixture made of two superimposed liquids. To this aim, an experimental device equipped with two high-speed video cameras was designed, allowing us to observe isolated air bubbles and bubble trains crossing a horizontal interface separating two Newtonian immiscible liquids initially at rest. The size of the bubbles and the viscosity contrast between the two liquids were varied by more than one and four orders of magnitude respectively, making it possible to observe a wide variety of flow regimes. In some situations, small millimetric bubbles remain trapped at the liquid-liquid interface, whereas larger bubbles succeed in crossing the interface and tow a significant column of lower fluid behind them. After the influence of the physical parameters was qualitatively established thanks to simple models, direct numerical simulations of several selected experimental situations were performed with two different approaches. These are both based on the incompressible Navier-Stokes equations, one making use of an interface capturing technique, the other of a diffuse Cahn-Hilliard description. Comparisons between experimental and numerical results confirmed the reliability of the computational approaches in most situations but also highlighted the need for improvements to capture small-scale physical phenomena especially those related to film drainage. (author)

  15. Exploring Bubbles

    Science.gov (United States)

    O'Geary, Melissa A.

    Bubbles provide an enjoyable and festive medium through which to teach many concepts within the science topics of light, color, chemistry, force, air pressure, electricity, buoyancy, floating, density, among many others. In order to determine the nature of children's engagement within a museum setting and the learning opportunities of playing with bubbles, I went to a children's interactive museum located in a metropolitan city in the Northeastern part of the United States.

  16. Antigravitating bubbles

    CERN Document Server

    Barnaveli, A T; Barnaveli, Andro; Gogberashvili, Merab

    1995-01-01

    We investigate the gravitational behavior of spherical domain walls (bubbles) arising during the phase transitions in the early Universe. In the thin-wall approximation we show the existence of the new solution of Einstein equations with negative gravitational mass of bubbles and the reversed direction of time flow on the shell. This walls exhibit gravitational repulsion just as the planar walls are assumed to do. The equilibrium radius and critical mass of such objects are found for realistic models.

  17. Noise Bubbles

    OpenAIRE

    Mario Forni; Luca Gambetti; Marco Lippi; Luca Sala

    2014-01-01

    We introduce noisy information into a standard present value stock price model. Agents receive a noisy signal about the structural shock driving future dividend variations. The resulting equilibrium stock price includes a transitory component — the "noise bubble" — which can be responsible for boom and bust episodes unrelated to economic fundamentals. We propose a non-standard VAR procedure to estimate the structural shock and the "noise" shock, their impulse response functions and the bubble...

  18. Characterization of Bubbles in a Bubble Column by Image Analysis

    Czech Academy of Sciences Publication Activity Database

    Freitas, C.; Amaral, A. E.; Fialová, Marie; Ferreira, E. C.; Zahradník, Jindřich; Teixeira, J. A.

    Praha : Process Engineering Publisher, 2000. s. 136. ISBN 80-86059-30-8. [International Congress of Chemical and Process Engineering CHISA 2000 /14./. 27.08.2000-31.08.2000, Praha] Grant ostatní: INCO-COPERNICUS(XE) ERB IC15-CT98-0904 Institutional research plan: CEZ:AV0Z4072921 Subject RIV: CI - Industrial Chemistry, Chemical Engineering

  19. Computational and Experimental Study of Bubble Size in Bubble Columns

    DEFF Research Database (Denmark)

    Hansen, Rolf

    I denne afhandling præsenteres en Eulerisk tofaset numerisk fluiddynamik model til modellering af boblekolonner. Modellen kan beregne boblestørrelse ved brug af en grænsearealskoncentrationsligning (IACE), der er koblet til den spredte fase som en skalær transportligning. IACEmodellen kan beregne...

  20. Bubbling away

    International Nuclear Information System (INIS)

    Bubble chambers may have almost vanished from the front line of physics research, but the vivid memory of their intricate and sometimes beautiful patterns of particle tracks lives on, and has greatly influenced the computer graphics of track reconstruction in today's big experiments. 'Seeing' an interaction makes it more understandable. Bubble chambers, with their big collaborations of physicists from many widely scattered research institutes, started another ball rolling. The groups formed are even now only surpassed in size by the big collaborations working on today's major detectors at colliding beam machines. From 14-16 July, about 130 physicists gathered at CERN to commemorate the 40th anniversary of the invention of the bubble chamber by Donald Glaser. The meeting, organized by Derek C. Colley from Birmingham, gave a comprehensive overview of bubble chamber contributions to physics, their challenging technology, and the usefulness of bubble chamber photographs in education, both for physics and the public at large. After opening remarks by CERN Director Carlo Rubbia, Donald Glaser began with a brief review of the work which led to his invention - there was much more to it than idly watching beer bubbles rise up the wall of the glass - before turning to his present line of research, biophysics, also very visually oriented

  1. Methods for eluting radiocesium from zeolite ion exchange material in a column in the TMI-2 reactor containment building

    International Nuclear Information System (INIS)

    Two alternative procedures were evaluated at Oak Ridge National Laboratory for potential use in eluting the radiocesium from Linde Ionsiv IE-95 zeolite in the pushcart ion exchange column in the TMI-2 containment building. The elution mechanism was iosotopic exchange of the radiocesium with stable cesium. Small zeolite ion exchange columns that had been loaded during ORNL tests of the Submerged Demineralizer System (SDS) flowsheet were eluted during these tests. One column was eluted using 0.25 M CsNO3, and a second column was eluted using 0.25 M CsH2BO3. Both eluent solutions were effective for removing the cesium. The 0.25 CsNO3 eluent removed approx. 91% of the 137Cs in 20 bed volumes and approx. 92% in 37.5 bed volumes. The 0.25 M CsH2BO3 eluent removed approx. 82% of the 137Cs in 20 bed volumes and approx. 85% in 40 bed volumes. In both cases, the radiation levels on the columns were reduced by a factor of approx. 30

  2. EURACOS II facility in the modified thermal column of the TRIGA Mark II reactor at the University of Pavia LENA Laboratory

    International Nuclear Information System (INIS)

    The EURACOS II (Enriched Uranium Converter Source) project foresees the installation of an U--Al alloy converter plate at the end of the thermal column in the Pavia University LENA reactor. The incident thermal flux on the 5 Kg of 235U generates a fast neutron source whose power is 0.4 kW. The fast flux near the center exceeds 109 neutrons/cm2-sec. The fission plate is cooled by a forced air flow of 500 m3/h; the use of air instead of water reduces to a minimum the initial spectrum deformation of source neutrons. An irradiation chamber of 3.75 x 1.5 x 1.8 m3 is placed in front of the source and contains the mock-up under investigation. The facility is principally intended for benchmark-and mock-up-experiments in the reactor shielding field, but irradiations to different types and materials not directly related to shielding can be extended. The modification of the TRIGA thermal column, the characteristics of the EURACOS II facility, and the experiments now in preparation are described. The source intensity allows the study of neutron attenuation factor of 105 for fast, and 108 for thermal neutrons. The neutron spectra are investigated with the sandwich technique in the epithermal range, and with threshold detectors, organic and telescopic spectrometers in the fast energy range. (U.S.)

  3. Design of an Extractive Distillation Column for the Environmentally Benign Separation of Zirconium and Hafnium Tetrachloride for Nuclear Power Reactor Applications

    Directory of Open Access Journals (Sweden)

    Le Quang Minh

    2015-09-01

    Full Text Available Nuclear power with strengthened safety regulations continues to be used as an important resource in the world for managing atmospheric greenhouse gases and associated climate change. This study examined the environmentally benign separation of zirconium tetrachloride (ZrCl4 and hafnium tetrachloride (HfCl4 for nuclear power reactor applications through extractive distillation using a NaCl-KCl molten salt mixture. The vapor–liquid equilibrium behavior of ZrCl4 and HfCl4 over the molten salt system was correlated with Raoult’s law. The molten salt-based extractive distillation column was designed optimally using a rigorous commercial simulator for the feasible separation of ZrCl4 and HfCl4. The molten salt-based extractive distillation approach has many potential advantages for the commercial separation of ZrCl4 and HfCl4 compared to the conventional distillation because of its milder temperatures and pressure conditions, smaller number of required separation trays in the column, and lower energy requirement for separation, while still taking the advantage of environmentally benign feature by distillation. A heat-pump-assisted configuration was also explored to improve the energy efficiency of the extractive distillation process. The proposed enhanced configuration reduced the energy requirement drastically. Extractive distillation can be a promising option competing with the existing extraction-based separation process for zirconium purification for nuclear power reactor applications.

  4. Computational Modeling of Multiphase Reactors.

    Science.gov (United States)

    Joshi, J B; Nandakumar, K

    2015-01-01

    Multiphase reactors are very common in chemical industry, and numerous review articles exist that are focused on types of reactors, such as bubble columns, trickle beds, fluid catalytic beds, etc. Currently, there is a high degree of empiricism in the design process of such reactors owing to the complexity of coupled flow and reaction mechanisms. Hence, we focus on synthesizing recent advances in computational and experimental techniques that will enable future designs of such reactors in a more rational manner by exploring a large design space with high-fidelity models (computational fluid dynamics and computational chemistry models) that are validated with high-fidelity measurements (tomography and other detailed spatial measurements) to provide a high degree of rigor. Understanding the spatial distributions of dispersed phases and their interaction during scale up are key challenges that were traditionally addressed through pilot scale experiments, but now can be addressed through advanced modeling. PMID:26134737

  5. Bubbling Threat

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    The shift of China’s monetary policy stance from "moderately loose" to "prudent" in 2011 indicates curbing inflation and asset bubbles have become the Central Government’s top priority. But is China’s bubble problem short-term or long-term? Is it only monetary or related to economic structure? Is it the cause of China’s economic imbalance or the result? And what kind of deep-rooted problems in the macro economy does it reflect? All these questions call for deep thought,said Zhang Monan,a

  6. Continuous enzymatic biodiesel production from coconut oil in two-stage packed-bed reactor incorporating an extracting column to remove glycerol formed as by-product.

    Science.gov (United States)

    Costa E Silva, William; Freitas, Larissa; Oliveira, Pedro C; de Castro, Heizir F

    2016-10-01

    The transesterification of coconut oil with ethanol catalyzed by Burkholderia cepacia lipase immobilized on polysiloxane-polyvinyl alcohol was performed in a continuous flow. The experimental design consisted of a two-stage packed-bed reactor incorporating a column with cationic resin (Lewatit GF 202) to remove the glycerol formed as by-product and the reactor performance was quantified for three different flow rates corresponding to space-times from 10 to 14 h. The influence of space-time on the ethyl ester (FAEE) concentrations, yields and productivities was determined. The reactor operation was demonstrated for space-time of 14 h attaining FAEE concentrations of 58.5 ± 0.87 wt%, FAEE yields of 97.3 ± 1.9 % and productivities of 41.6  ± 1.0 mgester g medium (-1)  h(-1). Biodiesel purified samples showed average kinematic viscosity values of 5.5 ± 0.3 mm(2) s(-1) that meet the criteria established by the American National Standard ASTM (D6751). The immobilized lipase was found to be stable regarding its morphological and catalytic characteristics, showing half-life time (t 1/2) around 1540 h. The continuous packed-bed reactor connected in series with simultaneous glycerol removal has a great potential to attain high level of transesterification yields, raising biodiesel productivity. PMID:27277745

  7. Test on steam bubble behavior, (4)

    International Nuclear Information System (INIS)

    The experiment simulating the behavior of large steam bubbles generated at the time of core collapse accident was carried out with water, and the method of forecasting the vanishing behavior of large steam bubbles was examined. The results are reported in this paper. First, the reference to the literatures, the analysis with FTAC code and the thermodynamic examination were performed. In the evaluation of the transfer of radioactive substances to the outside of reactors at the time of hypothetic core collapse accident in fast reactors, it is important to grasp the behavior of CDA (core disruptive accident) bubbles. The radius of these bubbles was estimated to be several meter, and it was clarified that the incompressible gas in the bubbles exerted large influence on the vanishing behavior of the bubbles. Using incompressible gas and the system simulating the internal structure of a reactor, experiment was carried out, and the change of shape and the rising behavior of large bubbles were examined. Also the experiment using the mixture of steam and incompressible gas was carried out in a warm water tank, and the data on the effect of incompressible gas to obstruct the condensation of bubbles were obtained. (Kako, I.)

  8. Biogas quality upgrade by simultaneous removal of CO2 and H2S in a packed column reactor

    International Nuclear Information System (INIS)

    Biogas from anaerobic digestion of biological wastes is a renewable energy resource. It has been used to provide heat, shaft power and electricity. Typical biogas contains 50-65% methane (CH4), 30-45% carbon dioxide (CO2), moisture and traces of hydrogen sulphide (H2S). Presence of CO2 and H2S in biogas affects engine performance adversely. Reducing CO2 and H2S content will significantly improve quality of biogas. In this work, a method for biogas scrubbing and CH4 enrichment is presented. Chemical absorption of CO2 and H2S by aqueous solutions in a packed column was experimentally investigated. The aqueous solutions employed were sodium hydroxide (NaOH), calcium hydroxide (Ca(OH)2) and mono-ethanolamine (MEA). Liquid solvents were circulated through the column, contacting the biogas in countercurrent flow. Absorption characteristics were examined. Test results revealed that the aqueous solutions used were effective in reacting with CO2 in biogas (over 90% removal efficiency), creating CH4 enriched fuel. H2S was removed to below the detection limit. Absorption capability was transient in nature. Saturation was reached in about 50 min for Ca(OH)2, and 100 min for NaOH and MEA, respectively. With regular replacement or regeneration of used solutions, upgraded biogas can be maintained. This technique proved to be promising in upgrading biogas quality.

  9. Characterization of the neutron flux in the Hohlraum of the thermal column of the TRIGA Mark III reactor of the ININ; Caracterizacion del flujo neutronico en el Hohlraum de la columna termica del reactor TRIGA Mark III del ININ

    Energy Technology Data Exchange (ETDEWEB)

    Delfin L, A.; Palacios, J.C.; Alonso, G. [ININ, 52045 Ocoyoacac, Estado de Mexico (Mexico)]. e-mail: adl@nuclear.inin.mx

    2006-07-01

    Knowing the magnitude of the neutron flux in the reactor irradiation facilities, is so much importance for the operation of the same one, like for the investigation developing. Particularly, knowing with certain precision the spectrum and the neutron flux in the different positions of irradiation of a reactor, it is essential for the evaluation of the results obtained for a certain irradiation experiment. The TRIGA Mark III reactor account with irradiation facilities designed to carry out experimentation, where the reactor is used like an intense neutron source and gamma radiation, what allows to make irradiations of samples or equipment in radiation fields with components and diverse levels in the different facilities, one of these irradiation facilities is the Thermal Column where the Hohlraum is. In this work it was carried out a characterization of the neutron flux inside the 'Hohlraum' of the irradiation facility Thermal Column of the TRIGA Mark III reactor of the Nuclear Center of Mexico to 1 MW of power. It was determined the sub cadmic neutron flux and the epi cadmic by means of the neutron activation technique of thin sheets of gold. The maps of the distribution of the neutron flux for both energy groups in three different positions inside the 'Hohlraum' are presented, these maps were obtained by means of the irradiation of undressed thin activation sheets of gold and covered with cadmium in arrangements of 10 x 12, located parallel to 11.5 cm, 40.5 cm and 70.5 cm to the internal wall of graphite of the installation in inverse address to the position of the reactor core. Starting from the obtained values of neutron flux it was found that, for the same position of the surface of irradiation of the experimental arrangement, the relative differences among the values of neutron flux can be of 80%, and that the differences among different positions of the irradiation surfaces can vary until in a one order of magnitude. (Author)

  10. Convection heat transfer anisotropy in a bubbling viscous pool-Application to molten core-concrete interaction

    International Nuclear Information System (INIS)

    In the absence of bubbling, natural convection in an internally heated pool is largely anisotropic. There are large heat transfers to the upper and lateral walls, while the heat transfer to the cooled lower surface is small. Bubbling is a well-known mean of increasing the heat transfer coefficients, especially at the lower wall. The heat transfer between an internally heated pool and its walls has been experimentally studied while air bubbles were produced through a grid drilled with holes installed at the lower interface. Sugar solutions have been used as simulant the high temperature corium melts that would be produced during molten core-concrete interaction with respect to [Deckwer, W.-D.,1992. Bubble Column Reactors. John Wiley and Sons, Chichester (English Translation)] heat transfer model. Without any gas bubbling, natural convection in the pool exhibits a large anisotropy with a small heat transfer to the bottom wall. This is due to the building of a thermal gradient through the pool height. Bubbling with superficial gas velocity as low as 1 mm/s is sufficient to destabilize these layers in water and homogenize the pool. For more viscous fluids, it has been possible to determine a threshold between these regimes

  11. Loop reactor staged with structured fibrous catalytic layers for liquid-phase hydrogenations

    OpenAIRE

    Kiwi-Minsker, L.; Joannet, E.; Renken, A.

    2004-01-01

    A novel concept of a recycle loop reactor is developed with structured filamentous catalysts integrated as trays in a staged bubble column. The reactor can be operated in batch or continuous mode. Woven fabrics of activated carbon fibers (ACF) were used as support for the Pd catalyst. The loop reactor was tested in the 2-butyne-1,4-diol hydrogenation showing selectivity up to 97% towards 2-butene-1,4-diol at conversions up to 80%. The reactor behavior was described quant. assuming an ideally ...

  12. Bubble drag reduction requires large bubbles

    CERN Document Server

    Verschoof, Ruben A; Sun, Chao; Lohse, Detlef

    2016-01-01

    In the maritime industry, the injection of air bubbles into the turbulent boundary layer under the ship hull is seen as one of the most promising techniques to reduce the overall fuel consumption. However, the exact mechanism behind bubble drag reduction is unknown. Here we show that bubble drag reduction in turbulent flow dramatically depends on the bubble size. By adding minute concentrations (6 ppm) of the surfactant Triton X-100 into otherwise completely unchanged strongly turbulent Taylor-Couette flow containing bubbles, we dramatically reduce the drag reduction from more than 40% to about 4%, corresponding to the trivial effect of the bubbles on the density and viscosity of the liquid. The reason for this striking behavior is that the addition of surfactants prevents bubble coalescence, leading to much smaller bubbles. Our result demonstrates that bubble deformability is crucial for bubble drag reduction in turbulent flow and opens the door for an optimization of the process.

  13. Gas bubbling cleaning method

    International Nuclear Information System (INIS)

    The present invention concerns a gas bubbling cleaning method for objects to be cleaned having complicate shapes such as reactor equipments. For instance, air is used as the gas, while water is used as the cleaning fluid. A jetting air is jetted out to an object to be cleaned from an air bubbling nozzle disposed below the object. This constitutes air/water two phase flow near the object to be cleaned, to generate a three dimensional circulating flow. The distance between the inner wall surface of a cleaning vessel and the object to be cleaned is set to greater than 5 mm, and the ratio between the air flow rate and the horizontal cross section of the cleaning vessel is set to 0.1 to 0.4m/sec. This enables to enter an appropriate amount of bubbles to the air at the inside of the object to be cleaned having a complicate shape. Accordingly, deposits adhered to the inside of the object to be cleaned can be eliminated and cleaned effectively. (I.N.)

  14. Attachment of Acidithiobacillus ferrooxidans and Leptospirillum ferriphilum cultured under varying conditions to pyrite, chalcopyrite, low-grade ore and quartz in a packed column reactor.

    Science.gov (United States)

    Africa, Cindy-Jade; van Hille, Robert P; Harrison, Susan T L

    2013-02-01

    The attachment of Acidithiobacillus ferrooxidans and Leptospirillum ferriphilum spp. grown on ferrous medium or adapted to a pyrite mineral concentrate to four mineral substrata, namely, chalcopyrite and pyrite concentrates, a low-grade chalcopyrite ore (0.5 wt%) and quartzite, was investigated. The quartzite represented a typical gangue mineral and served as a control. The attachment studies were carried out in a novel particle-coated column reactor. The saturated reactor containing glass beads, which were coated with fine mineral concentrates, provided a quantifiable surface area of mineral concentrate and maintained good fluid flow. A. ferrooxidans and Leptospirillum spp. had similar attachment characteristics. Enhanced attachment efficiency occurred with bacteria grown on sulphide minerals relative to those grown on ferrous sulphate in an ore-free environment. Selective attachment to sulphide minerals relative to gangue materials occurred, with mineral adapted cultures attaching to the minerals more efficiently than ferrous grown cultures. Mineral-adapted cultures showed highest levels of attachment to pyrite (74% and 79% attachment for A. ferrooxidans and L. ferriphilum, respectively). This was followed by attachment of mineral-adapted cultures to chalcopyrite (63% and 58% for A. ferrooxidans and L. ferriphilum, respectively). A. ferrooxidans and L. ferriphilum exhibited lower levels of attachment to low-grade ore and quartz relative to the sulphide minerals. PMID:22410741

  15. Dose estimation in B16 tumour bearing mice for future irradiation in the thermal column of the TRIGA reactor after B/Gd/LDL adduct infusion

    Energy Technology Data Exchange (ETDEWEB)

    Protti, N., E-mail: nicoletta.protti@pv.infn.it [University of Pavia, Department of Nuclear and Theoretical Physics, via Bassi 6, 27100 Pavia (Italy)] [National Institute of Nuclear Physics (INFN) Section of Pavia, via Bassi 6, 27100 Pavia (Italy); Ballarini, F.; Bortolussi, S. [University of Pavia, Department of Nuclear and Theoretical Physics, via Bassi 6, 27100 Pavia (Italy)] [National Institute of Nuclear Physics (INFN) Section of Pavia, via Bassi 6, 27100 Pavia (Italy); Bruschi, P. [University of Pavia, Department of Nuclear and Theoretical Physics, via Bassi 6, 27100 Pavia (Italy); Stella, S. [University of Pavia, Department of Nuclear and Theoretical Physics, via Bassi 6, 27100 Pavia (Italy)] [National Institute of Nuclear Physics (INFN) Section of Pavia, via Bassi 6, 27100 Pavia (Italy); Geninatti, S.; Alberti, D.; Aime, S. [University of Torino, Chemistry Department, via Nizza 52, 10126 Torino (Italy); Altieri, S. [University of Pavia, Department of Nuclear and Theoretical Physics, via Bassi 6, 27100 Pavia (Italy)] [National Institute of Nuclear Physics (INFN) Section of Pavia, via Bassi 6, 27100 Pavia (Italy)

    2011-12-15

    To test the efficacy of a new {sup 10}B-vector compound, the B/Gd/LDL adduct synthesised at Torino University, in vivo irradiations of murine tumours are in progress at the TRIGA Mark II reactor of the Pavia University. A localised B16 melanoma tumour is generated in C57BL/6 mice and subsequently infused with the adduct. During the irradiation, the mouse will be put in a shield to protect the whole body except the tumour in the back-neck area. To optimise the treatment set-up, MCNP simulations were performed. A very simplified mouse model was built using MCNP geometry capabilities, as well as the geometry of the shield made of 99% {sup 10}B enriched boric acid. A hole in the shield is foreseen in correspondence of the back-neck region. Many configurations of the shield were tested in terms of neutron flux, dose distribution and mean induced activity in the tumour region and in the radiosensitive organs of the mouse. In the final set-up, up to five mice can be treated simultaneously in the reactor thermal column and the neutron fluence in the tumour region for 10 min of irradiation is of about 5 Multiplication-Sign 10{sup 12} cm{sup -2}.

  16. Dose estimation in B16 tumour bearing mice for future irradiation in the thermal column of the TRIGA reactor after B/Gd/LDL adduct infusion.

    Science.gov (United States)

    Protti, N; Ballarini, F; Bortolussi, S; Bruschi, P; Stella, S; Geninatti, S; Alberti, D; Aime, S; Altieri, S

    2011-12-01

    To test the efficacy of a new (10)B-vector compound, the B/Gd/LDL adduct synthesised at Torino University, in vivo irradiations of murine tumours are in progress at the TRIGA Mark II reactor of the Pavia University. A localised B16 melanoma tumour is generated in C57BL/6 mice and subsequently infused with the adduct. During the irradiation, the mouse will be put in a shield to protect the whole body except the tumour in the back-neck area. To optimise the treatment set-up, MCNP simulations were performed. A very simplified mouse model was built using MCNP geometry capabilities, as well as the geometry of the shield made of 99% (10)B enriched boric acid. A hole in the shield is foreseen in correspondence of the back-neck region. Many configurations of the shield were tested in terms of neutron flux, dose distribution and mean induced activity in the tumour region and in the radiosensitive organs of the mouse. In the final set-up, up to five mice can be treated simultaneously in the reactor thermal column and the neutron fluence in the tumour region for 10 min of irradiation is of about 5×10(12) cm(-2). PMID:21459587

  17. Reactive transport of uranyl: fixation mode on silica and goethite; experiments in columns and closed reactors; simulations

    International Nuclear Information System (INIS)

    Uranium contaminated areas are found in mine waste disposal sites, former military areas, etc. The present study focuses on the identification or mechanisms which may lead contaminated soils to become a sudden potential threat to surface and ground waters. Mechanisms were studied on model material at two levels. On the molecular scale, the complexation of uranyl at trace metal concentrations was investigated with amorphous silica. Complexation is shown to occur via the formation of surface complexes, characterised by different time-resolved laser-induced luminescence spectra and life times and stoichiometry. On the macro-scale the transport behaviour of uranyl in a cristobalite-goethite-carbonate-uranyl system was investigated with laboratory column and batch experiments. Uranium mobility was found to be controlled by the interaction between physical transport and a reversible, rate-controlled, fixation reaction. Sorption was shown to be an ensemble of competing solution and surface complexation reactions, leading to an apparent non-linear (Langmuir-like) adsorption isotherm. Finally the impact of a sudden change in background geochemistry was studied. Conditions leading to a dramatic mobilization of uranium from mildly contaminated systems were experimentally identified. Maximal uranyl concentration are controlled by the total extractable uranyl in the system and limited by uranyl solubility. Evolution of the background geochemical conditions is thus an important part of contaminated sites risk assessment. (author)

  18. Fischer-Tropsch Slurry Reactor modeling

    Energy Technology Data Exchange (ETDEWEB)

    Soong, Y.; Gamwo, I.K.; Harke, F.W. [Pittsburgh Energy Technology Center, PA (United States)] [and others

    1995-12-31

    This paper reports experimental and theoretical results on hydrodynamic studies. The experiments were conducted in a hot-pressurized Slurry-Bubble Column Reactor (SBCR). It includes experimental results of Drakeol-10 oil/nitrogen/glass beads hydrodynamic study and the development of an ultrasonic technique for measuring solids concentration. A model to describe the flow behavior in reactors was developed. The hydrodynamic properties in a 10.16 cm diameter bubble column with a perforated-plate gas distributor were studied at pressures ranging from 0.1 to 1.36 MPa, and at temperatures from 20 to 200{degrees}C, using a dual hot-wire probe with nitrogen, glass beads, and Drakeol-10 oil as the gas, solid, and liquid phase, respectively. It was found that the addition of 20 oil wt% glass beads in the system has a slight effect on the average gas holdup and bubble size. A well-posed three-dimensional model for bed dynamics was developed from an ill-posed model. The new model has computed solid holdup distributions consistent with experimental observations with no artificial {open_quotes}fountain{close_quotes} as predicted by the earlier model. The model can be applied to a variety of multiphase flows of practical interest. An ultrasonic technique is being developed to measure solids concentration in a three-phase slurry reactor. Preliminary measurements have been made on slurries consisting of molten paraffin wax, glass beads, and nitrogen bubbles at 180 {degrees}C and 0.1 MPa. The data show that both the sound speed and attenuation are well-defined functions of both the solid and gas concentrations in the slurries. The results suggest possibilities to directly measure solids concentration during the operation of an autoclave reactor containing molten wax.

  19. Column flotation

    Energy Technology Data Exchange (ETDEWEB)

    Kohmuench, J.N.; Norrgran, D.A.; Luttrell, E.; Luttrell, G.H. [Virginia Tech. (United States)

    2008-04-15

    Over the last decade, column flotation has been recognised in the industry to be most efficient and economical means of recovering fine coal while maximizing product grade. When designed properly, flotation columns provide a high combustible recovery while maintaining a low product ash. The paper looks at the benefits of using column flotation for fine coal recovery. 2 refs., 5 figs.

  20. Free Surface Lattice Boltzmann with Enhanced Bubble Model

    CERN Document Server

    Anderl, Daniela; Rauh, Cornelia; Rüde, Ulrich; Delgado, Antonio

    2016-01-01

    This paper presents an enhancement to the free surface lattice Boltzmann method (FSLBM) for the simulation of bubbly flows including rupture and breakup of bubbles. The FSLBM uses a volume of fluid approach to reduce the problem of a liquid-gas two-phase flow to a single-phase free surface simulation. In bubbly flows compression effects leading to an increase or decrease of pressure in the suspended bubbles cannot be neglected. Therefore, the free surface simulation is augmented by a bubble model that supplies the missing information by tracking the topological changes of the free surface in the flow. The new model presented here is capable of handling the effects of bubble breakup and coalesce without causing a significant computational overhead. Thus, the enhanced bubble model extends the applicability of the FSLBM to a new range of practically relevant problems, like bubble formation and development in chemical reactors or foaming processes.

  1. Successive pretreatment and enzymatic saccharification of sugarcane bagasse in a packed bed flow-through column reactor aiming to support biorefineries.

    Science.gov (United States)

    Terán-Hilares, R; Reséndiz, A L; Martínez, R T; Silva, S S; Santos, J C

    2016-03-01

    A packed bed flow-through column reactor (PBFTCR) was used for pretreatment and subsequent enzymatic hydrolysis of sugarcane bagasse (SCB). Alkaline pretreatment was performed at 70°C for 4h with fresh 0.3M NaOH solution or with liquor recycled from a previous pretreatment batch. Scheffersomyces stipitis NRRL-Y7124 was used for fermentation of sugars released after enzymatic hydrolysis (20FPUg(-1) of dry SCB). The highest results for lignin removal were 61% and 52%, respectively, observed when using fresh NaOH or the first reuse of the liquor. About 50% of cellulosic and 57% of hemicellulosic fractions of pretreated SCBs were enzymatically hydrolyzed and the maximum ethanol production was 23.4gL(-1) (ethanol yield of 0.4gpgs(-1)), with near complete consumption of both pentoses and hexoses present in the hydrolysate during the fermentation. PBFTCR as a new alternative for SCB-biorefineries is presented, mainly considering its simple configuration and efficiency for operating with a high solid:liquid ratio. PMID:26720138

  2. Activity evaluation of 60Co, 137Cs, 152Eu, 154Eu, 14C and total β in graphite from the thermal column of Romanian TRIGA research reactor

    International Nuclear Information System (INIS)

    Several methods were investigated for identification and activity evaluation of 60Co, 137Cs, 152Eu, 154Eu, 14C and total β in graphite samples collected from the thermal column of Romanian research reactor. An ORTEC DIGIDART multichannel gamma spectrometer was used for measurement of 60Co, 137Cs, 152Eu and 154Eu. The main contribution to the radioactivity of graphite comes from 60Co, 152Eu and 154Eu. Combustion of graphite samples using a PerkinElmer sample oxidizer was utilized for total oxidizing of 14C to gaseous carbon dioxide. A TRI-CARB Packard liquid scintillation analyzer was used for 14C counting. The degree of 14C recovery in the analyzed standard samples was higher than 98%, and the 14C retention degree in the circuits of combustion system was less than 0.08%. To evaluation of total β activity in the irradiated graphite, the samples were measured using a proportional counter. The mean total β activity in the irradiated graphite samples was about 3000 Bq/g. (authors)

  3. Calculations of dose distributions in the lungs of a rat model irradiated in the thermal column of the TRIGA reactor in Pavia.

    Science.gov (United States)

    Protti, N; Bortolussi, S; Stella, S; Gadan, M A; De Bari, A; Ballarini, F; Bruschi, P; Ferrari, C; Clerici, A M; Zonta, C; Bakeine, J G; Dionigi, P; Zonta, A; Altieri, S

    2009-07-01

    To test the possibility to apply boron neutron capture therapy (BNCT) to lung tumors, some rats are planned to be irradiated in the thermal column of the TRIGA reactor of the University of Pavia. Before the irradiation, lung metastases will be induced in BDIX rats, which will be subsequently infused with boronophenylalanine (BPA). During the irradiation, the rats will be positioned in a box designed to shield the whole animal except the thorax area. In order to optimize the irradiation set-up and to design a suitable shielding box, a set of calculations were performed with the MCNP Monte Carlo transport code. A rat model was constructed using the MCNP geometry capabilities and was positioned in a box with walls filled with lithium carbonate. A window was opened in front of the lung region. Different shapes of the holder and of the window were tested and analyzed in terms of the dose distribution obtained in the lungs and of the dose absorbed by the radiosensitive organs in the rat. The best configuration of the holder ensures an almost uniform thermal neutron flux inside the lungs (Phi(max)/Phi(min)=1.5), an irradiation time about 10 min long, to deliver at least 40 Gy(w) to the tumor, a mean lung dose of 5.9+/-0.4 Gy(w), and doses absorbed by all the other healthy tissues below the tolerance limits. PMID:19406647

  4. Detail analysis of tritium permeation in the metal liquid channels of the regenerating sheaths of a fusion reactor in presence of helium bubbles; Analisis de detalle de la permeacion de tritio en los caneles de metal liquido de las envolturas regeneradoras de un reactor de fusion en presencia de burbujas de helio

    Energy Technology Data Exchange (ETDEWEB)

    Banet, L.; Mas de les Valls, E.; Sedano, L. A.

    2012-07-01

    Inside the channels of liquid metal of the fusion reactor regenerative wrappers, the possible existence of nucleated helium bubbles is not remote. Helium is formed joined the tritium in the escaped neutrons of plasma with lithium. The accumulation of helium in the contact surfaces, between the structure and ML, lead a reduction of heat transfer, at the same time a reduction in the permeation of tritium. The coexistence of three phases in touch: metal liquid, helium and structural material, makes the transport of heat and tritium in a complex phenomenon. To enrich tritium transport studies conducted in the past, there is now a detail analysis of the helium bubble environment adhered to the channel ML wall of a regenerative wrap. For the study we used a CFD tool development on free code OpenFOAM.

  5. Experimental investigation on bubble characteristics entrained by surface vortex

    International Nuclear Information System (INIS)

    The cover gas entrainment at the free surface of sodium coolant becomes one of the significant issues according to the compact sizing of reactor vessel in the latest reactor design. In the present study, some basic experiments for the gas entrainment due to the surface vortex were performed in order to obtain the fundamental knowledge about the entrained bubble size. Distributions of entrained bubble diameters in several experimental conditions were obtained from bubble images using an image processing technique. Velocity fields around vortices and surface dimple shapes (gas cores) due to surface vortices were measured to grasp those influences on bubble shapes. The result showed that mean equivalent diameters of bubbles were varied from 1.3 to 2.1 mm in the range of present experimental conditions. The bubble sizes were influenced by the thickness of gas core.

  6. Hydrodynamics of the continuously filtering slurry reactor. Influence of load of solids and particle size distribution.

    OpenAIRE

    Huizenga, P.; Kuipers, J.A.M.; Swaaij, van, W.P.M.

    1997-01-01

    Internal filtration in slurry bubble columns offers a possible solution to the filtration problems related to this reactor type. The applicability of the concept has already been demonstrated at full-scale for waste water treatment. Theoretical description of internal filtration is lacking, however. In previous work it was derived on basis of two different models, that in three-phase filtration solids concentration in the vicinity of the filter should uniquely depend on a single dimensionless...

  7. Fama on Bubbles

    DEFF Research Database (Denmark)

    Engsted, Tom

    2016-01-01

    While Eugene Fama has repeatedly expressed his discontent with the notion of an “irrational bubble,” he has never publicly expressed his opinion on “rational bubbles.” On empirical grounds Fama rejects bubbles by referring to the lack of reliable evidence that price declines are predictable....... However, this argument cannot be used to rule out rational bubbles because such bubbles do not necessarily imply return predictability, and return predictability of the kind documented by Fama does not rule out rational bubbles. On data samples that include the 1990s, there is evidence of an explosive...

  8. Fama on bubbles

    DEFF Research Database (Denmark)

    Engsted, Tom

    Eugene Fama has repeatedly expressed his discontent with the notion of an irrational bubble. However, he has never publicly expressed his opinion on rational bubbles. This is peculiar since such bubbles build naturally from the rational efficient markets paradigm that Fama strongly adheres to....... On empirical grounds Fama rejects bubbles by referring to the lack of reliable evidence that price declines are predictable. However, this argument cannot be used to rule out rational bubbles because such bubbles do not necessarily imply return predictability. On data samples that include the 1990s...

  9. Condensation-Induced Steam Bubble Collapse in a Pipeline

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Steam bubbles often occur in pipelines due to the pipeline structure or operational errors. The water hammer force induced by the steam bubble collapse is a hidden safety concern. This paper experimentally and numerically investigates the conditions for steam bubble formation and collapse. A series of video pictures taken in the laboratory show that steam bubbles form and collapse over several cycles. The pressure history of the steam bubbles is measured in conjunction with the pictures. In the experiment, the liquid column cavitated at the low pressures and then the cavities collapsed due to condensation causing high pressure pulses. The process was also simulated numerically. The results suggest that coolant pipeline design and operation must include procedures to avoid steam bubble formation.

  10. Soap Bubbles and Logic.

    Science.gov (United States)

    Levine, Shellie-helane; And Others

    1986-01-01

    Introduces questions and activities involving soap bubbles which provide students with experiences in prediction and logic. Examines commonly held false conceptions related to the shapes that bubbles take and provides correct explanations for the phenomenon. (ML)

  11. Preheating in Bubble Collision

    CERN Document Server

    Zhang, Jun

    2010-01-01

    In a landscape with metastable minima, the bubbles will inevitably nucleate. We show that when the bubbles collide, due to the dramatically oscillating of the field at the collision region, the energy deposited in the bubble walls can be efficiently released by the explosive production of the particles. In this sense, the collision of bubbles is actually high inelastic. The cosmological implications of this result are discussed.

  12. CFD - Facilitated Prognosis of Bubble Bed Bioreactor Performance Based on Bubble Swarms Oscillation Analysis

    Czech Academy of Sciences Publication Activity Database

    Vlaev, S. D.; Staykov, P.; Fialová, Marie

    2009-01-01

    Roč. 23, č. 4 (2009), s. 513-518. ISSN 0352-9568 R&D Projects: GA ČR GA104/07/1110 Institutional research plan: CEZ:AV0Z40720504 Keywords : bubble column bioreactor * gas holdup * cfd Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 0.387, year: 2009

  13. Fluid dynamics of bubbles in liquid

    Directory of Open Access Journals (Sweden)

    SCHEID C.M.

    1999-01-01

    Full Text Available Results gathered from the literature on the dynamics of bubbles in liquid are correlated by means of a formulation traditionally employed to describe the dynamics of isometric solid particles. It is assumed that the shape of the bubble depends, by means of the Eotvos number, on its diameter and on the gas-liquid surface tension. The analysis reported herein includes the dynamics of the isolated bubble along with wall and concentration effects. However, the effects of gas circulation in the bubble, which result in terminal velocities higher than those of a rigid sphere, are not being considered. A limited number of experimental points are obtained employing a modified version of the Mariotte flask which permits the precise measure of bubble volume. A classic bubble column is also employed in order to measure gas holdup in the continuous phase. Experiments were carried out employing air, with distilled water, potable water, water with variable amounts of surfactant and glycerin as the liquid phase.

  14. Bubbles tomorrow and bubbles yesterday, but never bubbles today?

    OpenAIRE

    Williams, John C.

    2013-01-01

    Standard asset price models have generally failed to detect bubbles, with enormous costs to the economy. Economists are now creating promising new models that account for bubbles by relaxing the assumption of rational expectations and allowing people’s decisions to be driven by their perceptions of what the future may hold. ; This letter is adapted from a presentation by the president and CEO of the Federal Reserve Bank of San Francisco to the National Association for Business Economics in Sa...

  15. Particle-bubble aggregate stability on static bubble generated by single nozzle on flotation process

    Science.gov (United States)

    Warjito, Harinaldi, Setyantono, Manus; Siregar, Sahala D.

    2016-06-01

    There are three sub-processes on flotation. These processes are intervening liquid film into critical thickness, rupture of liquid film forming three phase contact line, and expansion three phase contact line forming aggregate stability. Aggregate stability factor contribute to determine flotation efficiency. Aggregate stability has some important factors such as reagent and particle geometry. This research focussed on to understand effect of particle geometry to aggregate stability. Experimental setup consists of 9 x 9 x26 cm flotation column made of glass, bubble generator, particle feeding system, and high speed video camera. Bubble generator made from single nozzle with 0.3 mm diameter attached to programmable syringe pump. Particle feeding system made of pipette. Particle used in this research is taken from open pit Grasberg in Timika, Papua. Particle has sub-angular geometry and its size varies from 38 to 300 µm. Bubble-particle interaction are recorded using high speed video camera. Recordings from high speed video camera analyzed using image processing software. Experiment result shows that aggregate particle-bubble and induction time depends on particle size. Small particle (38-106 µm) has long induction time and able to rupture liquid film and also forming three phase contact line. Big particle (150-300 µm) has short induction time, so it unable to attach with bubble easily. This phenomenon is caused by apparent gravity work on particle-bubble interaction. Apparent gravity worked during particle sliding on bubble surface experience increase and reached its maximum magnitude at bubble equator. After particle passed bubble equator, apparent gravity force experience decrease. In conclusion particle size from 38-300 µm can form stable aggregate if particle attached with bubble in certain condition.

  16. Density of radiolytic gas bubbles in polymethyl methacrylate

    Science.gov (United States)

    Makkonen, T.; Tiainen, O. J. A.; Valkiainen, M.; Winberg, M.

    The density of the radiolytic gas bubbles in irradiated polymethyl methacrylate was measured during subsequent heat treatment as a function of radiation dose. The samples were irradiated in the core of the Triga Mark II reactor in Otaniemi. After the irradiation periods the samples were heat treated at 393 K. The number of the bubbles could be explained by a thermal activation model. The bubbles are born in material inhomogeneities and the threshold dose for the bubble initiation was about 25 Mrad for the heat treatment at 393 K under the atmospheric pressure.

  17. Separation of Oil from Wastewater by Column Flotation

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A new type of device, a dissolved-air flotation column, was developed for separation of oily wastewater.The unique design idea of the dissolved-air flotation column is the combined use of dissolved-air flotation and column flotation.The dissolved air release occurred within the column separation system.As a potential application the column was investigated for its performance in separating emulsified oil droplets in oily wastewater.A high separation efficiency was obtained in a series of tests.The aeration performance of the bubble generator used in the dissolved-air flotation column was also studied in particular.

  18. Bubble Manipulation by Self Organization of Bubbles inside Ultrasonic Wave

    Science.gov (United States)

    Yamakoshi, Yoshiki; Koganezawa, Masato

    2005-06-01

    Microbubble manipulation using ultrasonic waves is a promising technology in the fields of future medicine and biotechnology. For example, it is considered that bubble trapping using ultrasonic waves may play an important role in drug or gene delivery systems in order to trap the drugs or genes in the diseased tissue. Usually, when bubbles are designed so that they carry payloads, such as drug or gene, they tend to be harder than free bubbles. These hard bubbles receive a small acoustic radiation force, which is not sufficient for bubble manipulation. In this paper, a novel method of microbubble manipulation using ultrasonic waves is proposed. This method uses seed bubbles in order to manipulate target bubbles. When the seed bubbles are introduced into the ultrasonic wave field, they start to oscillate to produce a bubble aggregation of a certain size. Then the target bubbles are introduced, the target bubbles attach around the seed bubbles producing a bubble mass with bilayers (inner layer: seed bubbles, outer layer: target bubbles). The target bubbles are manipulated as a bilayered bubble mass. Basic experiments are carried out using polyvinyl chloride (PVC) shell bubbles. No target bubbles are trapped when only the target bubbles are introduced. However, they are trapped if the seed bubbles are introduced in advance.

  19. Column: lef

    NARCIS (Netherlands)

    Reep, Frans van der

    2012-01-01

    1e alinea column: Ook in je beleggingsbeslissingen is het voor echte performance wellicht tijd om eens voorbij best practices (dan word je namelijk hoogstens tweede) te kijken naar next practices. Als je op zeker speelt, verdien je weinig geld. Want anderen gingen je al voor. Maar kun je nog meer op

  20. Nanoemulsions obtained via bubble bursting at a compound interface

    CERN Document Server

    Feng, Jie; Vigolo, Daniele; Arnaudov, Luben N; Stoyanov, Simeon D; Gurkov, Theodor D; Tsutsumanova, Gichka G; Stone, Howard A

    2013-01-01

    The bursting of bubbles at an air/liquid interface is a familiar occurrence important to foam stability, cell cultures in bioreactors and mass transfer between the sea and atmosphere. Here we document the hitherto unreported formation and dispersal into the water column of submicrometre oil droplets following bubble bursting at a compound air/oil/water-with-surfactant interface. We show that dispersal results from the detachment of an oil spray from the bottom of the bubble towards water during bubble collapse. We provide evidence that droplet size is selected by physicochemical interactions between oil molecules and the surfactants rather than by hydrodynamic effects. We illustrate the unrecognized role that this dispersal mechanism may play in the fate of the sea surface micro-layer and of pollutant spills by dispersing petroleum in the water column. Finally, our system provides an energy-efficient route, with potential upscalability and wide applicability, for applications in drug delivery, food production...

  1. Luminescence from Tube-Arrest Bubbles in Pure Glycerin

    Institute of Scientific and Technical Information of China (English)

    陈岐岱; 王龙

    2004-01-01

    Single transient cavitation bubble with luminescence has been generated in pure glycerin by using the ‘tube arrest'method. The analyses of high-speed photograph and light emission data suggest that the light emission would be a single bubble sonoluminescence. The luminescence pulse width is observed to wry from sub-nanosecond to about 30 ns. The width and intensity of luminescence pulses increases with the height of the liquid column height and decreases with the liquid temperature.

  2. Bubble transport in subcooled flow boiling

    Science.gov (United States)

    Owoeye, Eyitayo James

    Understanding the behavior of bubbles in subcooled flow boiling is important for optimum design and safety in several industrial applications. Bubble dynamics involve a complex combination of multiphase flow, heat transfer, and turbulence. When a vapor bubble is nucleated on a vertical heated wall, it typically slides and grows along the wall until it detaches into the bulk liquid. The bubble transfers heat from the wall into the subcooled liquid during this process. Effective control of this transport phenomenon is important for nuclear reactor cooling and requires the study of interfacial heat and mass transfer in a turbulent flow. Three approaches are commonly used in computational analysis of two-phase flow: Eulerian-Lagrangian, Eulerian-Eulerian, and interface tracking methods. The Eulerian- Lagrangian model assumes a spherical non-deformable bubble in a homogeneous domain. The Eulerian-Eulerian model solves separate conservation equations for each phase using averaging and closure laws. The interface tracking method solves a single set of conservation equations with the interfacial properties computed from the properties of both phases. It is less computationally expensive and does not require empirical relations at the fluid interface. Among the most established interface tracking techniques is the volume-of-fluid (VOF) method. VOF is accurate, conserves mass, captures topology changes, and permits sharp interfaces. This work involves the behavior of vapor bubbles in upward subcooled flow boiling. Both laminar and turbulent flow conditions are considered with corresponding pipe Reynolds number of 0 -- 410,000 using a large eddy simulation (LES) turbulence model and VOF interface tracking method. The study was performed at operating conditions that cover those of boiling water reactors (BWR) and pressurized water reactors (PWR). The analysis focused on the life cycle of vapor bubble after departing from its nucleation site, i.e. growth, slide, lift-off, rise

  3. The condensation of sodium vapour bubbles

    International Nuclear Information System (INIS)

    This is a preliminary analytic study of the violent collapse of a vapour bubble by condensation in cold liquid. A calculation method is described and is applied to the condensation of sodium vapour bubbles such as might be formed in an overheating accident in a fast reactor. The method is not satisfactory, and a more thorough study of the problem is needed, but these preliminary results suggest that while the violent collapse is unlikely to do much mechanical damage, it produces a considerable amount of acoustic energy. (author)

  4. Tribonucleation of bubbles

    CERN Document Server

    Wildeman, Sander; Sun, Chao; Lohse, Detlef; Prosperetti, Andrea

    2016-01-01

    We report on the nucleation of bubbles on solids that are gently rubbed against each other in a liquid. The phenomenon is found to depend strongly on the material and roughness of the solid surfaces. For a given surface, temperature, and gas content, a trail of growing bubbles is observed if the rubbing force and velocity exceed a certain threshold. Direct observation through a transparent solid shows that each bubble in the trail results from the early coalescence of several microscopic bubbles, themselves detaching from microscopic gas pockets forming between the solids. From a detailed study of the wear tracks, with atomic force and scanning electron microscopy imaging, we conclude that these microscopic gas pockets originate from a local fracturing of the surface asperities, possibly enhanced by chemical reactions at the freshly created surfaces. Our findings will be useful either for preventing undesired bubble formation or, on the contrary, for "writing with bubbles," i.e., creating controlled patterns ...

  5. Nanoemulsions obtained via bubble-bursting at a compound interface

    Science.gov (United States)

    Feng, Jie; Roché, Matthieu; Vigolo, Daniele; Arnaudov, Luben N.; Stoyanov, Simeon D.; Gurkov, Theodor D.; Tsutsumanova, Gichka G.; Stone, Howard A.

    2014-08-01

    Bursting of bubbles at an air/liquid interface is a familiar occurrence relevant to foam stability, cell cultures in bioreactors and ocean-atmosphere mass transfer. In the latter case, bubble-bursting leads to the dispersal of sea-water aerosols in the surrounding air. Here we show that bubbles bursting at a compound air/oil/water-with-surfactant interface can disperse submicrometre oil droplets in water. Dispersal results from the detachment of an oil spray from the bottom of the bubble towards water during bubble collapse. We provide evidence that droplet size is selected by physicochemical interactions between oil molecules and the surfactants rather than by hydrodynamics. We demonstrate the unrecognized role that this dispersal mechanism may play in the fate of the sea surface microlayer and of pollutant spills by dispersing petroleum in the water column. Finally, our system provides an energy-efficient route, with potential upscalability, for applications in drug delivery, food production and materials science.

  6. Bubbles and market crashes

    CERN Document Server

    Youssefmir, M; Hogg, T; Youssefmir, Michael; Huberman, Bernardo; Hogg, Tad

    1994-01-01

    We present a dynamical theory of asset price bubbles that exhibits the appearance of bubbles and their subsequent crashes. We show that when speculative trends dominate over fundamental beliefs, bubbles form, leading to the growth of asset prices away from their fundamental value. This growth makes the system increasingly susceptible to any exogenous shock, thus eventually precipitating a crash. We also present computer experiments which in their aggregate behavior confirm the predictions of the theory.

  7. Inexperienced Investors and Bubbles

    OpenAIRE

    Robin Greenwood; Stefan Nagel

    2008-01-01

    We use mutual fund manager data from the technology bubble to examine the hypothesis that inexperienced investors play a role in the formation of asset price bubbles. Using age as a proxy for managers' investment experience, we find that around the peak of the technology bubble, mutual funds run by younger managers are more heavily invested in technology stocks, relative to their style benchmarks, than their older colleagues. Furthermore, young managers, but not old managers, exhibit trend-ch...

  8. Sonoluminescence and bubble fusion

    OpenAIRE

    Arakeri, Vijay H

    2003-01-01

    Sonoluminescence (SL), the phenomenon of light emission from nonlinear motion of a gas bubble, involves an extreme degree of energy focusing. The conditions within the bubble during the last stages of the nearly catastrophic implosion are thought to parallel the efforts aimed at developing inertial confinement fusion. A limited review on the topic of SL and its possible connection to bubble nuclear fusion is presented here. The emphasis is on looking for a link between the various forms o...

  9. Contactless Inductive Bubble Detection in a Liquid Metal Flow.

    Science.gov (United States)

    Gundrum, Thomas; Büttner, Philipp; Dekdouk, Bachir; Peyton, Anthony; Wondrak, Thomas; Galindo, Vladimir; Eckert, Sven

    2016-01-01

    The detection of bubbles in liquid metals is important for many technical applications. The opaqueness and the high temperature of liquid metals set high demands on the measurement system. The high electrical conductivity of the liquid metal can be exploited for contactless methods based on electromagnetic induction. We will present a measurement system which consists of one excitation coil and a pickup coil system on the opposite sides of the pipe. With this sensor we were able to detect bubbles in a sodium flow inside a stainless steel pipe and bubbles in a column filled with a liquid Gallium alloy. PMID:26751444

  10. Sonochemistry and bubble dynamics.

    Science.gov (United States)

    Mettin, Robert; Cairós, Carlos; Troia, Adriano

    2015-07-01

    The details of bubble behaviour in chemically active cavitation are still not sufficiently well understood. Here we report on experimental high-speed observations of acoustically driven single-bubble and few-bubble systems with the aim of clarification of the connection of their dynamics with chemical activity. Our experiment realises the sonochemical isomerization reaction of maleic acid to fumaric acid, mediated by bromine radicals, in a bubble trap set-up. The main result is that the reaction product can only be observed in a parameter regime where a small bubble cluster occurs, while a single trapped bubble stays passive. Evaluations of individual bubble dynamics for both cases are given in form of radius-time data and numerical fits to a bubble model. A conclusion is that a sufficiently strong collapse has to be accompanied by non-spherical bubble dynamics for the reaction to occur, and that the reason appears to be an efficient mixing of liquid and gas phase. This finding corroborates previous observations and literature reports on high liquid phase sonochemical activity under distinct parameter conditions than strong sonoluminescence emissions. PMID:25194210

  11. Bubble and drop interfaces

    CERN Document Server

    Miller

    2011-01-01

    The book aims at describing the most important experimental methods for characterizing liquid interfaces, such as drop profile analysis, bubble pressure and drop volume tensiometry, capillary pressure technique, and oscillating drops and bubbles. Besides the details of experimental set ups, also the underlying theoretical basis is presented in detail. In addition, a number of applications based on drops and bubbles is discussed, such as rising bubbles and the very complex process of flotation. Also wetting, characterized by the dynamics of advancing contact angles is discussed critically. Spec

  12. Prospects for bubble fusion

    Energy Technology Data Exchange (ETDEWEB)

    Nigmatulin, R.I. [Tyumen Institute of Mechanics of Multiphase Systems (TIMMS), Marx (Russian Federation); Lahey, R.T. Jr. [Rensselaer Polytechnic Institute, Troy, NY (United States)

    1995-09-01

    In this paper a new method for the realization of fusion energy is presented. This method is based on the superhigh compression of a gas bubble (deuterium or deuterium/thritium) in heavy water or another liquid. The superhigh compression of a gas bubble in a liquid is achieved through forced non-linear, non-periodic resonance oscillations using moderate amplitudes of forcing pressure. The key feature of this new method is a coordination of the forced liquid pressure change with the change of bubble volume. The corresponding regime of the bubble oscillation has been called {open_quotes}basketball dribbling (BD) regime{close_quotes}. The analytical solution describing this process for spherically symmetric bubble oscillations, neglecting dissipation and compressibility of the liquid, has been obtained. This solution shown no limitation on the supercompression of the bubble and the corresponding maximum temperature. The various dissipation mechanisms, including viscous, conductive and radiation heat losses have been considered. It is shown that in spite of these losses it is possible to achieve very high gas bubble temperatures. This because the time duration of the gas bubble supercompression becomes very short when increasing the intensity of compression, thus limiting the energy losses. Significantly, the calculated maximum gas temperatures have shown that nuclear fusion may be possible. First estimations of the affect of liquid compressibility have been made to determine possible limitations on gas bubble compression. The next step will be to investigate the role of interfacial instability and breaking down of the bubble, shock wave phenomena around and in the bubble and mutual diffusion of the gas and the liquid.

  13. Estimation of the lifetime of small helium bubbles near tungsten surfaces - A methodological study

    Science.gov (United States)

    Cui, Jiechao; Wu, Zhangwen; Hou, Qing

    2016-09-01

    Under low energy and high flux/fluence irradiation of helium (He) atoms, the formation and bursting of He bubbles on tungsten (W) surfaces play important roles in the morphological evolution of component surfaces in fusion reactors. Microscopically, the bursting of He bubbles is a stochastic process, and He bubbles have statistically average lifetimes. In the present paper, a molecular dynamics-based method was developed to extract, for the first time, the lifetime of He bubbles near tungsten surfaces. It was found that He bubble bursting can be treated as an activated event. Its frequency or, equivalently, the average lifetime of bubbles follows the Arrhenius equation. For a given bubble size, the activation energy exhibits a good linear dependence with the depth, and the pre-exponential factor obeys the Meyer-Neldle rule. These results are useful for establishing a model in multi-scale simulations of the morphological evolution of component surfaces in fusion reactors.

  14. Understanding the bubbles

    DEFF Research Database (Denmark)

    Turcan, Romeo V.

    prospects of a new venture and intended outcomes of that new venture; the higher the residue, the higher the likelihood of the bubble emergence; as residue increases, the likelihood of bubble burst increases. One question that arises is whether one can manage the hype, hence the residue. In this, it is...

  15. Tribonucleation of bubbles

    NARCIS (Netherlands)

    Wildeman, Sander; Lhuissier, Henri; Sun, Chao; Lohse, Detlef; Prosperetti, Andrea

    2014-01-01

    We report on the nucleation of bubbles on solids that are gently rubbed against each other in a liquid. The phenomenon is found to depend strongly on the material and roughness of the solid surfaces. For a given surface, temperature, and gas content, a trail of growing bubbles is observed if the rub

  16. Bubbles in graphene

    DEFF Research Database (Denmark)

    Settnes, Mikkel; Power, Stephen; Lin, Jun;

    2015-01-01

    Strain-induced deformations in graphene are predicted to give rise to large pseudomagnetic fields. We examine theoretically the case of gas-inflated bubbles to determine whether signatures of such fields are present in the local density of states. Sharp-edged bubbles are found to induce Friedel...

  17. Reactors

    International Nuclear Information System (INIS)

    Purpose: To provide a spray cooling structure wherein the steam phase in a bwr reactor vessel can sufficiently be cooled and the upper cap and flanges in the vessel can be cooled rapidly which kept from direct contaction with cold water. Constitution: An apertured shielding is provided in parallel spaced apart from the inner wall surface at the upper portion of a reactor vessel equipped with a spray nozzle, and the lower end of the shielding and the inner wall of the vessel are closed to each other so as to store the cooling water. Upon spray cooling, cooling water jetting out from the nozzle cools the vapor phase in the vessel and then hits against the shielding. Then the cooling water mostly falls as it is, while partially enters through the apertures to the back of the shielding plate, abuts against stoppers and falls down. The stoppers are formed in an inverted L shape so that the spray water may not in direct contaction with the inner wall of the vessel. (Horiuchi, T.)

  18. Performance of the lift-pump with the lead-bismuth cooled fast reactor. Experimental study on bubble distribution and circulation flow rate

    International Nuclear Information System (INIS)

    Recently, the utilization of the lift pump is examined in a small reactor of the lead-bismuth eutectic cooling. Then, the experiments concerning about void behavior and performance of the lift pump in three kinds of risers (1124mm in height and inside diameters φ69.3mm, φ106.3mm, φ155.2mm) were performed by using lead bismuth eutectic. The main results are as follows: (1) The local void fraction varies in horizontal plane in case of the big diameter riser. (2) The lead-bismuth circulating flow rate evaluated by a present design method becomes lower than that of experiments in case of medium and small diameter risers. This design method can be used as an outline evaluating function for these cases, considering the evaluation accuracy of the pressure loss of the test section in the calculation. (3) In the big diameter riser, the present design method excessively evaluates the lead-bismuth circulating flow rate. It thought that the circulation head will not occur in the experiments such as a results of the present design method because the void rises biasing in horizontal plane in case of big diameter riser though the present method is one dimensional model. It is better to utilize a separator which can divides the riser into about 10cm diameter flow path and the void is fed uniformly distributed to each paths to obtain appropriate circulation head. (author)

  19. Experimental investigation of air bubble flows in a water pool

    International Nuclear Information System (INIS)

    This paper presents experimental results on rising bubbles in the wetwell of a boiling water reactor (BWR) in a loss-of-coolant accident in the pressure suppression pool (PSP). This accident scenario includes three processes: blowdown and associated water slug phenomena, bubble dynamics and related water flow during continuous release of gases and development of a thermal stratification. The paper covers the middle phase where air is fed through a downcomer. The developments of bubble formation and bubble flow are investigated by means of high speed videos. Diameter, velocity, formation frequency and breakup distance of bubbles are evaluated using automated image evaluation procedures. The experiments have been performed in the cylindrical vessel of the THAI test facility with a height of 9.2 m and a diameter of 3.2 m. (author)

  20. An application of the method of moments to the modeling of bubbly flow

    International Nuclear Information System (INIS)

    Bubbly flows are relevant in nuclear reactors thermalhydraulics and safety analysis. Regularly, empirical constitutive laws are required to close the two-fluid equations, particularly in relating the interfacial area and the bubble number densities to the local void fraction. In this article, starting from a generalized Boltzmann transport equation for the bubble size spectrum, a convection equation for the bubble number density is derived using the method of moments. The equation is analyzed for a vertical bubbly flow in stagnated liquid, showing excellent agreement with experimental data. The model is useful as a mean to provide conservation-based correlations to complement the existing two-fluid models

  1. PROBLEM OF METAL VAPOUR BUBBLE GROWTH IN MAGNETIC FIELD

    OpenAIRE

    Jerzy Gąsiorowski; Jacek Szypliński; Ryszard Wnuk

    1982-01-01

    Limits influencing on hieat transfer method's choice, in fusion reactors, have been analysed. Structure of nucleate boiling of metal was selected, as a effective way of problem solution. Existence of relation between magnetic field and heat transfer intensity in boiling metal was shown.A part of Lorentz's forces in motion balance of valour bubble rising in liquid metal was evaluated. Magnetic field influence on elipsoidal vapour bubble growth time was estimated.

  2. Investigations for the reduction of specific power input at the production and downstream processing of antibiotics on the example of penicillin II. Pt. 1. Product formation in loop-type bubble columns. Final report. Untersuchugen zur Minimierung der Energie bei der Produktion und Aufarbeitung von Antibiotika am Beispiel des Penicillins II. T. 1. Produktbildung in Mammut-Schlaufen-Reaktoren. Abschlussbericht

    Energy Technology Data Exchange (ETDEWEB)

    Schuegerl, K.; Lorenz, T.; Likidis, Z.

    1986-08-01

    The concentrations of most important medium components were permanently measured by means of an on-line analyser system consisting of a ultrafiltration probe for continuous sterile sampling of cell-free fermentation broth and a multichannel autoanalyser. An improved process operation was possible by coupling the reactor and its periphery to a process computer to store and evaluate the measured data. The specific power input into the applied airlift tower loop reactor could be considerably reduced by means of pellet morphology and a parameter-adaptive closed loop control of the dissolved oxygen concentration in the broth. Reactive extraction of penicillin from model media and fermentation as well as its reextraction were carried out in different extraction columns, in a mixer-settler and in different centrifugal extractors. By testing several carriers a new inexpensive compound, diisotridecylamin, was found, which proved to be - beside Amberlite LA-2 - as especially suitable for the extraction of penicillin. Extractions were carried out at pH 5 and reextractions at pH 7.5 at different phase-rations, throughputs from 20 l/h up to 1.5 m/sup 3//h and at penicillin concentrations up to 40 g/l with very high degrees of extraction.

  3. Rotating bubble membrane radiator

    Science.gov (United States)

    Webb, Brent J.; Coomes, Edmund P.

    1988-12-06

    A heat radiator useful for expelling waste heat from a power generating system aboard a space vehicle is disclosed. Liquid to be cooled is passed to the interior of a rotating bubble membrane radiator, where it is sprayed into the interior of the bubble. Liquid impacting upon the interior surface of the bubble is cooled and the heat radiated from the outer surface of the membrane. Cooled liquid is collected by the action of centrifical force about the equator of the rotating membrane and returned to the power system. Details regarding a complete space power system employing the radiator are given.

  4. Design of an Extractive Distillation Column for the Environmentally Benign Separation of Zirconium and Hafnium Tetrachloride for Nuclear Power Reactor Applications

    OpenAIRE

    Duong, Pham

    2015-01-01

    Nuclear power with strengthened safety regulations continues to be used as an important resource in the world for managing atmospheric greenhouse gases and associated climate change. This study examined the environmentally benign separation of zirconium tetrachloride (ZrCl4) and hafnium tetrachloride (HfCl4) for nuclear power reactor applications through extractive distillation using a NaCl-KCl molten salt mixture. The vapor–liquid equilibrium behavior of ZrCl4 and HfCl4 over t...

  5. Fluctuations of the Solitary Bubble at the Separation from the Air Cavity, Compressed by the Magnetic Field in Magnetic Liquid

    Directory of Open Access Journals (Sweden)

    M.L. Boev

    2013-12-01

    Full Text Available In the article, on the basis of the concept of "display" of geometry of a free surface of the "low-magnetic" environment by the topography of isolines of the module of intensity of a magnetic field, it is studied a form of a free surface of magnetic fluid in a static condition at the initial stage of rapprochement of a ring magnet with a surface of a column of magnetic fluid in a tube and at a stage of pressing of a cavity to a bottom. It is shown that the separation of bubbles from an air cavity occurs in close proximity to the plane of symmetry of a ring magnet on its axis. It is described the method and experimental installation for studying the possibility of electromagnetic indication of sizes of the air bubbles, being in magnetic fluid. It is discussed the results of experimental research on process of a separation of solitary air bubble from a cavity, contained in magnetic fluid and squeezed by ponderomotive forces of a magnetic field which are of interest for creation of essentially new technique of the dosed supply of small amount of gas in the reactor.

  6. Bubble Collision in Curved Spacetime

    International Nuclear Information System (INIS)

    We study vacuum bubble collisions in curved spacetime, in which vacuum bubbles were nucleated in the initial metastable vacuum state by quantum tunneling. The bubbles materialize randomly at different times and then start to grow. It is known that the percolation by true vacuum bubbles is not possible due to the exponential expansion of the space among the bubbles. In this paper, we consider two bubbles of the same size with a preferred axis and assume that two bubbles form very near each other to collide. The two bubbles have the same field value. When the bubbles collide, the collided region oscillates back-and-forth and then the collided region eventually decays and disappears. We discuss radiation and gravitational wave resulting from the collision of two bubbles

  7. Methane gas seepage - Disregard of significant water column filter processes?

    Science.gov (United States)

    Schneider von Deimling, Jens; Schmale, Oliver

    2016-04-01

    Marine methane seepage represents a potential contributor for greenhouse gas in the atmosphere and is discussed as a driver for climate change. The ultimate question is how much methane is released from the seafloor on a global scale and what fraction may reach the atmosphere? Dissolved fluxes from methane seepage sites on the seabed were found to be very efficiently reduced by benthic microbial oxidation, whereas transport of free gas bubbles from the seabed is considered to bypass the effective benthic methane filter. Numerical models are available today to predict the fate of such methane gas bubble release to the water column in regard to gas exchange with the ambient water column, respective bubble lifetime and rise height. However, the fate of rising gas bubbles and dissolved methane in the water column is not only governed by dissolution, but is also affected by lateral oceanographic currents and vertical bubble-induced upwelling, microbial oxidation, and physico-chemical processes that remain poorly understood so far. According to this gap of knowledge we present data from two study sites - the anthropogenic North Sea 22/4b Blowout and the natural Coal Oil point seeps - to shed light into two new processes gathered with hydro-acoustic multibeam water column imaging and microbial investigations. The newly discovered processes are hereafter termed Spiral Vortex and Bubble Transport Mechanism. Spiral Vortex describes the evolution of a complex vortical fluid motion of a bubble plume in the wake of an intense gas release site (Blowout, North Sea). It appears very likely that it dramatically changes the dissolution kinetics of the seep gas bubbles. Bubble Transport Mechanism prescribes the transport of sediment-hosted bacteria into the water column via rising gas bubbles. Both processes act as filter mechanisms in regard to vertical transport of seep related methane, but have not been considered before. Spiral Vortex and Bubble Transport Mechanism represent the

  8. PIV measurement of pressure distributions about single bubbles

    International Nuclear Information System (INIS)

    Measurements of velocity and pressure distributions around a bubble are of fundamental importance to model the forces acting on the bubbles and to verify detailed numerical methods for the prediction of flow in nuclear reactors. The measurements of velocity distributions around a bubble have been conducted to understand the interaction between liquid flow and bubbles. However there are few studies on pressure distributions around a bubble for the lack of measurement method. In this study, we developed a method for evaluating a pressure distribution by making use of velocity data obtained by a particle image velocimetry (PIV) or a particle tracking velocimetry (PTV), and applied it to laminar pipe flows, laminar flows around single particles and single bubbles in a pipe to examine its accuracy and applicability to the flow around single bubbles. As a result, we could confirm that the method can evaluate the pressure distribution in various laminar flow, provided that the velocity data process a good quality and a flow of concern is two-dimensional. The proposed method therefore has a potential to provide the important information for modeling of the bubble motion and verification of CFD methods such as interface tracking and lattice Boltzmann methods. (author)

  9. Bubble chamber: antiproton annihilation

    CERN Multimedia

    1971-01-01

    These images show real particle tracks from the annihilation of an antiproton in the 80 cm Saclay liquid hydrogen bubble chamber. A negative kaon and a neutral kaon are produced in this process, as well as a positive pion. The invention of bubble chambers in 1952 revolutionized the field of particle physics, allowing real tracks left by particles to be seen and photographed by expanding liquid that had been heated to boiling point.

  10. A Gold Bubble?

    OpenAIRE

    Dirk G Baur; Kristoffer Glover

    2012-01-01

    In this paper we use a test developed by Phillips et al. (2011) to identify a bubble in the gold market. We find that the price of gold followed an explosive price process between 2002 and 2012 interrupted only briefly by the subprime crisis in 2008. We also provide a theoretical foundation for such bubble tests based on a behavioural model of heterogeneous agents and demonstrate that periods of explosive price behaviour are consistent with increased chartist activity in the gold market. The ...

  11. CONDITIONS FOR BUBBLE FORMATION

    OpenAIRE

    Joffe, M

    2010-01-01

    A bubble is typically defined as ìtrade in high volume at prices that are considerably at variance from intrinsic valueî, which is compatible both with higher or lower prices, whereas the metaphor suggests something asymmetric that gradually inflates rather than deflates. Whether bubbles are symmetric or not is an empirical question; the historical record appears to be that they are asymmetric, but the literature is unclear on this point. In addition, in some types of market such as property,...

  12. Radio Bubbles in Clusters

    CERN Document Server

    Dunn, R J H; Taylor, G B

    2005-01-01

    We extend our earlier work on cluster cores with distinct radio bubbles, adding more active bubbles, i.e. those with Ghz radio emission, to our sample, and also investigating ``ghost bubbles,'' i.e. those without GHz radio emission. We have determined k, which is the ratio of the total particle energy to that of the electrons radiating between 10 MHz and 10 GHz. Constraints on the ages of the active bubbles confirm that the ratio of the energy factor, k, to the volume filling factor, f lies within the range 1 < k/f < 1000. In the assumption that there is pressure equilibrium between the radio-emitting plasma and the surrounding thermal X-ray gas, none of the radio lobes has equipartition between the relativistic particles and the magnetic field. A Monte-Carlo simulation of the data led to the conclusion that there are not enough bubbles present in the current sample to be able to determine the shape of the population. An analysis of the ghost bubbles in our sample showed that on the whole they have high...

  13. Biogas quality upgrade by simultaneous removal of CO{sub 2} and H{sub 2}S in a packed column reactor

    Energy Technology Data Exchange (ETDEWEB)

    Tippayawong, N.; Thanompongchart, P. [Department of Mechanical Engineering, Faculty of Engineering, Chiang Mai University, Chiang Mai 50200 (Thailand)

    2010-12-15

    Biogas from anaerobic digestion of biological wastes is a renewable energy resource. It has been used to provide heat, shaft power and electricity. Typical biogas contains 50-65% methane (CH{sub 4}), 30-45% carbon dioxide (CO{sub 2}), moisture and traces of hydrogen sulphide (H{sub 2}S). Presence of CO{sub 2} and H{sub 2}S in biogas affects engine performance adversely. Reducing CO{sub 2} and H{sub 2}S content will significantly improve quality of biogas. In this work, a method for biogas scrubbing and CH{sub 4} enrichment is presented. Chemical absorption of CO{sub 2} and H{sub 2}S by aqueous solutions in a packed column was experimentally investigated. The aqueous solutions employed were sodium hydroxide (NaOH), calcium hydroxide (Ca(OH){sub 2}) and mono-ethanolamine (MEA). Liquid solvents were circulated through the column, contacting the biogas in countercurrent flow. Absorption characteristics were examined. Test results revealed that the aqueous solutions used were effective in reacting with CO{sub 2} in biogas (over 90% removal efficiency), creating CH{sub 4} enriched fuel. H{sub 2}S was removed to below the detection limit. Absorption capability was transient in nature. Saturation was reached in about 50 min for Ca(OH){sub 2}, and 100 min for NaOH and MEA, respectively. With regular replacement or regeneration of used solutions, upgraded biogas can be maintained. This technique proved to be promising in upgrading biogas quality. (author)

  14. CS emission near MIR-bubbles

    CERN Document Server

    Watson, C; Quintanar, N; Candelaria, T

    2016-01-01

    We survey 44 young stellar objects located near the edges of mid-IR-identified bubbles in CS (1-0) using the Green Bank Telescope. We detect emission in 18 sources, indicating young protostars that are good candidates for being triggered by the expansion of the bubble. We calculate CS column densities and abundances. Three sources show evidence of infall through non-Gaussian line-shapes. Two of these sources are associated with dark clouds and are promising candidates for further exploration of potential triggered star formation. We obtained on-the-fly maps in CS (1-0) of three sources, showing evidence of significant interactions between the sources and the surrounding environment.

  15. The thermal column. A new irradiation position for fission-track dating in the University of Pavia Triga Mark II nuclear reactor

    International Nuclear Information System (INIS)

    In the present paper a new irradiation position arranged for fission-track dating in the Triga Mark II reactor of the University of Pavia is described. Fluence values determined using the NIST glass standard SRM 962a for fission-track dating and the traditional metal foils are compared. Relatively high neutron thermalization (cadmium ratio of 85.3 for gold and 643 for cobalt) and lack of significant fluence spatial gradients are very favorable factors for fission-track dating. Finally, international age standards (or putative age standards) irradiated in this new position yielded results consistent with independent reference ages. (author). 9 refs., 2 figs., 4 tabs

  16. Design of an Extractive Distillation Column for the Environmentally Benign Separation of Zirconium and Hafnium Tetrachloride for Nuclear Power Reactor Applications

    OpenAIRE

    Le Quang Minh; Nguyen Van Duc Long; Pham Luu Trung Duong; Youngmi Jung; Alireza Bahadori; Moonyong Lee

    2015-01-01

    Nuclear power with strengthened safety regulations continues to be used as an important resource in the world for managing atmospheric greenhouse gases and associated climate change. This study examined the environmentally benign separation of zirconium tetrachloride (ZrCl4) and hafnium tetrachloride (HfCl4) for nuclear power reactor applications through extractive distillation using a NaCl-KCl molten salt mixture. The vapor–liquid equilibrium behavior of ZrCl4 and HfCl4 over the molten s...

  17. The Milky Way Project and ATLASGAL: The distribution and physical properties of cold clumps near infrared bubbles

    CERN Document Server

    Kendrew, S; Simpson, R; Csengeri, T; Wienen, M; Lintott, C J; Povich, M S; Beaumont, C; Schuller, F

    2016-01-01

    We present a statistical study of the distribution and physical properties of cold dense material in and around the inner Galactic Plane near infrared bubbles as catalogued by the Milky Way Project citizen scientists. Using data from the ATLASGAL 870 um survey, we show that 48 +/- 2% of all cold clumps in the studied survey region (|l| <= 65 degrees, |b| <= 1 degree) are found in close proximity to a bubble, and 25 +/- 2% appear directly projected towards a bubble rim. A two-point correlation analysis confirms the strong correlation of massive cold clumps with expanding bubbles. It shows an overdensity of clumps along bubble rims that grows with increasing bubble size, which shows how interstellar medium material is reordered on large scales by bubble expansion around regions of massive star formation. The highest column density clumps appear resistent to the expansion, remaining overdense towards the bubbles' interior rather than being swept up by the expanding edge. Spectroscopic observations in ammon...

  18. Colliding with a crunching bubble

    Energy Technology Data Exchange (ETDEWEB)

    Freivogel, Ben; Freivogel, Ben; Horowitz, Gary T.; Shenker, Stephen

    2007-03-26

    In the context of eternal inflation we discuss the fate of Lambda = 0 bubbles when they collide with Lambda< 0 crunching bubbles. When the Lambda = 0 bubble is supersymmetric, it is not completely destroyed by collisions. If the domain wall separating the bubbles has higher tension than the BPS bound, it is expelled from the Lambda = 0 bubble and does not alter its long time behavior. If the domain wall saturates the BPS bound, then it stays inside the Lambda = 0 bubble and removes a finite fraction of future infinity. In this case, the crunch singularity is hidden behind the horizon of a stable hyperbolic black hole.

  19. Fermi Bubbles with HAWC

    CERN Document Server

    Solares, H A Ayala; Hüntemeyer, P

    2015-01-01

    The Fermi Bubbles, which comprise two large and homogeneous regions of spectrally hard gamma-ray emission extending up to $55^{o}$ above and below the Galactic Center, were first noticed in GeV gamma-ray data from the Fermi Telescope in 2010. The mechanism or mechanisms which produce the observed hard spectrum are not understood. Although both hadronic and lep- tonic models can describe the spectrum of the bubbles, the leptonic model can also explain similar structures observed in microwave data from the WMAP and Planck satellites. Recent publications show that the spectrum of the Fermi Bubbles is well described by a power law with an exponential cutoff in the energy range of 100MeV to 500GeV. Observing the Fermi Bubbles at higher gamma-ray energies will help constrain the origin of the bubbles. A steeper cutoff will favor a leptonic model. The High Altitude Water Cherenkov (HAWC) Observatory, located 4100m above sea level in Mexico, is designed to measure high-energy gamma rays between 100GeV to 100TeV. With...

  20. Bubbles of Metamorphosis

    Science.gov (United States)

    Prakash, Manu

    2011-11-01

    Metamorphosis presents a puzzling challenge where, triggered by a signal, an organism abruptly transforms its entire shape and form. Here I describe the role of physical fluid dynamic processes during pupal metamorphosis in flies. During early stages of pupation of third instar larvae into adult flies, a physical gas bubble nucleates at a precise temporal and spatial location, as part of the normal developmental program in Diptera. Although its existence has been known for the last 100 years, the origin and control of this ``cavitation'' event has remained completely mysterious. Where does the driving negative pressure for bubble nucleation come from? How is the location of the bubble nucleation site encoded in the pupae? How do molecular processes control such a physical event? What is the role of this bubble during development? Via developing in-vivo imaging techniques, direct bio-physical measurements in live insect pupal structures and physical modeling, here I elucidate the physical mechanism for appearance and disappearance of this bubble and predict the site of nucleation and its exact timing. This new physical insight into the process of metamorphosis also allows us to understand the inherent design of pupal shell architectures in various species of insects. Milton Award, Harvard Society of Fellows; Terman Fellowship, Stanford

  1. MEASUREMENT OF BUBBLE-BUBBLE INTERACTION DEPENDED ON REYNOLDS NUMBER USING STEREOSCOPIC BUBBLE-TRACKING TECHNIQUE

    Institute of Scientific and Technical Information of China (English)

    QU Jian-wu; MURAI Yuichi; YAMAMOTO Fujio

    2005-01-01

    Bubble-bubble interaction in free rising bubbly flows is experimentally investigated in the present study.The velocity vectors of the bubbles are measured by a stereoscopic bubble-tracking technique and then the relative velocity vectors of two nearest-neighbor bubbles are calculated with high statistical reliability.With the measurement data at Reynolds number ranging from 5 to 75, the vertical attraction and the horizontal repulsion are confirmed for Re<10 as known by the past study based on Navier-Stokes simulation.The new finding of the present measurement is that the bubbles of Re>30 have repulsive velocity bothin the horizontal and the vertical directions as those rise closely.Moreover, the three-dimensional structure of the bubble-bubble interaction is discussed with the data analysis of the interaction vector fields.

  2. Simultaneous determination of imidacloprid and carbendazim in water samples by ion chromatography with fluorescence detector and post-column photochemical reactor.

    Science.gov (United States)

    Subhani, Qamar; Huang, Zhongping; Zhu, Zuoyi; Zhu, Yan

    2013-11-15

    A new analytical method has been developed and validated for the simultaneous determination of pesticides from different classes using ion chromatography-online photochemical derivatisation-fluorescence detector (IC-hv-FD). Fluorimetric detection was performed at λex/λem=332 nm/367 nm for imidacloprid and then detector was set at λex/λem=247 nm/470 nm for carbendazim. The two pesticides imidacloprid and carbendazim were successfully separated isocratically on an IonPac(®) AS11 (250 mm × 4 mm i.d; 13 µm particle size, Dionex) anion-exchange column using 40 mM KOH with 10% (v/v) acetonitrile and pumped at a flow rate of 1.0 mL min(-1). Under the optimized conditions, the limit of detection (LOD, S/N=3) of imidacloprid and carbendazim were 7.8 µg L(-1) and 67 µg L(-1), respectively. The experimental results showed that there was good linearity with a correlation coefficient (r)≥0.9966 over the range of 0.05-10 mg L(-1) for imidacloprid and 0.2-15 mg L(-1) for carbendazim. Good reproducibility with a relative standard deviation (RSD, n=7) less than 4.5%. Finally, the proposed method was applied with satisfactory results to the analysis of these pesticides in ground water, lake water and river water without any pre-treatment of samples. The average spiked recoveries were in the range of 90-104%. PMID:24148383

  3. Electric-field enhanced fluidized beds : a low-energy bubble control method

    NARCIS (Netherlands)

    Kleijn van Willigen, F.

    2006-01-01

    Reducing the size of gas bubbles can significantly improve the performance of gas-solid fluidized beds one of the most common reactor types in the chemical industry applied for such diverse systems as gasoline and plastics production to foods processing. However, a control of bubbles in these reac

  4. Analyzing Cosmic Bubble Collisions

    CERN Document Server

    Gobbetti, Roberto

    2012-01-01

    We develop a set of controlled, analytic approximations to study the effects of bubble collisions on cosmology. We expand the initial perturbation to the inflaton field caused by the collision in a general power series, and determine its time evolution during inflation in terms of the coefficients in the expansion. In models where the observer's bubble undergoes sufficient slow-roll inflation to solve the flatness problem, in the thin wall limit only one coefficient in the expansion is relevant to observational cosmology, allowing nearly model-independent predictions. We discuss two approaches to determining the initial perturbation to the inflaton and the implications for the sign of the effect (a hot or cold spot on the Cosmic Microwave Background temperature map). Lastly, we analyze the effects of collisions with thick-wall bubbles, i.e. away from the thin-wall limit.

  5. Pseudo-Stable Bubbles

    CERN Document Server

    Gleiser, Marcello

    1994-01-01

    The evolution of spherically symmetric unstable scalar field configurations (``bubbles'') is examined for both symmetric (SDWP) and asymmetric (ADWP) double-well potentials. Bubbles with initial static energies $E_0\\la E_{{\\rm crit}}$, where $E_{{\\rm crit}}$ is some critical value, shrink in a time scale determined by their linear dimension, or ``radius''. Bubbles with $E_0\\ga E_{{\\rm crit}}$ evolve into time-dependent, localized configurations which are {\\it very} long-lived compared to characteristic time-scales in the models examined. The stability of these configurations is investigated and possible applications are briefly discussed.tic time-scales in the models examined. The stability of these configurations is investigated and possible applications are briefly discussed.

  6. Bubble nuclei; Noyaux Bulles

    Energy Technology Data Exchange (ETDEWEB)

    Legoll, F. [Service de Physique Theorique, CEA Centre d`Etudes de Saclay, 91 - Gif-sur-Yvette (France)

    1998-07-22

    For nuclei with very high electrical charge, the Coulomb field is expected to drive the protons away from the centre to the surface of the nucleus. Such a nucleus would be no more compact but look like a bubble. The goal of this work is to confirm this idea. We are interested in only the ground state of spherical nuclei. We use the Skyrme potential with the Sly4 parametrization to calculate the mean-field Hamiltonian. Paring correlations are described by a surface-active delta paring interaction. In its ground state the nucleus {sup A=900} X{sub Z=274} is shown to be a bubble. Another stable state is found with a little higher energy: it is also a bubble. (author) 11 refs., 18 figs., 33 tabs.

  7. Investigation of The Bubble Foam Separation Technique To Extract Protein From Whey

    OpenAIRE

    Mohammed Matouq

    2008-01-01

    Separation of proteins from whey; namely α- Lactoglobulin and β-Lactalbumin was obtained using the bubble foam column technique. Two types of whey were conducted in this study; yogurt whey and cheese whey. The effect of gas flow-rate and the height of the whey (liquid holdup) inside the column were studied at room temperature and at constant pH of whey. Whey used here obtained from local dairy factory as waste, and was used to investigate the performance ability of bubble column...

  8. Enhancing mass transfer and ethanol production in syngas fermentation of Clostridium carboxidivorans P7 through a monolithic biofilm reactor

    International Nuclear Information System (INIS)

    Highlights: • Syngas fermentation process is limited by gas-to-liquid mass transfer. • A novel monolithic biofilm reactor (MBR) for efficient mass transfer was developed. • MBR with slug flow resulted in higher kLa than bubble column reactor (BCR). • MBR enhanced ethanol productivity by 53% compared to BCR. • MBR was demonstrated as a promising reactor configuration for syngas fermentation. - Abstract: Syngas fermentation is a promising process for producing fuels and chemicals from lignocellulosic biomass. Currently syngas fermentation faces several engineering challenges, with gas-to-liquid mass transfer limitation representing the major bottleneck. The aim of this work is to evaluate the performance of a monolithic biofilm reactor (MBR) as a novel reactor configuration for syngas fermentation. The volumetric mass transfer coefficient (kLa) of the MBR was evaluated in abiotic conditions within a wide range of gas flow rates (i.e., gas velocity in monolithic channels) and liquid flow rates (i.e., liquid velocity in the channels). The kLa values of the MBR were higher than those of a controlled bubble column reactor (BCR) in certain conditions, due to the slug flow pattern in the monolithic channels. A continuous syngas fermentation using Clostridium carboxidivorans P7 was conducted in the MBR system under varying operational conditions, with the variables including syngas flow rate, liquid recirculation between the monolithic column and reservoir, and dilution rate. It was found that the syngas fermentation performance – measured by such parameters as syngas utilization efficiency, ethanol concentration and productivity, and ratio of ethanol to acetic acid – depended not only on the mass transfer efficiency but also on the biofouling or abrading of the biofilm attached on the monolithic channel wall. At a condition of 300 mL/min of syngas flow rate, 500 mL/min of liquid flow rate, and 0.48 day−1 of dilution rate, the MBR produced much higher syngas

  9. Determination of Carbon-14 (14C) and Tritium (3H) in the graphite thermal column of a IRT-2000 research reactor in Sofia

    International Nuclear Information System (INIS)

    Radiocarbon has average, and tritium has low level of radiotoxicity, but both are easily absorbable radionuclide from the body as due to their chemical nature they are included in almost all the chemical compounds involved in metabolic chains and in structure of proteins and biological macromolecules. Due to above mentioned reasons, the analysis and determination of these two major radionuclides is very significant for radiation protection for both the public and the environment as well as for occupational exposure of personnel. This publication describes the detailed procedure for determining the concentration of 3H and 14C in samples selected at the stage 'partial dismantling' of the research nuclear reactor IRT-2000 reconstruction. The procedure consists graphite sample thermal burning in the tubing muffle furnace at a maximum temperature of 850'0C. After combustion the gas mixture passes through a CuO catalyst, heated to 450-5000C and through a series of traps for 3H and 14C capturing. The captured CO2+ 14CO2 as Na2CO3 in NaOH precipitates with BaCl2 as BaCO3 and it is followed by a liquid scintillation spectrometry measurements

  10. A model of phase distribution in bubble flow

    International Nuclear Information System (INIS)

    The knowledge of phase distribution in a channel with bubble flow is important for several problems in nuclear reactor technology. It is possible to assume the random bubble motion as a Markov diffusion process caused by turbulent liquid velocity fluctuations. A diffusion coefficient can be evaluated in this case. Diffusion equations and their boundary conditions are given to calculate bubble distribution in some cases of practical interest. The solution is possible for the most problems on numerical way only. Analytical solutions are shown in the case of a small bubble source near the wall, for instance a water to sodium microleak in a sodium-heated steam generator. Results of a two-dimensional calculation are discussed from the point of view of microleak detection. (author)

  11. Correlation of bubble rise velocity and volume

    International Nuclear Information System (INIS)

    This project was conducted at Westinghouse's Savannah River Laboratories (SRL). The goal of SRL is to make certain that the modifications on the reactor are safe for those working at the plant as well as the general public. One of the steps needed to insure safety is the knowledge of the occurrences that result from a plenum pipe breakage. When a plenum pipe breaks, two things occur: air is sucked into the pipe and is trapped in the cooling water; and water used to cool the fuel rods is lost. As a result of these occurrences, the water is slowed down by both the loss in water pressure and the upward force of air bubbles pushing against the downward force of the water. The project required the conducting of tests to find the bubble velocity in an annular ribbed pipe filled with stagnant water. This document discusses the methodology and results of this testing

  12. Visualization of cavitation bubbles; Visualisation de bulles de cavitation

    Energy Technology Data Exchange (ETDEWEB)

    Chouvellon, M.; Fournel, Th.; Ducottet, Ch. [Universite Jean Monnet, 31 Saint-Etienne (France). Laboratoire Traitement du Signal et Instrumentation-UMR CNRS 5516

    1999-07-01

    A high frequency ultrasonic reactor allows the degradation of some organic compounds which are not or poorly biodegradable by usual methods in industrial flows. The propagation of an ultrasonic wave in a liquid induces cavitation phenomena. The implosion of cavitation bubble locally causes a temperature of about several thousand Kelvins and a pressure of about several hundred bars. Such conditions allow the creation of the hydroxyl radicals and then the oxidation of organic compounds. The aim of this paper is to describe the method used to visualize cavitation bubbles in an ultrasonic reactor at a frequency of 500 kHz. The experimental set-up and the measurement of both the bubble radius and the fringe separation are presented. (authors)

  13. Aerosol removal from gas bubbles resulting from molten core-concrete interactions

    International Nuclear Information System (INIS)

    Pool scrubbing, the removal of aerosol particles by bubbling contaminated gases though a water pool, could be a significant mechanism in limiting the severity of certain nuclear reactor accidents. BUSCA is a computer code designed to model bubble thermal-hydraulics and associated pool scrubbing removal processes. This paper describes the enhancements made to the code since the Palo Alto CSNI conference in 1986. BUSCA now has the ability to model effects of different bubble shapes, bulk condensation, bubble breakup, and bubble cluster and plume rise conditions. A series of sensitivity tests have been included to assess the significance of these additions on decontamination factor calculations. In summary: A number of mechanisms have been successfully introduced into the BUSCA pool scrubbing code. These include modelling of bulk condensation, bubble breakup and cluster and plume rise conditions. This paper has illustrated the effects of these changes on DF calculation. In general, decontamination factors are seen to increase with, i) Increasing initial mole fraction of steam in bubble, ii) Reduction of the initial bubble size, iii) Reduction of the pool temperature, iv) Increasing the initial temperature difference between the pool and the bubble, v) Increasing the pool depth, vi) Increasing the solubility of the aerosol particles. while a reduction in decontamination factors can be brought about by assuming the bubbles rise as a plume rather than as individual bubbles

  14. Scanning bubble chamber pictures

    CERN Multimedia

    1974-01-01

    These were taken at the 2 m hydrogen bubble chamber. The photo shows an early Shiva system where the pre-measurements needed to qualify the event were done manually (cf photo 7408136X). The scanning tables were located in bld. 12. Gilberte Saulmier sits on foreground, Inge Arents at centre.

  15. Critical scattering by bubbles

    International Nuclear Information System (INIS)

    We apply the complex angular momentum theory to the problem of the critical scattering of light by spherical cavities in the high frequency limit (permittivity greater than the external media) (e.g, air bubble in water) (M.W.O.)

  16. BEBC bubble chamber

    CERN Multimedia

    1972-01-01

    Looking up into the interior of BEBC bubble chamber from the expansion cylinder. At the top of the chamber two fish-eye lenses are installed and three other fish-eye ports are blanked off. In the centre is a heat exchanger.

  17. Interaction of two spark-generated bubbles near a confined free surface

    Science.gov (United States)

    Saleki-Haselghoubi, Noureyeh; Shervani-Tabar, Mohammad Taghi; Taeibi-Rahni, Mohammad; Dadvand, Abdolrahman

    2016-06-01

    In this paper, the oscillation of two spark-generated bubbles placed on a vertical column in close proximity to a confined free surface is considered. The confined free surface is accorded by the top opening of different configurations. These configurations include (i) a centrally perforated horizontal flat plate ({θ=90°)}, (ii) vertically placed cylinder ({θ=0°)} and (iii) nozzle ({θ >0°)}. The main objective of the present work is to study the effects of key parameters such as the nozzle geometry, the locations of the energy input (i.e., initial position of the bubbles with respect to each other and relative to the free surface) on the dynamics of the two bubbles and the free surface. It was found that the lifetime of the upper bubble decreases from the vertical cylinder to the flat plate case. In addition, by reducing the inter-bubble distance, the lifetime of the upper bubble becomes longer and the repulsion between two bubbles during the expansion phase is stronger. Finally, by reducing the upper bubble-free surface distance, the repulsion between two bubbles during expansion phase increases, the tendency of the upper bubble to rebound and initiate another oscillation cycle decreases, and the amplitude of elevation of the free surface increases.

  18. Numerical simulation of vapor bubble condensation in turbulent subcooled flow boiling

    International Nuclear Information System (INIS)

    Highlights: • The two-phase flow was modeled using VOF interface tracking method. • Bubble dynamics at high pressure, high velocity conditions was captured using LES. • Reverse bubble velocity trends occur for varying pressure with zero and nonzero bulk velocity. • Condensation rate increases with subcooling temperature and bulk velocity. • Bubble distortion increases with system pressure and bulk velocity. - Abstract: Subcooled flow boiling is a significant heat transfer regime in pressurized water reactors (PWRs) and also occurs in boiling water reactors (BWRs) prior to the onset of saturated nucleate boiling. In subcooled boiling, individual bubbles experience a life-cycle of nucleation from the wall, (possible) departure from the wall, and transport along the channel during condensation/collapse. The present paper focuses on the last stage of this life cycle. CFD analysis of a single bubble behavior in upward subcooled flow boiling was performed using volume-of-fluid (VOF) interface tracking method and large eddy simulation (LES) turbulence model. High pressure steam-water conditions at high flow velocity were simulated due to their relevance to the nuclear application. The numerical solutions were compared with terminal velocity correlations. Bubble behavior was investigated at different system pressure, subcooling temperature, bubble diameter, pipe diameter, and bulk fluid velocity, corresponding to bulk Reynolds number range of 0–410,000. The effects of these parametric variations on bubble rise velocity, deformation rate, trajectory, and distortion are presented. Results show that bubble rise velocity increases with bulk velocity, and bubble size, but decreases with increasing pipe diameter. A reverse bubble velocity trend with varying system pressure is observed with and without bulk velocity. Bubble condensation rate decreased with increasing system pressure, bubble size and pipe diameter, but increased with increasing subcooling temperature

  19. Numerical simulation of vapor bubble condensation in turbulent subcooled flow boiling

    Energy Technology Data Exchange (ETDEWEB)

    Owoeye, Eyitayo James, E-mail: msgenius10@ufl.edu; Schubring, DuWanye, E-mail: dlschubring@ufl.edu

    2015-08-15

    Highlights: • The two-phase flow was modeled using VOF interface tracking method. • Bubble dynamics at high pressure, high velocity conditions was captured using LES. • Reverse bubble velocity trends occur for varying pressure with zero and nonzero bulk velocity. • Condensation rate increases with subcooling temperature and bulk velocity. • Bubble distortion increases with system pressure and bulk velocity. - Abstract: Subcooled flow boiling is a significant heat transfer regime in pressurized water reactors (PWRs) and also occurs in boiling water reactors (BWRs) prior to the onset of saturated nucleate boiling. In subcooled boiling, individual bubbles experience a life-cycle of nucleation from the wall, (possible) departure from the wall, and transport along the channel during condensation/collapse. The present paper focuses on the last stage of this life cycle. CFD analysis of a single bubble behavior in upward subcooled flow boiling was performed using volume-of-fluid (VOF) interface tracking method and large eddy simulation (LES) turbulence model. High pressure steam-water conditions at high flow velocity were simulated due to their relevance to the nuclear application. The numerical solutions were compared with terminal velocity correlations. Bubble behavior was investigated at different system pressure, subcooling temperature, bubble diameter, pipe diameter, and bulk fluid velocity, corresponding to bulk Reynolds number range of 0–410,000. The effects of these parametric variations on bubble rise velocity, deformation rate, trajectory, and distortion are presented. Results show that bubble rise velocity increases with bulk velocity, and bubble size, but decreases with increasing pipe diameter. A reverse bubble velocity trend with varying system pressure is observed with and without bulk velocity. Bubble condensation rate decreased with increasing system pressure, bubble size and pipe diameter, but increased with increasing subcooling temperature

  20. Bubble Dynamics and Shock Waves

    CERN Document Server

    2013-01-01

    This volume of the Shock Wave Science and Technology Reference Library is concerned with the interplay between bubble dynamics and shock waves. It is divided into four parts containing twelve chapters written by eminent scientists. Topics discussed include shock wave emission by laser generated bubbles (W Lauterborn, A Vogel), pulsating bubbles near boundaries (DM Leppinen, QX Wang, JR Blake), interaction of shock waves with bubble clouds (CD Ohl, SW Ohl), shock propagation in polydispersed bubbly liquids by model equations (K Ando, T Colonius, CE Brennen. T Yano, T Kanagawa,  M Watanabe, S Fujikawa) and by DNS (G Tryggvason, S Dabiri), shocks in cavitating flows (NA Adams, SJ Schmidt, CF Delale, GH Schnerr, S Pasinlioglu) together with applications involving encapsulated bubble dynamics in imaging (AA Doinikov, A Novell, JM Escoffre, A Bouakaz),  shock wave lithotripsy (P Zhong), sterilization of ships’ ballast water (A Abe, H Mimura) and bubbly flow model of volcano eruptions ((VK Kedrinskii, K Takayama...

  1. Modeling of column apparatuses: A review

    Energy Technology Data Exchange (ETDEWEB)

    Doichinova, M., E-mail: mar-doych@mail.bg, E-mail: petyabs@yahoo.com; Popova-Krumova, P., E-mail: mar-doych@mail.bg, E-mail: petyabs@yahoo.com [Institute of Chemical Engineering, Bulgarian Academy of Sciences, Acad. St.Angelov str., Bl. 103, 1113 Sofia (Bulgaria)

    2013-12-18

    This paper presents a review of the modeling method on the base of the physical approximations of the mechanics of continua, which have been developed for processes in column apparatuses. This method includes diffusion type of model for modeling of mass transfer with chemical reaction in column apparatuses with and without circulation zones. The diffusion type of model is used for modeling of scale effect in column apparatuses too. The study concluded that the proposal method is possibility for investigation the influence of radial non uniformity of the velocity distribution on the process efficiency, influence of zones breadths on the mass transfer efficiency in the column. The method of the column apparatuses modeling can be used for modeling of physical and chemical absorption, chemical adsorption, homogeneous and heterogeneous (catalytic) chemical reactions, airlift reactors for chemical and photochemical reactions.

  2. Bubble Size Models for the Prediction of Bubbly Flow with CMFD Code

    Energy Technology Data Exchange (ETDEWEB)

    Bak, Jin-yeong; Yun, Byong-jo; Jeong, Jae-jun [Pusan National Univ., Busan (Korea, Republic of)

    2015-05-15

    In recent years, the use of computational multi-fluid dynamics (CMFD) codes has been extended to the analysis of multi-dimensional two-phase flow for the operation and safety analysis of nuclear power plants (NPP). In these applications, an accurate prediction of bubble behaviors is one of major concerns. Yao and Morel and Yeoh and Tu respectively applied interfacial area concentration transport (IACT) equation and bubble number density transport equation into CMFD code. Recently Lo and Zhang tried to apply the generalized S{sub γ} model to the predictions of not only droplet size in the oil-water flow but also bubble size in the air-water flow. In this paper, three-dimensional numerical simulations for the gas-liquid two-phase flow were conducted to validate and confirm the performance of S{sub γ} bubble size model for the further application to the narrow rectangular boiling channel for the research reactor core, using the commercial CFD code STAR CCM''+ ver. 9.06. For this, S{sub γ} model was evaluated against air-water data of DEDALE and Hibiki et al.'s experiment. These experimental data were obtained in a vertically arranged pipe under upwards air-water flow condition. Detailed descriptions on the S{sub γ} with its breakup and coalescence model are presented in the present manuscript.

  3. More bubbling solutions

    International Nuclear Information System (INIS)

    In this note we construct families of asymptotically flat, smooth, horizonless solutions with a large number of non-trivial two-cycles (bubbles) of N = 1 five-dimensional supergravity with an arbitrary number of vector multiplets, which may or may not have the charges of a macroscopic black hole and which contain the known bubbling solutions as a sub-family. We do this by lifting various multi-center BPS states of type IIA compactified on Calabi-Yau three-folds and taking the decompactification (M-theory) limit. We also analyse various properties of these solutions, including the conserved charges, the shape, especially the (absence of) throat and closed timelike curves, and relate them to the various properties of the four-dimensional BPS states. We finish by briefly commenting on their degeneracies and their possible relations to the fuzzball proposal of Mathur et al

  4. Bubble dynamics in drinks

    Czech Academy of Sciences Publication Activity Database

    Broučková, Zuzana; Trávníček, Zdeněk; Šafařík, P.

    Liberec: Technical University of Liberec, 2013 - (Vít, T.; Dančová, P.; Novotný, P.), s. 114-118 ISBN 978-80-260-5375-0. [Experimental Fluid Mechanics 2013. Kutná hora (CZ), 19.11.2013-22.11.2013] R&D Projects: GA ČR(CZ) GCP101/11/J019 Institutional support: RVO:61388998 Keywords : bubbles * hot chocolate effect * visualization Subject RIV: BK - Fluid Dynamics

  5. CRISIS FOCUS Blowing Bubbles

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The Chinese stock and property markets have been outperforming expectations, fueled by an unprecedented surge in bank lending. Xie Guozhong, an economist and board member of Rosetta Stone Advisors, argues the robust Chinese economic figures are only propped up by bubbles, whose bursting will lead to a hard landing for the economy. Xie published his opinion in a related article in Caijing Magazine. Edited excerpts follow:

  6. Mechanisms of gas bubble retention

    International Nuclear Information System (INIS)

    Retention and episodic release of flammable gases are critical safety concerns regarding double-shell tanks (DSTs) containing waste slurries. Previous investigations have concluded that gas bubbles are retained by the slurry that has settled at the bottom of the DST. However, the mechanisms responsible for the retention of these bubbles are not well understood. In addition, the presence of retained gas bubbles is expected to affect the physical properties of the sludge, but essentially no literature data are available to assess the effect of these bubbles. The rheological behavior of the waste, particularly of the settled sludge, is critical to characterizing the tendency of the waste to retain gas bubbles. The objectives of this study are to elucidate the mechanisms contributing to gas bubble retention and release from sludge such as is in Tank 241-SY-101, understand how the bubbles affect the physical properties of the sludge, develop correlations of these physical properties to include in computer models, and collect experimental data on the physical properties of simulated sludges with bubbles. This report presents a theory and experimental observations of bubble retention in simulated sludge and gives correlations and new data on the effect of gas bubbles on sludge yield strength

  7. Optical sensing for characterization of bubble plumes from methane seeps

    Science.gov (United States)

    Pizarro, O.; Camilli, R.; Whelan, J.

    2004-12-01

    Methane seeps are potentially a key contributor to atmospheric methane and to the global greenhouse gas budget. Improved estimates of methane flux from ocean floor seeps is required to understand the magnitude and characteristics of this contribution to the carbon cycle. % State of the art In steady, slow seeps a large portion of the gas is dissolved and oxidized before reaching the surface. However, in high-intensity methane seeps the bubble density, speed and size are such that a significant fraction of the gas can reach the atmosphere. Dissolved methane can be measured fairly reliably at the sea surface with traditional equilibration techniques. New types of in-situ chemical sensors can quantify dissolved methane deeper in the water column. Quantifying methane within the water column in the free gas phase (i.e., in the form of bubbles) remains a challenging problem. Current approaches rely either on indirect acoustic methods or direct collection of bubbles. Acoustic methods have the disadvantage of requiring extensive calibration, and can fail to distinguish the bubble signal from other sources of acoustic noise. Gas-capture techniques are mechanically complex, have a surface expression that introduces some noise, and can potentially alias episodic events. %how slow ? In both cases the fine scale structure such as herogeneity of the bubbling plume is lost. % Proposed We propose a vision-based system to detect and track bubble plumes. High speed optical imagery is propenables precise measurements of the motion of bubbles through a process involving identification of the individual bubbles (and rejection of other particles). Additional image processing steps are then used to estimate each bubble's volume and velocity. These are then integrated to produce an estimate of volumetric flux rate. This technique can also reveal fine scale variabilities in the spatial and temporal structure within the plume. %We discuss sensing configurations based on a stereo setup and

  8. Evolution of bubble size distribution from gas blowout in shallow water

    Science.gov (United States)

    Zhao, Lin; Boufadel, Michel C.; Lee, Kenneth; King, Thomas; Loney, Norman; Geng, Xiaolong

    2016-03-01

    Gas is often emanated from the sea bed during a subsea oil and gas blowout. The size of a gas bubble changes due to gas dissolution in the ambient water and expansion as a result of a decrease in water pressure during the rise. It is important to understand the fate and transport of gas bubbles for the purpose of environmental and safety concerns. In this paper, we used the numerical model, VDROP-J to simulate gas formation in jet/plume upon release, and dissolution and expansion while bubble rising during a relatively shallow subsea gas blowout. The model predictions were an excellent match to the experimental data. Then a gas dissolution and expansion module was included in the VDROP-J model to predict the fate and transport of methane bubbles rising due to a blowout through a 0.10 m vertical orifice. The numerical results indicated that gas bubbles would increase the mixing energy in released jets, especially at small distances and large distances from the orifice. This means that models that predict the bubble size distribution (BSD) should account for this additional mixing energy. It was also found that only bubbles of certain sizes would reach the water surfaces; small bubbles dissolve fast in the water column, while the size of the large bubbles decreases. This resulted in a BSD that was bimodal near the orifice, and then became unimodal.

  9. Methane rising from the Deep: Hydrates, Bubbles, Oil Spills, and Global Warming

    Science.gov (United States)

    Leifer, I.; Rehder, G. J.; Solomon, E. A.; Kastner, M.; Asper, V. L.; Joye, S. B.

    2011-12-01

    Elevated methane concentrations in near-surface waters and the atmosphere have been reported for seepage from depths of nearly 1 km at the Gulf of Mexico hydrate observatory (MC118), suggesting that for some methane sources, deepsea methane is not trapped and can contribute to atmospheric greenhouse gas budgets. Ebullition is key with important sensitivity to the formation of hydrate skins and oil coatings, high-pressure solubility, bubble size and bubble plume processes. Bubble ROV tracking studies showed survival to near thermocline depths. Studies with a numerical bubble propagation model demonstrated that consideration of structure I hydrate skins transported most methane only to mid-water column depths. Instead, consideration of structure II hydrates, which are stable to far shallower depths and appropriate for natural gas mixtures, allows bubbles to survive to far shallower depths. Moreover, model predictions of vertical methane and alkane profiles and bubble size evolution were in better agreement with observations after consideration of structure II hydrate properties as well as an improved implementation of plume properties, such as currents. These results demonstrate the importance of correctly incorporating bubble hydrate processes in efforts to predict the impact of deepsea seepage as well as to understand the fate of bubble-transported oil and methane from deepsea pipeline leaks and well blowouts. Application to the DWH spill demonstrated the importance of deepsea processes to the fate of spilled subsurface oil. Because several of these parameters vary temporally (bubble flux, currents, temperature), sensitivity studies indicate the importance of real-time monitoring data.

  10. Bubble Bed Bioreactor Malfunctions Revealed by Computational Flow Simulation Analysis

    Czech Academy of Sciences Publication Activity Database

    Fialová, Marie; Staykov, P.; Vlaev, S. D.

    Bratislava: Slovak University of Technology, 2009 - (Markoš, J.), s. 351 ISBN 978-80-227-3072-3. [International Conference of Slovak Society of Chemical Engineering /36./. Tatranské Matliare (SK), 25.05.2009-29.05.2009] R&D Projects: GA ČR GA104/07/1110 Institutional research plan: CEZ:AV0Z40720504 Keywords : bubble column bioreactor * gas holdup * CFD Subject RIV: CI - Industrial Chemistry, Chemical Engineering

  11. Electrowetting of a soap bubble

    CERN Document Server

    Arscott, Steve

    2013-01-01

    A proof-of-concept demonstration of the electrowetting-on-dielectric of a sessile soap bubble is reported here. The bubbles are generated using a commercial soap bubble mixture - the surfaces are composed of highly doped, commercial silicon wafers covered with nanometre thick films of Teflon. Voltages less than 40V are sufficient to observe the modification of the bubble shape and the apparent bubble contact angle. Such observations open the way to inter alia the possibility of bubble-transport, as opposed to droplet-transport, in fluidic microsystems (e.g. laboratory-on-a-chip) - the potential gains in terms of volume, speed and surface/volume ratio are non-negligible.

  12. Tools for Reactive Distillation Column Design: Graphical and Stage-to-Stage Computation Methods

    DEFF Research Database (Denmark)

    Sanchez Daza, O.; Cisneros, Eduardo Salvador P.; Hostrup, Martin;

    2001-01-01

    Based on the element mass balance concept, a graphical design method and a stage-to-stage multicomponent design method for reactive distillation columns have been developed. For distillation columns comprising reactive and non-reactive stages, a simple design strategy based on reactive and non......-reactive bubble point calculations is proposed. This strategy tracks the conversion and temperature between the feed and the end stages of the column. An illustrative example highlights the verification of the design strategy through rigorous simulation....

  13. Cost-benefit of the bubble tower concept as a containment passive safety system

    International Nuclear Information System (INIS)

    Containment system integrity for both PWRs and BWRs can be assured by passive measures highlighted the use of an accessory Bubble Tower. The utilization of the Bubble Tower precludes the possibility of containment overpressurization. From the thermodynamic standpoint, the Bubble Tower is simply water column of about 120 ft. height attached to the containment and connected to the air space above the suppression pool of a BWR, or a PWR In-containment Refueling Water Storage Tank. From the radiological protection standpoint, the Bubble Tower is a water column sufficient to effect decontamination factors of at least 100 for nuclide species other than the noble gases, and with the addition of organic solubilizers sufficient to effect decontamination factors of at least 10 iodides and at least 100 for other nuclide species. When containment steam or noncondensable gas passes through the Bubble Tower, a significant fraction of the radionuclides is absorbed by the water column. When a cost-benefit dose evaluation is performed relative to the utilization of a Bubble Tower, even under conditions where the dollars per man-rem is taken as $1000, the results are favorable. They are substantially more favorable when the dollars per man-rem is taken as $5000 or $10,000 as are the current trends. (author)

  14. Rational Bubbles in Stock Prices?

    OpenAIRE

    Behzad T. Diba; Grossman, Herschel I.

    1985-01-01

    This paper reports empirical tests for the existence of rational bubbles in stock prices. The analysis focuses on a familiar model that defines market fundamentals to be the expected present value of dividends, discounted at a constantrate, and defines a rational bubble to be a self-confirming divergence of stock prices from market fundamentals in response to extraneous variables. The tests are based on the theoretical result that, if rational bubbles exist, time series obtained by differenci...

  15. Rational Asset Pricing Bubbles Revisited

    OpenAIRE

    Jan Werner

    2012-01-01

    Price bubble arises when the price of an asset exceeds the asset's fundamental value, that is, the present value of future dividend payments. The important result of Santos and Woodford (1997) says that price bubbles cannot exist in equilibrium in the standard dynamic asset pricing model with rational agents as long as assets are in strictly positive supply and the present value of total future resources is finite. This paper explores the possibility of asset price bubbles when either one of ...

  16. Interactions of the Infrared bubble N4 with the surroundings

    CERN Document Server

    Liu, Hong-Li; Wu, Yuefang; Yuan, Jing-Hua; Liu, Tie; Dubner, G; Paron, S; Ortega, M E; Molinari, Sergio; Huang, Maohai; Zavagno, Annie; Samal, Manash R; Huang, Ya-Fang; Zhang, Si-Ju

    2016-01-01

    The physical mechanisms that induce the transformation of a certain mass of gas in new stars are far from being well understood. Infrared bubbles associated with HII regions have been considered to be a good sample to investigate triggered star formation. In this paper we report on the investigation of the dust properties of the infrared bubble N4 around the HII region G11.898+0.747, analyzing its interaction with the surroundings and star formation histories therein, aiming at determining the possibility of star formation triggered by the expansion of the bubble. Using Herschel PACS and SPIRE images with a wide wavelength coverage, we reveal the dust properties over the entire bubble. Meanwhile, we are able to identify six dust clumps surrounding the bubble, with a mean size of 0.50 pc, temperature of about 22 K, mean column density of 1.7 $\\times10^{22}$ cm$^{-2}$, mean volume density of about 4.4 $\\times10^{4}$ cm$^{-3}$, and a mean mass of 320 $M_{\\odot}$. In addition, from PAH emission seen at 8 $\\mu$m, ...

  17. Nuclear reactor fuel elements

    International Nuclear Information System (INIS)

    A nuclear reactor fuel element comprising a column of vibration compacted fuel which is retained in consolidated condition by a thimble shaped plug. The plug is wedged into gripping engagement with the wall of the sheath by a wedge. The wedge material has a lower coefficient of expansion than the sheath material so that at reactor operating temperature the retainer can relax sufficient to accommodate thermal expansion of the column of fuel. (author)

  18. Droplets, Bubbles and Ultrasound Interactions.

    Science.gov (United States)

    Shpak, Oleksandr; Verweij, Martin; de Jong, Nico; Versluis, Michel

    2016-01-01

    The interaction of droplets and bubbles with ultrasound has been studied extensively in the last 25 years. Microbubbles are broadly used in diagnostic and therapeutic medical applications, for instance, as ultrasound contrast agents. They have a similar size as red blood cells, and thus are able to circulate within blood vessels. Perfluorocarbon liquid droplets can be a potential new generation of microbubble agents as ultrasound can trigger their conversion into gas bubbles. Prior to activation, they are at least five times smaller in diameter than the resulting bubbles. Together with the violent nature of the phase-transition, the droplets can be used for local drug delivery, embolotherapy, HIFU enhancement and tumor imaging. Here we explain the basics of bubble dynamics, described by the Rayleigh-Plesset equation, bubble resonance frequency, damping and quality factor. We show the elegant calculation of the above characteristics for the case of small amplitude oscillations by linearizing the equations. The effect and importance of a bubble coating and effective surface tension are also discussed. We give the main characteristics of the power spectrum of bubble oscillations. Preceding bubble dynamics, ultrasound propagation is introduced. We explain the speed of sound, nonlinearity and attenuation terms. We examine bubble ultrasound scattering and how it depends on the wave-shape of the incident wave. Finally, we introduce droplet interaction with ultrasound. We elucidate the ultrasound-focusing concept within a droplets sphere, droplet shaking due to media compressibility and droplet phase-conversion dynamics. PMID:26486337

  19. Diamagnetic "bubble" equilibria in linear traps

    Science.gov (United States)

    Beklemishev, A. D.

    2016-08-01

    The plasma equilibrium in a linear trap at β ≈ 1 (or above the mirror-instability threshold) under the topology-conservation constraint evolves into a kind of diamagnetic "bubble." This can take two forms: either the plasma body greatly expands in radius while containing the same magnetic flux, or, if the plasma radius is limited, the plasma distribution across flux-tubes changes, so that the same cross-section contains a greatly reduced flux. If the magnetic field of the trap is quasi-uniform around its minimum, the bubble can be made roughly cylindrical, with radius much larger than the radius of the corresponding vacuum flux-tube, and with non-paraxial ends. Then the effective mirror ratio of the diamagnetic trap becomes very large, but the cross-field transport increases. The confinement time can be found from solution of the system of equilibrium and transport equations and is shown to be τ E ≈ √{ τ ∥ τ ⊥ } . If the cross-field confinement is not too degraded by turbulence, this estimate in principle allows construction of relatively compact fusion reactors with lengths in the range of a few tens of meters. In many ways, the described diamagnetic confinement and the corresponding reactor parameters are similar to those claimed by the field-reversed configurations.

  20. Liquid entrainment by an expanding core disruptive accident bubble--a Kelvin/Helmholtz phenomenon

    International Nuclear Information System (INIS)

    The final stage of a postulated energetic core disruptive accident (CDA) in a liquid metal fast breeder reactor is believed to involve the expansion of a high-pressure core-material bubble against the overlying pool of sodium. Some of the sodium will be entrained by the CDA bubble which may influence the mechanical energy available for damage to the reactor vessel. The following considerations of liquid surface instability indicate that the Kelvin-Helmholtz (K-H) mechanism is primarily responsible for liquid entrainment by the expanding CDA bubble. First, an instability analysis is presented which shows that the K-H mechanism is faster than the Taylor acceleration mechanism of entrainment at the high fluid velocities expected within the interior of the expanding CDA bubble. Secondly, a new model of liquid entrainment by the CDA bubble is introduced which is based on spherical-core-vortex motion and entrainment via the K-H instability along the bubble surface. The model is in agreement with new experimental results presented here on the reduction of nitrogen-gas-simulant CDA bubble work potential. Finally, a one-dimensional air-over-water parallel flow experiment was undertaken which demonstrates that the K-H instability results in sufficiently rapid and fine liquid atomization to account for observed CDA gas-bubble work reductions. An important byproduct of the theoretical and experimental work is that the liquid entrainment rate is well described by the Ricou-Spalding entrainment law

  1. Bubble Coalescence: Effect of Bubble Approach Velocity and Liquid Viscosity

    Czech Academy of Sciences Publication Activity Database

    Orvalho, Sandra; Růžička, Marek; Olivieri, G.; Marzocchella, A.

    2015-01-01

    Roč. 134, SEP 29 (2015), s. 205-216. ISSN 0009-2509 R&D Projects: GA MŠk(CZ) LD13018 Institutional support: RVO:67985858 Keywords : bubble coalescence * bubble approach velocity * liquid viscosity Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 2.337, year: 2014

  2. Dynamic Bubble Behaviour during Microscale Subcooled Boiling

    Institute of Scientific and Technical Information of China (English)

    WANG Hao; PENG Xiao-Feng; David M.Christopher

    2005-01-01

    @@ Bubble cycles, including initiation, growth and departure, are the physical basis of nucleate boiling. The presentinvestigation, however, reveals unusual bubble motions during subcooled nucleate boiling on microwires 25 orl00μm in diameter. Two types of bubble motions, bubble sweeping and bubble return, are observed in theexperiments. Bubble sweeping describes a bubble moving back and forth along the wire, which is motion parallelto the wire. Bubble return is the bubble moving back to the wire after it has detached or leaping above thewire. Theoretical analyses and numerical simulations are conducted to investigate the driving mechanisms forboth bubble sweeping and return. Marangoni flow from warm to cool regions along the bubble interface is foundto produce the shear stresses needed to drive these unusual bubble movements.

  3. PRTR ion exchange vault column sampling

    International Nuclear Information System (INIS)

    This report documents ion exchange column sampling and Non Destructive Assay (NDA) results from activities in 1994, for the Plutonium Recycle Test Reactor (PRTR) ion exchange vault. The objective was to obtain sufficient information to prepare disposal documentation for the ion exchange columns found in the PRTR Ion exchange vault. This activity also allowed for the monitoring of the liquid level in the lower vault. The sampling activity contained five separate activities: (1) Sampling an ion exchange column and analyzing the ion exchange media for purpose of waste disposal; (2) Gamma and neutron NDA testing on ion exchange columns located in the upper vault; (3) Lower vault liquid level measurement; (4) Radiological survey of the upper vault; and (5) Secure the vault pending waste disposal

  4. Dynamic of vapor bubble growth in fields of variable pressure

    International Nuclear Information System (INIS)

    A mathematical model for the description of the growth from an initial nucleus of a vapor bubble imersed in liquid, subjected to a loss of pressure is presented. The model is important for analysing LOCA (Loss of Coolant Acident) in P.W.R. type reactors. Several simplifications were made in the phenomenum governing equations. With such simplifications the heat diffusion equation became the determining factor for the bubble growth, and the problem was reduced to solve the heat diffusion equation for semi infinite solid whose surface temperature is a well known function of time (it is supposed that the surface temperature is equal to the saturation temperature of the liquid at the system pressure at a given moment). The model results in an analytical expression for the bubble radius as a function of time. Comparisons with experimental data and previous models were made, with reasonable agreement. (author)

  5. Heat transfer between immiscible liquids enhanced by gas bubbling

    Science.gov (United States)

    Greene, G. A.; Schwarz, C. E.; Klages, J.; Klein, J.

    1982-08-01

    The phenomena of core-concrete interactions impact upon containment integrity of light water reactors (LWR) following postulated complete meltdown of the core by containment pressurization, production of combustible gases, and basemat penetration. Experiments were performed with nonreactor materials to investigate one aspect of this problem, heat transfer between overlying immiscible liquids whose interface is disturbed by a transverse non-condensable gas flux emanating from below. Hydrodynamic studies were performed to test a criterion for onset of entrainment due to bubbling through the interface and subsequent heat transfer studies were performed to assess the effect of bubbling on interfacial heat transfer rates, both with and without bubble induced entrainment. Non entraining interfacial heat transfer data with mercury-water/oil fluid pairs were observed to be bounded from below within a factor of two to three by the Szekeley surface renewal heat transfer model.

  6. Optical behavior of surface bubbles

    Science.gov (United States)

    Straulino, Samuele; Gambi, Cecilia M. C.; Molesini, Giuseppe

    2015-11-01

    The observation of diamond-like light spots produced by surface bubbles obliquely illuminated is reported. The phenomenon is discussed in terms of geometrical optics, and an explanation is provided attributing the effect to the astigmatism introduced by the deformation of the liquid surface surrounding the bubble. An essential ray tracing program is outlined and used to reconstruct the observed phenomenon numerically.

  7. Bubble chamber: colour enhanced tracks

    CERN Multimedia

    1998-01-01

    This artistically-enhanced image of real particle tracks was produced in the Big European Bubble Chamber (BEBC). Liquid hydrogen is used to create bubbles along the paths of the particles as a piston expands the medium. A magnetic field is produced in the detector causing the particles to travel in spirals, allowing charge and momentum to be measured.

  8. Bubble coalescence in breathing DNA

    DEFF Research Database (Denmark)

    Novotný, Tomas; Pedersen, Jonas Nyvold; Ambjörnsson, Tobias; Hansen, Mikael Sonne; Metzler, Ralf

    2007-01-01

    We investigate the coalescence of two DNA bubbles initially located at weak segments and separated by a more stable barrier region in a designed construct of double-stranded DNA. The characteristic time for bubble coalescence and the corresponding distribution are derived, as well as the distribu...

  9. Bubble Formation in Basalt-like Melts

    DEFF Research Database (Denmark)

    Jensen, Martin; Keding, Ralf; Yue, Yuanzheng

    2011-01-01

    The effect of the melting temperature on bubble size and bubble formation in an iron bearing calcium aluminosilicate melt is studied by means of in-depth images acquired by optical microscopy. The bubble size distribution and the total bubble volume are determined by counting the number of bubbles...... species. Mass spectroscopy analysis of gases liberated during heating of the glass reveals that small bubbles contain predominantly CH4, CO and CO2, whereas large bubbles bear N2, SO2 and H2S. The methodology utilised in this work can, besides mapping the bubbles in a glass, be applied to shed light on...

  10. Natural convection type reactor

    International Nuclear Information System (INIS)

    In a natural convection type nuclear reactor, recycling flow rate of coolants is increased and the amount of entrained bubbles are increased as the driving force is increased, so that bubbles are not separated completely even if a stagnation region is disposed. Then, a space opened only at the upper portion is disposed at the outer circumference of the upper end of a riser for storing overflown coolants temporarily. The flow of coolants incorporating steam bubbles uprising in the riser turns into the horizontal direction at the upper end of the riser wall and flows into the coolant reservoir. In the coolant reservoir, since the momentum of the coolants is lost and the flow is stagnated, the bubbles are easily released to the upper space. Coolants, after releasing the bubbles, further overflow and descend in the downcomer. Then, the bubbles can be separated undergoing no influence of the driving force caused as the sum of the uprising force in the riser and the water head pressure in the downcomer, to prevent increase of carry under due to increase of the driving force. (N.H.)

  11. The Milky Way Project and ATLASGAL: The Distribution and Physical Properties of Cold Clumps Near Infrared Bubbles

    Science.gov (United States)

    Kendrew, Sarah; Beuther, Henrik; Simpson, Robert; Csengeri, Timea; Wienen, Marion; Lintott, Chris. J.; Povich, Matthew S.; Beaumont, Chris; Schuller, Frédéric

    2016-07-01

    We present a statistical study of the distribution and physical properties of cold, dense material in and around the inner Galactic Plane near-infrared bubbles as cataloged by the Milky Way Project citizen scientists. Using data from the Atacama Pathfinder Experiment (APEX) Telescope Large Area Survey of the Galaxy 870 μm survey, we show that 48 ± 2% of all cold clumps in the studied survey region (| l| ≤slant 65^\\circ , | b| ≤slant 1^\\circ ) are found in close proximity to a bubble, and 25 ± 2% appear directly projected toward a bubble rim. A two-point correlation analysis confirms the strong correlation of massive cold clumps with expanding bubbles. It shows an overdensity of clumps along bubble rims that grows with increasing bubble size, which shows how interstellar medium material is reordered on large scales by bubble expansion around regions of massive star formation. The highest column density clumps appear to be resistent to the expansion, remaining overdense toward the bubbles’ interior rather than being swept up by the expanding edge. Spectroscopic observations in ammonia show that cold dust clumps near bubbles appear to be denser, hotter, and more turbulent than those in the field, offering circumstantial evidence that bubble-associated clumps are more likely to be forming stars. These observed differences in physical conditions persist beyond the region of the bubble rims.

  12. Observation of bubble formation in water during microwave irradiation by dynamic light scattering

    Science.gov (United States)

    Asakuma, Yusuke; Munenaga, Takuya; Nakata, Ryosuke

    2015-10-01

    A microwave reactor was designed for in situ observation of nano- and micro-bubbles, and size profiles during and after irradiation were measured with respect to irradiation power and time. Bubble formation in water during irradiation was observed even at temperatures below the boiling point of water. The maximum size strongly depended on radiation power and time, even at a given temperature. Nano-particles in the dispersion medium were found to play an important role in achieving more stable nucleation of bubbles around particles, and stable size distributions were obtained from clear autocorrelation by a dynamic light scattering system. Moreover, a combination of microwave induction heating and the addition of nano-particles to the dispersion medium can prevent heterogeneous nucleation of bubbles on the cell wall. Quantitative nano-bubble size profiles obtained by in situ observation provide useful information regarding microwave-based industrial processes for nano-particle production.

  13. Experimental investigation on characteristic of entrained bubbles due to surface vortex

    International Nuclear Information System (INIS)

    According to the compact sizing of reactor vessel, gas entrainment at the free surface of sodium coolant becomes one of the significant issues in the latest sodium-cooled fast reactor design. In the present study, some basic experiments for gas entrainment due to surface vortices were performed in order to obtain the fundamental knowledge about entrained bubbles. The distribution of bubble diameters was obtained from an image processing technique from the images. In addition to that, velocity field and surface shape of gas core were measured to grasp the influences of the local velocity field on the gas core shape and detached bubbles. The results showed that the mean equivalent diameters of bubbles were varied from 1.34 to 2.06 mm in the range of present experimental conditions. (author)

  14. Strings on Bubbling Geometries

    CERN Document Server

    Lin, Hai; Shock, Jonathan P

    2010-01-01

    We study gauge theory operators which take the form of a product of a trace with a Schur polynomial, and their string theory duals. These states represent strings excited on bubbling AdS geometries which are dual to the Schur polynomials. These geometries generically take the form of multiple annuli in the phase space plane. We study the coherent state wavefunction of the lattice, which labels the trace part of the operator, for a general Young tableau and their dual description on the droplet plane with a general concentric ring pattern. In addition we identify a density matrix over the coherent states on all the geometries within a fixed constraint. This density matrix may be used to calculate the entropy of a given ensemble of operators. We finally recover the BMN string spectrum along the geodesic near any circle from the ansatz of the coherent state wavefunction.

  15. Anatomy of bubbling solutions

    CERN Document Server

    Skenderis, Kostas

    2007-01-01

    We present a comprehensive analysis of holography for the bubbling solutions of Lin-Lunin-Maladacena. These solutions are uniquely determined by a coloring of a 2-plane, which was argued to correspond to the phase space of free fermions. We show that in general this phase space distribution does not determine fully the 1/2 BPS state of N=4 SYM that the gravitational solution is dual to, but it does determine it enough so that vevs of all single trace 1/2 BPS operators in that state are uniquely determined to leading order in the large N limit. These are precisely the vevs encoded in the asymptotics of the LLM solutions. We extract these vevs for operators up to dimension 4 using holographic renormalization and KK holography and show exact agreement with the field theory expressions.

  16. Methanotrophic microbial communities associated with bubble plumes above gas seeps in the Black Sea

    OpenAIRE

    Carsten J Schubert; Durisch-Kaiser, Edith; Holzner, Christian P.; Klauser, Lucia; Wehrli, Bernhard; Schmale, Oliver; Greinert, Jens; McGinnis, Daniel Frank; De Batist, Marc; Kipfer, Rolf

    2006-01-01

    Bubbles evolving from active gas seeps can be traced by hydroacoustic imaging up to 1000 m high in the Black Sea water column. Although methane concentrations are not distinguishable between the water column above the deep seep and reference sites, atmospheric noble gas measurements clearly show the constant input of gases (mainly methane) via seepage into the Black Sea. Archaea (ANME-1, ANME-2) and methanotrophic bacteria detected with specific 16S rRNA-targeted oligonucleotide probes are re...

  17. Doughnut-shaped soap bubbles

    Science.gov (United States)

    Préve, Deison; Saa, Alberto

    2015-10-01

    Soap bubbles are thin liquid films enclosing a fixed volume of air. Since the surface tension is typically assumed to be the only factor responsible for conforming the soap bubble shape, the realized bubble surfaces are always minimal area ones. Here, we consider the problem of finding the axisymmetric minimal area surface enclosing a fixed volume V and with a fixed equatorial perimeter L . It is well known that the sphere is the solution for V =L3/6 π2 , and this is indeed the case of a free soap bubble, for instance. Surprisingly, we show that for V caps, but is rather a toroidal surface. Practically, a doughnut-shaped bubble is known to be ultimately unstable and, hence, it will eventually lose its axisymmetry by breaking apart in smaller bubbles. Indisputably, however, the topological transition from spherical to toroidal surfaces is mandatory here for obtaining the global solution for this axisymmetric isoperimetric problem. Our result suggests that deformed bubbles with V <α L3/6 π2 cannot be stable and should not exist in foams, for instance.

  18. Plane shock wave interaction with a cylindrical water column

    Science.gov (United States)

    Sembian, S.; Liverts, M.; Tillmark, N.; Apazidis, N.

    2016-05-01

    A complex system of waves propagating inside a water column due to the impact of plane shock wave is investigated both experimentally and numerically. Flow features, such as, focusing of expansion waves generating large negative pressure, nucleation of cavitation bubbles, and a re-circulation zone are observed and discussed qualitatively and quantitatively. Experiments are conducted on a 22 mm diametrical water column hit by shock waves with Mach numbers 1.75 and 2.4 in a newly constructed exploding wire facility. A new technique to create a properly shaped, repeatable, large diameter water column with straight walls is presented. Qualitative features of the flow are captured using the shadowgraph technique. With the aid of numerical simulations the wave motions inside the column are analyzed; the spatial location of the expansion wave focusing point and the corresponding negative peak pressures is estimated.

  19. Aerosol impaction and critical trajectories in oscillating bubbles

    International Nuclear Information System (INIS)

    When gas containing aerosol is subject to rapid acceleration, the failure of the aerosol to follow the gas motion can lead to impaction into walls. This problem arises in oscillating bubbles which could be formed under sodium during a hypothetical core disruptive accident in a liquid-metal-cooled fast breeder reactor, and the calculation of aerosol trajectories and wall impaction has been considered by previous authors. Here, we introduce a powerful technique to perform such calculations based on critical trajectories. (author)

  20. Numerical Modeling and Prediction of Bubbling Fluidized Beds

    OpenAIRE

    England, Jonas Andrew

    2011-01-01

    Numerical modeling and prediction techniques are used to determine pressure drop, minimum fluidization velocity and segregation for bubbling fluidized beds. The computational fluid dynamics (CFD) code Multiphase Flow with Interphase eXchange (MFIX) is used to study a two-stage reactor geometry with a binary mixture. MFIX is demonstrated to accurately predict pressure drop versus inlet gas velocity for binary mixtures. A new method is developed to predict the pressure drop versus inlet gas v...

  1. Bubble Growth in Lunar Basalts

    Science.gov (United States)

    Zhang, Y.

    2009-05-01

    Although Moon is usually said to be volatile-"free", lunar basalts are often vesicular with mm-size bubbles. The vesicular nature of the lunar basalts suggests that they contained some initial gas concentration. A recent publication estimated volatile concentrations in lunar basalts (Saal et al. 2008). This report investigates bubble growth on Moon and compares with that on Earth. Under conditions relevant to lunar basalts, bubble growth in a finite melt shell (i.e., growth of multiple regularly-spaced bubbles) is calculated following Proussevitch and Sahagian (1998) and Liu and Zhang (2000). Initial H2O content of 700 ppm (Saal et al. 2008) or lower is used and the effect of other volatiles (such as carbon dioxide, halogens, and sulfur) is ignored. H2O solubility at low pressures (Liu et al. 2005), concentration-dependent diffusivity in basalt (Zhang and Stolper 1991), and lunar basalt viscosity (Murase and McBirney 1970) are used. Because lunar atmospheric pressure is essentially zero, the confining pressure on bubbles is completely supplied by the overlying magma. Due to low H2O content in lunar basaltic melt (700 ppm H2O corresponds to a saturation pressure of 75 kPa), H2O bubbles only grow in the upper 16 m of a basalt flow or lake. A depth of 20 mm corresponds to a confining pressure of 100 Pa. Hence, vesicular lunar rocks come from very shallow depth. Some findings from the modeling are as follows. (a) Due to low confining pressure as well as low viscosity, even though volatile concentration is very low, bubble growth rate is extremely high, much higher than typical bubble growth rates in terrestrial melts. Hence, mm-size bubbles in lunar basalts are not strange. (b) Because the pertinent pressures are so low, bubble pressure due to surface tension plays a main role in lunar bubble growth, contrary to terrestrial cases. (c) Time scale to reach equilibrium bubble size increases as the confining pressure increases. References: (1) Liu Y, Zhang YX (2000) Earth

  2. Sonochemistry and the acoustic bubble

    CERN Document Server

    Grieser, Franz; Enomoto, Naoya; Harada, Hisashi; Okitsu, Kenji; Yasui, Kyuichi

    2015-01-01

    Sonochemistry and the Acoustic Bubble provides an introduction to the way ultrasound acts on bubbles in a liquid to cause bubbles to collapse violently, leading to localized 'hot spots' in the liquid with temperatures of 5000° celcius and under pressures of several hundred atmospheres. These extreme conditions produce events such as the emission of light, sonoluminescence, with a lifetime of less than a nanosecond, and free radicals that can initiate a host of varied chemical reactions (sonochemistry) in the liquid, all at room temperature. The physics and chemistry behind the p

  3. Development of cesium trapper and single-gas-bubble injector into sodium pool

    International Nuclear Information System (INIS)

    On the core disruptive accident in the sodium cooled fast breeder reactor, in fuel pins the cesium fission product with a high hazard is transferred to the sodium coolant together with noble gas including fission product, and the cesium accumulates on the cover gas area because of its low migration rate to sodium. The high temperature and high pressure in the cover gas due to the decay heat of fission products including cesium cause the leakage of cesium to the outside of reactor vessel. However the exact migration rate of cesium to sodium has not been reported because of difficulty on the evaluation of the interfacial area of large gas bubble (Minges et al., 1986). In this study, we developed a cesium trapper composed of β”-alumina cylindrical container and a single-gas-bubble injector without wettability. We confirmed that a single argon gas bubble was steadily produced in our injector. Bhaga proposed the bubble shape region map, which correlates the bubble shape with Reynolds number, Eotvos number and Morton number of the bubble ejected into sodium pool. The bubble shapes were estimated to be always ellipsoidal. We could successfully confirmed that the liquid sodium can be separated from liquid sodium cesium mixture by using β”-alumina, whose separation rate was found to be calculated by the Faraday's law of electrolysis. (author)

  4. Slender CRC Columns

    DEFF Research Database (Denmark)

    Aarup, Bendt; Jensen, Lars Rom; Ellegaard, Peter

    2005-01-01

    CRC is a high-performance steel fibre reinforced concrete with a typical compressive strength of 150 MPa. Design methods for a number of structural elements have been developed since CRC was invented in 1986, but the current project set out to further investigate the range of columns for which...... current design guides can be used. The columns tested had a slenderness varying from 1.11 to 12.76 and a reinforcement ratio (area of rebar to area of concrete) ranging from 0 to 8.8 %. A total of 77 tests were carried out - 61 columns were tested in ambient conditions and 16 columns were tested in...... standard fire conditions. The tests showed good correlation between test results and results calculated according to established deisgn guides. The fire tests demonstrate that the load capacity of slender columns can be reduced very quickly due to thermal stresses and a reduction of stiffness - also in...

  5. A Summary of Shock/Soap Bubble Interactions Performed at the SWRC, Tohoku University

    Science.gov (United States)

    Yamamoto, H.; Igra, D.; Takayama, Kazuyoshi

    A summary of experiments of shock wave interactions with spherical soap bubbles and cylindrical soap columns filled with helium performed in the Shock Wave Research Center at Tohoku University is presented. Sequential holographic interferograms of soap bubbles impinged by small-scale blast waves created by explosion of 10 mg weight silver azide pellets are presented. The standoff distance between micro-explosives and the bubbles center is about 40 mm and the shock overpressure was about 2 MPa. Helium filled soap columns of 40 mm diameter and 60 mm in height were placed in a 60 mm x 150 mm shock tube. Their interaction with shock wave was intensively visualized by using holographic interferogram at atmospheric conditions. It is found that the irregular interfacial deformation observed are just three-dimensional vortices viewed from the side

  6. The Housing Bubble Fact Sheet

    OpenAIRE

    Dean Baker

    2005-01-01

    This paper explains the basic facts about the current housing market. It lays out the evidence that the rise in housing prices constitutes a housing bubble - and explains what can be expected when it inevitably collapses.

  7. Bubble bean bags in shampoo

    OpenAIRE

    Kundu, Anup; Sharma, Chandan; Das, Gargi; Harikrishnan, G.

    2011-01-01

    In these fluid dynamics videos, we, for the first time, show various interactions of a 'Taylor bubble' with their smaller and differently, shaped counterparts, in a shear thinning, non-Newtonian fluid, confined in a narrow channel.

  8. Helium bubbles in UO2

    International Nuclear Information System (INIS)

    A certain part of helium generated in MOX fuel could form additional bubbles in fuel pellets as a result of the combination of radiation defects and high temperature. In the present study, the helium infusion treatments were conducted at high temperature with highly pressurized helium for both polycrystalline UO2 fragments and hyperstoichiometric single crystal UO2+x particles. Annealing tests for polycrystalline UO2 were followed by the helium infusion treatment to evaluate formation of helium bubble. In case of as helium-infused polycrystalline sample, it was confirmed that helium bubbles were formed after slight oxidative annealing at more than 1573K. On the other hand, the cavity observed in as-helium-infused single crystal sample grew up to form a negative crystal. Formation mechanism of helium bubble and negative crystal were discussed. (author)

  9. Transient bubbles, bublets and breakup

    Science.gov (United States)

    Keen, Giles; Blake, John

    1999-11-01

    The non-spherical nature of the collapse of bubbles has important ramifications in many practical situations such as ultrasonic cleaning, tanning of leather, and underwater explosions. In particular the high speed liquid jet that can thread a collapsing bubble is central to the functional performance. An impressive photographic record of a liquid jet was obtained by Crum using a bubble situated in the vicinity of a platform oscillating vertically at a frequency of 60 Hz. A boundary integral method is used to model this situation and is found to closely mimic some of the observations. However, a slight variation of parameters or a change in the phase of the driving frequency can lead to dramatically different bubble behaviour, a feature also observed by Crum.

  10. Pulling bubbles from a bath

    Science.gov (United States)

    Kao, Justin C. T.; Blakemore, Andrea L.; Hosoi, A. E.

    2010-06-01

    Deposition of bubbles on a wall withdrawn from a liquid bath is a phenomenon observed in many everyday situations—the foam lacing left behind in an emptied glass of beer, for instance. It is also of importance to the many industrial processes where uniformity of coating is desirable. We report work on an idealized version of this situation, the drag-out of a single bubble in Landau-Levich-Derjaguin flow. We find that a well-defined critical wall speed exists, separating the two regimes of bubble persistence at the meniscus and bubble deposition on the moving wall. Experiments show that this transition occurs at Ca∗˜Bo0.73. A similar result is obtained theoretically by balancing viscous stresses and gravity.

  11. Modeling the Local Bubble

    Science.gov (United States)

    Cox, D. P.

    Modeling the Local Bubble is one of those activities fraught with danger. It is very easy to be too naive, to fail to consider the dependence of the model on assumptions about the nearby ambient state, or the likelihood of such a structure. It is similarly easy to become so caught up in the details of the vicinity that it is unclear where to begin a necessarily idealized modeling effort. And finally, it is important to remember that the data we have may in some cases be lying to us, and that we have not yet learned to read their facial expressions quite carefully enough. That said, I've tried in this paper to be helpful to those who may wish to take the risks. I surveyed the very most basic stories that the data seem to tell, and pointed out the standard coincidences that may be telling us a lot about what is happening, but may turn out once again to have been just coincidences. I've described 5 distinct conceptions that in one flavor or another pretty well survey the collection of mental images that have so far been carried by those who've attempted models. One may be right, or something entirely different may be more appropriate. It's at least vital to realize that a conception comes first, followed by a simplified model of details. I've also included a long list of questions directed at observers. Some have partial answers, some one wouldn't know today quite how to approach. But it is a list that students of the soft x-ray background, interstellar absorption lines, possible instrumentation, and the heliosphere may wish to review from time to time, just to see whether they can figure out how to be more helpful. There is another list for modelers, things the models must address, however-so-flimsily if necessary, because there are strong observational constraints (and stronger ones coming) on what can and cannot be present in the local ISM. To that I've added a few remarks concerning x-ray emission coming from beyond the Local Bubble, and another few on how x

  12. Mechanisms of single bubble cleaning.

    Science.gov (United States)

    Reuter, Fabian; Mettin, Robert

    2016-03-01

    The dynamics of collapsing bubbles close to a flat solid is investigated with respect to its potential for removal of surface attached particles. Individual bubbles are created by nanosecond Nd:YAG laser pulses focused into water close to glass plates contaminated with melamine resin micro-particles. The bubble dynamics is analysed by means of synchronous high-speed recordings. Due to the close solid boundary, the bubble collapses with the well-known liquid jet phenomenon. Subsequent microscopic inspection of the substrates reveals circular areas clean of particles after a single bubble generation and collapse event. The detailed bubble dynamics, as well as the cleaned area size, is characterised by the non-dimensional bubble stand-off γ=d/Rmax, with d: laser focus distance to the solid boundary, and Rmax: maximum bubble radius before collapse. We observe a maximum of clean area at γ≈0.7, a roughly linear decay of the cleaned circle radius for increasing γ, and no cleaning for γ>3.5. As the main mechanism for particle removal, rapid flows at the boundary are identified. Three different cleaning regimes are discussed in relation to γ: (I) For large stand-off, 1.8flows touch down onto the substrate and remove particles without significant contact of the gas phase. (II) For small distances, γflows at the substrate are driven by the jet impact with its subsequent radial spreading, and by the liquid following the motion of the collapsing and rebounding bubble wall. Both flows remove particles. Their relative timing, which depends sensitively on the exact γ, appears to determine the extension of the area with forces large enough to cause particle detachment. (III) At intermediate stand-off, 1.1cleaning mechanisms similar to an effective small γ collapse: particles are removed by the jet flow and the flow induced by the bubble wall oscillation. Furthermore, the observations reveal that the extent of direct bubble gas phase contact to the solid is partially

  13. Ostwald Ripening in Multiple-Bubble Nuclei

    OpenAIRE

    Watanabe, Hiroshi; Suzuki, Masaru; Inaoka, Hajime; Ito, Nobuyasu

    2014-01-01

    The ostwald ripening of bubbles is studied by molecular dynamics simulations involving up to 679 million Lennard-Jones particles. Many bubbles appear after depressurizing a system that is initially maintained in the pure-liquid phase, and the coarsening of bubbles follows. The self-similarity of the bubble-size distribution function predicted by Lifshitz-Slyozov-Wagner theory is directly confirmed. The total number of bubbles decreases asymptotically as $t^{-x}$ with scaling exponent $x$. As ...

  14. Learning the CAPM through Bubbles

    OpenAIRE

    Haim Kedar-Levy

    2004-01-01

    Bubbles are generally considered the outcome of investor irrationality or informational asymmetry, both objectionable in efficient markets with rational investors. We introduce an Intertemporal-CAPM with market clearing between high- and low-risk-averse rational investors who learn the CAPM under incomplete, yet symmetric information. Periodic equilibrium prices make a lognormal price process that nests the classic CAPM with a potential for endogenous bubbles through learning. The absence of ...

  15. Distillation Column Flooding Predictor

    Energy Technology Data Exchange (ETDEWEB)

    George E. Dzyacky

    2010-11-23

    The Flooding Predictor™ is a patented advanced control technology proven in research at the Separations Research Program, University of Texas at Austin, to increase distillation column throughput by over 6%, while also increasing energy efficiency by 10%. The research was conducted under a U. S. Department of Energy Cooperative Agreement awarded to George Dzyacky of 2ndpoint, LLC. The Flooding Predictor™ works by detecting the incipient flood point and controlling the column closer to its actual hydraulic limit than historical practices have allowed. Further, the technology uses existing column instrumentation, meaning no additional refining infrastructure is required. Refiners often push distillation columns to maximize throughput, improve separation, or simply to achieve day-to-day optimization. Attempting to achieve such operating objectives is a tricky undertaking that can result in flooding. Operators and advanced control strategies alike rely on the conventional use of delta-pressure instrumentation to approximate the column’s approach to flood. But column delta-pressure is more an inference of the column’s approach to flood than it is an actual measurement of it. As a consequence, delta pressure limits are established conservatively in order to operate in a regime where the column is never expected to flood. As a result, there is much “left on the table” when operating in such a regime, i.e. the capacity difference between controlling the column to an upper delta-pressure limit and controlling it to the actual hydraulic limit. The Flooding Predictor™, an innovative pattern recognition technology, controls columns at their actual hydraulic limit, which research shows leads to a throughput increase of over 6%. Controlling closer to the hydraulic limit also permits operation in a sweet spot of increased energy-efficiency. In this region of increased column loading, the Flooding Predictor is able to exploit the benefits of higher liquid

  16. ADVANCED COMPUTATIONAL MODEL FOR THREE-PHASE SLURRY REACTORS

    International Nuclear Information System (INIS)

    In this project, an Eulerian-Lagrangian formulation for analyzing three-phase slurry flows in a bubble column was developed. The approach used an Eulerian analysis of liquid flows in the bubble column, and made use of the Lagrangian trajectory analysis for the bubbles and particle motions. The bubble-bubble and particle-particle collisions are included the model. The model predictions are compared with the experimental data and good agreement was found An experimental setup for studying two-dimensional bubble columns was developed. The multiphase flow conditions in the bubble column were measured using optical image processing and Particle Image Velocimetry techniques (PIV). A simple shear flow device for bubble motion in a constant shear flow field was also developed. The flow conditions in simple shear flow device were studied using PIV method. Concentration and velocity of particles of different sizes near a wall in a duct flow was also measured. The technique of Phase-Doppler anemometry was used in these studies. An Eulerian volume of fluid (VOF) computational model for the flow condition in the two-dimensional bubble column was also developed. The liquid and bubble motions were analyzed and the results were compared with observed flow patterns in the experimental setup. Solid-fluid mixture flows in ducts and passages at different angle of orientations were also analyzed. The model predictions were compared with the experimental data and good agreement was found. Gravity chute flows of solid-liquid mixtures were also studied. The simulation results were compared with the experimental data and discussed A thermodynamically consistent model for multiphase slurry flows with and without chemical reaction in a state of turbulent motion was developed. The balance laws were obtained and the constitutive laws established

  17. ADVANCED COMPUTATIONAL MODEL FOR THREE-PHASE SLURRY REACTORS

    Energy Technology Data Exchange (ETDEWEB)

    Goodarz Ahmadi

    2004-10-01

    In this project, an Eulerian-Lagrangian formulation for analyzing three-phase slurry flows in a bubble column was developed. The approach used an Eulerian analysis of liquid flows in the bubble column, and made use of the Lagrangian trajectory analysis for the bubbles and particle motions. The bubble-bubble and particle-particle collisions are included the model. The model predictions are compared with the experimental data and good agreement was found An experimental setup for studying two-dimensional bubble columns was developed. The multiphase flow conditions in the bubble column were measured using optical image processing and Particle Image Velocimetry techniques (PIV). A simple shear flow device for bubble motion in a constant shear flow field was also developed. The flow conditions in simple shear flow device were studied using PIV method. Concentration and velocity of particles of different sizes near a wall in a duct flow was also measured. The technique of Phase-Doppler anemometry was used in these studies. An Eulerian volume of fluid (VOF) computational model for the flow condition in the two-dimensional bubble column was also developed. The liquid and bubble motions were analyzed and the results were compared with observed flow patterns in the experimental setup. Solid-fluid mixture flows in ducts and passages at different angle of orientations were also analyzed. The model predictions were compared with the experimental data and good agreement was found. Gravity chute flows of solid-liquid mixtures were also studied. The simulation results were compared with the experimental data and discussed A thermodynamically consistent model for multiphase slurry flows with and without chemical reaction in a state of turbulent motion was developed. The balance laws were obtained and the constitutive laws established.

  18. Doughnut-shaped soap bubbles

    CERN Document Server

    Preve, Deison

    2015-01-01

    Soap bubbles are thin liquid films enclosing a fixed volume of air. Since the surface tension is typically assumed to be the only responsible for conforming the soap bubble shape, the realized bubble surfaces are always minimal area ones. Here, we consider the problem of finding the axisymmetric minimal area surface enclosing a fixed volume $V$ and with a fixed equatorial perimeter $L$. It is well known that the sphere is the solution for $V=L^3/6\\pi^2$, and this is indeed the case of a free soap bubble, for instance. Surprisingly, we show that for $V<\\alpha L^3/6\\pi^2$, with $\\alpha\\approx 0.21$, such a surface cannot be the usual lens-shaped surface formed by the juxtaposition of two spherical caps, but rather a toroidal surface. Practically, a doughnut-shaped bubble is known to be ultimately unstable and, hence, it will eventually lose its axisymmetry by breaking apart in smaller bubbles. Indisputably, however, the topological transition from spherical to toroidal surfaces is mandatory here for obtainin...

  19. Nuclear reactor

    International Nuclear Information System (INIS)

    Cover gas spaces for primary coolant vessel, such as a reactor container, a pump vessel and an intermediate heat exchanger vessel are in communication with each other by an inverted U-shaped pressure conduit. A transmitter and a receiver are disposed to the pressure conduit at appropriate positions. If vibration frequencies (pressure vibration) from low frequency to high frequency are generated continuously from the transmitter to the inside of the communication pipe, a resonance phenomenon (air-column resonance oscillation) is caused by the inherent frequency or the like of the communication pipe. The frequency of the air-column resonance oscillation is changed by the inner diameter and the clogged state of the pipelines. Accordingly, by detecting the change of the air-column oscillation characteristics by the receiver, the clogged state of the flow channels in the pipelines can be detected even during the reactor operation. With such procedures, steams of coolants flowing entrained by the cover gases can be prevented from condensation and coagulation at a low temperature portion of the pipelines, otherwise it would lead clogging in the pipelines. (I.N.)

  20. Beyond the gas bubble

    International Nuclear Information System (INIS)

    The deliverability issue currently being discussed within the natural gas industry involves both near-term and long-term questions. In the near-term, over the next two or three years, it is probable that the natural gas industry will need to mobilize for much greater levels of investment than have been the experience over the past few years. In the longer-term, it is expected that new opportunities for gas will arise as the nation seeks to meet increasing energy requirements within new environmental constraints. Methane for emissions control, CNG vehicles, expanded gas-fired electricity generation, and increased efficiency of traditional energy services are just a few examples. The issues in the longer-term center on the ability of the gas industry to meet increasing supply requirements reliably and at cost-competitive prices for these markets. This paper begins by reviewing the historical situation of gas deliverability that is the capability of the gas producing and transportation portions of the industry. The delivery system's ability to handle shifts in the centers of consumption and production is discussed, with an emphasis on regional problems of gas deliverability and potential bottlenecks. On the production side, the paper reviews the capability and the required investment necessary to handle an orderly transition to a stable supply and demand balance once the elusive bubble had finally disappeared

  1. Numerical simulation on single bubble rising behavior in liquid metal using moving particle semi-implicit method

    International Nuclear Information System (INIS)

    The gas-lift pump in liquid metal cooling fast reactor (LMFR) is an innovational conceptual design to enhance the natural circulation ability of reactor core. The two-phase flow character of gas-liquid metal makes significant improvement of the natural circulation capacity and reactor safety. In present basic study, the rising behavior of a single nitrogen bubble in five kinds of liquid metals (lead bismuth alloy, liquid kalium, sodium, potassium sodium alloy and lithium lead alloy) was numerically simulated using moving particle semi-implicit (MPS) method. The whole growing process of single nitrogen bubble in liquid metal was captured. The bubble shape and rising speed of single nitrogen bubble in each liquid metal were compared. The comparison between simulation results using MPS method and Grace graphical correlation shows a good agreement. (authors)

  2. Modeling the impediment of methane ebullition bubbles by seasonal lake ice

    Directory of Open Access Journals (Sweden)

    S. Greene

    2014-07-01

    Full Text Available Microbial methane (CH4 ebullition (bubbling from anoxic lake sediments comprises a globally significant flux to the atmosphere, but ebullition bubbles in temperate and polar lakes can be trapped by winter ice cover and later released during spring thaw. This "ice-bubble storage" (IBS constitutes a novel mode of CH4 emission. Before bubbles are encapsulated by downward-growing ice, some of their CH4 dissolves into the lake water, where it may be subject to oxidation. We present field characterization and a model of the annual CH4 cycle in Goldstream Lake, a thermokarst (thaw lake in interior Alaska. We find that summertime ebullition dominates annual CH4 emissions to the atmosphere. Eighty percent of CH4 in bubbles trapped by ice dissolves into the lake water column in winter, and about half of that is oxidized. The ice growth rate and the magnitude of the CH4 ebullition flux are important controlling factors of bubble dissolution. Seven percent of annual ebullition CH4 is trapped as IBS and later emitted as ice melts. In a future warmer climate, there will likely be less seasonal ice cover, less IBS, less CH4 dissolution from trapped bubbles, and greater CH4 emissions from northern lakes.

  3. Measuring and modeling the bubble population produced by an underwater explosion.

    Science.gov (United States)

    Holt, Fred D; Lee Culver, R

    2011-11-01

    Underwater explosions have been studied intensively in the United States since 1941 [e.g., R. H. Cole, Underwater Explosions (Princeton University Press, Princeton, NJ, 1945), pp. 3-13]. Research to date has primarily focused on the initial shock and subsequent pressure waves caused by the oscillations of the "gas-globe" resulting from charge detonation. These phenomena have relatively short timescales (typically less than 2 s). However, after the gas-globe rises through the water column and breaks the surface, there remains behind a cloud of bubbles and perhaps debris from the explosion container which has been markedly less studied. A recent experiment measured the spatial and temporal acoustic response of the bubble cloud resulting from a 13.6 kg PBXN-111 charge detonated at 15.2 m (50 ft) depth. A directional projector was used to propagate linear frequency-modulated (5-65 kHz) and 40 kHz tonal pulses through the bubble cloud. Two hydrophone arrays were positioned so as to measure the energy lost in propagating through the bubble cloud. Three methods have been utilized to invert measurements and estimate the bubble population. The bubble population estimates have been used to develop a model for the bubble population resulting from an underwater explosion. PMID:22088003

  4. FEASTING BLACK HOLE BLOWS BUBBLES

    Science.gov (United States)

    2002-01-01

    A monstrous black hole's rude table manners include blowing huge bubbles of hot gas into space. At least, that's the gustatory practice followed by the supermassive black hole residing in the hub of the nearby galaxy NGC 4438. Known as a peculiar galaxy because of its unusual shape, NGC 4438 is in the Virgo Cluster, 50 million light-years from Earth. These NASA Hubble Space Telescope images of the galaxy's central region clearly show one of the bubbles rising from a dark band of dust. The other bubble, emanating from below the dust band, is barely visible, appearing as dim red blobs in the close-up picture of the galaxy's hub (the colorful picture at right). The background image represents a wider view of the galaxy, with the central region defined by the white box. These extremely hot bubbles are caused by the black hole's voracious eating habits. The eating machine is engorging itself with a banquet of material swirling around it in an accretion disk (the white region below the bright bubble). Some of this material is spewed from the disk in opposite directions. Acting like high-powered garden hoses, these twin jets of matter sweep out material in their paths. The jets eventually slam into a wall of dense, slow-moving gas, which is traveling at less than 223,000 mph (360,000 kph). The collision produces the glowing material. The bubbles will continue to expand and will eventually dissipate. Compared with the life of the galaxy, this bubble-blowing phase is a short-lived event. The bubble is much brighter on one side of the galaxy's center because the jet smashed into a denser amount of gas. The brighter bubble is 800 light-years tall and 800 light-years across. The observations are being presented June 5 at the American Astronomical Society meeting in Rochester, N.Y. Both pictures were taken March 24, 1999 with the Wide Field and Planetary Camera 2. False colors were used to enhance the details of the bubbles. The red regions in the picture denote the hot gas

  5. Bubbles Tomorrow and Bubbles Yesterday, but Never Bubbles Today?

    OpenAIRE

    Williams, John C.

    2013-01-01

    Considering their importance and the amount of effort that has gone into understanding them, asset price bubbles continue to perplex. The evidence of these bubbles seldom squares with what would be expected from standard asset price theory. Unlike the suggestions from theory, expectations of prices of both stocks and houses tend to be procyclical—price expectations are driven by recent price performance. Thus, price expectations are extrapolative rather than rational, as assumed by standard a...

  6. Solvent extraction columns

    International Nuclear Information System (INIS)

    In pulsed columns for use in solvent extraction processes, e.g. the reprocessing of nuclear fuel, the horizontal perforated plates inside the column are separated by interplate spacers manufactured from metallic neutron absorbing material. The spacer may be in the form of a spiral or concentric circles separated by radial limbs, or may be of egg-box construction. Suitable neutron absorbing materials include stainless steel containing boron or gadolinium, hafnium metal or alloys of hafnium. (UK)

  7. Hydrodynamics in a swarm of rising bubbles; Hydrodynamique d'un essaim de bulles en ascension

    Energy Technology Data Exchange (ETDEWEB)

    Riboux, G

    2007-04-15

    In many applications, bubbles are used to agitate a liquid in order to enhance mixing and transfer. This work is devoted to the study of the hydrodynamics in a stable bubble column. Experimentally, we have determined the properties of the velocity fluctuations inside and behind a homogeneous swarm of rising bubbles for different bubble sizes and gas volume fractions {alpha}: self-similarity in {alpha}{sup 0,4}, spectrum in k{sup -3} and integral length scale controlled by buoyancy. Numerically, we have reproduced these properties by means of large-scale simulations, the bubbles being modeled by volume-forces. This confirms that the dynamics is controlled by wake interactions. (author)

  8. A study of gas bubbles in liquid mercury in a vertical Hele-Shaw cell

    International Nuclear Information System (INIS)

    High-quality observations of mesoscopic gas bubbles in liquid metal are vital for a further development of pyrometallurgical gas injection reactors. However, the opacity of metals enforces the use of indirect imaging techniques with limited temporal or spatial resolution. In addition, accurate interface tracking requires tomography which further complicates the design of a high-temperature experimental setup. In this paper, an alternative approach is suggested that circumvents these two main restrictions. By injecting gas in a thin layer of liquid metal entrapped between two flat and closely spaced plates, bubbles in a Hele-Shaw flow regime are generated. The resulting quasi-2D multiphase flow phenomena can be fully captured from a single point of view and, when using a non-wetted transparent plate material, the bubbles can be observed directly. The feasibility of this approach is demonstrated by observations on buoyancy-driven nitrogen bubbles in liquid mercury in a vertical Hele-Shaw cell. By using a moving high-speed camera to make continuous close up recordings of individual bubbles, the position and geometry of these bubbles are quantified with a high resolution along their entire path. After a thorough evaluation of the experimental accuracy, this information is used for a detailed analysis of the bubble expansion along the path. While the observed bubble growth is mainly caused by the hydrostatic pressure gradient, a careful assessment of the volume variations for smaller bubbles shows that an accurate bubble description should account for significant dynamic pressure variations that seem to be largely regime dependent. (orig.)

  9. Bursting Bubbles and Bilayers

    Directory of Open Access Journals (Sweden)

    Steven P. Wrenn, Stephen M. Dicker, Eleanor F. Small, Nily R. Dan, Michał Mleczko, Georg Schmitz, Peter A. Lewin

    2012-01-01

    Full Text Available This paper discusses various interactions between ultrasound, phospholipid monolayer-coated gas bubbles, phospholipid bilayer vesicles, and cells. The paper begins with a review of microbubble physics models, developed to describe microbubble dynamic behavior in the presence of ultrasound, and follows this with a discussion of how such models can be used to predict inertial cavitation profiles. Predicted sensitivities of inertial cavitation to changes in the values of membrane properties, including surface tension, surface dilatational viscosity, and area expansion modulus, indicate that area expansion modulus exerts the greatest relative influence on inertial cavitation. Accordingly, the theoretical dependence of area expansion modulus on chemical composition - in particular, poly (ethylene glyclol (PEG - is reviewed, and predictions of inertial cavitation for different PEG molecular weights and compositions are compared with experiment. Noteworthy is the predicted dependence, or lack thereof, of inertial cavitation on PEG molecular weight and mole fraction. Specifically, inertial cavitation is predicted to be independent of PEG molecular weight and mole fraction in the so-called mushroom regime. In the “brush” regime, however, inertial cavitation is predicted to increase with PEG mole fraction but to decrease (to the inverse 3/5 power with PEG molecular weight. While excellent agreement between experiment and theory can be achieved, it is shown that the calculated inertial cavitation profiles depend strongly on the criterion used to predict inertial cavitation. This is followed by a discussion of nesting microbubbles inside the aqueous core of microcapsules and how this significantly increases the inertial cavitation threshold. Nesting thus offers a means for avoiding unwanted inertial cavitation and cell death during imaging and other applications such as sonoporation. A review of putative sonoporation mechanisms is then presented

  10. Nuclear reactor with a reactor core composed of fuel elements

    International Nuclear Information System (INIS)

    A tube surrounding a fuel element projects above the liquid level. The tube is situated in a pot, whose upper edge lies between the top of the reactor core and the liquid level. A greater pressure is therefore produced, which ensures a reduction of the steam bubble proportion in the cooling liquid at the other fuel elements. (orig./HP)

  11. Growth process of helium bubbles in aluminum

    International Nuclear Information System (INIS)

    The growth process of helium bubbles in α-particle bombarded pure aluminum during isothermal anneal at 200 to 6450C for 1 hr to 100 hr was observed by transmission electronmicroscopy and possible mechanisms are discussed. The effects of helium concentration and cold work were investigated. Helium bubbles are detectable only by annealing above 5500C for 1 hr in both the annealed and cold worked samples. The cold work does not cause any extra coarsening trend of bubbles. The observed types of the bubble distribution are divided into two categories, irrespective of helium concentration and cold work; (1) fine and uniform bubble distribution, in which case the average size is limited to about 200 A or less in diameter even by the anneal just below the melting point, and (2) the coarsened and nonuniform bubble distribution ranging from 500 to 4000 A in diameter. The intermediate size bubbles are scarcely found in any cases. In the above fine bubble distribution, the increase of helium concentration by a factor of two increases the density by the same factor of two, but does not change the mean size of bubbles. From these two characteristic bubble distributions, it is concluded that two different mechanisms are operative in this experiment (1) the growth of bubbles by Brownian motion, in which the growth rate of bubbles is decreased to almost zero by bubble faceting and this results in the bubble size constancy during the prolonged annealing, and (2) the growth of bubbles by the grain boundary sweep-out mechanism, by which the abrupt coarsening of bubbles is caused. The lack of the intermediate size bubble is explained in this way. (auth.)

  12. Aspherical bubble dynamics and oscillation times

    Energy Technology Data Exchange (ETDEWEB)

    Godwin, R.P.; Chapyak, E.J. [Los Alamos National Lab., NM (United States); Noack, J.; Vogel, A. [Medizinisches Laserzentrum Luebeck (Germany)

    1999-03-01

    The cavitation bubbles common in laser medicine are rarely perfectly spherical and are often located near tissue boundaries, in vessels, etc., which introduce aspherical dynamics. Here, novel features of aspherical bubble dynamics are explored. Time-resolved experimental photographs and simulations of large aspect ratio (length:diameter {approximately}20) cylindrical bubble dynamics are presented. The experiments and calculations exhibit similar dynamics. A small high-pressure cylindrical bubble initially expands radially with hardly any axial motion. Then, after reaching its maximum volume, a cylindrical bubble collapses along its long axis with relatively little radial motion. The growth-collapse period of these very aspherical bubbles differs only sightly from twice the Rayleigh collapse time for a spherical bubble with an equivalent maximum volume. This fact justifies using the temporal interval between the acoustic signals emitted upon bubble creation and collapse to estimate the maximum bubble volume. As a result, hydrophone measurements can provide an estimate of the bubble energy even for aspherical bubbles. The prolongation of the oscillation period of bubbles near solid boundaries relative to that of isolated spherical bubbles is also discussed.

  13. Tohoku one meter bubble chamber

    International Nuclear Information System (INIS)

    At the request of Tohoku University and the National Laboratory for High Energy Physics, IHI has developed a complete freon bubble chamber system successfully, which is used for photo analysis of elementary particles physics. This system will be delivered to Fermi National Accelerator Laboratory (FNAL) in Illinois (U.S.A.) and will be coupled with the superconducting accelerator (TEVATRON) for the study of elementary particles. The total system of the freon bubble chamber is composed of a stainless steel casting spherical bubble chamber with a diameter of about one meter, an expansion system for freon pressure control, hydraulic system for driving an expansion piston, a freon feed system, a temperature control system, an overall control system as well as camera and flashlight for photograph. (author)

  14. Particle Residence Time in Column Flotation Based on Cyclonic Separation

    Institute of Scientific and Technical Information of China (English)

    ZHOU Xiao-hua; LIU Jiong-tian

    2007-01-01

    The cyclonic static micro-bubble column flotation (FCSMC) is an effective separation device for fine particle treatment. The high mineralization rate and short flotation time of this equipment can be attributed to its unique cyclonic force field. It also has been observed that the presence of a cyclonic force field leads to a lower bottom separation size limit and a reduction of unselective entrainment. The collection zone of the column is considered to consist of two parts, a column separation zone and a cyclonic zone. Total recovery of the collection zone was developed. For our study, we analyzed the particle movement in the cyclonic zone. Particle residence time equations for the cyclonic zone were derived by force analysis. Results obtained in this study provide a theoretical foundation for the design and scale-up of the FCSMC.

  15. Prediction of adiabatic bubbly flows in TRACE using the interfacial area transport equation

    International Nuclear Information System (INIS)

    The conventional thermal-hydraulic reactor system analysis codes utilize a two-field, two-fluid formulation to model two-phase flows. To close this model, static flow regime transition criteria and algebraic relations are utilized to estimate the interfacial area concentration (ai). To better reflect the continuous evolution of two-phase flow, an experimental version of TRACE is being developed which implements the interfacial area transport equation (IATE) to replace the flow regime based approach. Dynamic estimation of ai is provided through the use of mechanistic models for bubble coalescence and disintegration. To account for the differences in bubble interactions and drag forces, two-group bubble transport is sought. As such, Group 1 accounts for the transport of spherical and distorted bubbles, while Group 2 accounts for the cap, slug, and churn-turbulent bubbles. Based on this categorization, a two-group IATE applicable to the range of dispersed two-phase flows has been previously developed. Recently, a one-group, one-dimensional, adiabatic IATE has been implemented into the TRACE code with mechanistic models accounting for: (1) bubble breakup due to turbulent impact of an eddy on a bubble, (2) bubble coalescence due to random collision driven by turbulent eddies, and (3) bubble coalescence due to the acceleration of a bubble in the wake region of a preceding bubble. To demonstrate the enhancement of the code's capability using the IATE, experimental data for ai, void fraction, and bubble velocity measured by a multi-sensor conductivity probe are compared to both the IATE and flow regime based predictions. In total, 50 air-water vertical co-current upward and downward bubbly flow conditions in pipes with diameters ranging from 2.54 to 20.32 cm are evaluated. It is found that TRACE, using the conventional flow regime relation, always underestimates ai. Moreover, the axial trend of the ai prediction is always quasi-linear because ai in the conventional

  16. Final design and construction issues of the TAPIRO epithermal column

    International Nuclear Information System (INIS)

    The construction of the epithermal column for clinical trials at the 5 kW fast reactor TAPIRO (ENEA, Casaccia, Italy) has been completed, the experimental bunker in the reactor hall has been designed and the beam characterisation will shortly be underway. As has been reviewed at the last two ICNCT conferences, the low power of the neuron source and the relatively distant patient position outside the reactor shield led to a column design with certain characteristics. One consequence is the employment of a collimator containing lead of high purity with the resultant problems of mechanical construction. Another is the substantial neutron leakage from the column outside the aperture into the experimental bunker. Furthermore the absence of a gamma shield has led to an electron dose to the skin. This is resolved with an electron shield of aluminium. Here the construction and final design issues are discussed and the state of the project is presented. (author)

  17. Estimation of the lifetime of small helium bubbles near tungsten surfaces -- a methodological study

    CERN Document Server

    Cui, Jiechao; Hou, Qing

    2016-01-01

    Under low energy and high flux/fluence irradiation of helium (He) atoms, the formation and bursting of He bubbles on tungsten (W) surfaces play important roles in the morphological evolution of component surfaces and impurity production in fusion reactors. Microscopically, the bursting of He bubbles is a stochastic process, and He bubbles have statistically average lifetimes. In the present paper, a molecular dynamics-based method was developed to extract, for the first time, the lifetime of He bubbles near tungsten surfaces. It was found that He bubble bursting can be treated as an activated event. Its occurrence frequency or, equivalently, the average lifetime of bubbles follows the Arrhenius equation. For a given bubble size, the activation energy exhibits a good linear dependence with the depth, and the pre-exponential factor obeys the Meyer-Nedle rule. These results are useful for establishing a model in multi-scale simulations of impurity production in the fusion plasma and of the morphological evolutio...

  18. Gas-bubble growth mechanisms in the analysis of metal fuel swelling

    International Nuclear Information System (INIS)

    During steady-state irradiation, swelling rates associated with growth of fission-gas bubbles in metallic fast reactor fuels may be expected to remain small. As a consequence, bubble-growth mechanisms are not a major consideration in modeling the steady-state fuel behavior, and it is usually adequate to consider the gas pressure to be in equilibrium with the external pressure and surface tension restraint. On transient time scales, however, various bubble-growth mechanisms become important components of the swelling rate. These mechanisms include growth by diffusion, for bubbles within grains and on grain boundaries; dislocation nucleation at the bubble surface, or ''punchout''; and bubble growth by creep. Analyses of these mechanisms are presented and applied to provide information on the conditions and the relative time scales for which the various processes should dominate fuel swelling. The results are compared to a series of experiments in which the swelling of irradiated metal fuel was determined after annealing at various temperatures and pressures. The diffusive growth of bubbles on grain boundaries is concluded to be dominant in these experiments

  19. Inhomogeneous MUSIG Model - a population balance approach for polydispersed bubbly flows

    International Nuclear Information System (INIS)

    Many flow regimes in Nuclear Reactor Safety (NRS) Research are characterized by multiphase flows, with one phase being a continuous liquid and the other phase consisting of gas or vapour of the liquid phase. In the range of low to intermediate volume fraction of the gaseous phase the multiphase flow under consideration is a bubbly or slug flow, where the disperse phase is characterized by an evolving bubble size distribution due to bubble breakup and coalescence processes. The paper presents a generalized inhomogeneous Multiple Size Group (MUSIG) Model. Within this model the disperse gaseous phase is divided into N inhomogeneous velocity groups (phases) and each of these groups is subdivided into M bubble size classes. Bubble breakup and coalescence processes between all bubble size classes are taken into account by appropriate models. The derived inhomogeneous MUSIG model has been validated against experimental data from the TOPFLOW test facility at the Research Center Rossendorf (FZR). Comparisons of gas volume fraction and velocity profiles with TOPFLOW-074 test case data are provided, showing the applicability and accuracy of the model for polydispersed bubbly flow in large diameter vertical pipe flow. (author)

  20. Detecting the gas bubbles in a liquid metal coolants by mans of magnetic flowmeters

    International Nuclear Information System (INIS)

    Solution of some problems of control and diagnosis of circuits with a liquid-metal coolant (LMC) often requires the detection of gas bubbles penetrating the circulaton loop. The sources of gas intake can be presented by failed fuel elements in reactor core, failed heat-exchange surfaces in sodium-water steam generators in the secondary circuits, gas capture by circulating coolant from gas circuits. Sometimes the gas is especially injected into circulating coolant to study the dynamics of accumulation and extraction of gas bubbles and to solve research problems, related to simulations of emergency situations. The most commonly used methods for gas bubble detection include methods, based on measuring coolant electric conductivity. Method for detecting gas bubbles in LMC, based on revealing the change of its electric conductivity is considered. Magnetic flowmeter is used as a detecting element of these changes. Approximate theory for describing spectral and energy noises in signals of a magnetic flowmeter, controlling the flow rate of LMC with gas bubbles is suggested. New method for signal reading is suggested. Experimental results, illustrating possibility of using the method for measuring the rate of bubble movement and studying the dependence of gas bubble volume on the flow rate of injected gas are presented

  1. Hydrodynamic Interactions of a Bubble Pair and Bubbles in Clusters

    Czech Academy of Sciences Publication Activity Database

    Stanovský, Petr; Růžička, Marek

    Prague : ICPF ASCR, 2013. s. 122. ISBN N. [Workshop on Smart and Green Interfaces 2013. 20.3.2013-22.03.2013, Prague] Grant ostatní: COST (XE) MP1106 Institutional support: RVO:67985858 Keywords : ultrapure water * bubbles * silicon oils Subject RIV: CI - Industrial Chemistry, Chemical Engineering

  2. Slender CRC Columns

    OpenAIRE

    Aarup, Bendt; Jensen, Lars Rom; Ellegaard, Peter

    2005-01-01

    CRC is a high-performance steel fibre reinforced concrete with a typical compressive strength of 150 MPa. Design methods for a number of structural elements have been developed since CRC was invented in 1986, but the current project set out to further investigate the range of columns for which current design guides can be used. The columns tested had a slenderness varying from 1.11 to 12.76 and a reinforcement ratio (area of rebar to area of concrete) ranging from 0 to 8.8 %. A total of 77 te...

  3. Optical measurement of slurry concentration profile in a concurrent-flow gas-slurry column

    International Nuclear Information System (INIS)

    An optical technique is described which allows the measurement of steady-state slurry concentration profile in a slender concurrent-flow gas-slurry bubble column. The optically measured profile is compared with that predicted by a previously reported semiempirical dispersion model. Qualitative agreement is observed between them, and the reliability of the technique is supported by additional experimental data

  4. Calibration of an accountability tank by bubbling pressure method: correction factors to be taken into account; Etalonnage d`une cuve de comptabilite par mesure de pression de bullage: facteurs correctifs a prendre en compte

    Energy Technology Data Exchange (ETDEWEB)

    Cauchetier, Ph.

    1993-12-31

    To obtain the needed precision in the calibration of an accountability tank by bubbling pressure method, it requires to use very slow bubbling. The measured data (mass and pressure) must be transformed into physical sizes of the vessel (height and cubic capacity). All corrections to take in account (buoyancy, calibration curve of the sensor, density of the liquid, weight of the gas column, bubbling overpressure, temperature...) are reviewed and valuated. We give the used equations. (author). 3 figs., 1 tab., 2 refs.

  5. Radiation Characteristics of Glass Containing Gas Bubbles

    OpenAIRE

    Pilon, Laurent; Viskanta, Raymond

    2003-01-01

    In many materials processing and manufacturing situations such as steel, aluminum, ceramics and glass, gas bubbles can form in liquid and solid phases. The presence of such bubbles affects the thermophysical properties and radiation characteristics of the two-phase system and hence the transport phenomena. This paper presents a general formulation of the radiation characteristics of semitransparent media containing large gas bubbles (bubble radius is much larger than the wavelength of radiati...

  6. Modeling bubbly-cap flows using two-group average bubble number density

    International Nuclear Information System (INIS)

    The basic concept of two-group average bubble number density equations along with three-fluid model has been demonstrated for vertical gas-liquid flow. Specifically, the current study focused on: (i)classification of bubble interaction between spherical bubbles (Group-1) and cap bubbles (Group- 2), (ii) preliminary consideration of source and sink terms in the averaged bubble number density equations via the model of Hibiki and Ishii [1] and (iii) assessment by means of experimental data sets at bubbly-to-cap flow transition. Reasonable agreement was achieved between measured and predicted distributions of void fraction, interfacial area concentration (IAC) and volume equivalent bubble diameter. (author)

  7. Frictional drag reduction by bubble injection

    Science.gov (United States)

    Murai, Yuichi

    2014-07-01

    The injection of gas bubbles into a turbulent boundary layer of a liquid phase has multiple different impacts on the original flow structure. Frictional drag reduction is a phenomenon resulting from their combined effects. This explains why a number of different void-drag reduction relationships have been reported to date, while early works pursued a simple universal mechanism. In the last 15 years, a series of precisely designed experimentations has led to the conclusion that the frictional drag reduction by bubble injection has multiple manifestations dependent on bubble size and flow speed. The phenomena are classified into several regimes of two-phase interaction mechanisms. Each regime has inherent physics of bubbly liquid, highlighted by keywords such as bubbly mixture rheology, the spectral response of bubbles in turbulence, buoyancy-dominated bubble behavior, and gas cavity breakup. Among the regimes, bubbles in some selected situations lose the drag reduction effect owing to extra momentum transfer promoted by their active motions. This separates engineers into two communities: those studying small bubbles for high-speed flow applications and those studying large bubbles for low-speed flow applications. This article reviews the roles of bubbles in drag reduction, which have been revealed from fundamental studies of simplified flow geometries and from development of measurement techniques that resolve the inner layer structure of bubble-mixed turbulent boundary layers.

  8. Modeling bubble collapse aggressiveness in traveling bubble cavitation using bubble breakup model

    Czech Academy of Sciences Publication Activity Database

    Zima, Patrik; Sedlář, M.

    Singapore : Research Publishing Services, 2012 - (Ohl, C.; Klaseboer, E.; Ohl, S.; Gong, S.; Khoo, B.), s. 182-186 ISBN 978-981-07-2826-7. [International Symposium on Cavitation /8./ CAV 2012. Singapur (SG), 13.08.2012-16.08.2012] R&D Projects: GA ČR GAP101/10/1428 Institutional research plan: CEZ:AV0Z20760514 Keywords : bubble collapse * traveling bubble cavitation * numerical modeling Subject RIV: BK - Fluid Dynamics http://rpsonline.com.sg/proceedings/9789810728267/html/209.xml51.xml

  9. Passive acoustic derived bubble flux and applications to natural gas seepage in the Mackenzie Delta, NWT, Canada and Coal Oil Point, CA

    Science.gov (United States)

    Culling, D.; Leifer, I.; Dallimore, S.; Alcala, K.

    2012-12-01

    Methane is a prominent greenhouse gas that escapes naturally from thermogenic reservoirs as seepage from marine and lacustrine biogenic sources as bubble ebullition. Geologic methane emissions are critically important contributors to the global methane budget however, few quantitative flux measurements are available for shallow waters. This gap in knowledge is critical as in these settings gas can easily transit as bubbles through the water column and directly influence global atmospheric budgets. Video and active acoustic (sonar) measurements of bubble flux have spatial limitations requiring predictable bubble emission location. Passive acoustics are less affected by these limitations, in addition, they can provide data in water too shallow for effective sonar bubble observations. Lab tests were undertaken to quantify the acoustic signature of bubbles formed in non-cohesive sediments. specifically focusing on mechanisms that complicate interpretation of acoustic data. Lab tests then were compared to field data to provide measurement calibration/validation. The principles behind the acoustic analysis method are based on the Minnaert equation, which relates a bubble radius and acoustic frequency. Bubble size and the resultant acoustic frequency from known flows and capillary tube diameters are well documented; however changing sediment pathways adds to the complexity of bubble formation and the resultant bubble acoustic signal. These complex signals were investigated in a lab tank with a thick, cohesive fine-grained sediment bed, through which bubbles produced by a syringe pump migrated to the sediment-water interface. Then, the resultant bubbles were diverted into clear water and measured from high speed, high definition video, while the acoustic signature of bubble formation was recorded concurrently by a hydrophone. Bubble formation is influenced by currents, which shifts the acoustical signal towards a higher frequency with a more complex pattern than the

  10. Column: Job crafting

    NARCIS (Netherlands)

    Reep, Frans van der

    2012-01-01

    1e alinea column: Organisaties dienen tegenwoordig randvoorwaarden te creëren waarbij ook behoeftes van de medewerkers aan autonomie, identificatie en zingeving worden vervuld. In organisaties die dit snappen geven de medewerkers zelf vorm aan eigen functie zodat die voldoet aan de behoeftes van de

  11. European Analytical Column

    DEFF Research Database (Denmark)

    Karlberg, B.; Grasserbauer, M.; Andersen, Jens Enevold Thaulov

    2009-01-01

    The European Analytical Column has once more invited a guest columnist to give his views on various matters related to analytical chemistry in Europe. This year, we have invited Professor Manfred Grasserbauer of the Vienna University of Technology to present some of the current challenges for...

  12. Implementation of two-phase tritium models for helium bubbles in HCLL breeding blanket modules

    OpenAIRE

    Fradera, Jordi; Sedano, L.A.; Mas de les Valls Ortiz, Elisabet; Batet Miracle, Lluís

    2011-01-01

    Tritium self-sufficiency requirement of future DT fusion reactors involves large helium production rates in the breeding blankets; this might impact on the conceptual design of diverse fusion power reactor units, such as Liquid Metal (LM) blankets. Low solubility, long residence-times and high production rates create the conditions for Helium nucleation, which could mean effective T sinks in LM channels. A model for helium nano-bubble formation and tritium conjugate transport phen...

  13. Impurity bubbles in a BEC

    Science.gov (United States)

    Timmermans, Eddy; Blinova, Alina; Boshier, Malcolm

    2013-05-01

    Polarons (particles that interact with the self-consistent deformation of the host medium that contains them) self-localize when strongly coupled. Dilute Bose-Einstein condensates (BECs) doped with neutral distinguishable atoms (impurities) and armed with a Feshbach-tuned impurity-boson interaction provide a unique laboratory to study self-localized polarons. In nature, self-localized polarons come in two flavors that exhibit qualitatively different behavior: In lattice systems, the deformation is slight and the particle is accompanied by a cloud of collective excitations as in the case of the Landau-Pekar polarons of electrons in a dielectric lattice. In natural fluids and gases, the strongly coupled particle radically alters the medium, e.g. by expelling the host medium as in the case of the electron bubbles in superfluid helium. We show that BEC-impurities can self-localize in a bubble, as well as in a Landau-Pekar polaron state. The BEC-impurity system is fully characterized by only two dimensionless coupling constants. In the corresponding phase diagram the bubble and Landau-Pekar polaron limits correspond to large islands separated by a cross-over region. The same BEC-impurity species can be adiabatically Feshbach steered from the Landau-Pekar to the bubble regime. This work was funded by the Los Alamos LDRD program.

  14. Impact of nuclear irradiation on helium bubble nucleation at interfaces in liquid metals coupled to permeation through stainless steels

    CERN Document Server

    Fradera, Jorge

    2013-01-01

    The impact of nucleating gas bubbles in the form of a dispersed gas phase on hydrogen isotope permeation at interfaces between liquid metals, like LLE, and structural materials, like stainless steel, has been studied. Liquid metal to structural material interfaces involving surfaces, may lower the nucleation barrier promoting bubble nucleation at active sites. Hence, hydrogen isotope absorption into gas bubbles modelling and control at interfaces may have a capital importance regarding design, operation and safety. He bubbles as a permeation barrier principle is analysed showing a significant impact on hydrogen isotope permeation, which may have a significant effect on liquid metal systems, e.g., tritium extraction systems. Liquid metals like LLE under nuclear irradiation in, e.g., breeding blankets of a nuclear fusion reactor would generate tritium which is to be extracted and recirculated as fuel. At the same time that tritium is bred, helium is also generated and may precipitate in the form of nano bubbles...

  15. Flare imaging with multibeam systems: Data processing for bubble detection at seeps

    Science.gov (United States)

    Schneider von Deimling, J.; Brockhoff, J.; Greinert, J.

    2007-06-01

    Multibeam sonar surveys have been conducted since their invention in the 1970s; however, mainly reflections from the seafloor were considered so far. More recently, water column imaging with multibeam is becoming of increasing interest for fisheries, buoy, mooring, or gas detection in the water column. Using ELAC SEABEAM 1000 data, we propose a technique to detect gas bubbles (flares) although this system is originally not designed to record water column data. The described data processing represents a case study and can be easily adapted to other multibeam systems. Multibeam data sets from the Black Sea and the North Sea show reflections of gas bubbles that form flares in the water column. At least for reasonably intense gas escape the detection of bubbles is feasible. The multibeam technique yields exact determination of the source position and information about the dimension of the gas cloud in the water. Compared to conventional flare imaging by single-beam echo sounders, the wide swath angle of multibeam systems allows the mapping of large areas in much shorter time.

  16. Experimental study of the interaction between the spark-induced cavitation bubble and the air bubble

    Institute of Scientific and Technical Information of China (English)

    罗晶; 许唯临; 牛志攀; 罗书靖; 郑秋文

    2013-01-01

    Experiments are carried out by using high-speed photography to investigate the interaction between the spark-generated cavitation bubble and the air bubble in its surrounding fluid. Three problems are discussed in detail: the impact of the air bubble upon the development of the cavitation bubble, the evolution of the air bubble under the influence of the cavitation bubble, and the change of the fluid pressure during the development of a micro jet of the cavitation bubble. Based on the experimental results, under the condition of no air bubble present, the lifetime of the cavitation bubble from expansion to contraction increases with the increase of the maximum radius. On the other hand, when there is an air bubble present, different sized cavitation bubbles have similarity with one another generally in terms of the lifetime from expansion to contraction, which does not depend on the maximum radius. Also, with the presence of an air bubble, the lifetime of the smaller cavitation bubble is extended while that of the bigger ones reduced. Furthermore, it is shown in the experiment that the low pressure formed in the opposite direction to the cavitation bubble micro jet makes the air bubble in the low pressure area being stretched into a steplike shape.

  17. Packing mode and optimization of flotation column

    Energy Technology Data Exchange (ETDEWEB)

    Li Yan-feng; Zhang Min; Liu Jiong-tian [University of Mining and Technology, Xuzhou (China). School of Chemical Engineering and Technology

    2008-04-15

    The effects of the two usual packing types, namely filling material and sieve plates, on flotation environment were analyzed and it was pointed out that sieve plate filling could be integrated with the fluid regime and mineralization environment with the results of stabilizing bubbles and enhancing the efficiencies of flotation and mineralization. The tests show that the ash gradient of the flotation column increases from 1.62%/m to 6.80%/m as a result of sieve plate filling. Material filling can clean the froth, reduce the ash of clean coal and make the froth steady. To form the two non-linear-change separation environments suitable for mineral separation, the mixed filling mode of packing sieve plates in the middle and lower parts of the column and packing material in the foam area was proposed. By optimizing the packing mode, the mixed packing mode of the sieve plates and honeycomb tubes were introduced. The simulation results show that obligatory suppression of the honeycomb tubes make the radial distribution of the fluid at the second sieve plate completely disappear and the axial velocity stable. It makes the flow regime transfers from turbulent flow to plug flow in a short distance come true. 7 refs., 5 figs., 2 tabs.

  18. FLUIDDYNAMIC ASPECTS OF GAS-PHASE ETHYLENE POLYMERIZATION REACTOR DESIGN

    OpenAIRE

    R. Guardani; A.C.S.C. Teixeira; E.L. Casella

    1998-01-01

    The relative importance of design variables affecting the fluiddynamic behavior of a fluidized bed reactor for the gas-phase ethylene polymerization is discussed, based on mathematical modeling. The three-phase bubbling fluidized bed model is based on axially distributed properties for the bubble, cloud and emulsion phases, combined with correlations for population balance and entrainment. Under the operating conditions adopted in most industrial processes, the reactor performance is affected...

  19. Shell correction energy for bubble nuclei

    CERN Document Server

    Yu, Y; Magierski, P; Bulgac, Aurel; Magierski, Piotr

    2000-01-01

    The positioning of a bubble inside a many fermion system does not affect the volume, surface or curvature terms in the liquid drop expansion of the total energy. Besides possible Coulomb effects, the only other contribution to the ground state energy of such a system arises from shell effects. We show that the potential energy surface is a rather shallow function of the displacement of the bubble from the center and in most cases the preferential position of a bubble is off center. Systems with bubbles are expected to have bands of extremely low lying collective states, corresponding to various bubble displacements.

  20. APPLICATION OF γ-RAY ATTENUATION FOR AXIAL DISTRIBUTION OF HOLDUPS IN LARGE-SCALE BUBBLE COLUMN WITH EVALUATED PRESSURE%γ射线透射技术测量气液鼓泡塔内气含率的轴向分布

    Institute of Scientific and Technical Information of China (English)

    靳海波; 杨索和; 佟泽民

    2004-01-01

    The axial profile of gas holdups was measured using a γ-ray densitometry in the pressurizedb ubble column, 0. 3 m in diameter and 6.6 m in height. The principle of γ-ray measurement and data processing is discussed. The axial profile of gas holdups and its average value in two-phase system were obtained in the churn-turbulent flow regime with a gas velocity up to 0.40 m · s-1 and a system pressure up to 1.0 MPa, which are in agreement with results obtained by differential pressure method. The effects of superficial gas velocity, liquid surface tension, liquid viscosity and system pressure on the axial profile of gas holdups were investigated. It is shown that the gas holdup decreases with the increasing liquid viscosity and liquid surface tension, and increases with the increase of pressure and superficial gas velocity.

  1. Electrical Capacitance Volume Tomography for the Packed Bed Reactor ISS Flight Experiment

    Science.gov (United States)

    Marashdeh, Qussai; Motil, Brian; Wang, Aining; Liang-Shih, Fan

    2013-01-01

    Fixed packed bed reactors are compact, require minimum power and maintenance to operate, and are highly reliable. These features make this technology a highly desirable unit operation for long duration life support systems in space. NASA is developing an ISS experiment to address this technology with particular focus on water reclamation and air revitalization. Earlier research and development efforts funded by NASA have resulted in two hydrodynamic models which require validation with appropriate instrumentation in an extended microgravity environment. To validate these models, the instantaneous distribution of the gas and liquid phases must be measured.Electrical Capacitance Volume Tomography (ECVT) is a non-invasive imaging technology recently developed for multi-phase flow applications. It is based on distributing flexible capacitance plates on the peripheral of a flow column and collecting real-time measurements of inter-electrode capacitances. Capacitance measurements here are directly related to dielectric constant distribution, a physical property that is also related to material distribution in the imaging domain. Reconstruction algorithms are employed to map volume images of dielectric distribution in the imaging domain, which is in turn related to phase distribution. ECVT is suitable for imaging interacting materials of different dielectric constants, typical in multi-phase flow systems. ECVT is being used extensively for measuring flow variables in various gas-liquid and gas-solid flow systems. Recent application of ECVT include flows in risers and exit regions of circulating fluidized beds, gas-liquid and gas-solid bubble columns, trickle beds, and slurry bubble columns. ECVT is also used to validate flow models and CFD simulations. The technology is uniquely qualified for imaging phase concentrations in packed bed reactors for the ISS flight experiments as it exhibits favorable features of compact size, low profile sensors, high imaging speed, and

  2. An equation of motion for bubble growth

    International Nuclear Information System (INIS)

    A mathematical model is developed which describes asymmetric bubble growth, either during boiling or bubble injection from submerged orifices. The model is developed using the integral form of the continuity and momentum equations, resulting in a general expression for the acceleration of the bubble's centre of gravity. The proposed model highlights the need to include acceleration due to an asymmetric gain or loss of mass in order to accurately predict bubble motion. Some scenarios are posed by which the growth of bubbles, particularly idealized bubbles that remain a section of a sphere, must include the fact that bubble growth can be asymmetric. In particular, for approximately hemispherical bubble growth the sum of the forces acting on the bubble is negligible compared with the asymmetric term. Further, for bubble injection from a submerged needle this component in the equation of motion is very significant during the initial rapid growth phase as the bubble issues from the nozzle changing from a near hemisphere to truncated sphere geometry. (author)

  3. Digital Microfluidics with Bubble Manipulations by Dielectrophoresis

    Directory of Open Access Journals (Sweden)

    Shih-Kang Fan

    2012-03-01

    Full Text Available This paper presents basic bubble manipulations, including transporting, splitting, and merging, by dielectrophoresis (DEP in an oil environment. In our presented method, bubbles are placed between parallel plates in an oil medium of a low vapor pressure, which eliminates the possibility of changing the gaseous composition of the bubble caused by evaporation of the medium. DEP has been previously investigated to actuate dielectric droplets and is adopted here to drive the oil environment as well as the immersed bubbles between parallel plates. In our experiment, air bubbles of 0.3 ml were successfully transported in a 20 cSt silicone oil medium between a 75 mm-high parallel plate gap. In addition, 0.6 ml air bubbles were successfully split into two 0.3 ml air bubbles, and then merged again by DEP. These successful manipulations make digital gaseous lab-on-a-chip a reality.

  4. Startup and oxygen concentration effects in a continuous granular mixed flow autotrophic nitrogen removal reactor.

    Science.gov (United States)

    Varas, Rodrigo; Guzmán-Fierro, Víctor; Giustinianovich, Elisa; Behar, Jack; Fernández, Katherina; Roeckel, Marlene

    2015-08-01

    The startup and performance of the completely autotrophic nitrogen removal over nitrite (CANON) process was tested in a continuously fed granular bubble column reactor (BCR) with two different aeration strategies: controlling the oxygen volumetric flow and oxygen concentration. During the startup with the control of oxygen volumetric flow, the air volume was adjusted to 60mL/h and the CANON reactor had volumetric N loadings ranging from 7.35 to 100.90mgN/Ld with 36-71% total nitrogen removal and high instability. In the second stage, the reactor was operated at oxygen concentrations of 0.6, 0.4 and 0.2mg/L. The best condition was 0.2 mgO2/L with a total nitrogen removal of 75.36% with a CANON reactor activity of 0.1149gN/gVVSd and high stability. The feasibility and effectiveness of CANON processes with oxygen control was demonstrated, showing an alternative design tool for efficiently removing nitrogen species. PMID:25965951

  5. Buoyant Bubbles in a Cooling Intracluster Medium I. Hydrodynamic Bubbles

    CERN Document Server

    Gardini, A

    2006-01-01

    Over the past several years, numerous examples of X-ray cavities coincident with radio sources have been observed in so-called "cool core" clusters of galaxies. Motivated by these observations, we explore the evolution and the effect of cavities on a cooling intracluster medium (ICM) numerically, adding relevant physics step by step. In this paper we present a first set of hydrodynamical, high resolution (1024^3 effective grid elements), three-dimensional simulations, together with two-dimensional test cases. The simulations follow the evolution of radio cavities, modeled as bubbles filled by relativistic plasma, in the cluster atmosphere while the ICM is subject to cooling. We find that the bubble rise retards the development of a cooling flow by inducing motions in the ICM which repeatedly displace the material in the core. Even bubbles initially set significantly far from the cluster center affect the cooling flow, although much later than the beginning of the simulation. The effect is, however, modest: th...

  6. Decoding the Pantheon Columns

    OpenAIRE

    Gerd Grasshoff; Christian Berndt

    2014-01-01

    The goal of this study has been to reconstruct the design principles underlying the construction of the Pantheon’s portico columns as well as to demonstrate how digital investigation methods and models can be used to improve our understanding of ancient architectural knowledge. Thanks to the data of the Bern Digital Pantheon Model, a synthesis of all the scanned surface points obtained during a digitization campaign of the Karman Center for Advanced Studies in the Humanities of the University...

  7. Nuclear Reactors

    Energy Technology Data Exchange (ETDEWEB)

    Hogerton, John

    1964-01-01

    This pamphlet describes how reactors work; discusses reactor design; describes research, teaching, and materials testing reactors; production reactors; reactors for electric power generation; reactors for supply heat; reactors for propulsion; reactors for space; reactor safety; and reactors of tomorrow. The appendix discusses characteristics of U.S. civilian power reactor concepts and lists some of the U.S. reactor power projects, with location, type, capacity, owner, and startup date.

  8. The Experimental Study of Bubble Formation: Acoustics and CCD Camera

    Czech Academy of Sciences Publication Activity Database

    Bunganič, Radovan; Růžička, Marek; Drahoš, Jiří

    - : -, 2005. 7.5.. [Conference on Gas-Liquid and Gas-Liquid-Solid Reactor Engineering /7./. 21.08.2005-24.08.2005, Strasbourg] R&D Projects: GA ČR(CZ) GA104/04/0826; GA ČR(CZ) GA104/05/2566 Grant ostatní: BEMUSAC(XE) G1MA/CT/2002/04019 Institutional research plan: CEZ:AV0Z40720504 Keywords : bubble formation * acoustic emissions * high-speed camera Subject RIV: CI - Industrial Chemistry, Chemical Engineering

  9. Developed ‘laminar’ bubbly flow with non-uniform bubble sizes

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Bubbles with different sizes have different dynamic and kineticbehavior in a two-phase bubbly flow. A common two-fluid model based on the uniform bubble size assumption is not suitable for a bubbly flow with non-uniform bubble sizes. To deal with non-uniform bubbly flows, a multi-fluid model is established, with which bubbles are divided into several groups according to their sizes and a set of basic equations is derived for each group of bubbles with almost the same size. Through analyzing the bubble-bubble and bubble-pipe wall interactions, two new constitutive laws for the wall-force and pressure difference between the liquid phase and interface are developed to close the averaged basic equations. The respective phase distributions for each group of bubbles measured by a specially designed three-dimensional photographic method are used to check the model. Comparison between model-predicted values and experimental data shows that the model can describe laminar bubbly flow with non-uniform bubble sizes.

  10. Bubbling the False Vacuum Away

    CERN Document Server

    Gleiser, Marcelo; Thorarinson, Joel

    2007-01-01

    We investigate the role of nonperturbative, bubble-like inhomogeneities on the decay rate of false-vacuum states in two and three-dimensional scalar field theories. The inhomogeneities are induced by setting up large-amplitude oscillations of the field about the false vacuum as, for example, after a rapid quench or in certain models of cosmological inflation. We show that, for a wide range of parameters, the presence of large-amplitude bubble-like inhomogeneities greatly accelerates the decay rate, changing it from the well-known exponential suppression of homogeneous nucleation to a power-law suppression. It is argued that this fast, power-law vacuum decay -- known as resonant nucleation -- is promoted by the presence of long-lived oscillons among the nonperturbative fluctuations about the false vacuum. A phase diagram is obtained distinguishing three possible mechanisms for vacuum decay: homogeneous nucleation, resonant nucleation, and cross-over. Possible applications are briefly discussed.

  11. Conformal gravity and "gravitational bubbles"

    CERN Document Server

    Berezin, V A; Eroshenko, Yu N

    2015-01-01

    We describe the general structure of the spherically symmetric solutions in the Weyl conformal gravity. The corresponding Bach equations are derived for the special type of metrics, which can be considered as the representative of the general class. The complete set of the pure vacuum solutions, consisting of two classes, is found. The first one contains the solutions with constant two-dimensional curvature scalar, and the representatives are the famous Robertson--Walker metrics. We called one of them the "gravitational bubbles", which is compact and with zero Weyl tensor. These "gravitational bubbles" are the pure vacuum curved space-times (without any material sources, including the cosmological constant), which are absolutely impossible in General Relativity. This phenomenon makes it easier to create the universe from "nothing". The second class consists of the solutions with varying curvature scalar. We found its representative as the one-parameter family, which can be conformally covered by the thee-para...

  12. Bubble entrapment through topological change

    KAUST Repository

    Thoroddsen, Sigurdur T.

    2010-05-03

    When a viscousdrop impacts onto a solid surface, it entraps a myriad of microbubbles at the interface between liquid and solid. We present direct high-speed video observations of this entrapment. For viscousdrops, the tip of the spreading lamella is separated from the surface and levitated on a cushion of air. We show that the primary mechanism for the bubble entrapment is contact between this precursor sheet of liquid with the solid and not air pulled directly through cusps in the contact line. The sheet makes contact with the solid surface,forming a wetted patch, which grows in size, but only entraps a bubble when it meets the advancing contact line. The leading front of this wet patch can also lead to the localized thinning and puncturing of the liquid film producing strong splashing of droplets.

  13. Cavitation inception from bubble nuclei

    DEFF Research Database (Denmark)

    Mørch, Knud Aage

    2015-01-01

    experimental investigations of bubbles and cavitation inception have been presented. These results suggest that cavitation nuclei in equilibrium are gaseous voids in the water, stabilized by a skin which allows diffusion balance between gas inside the void and gas in solution in the surrounding liquid. The...... cavitation nuclei may be free gas bubbles in the bulk of water, or interfacial gaseous voids located on the surface of particles in the water, or on bounding walls. The tensile strength of these nuclei depends not only on the water quality but also on the pressure-time history of the water. A recent model...... and associated experiments throw new light on the effects of transient pressures on the tensile strength of water, which may be notably reduced or increased by such pressure changes....

  14. Methodology on the sparger development for Korean next generation reactor

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Hwan Yeol; Hwang, Y.D.; Kang, H.S.; Cho, B.H.; Park, J.K

    1999-06-01

    In case of an accident, the safety depressurization system of Korean Next Generation Reactor (KNGR) efficiently depressurize the reactor pressure by directly discharge steam of high pressure and temperature from the pressurizer into the in-containment refuelling water storage tank (IRWST) through spargers. This report was generated for the purpose of developing the sparger of KNGR. This report presents the methodology on application of ABB-Atom. Many thermal hydraulic parameters affecting the maximum bubble could pressure were obtained and the maximum bubble cloud pressure transient curve so called forcing function of KNGR was suggested and design inputs for IRWST (bubble cloud radius vs. time, bubble cloud velocity vs. time, bubble cloudacceleration vs. time, etc.) were generated by the analytic using Rayleigh-Plesset equation. (author). 17 refs., 6 tabs., 27 figs.

  15. Methodology on the sparger development for Korean next generation reactor

    International Nuclear Information System (INIS)

    In case of an accident, the safety depressurization system of Korean Next Generation Reactor (KNGR) efficiently depressurize the reactor pressure by directly discharge steam of high pressure and temperature from the pressurizer into the in-containment refuelling water storage tank (IRWST) through spargers. This report was generated for the purpose of developing the sparger of KNGR. This report presents the methodology on application of ABB-Atom. Many thermal hydraulic parameters affecting the maximum bubble could pressure were obtained and the maximum bubble cloud pressure transient curve so called forcing function of KNGR was suggested and design inputs for IRWST (bubble cloud radius vs. time, bubble cloud velocity vs. time, bubble cloud acceleration vs. time, etc.) were generated by the analytic using Rayleigh-Plesset equation. (author). 17 refs., 6 tabs., 27 figs

  16. Behavior of Columns During Earthquakes

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The behavior of columns during earthquakes is very important since column failures may lead to additional structural failures and result in total building...

  17. Determination of Two Columns Performance

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    When protein is analyzed by high performance liquid chromatography (HPLC), the selection of column is one of the most important factors. There are four quality control parameters for the column, which are theoretical plates n, capacity facto

  18. BEBC Big European Bubble Chamber

    CERN Multimedia

    1974-01-01

    A view of the dismantling of the magnet of BEBC, the 3.7 m European Bubble Chamber : iron magnetic shielding ; lower and upper parts of the vacuum enclosure of the magnet; turbo-molecular vacuum pumps for the "fish-eye" windows; the two superconducting coils; a handling platform; the two cryostats suspended from the bar of the travelling crane which has a 170 ton carrying capacity. The chamber proper, not dismantled, is inside the shielding.

  19. Bubble-induced cave collapse.

    Directory of Open Access Journals (Sweden)

    Lakshika Girihagama

    Full Text Available Conventional wisdom among cave divers is that submerged caves in aquifers, such as in Florida or the Yucatan, are unstable due to their ever-growing size from limestone dissolution in water. Cave divers occasionally noted partial cave collapses occurring while they were in the cave, attributing this to their unintentional (and frowned upon physical contact with the cave walls or the aforementioned "natural" instability of the cave. Here, we suggest that these cave collapses do not necessarily result from cave instability or contacts with walls, but rather from divers bubbles rising to the ceiling and reducing the buoyancy acting on isolated ceiling rocks. Using familiar theories for the strength of flat and arched (un-cracked beams, we first show that the flat ceiling of a submerged limestone cave can have a horizontal expanse of 63 meters. This is much broader than that of most submerged Florida caves (~ 10 m. Similarly, we show that an arched cave roof can have a still larger expanse of 240 meters, again implying that Florida caves are structurally stable. Using familiar bubble dynamics, fluid dynamics of bubble-induced flows, and accustomed diving practices, we show that a group of 1-3 divers submerged below a loosely connected ceiling rock will quickly trigger it to fall causing a "collapse". We then present a set of qualitative laboratory experiments illustrating such a collapse in a circular laboratory cave (i.e., a cave with a circular cross section, with concave and convex ceilings. In these experiments, a metal ball represented the rock (attached to the cave ceiling with a magnet, and the bubbles were produced using a syringe located at the cave floor.

  20. Dynamical viscosity of nucleating bubbles

    CERN Document Server

    Alamoudi, S M; Boyanovsky, D; Aragão de Carvalho, C; Fraga, E S; Jorás, S E; Takakura, F I

    1999-01-01

    We study the viscosity corrections to the growth rate of nucleating bubbles in a first order phase transition in scalar field theory. We obtain the non-equilibrium equation of motion of the coordinate that describes small departures from the critical bubble and extract the growth rate consistently in weak coupling and in the thin wall limit. Viscosity effects arise from the interaction of this coordinate with the stable quantum and thermal fluctuations around a critical bubble. In the case of 1+1 dimensions we provide an estimate for the growth rate that depends on the details of the free energy functional. In 3+1 dimensions we recognize robust features that are a direct consequence of the thin wall approximation and give the leading viscosity corrections.These are long-wavelength hydrodynamic fluctuations that describe surface waves, quasi-Goldstone modes which are related to ripples on interfaces in phase ordered Ising-like systems. We discuss the applicability of our results to describe the growth rate of ...

  1. Analysis of large two phase uranium dioxide bubble behavior in water and sodium pools

    International Nuclear Information System (INIS)

    An understanding of the behavior of large, two-phase UO2 bubbles is important in assessing the consequences of a hypothetical core disruptive accident in a fast reactor. The UVABUBL II computer program was written to study the dynamics and heat and mass transfer in large UO2 bubbles, and the code was used to analyze data from the underwater and undersodium FAST experiments conducted at Oak Ridge National Laboratory in which the behavior of UO2 bubbles under a wide variety of conditions was examined. Significant understanding of the phenomena that govern UO2 bubble behavior in both water and sodium was obtained by matching calculations of pressure, bubble size, and bubble growth and collapse rate to the experimental data. Heat and mass transfer included radiative heat losses and coolant entrainment. Larger heat transfer rates were calculated for the water tests with significant surface vaporization occurring. Because of the high thermal conductivity of sodium, no surface vaporization was calculated for the sodium tests. Entrainment was not found to be necessary for either the water or sodium tests, but calculations that included entrainment implied that it may be occurring. 38 references

  2. Experiment and Numerical Simulation of Bubble Behavior in Argon Gas Injection into Lead-Bismuth Pool

    Science.gov (United States)

    Yamada, Yumi; Akashi, Toyou; Takahashi, Minoru

    In a lead-bismuth alloy (45%Pb-55%Bi) cooled direct contact boiling water fast reactor (PBWFR), steam can be produced by direct contact of feed water with primary Pb-Bi coolant in the upper core plenum, and Pb-Bi coolant can be circulated by buoyancy forces of steam bubbles. As a basic study to investigate the two-phase flow characteristics in the chimneys of PBWFR, a two-dimensional two-phase flow was simulated by injecting argon gas into Pb-Bi pool in a rectangular vessel (400mm in length, 1500mm in height), and bubble behavior were investigated experimentally. Bubble sizes, bubble rising velocities and void fractions were measured using void probes. The experimental conditions are the atmospheric pressure and the flow rate of injection Ar gas is 10, 20, and 30 NL/min. The average of measured bubble rising velocity was about 0.6 m/s. The average chord length was about 7mm. An analysis was performed by two-dimensional and two-fluid model. The experimental results were compared with the analytical results to evaluate the validity of the analytical model. Although large diameter bubbles were observed in the experiment, the drag force model of lower value performed better for simulation of the experimental result.

  3. Safety operation of chromatography column system with discharging hydrogen radiolytically generated

    Directory of Open Access Journals (Sweden)

    Watanabe Sou

    2015-01-01

    Full Text Available In the extraction chromatography system, accumulation of hydrogen gas in the chromatography column is suspected to lead to fire or explosion. In order to prevent the hazardous accidents, it is necessary to evaluate behaviors of gas radiolytically generated inside the column. In this study, behaviors of gas inside the extraction chromatography column were investigated through experiments and Computation Fluid Dynamics (CFD simulation. N2 gas once accumulated as bubbles in the packed bed was hardly discharged by the flow of mobile phase. However, the CFD simulation and X-ray imaging on γ-ray irradiated column revealed that during operation the hydrogen gas generated in the column was dissolved into the mobile phase without accumulation and discharged.

  4. Treatment of Wastewater Containing Heavy Metals Using Dissolved Air Released Flotation Column

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    A new type of dissolved air released flotation column is developed to treat wastewater containing Cr(Ⅵ) based on advantages of both dissolved air floatation and column floatation. By using a column with a diameter of 50 mm and a specially made dissolved air releaser, micro-bubbles inside the column can be formed. N2H4.H2O was used as reductant, AlCl3 as flocculant, C12H25SO3Na(SDS) as surfactant in the experiment. The effects of pH of wastewater, pressure of dissolved air, ratio of return water, and concentration of flocculant and surfactant on the removal efficiency are studied. The results show that the efficiency of dissolved air released flotation column is much higher than that of other approaches after the operation parameters are optimized, with the reduction ratio of Cr(Ⅵ) in wastewater reaching 98%. So this technique can be widely used in wastewater treatment.

  5. Column and Batch Experiments

    Directory of Open Access Journals (Sweden)

    Jorge L. Gardea-Torresdey

    2005-01-01

    Full Text Available Batch and column experiments were performed to determine the Cu(II binding capacity of silica-immobilized humin biomass. For column studies, 500 bed volumes of a 0.1 mM Cu(II solution were passed through humin packed columns at the flow rates of 1, 1.5, 2, and 3 mL/min. The biopolymer showed an average Cu binding capacity of 12 ± 1.5 mg/g and a Cu recovery of about 96.5 % ± 1.5. The breakthrough points for Cu(II alone were approximately 420, 390, 385, and 300 bed volumes for the flow rates of 1, 1.5, 2 and 3 mL/min, respectively. The interference studies demonstrated that at low concentrations, the hard cations Ca(II and Mg(II did not seem to represent a major interference on Cu(II binding to the humin biopolymer. The selectivity showed by this biopolymer was Cu(II>Ca(II>Mg(II. On the other hand, batch experiments showed that Ca(II + Mg(II at 100mM each reduced the Cu(II binding to 73 %. However, 1000 mM concentrations of Ca(II and Mg(II, separately and in mixture, reduced the Cu(II binding to 47 %, 44 % and 31 %, respectively. The results of this study showed that immobilized humin in a silica matrix could represent an inexpensive bio-source for Cu removal from contaminated water, even in the presence of low concentrations of the hard cations Ca(II and Mg(II.

  6. Column: Every Last Byte

    Directory of Open Access Journals (Sweden)

    Simson Garfinkel

    2011-06-01

    Full Text Available Inheritance powder is the name that was given to poisons, especially arsenic, that were commonly used in the 17th and early 18th centuries to hasten the death of the elderly. For most of the 17th century, arsenic was deadly but undetectable, making it nearly impossible to prove that someone had been poisoned. The first arsenic test produced a gas—hardly something that a scientist could show to a judge. Faced with a growing epidemic of poisonings, doctors and chemists spent decades searching for something better.(see PDF for full column

  7. Simulation of bubbly flow in vertical pipes by coupling Lagrangian and Eulerian models with 3D random walks models: validation with experimental data using multi-sensor conductivity probes and laser doppler anemometry

    International Nuclear Information System (INIS)

    A set of air-water experiments have been performed under isothermal upward concurrent flow in a vertical column. The interfacial velocity, interfacial area of the bubbles and the void fraction distributions was obtained. Numerical validation of these results for bubbly flow conditions were performed by coupling a Lagrangian code which tracks the 3D motion of the individual bubbles, with an Eulerian one. Both Lagrangian and Eulerian calculations were performed in parallel and iterative self-consistent method was developed. The bubbles-induced turbulence is an important issue considered, to obtain good predictions of experimental results. (author)

  8. Simulation of bubbly flow in vertical pipes by coupling Lagrangian and Eulerian models with 3D random walks models: validation with experimental data using multi-sensor conductivity probes and laser doppler anemometry

    Energy Technology Data Exchange (ETDEWEB)

    Munoz-Cobo, J.L. [Univ. Politecnica de Valencia, Inst. de Ingenieria Energetica, Valencia (Spain); Chiva, S. [Univ. Jaume I, Dept. of Mechnical Engineering and Construction, Castellon (Spain); Abd El Aziz Essa, M. [Univ. Politecnica de Valencia, Inst. de Ingenieria Energetica, Valencia (Spain); Mendes, S. [Univ. Autonoma de Nuevo Leon, Facultad de Ingenieria Mecanica y Electrica (Mexico)

    2011-07-01

    A set of air-water experiments have been performed under isothermal upward concurrent flow in a vertical column. The interfacial velocity, interfacial area of the bubbles and the void fraction distributions was obtained. Numerical validation of these results for bubbly flow conditions were performed by coupling a Lagrangian code which tracks the 3D motion of the individual bubbles, with an Eulerian one. Both Lagrangian and Eulerian calculations were performed in parallel and iterative self-consistent method was developed. The bubbles-induced turbulence is an important issue considered, to obtain good predictions of experimental results. (author)

  9. Biological Treatment of Dairy Wastewater by Sequencing Batch Reactor

    OpenAIRE

    A Mohseni-Bandpi, H Bazari

    2004-01-01

    A bench scale aerobic Sequencing Batch Reactor (SBR) was investigated to treat the wastewater from an industrial milk factory. The reactor was constructed from plexi glass material and its volume was 22.5 L. The reactor was supplied with oxygen by fine bubble air diffuser. The reactor was fed with milk factory and synthetic wastewater under different operational conditions. The COD removal efficiency was achieved more than 90%, whereas COD concentration varied from 400 to 2500 mg/l. The optim...

  10. Ostwald ripening in multiple-bubble nuclei

    Science.gov (United States)

    Watanabe, Hiroshi; Suzuki, Masaru; Inaoka, Hajime; Ito, Nobuyasu

    2014-12-01

    The Ostwald ripening of bubbles is studied by molecular dynamics simulations involving up to 679 × 106 Lennard-Jones particles. Many bubbles appear after depressurizing a system that is initially maintained in the pure-liquid phase, and the coarsening of bubbles follows. The self-similarity of the bubble-size distribution function predicted by Lifshitz-Slyozov-Wagner theory is directly confirmed. The total number of bubbles decreases asymptotically as t-x with scaling exponent x. As the initial temperature increases, the exponent changes from x = 3/2 to 1, which implies that the growth of bubbles changes from interface-limited (the t1/2 law) to diffusion-limited (the t1/3 law) growth.

  11. Ostwald Ripening in Multiple-Bubble Nuclei

    CERN Document Server

    Watanabe, Hiroshi; Inaoka, Hajime; Ito, Nobuyasu

    2014-01-01

    The ostwald ripening of bubbles is studied by molecular dynamics simulations involving up to 679 million Lennard-Jones particles. Many bubbles appear after depressurizing a system that is initially maintained in the pure-liquid phase, and the coarsening of bubbles follows. The self-similarity of the bubble-size distribution function predicted by Lifshitz-Slyozov-Wagner theory is directly confirmed. The total number of bubbles decreases asymptotically as $t^{-x}$ with scaling exponent $x$. As the initial temperature increases, the exponent changes from $x=3/2$ to $1$, which implies that the growth of bubbles changes from interface-limited (the $t^{1/2}$ law) to diffusion-limited (the $t^{1/3}$ law) growth.

  12. Manipulating bubbles with secondary Bjerknes forces

    International Nuclear Information System (INIS)

    Gas bubbles in a sound field are submitted to a radiative force, known as the secondary Bjerknes force. We propose an original experimental setup that allows us to investigate in detail this force between two bubbles, as a function of the sonication frequency, as well as the bubbles radii and distance. We report the observation of both attractive and, more interestingly, repulsive Bjerknes force, when the two bubbles are driven in antiphase. Our experiments show the importance of taking multiple scatterings into account, which leads to a strong acoustic coupling of the bubbles when their radii are similar. Our setup demonstrates the accuracy of secondary Bjerknes forces for attracting or repealing a bubble, and could lead to new acoustic tools for noncontact manipulation in microfluidic devices

  13. The KEK 1 m hydrogen bubble chamber

    International Nuclear Information System (INIS)

    A medium size hydrogen bubble chamber has been constructed at the National Laboratory for High Energy Physics, KEK. The bubble chamber has been designed to be operated with a maximum rate of three times per half a second in every two second repetition time of the accelerator, by utilizing a hydraulic expansion system. The bubble chamber has a one meter diameter and a visible volume of about 280 l. A three-view stereo camera system is used for taking photographic pictures of the chamber. A 2 MW bubble chamber magnet is constructed. The main part of the bubble chamber vessel is supported by the magnet yoke. The magnet gives a maximum field of 18.4 kG at the centre of the fiducial volume of the chamber. The overall system of the KEK 1 m hydrogen bubble chamber facility is described in some detail. Some operational characteristics of the facility are also reported. (auth.)

  14. Mechanism of bubble detachment from vibrating walls

    International Nuclear Information System (INIS)

    We discovered a previously unobserved mechanism by which air bubbles detach from vibrating walls in glasses containing water. Chaotic oscillation and subsequent water jets appeared when a wall vibrated at greater than a critical level. Wave forms were developed at water-air interface of the bubble by the wall vibration, and water jets were formed when sufficiently grown wave-curvatures were collapsing. Droplets were pinched off from the tip of jets and fell to the surface of the glass. When the solid-air interface at the bubble-wall attachment point was completely covered with water, the bubble detached from the wall. The water jets were mainly generated by subharmonic waves and were generated most vigorously when the wall vibrated at the volume resonant frequency of the bubble. Bubbles of specific size can be removed by adjusting the frequency of the wall's vibration

  15. Manipulating bubbles with secondary Bjerknes forces

    Energy Technology Data Exchange (ETDEWEB)

    Lanoy, Maxime [Institut Langevin, ESPCI ParisTech, CNRS (UMR 7587), PSL Research University, 1 rue Jussieu, 75005 Paris (France); Laboratoire Matière et Systèmes Complexes, Université Paris-Diderot, CNRS (UMR 7057), 10 rue Alice Domon et Léonie Duquet, 75013 Paris (France); Derec, Caroline; Leroy, Valentin [Laboratoire Matière et Systèmes Complexes, Université Paris-Diderot, CNRS (UMR 7057), 10 rue Alice Domon et Léonie Duquet, 75013 Paris (France); Tourin, Arnaud [Institut Langevin, ESPCI ParisTech, CNRS (UMR 7587), PSL Research University, 1 rue Jussieu, 75005 Paris (France)

    2015-11-23

    Gas bubbles in a sound field are submitted to a radiative force, known as the secondary Bjerknes force. We propose an original experimental setup that allows us to investigate in detail this force between two bubbles, as a function of the sonication frequency, as well as the bubbles radii and distance. We report the observation of both attractive and, more interestingly, repulsive Bjerknes force, when the two bubbles are driven in antiphase. Our experiments show the importance of taking multiple scatterings into account, which leads to a strong acoustic coupling of the bubbles when their radii are similar. Our setup demonstrates the accuracy of secondary Bjerknes forces for attracting or repealing a bubble, and could lead to new acoustic tools for noncontact manipulation in microfluidic devices.

  16. Single DNA denaturation and bubble dynamics

    International Nuclear Information System (INIS)

    While the Watson-Crick double-strand is the thermodynamically stable state of DNA in a wide range of temperature and salt conditions, even at physiological conditions local denaturation bubbles may open up spontaneously due to thermal activation. By raising the ambient temperature, titration, or by external forces in single molecule setups bubbles proliferate until full denaturation of the DNA occurs. Based on the Poland-Scheraga model we investigate both the equilibrium transition of DNA denaturation and the dynamics of the denaturation bubbles with respect to recent single DNA chain experiments for situations below, at, and above the denaturation transition. We also propose a new single molecule setup based on DNA constructs with two bubble zones to measure the bubble coalescence and extract the physical parameters relevant to DNA breathing. Finally we consider the interplay between denaturation bubbles and selectively single-stranded DNA binding proteins.

  17. Remote sensing of bubble clouds in seawater

    OpenAIRE

    Flatau, Piotr J.; Flatau, Maria; Zaneveld, J. R. V.; Mobley, Curtis D.

    2000-01-01

    We report on the influence of submerged bubble clouds on the remote sensing properties of water. We show that the optical effect of bubbles on radiative transfer and on the estimate of the ocean color is significant. We present a global map of the volume fraction of air in water derived from daily wind speed data. This map, together with the parameterization of the microphysical properties, shows the possible significance of bubble clouds on the albedo of incoming solar energy

  18. The economy of "soap bubbles" (continued)

    OpenAIRE

    O. Baranovskyi

    2009-01-01

    The author defines the essence of economic "bubbles". He reveals the peculiar features of "soap bubbles" on the markets of shares and consumer credits, in crediting realty purchases, granting credits to medium-size and small business and on the markets of realty and derivatives, as well as "soap bubbles" as a consequence of overconcentration of market, credit, Interest, and exchange risks and the liquidity risks and analyses their evolution. The article considers the specificity of economic (...

  19. A signature of anisotropic bubble collisions

    OpenAIRE

    Salem, Michael P.

    2010-01-01

    Our universe may have formed via bubble nucleation in an eternally-inflating background. Furthermore, the background may have a compact dimension---the modulus of which tunnels out of a metastable minimum during bubble nucleation---which subsequently grows to become one of our three large spatial dimensions. When in this scenario our bubble universe collides with other ones like it, the collision geometry is constrained by the reduced symmetry of the tunneling instanton. While the regions aff...

  20. Local measurements in turbulent bubbly flows

    International Nuclear Information System (INIS)

    Local measurements methods in bubbly flows are discussed. Concerning liquid velocity measurement, problems linked to HFA and LDA are first analysed. Then simultaneously recorded velocity signals obtained by both anemometers are compared. New signal processing are developed for the two techniques. Bubble sizes and velocities measurements methods using intrusive double optical sensor probe are presented. Plane bubbly mixing layer has been investigated. Local measurements using the described methods are presented as examples. (author)

  1. On Bubble Rising in Countercurrent Flow

    Czech Academy of Sciences Publication Activity Database

    Večeř, M.; Leštinský, P.; Wichterle, K.; Růžička, Marek

    2012-01-01

    Roč. 10, č. 2012 (2012), A30. ISSN 1542-6580 R&D Projects: GA ČR GA104/09/0972; GA ČR GA104/07/1110 Grant ostatní: GA MŠMT(CZ) CZ.1.05/2.1.00/03.0069 Institutional support: RVO:67985858 Keywords : ellipsoidal bubble * bubble shape * bubble velocity Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 0.790, year: 2011

  2. Bubble Universes With Different Gravitational Constants

    OpenAIRE

    Takamizu, Yu-ichi; Maeda, Kei-ichi

    2015-01-01

    We argue a scenario motivated by the context of string landscape, where our universe is produced by a new vacuum bubble embedded in an old bubble and these bubble universes have not only different cosmological constants, but also their own different gravitational constants. We study these effects on the primordial curvature perturbations. In order to construct a model of varying gravitational constants, we use the Jordan-Brans-Dicke (JBD) theory where different expectation values of scalar fi...

  3. Bremsstrahlung Radiation At a Vacuum Bubble Wall

    CERN Document Server

    Lee, Jae-Weon; Lee, Chul H; Jang, Ji-ho

    2007-01-01

    When charged particles collide with a vacuum bubble, they can radiate strong electromagnetic waves due to rapid deceleration. Owing to the energy loss of the particles by this bremsstrahlung radiation, there is a non-negligible damping pressure acting on the bubble wall even when thermal equilibrium is maintained. In the non-relativistic region, this pressure is proportional to the velocity of the wall and could have influenced the bubble dynamics in the early universe.

  4. Numerical analysis and optimisation of heavy water upgrading column

    International Nuclear Information System (INIS)

    In the 'Pressurised Heavy Water' type of reactors, heavy water is used both as moderator and coolant. During operation of reactor downgraded heavy water is generated that needs to be upgraded for reuse in the reactor. When the isotopic purity of heavy water becomes less than 99.75%, it is termed as downgraded heavy water. Downgraded heavy water also contains impurity such as corrosion products, dirt, oil etc. Upgradation of downgraded heavy water is normally done in two steps: (i) Purification: In this step downgraded heavy water is first purified to remove corrosion products, dirt, oil, etc. and (ii) Upgradation of heavy water to increase its isotopic purity, this step is carried out by vacuum distillation of downgraded heavy water after purification. This project is aimed at mathematical modelling and numerical simulation of heavy water upgrading column. Modelling and simulation studies of the upgradation column are based on equilibrium stage model to evaluate the effect of feed location, pressure, feed composition, reflux ratio in the packed column for given reboiler and condenser duty of distillation column. State to stage modelling of two-phase two-component flow has constitutes the overall modelling of the column. The governing equations consist of stage-wise species and overall mass continuity and stage-wise energy balance. This results in tridigonal matrix equation for stage liquid fractions for heavy and light water. The stage-wise liquid flow rates and temperatures are governed by stage-wise mass and energy balance. The combined form of the corresponding governing equations, with the incorporation of thermodynamic equation of states, form a system of nonlinear equations. This system have been resolved numerically using modified Newton-Raphson method. A code in the MATLAB platform has been developed by on above numerical procedure. The optimisation of the column operating conditions is to be carried out based on parametric studies and analysis of different

  5. The evaluation of the bubble condenser containment of VVER-440/213 plants

    International Nuclear Information System (INIS)

    A number of pressurized water reactors of the VVER-440 type have a containment building which is connected to a bubble condenser unit reducing the design pressure of the entire containment system. The bubble condenser acts as a pressure suppression system by condensation of released steam. Some characteristic features of this system are presented. Refering to experience with the assessement of Western pressure suppression system containments of boiling water reactors (BWRs) the experimental and analytical background of the bubble condenser design has been studied. Several earlier test rigs located in the territory of the former Soviet Union and in other Eastern European countries have been studied and assessed. These test rigs served to prove the thermal efficiency of this arrangement. Characteristic properties of pressures suppression systems of Western BWRs are compared with the properties of bubble condensers and some existing test rigs. An international working group has identified a number of open questions for which neither experimental evidence nor sound analytical predictions exist. Of main interest are the response of bubble condenser structures to oscillatory condensation processes, the simultaneous interaction of a large number of gap-cap units and additionally some unresolved scale-up problems. Based on these findings a supplementary experimental research program has been proposed to answer these open questions. The suitability of existing test rigs and of a new experimental model have been assessed. The results are summarized. In view of the importance of the containment effectiveness for public safety the proposed research work deserves a high priority within a program to assist countries utilizing VVER-440 reactors in confirming an adequate level of reactor safety. (orig.)

  6. Stable bubble oscillations beyond Blake's critical threshold.

    Science.gov (United States)

    Hegedűs, Ferenc

    2014-04-01

    The equilibrium radius of a single spherical bubble containing both non-condensable gas and vapor is determined by the mechanical balance at the bubble interface. This expression highlights the fact that decreasing the ambient pressure below the so called Blake's critical threshold, the bubble has no equilibrium state at all. In the last decade many authors have tried to find evidence for the existence of stable bubble oscillation under harmonic forcing in this regime, that is, they have tried to stabilize the bubble motion applying ultrasonic radiation on the bubble. The available numerical results provide only partial proof for the existence as they are usually based on linearized or weakly nonlinear (higher order approximation) bubble models. Here, based on numerical techniques of the modern nonlinear and bifurcation theory, the existence of stable bubble motion has been proven without any restrictions in nonlinearities. Although the model, applied in this paper, is the rather simple Rayleigh-Plesset equation, the presented technique can be extended to more complex bubble models easily. PMID:24485747

  7. Bubble formation in additive manufacturing of glass

    Science.gov (United States)

    Luo, Junjie; Gilbert, Luke J.; Peters, Daniel C.; Bristow, Douglas A.; Landers, Robert G.; Goldstein, Jonathan T.; Urbas, Augustine M.; Kinzel, Edward C.

    2016-05-01

    Bubble formation is a common problem in glass manufacturing. The spatial density of bubbles in a piece of glass is a key limiting factor to the optical quality of the glass. Bubble formation is also a common problem in additive manufacturing, leading to anisotropic material properties. In glass Additive Manufacturing (AM) two separate types of bubbles have been observed: a foam layer caused by the reboil of the glass melt and a periodic pattern of bubbles which appears to be unique to glass additive manufacturing. This paper presents a series of studies to relate the periodicity of bubble formation to part scan speed, laser power, and filament feed rate. These experiments suggest that bubbles are formed by the reboil phenomena why periodic bubbles result from air being trapped between the glass filament and the substrate. Reboil can be detected using spectroscopy and avoided by minimizing the laser power while periodic bubbles can be avoided by a two-step laser melting process to first establish good contact between the filament and substrate before reflowing the track with higher laser power.

  8. Bubble burst as jamming phase transition

    CERN Document Server

    Nishinari, Katsuhiro; Saito, Yukiko Umeno; Watanabe, Tsutomu

    2010-01-01

    Recently research on bubble and its burst attract much interest of researchers in various field such as economics and physics. Economists have been regarding bubble as a disorder in prices. However, this research strategy has overlooked an importance of the volume of transactions. In this paper, we have proposed a bubble burst model by focusing the transactions incorporating a traffic model that represents spontaneous traffic jam. We find that the phenomenon of bubble burst shares many similar properties with traffic jam formation by comparing data taken from US housing market. Our result suggests that the transaction could be a driving force of bursting phenomenon.

  9. SELF-SIMILARITY OF VERTICAL BUBBLY JETS

    Directory of Open Access Journals (Sweden)

    I. E. Lima Neto

    2015-06-01

    Full Text Available AbstractAn integral model for vertical bubbly jets with nearly monodisperse bubble sizes is presented. The model is based on the Gaussian type self-similarity of mean liquid velocity, bubble velocity and void fraction, as well as on functional relationships for initial liquid jet velocity and radius, bubble diameter and relative velocity. Adjusting the model to experimental data available in the literature for a wide range of densimetric Froude numbers provide constant values for the entrainment coefficient, momentum amplification factor, and spreading ratio of the bubble core for different flow conditions. Consistency and sensitivity of key model parameters are also verified. Overall, the deviations between model predictions and axial/radial profiles of mean liquid velocity, bubble velocity and void fraction are lower than about 20%, which suggests that bubbly jets tend to behave as self-preserving shear flows, similarly to single-phase jets and plumes. Furthermore, model simulations indicate a behavior similar to those of single-phase buoyant jets and slurry jets, but some differences with respect to confined bubbly jets are highlighted. This article provides not only a contribution to the problem of self-similarity in two-phase jets, but also a comprehensive model that can be used for analysis of artificial aeration/mixing systems involving bubbly jets.

  10. General correlation for interfacial area concentration in bubbly flows

    International Nuclear Information System (INIS)

    Full text of publication follows: Although bubbly flows are encountered in various engineering fields, there are very few established theoretical foundations on the interfacial area concentration, which have been supported by extensive experimental data. From this point of view, a simple equation for the interfacial area concentration under steady fully-developed flow condition has been derived from the interfacial area transport equation. The derived theoretical equation has been modified to obtain experimentally supported predictive correlation. Important conclusions obtained from this study are summarized below. (1) The interfacial area concentration under steady fully-developed bubbly flow condition was derived from the interfacial area transport equation. The obtained equation was modified to obtain experimentally supported predictive correlation. (2) The obtained correlation of the interfacial area concentration was validated by 459 data sets measured in bubble columns and forced convective bubbly flows. These data sets covered extensive loop and flow conditions such as channel geometry (circular or rectangular channel), channel hydraulic equivalent diameter (9.0 mm ∼ 5500 mm), flow direction (vertical or horizontal flow), superficial gas velocity (0.000788 m/s ∼ 4.87 m/s), and superficial liquid velocity (0.00 m/s ∼ 6.55 m/s). The extensive database also covered wide ranges of physical properties such as liquid density (684 kg/m3 ∼ 1594 kg/m3), liquid viscosity (0.410 mPa.s ∼ 21.1 mPa.s), and surface tension (20.0 mN/m ∼ 75.0 mN/m). An excellent agreement was obtained between the developed semi-theoretical correlation and 459 data within an average relative deviation of ±21.4 %. (3) The applicability of the interfacial area correlation to developing flows was examined. As flow developed, the estimation error was getting better. As expected, the bubble breakup and coalescence might not be in equilibrium state near the channel inlet. However, if

  11. Revitalisation thermal column drive train control system

    International Nuclear Information System (INIS)

    Revitalisation thermal columns propulsion train control system is very urgent to be implemented because of the test results and observation, control system performance is not normal, there are several components that must be renewed. Components includes MCB, magnetic contactors, push buttons, indicator lights and wiring. Drive motor is used to power 1.5 kW 3 phase, 380 volts and 50 Hz, nominal current (In = 3.75 A). Thermal column is one of the irradiation facility at the Kartini reactor has a beam-shaped room of measuring 1.2 X 1.2 X 1.6 m contains graphite blocks 10.2 X 10.2 X 127 cm(1) and is tangentially connected to the Kartini reactor core. Graphite blocks mounted reflector extends from the outer side to the inner surface of the door closer. Door closer contains barite concrete as radiation shielding and can be moved forward and backward to close and to open using a rotating motor to spin the wheel transmission system for running on rails. (author)

  12. Porous layer open tubular columns with immobilized trypsin for protein digestion

    OpenAIRE

    Knob, R.

    2013-01-01

    We have developed a monolithic porous layer open tubular (PLOT) column with immobilized trypsin for protein digestion. The PLOT column was prepared in a 10 (mikro)m ID fused silica capillary. Trypsin was immobilized on the monolithic surface and the developed enzyme reactor was used for protein digestion followed by on-line ESI/MS analysis.

  13. Dynamics of Vapour Bubbles in Nucleate Boiling. 1; Basic Equations of Bubble Evolution

    Science.gov (United States)

    Buyevich, Yu A.; Webbon, Bruce W.; Callaway, Robert (Technical Monitor)

    1995-01-01

    We consider the behaviour of a vapour bubble formed at a nucleation site on a heated horizontal wall. There is no forced convection of an ambient liquid, and the bubble is presumably separated from the wall by a thin liquid microlayer. The energy conservation law results in a variational equation for the mechanical energy of the whole system consisting of the bubble and liquid. It leads to a set of two strongly nonlinear equations which govern bubble expansion and motion of its centre of mass. A supplementary equation to find out the vapour temperature follows from consideration of heat transfer to the bubble, both from the bulk of surrounding liquid and through the microlayer. The average thickness of the microlayer is shown to increase monotonously with time as the bubble meniscus spreads along the wall. Bubble expansion is driven by the pressure head between vapour inside and liquid far away from the bubble, with due allowance for surface tension and gravity effects. It is resisted by inertia of liquid being placed into motion as the bubble grows. The inertia originates also a force that presses the bubble to the wall. This force is counteracted by the buoyancy and an effective surface tension force that tends to transform the bubble into a sphere. The analysis brings about quite a new formulation of the familiar problem of bubble growth and detachment under conditions of nucleate pool boiling.

  14. Bubbles are more than you think - The Center for Information and Bubble Studies

    DEFF Research Database (Denmark)

    Hendricks, Vincent Fella

    2016-01-01

    dynamics of different bubble phenomena from finance over social media to politics and science in order to (1) formulate intervention strategies for malignant bubbles from “shitstorms” to radicalisation, stimulate possible benign bubbles from climate awareness to democratic initiatives and thus play a...... proactive role promoting scientific social responsibility (SSR)....

  15. Measurement of interfacial structures in horizontal air-water bubbly flows

    International Nuclear Information System (INIS)

    In order to predict multi-dimensional phenomena in nuclear reactor systems, methods relying on computational fluid dynamics (CFD) codes are essential. However, to be applicable in assessing thermal-hydraulic safety, these codes must be able to accurately predict the development of two-phase flows. Therefore, before practical application these codes must be assessed using experimental databases that capture multi-dimensional phenomena. While a large database exists that can be employed to assess predictions in vertical flows, the available database for horizontal flows is significantly lacking. Therefore, the current work seeks to develop an additional database in air-water horizontal bubbly flow through a 38.1 mm ID test section with a total development length of approximately 250 diameters. The experimental conditions are chosen to cover a wide range of the bubbly flow regime based upon flow visualization using a high-speed video camera. A database of local time-averaged void fraction, bubble velocity, interfacial area concentration, and bubble Sauter mean diameter are acquired throughout the pipe cross-section using a four-sensor conductivity probe. To investigate the evolution of the flow, measurements are made at axial locations of 44, 116, and 244 diameters downstream of the inlet. In the current work, only measurements obtained at L/D = 244 are presented. It is found that increasing the liquid superficial velocity tends to reduce both the bubble size and the degree of bubble packing near the upper wall. However, it is observed that the position of the maximum void fraction value remains nearly constant and is located approximately one bubble diameter away from the upper wall. It is also found that the bubble velocity exhibits a power law behavior resembling a single phase liquid turbulent velocity profile. Moreover, the local bubble velocity tends to decrease as the local void fraction increases. Conversely, increasing the gas superficial velocity is found to

  16. Giant bubble pinch-off

    OpenAIRE

    Bergmann, Raymond; Meer, Van Der; Stijnman, Mark; Sandtke, Marijn; Prosperetti, Andrea; Lohse, Detlef

    2006-01-01

    Self-similarity has been the paradigmatic picture for the pinch-off of a drop. Here we will show through high-speed imaging and boundary integral simulations that the inverse problem, the pinch-off of an air bubble in water, is not self-similar in a strict sense: A disk is quickly pulled through a water surface, leading to a giant, cylindrical void which after collapse creates an upward and a downward jet. Only in the limiting case of large Froude numbers does the purely inertial scaling h(-l...

  17. Biosynthesis within a bubble architecture

    Science.gov (United States)

    Choi, Hyo-Jick; Montemagno, Carlo D.

    2006-05-01

    Sub-cellular compartmentalization is critical to life; it minimizes diffusion effects and enables locally high concentrations of biochemicals for improved reaction kinetics. We demonstrate an example of in vitro biochemical synthesis inside the water channels of foam using engineered artificial organelles (bacteriorhodopsin and F0F1-ATP synthase reconstituted polymer vesicles) as functional units to produce ATP. These results show that the interstitial space of bubbles serves as a metaphor for sub-cellular structure, providing a new platform for both investigating cellular metabolism and the engineering of biofunctional materials and systems.

  18. Stationary bubbles: information loss paradox?

    CERN Document Server

    Domènech, Guillem

    2016-01-01

    The main purpose of this work is to build classically stationary bubbles, within the thin-shell formalism, which are unstable under quantum effects; they either collapse into a black hole or expand. Thus, the final state can be thought of a superposition of geometries. We point out that, from a quantum mechanical point of view, there is no issue with a loss of information in such configuration. A classical observer sees a definite geometry and, hence, finds an effective loss of information. Although it does not cover all possible cases, we emphasise the role of semi-classical gravitational effects, mediated by instatons, in alleviating/solving the information loss paradox.

  19. Strength degradation of oxidized graphite support column in VHTR

    International Nuclear Information System (INIS)

    Air-ingress events caused by large pipe breaks are important accidents considered in the design of Very High Temperature Gas-Cooled Reactors (VHTRs). A main safety concern for this type of event is the possibility of core collapse following the failure of the graphite support column, which can be oxidized by ingressed air. In this study, the main target is to predict the strength of the oxidized graphite support column. Through compression tests for fresh and oxidized graphite columns, the compressive strength of IG-110 was obtained. The buckling strength of the IG-110 column is expressed using the following empirical straight-line formula: σcr,buckling=91.34-1.01(L/r). Graphite oxidation in Zone 1 is volume reaction and that in Zone 3 is surface reaction. We notice that the ultimate strength of the graphite column oxidized in Zones 1 and 3 only depends on the slenderness ratio and bulk density. Its strength degradation oxidized in Zone 1 is expressed in the following nondimensional form: σ/σ0=exp(-kd), k=0.114. We found that the strength degradation of a graphite column, oxidized in Zone 3, follows the above buckling empirical formula as the slenderness of the column changes. (author)

  20. One meter holographic bubble chamber for TEVATRON neutrino experiments

    International Nuclear Information System (INIS)

    A one meter holographic bubble chamber was constructed for Fermilab TEVATRON neutrino experiments. Bubble chamber and optics are briefly outlined. Developments in holography for this bubble chamber and two types of reconstruction projectors are reported. (orig.)

  1. Assessment of bubble-borne methane emissions in the East Siberian Arctic Shelf via interpretation of sonar data

    Science.gov (United States)

    Chernykh, D.; Leifer, I.; Shakhova, N. E.; Semiletov, I. P.

    2014-12-01

    Arctic warming is proposed to increase methane emissions from submerged permafrost driving a positive feedback. Where emissions are from shallow seas, bubbles transport much of the methane directly, while frequent Arctic storms sparge much of the remaining dissolved methane before microbes can oxidize it. Complexity arises where emissions are small bubbles or from deeper water due to dissolution below the storm-mixed layer. Given that these emissions span a wide geographic area, a promising remote sensing technology that has been used to map and estimate emissions; however, significant uncertainties exist in sonar data interpretation due to a range of parameters affecting sonar return including bubble size distribution and spatial distribution, vertical velocity, and temperature all of which are closely inter-related in a complex and at best poorly understood manner, and change as the bubble plume rises. This process was illustrated in a series of in situ calibration experiments in the East Siberian Arctic Sea (ESAS) where controlled air bubble plumes were created and observed with sonar to quantify the relationship between sonar return and bubble plume flux for a first calibration of in situ sonar bubble plume observations in the ESAS. Results highlight the importance of bubble plume dynamics to sonar return and the absence of a simple relationship between sonar return and bubble flux. Instead sonar return related to height above seabed, even accounting for dissolution and changing hydrostatic pressure, confirming earlier laboratory studies for a deeper water column. Calibrations then were applied to field data of an area of ESAS natural seepage.

  2. Giant bubble pinch-off

    CERN Document Server

    Bergmann, R; Prosperetti, A; Sandtke, M; Stijnman, M; Van der Meer, D; Bergmann, Raymond; Lohse, Detlef; Meer, Devaraj van der; Prosperetti, Andrea; Sandtke, Marijn; Stijnman, Mark

    2006-01-01

    Self-similarity has been the paradigmatic picture for the pinch-off of a drop. Here we will show through high-speed imaging and boundary integral simulations that the inverse problem, the pinch-off of an air bubble in water, is not self-similar in a strict sense: A disk is quickly pulled through a water surface, leading to a giant, cylindrical void which after collapse creates an upward and a downward jet. Only in the limiting case of large Froude number the neck radius $h$ scales as $h(-\\log h)^{1/4} \\propto \\tau^{1/2}$, the purely inertial scaling. For any finite Froude number the collapse is slower, and a second length-scale, the curvature of the void, comes into play. Both length-scales are found to exhibit power-law scaling in time, but with different exponents depending on the Froude number, signaling the non-universality of the bubble pinch-off.

  3. Cavitation inception from bubble nuclei.

    Science.gov (United States)

    Mørch, K A

    2015-10-01

    The tensile strength of ordinary water such as tap water or seawater is typically well below 1 bar. It is governed by cavitation nuclei in the water, not by the tensile strength of the water itself, which is extremely high. Different models of the nuclei have been suggested over the years, and experimental investigations of bubbles and cavitation inception have been presented. These results suggest that cavitation nuclei in equilibrium are gaseous voids in the water, stabilized by a skin which allows diffusion balance between gas inside the void and gas in solution in the surrounding liquid. The cavitation nuclei may be free gas bubbles in the bulk of water, or interfacial gaseous voids located on the surface of particles in the water, or on bounding walls. The tensile strength of these nuclei depends not only on the water quality but also on the pressure-time history of the water. A recent model and associated experiments throw new light on the effects of transient pressures on the tensile strength of water, which may be notably reduced or increased by such pressure changes. PMID:26442138

  4. Differential criterion of a bubble collapse in viscous liquids

    CERN Document Server

    Bogoyavlenskiy, V A

    1999-01-01

    The present work is devoted to a model of bubble collapse in a Newtonian viscous liquid caused by an initial bubble wall motion. The obtained bubble dynamics described by an analytic solution significantly depends on the liquid and bubble parameters. The theory gives two types of bubble behavior: collapse and viscous damping. This results in a general collapse condition proposed as the sufficient differential criterion. The suggested criterion is discussed and successfully applied to the analysis of the void and gas bubble collapses.

  5. Galactic Teamwork Makes Distant Bubbles

    Science.gov (United States)

    Kohler, Susanna

    2016-03-01

    During the period of reionization that followed the dark ages of our universe, hydrogen was transformed from a neutral state, which is opaque to radiation, to an ionized one, which is transparent to radiation. But what generated the initial ionizing radiation? The recent discovery of multiple distant galaxies offers evidence for how this process occurred.Two Distant GalaxiesWe believe reionization occurred somewhere between a redshift of z = 6 and 7, because Ly-emitting galaxies drop out at roughly this redshift. Beyond this distance, were generally unable to see the light from these galaxies, because the universe is no longer transparent to their emission. This is not always the case, however: if a bubble of ionized gas exists around a distant galaxy, the radiation can escape, allowing us to see the galaxy.This is true of two recently-discovered Ly-emitting galaxies, confirmed to be at a redshift of z~7 and located near one another in a region known as the Bremer Deep Field. The fact that were able to see the radiation from these galaxies means that they are in an ionized HII region presumably one of the earlier regions to have become reionized in the universe.But on their own, neither of these galaxies is capable of generating an ionized bubble large enough for their light to escape. So what ionized the region around them, and what does this mean for our understanding of how reionization occurred in the universe?A Little Help From FriendsLocation in different filters of the objects in the Hubble Bremer Deep Field catalog. The z~7 selection region is outlined by the grey box. BDF-521 and BDF-3299 were the two originally discovered galaxies; the remaining red markers indicate the additional six galaxies discovered in the same region. [Castellano et al. 2016]A team of scientists led by Marco Castellano (Rome Observatory, INAF) investigated the possibility that there are other, faint galaxies near these two that have helped to ionize the region. Performing a survey

  6. Financial frictions, bubbles, and macroprudential policies

    OpenAIRE

    Derviz, Alexis

    2011-01-01

    Writer explores the ability of a macroprudential policy instrument to dampen the consequences of equity mispricing (a bubble) and the correction thereof (the bubble bursting), as well as the consequences for real activity in a production economy. In the model, producers are financed by both bank debt and equity, and face a mix of systemic and idiosyncratic uncertainty.

  7. Gravity Wave Seeding of Equatorial Plasma Bubbles

    Science.gov (United States)

    Singh, Sardul; Johnson, F. S.; Power, R. A.

    1997-01-01

    Some examples from the Atmosphere Explorer E data showing plasma bubble development from wavy ion density structures in the bottomside F layer are described. The wavy structures mostly had east-west wavelengths of 150-800 km, in one example it was about 3000 km. The ionization troughs in the wavy structures later broke up into either a multiple-bubble patch or a single bubble, depending upon whether, in the precursor wavy structure, shorter wavelengths were superimposed on the larger scale wavelengths. In the multiple bubble patches, intrabubble spacings vaned from 55 km to 140 km. In a fully developed equatorial spread F case, east-west wavelengths from 690 km down to about 0.5 km were present simultaneously. The spacings between bubble patches or between bubbles in a patch appear to be determined by the wavelengths present in the precursor wave structure. In some cases, deeper bubbles developed on the western edge of a bubble patch, suggesting an east-west asymmetry. Simultaneous horizontal neutral wind measurements showed wavelike perturbations that were closely associated with perturbations in the plasma horizontal drift velocity. We argue that the wave structures observed here that served as the initial seed ion density perturbations were caused by gravity waves, strengthening the view that gravity waves seed equatorial spread F irregularities.

  8. Laminar separation bubbles: Dynamics and control

    Indian Academy of Sciences (India)

    Sourabh S Diwan; O N Ramesh

    2007-02-01

    This work is an experimental investigation of the dynamics and control of the laminar separation bubbles which are typically present on the suction surface of an aerofoil at a large angle of attack. A separation bubble is produced on the upper surface of a flat plate by appropriately contouring the top wall of the wind tunnel. First, a basic (unforced) separation bubble is obtained to set a benchmark for further experiments. Parametric study is done where the reference velocity is decreased to quantify its effect on the aspect ratio of the bubble. It is found that with decrease in Reynolds number, the height of the bubble increases at a greater rate than the length. This feature could be useful in characterising separation bubbles especially from the point of view of low Reynolds number aerofoil design. Artificial disturbance is introduced at two different initial amplitudes (infinitesimal and finite) upstream of separation location and hotwire anemometry is used to trace the wave packet as it is advected downstream. The evolution of wave packets is seen to take place in two distinct stages. Finite amplitude forcing causes periodic quenching of the bubble. Interestingly, even an infinitesimally small forcing is seen to modify and thereby control the separation bubble.

  9. Steady State Vapor Bubble in Pool Boiling

    Science.gov (United States)

    Zou, An; Chanana, Ashish; Agrawal, Amit; Wayner, Peter C.; Maroo, Shalabh C.

    2016-02-01

    Boiling, a dynamic and multiscale process, has been studied for several decades; however, a comprehensive understanding of the process is still lacking. The bubble ebullition cycle, which occurs over millisecond time-span, makes it extremely challenging to study near-surface interfacial characteristics of a single bubble. Here, we create a steady-state vapor bubble that can remain stable for hours in a pool of sub-cooled water using a femtosecond laser source. The stability of the bubble allows us to measure the contact-angle and perform in-situ imaging of the contact-line region and the microlayer, on hydrophilic and hydrophobic surfaces and in both degassed and regular (with dissolved air) water. The early growth stage of vapor bubble in degassed water shows a completely wetted bubble base with the microlayer, and the bubble does not depart from the surface due to reduced liquid pressure in the microlayer. Using experimental data and numerical simulations, we obtain permissible range of maximum heat transfer coefficient possible in nucleate boiling and the width of the evaporating layer in the contact-line region. This technique of creating and measuring fundamental characteristics of a stable vapor bubble will facilitate rational design of nanostructures for boiling enhancement and advance thermal management in electronics.

  10. Steady State Vapor Bubble in Pool Boiling.

    Science.gov (United States)

    Zou, An; Chanana, Ashish; Agrawal, Amit; Wayner, Peter C; Maroo, Shalabh C

    2016-01-01

    Boiling, a dynamic and multiscale process, has been studied for several decades; however, a comprehensive understanding of the process is still lacking. The bubble ebullition cycle, which occurs over millisecond time-span, makes it extremely challenging to study near-surface interfacial characteristics of a single bubble. Here, we create a steady-state vapor bubble that can remain stable for hours in a pool of sub-cooled water using a femtosecond laser source. The stability of the bubble allows us to measure the contact-angle and perform in-situ imaging of the contact-line region and the microlayer, on hydrophilic and hydrophobic surfaces and in both degassed and regular (with dissolved air) water. The early growth stage of vapor bubble in degassed water shows a completely wetted bubble base with the microlayer, and the bubble does not depart from the surface due to reduced liquid pressure in the microlayer. Using experimental data and numerical simulations, we obtain permissible range of maximum heat transfer coefficient possible in nucleate boiling and the width of the evaporating layer in the contact-line region. This technique of creating and measuring fundamental characteristics of a stable vapor bubble will facilitate rational design of nanostructures for boiling enhancement and advance thermal management in electronics. PMID:26837464

  11. Analytical solutions for problems of bubble dynamics

    CERN Document Server

    Kudryashov, Nikolai A

    2016-01-01

    Recently, an asymptotic solution of the Rayleigh equation for an empty bubble in $N$ dimensions has been obtained. Here we give the closed--from general analytical solution of this equation. We also find the general solution of the Rayleigh equation in $N$ dimensions for the case of a gas--filled hyperspherical bubble. In addition, we include a surface tension into consideration.

  12. Measuring the surface tension of soap bubbles

    Science.gov (United States)

    Sorensen, Carl D.

    1992-01-01

    The objectives are for students to gain an understanding of surface tension, to see that pressure inside a small bubble is larger than that inside a large bubble. These concepts can be used to explain the behavior of liquid foams as well as precipitate coarsening and grain growth. Equipment, supplies, and procedures are explained.

  13. Liquid-liquid contractor columns

    International Nuclear Information System (INIS)

    A liquid-liquid contactor column has a solvent input and an aqueous phase input. Lighter phase liquid is discharged and heavier phase is moved by an air lift to a receiver. The air supply line to the air lift includes valve and a pressure sensing transducer senses pressure in line and sends electric signals to signal processing unit which may for example close down operation of the column, or effect other changes to maintain operating characteristics of the column. The column could be pulsed by means which also send signals to unit, and could deliver to an external settler. (author)

  14. Magma mixing enhanced by bubble segregation

    Science.gov (United States)

    Wiesmaier, S.; Morgavi, D.; Renggli, C. J.; Perugini, D.; De Campos, C. P.; Hess, K.-U.; Ertel-Ingrisch, W.; Lavallée, Y.; Dingwell, D. B.

    2015-08-01

    In order to explore the materials' complexity induced by bubbles rising through mixing magmas, bubble-advection experiments have been performed, employing natural silicate melts at magmatic temperatures. A cylinder of basaltic glass was placed below a cylinder of rhyolitic glass. Upon melting, bubbles formed from interstitial air. During the course of the experimental runs, those bubbles rose via buoyancy forces into the rhyolitic melt, thereby entraining tails of basaltic liquid. In the experimental run products, these plume-like filaments of advected basalt within rhyolite were clearly visible and were characterised by microCT and high-resolution EMP analyses. The entrained filaments of mafic material have been hybridised. Their post-experimental compositions range from the originally basaltic composition through andesitic to rhyolitic composition. Rheological modelling of the compositions of these hybridised filaments yield viscosities up to 2 orders of magnitude lower than that of the host rhyolitic liquid. Importantly, such lowered viscosities inside the filaments implies that rising bubbles can ascend more efficiently through pre-existing filaments that have been generated by earlier ascending bubbles. MicroCT imaging of the run products provides textural confirmation of the phenomenon of bubbles trailing one another through filaments. This phenomenon enhances the relevance of bubble advection in magma mixing scenarios, implying as it does so, an acceleration of bubble ascent due to the decreased viscous resistance facing bubbles inside filaments and yielding enhanced mass flux of mafic melt into felsic melt via entrainment. In magma mixing events involving melts of high volatile content, bubbles may be an essential catalyst for magma mixing. Moreover, the reduced viscosity contrast within filaments implies repeated replenishment of filaments with fresh end-member melt. As a result, complex compositional gradients and therefore diffusion systematics can be

  15. CO observations of the Galactic bubble N4

    Institute of Scientific and Technical Information of China (English)

    Jun-Yu Li; Zhi-Bo Jiang; Yao Liu; Yuan Wang

    2013-01-01

    We present a study of the Galactic bubble N4 using the 13.7 m millimeterwave telescope,which is managed by Purple Mountain Observatory at Qinghai Station.N4 is one of the science demonstration regions where simultaneous observations of 12CO (J =1-0),13CO (J =1-0) and C18O (J =1-0) line emission towards N4 were carried out under the project Milky Way Imaging Scroll Painting (MWISP).We analyze the spectral profile and the distribution of the molecular gas.Morphologically,the CO emissions correlate well with Spitzer IRAC 8.0 μm emission.The channel map and velocity-position diagram show that N4 is more likely to be an inclined expanding ring rather than a spherical bubble.We calculated the physical parameters of N4 including mass,size,column density and optical depth.Some massive star candidates were discovered in the region of N4 using the (J,J-H) colormagnitude diagram.We found a candidate for the energy source driving the expansion of N4,a massive star with a mass of ~15 M☉ and an age of ~ 1 Myr.There is the signature of infall motion in N4,which can be a good candidate for the infall area.Combining millimeter and infrared data,we suggest that triggered star formation can exist in N4.

  16. CO observation of the Galactic bubble N4

    CERN Document Server

    Li, Junyu; Liu, Yao; Wang, Yuan

    2013-01-01

    We presented a study on the Galactic bubble N4 using the 13.7 m millimeter telescope of Purple Mountain Observatory at the Qinghai Station. N4 is one of the science demonstration regions for the Milky Way Imaging Scroll Painting (WMISP). Simultaneous observations of $^{12}$CO (J = 1$-$0), $^{13}$CO (J = 1$-$0) and C$^{18}$O (J = 1$-$0) line emission towards N4 were carried out. We analyzed the spectral profile and the distribution of the molecular gas. Morphologically, the CO emissions correlate well with Spitzer IRAC 8.0 $\\mu$m emission. The channel map and velocity-position diagram shows that N4 is more likely an inclined expanding ring than a spherical bubble. We calculated the physical parameters of N4 including the mass, size, column density and optical depth. Some massive star candidates were discovered in the region of N4 using (J, J$-$H) color-magnitude diagram. We found an energy source candidate for the expansion of N4, a massive star with a mass of ${\\sim} 15\\,M_{\\odot}$ and an age of $\\sim$ 1 Myr....

  17. Method for enhancing selectivity and recovery in the fractional flotation of particles in a flotation column

    Science.gov (United States)

    Klunder, Edgar B.

    2011-08-09

    The method relates to particle separation from a feed stream. The feed stream is injected directly into the froth zone of a vertical flotation column in the presence of a counter-current reflux stream. A froth breaker generates a reflux stream and a concentrate stream, and the reflux stream is injected into the froth zone to mix with the interstitial liquid between bubbles in the froth zone. Counter-current flow between the plurality of bubbles and the interstitial liquid facilitates the attachment of higher hydrophobicity particles to bubble surfaces as lower hydrophobicity particles detach. The height of the feed stream injection and the reflux ratio may be varied in order to optimize the concentrate or tailing stream recoveries desired based on existing operating conditions.

  18. Solar prominences: 'double, double ... boil and bubble'

    CERN Document Server

    Keppens, Rony

    2015-01-01

    Observations revealed rich dynamics within prominences, the cool 10,000 K, macroscopic (sizes of order 100 Mm) "clouds" in the million degree solar corona. Even quiescent prominences are continuously perturbed by hot, rising bubbles. Since prominence matter is hundredfold denser than coronal plasma, this bubbling is related to Rayleigh-Taylor instabilities. Here we report on true macroscopic simulations well into this bubbling phase, adopting a magnetohydrodynamic description from chromospheric layers up to 30 Mm height. Our virtual prominences rapidly establish fully non-linear (magneto)convective motions where hot bubbles interplay with falling pillars, with dynamical details including upwelling pillars forming within bubbles. Our simulations show impacting Rayleigh-Taylor fingers reflecting on transition region plasma, ensuring that cool, dense chromospheric material gets mixed with prominence matter up to very large heights. This offers an explanation for the return mass cycle mystery for prominence mater...

  19. Bubble growth and rise in soft sediments

    Science.gov (United States)

    Boudreau, Bernard P.; Algar, Chris; Johnson, Bruce D.; Croudace, Ian; Reed, Allen; Furukawa, Yoko; Dorgan, Kelley M.; Jumars, Peter A.; Grader, Abraham S.; Gardiner, Bruce S.

    2005-06-01

    The mechanics of uncemented soft sediments during bubble growth are not widely understood and no rheological model has found wide acceptance. We offer definitive evidence on the mode of bubble formation in the form of X-ray computed tomographic images and comparison with theory. Natural and injected bubbles in muddy cohesive sediments are shown to be highly eccentric oblate spheroids (disks) that grow either by fracturing the sediment or by reopening preexisting fractures. In contrast, bubbles in soft sandy sediment tend to be spherical, suggesting that sand acts fluidly or plastically in response to growth stresses. We also present bubble-rise results from gelatin, a mechanically similar but transparent medium, that suggest that initial rise is also accomplished by fracture. Given that muddy sediments are elastic and yield by fracture, it becomes much easier to explain physically related phenomena such as seafloor pockmark formation, animal burrowing, and gas buildup during methane hydrate melting.

  20. Oscillation of large air bubble cloud

    Energy Technology Data Exchange (ETDEWEB)

    Bae, Y.Y.; Kim, H.Y.; Park, J.K. [Korea Atomic Energy Research Inst., Daejeon (Korea, Republic of)

    2001-07-01

    The behavior of a large air bubble cloud, which is generated by the air discharged from a perforated sparger, is analyzed by solving Rayleigh-Plesset equation, energy equations and energy balance equation. The equations are solved by Runge-Kutta integration and MacCormack finite difference method. Initial conditions such as driving pressure, air volume, and void fraction strongly affect the bubble pressure amplitude and oscillation frequency. The pool temperature has a strong effect on the oscillation frequency and a negligible effect on the pressure amplitude. The polytropic constant during the compression and expansion processes of individual bubbles ranges from 1.0 to 1.4, which may be attributed to the fact that small bubbles oscillated in frequencies different from their resonance. The temperature of the bubble cloud rapidly approaches the ambient temperature, as is expected from the polytropic constants being between 1.0 and 1.4. (authors)