WorldWideScience

Sample records for bubbling fluidised bed

  1. Experimental study of bubbling fluidised bed co-combustion of Spanish lignite with PVC

    Energy Technology Data Exchange (ETDEWEB)

    J.M. Sanchez; L. Armesto; E. Ruiz; J. Otero [CIEMAT, Madrid (Spain). Fossil Fuels Department

    2005-07-01

    This work presents preliminary results obtained in the co-combustion of subbituminous coal from Puertollano (Spain) and recycled PVC. Pilot scale cocombustion tests have been carried out in a 0,5 MWth Bubbling Fluidised Bed Combustor (BFBC). The effects of temperature, in the range from 800 to 880{sup o}C, and PVC content (5-10% w/w) are studied. Gas monitoring programme has taken into account major gas components and pollutants as well as isokinetic sampling for the collection of PCDD/F according to standard methods. Ashes have been characterised using ASTM standard methods. Results have been analysed in terms of combustion efficiency, major pollutants emission and PCDD/Fs formation, both in the flue gas and in the fly ash. Results show that the addition of PVC to coal leads to low combustion efficiency. Fuel composition and operating conditions affect PCDD/Fs release. Distribution of PCDD/Fs in flue gas and in fly ash shows a dominance of lower chlorinated homologues. 11 refs., 10 figs., 7 tabs.

  2. PCDD/PCDF emissions from co-combustion of coal and PVC in a bubbling fluidised bed boiler

    Energy Technology Data Exchange (ETDEWEB)

    J.M. Sanchez-Hervas; L. Armesto; E. Ruiz-Martinez; J. Otero-Ruiz; M. Pandelova; K.W. Schramm [CIEMAT, Madrid (Spain). Fossil Fuels Department

    2005-12-01

    This paper reports on the results obtained in the study of the co-combustion of PVC with hard coal from South Africa in a 0,5 MWth Bubbling Fluidised Bed Boiler. The research has included the study of the effect of combustion temperature, fluidisation velocity and PVC content. The addition of urea to the raw fuel, as a dioxin-preventing compound has also been evaluated. Results have been analysed in terms of combustion efficiency, major pollutants emission (NOx, CO), and PCDD/Fs formation in the flue gas and in the fly ash. Under the experimental conditions tested, co-combustion of coal and PVC has proved to be feasible from the combustion efficiency and emission of PCDD/Fs points of view, whose levels remained below limits set by existing legislation on persistent organic pollutants. The addition of solid urea to the fuel blend reduces the amount of chlorinated compounds emitted. However, it has a negative impact on nitrogen pollutants formation. 19 refs., 12 figs., 5 tabs.

  3. Characterisation of coal and chars in fluidised bed gasification

    CSIR Research Space (South Africa)

    Oboirien, BO

    2009-03-01

    Full Text Available temperature range of 900 to 935oC. Char residual remaining after atmospheric gasification in a pilot plant bubbling fluidised bed reactor were analysed by petrographic techniques, X-ray diffraction, scanning electron microscopy (SEM), EDX, Raman spectroscopy...

  4. Fluidised-bed combustion of gasification residue

    Energy Technology Data Exchange (ETDEWEB)

    Korpela, T.; Kudjoi, A.; Hippinen, I.; Heinolainen, A.; Suominen, M.; Lu Yong [Helsinki Univ. of Technology (Finland). Lab of Energy Economics and Power Plant Engineering

    1996-12-01

    Partial gasification processes have been presented as possibilities for future power production. In the processes, the solid materials removed from a gasifier (i.e. fly ash and bed material) contain unburnt fuel and the fuel conversion is increased by burning this gasification residue either in an atmospheric or a pressurised fluidised-bed. In this project, which is a part of European JOULE 2 EXTENSION research programme, the main research objectives are the behaviour of calcium and sulphur compounds in solids and the emissions of sulphur dioxide and nitrogen oxides (NO{sub x} and N{sub 2}O) in pressurised fluidised-bed combustion of gasification residues. (author)

  5. Making the most of South Africa’s low-quality coal: Converting high-ash coal to fuel gas using bubbling fluidised bed gasifiers

    CSIR Research Space (South Africa)

    Engelbrecht, AD

    2010-08-31

    Full Text Available South Africa has abundant resources of high-ash and other low-quality coals. The aim of this work is to investigate the possibility of using fluidised bed gasification technology to convert these coals into clean fuel gas. The fuel gas can be used...

  6. Discrete particle simulation of bubble and slug formation in a two-dimensional gas-fluidised bed: A hard-sphere approach.

    NARCIS (Netherlands)

    Hoomans, B.P.B.; Kuipers, J.A.M.; Briels, Willem J.; van Swaaij, Willibrordus Petrus Maria

    1996-01-01

    A discrete particle model of a gas-fluidised bed has been developed and in this the two-dimensional motion of the individual, spherical particles was directly calculated from the forces acting on them, accounting for the interaction between the particles and the interstitial gas phase. Our collision

  7. Modeling and Simulation of a lab-scale Fluidised Bed

    Directory of Open Access Journals (Sweden)

    Britt Halvorsen

    2002-04-01

    Full Text Available The flow behaviour of a lab-scale fluidised bed with a central jet has been simulated. The study has been performed with an in-house computational fluid dynamics (CFD model named FLOTRACS-MP-3D. The CFD model is based on a multi-fluid Eulerian description of the phases, where the kinetic theory for granular flow forms the basis for turbulence modelling of the solid phases. A two-dimensional Cartesian co-ordinate system is used to describe the geometry. This paper discusses whether bubble formation and bed height are influenced by coefficient of restitution, drag model and number of solid phases. Measurements of the same fluidised bed with a digital video camera are performed. Computational results are compared with the experimental results, and the discrepancies are discussed.

  8. Fungi solubilisation of low rank coal: performances of stirred tank, fluidised bed and packed bed reactors

    CSIR Research Space (South Africa)

    Oboirien, BO

    2013-02-01

    Full Text Available Coal biosolubilisation was investigated in stirred tank reactor, fluidised bed and fixed bed bioreactors with a view to highlight the advantages and shortcomings of each of these reactor configurations. The stirred aerated bioreactor and fluidised...

  9. Fluidised bed gasification of South African coals – experimental results and process integration

    CSIR Research Space (South Africa)

    Engelbrecht, A

    2011-06-01

    Full Text Available high-ash coal from the Waterberg coalfield was tested in a bubbling fluidised bed gasifier at the CSIR using various gasification agents and operating conditions. The results of the tests show that when air and steam are used as the gasification agents...

  10. Fluidised bed gasification of low grade South African coals

    CSIR Research Space (South Africa)

    North, BC

    2006-09-01

    Full Text Available -going investigation into one potential Clean Coal Technology (CCT), namely fluidised bed gasification. Coal gasification holds the potential benefits of increased efficiency, reduced water consumption and co-production of liquid and gaseous fuels and chemicals...

  11. Studies of carbonaceous cenospheres from fluidised-bed combustors

    NARCIS (Netherlands)

    Gay, A.J.; Littlejohn, R.F.; Duin, P.J. van

    1984-01-01

    FIy ash from fluidised bed combustion of bituminous coals contains carbonaceous cenospheres of several forms including thick-walled opaque, transparent with a skeletal structure and 'balloons' without skeletons. The influence on cenosphere formation of particle size, temperature, heating rate,

  12. Hydrodynamic modelling of dense gas-fluidised beds: comparison and validation of 3D discrete particle and continuum models

    NARCIS (Netherlands)

    Goldschmidt, M.J.V.; Beetstra, R.; Kuipers, J.A.M.

    2004-01-01

    A critical comparison of a hard-sphere discrete particle model, a two-fluid model with kinetic theory closure equations and experiments performed in a pseudo-two-dimensional gas-fluidised bed is made. Bubble patterns, time-averaged particle distributions and bed expansion dynamics measured with a

  13. Pyrolysis of brominated feedstock plastic in a fluidised bed reactor

    OpenAIRE

    Hall, W.J.; Williams, P.T.

    2006-01-01

    Fire retarded high impact polystyrene has been pyrolysed using a fluidised bed reactor with a sand bed. The yield and composition of the products have been investigated in relation to fluidised bed temperature. The bromine distribution between the products and a detailed analysis of the oils using GC-FID/ECD, GC-MS, FT-ir, and size exclusion chromatography has been carried out. It was found that the majority of the bromine transfers to the pyrolysis oil and the antimony was detected in both t...

  14. Model-based operational constraints for fluidised bed crystallisation.

    Science.gov (United States)

    van Schagen, K M; Rietveld, L C; Babuska, R; Kramer, O J I

    2008-01-01

    Fluidised bed reactors are used for water softening in water treatment plants. Recent research shows that under current operation of reactors the crystallisation of calcium carbonate can be hampered. Until now the operational constraints on the fluidised bed have not been exactly known. Experiments were carried out to investigate the fluidisation behaviour of calcium carbonate pellets in water. The results of the fluidisation experiments are compared to two commonly used modelling approaches of Ergun and Richardon-Zaki. Using the experimental data the models are calibrated. The calibrated Richardson-Zaki model is used to determine operational constraints on pellet size at the bottom of the reactor and water flow through the reactor. The model-based constraints are compared to operational data of the Weesperkarspel full-scale treatment plant of Waternet (The Netherlands). It can be concluded that the current operation of the treatment plant violates the calculated constraints with consequences for effluent quality and corrective maintenance. By using models for determining the operation of the fluidised bed, the softening process can thus be improved.

  15. A simplified approach to the drying of solids in a batch fluidised bed

    Directory of Open Access Journals (Sweden)

    C. Srinivasakannan

    2002-07-01

    Full Text Available A simplified model for drying solids in the constant rate period in a batch fluidised bed was developed.It assumes the bed to be divided into dense and bubble phases with heat and mass transfer between the phases.The model predicts the constant-rate drying period, provided the fluid bed shape and material characteristics are known.The model is compared with experimental data reported in the literature covering a wide range of materials, gas flow rates, column diameters, material hold-ups, air temperatures and humidities.Model predictions compare satisfactorily with the experimental data.

  16. Study on the structure and gasification characteristics of selected South African bituminous coal in fluidised bed gasification

    CSIR Research Space (South Africa)

    Oboirien, BO

    2009-10-01

    Full Text Available The gasification characteristics of three South African bituminous coals were investigated in a bubbling fluidised bed reactor. The three coals are similar in rank, but two are inertinite-rich coals and the third has high vitrinite content...

  17. Study on the structure and gasification characteristics of selected South African bituminous coals in fluidised bed gasification

    CSIR Research Space (South Africa)

    Oboirien, BO

    2011-04-01

    Full Text Available The gasification characteristics of three South African bituminous coals were investigated in a bubbling fluidised bed reactor. The three coals are similar in rank, but two are inertinite-rich coals and the third has a high vitrinite content...

  18. Fluidised Bed Combustion: A Novel Technology for the Combustion ...

    African Journals Online (AJOL)

    A firing technology, which is increasingly becoming popular for the combustion of fuels with difficult combustion properties, is fluidised bed combustion (FBC). In the current paper, the special features of FBC have been reviewed and their advantages as compared to conventional firing systems highlighted. This has been ...

  19. Sustainable nitrification in fluidised bed reactor with immobilised ...

    African Journals Online (AJOL)

    Sustainable nitrification in fluidised bed reactor with immobilised sludge pellets. Y Wang, W Zhou, Z Li, W Wu, Z Zhang. Abstract. Sustainable immobilised microbial pellets were developed with water-borne polyurethane (WPU) material together with powdered activated carbon (PAC) and activated sludge as microbial ...

  20. Biofluid process: fluidised-bed gasification of biomass

    Energy Technology Data Exchange (ETDEWEB)

    Dittrich, A. [ATEKO a.s., Hradec Kralove (Czech Republic)

    1996-12-31

    Fluidised-bed gasification of biomass was developed by ATEKO by using long-term experience from coal gasification. An experimental unit was built and a number of tests, first with sawdust gasification, were carried out. A gas combustion engine combined with a power generator was installed and operated in power production. (orig.)

  1. Microwave-assisted synthesis of geopolymers from fluidised bed gasifier bottom ash

    CSIR Research Space (South Africa)

    Oboirien, BO

    2013-09-01

    Full Text Available Fluidised bed gasification (FBG) is a clean coal technology suitable for power and fuel generation from low grade coals. However, the resulting bottom ash presents some disposal challenges to the power plants and the environment. The production...

  2. Emissions modeling of fluidised bed co-combustion of poultry litter and peat

    OpenAIRE

    Henihan, Anne Marie; Leahy, Martin J.; Leahy, J. J.; Cummins, E; B. P. Kelleher

    2003-01-01

    peer-reviewed Gaseous emissions from the fluidised bed co-combustion of 50% w/w chicken litter and peat were monitored and recorded. Emission data were used to create a dispersion model for a proposed site on a poultry farm in Ireland. Variables within the combustion unit influenced both combustion and emission levels of pollutants such as SO2 and NOx, CO. Concentrations of atmospheric pollutants decreased with use of the correct ratio between fluidising and secondary air. Dispersion model...

  3. Fluidisation and dispersion behaviour of small high density pellicular expanded bed adsorbents

    DEFF Research Database (Denmark)

    Theodossiou, Irini; Elsner, H.D.; Thomas, Owen R. T.

    2002-01-01

    The fluidisation and dispersion properties of various agarose-based expanded bed matrices-small high density stainless steel cored prototypes and standard commercial types-were studied in I-cm diameter expanded bed contactors in which fluid entering the column base is locally stirred. In all cases...

  4. SPECIFIC INFLUENCE OF BIOMASS ON THE DESULPHURISATION PROCESS IN COMBUSTION OF BROWN COAL AND BIOMASS MIXTURE IN FLUIDISED BED BOILER

    OpenAIRE

    Kozlova, Svetlana; Ochman, Józef

    2016-01-01

    Thesis is focused on specific aspects of the desulphurisation processes of fluidised- bed boilers. The original goal of the study was to analyse the influence of several kinds of biomass to the quality of the desulphurisation process in combustion of the mixture of brown coal, biomass and limestone in fluidised-bed boilers.

  5. Catalysts for dual fluidised bed biomass gasification - an experimental study at the pilot plant scale

    Energy Technology Data Exchange (ETDEWEB)

    Pfeifer, Christoph; Koppatz, Stefan; Hofbauer, Hermann [Vienna University of Technology, Institute of Chemical Engineering, Vienna (Austria)

    2011-07-15

    Energy from renewable sources is expected to contribute increasingly to the future energy supply. Particularly, the utilisation of biomass via gasification features a high potential for local energy supply. In addition to the conventional heat and power supply, the biomass-derived product gas is utilisable for further conversion, e.g. into liquid fuels, synthetic natural gas or even chemicals. In the field of biomass gasification systems, fluidised bed gasification has achieved notable relevance. Biomass gasification by fluidised bed processing produces high-quality product gas. However, the technical and economical effectiveness is not yet competitive. A major issue is the purity of the product gas, which is mainly focused on the gasification originating tar. A promising option to yield tar-free product gas is the application of a catalyst directly in the fluidised bed process. The present paper outlines catalysts for biomass gasification in fluidised bed processing. Recent activities in the development of gasifier catalysts are highlighted. Different catalysts are described depending on their performance and capability regarding tar conversion. The scope of catalysts ranges from naturally occurring materials to synthetic materials. (orig.)

  6. Occurrence of bromine in fluidised bed combustion of solid recovered fuel

    Energy Technology Data Exchange (ETDEWEB)

    Vainikka, P.

    2011-12-15

    Corrosive ash species are the single most important factor limiting the electric efficiency of steam boiler plants fired with waste or biomass. Chlorine has been found to have a central role in the chemistry involved as it reduces the melting temperature of ash, forms corrosive vapour and gas species in the furnace and halogenated deposits on boiler heat transfer surfaces. In this context chlorine has been extensively researched. At the time of writing this thesis there was hardly any published data available on the occurrence of bromine (Br) in the aforementioned context. The objective of this work was to review the occurrence of bromine in solid fuels and characterise the behaviour of bromine in full-scale fluidised bed combustion. The review on the occurrence of bromine in solid fuels revealed that in anthropogenic wastes bromine is mainly found in connection to flame retarded substances. Several weight percentages of bromine can be found in plastics treated with brominated flame retardants (BFRs). Bromine is typically found some 100-200 mg kg-1 in mixed municipal solid wastes (MSW). Bromine may be enriched in fuels with high share of plastics, such as solid recovered fuel (SRF) or refuse derived fuel (RDF). Up to 2000 mg kg-1 was found as a monthly average in SRF, typical levels being 20-200 mg kg-1. Wastewater sludge from paper mills may contain bromine 20-100 mg kg-1 due the use of bromine based biocides. In other fuels bromine may be found in significant amounts in marine influenced coal deposits and peat as well as in biomass treated with brominated pesticides. In the experimental part SRF, spruce bark and wastewater sludge from a paper mill were co-fired in a full- scale bubbling fluidised bed (BFB) boiler, and the collected fuels, aerosols and waterwall deposits were analysed with the focus on the fate of bromine. Bromine was mainly found to form water soluble high vapour pressure alkali metal halides in the furnace - in the form of KBr(g) and NaBr(g) as

  7. Bed-To-Wall Heat Transfer in a Supercritical Circulating Fluidised Bed Boiler

    Directory of Open Access Journals (Sweden)

    Błaszczuk Artur

    2014-06-01

    Full Text Available The purpose of this work is to find a correlation for heat transfer to walls in a 1296 t/h supercritical circulating fluidised bed (CFB boiler. The effect of bed-to-wall heat transfer coefficient in a long active heat transfer surface was discussed, excluding the radiation component. Experiments for four different unit loads (i.e. 100% MCR, 80% MCR, 60% MCR and 40% MCR were conducted at a constant excess air ratio and high level of bed pressure (ca. 6 kPa in each test run. The empirical correlation of the heat transfer coefficient in a large-scale CFB boiler was mainly determined by two key operating parameters, suspension density and bed temperature. Furthermore, data processing was used in order to develop empirical correlation ranges between 3.05 to 5.35 m·s-1 for gas superficial velocity, 0.25 to 0.51 for the ratio of the secondary to the primary air, 1028 to 1137K for bed temperature inside the furnace chamber of a commercial CFB boiler, and 1.20 to 553 kg·m-3 for suspension density. The suspension density was specified on the base of pressure measurements inside the boiler’s combustion chamber using pressure sensors. Pressure measurements were collected at the measuring ports situated on the front wall of the combustion chamber. The obtained correlation of the heat transfer coefficient is in agreement with the data obtained from typical industrial CFB boilers.

  8. Experimental and predicted approaches for biomass gasification with enriched air-steam in a fluidised bed.

    Science.gov (United States)

    Fu, Qirang; Huang, Yaji; Niu, Miaomiao; Yang, Gaoqiang; Shao, Zhiwei

    2014-10-01

    Thermo-chemical gasification of sawdust refuse-derived fuel was performed on a bench-scale fluidised bed gasifier with enriched air and steam as fluidising and oxidising agents. Dolomite as a natural mineral catalyst was used as bed material to reform tars and hydrocarbons. A series of experiments were carried out under typical operating conditions for gasification, as reported in the article. A modified equilibrium model, based on equilibrium constants, was developed to predict the gasification process. The sensitivity analysis of operating parameters, such as the fluidisation velocity, oxygen percentage of the enriched air and steam to biomass ratios on the produced gas composition, lower heating value, carbon conversion and cold gas efficiency was investigated. The results showed that the predicted syngas composition was in better agreement with the experimental data compared with the original equilibrium model. The higher fluidisation velocity enhanced gas-solid mixing, heat and mass transfers, and carbon fines elutriation, simultaneously. With the increase of oxygen percentage from 21% to 45%, the lower heating value of syngas increased from 5.52 MJ m(-3) to 7.75 MJ m(-3) and cold gas efficiency from 49.09% to 61.39%. The introduction of steam improved gas quality, but a higher steam to biomass ratio could decrease carbon conversion and gasification efficiency owing to a low steam temperature. The optimal value of steam to biomass ratio in this work was 1.0. © The Author(s) 2014.

  9. CFD-DEM Analysis of Particle Attrition in a Jet in a Fluidised Bed

    Science.gov (United States)

    Fulchini, F.; Nan, W.; Ghadiri, M.; Yazdan Panah, M.; Bertholin, S.; Amblard, B.; Cloupet, A.; Gauthier, T.

    2017-06-01

    In fluidised bed processes, the solids are in vigorous motion and thus inevitably subjected to mechanical stresses due to inter-particle and particle-wall impacts. These stresses lead to a gradual degradation of the particles by surface wear, abrasion and body fragmentation commonly termed attrition. One significant contribution of attrition comes from the air jets of the fluidised bed distributor. Particles are entrained into the air jet, where they get accelerated and impacted onto the fluidised bed particles. The jet induced attrition only affects the part of the bed which is limited by the jet length, where the mode of attrition is largely collisional. The overall jet attrition rate is therefore the result of the combination of the single particle damage and the flux of particles entering into that region. The attrition behaviour of particles in the jet region is analysed by evaluating their propensity of breakage experimentally and by simulating an air-jet in a bed of particles by CFD-DEM. The frequency of collisions and impact velocities are estimated from which the attrition due to a single air-jet is predicted.

  10. Validation of the flux number as scaling parameter for top-spray fluidised bed systems

    DEFF Research Database (Denmark)

    Hede, Peter Dybdahl; Bach, P.; Jensen, Anker Degn

    2008-01-01

    . Coating conditions with flux number values of 4.5 and 4.7 were however successful in terms of agglomeration tendency and match of particle size fractions, but indicated in addition a strong influence of nozzle pressure. The present paper suggests even narrower boundaries for the flux number compared......Top-spray fluidised bed coating scale-up experiments have been performed in three scales in order to test and validate the Akkermans flux number as possible scale-up parameter. Coating operations were performed on low porosity sodium sulphate cores (180-350 mu m) coated with aqueous solutions of Na......2SO4 using Dextrin as binder in three top-spray fluidised bed scales, i.e. a small-scale (type: GEA Aeromatic-Fielder Strea-1), medium-scale (type: Niro MP-1) and large-scale (type: GEA MP-2/3). Following the parameter guidelines adapted from the original patent description, the flux number...

  11. Gasification of Biomass with CO2 and H2O Mixtures in a Catalytic Fluidised Bed.

    Czech Academy of Sciences Publication Activity Database

    Jeremiáš, Michal; Pohořelý, Michael; Svoboda, Karel; Manovic, V.; Anthony, E.J.; Skoblia, S.; Beňo, Z.; Šyc, Michal

    2017-01-01

    Roč. 210, DEC 15 (2017), s. 605-610 ISSN 0016-2361 R&D Projects: GA ČR GC14-09692J Grant - others:NSC(TW) 103-2923-E-042A-001-MY3 Institutional support: RVO:67985858 Keywords : fluidised bed * gasification * catalyst Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 4.601, year: 2016

  12. Coal. Fluidized bed, a world record; Charbon. Lit fluidise: record mondial

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-12-31

    In April 1996, the `Societe Provencale du Lit Fluidise`, a subsidiary of Electricite de France (EDF) has put into service in Gardanne, the most powerful circulating fluidized bed boiler in the world, producing 600 MWt; it was constructed by GEC Alsthom Stein Industrie, and will strongly reduce the SO{sub 2} emissions from the coal power plant of Gardanne, which use a highly sulfurous coal. New regulations concerning the French coal industry are also introduced

  13. Potassium behaviour during combustion of wood in circulating fluidised bed power plants

    OpenAIRE

    Valmari, Tuomas

    2000-01-01

    The behaviour of alkali metals, especially of potassium, during circulating fluidised bed combustion of wood-based fuels was studied experimentally in pilot-scale and industrial scale combustors. The fuels included willow, forest residue and waste wood co-combusted with paper mill sludge. As a result of this work, the main chemical and physical transformation mechanisms of potassium compounds in the combustion chamber and in the convective pass are presented in this thesis. Aerosol measur...

  14. Emissions modeling of fluidised bed co-combustion of poultry litter and peat

    Energy Technology Data Exchange (ETDEWEB)

    Henihan, A.M.; Leahy, J.J.; Kelleher, B.P. [University of Limerick (Ireland). Dept. of Chemical and Environmental Science; Leahy, M.J. [University of Limerick (Ireland). Dept. of Physics; Cummins, E. [University College, Dublin (Ireland). Dept. of Agricultural and Food Engineering

    2003-05-01

    Gaseous emissions from the fluidised bed co-combustion of 50% w/w chicken litter and peat were monitored and recorded. Emission data were used to create a dispersion model for a proposed site on a poultry farm in Ireland. Variables within the combustion unit influenced both combustion and emission levels of pollutants such as SO{sub 2} and NO{sub x}, CO. Concentrations of atmospheric pollutants decreased with use of the correct ratio between fluidising and secondary air. Dispersion modelling of combustion at a proposed poultry unit predicted that ground level concentrations for the set of emissions data would be below the limits and guidelines set by air quality standards. (author)

  15. Temperature control of electronic components using fluidised beds

    Science.gov (United States)

    Bean, R.

    1981-06-01

    This paper introduces the concept of fluidized bed cooling applied to electronic systems. It is shown that, when fluidized with air, the cooling efficiency and the pumping power are principally dependent on particle characteristics; in particular the mean diameter should not be less than 100 microns. Design rules are developed and applied to two types of fluid-bed systems: (1) a small bed of alumina particles cooling single devices of 40 W power dissipation where the fluidizing air is the main heat transporting medium, and (2) a large bed of cenospheres with a simple integrated heat exchanger to extract more than 1 KW of heat from complete sub-rack assemblies of up to 40 printed circuit boards, for a fluidizing power of about 3 W. The effect of board spacing on the overall thermal performance is considered, and a minimum spacing of 10-20 mm is shown to be required to maintain cooling efficiency.

  16. The generation and disposal of solid wastes from circulating fluidised bed combustion plant

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, P.; Tomlinson, P. (Ove Arup Partners, London (United Kingdom). Arup Environmental)

    1993-01-01

    This paper describes the environmental issues arising from proposals by British Coal and East Midlands Electricity to construct a circulating fluidised bed combustion (CFBC) Power Station and an associated waste disposal facility at Bilsthorpe in the East Midlands of England. CFBC ash is novel to the UK and the problems of co-disposal of ash and colliery spoil from the power station and adjacent deep coal mine at a surface disposal site are highlighted. The chemical and physical properties of the wastes, research on the revegetation of the ash/spoil mound and the design philosophy developed for the disposal site are reported. 3 refs., 2 figs., 7 tabs.

  17. Gasification of biomass and coal in a pressurised fluidised bed gasifier

    Energy Technology Data Exchange (ETDEWEB)

    Andries, J.; Jong, W. de; Hein, K.R.G. [Technische Univ. Delft (Netherlands)

    1998-09-01

    During a 3 year (1996-1998) multinational JOULE project, partly funded by the EU, experimental and theoretical research is being done on co-gasification of biomass (pelletised straw and Miscanthus) and coal in a pressurised fluidised bed reactor. The influence of feedstock and operating conditions on gasification characteristics has been studied using a 1.5 MW{sub th} gasifier, which has been operated at a pressure of 5 bar and temperatures up to 900 C. The project and the test rig are described and results obtained in the first part of the project are presented and analysed. (orig.)

  18. Stabilization of ash from combustion of MSW in a fluidised bed boiler

    Energy Technology Data Exchange (ETDEWEB)

    Steenari, Britt-Marie; Wilewska, Magda [Chalmers Univ. of Technology, Goeteborg (Sweden). Dept. of Environmental Inorganic Chemistry

    2004-06-01

    Due to restrictions against the land filling of combustible waste and directives from authorities that favour energy recovery from the waste, combustion of household waste is becoming more common. Even though combustion of MSW reduces the volume of waste to be handled by approximately 90%, it produces ash residues containing most of the metals present in the original fuel and a number of other species carried through the boiler or formed during combustion. The residues can be divided into three categories: 1. Stable, inert ash that can be utilised in, for example, construction applications 2. Ash that is stable enough to be land filled as nonhazardous waste 3. Ash that contains large amounts of soluble components and potentially toxic metal species. The regulations considering leaching of ash components set limits for the release of soluble salts and toxic metals. Some fly ashes show low leachability for metals but gives a salt release that is too close to the limit for total dissolved solids. Since fly ash from FBC boilers represent the largest volume of ash from these boilers there is a need for a simple and cheap treatment method that reduces the amount of soluble salts, i.e. NaCl, KCl etc, in the ash. After stabilisation, the ash is supposed to go into a more stable category. The aim of this project has been to investigate the applicability of a method to wash such an ash with water. The work included laboratory studies of the ash properties, the water washing process, filtration properties of the ash slurry and also tests of the method in pilot scale at a full scale boiler. This work has been concentrated towards the investigation of cyclone ash from a bubbling fluidised bed boiler in Lidkoeping fired with 100% household waste. Elemental composition of ash samples before and after washing/filtration was determined by AAS or ICP after a suitable dissolution of the sample. The mineralogy of ash samples was analysed using X-ray powder diffractometry. This method

  19. Energy recovery from sewage sludge by means of fluidised bed gasification.

    Science.gov (United States)

    Gross, Bodo; Eder, Christian; Grziwa, Peter; Horst, Juri; Kimmerle, Klaus

    2008-01-01

    Because of its potential harmful impact on the environment, disposal of sewage sludge is becoming a major problem all over the world. Today the available disposal measures are at the crossroads. One alternative would be to continue its usage as fertiliser or to abandon it. Due to the discussions about soil contamination caused by sewage sludge, some countries have already prohibited its application in agriculture. In these countries, thermal treatment is now presenting the most common alternative. This report describes two suitable methods to directly convert sewage sludge into useful energy on-site at the wastewater treatment plant. Both processes consist mainly of four devices: dewatering and drying of the sewage sludge, gasification by means of fluidised bed technology (followed by a gas cleaning step) and production of useful energy via CHP units as the final step. The process described first (ETVS-Process) is using a high pressure technique for the initial dewatering and a fluidised bed technology utilising waste heat from the overall process for drying. In the second process (NTVS-Process) in addition to the waste heat, solar radiation is utilised. The subsequent measures--gasification, gas cleaning and electric and thermal power generation--are identical in both processes. The ETVS-Process and the NTVS-Process are self-sustaining in terms of energy use; actually a surplus of heat and electricity is generated in both processes.

  20. Recommendations for conversions of grate fired boilers to fluidising beds; Anvisningar foer konvertering av rosterpannor till fluidiserad baeddteknik

    Energy Technology Data Exchange (ETDEWEB)

    Eriksson, Lars; Ingman, Rolf [AaF Energikonsult AB, Stockholm (Sweden)

    2001-03-01

    This report gives advice and recommendations for retrofitting of grate fired boilers to fluidising beds. Nine plants have been visited and experiences from these conversion projects have been gathered and analysed. Among the important points planning, fuel specification, heat balance calculations and clarifying of delivery limits can be mentioned. It is also important not to underestimate the need for education of the operational staff.

  1. Heat transfer analysis of laboratory scale fast pyrolysis fluidised bed reactor

    Science.gov (United States)

    Jourabchi, Seyed Amirmostafa; Gan, Suyin; Ng, Hoon Kiat

    2017-04-01

    Heat transfer analysis of a fluidised bed with a bore diameter of 2.5 cm and a vertical length of 50 cm was investigated by using computational fluid dynamics (CFD) on FLUENT 15.0 educational version software. The Eulerian-Eulerian two-fluid granular model was used as the multiphase flow model to perform this simulation. A 2-D axisymmetric model was considered by using glass and stainless steel beads of 0.5 mm and 1.0 mm in diameters as the heat transfer medium to biomass. The Gidaspow model was used for the drag equation and the Gunn model was used in the interphase heat transfer coefficient determination. Heat transfer coefficient (HTC) of stainless steel beads shows to be approximately 3 times higher than that of the glass beads of the same size based on having higher thermal conductivity. At wall temperature of 500 K, stainless steel and glass beads can be fluidised by using nitrogen linear velocity of 0.7 and 0.3 m/s respectively. Under these optimum conditions, HTC reaches up to 7625 W/(m2.K) and 2900 W/(m2.K) for stainless steel and glass beads and their surface temperatures can reach up to 495 K and 480 K, respectively.

  2. A new process control strategy for aqueous film coating of pellets in fluidised bed

    DEFF Research Database (Denmark)

    Larsen, C.C.; Sonnergaard, Jørn; Bertelsen, Pernille Scholdan

    2003-01-01

    The parameters with effect on maximum spray rate and maximum relative outlet air humidity when coating pellets in a fluidised bed were investigated. The tested variables include type of water based modified release film coating (Eudragit® NE 30D, Eudragit® RS 30D, Aquacoat ECD®) coating principle...... to be the controlling factor. The type of pellets affected the maximum spray rate. A thermodynamic model for the coating process is employed throughout the process and not just during steady state. The thermodynamic model is incorporated into a new process control strategy. The process control strategy is based on in......-process calculation of degree of utilisation of the potential evaporation energy (DUE) of the outlet air and the relative outlet air humidity (RH). The spray rate is maximised using set points of DUE and RH as control parameters. The product temperature is controlled simultaneously by regulating the inlet air...

  3. Hydrodynamic study of the turbulent fluidized beds; Etude hydrodynamique des lits fluidises turbulents

    Energy Technology Data Exchange (ETDEWEB)

    Taxil, I.

    1996-12-20

    Gas-solid turbulent fluidization has already been widely studied in the literature. However, its definition and specificities remain controversial and confused. Most of the studies focussed on the turbulent transition velocities are based on wall pressure drop fluctuations studies. In this work, we first characterize the turbulent regime with the classical study of pressure drop signals with standard deviation analysis, completed with a more specific frequency analysis and also by a stochastic analysis. Then, we evaluate bubble flow properties. Experimental results have been obtained in a 0.2 m I.D. fluidized bed expanding to 0.4 m I.D. in the freeboard in order to limit entrainment at high fluidization velocities. The so lid used was FCC catalyst. It was fluidized by air at ambient conditions. The superficial fluidization velocity ranged 0.2 to 2 m/s. Fast response transducers recorded pressure drop at the wall and bubble flow properties (bubble size, bubble velocity and bubble frequency) could be deduced from a light reflected signal at various bed locations with optical fibers. It has been shown the turbulent regime is delimited by two velocities: Uc (onset of turbulent regime) and Utr (onset of transport regime), which can be determined based on standard deviations, dominant frequencies and width of wave land of pressure signals. The stochastic analysis confirms that the signal enriches in frequencies in the turbulent regime. Bubble size and bubble velocity could be correlated to the main superficial gas velocity. The main change in bubble flow in the turbulent regime was shown to be the stagnation of the bubble frequency at its maximum value. It was also shown that the bubble flow properties in the turbulent regime imply a strong aeration of the emulsion phase. (authors) 76 refs.

  4. Steam gasification of various feedstocks at a dual fluidised bed gasifier: Impacts of operation conditions and bed materials

    Energy Technology Data Exchange (ETDEWEB)

    Pfeifer, Christoph; Koppatz, Stefan; Hofbauer, Hermann [Vienna University of Technology, Institute of Chemical Engineering, Vienna (Austria)

    2011-03-15

    Gasification of biomass is an attractive technology for combined heat and power production as well as for synthesis processes such as production of liquid and gaseous biofuels. Dual fluidised bed (DFB) technology offers the advantage of a nearly nitrogen-free product gas mainly consisting of H{sub 2}, CO, CO{sub 2} and CH{sub 4}. The DFB steam gasification process has been developed at Vienna University of Technology over the last 15 years using cold flow models, laboratory units, mathematical modelling and simulation. The main findings of the experimental work at a 100-kW pilot scale unit are presented. Different fuels (wood pellets, wood chips, lignite, coal, etc.) and different bed materials (natural minerals such as olivine, limestones, calcites, etc. as well as modified olivines) have been tested and the influence on tar content as well as gas composition was measured and compared among the different components. Moreover, the influence of operating parameters such as fuel moisture content, steam/fuel ratio and gasification temperature on the product gas has been investigated. DFB steam gasification of solid biomass coupled with CO{sub 2} capture, the so-called absorption enhanced reforming (AER) process, is highlighted. The experiments in pilot scale led to commercial realisation of this technology in demonstration scale. Summarising, the DFB system offers excellent fuel flexibility to be used in advanced power cycles as well as in polygeneration applications. (orig.)

  5. Bubble size reduction in a fluidized bed by electric fields

    NARCIS (Netherlands)

    Kleijn van Willigen, F.; Van Turnhout, J.; Van Ommen, J.R.; Van den Bleek, C.

    2003-01-01

    The reduction of the size of bubbles can improve both selectivity and conversion in gas-solid fluidized beds. Results are reported of the reduction of bubble size by the application of electric fields to uncharged, polarizable particles in fluidized beds. It is shown how average bubble diameters can

  6. Co-gasification of meat and bone meal with coal in a fluidised bed reactor

    Energy Technology Data Exchange (ETDEWEB)

    E. Cascarosa; L. Gasco; G. Gea; J.L. Sanchez; J. Arauzo [Universidad de Zaragoza (Spain). Thermochemical Processes Group

    2011-08-15

    After the Bovine Spongiform Encephalopathy illness appeared, the meat and bone meat (MBM) produced from animal residues became an important waste. In spite of being a possible fuel due to its heating value (around 21.4 MJ/kg), an important fraction of the meat and bone meal is being sent to landfills. The aim of this work is to evaluate the co-gasification of low percentages of meat and bone meal with coal in a fluidised bed reactor as a potential waste management alternative. The effect of the bed temperature (800-900{sup o}C), the equivalence ratio (0.25-0.35) and the percentage of MBM in the solid fed (0-1 wt.%) on the co-gasification product yields and properties is evaluated. The results show the addition of 1 wt.% of MBM in a coal gasification process increases the gas and the liquid yield and decreases the solid yield at 900{sup o}C and 0.35 of temperature and equivalence ratio operational conditions. At operational conditions of 900{sup o}C and equivalence ratio of 0.35, the specific yield to gas (y{sub gas}) increases from 3.18 m{sup 3}(STP)/kg to 4.47 m{sup 3}(STP)/kg. The gas energy yield decreased 24.1% and the lower heating value of the gas decreases from 3.36 MJ/m{sup 3}(STP) to 2.16 MJ/m{sup 3}(STP). The concentration of the main gas components (H{sub 2}, CO and CO{sub 2}) hardly varies with the addition of MBM, however the light hydrocarbon concentrations decrease and the H{sub 2}S concentration increases at the higher temperature (900{sup o}C). 32 refs., 9 figs., 7 tabs.

  7. Behaviour of meat and bonemeal/peat pellets in a bench scale fluidised bed combustor

    Energy Technology Data Exchange (ETDEWEB)

    McDonnell, K.; Desmond, J.; Leahy, J.J.; Howard-Hildige, R.; Ward, S. [University College Dublin, Dublin (Ireland). Agriculture and Food Engineering Department

    2001-01-01

    As a result of the recent Bovine Spongiform Encephalopathy crisis in the European beef industry, safe animal by-product disposal is currently being addressed. One such disposal option is the combustion of by-product material such as meat and bone meal (MBM) in a fluidised bed combustor (FBC) for the purpose of energy recovery. Two short series of combustion tests were conducted on a FBC at the University of Twente, the Netherlands. In the first series, pellets (10 mm in diameter and approximately 10 mm in length) were made from a mixture of MBM and milled peat, at MBM inclusion rates of 0%, 30%, 50%, 70% and 100%. In the second series of tests, the pellets were commercially made and were 4.8 mm in diameter and between 12 and 15 mm long. These pellets had a weight of about 0.3 g and contained 0%, 25%, 35%, 50% and 100% MBM inclusion with the peat. Both sets of pellets were combusted at 800{degree}C. The residence times in the FBC varied from 300 s (25% MBM inclusion) to 120 s (100% MBM inclusion) for the first series of pellets. Increasing compaction pressure increased the residence time. For the second series of pellets, the residence time varied from about 300 s (25% MBM inclusion) to 100 s (100% MBM inclusion). MBM was found to be a volatile product (about 65%) and co-firing it with milled peat in a pelleted feed format reduces its volatile intensity. Pellets made from 100% bone based meal remained intact within the bed and are thought to have undergone a process of calcination during combustion. A maximum MBM inclusion rate of 35% with milled peat in a pellet is recommended.

  8. Eulerian simulations of bubble behaviour in a two-dimensional gas-solid bubbling fluidized bed

    Energy Technology Data Exchange (ETDEWEB)

    Lu Huilin; Liu Wentie; Zhao Guangbo; He Yurong [Harbin Institute of Technology (China). Dept. of Power Engineering; Li Feng [Jiangxi Boiler Co. Ltd., Nanchang (China)

    2002-07-01

    In the present study, the CFD model is based on a two-fluid model extended with the kinetic theory of granular flow. The simulation results of bubble diameter and bubble rise velocity are compared to the Darton equation and the Davidson model in a free bubbling fluidized bed. The predicted values are in reasonable agreement with the values from the Darton bubble size equation and the Davidson model for isolated bubbles. It is shown that the break-up and direct wall interaction effects influence the dynamic bubble behavior in the free bubbling fluidized beds. (author)

  9. Liquid transportation fuels via large-scale fluidised-bed gasification of lignocellulosic biomass

    Energy Technology Data Exchange (ETDEWEB)

    Hannula, I.; Kurkela, E.

    2013-04-15

    With the objective of gaining a better understanding of the system design trade-offs and economics that pertain to biomass-to-liquids processes, 20 individual BTL plant designs were evaluated based on their technical and economic performance. The investigation was focused on gasification-based processes that enable the conversion of biomass to methanol, dimethyl ether, Fischer-Tropsch liquids or synthetic gasoline at a large (300 MWth of biomass) scale. The biomass conversion technology was based on pressurised steam/O2-blown fluidised-bed gasification, followed by hot-gas filtration and catalytic conversion of hydrocarbons and tars. This technology has seen extensive development and demonstration activities in Finland during the recent years and newly generated experimental data has also been used in our simulation models. Our study included conceptual design issues, process descriptions, mass and energy balances and production cost estimates. Several studies exist that discuss the overall efficiency and economics of biomass conversion to transportation liquids, but very few studies have presented a detailed comparison between various syntheses using consistent process designs and uniform cost database. In addition, no studies exist that examine and compare BTL plant designs using the same front-end configuration as described in this work. Our analysis shows that it is possible to produce sustainable low-carbon fuels from lignocellulosic biomass with first-law efficiency in the range of 49.6-66.7% depending on the end-product and process conditions. Production cost estimates were calculated assuming Nth plant economics and without public investment support, CO2 credits or tax assumptions. They are 58-65 euro/MWh for methanol, 58-66 euro/MWh for DME, 64-75 euro/MWh for Fischer-Tropsch liquids and 68-78 euro/MWh for synthetic gasoline. (orig.)

  10. Pressurised fluidised bed combustion: an alternative for the clean use of coal. La combustion en lecho fluido a presion, una alternativa de uso limpio del carbon en desarrollo

    Energy Technology Data Exchange (ETDEWEB)

    Beucom O Perez-Zamora, V.; Menendez Perez, J.A.E. (ENDESA, Madrid (Spain))

    1988-11-01

    Atmospheric fluidised bed combustion is an alternative worthy of consideration. It is a solution which maintains or even increases output slightly and, in the circulating fluidised bed variety, has the advantage of being able to burn an inconsistent quality of coal with a high sulphur content. The most important question is to what output this method can be developed whilst remaining competitive with other systems. There is a tendency to assume that atmospheric fluidised bed combustors can be developed up to 250 MW and that more powerful installations for electricity generation use systems with a higher output. In any case, this is no more than a general and preliminary observation. Its validity will be proved by the technical and economic results achieved with high output systems and by the availability of coal of the required mix of quality and price. 10 tabs., 10 figs.

  11. Utilisation of ash from the co-combustion of CandD wood with biofuels. A series of experiments with a 24 MW{sub th} bubbling fluidised bed; Askanvaendning vid samfoerbraenning av RT-flis med olika biobraenslen. Foersoeksprogram i en 24 MW{sub th} bubblande baedd

    Energy Technology Data Exchange (ETDEWEB)

    Bjurstroem, Henrik; Wikman, Karin [AaF-Process AB, Stockholm (Sweden)

    2005-10-01

    fluidised bed has a memory effect. The 'eco-ash' is coarser than the filter ash and has not been studied in detail. It should be able to complement the particle size distribution of filter ash in its uses. The content of environmentally disruptive elements in the waste wood is so much larger than that in logging residues that, in practice, they may not be co-combusted if one wish to obtain an ash that is may be recycled to forestland. When firing waste wood and logging residues alternatively, the transition from waste wood ash to logging residue ash is slow: given the experimental conditions, it requires more than the 11 days that we had at our disposal. The transition time depends largely on the rate of turnover of the bed.

  12. Results concerning a clean co-combustion technology of waste biomass with fossil fuel, in a pilot fluidised bed combustion facility

    Energy Technology Data Exchange (ETDEWEB)

    Ionel, Ioana; Trif-Tordai, Gavril; Ungureanu, Corneliu; Popescu, Francisc; Lontis, Nicolae [Politehnica Univ. Timisoara (Romania). Faculty for Mechanical Engineering

    2008-07-01

    The research focuses on a facility, the experimental results, interpretation and future plans concerning a new developed technology of using waste renewable energy by applying the cocombustion of waste biomass with coal, in a fluidised bed system. The experimental facility is working entirely in accordance to the allowed limits for the exhaust flue gas concentration, with special concern for typical pollutants. The experiments conclude that the technology is cleaner, has as main advantage the possibility to reduce both the SO{sub 2} and CO{sub 2} exhaust in comparison to standard fossil fuel combustion, under comparable circumstances. The combustion is occurring in a stable fluidised bed. (orig.)

  13. Gaseous emissions in pressurised fluidised-bed combustion. Analysis and summary of the pilot experiments; Kaasumaiset paeaestoet paineistetussa leijukerrospoltossa. Koetulosten kaesittely ja yhteenveto

    Energy Technology Data Exchange (ETDEWEB)

    Korpela, T.; Hippinen, I.; Konkola, M. [Helsinki Univ. of Technology, Espoo (Finland)

    1996-12-01

    The influence of operating conditions on gaseous emissions in pressurised fluidised-bed combustion have been studied. The research objectives have been behaviour of sulphur absorbents and reduction of sulphur dioxide emissions, reduction of nitrogen oxide emissions, release of vapour-phase alkalimetals and carbon monoxide emissions. The sulphur capture capacities of calcium-based sorbents under PFBC conditions have been studied at a pressurised fluidised-bed reactor and at a pressurised thermogravimetric apparatus. The project has also connected results of the experimental PFBC at HUT/EVO. (author)

  14. Treatment of a highly-concentrated sulphate-rich synthetic wastewater using calcium hydroxide in a fluidised bed crystallizer.

    Science.gov (United States)

    Maharaj, Chiara; Chivavava, Jemitias; Lewis, Alison

    2018-02-01

    This study aimed to investigate factors that affect the conversion of sulphates and magnesium, and the recovery of gypsum and magnesium hydroxide in the neutralization of a sulphate rich stream using calcium hydroxide, in a laboratory scale seeded fluidised bed crystallizer. Particular focus was on reducing the precipitated fines that escaped with the treated water, through the use of seeds, while removing as much sulphate-compounds from the waste stream as possible. The composition of the total sulphate salts was as follows: 80% magnesium sulphate, calcium sulphate remaining at its saturation concentration (1.5 g/L), with the remainder being sodium sulphate based on typical reverse osmosis retentate concentrations ranging from 1.5 - 120 g/L of total sulphate salts. The fluidised bed crystallizer, using silica seeds, was found to be effective at reducing the formation of gypsum and magnesium hydroxide fines by almost half. Feed concentrations of 35 g/L of total salts yielded better sulphate conversions (±75%), compared to a feed concentration of 8 g/L (±30%). It was possible to remove 99% of the magnesium in the saline wastewater stream using a calcium to sulphate ratio of 1:1 for feed concentrations of 15 g/L and higher. Excess calcium hydroxide suspension improved sulphate conversions. Copyright © 2017 Elsevier Ltd. All rights reserved.

  15. Co-firing coal and biomass in a fluidised bed boiler

    CSIR Research Space (South Africa)

    North, BC

    2005-11-01

    Full Text Available combustion occurs in the bed, and how much drying occurs in the bed. This has a direct impact on the design of the bed because, if the actual heat balance over the bed showed that there was excess heat, then in-bed heat transfer surfaces may have needed... to be installed. If, however, there was insufficient heat, then in-bed heat transfer cannot be included and, in fact, some method must be found to reduce heat losses from the bed, for example pre-drying of the sludge. For these trials a 0.25 m2 test facility...

  16. A comparison of circulating fluidised bed combustion and gasification power plant technologies for processing mixtures of coal, biomass and plastic waste

    Energy Technology Data Exchange (ETDEWEB)

    McIlveen-Wright, D.R.; Huang, Y.; McMullan, J.T. [NICERT, University of Ulster at Jordanstown, Newtownabbey BT37 0QB, Northern Ireland (United Kingdom); Pinto, F.; Franco, C.; Gulyurtlu, I. [INETI-DEECA, Estrada do Paco do Lumiar, 22, 1649-038 Lisboa (Portugal); Armesto, L.; Cabanillas, A. [CIEMAT, Avda Complutense, 22, 28040 Madrid (Spain); Caballero, M.A.; Aznar, M.P. [Chemical and Environmental Engineering Department, Centro Politecnico Superior, Maria de Luna, University of Saragossa, 50018 Saragossa (Spain)

    2006-09-15

    Environmental regulations concerning emission limitations from the use of fossil fuels in large combustion plants have stimulated interest in biomass for electricity generation. The main objective of the present study was to examine the technical and economic viability of using combustion and gasification of coal mixed with biomass and plastic wastes, with the aim of developing an environmentally acceptable process to decrease their amounts in the waste stream through energy recovery. Mixtures of a high ash coal with biomass and/or plastic using fluidised bed technologies (combustion and gasification) were considered. Experiments were carried out in laboratory and pilot plant fluidised bed systems on the combustion and air/catalyst and air/steam gasification of these feedstocks and the data obtained were used in the techno-economic analyses. The experimental results were used in simulations of medium to large-scale circulating fluidised bed (CFB) power generation plants. Techno-economic analysis of the modelled CFB combustion systems showed efficiencies of around 40.5% (and around 46.5% for the modelled CFB gasification systems) when fuelled solely by coal, which were only minimally affected by co-firing with up to 20% biomass and/or wastes. Specific investments were found to be around $2150/kWe to $2400/kWe ($1350/kWe to $1450/kWe) and break-even electricity selling prices to be around $68/MWh to $78/MWh ($49/MWh to $54/MWh). Their emissions were found to be within the emission limit values of the large combustion plant directive. Fluidised bed technologies were found to be very suitable for co-firing coal and biomass and/or plastic waste and to offer good options for the replacement of obsolete or polluting power plants. (author)

  17. Testing of downstream catalysts for tar destruction with a guard bed in a fluidised bed biomass gasifier at pilot plant scale

    Energy Technology Data Exchange (ETDEWEB)

    Aznar, M.P.; Frances, E.; Campos, I.J.; Martin, J.A.; Gil, J. [Saragossa Univ. (Spain). Dept. of Chemistry and Environment Engineering; Corella, J. [Complutense Univ. of Madrid (Spain). Dept. of Chemical Engineering

    1996-12-31

    A new pilot plant for advanced gasification of biomass in a fast fluidised bed is now fully operative at University of Saragossa, Spain. It is a `3rd generation` pilot plant. It has been built up after having used two previous pilot plants for biomass gasification. The main characteristic of this pilot plant is that it has two catalytic reactors connected in series, downstream the biomass gasifier. Such reactors, of 4 cm i.d., are placed in a slip stream in a by-pass from the main gasifier exit gas. The gasification is made at atmospheric pressure, with flow rates of 3-50 kg/in, using steam + O{sub 2} mixtures as the gasifying agent. Several commercial Ni steam-reforming catalyst are being tested under a realistic raw gas composition. Tar eliminations or destructions higher than 99 % are easily achieved. (orig.) 2 refs.

  18. Chemical and ecotoxicological characterization of ashes obtained from sewage sludge combustion in a fluidised-bed reactor

    Energy Technology Data Exchange (ETDEWEB)

    Lapa, N. [Environmental Biotechnology Researching Unit (UBiA), Faculty of Science and Technology (FCT), New University of Lisbon - UNL, Ed. Departamental, piso 3, gabinete 377, Quinta da Torre, 2829-516 Caparica (Portugal)]. E-mail: ncsn@fct.unl.pt; Barbosa, R. [Environmental Biotechnology Researching Unit (UBiA), Faculty of Science and Technology (FCT), New University of Lisbon - UNL, Ed. Departamental, piso 3, gabinete 377, Quinta da Torre, 2829-516 Caparica (Portugal); Lopes, M.H. [National Institute of Engineering, Technology and Innovation (INETI), Department of Energetic Engineering and Environmental Control (DEECA). Edificio J, Estrada do Paco do Lumiar, 22, 1649-038 Lisbon (Portugal); Mendes, B. [Environmental Biotechnology Researching Unit (UBiA), Faculty of Science and Technology (FCT), New University of Lisbon - UNL, Ed. Departamental, piso 3, gabinete 377, Quinta da Torre, 2829-516 Caparica (Portugal); Abelha, P. [National Institute of Engineering, Technology and Innovation (INETI), Department of Energetic Engineering and Environmental Control (DEECA). Edificio J, Estrada do Paco do Lumiar, 22, 1649-038 Lisbon (Portugal); Gulyurtlu, I. [National Institute of Engineering, Technology and Innovation (INETI), Department of Energetic Engineering and Environmental Control (DEECA). Edificio J, Estrada do Paco do Lumiar, 22, 1649-038 Lisbon (Portugal); Santos Oliveira, J. [Environmental Biotechnology Researching Unit (UBiA), Faculty of Science and Technology (FCT), New University of Lisbon - UNL, Ed. Departamental, piso 3, gabinete 377, Quinta da Torre, 2829-516 Caparica (Portugal)

    2007-08-17

    In 1999, the DEECA/INETI and the UBiA/FCT/UNL started a researching project on the partition of heavy metals during the combustion of stabilised sewage sludge (Biogran[reg]), in a fluidised-bed reactor, and on the quality of the bottom ashes and fly ashes produced. This project was entitled Bimetal and was funded by the Portuguese Foundation for Science and Technology. In this paper only the results on the combustion of Biogran[reg]) are reported. The combustion process was performed in two different trials, in which different amounts of sewage sludge and time of combustion were applied. Several ash samples were collected from the bed (bottom ashes) and from two cyclones (first cyclone and second cyclone ashes). Sewage sludge, bed material (sand) and ash samples were submitted to the leaching process defined in the European leaching standard EN 12457-2. The eluates were characterized for a set of inorganic chemical species. The ecotoxicological levels of the eluates were determined for two biological indicators (Vibrio fischeri and Daphnia magna). The results were compared with the limit values of the CEMWE French Regulation. The samples were also ranked according to an index based on the chemical characterization of the eluates. It was observed an increase of the concentration of metals along the combustion system. The ashes trapped in the second cyclone, for both combustion trials, showed the highest concentration of metals in the eluates. Chemically, the ashes of the second cyclone were the most different ones. In the ecotoxicological point of view, the ecotoxicity levels of the eluates of the ashes, for both combustion cycles, did not follow the same pattern as observed for the chemical characterization. The ashes of the first cyclone showed the highest ecotoxicity levels for V. fischeri and D. magna. This difference on chemical and ecotoxicological results proves the need for performing both chemical and ecotoxicological characterizations of the sub

  19. Chemical and ecotoxicological characterization of ashes obtained from sewage sludge combustion in a fluidised-bed reactor.

    Science.gov (United States)

    Lapa, N; Barbosa, R; Lopes, M H; Mendes, B; Abelha, P; Boavida, D; Gulyurtlu, I; Oliveira, J Santos

    2007-08-17

    In 1999, the DEECA/INETI and the UBiA/FCT/UNL started a researching project on the partition of heavy metals during the combustion of stabilised sewage sludge (Biogran), in a fluidised-bed reactor, and on the quality of the bottom ashes and fly ashes produced. This project was entitled Bimetal and was funded by the Portuguese Foundation for Science and Technology. In this paper only the results on the combustion of Biogran are reported. The combustion process was performed in two different trials, in which different amounts of sewage sludge and time of combustion were applied. Several ash samples were collected from the bed (bottom ashes) and from two cyclones (first cyclone and second cyclone ashes). Sewage sludge, bed material (sand) and ash samples were submitted to the leaching process defined in the European leaching standard EN 12457-2. The eluates were characterized for a set of inorganic chemical species. The ecotoxicological levels of the eluates were determined for two biological indicators (Vibrio fischeri and Daphnia magna). The results were compared with the limit values of the CEMWE French Regulation. The samples were also ranked according to an index based on the chemical characterization of the eluates. It was observed an increase of the concentration of metals along the combustion system. The ashes trapped in the second cyclone, for both combustion trials, showed the highest concentration of metals in the eluates. Chemically, the ashes of the second cyclone were the most different ones. In the ecotoxicological point of view, the ecotoxicity levels of the eluates of the ashes, for both combustion cycles, did not follow the same pattern as observed for the chemical characterization. The ashes of the first cyclone showed the highest ecotoxicity levels for V. fischeri and D. magna. This difference on chemical and ecotoxicological results proves the need for performing both chemical and ecotoxicological characterizations of the sub-products of such type

  20. Catalytic reduction of nitrous oxide by hydrocarbons over a Fe-zeolite monolith under fluidised bed combustion conditions

    Energy Technology Data Exchange (ETDEWEB)

    Ruiz-Martinez, E.; Sanchez-Hervas, J.M.; Otero-Ruiz, J. [Departamento de Combustibles Fosiles, Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas (CIEMAT), 28040 Madrid (Spain)

    2004-07-08

    Fluidised bed combustion (FBC) is an important source of nitrous oxide emissions. The catalytic reduction of nitrous oxide with different hydrocarbons was carried out over the catalytic system Fe-ZSM-5 supported on ceramic monoliths, under conditions representative of the off-gases of FBC. The selective catalytic reduction (SCR) of nitrous oxide by propane and propene is activated in the presence of oxygen, whereas its conversion is not affected by the increase of oxygen concentration in the feed gas. The SCR of nitrous oxide by methane is inhibited in the presence of oxygen and the increment of oxygen content in the feed gas leads to a decrease in the catalyst activity and selectivity. Water strongly inhibits the nitrous oxide catalytic reduction independently of the type of hydrocarbon. This effect is more pronounced as water concentration in the process gas increases. Propane resulted to be the most appropriate hydrocarbon of those easily available for the SCR of nitrous oxide over the catalytic system. Methane is little active, whereas propane is slightly more active and selective than propene and results in lower hydrocarbon residual emissions, at oxygen and water levels similar to those found in real combustion off-gases. Furthermore, with respect to methane, propane allows lower reaction temperatures in addition to higher reduction efficiency. Moreover, the emission of unreacted hydrocarbon is higher in the case of methane, whose emission is unwanted, because methane is a greenhouse gas itself.

  1. Flow structure formation and evolution in circulating gas-fluidised beds

    NARCIS (Netherlands)

    Li, J.; Kuipers, J.A.M.

    2004-01-01

    The occurrence of heterogeneous flow structures in gas-particle flows seriously affects the gas-solid contacting and transport processes in high-velocity gas-fluidized beds. Particles do not disperse uniformly in the flow but pass through the bed in a swarm of clusters. The so-called "core-annulus"

  2. Flow pattern formation in high-velocity gas-fluidised beds

    NARCIS (Netherlands)

    Li, J.; Kuipers, J.A.M.; Grace, J.R.; Zhu, J.; De Hugo, L.

    2002-01-01

    The occurrence of heterogeneous flow structures in gas-particle flows seriously affects the gas-solid contacting and transport processes in high-velocity fluidized beds. A computational study, using a discrete particle method based on Molecular Dynamics techniques, has been carried out to explore

  3. Experience gained in pilot-scale and bench-scale fluidised beds processing

    CSIR Research Space (South Africa)

    Hadley, TD

    2006-02-01

    Full Text Available , considerable progress has been made. The earliest developments were in coal combustion. Work has been done on in-bed sulphur capture to reduce the sulphur dioxide off-gas content. Expertise in the design and commissioning of industrial-scale plants has led...

  4. Cofiring of difficult fuels: The effect of Ca-based sorbents on the gas chemistry in fluidised bed combustion; Kalsiumpohjaisten lisaeaineiden vaikutus leijukerrospolton kaasukemiaan vaikeiden polttoaineiden sekapoltossa

    Energy Technology Data Exchange (ETDEWEB)

    Aeijaelae, M.; Partanen, J.; Fabritius, M.; Elo, T.; Virta, A.K. [Imatran Voima Oy, Vantaa (Finland)

    1997-10-01

    The objective of this project is to establish the effects of Ca-based sorbents on sulphur, halogen and alkaline chemistry in fluidised bed combustion of difficult fuels, and to find out any restrictions on the use of these sorbents. The aim is to acquire sufficient knowledge to ensure the operational reliability of power plants and to minimise the emissions and costs of flue gas cleaning. The results enable the owner to anticipate necessary changes associated with slagging, fouling and emission control in the existing power plants, when there are plans to increase the range of fuels used. (orig.)

  5. Pressurised fluidised bed combustion: an alternative clean coal technology. La combustion en lecho fluido a presion, una alternativa de uso limpio del carbon en desarollo

    Energy Technology Data Exchange (ETDEWEB)

    Bencomo Perez-Zamora, V.; Menendez Perez, J.A.E. (ENDESA, Madrid (Spain))

    1988-11-01

    The primary aim of thistechnology is to reduce emissions of sulphur and nitrous oxides. Pilot plant tests have achieved a sulphur fixing rate of over 95%. Pressurised fluidised bed combustion also has advantages with regard to the emission of contaminants. Halogens, fluorine and chlorine, which in conventional combustion methods are released in the gases, to a large degree remain in the ash as do trace elements, such as arsenic, which usually vapourise at high temperatures in pulverised coal combustors. This technology also has a high output of between 38 and 40% net according to the type of coal used. 10 figs., 10 tabs.

  6. CO-COMBUSTION OF REFUSE DERIVED FUEL WITH COAL IN A FLUIDISED BED COMBUSTOR

    Directory of Open Access Journals (Sweden)

    W. A. WAN AB KARIM GHANI

    2009-03-01

    Full Text Available Power generation from biomass is an attractive technology which utilizes municipal solid waste-based refused derived fuel. In order to explain the behavior of biomass-fired fluidized bed incinerator, biomass sources from refuse derived fuel was co-fired with coal in a 0.15 m diameter and 2.3 m high fluidized bed combustor. The combustion efficiency and carbon monoxide emissions were studied and compared with those from pure coal combustion. This study proved that the blending effect had increased the carbon combustion efficiency up to 12% as compared to single MSW-based RDF. Carbon monoxide levels fluctuated between 200-1600 ppm were observed when coal is added. It is evident from this research that efficient co-firing of biomass with coal can be achieved with minimum modification of existing coal-fired boilers.

  7. Feasibility study - Lowered bed temperature in Fluidised Bed boilers for waste; Foerstudie - Saenkt baeddtemperatur i FB-pannor foer avfallsfoerbraenning

    Energy Technology Data Exchange (ETDEWEB)

    Niklasson, Fredrik

    2009-01-15

    Waste incineration generally serves two purposes; 1) dispose of waste and 2) generation of heat and power. In the process of power production from waste fuels, the steam temperatures in super heaters are generally limited by the severe fouling and corrosion that occurs at elevated material temperatures, caused by high concentrations of alkali metals and chloride in the flue gas and fly ash. The overall aim of a continuation of present project is to determine if a reduced temperature of the bed zone in a fluidized bed waste incinerator reduces the amount of alkali chlorides in the flue gas. If so, a reduced bed temperature might enable increased steam temperature in super heaters, or, at unchanged steam temperature, improve the lifespan of the super heaters. The results from the project are of interest for plant owners wishing to improve performance of existing plants. The results may also be used to modify the design of future plants by boiler manufacturers. The aim of present pre-study was to determine how far the bed temperature can be reduced in a waste fired fluidized bed boiler in Boraas while maintaining a stable operation with sufficient combustion temperature in the freeboard to fulfil the directives of waste incineration. A continuation of the project will be based on the results from present study. The work is based on experiments at the test boiler. During the present study, no other measurements were performed apart from some sampling of bed material and ashes at different modes of operation. The experiments show that it is possible to alter the air and recycled flue gas in such a manner that the bed temperature is reduced from about 870 deg C to 700 deg C at 100% load and normal fuel mixture, while fulfilling the directive of 850 deg C at 2 seconds. Within normal variations of the fuel properties, however, the bed temperature increases to somewhat above 700 deg C if the fuel turns dry, while it falls below 650 deg C when the fuel turns wet. With

  8. Fluidised bed technology – Applications and R&D in Southern Africa

    CSIR Research Space (South Africa)

    North, BC

    2007-06-28

    Full Text Available .csir.co.zaSlide 12 Minerals Treatment • Pyrite roasters (Gold industry) • Zinc Sulphide roasters • Ilmenite roasting (to assist in Chrome removal) • Recovery of gold from gold industry waste • Drying A p p l i c a t i o n s o f F B T A p... t i o n s o f F B T © CSIR 2006 www.csir.co.zaSlide 23 Combustion - CSIR WOODCHIP INCINERATOR Bed area : 6 m2 Plant purpose : Incineration of woodchips and carbon to enable recovery of precious metals. Original...

  9. SIMULATION OF THE DRYING CHARACTERISTICS OF GROUND NEEM SEEDS IN A FLUIDISED BED

    Directory of Open Access Journals (Sweden)

    A. KUYE

    2007-04-01

    Full Text Available The neem seed is a good source of neem oil as well as insecticides and pesticides. The oil and insecticides can be extracted by two consecutive leaching of neem seed kernels with hexane and ethanol. This work presents a model for simulating the drying of neem seeds in a fluidized bed. Experimental values obtained from literature were used to validate the model prediction. The drying simulation results show that there was a good agreement between the experimental values and the corresponding model predictions.

  10. CFD-DEM study of effect of bed thickness for bubbling fluidized beds

    Energy Technology Data Exchange (ETDEWEB)

    Tingwen, Li; Gopalakrishnan, Pradeep; Garg, Rahul; Shahnam, Mehrdad

    2011-10-01

    The effect of bed thickness in rectangular fluidized beds is investigated through the CFD–DEM simulations of small-scale systems. Numerical results are compared for bubbling fluidized beds of various bed thicknesses with respect to particle packing, bed expansion, bubble behavior, solids velocities, and particle kinetic energy. Good two-dimensional (2D) flow behavior is observed in the bed having a thickness of up to 20 particle diameters. However, a strong three-dimensional (3D) flow behavior is observed in beds with a thickness of 40 particle diameters, indicating the transition from 2D flow to 3D flow within the range of 20–40 particle diameters. Comparison of velocity profiles near the walls and at the center of the bed shows significant impact of the front and back walls on the flow hydrodynamics of pseudo-2D fluidized beds. Hence, for quantitative comparison with experiments in pseudo-2D columns, the effect of walls has to be accounted for in numerical simulations.

  11. Dry formulations of the biocontrol agent Candida sake CPA-1 using fluidised bed drying to control the main postharvest diseases on fruits.

    Science.gov (United States)

    Carbó, Anna; Torres, Rosario; Usall, Josep; Fons, Estanislau; Teixidó, Neus

    2017-08-01

    The biocontrol agent Candida sake CPA-1 is effective against several diseases. Consequently, the optimisation of a dry formulation of C. sake to improve its shelf life and manipulability is essential for increasing its potential with respect to future commercial applications. The present study aimed to optimise the conditions for making a dry formulation of C. sake using a fluidised bed drying system and then to determine the shelf life of the optimised formulation and its efficacy against Penicillium expansum on apples. The optimal conditions for the drying process were found to be 40 °C for 45 min and the use of potato starch as the carrier significantly enhanced the viability. However, none of the protective compounds tested increased the viability of the dried cells. A temperature of 25 °C for 10 min in phosphate buffer was considered as the optimum condition to recover the dried formulations. The dried formulations should be stored at 4 °C and air-packaged; moreover, shelf life assays indicated good results after 12 months of storage. The formulated products maintained their biocontrol efficacy. A fluidised bed drying system is a suitable process for dehydrating C. sake cells; moreover, the C. sake formulation is easy to pack, store and transport, and is a cost-effective process. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

  12. Leaching Behavior of Circulating Fluidised Bed MSWI Air Pollution Control Residue in Washing Process

    Directory of Open Access Journals (Sweden)

    Zhiliang Chen

    2016-09-01

    Full Text Available In this study, air pollution control (APC residue is conducted with water washing process to reduce its chloride content. A novel electrical conductivily (EC measurement method is proposed to monitor the dynamic change of chloride concentrations in leachate as well as the chloride content of the residue. The method equally applies to various washing processes with different washing time, liquid/solid ratio and washing frequency. The results show that washing effectively extracts chloride salts from APC residues, including those from circulating fluidized bed (CFB municipal solid waste incineration (MSWI. The most appropriate liquid/solid ratio and washing time in the first washing are found to be around 4 L water per kg of APC residue and 30 min, respectively, and washing twice is required to obtain maximum dissolution. The pH value is the major controlling factor of the heavy metals speciation in leachate, while chloride concentration also affects the speciation of Cd. Water washing causes no perceptible transfer of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs from the APC residue to leachate. The chloride concentration is strongly related with electrical conductivity (EC, as well as with the concentrations of calcium, sodium and potassium of washing water. Their regression analyses specify that soluble chloride salts and EC could act as an indirect indicator to monitor the change of chloride concentration and remaining chloride content, thus, contributing to the selection of the optimal washing conditions.

  13. Laboratory investigations on sorbents for control and reduction of acid emissions from atmospheric fluidised bed combustors

    Energy Technology Data Exchange (ETDEWEB)

    Schmal, D.; Ligtvoet, A.C.P.

    1991-06-10

    One of the main problems in the combustion of solid fuels is the formation and emission of sulfur-, nitrogen-, and halogen-based acidic gaseous compounds. In the framework of the TNO (Dutch organization for applied scientific research) research program on fluidized bed combustion of coal for industrial heat and electricity generation, laboratory investigations were carried out on the physical and chemical aspects of the removal of various acidic gas emissions. Attention is paid to acidic compounds that can be converted or removed by reaction at high temperatures with appropriate solid sorbents to be added at the installation. The acids investigated are SO{sub 2}, HCl, HF, and N{sub 2}O. Relatively simple methods were developed for sulfur dioxide to decrease the quantity of limestone needed for effective removal. The investigations on hydrochloric acid were directed towards the development of methods which can be easily incorporated in existing installations if in the future removal of these compounds should be required. For nitrous oxide, some orientating investigations were performed on the reaction with calcium cyanamide. The experiments showed that it is possible to use this compound to remove nitrous oxide. 20 figs., 7 tabs., 19 refs.

  14. Strategies to reduce gaseous KCl and chlorine in deposits during combustion of biomass in fluidised bed boilers

    Energy Technology Data Exchange (ETDEWEB)

    Kassman, Haakan

    2012-11-01

    Combustion of a biomass with an enhanced content of alkali and chlorine (Cl) can result in operational problems including deposit formation and superheater corrosion. The strategies applied to reduce such problems include co-combustion and the use of additives. In this work, measures were investigated in order to decrease the risk of superheater corrosion by reducing gaseous KCl and the content of chlorine in deposits. The strategies applied were sulphation of KCl by sulphur/sulphate containing additives (i.e. elemental sulphur (S) and ammonium sulphate (AS)) and co-combustion with peat. Both sulphation of KCl and capture of potassium (K) in ash components can be of importance when peat is used. The experiments were mainly performed in a 12 MW circulation fluidised bed (CFB) boiler equipped for research purposes but also in a full-scale CFB boiler. The results were evaluated by means of IACM (on-line measurements of gaseous KCl), conventional gas analysis, deposit and corrosion probe measurements and ash analysis. Ammonium sulphate performed significantly better than elemental sulphur. Thus the presence of SO{sub 3} (i.e. AS) is of greater importance than that of SO{sub 2} (i.e. S) for sulphation of gaseous KCl and reduction of chlorine in deposits. Only a minor reduction of gaseous KCl was obtained during co-combustion with peat although chlorine in the deposits was greatly reduced. This reduction was supposedly due to capture of K by reactive components from the peat ash in parallel to sulphation of KCl. These compounds remained unidentified. The effect of volatile combustibles on the sulphation of gaseous KCl was investigated. The poorest sulphation was attained during injection of ammonium sulphate in the upper part of the combustion chamber during the lowest air excess ratio. The explanation for this is that SO{sub 3} was partly consumed by side reactions due to the presence of combustibles. These experimental results were supported by modelling, although the

  15. A Bubble-Based Drag Model at the Local-Grid Level for Eulerian Simulation of Bubbling Fluidized Beds

    Directory of Open Access Journals (Sweden)

    Kun Hong

    2016-01-01

    Full Text Available A bubble-based drag model at the local-grid level is proposed to simulate gas-solid flows in bubbling fluidized beds of Geldart A particles. In this model, five balance equations are derived from the mass and the momentum conservation. This set of equations along with necessary correlations for bubble diameter and voidage of emulsion phase is solved to obtain seven local structural parameters (uge, upe, εe, δb, ub, db, and ab which describe heterogeneous flows of bubbling fluidized beds. The modified drag coefficient obtained from the above-mentioned structural parameters is then incorporated into the two-fluid model to simulate the hydrodynamics of Geldart A particles in a lab-scale bubbling fluidized bed. The comparison between experimental and simulation results for the axial and radial solids concentration profiles is promising.

  16. Bubbling fluidized bed boiler for Vanaja power plant

    Energy Technology Data Exchange (ETDEWEB)

    Sormunen, R.; Haermae, P.; Vessonen, K.; Ketomaeki, A. [ed.

    1998-07-01

    At the Vanaja Power Plant, on the outskirts of Haemeenlinna, there have been changes which reflect the central goals in IVO`s product development work. At Vanaja, efficiency is combined with environmental friendliness. In the early 1980s, the plant was modernized to produce district heat in addition to electricity. At that time, along with the new gas turbine at the plant, the main fuel, coal, while remaining the fuel for the old boilers, was replaced by natural gas. This year a new type of bubbling fluidized bed boiler enabling continuous use of peat and trial use of biofuels along with coal was introduced at the plant. In addition to the Nordic countries, this kind of technology is required in central eastern Europe, where modernization of ageing power plants is being planned to achieve the best possible solutions in respect of production and the environment. IVO develops a new repair technique for underwater sites

  17. Evaluation of encapsulated liver cell spheroids in a fluidised-bed bioartificial liver for treatment of ischaemic acute liver failure in pigs in a translational setting.

    Directory of Open Access Journals (Sweden)

    Clare Selden

    Full Text Available Liver failure is an increasing problem. Donor-organ shortage results in patients dying before receiving a transplant. Since the liver can regenerate, alternative therapies providing temporary liver-support are sought. A bioartificial-liver would temporarily substitute function in liver failure buying time for liver regeneration/organ-procurement. Our aim: to develop a prototype bioartificial-liver-machine (BAL comprising a human liver-derived cell-line, cultured to phenotypic competence and deliverable in a clinical setting to sites distant from its preparation. The objective of this study was to determine whether its use would improve functional parameters of liver failure in pigs with acute liver failure, to provide proof-of-principle. HepG2 cells encapsulated in alginate-beads, proliferated in a fluidised-bed-bioreactor providing a biomass of 4-6 × 10(10cells, were transported from preparation-laboratory to point-of-use operating theatre (6000 miles under perfluorodecalin at ambient temperature. Irreversible ischaemic liver failure was induced in anaesthetised pigs, after portal-systemic-shunt, by hepatic-artery-ligation. Biochemical parameters, intracranial pressure, and functional-clotting were measured in animals connected in an extracorporeal bioartificial-liver circuit. Efficacy was demonstrated comparing outcomes between animals connected to a circuit containing alginate-encapsulated cells (Cell-bead BAL, and those connected to circuit containing alginate capsules without cells (Empty-bead BAL. Cells of the biomass met regulatory standards for sterility and provenance. All animals developed progressive liver-failure after ischaemia induction. Efficacy of BAL was demonstrated since animals connected to a functional biomass (+ cells had significantly smaller rises in intracranial pressure, lower ammonia levels, more bilirubin conjugation, improved acidosis and clotting restoration compared to animals connected to the circuit without

  18. 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

  19. Ruedersdorf cement works substitutes raw material and fuel by means of a circulating fluidised bed; Roh- und Brennstoffsubstitution mit einer Zirkulierenden Wirbelschicht im Zementwerk Ruedersdorf

    Energy Technology Data Exchange (ETDEWEB)

    Scur, P. [Ruedersdorfer Zement GmbH, Ruedersdorf (Germany)

    1998-09-01

    The purpose of the present paper is to point out the great potential the cement industry holds for the utilisation of waste materials. There are meanwhile sufficient studies and measuring results to demonstrate the environmental acceptability of the processes and products involved. The solution found for Ruedersdorf cement kiln of using a circulating a fluidised bed for waste utilisation is a good example of the potential still available for conserving natural resources and landfill area. Efficient industrial applications of this kind should become a future mainstay of the waste industry. [Deutsch] In dem vorliegenden Beitrag sollte gezeigt werden, dass die Zementindustrie ueber ein hohes Potential zur thermischen und stofflichen Verwertung von Abfallstoffen verfuegt. Es liegen ausreichende Untersuchungen und konkrete Messergebnisse vor, mit denen die Umweltvertraeglichkeit von Prozess und Produkt nachgewiesen werden kann. Die Loesung zur Abfallverwertung an der Ruedersdorfer Zementofenanlage mit Hilfe einer Zirkulierenden Wirbelschicht ist ein Beispiel fuer die Reserven zur Schonung natuerlicher Ressourcen und zur Einsparung von Deponieraeumen. Derartige sinnvolle industrielle Einsatzmoeglichkeiten sollten ein wichtiges Standbein fuer die zukuenftige Abfallwirtschaft sein. (orig.)

  20. General project - Ash problem at wood fired fluidised bed plants. Phase 2; Ramprojekt - Askproblem vid skogsbraensleeldning i fluidbadd. Etapp 2

    Energy Technology Data Exchange (ETDEWEB)

    Hansson, Soeren; Kallner, Per; Ljungdahl, Boo; Wrangensten, Lars; Stalenheim, Annika; Goldschmidt, Barbara

    2003-10-01

    Some of the most common and most expensive problems concerning biomass fuelling are bed material agglomeration (fluid bed boilers) and ash deposits on superheater surfaces leading to corrosion and decreased heat transfer. During the preparation of the project it was noticed that much information was lacking concerning the causes for and preventive measures against deposit formation. The aim of the project is to increase the knowledge of which processes and conditions cause ash deposits on high temperature surfaces after the furnace. Sintering tendencies in bed recirculation cyclones are considered particularly. For this purpose a plant with a history of sintering problems in the cyclone has been chosen for measurements of gas temperature, cyclone wall temperature, gas composition, deposit growth and composition, fuel analysis, bottom ash, bed material and bed recirculation material. Three operating conditions have been investigated: normal operation, normal operation with low oxygen content, normal operation with low oxygen content and high cyclone temperature. Measurements during one week were made for each operating condition. As a reference, a less comprehensive measurement was made with two operating conditions at another CFB. In addition to the measurements, CFD modelling of the bed recirculation cyclones as well as laboratory sintering tests of collected bed material were made. The results of the measurements were in short, that the main investigated parameter high oxygen content - did not significantly influence the deposit formation or sintering tendencies of the cyclone ash. Instead, the cause seems to be a high cyclone ash temperature caused by char burning. The measurements and analysis of the cyclone ash showed that all ashes have high melting points and are not sticky at the relevant cyclone temperatures (850-900 deg C). Melting point calculations and laboratory tests are consistent. The composition of the deposits did not differ for the various

  1. Fluidised-bed spray-drying formulations of Candida sake CPA-1 by adding biodegradable coatings to enhance their survival under stress conditions.

    Science.gov (United States)

    Carbó, Anna; Torres, Rosario; Usall, Josep; Solsona, Cristina; Teixidó, Neus

    2017-11-01

    The biocontrol agent Candida sake CPA-1 has demonstrated to be effective against several diseases on fruit. However, for application of CPA-1 under field conditions, it was necessary to mix it with a food coating to improve survival under stress conditions, as well as adherence and distribution on fruit surfaces. The objective of this study was to obtain a more competitive formulation under field conditions to be applied independently of any product. To achieve this purpose, the drying process of CPA-1 by a fluidised-bed spray-drying system together with biodegradable coatings was optimised. This approach is novel for the drying system used and the formulation obtained which was able to form a film or coating on fruit surfaces. Several substances were tested as carriers and binders, and drying temperature was optimised. The addition of protective compounds was also tested to improve survival of CPA-1 during the dehydration process. Product shelf life, biocontrol efficacy on grapes against Botrytis cinerea, and the improvement of C. sake behaviour under stress conditions were tested. The optimal temperature of drying was 55 °C and two formulations that were able to develop a coating on fruit surfaces were obtained. One of the formulations was created by using a combination of native and pregelatinised potato starch; the other formulation was obtained using maltodextrin and by adding skimmed milk and sucrose as protectant compounds. The formulated products reduced the incidence and severity of B. cinerea, and CPA-1 survival rate was increased under stress conditions of temperature and humidity.

  2. Investigation of coalescence kinetics of microcristalline cellulose in fluidised bed spray agglomeration: experimental studies and modelling approach

    Directory of Open Access Journals (Sweden)

    M. Peglow

    2005-06-01

    Full Text Available In this paper a model for fluidized bed spray agglomeration is presented. To describe the processes of heat and mass transfer, a physical based model is derived. The model takes evaporation process from the wetted particles as well as the effects of transfer phenomena between suspension gas and bypass gas into account. The change of particle size distribution during agglomeration, modeled by population balances, is linked to the heat and mass transfer model. A new technique is derived to extract agglomeration and nucleation rates from experimental data. Comparisons of experiments and simulations are presented.

  3. Experimental study of Cynara Cardunculus L. gasification in bubbling fluidised bed : agglomeration, gas, tars and fly ash

    OpenAIRE

    Serrano García, Daniel

    2016-01-01

    Mención Internacional en el título de doctor El uso de biomasa como recurso energético puede reducir la dependencia actual que hay de los combustibles fósiles hacia un desarrollo más concienciado con el medio ambiente. Este hecho también puede ser empleado para tratar diferentes tipos de residuos que son generados en grandes cantidades como residuos sólidos urbanos, lodos de depuradora o residuos agrícolas, obteniendo productos útiles y reduciendo su eliminación en vertedero...

  4. Aerobic Biodegradation of Vinegar Containing Waste Water by Mixed Culture Bacteria from Soil in Fluidised Bed Reactor

    Directory of Open Access Journals (Sweden)

    Subba Rao Kumbha

    2014-09-01

    Full Text Available The present study is focussed on biodegradation of the vinegar effluents by mixed culture bacteria isolated from the soil. The presence of acetic acid in the vinegar plant effluent contaminates the water and soil erodes if the effluent is released into the soil, ultimately contaminate the ground water table. It is necessary to remove acetic acid from the vinegar plant effluents. The technique used in this study in order to remove biodegradable matter is Aerobic Biodegradation. Varying initial concentrations of vinegar is synthetically prepared in the laboratory, which resembled the effluent released from the vinegar plant by adding the vinegar of 1%, 4%, 7% to 1250 ml water respectively. The mixed culture bacteria from the soil grown on standard Lysogeny Broth medium and introduced into the aerobic fluidized bed reactor after 24 hours and the bacteria (Bacilli, Coccibiodegraded the organic matter i.e., acetic acid present in the sample. Samples analysed for vinegar concentration, DO and salinity, electrical conductivity for every 24hr, 48hr, and 72hr by volumetric analysis. The pH, DO, salinity, electrical conductivity and concentrations of the each samples measured for every 24hr, 48hr, and 72hr respectively. The pH of 1%, 4% & 7% samples varied from 6 to 9, 5 to 8.5 & 3 to 7 respectively from day1 to day3. The dissolved oxygen altered from 4ppm to 1ppm for 1% sample from day1 to day3 and from 5ppm to 2ppm for 4% vinegar sample for day1 o day3. Electrical conductivity of 1% vinegar sample increased from 52 to 58 from day1 to day3.

  5. CFD – facilitated Prognosis of Bubble Bed Bioreactor Performance Based on Bubble Swarms Oscillation Analysis

    OpenAIRE

    Vlaev, S. D.; Staykov, P.; Fialova, M.

    2009-01-01

    Bubble column reactors are widely used as gas-liquid and gas liquid-solid contactors in biotechnology applications. A basic issue in biotechnology is oxygen availability related to gas hold-up distribution, since aerobic bioprocessing depends on the dissolved oxygen substrate. The aim of this study is to analyze oxygen availability in bubble column bioreactors in terms of specific spatial and temporal gas-liquid flow. 3D CFD simulation is used to simulate the dispersed gas-liquid flow field o...

  6. Metal wastage design guidelines for bubbling fluidized-bed combustors. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Lyczkowski, R.W.; Podolski, W.F.; Bouillard, J.X.; Folga, S.M. [Argonne National Lab., IL (United States)

    1992-11-01

    These metal wastage design guidelines identify relationships between metal wastage and (1) design parameters (such as tube size, tube spacing and pitch, tube bundle and fluidized-bed height to distributor, and heat exchanger tube material properties) and (2) operating parameters (such as fluidizing velocity, particle size, particle hardness, and angularity). The guidelines are of both a quantitative and qualitative nature. Simplified mechanistic models are described, which account for the essential hydrodynamics and metal wastage processes occurring in bubbling fluidized beds. The empirical correlational approach complements the use of these models in the development of these design guidelines. Data used for model and guideline validation are summarized and referenced. Sample calculations and recommended design procedures are included. The influences of dependent variables on metal wastage, such as solids velocity, bubble size, and in-bed pressure fluctuations, are discussed.

  7. High temperature degradation by erosion-corrosion in bubbling fluidized bed combustors

    Directory of Open Access Journals (Sweden)

    Hou Peggy

    2004-01-01

    Full Text Available Heat-exchanger tubes in fluidized bed combustors (FBCs often suffer material loss due to combined corrosion and erosion. Most severe damage is believed to be caused by the impact of dense packets of bed material on the lower parts of the tubes. In order to understand this phenomenon, a unique laboratory test rig at Berkeley was designed to simulate the particle hammering interactions between in-bed particles and tubes in bubbling fluidized bed combustors. In this design, a rod shaped specimen is actuated a short distance within a partially fluidized bed. The downward specimen motion is controlled to produce similar frequencies, velocities and impact forces as those experienced by the impacting particle aggregates in practical systems. Room temperature studies have shown that the degradation mechanism is a three-body abrasion process. This paper describes the characteristics of this test rig, reviews results at elevated temperatures and compares them to field experience. At higher temperatures, deposits of the bed material on tube surfaces can act as a protective layer. The deposition depended strongly on the type of bed material, the degree of tube surface oxidation and the tube and bed temperatures. With HCl present in the bed, wastage was increased due to enhanced oxidation and reduced oxide scale adherence.

  8. 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 a...

  9. Experimental study on solids mixing and bubble behavior in a pseudo-2D, freely bubbling, gas-solid fluidized bed using PIV and DIA

    NARCIS (Netherlands)

    Laverman, J.A.; Roghair, Ivo; van Sint Annaland, M.; Kuipers, J.A.M.

    2007-01-01

    The hydrodynamics of a freely bubbling, gas-solid fluidized bed has been investigated experimentally with non-invasive measuring techniques in a pseudo-2D column filled with glass beads of 400-600 μm fluidized with air. Particle Image Velocimetry (PIV) combined with Digital Image Analysis (DIA) has

  10. A Study of Vertical Gas Jets in a Bubbling Fluidized Bed

    Energy Technology Data Exchange (ETDEWEB)

    Ceccio, Steven [Univ. of Michigan, Ann Arbor, MI (United States); Curtis, Jennifer [Univ. of Florida, Gainesville, FL (United States)

    2011-04-15

    A detailed experimental study of a vertical gas jet impinging a fluidized bed of particles has been conducted with the help of Laser Doppler Velocimetry measurements. Mean and fluctuating velocity profiles of the two phases have been presented and analyzed for different fluidization states of the emulsion. The results of this work would be greatly helpful in understanding the complex two-phase mixing phenomenon that occurs in bubbling beds, such as in coal and biomass gasification, and also in building more fundamental gas-solid Eulerian/Lagrangian models which can be incorporated into existing CFD codes. Relevant simulations to supplement the experimental findings have also been conducted using the Department of Energy's open source code MFIX. The goal of these simulations was two-fold. One was to check the two-dimensional nature of the experimental results. The other was an attempt to improve the existing dense phase Eulerian framework through validation with the experimental results. In particular the sensitivity of existing frictional models in predicting the flow was investigated. The simulation results provide insight on wall-bounded turbulent jets and the effect frictional models have on gas-solid bubbling flows. Additionally, some empirical minimum fluidization correlations were validated for non-spherical particles with the idea of extending the present study to non-spherical particles which are more common in industries.

  11. A system for measuring bubble voidage and frequency around tubes immersed in a fluidized bed of particles.

    Science.gov (United States)

    Whitty, Kevin J; Siddoway, Michael

    2010-07-01

    Gas-solid fluidized beds are common in chemical processing and energy production industries. These types of reactors frequently have banks of tubes immersed within the bed to provide heating or cooling, and it is important that the fluid dynamics within these bundles is efficient and uniform. This paper presents a simple, low-cost method for quantitatively analyzing the behavior of gas bubbles within banks of tubes in a fluidized bed cold flow model. Two probes, one containing an infrared emitter and one containing an infrared (IR) detector, are placed into adjacent glass tubes such that the emitter and detector face each other. As bubbles pass through the IR beam, the detector signal increases due to less solid material blocking the path between the emitter and detector. By calibrating the signal response to known voidage of the material, one can measure the bubble voidage at various locations within the tube bundle. The rate and size of bubbles passing through the beam can also be determined by high frequency data collection and subsequent analysis. This technique allows one to develop a map of bubble voidage within a fluidized bed, which can be useful for model validation and system optimization.

  12. 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.

  13. Gasification of torrefied Miscanthus × giganteus in an air-blown bubbling fluidized bed gasifier.

    Science.gov (United States)

    Xue, G; Kwapinska, M; Horvat, A; Kwapinski, W; Rabou, L P L M; Dooley, S; Czajka, K M; Leahy, J J

    2014-05-01

    Torrefaction is suggested to be an effective method to improve the fuel properties of biomass and gasification of torrefied biomass should provide a higher quality product gas than that from unprocessed biomass. In this study, both raw and torrefied Miscanthus × giganteus (M×G) were gasified in an air-blown bubbling fluidized bed (BFB) gasifier using olivine as the bed material. The effects of equivalence ratio (ER) (0.18-0.32) and bed temperature (660-850°C) on the gasification performance were investigated. The results obtained suggest the optimum gasification conditions for the torrefied M × G are ER 0.21 and 800°C. The product gas from these process conditions had a higher heating value (HHV) of 6.70 MJ/m(3), gas yield 2m(3)/kg biomass (H2 8.6%, CO 16.4% and CH4 4.4%) and cold gas efficiency 62.7%. The comparison between raw and torrefied M × G indicates that the torrefied M × G is more suitable BFB gasification. Copyright © 2014 Elsevier Ltd. All rights reserved.

  14. DOLOMITE DESULFURIZATION BEHAVIOR IN A BUBBLING FLUIDIZED BED PILOT PLANT FOR HIGH ASH COAL

    Directory of Open Access Journals (Sweden)

    G. M. F. Gomes

    Full Text Available Abstract Although fluidized bed in situ desulphurization from coal combustion has been widely studied, there are aspects that remain under investigation. Additionally, few publications address Brazilian coal desulphurization via fluidized beds. This study used a 250 kWth bubbling fluidized bed pilot plant to analyze different aspects of the dolomite desulphurization of two Brazilian coals. Superficial velocities of 0.38 and 0.46 m/s, flue gas recycling, Ca/S molar ratios and elutriation were assessed. Results confirmed the influence of the Ca/S molar ratio and superficial velocity - SO2 conversion up to 60.5% was achieved for one coal type, and 70.9% was achieved for the other type. A recycling ratio of 54.6% could increase SO2 conversion up to 86.1%. Elutriation and collection of ashes and Ca-containing products did not present the same behavior because a lower wt. % of CaO was collected by the gas controlled mechanism compared to the ash.

  15. Combustion performance evaluation of Posidonia oceanica using TGA and bubbling fluidized-bed combustor (batch reactor

    Directory of Open Access Journals (Sweden)

    Agnieszka Plis

    2016-01-01

    Full Text Available Combustion performance of emerging raw marine biomass called Posidonia oceanica (PO was investigated using TGA apparatus and a bubbling fluidized-bed batch reactor. The kinetic mechanism and parameters of the combustion process were determined. The Flynn-Wall-Ozawa (FWO method and data fitting method were analyzed. It was observed that a model based on consecutive processes: devolatilisation and char combustion for two fractions of PO (holocellulose and lignin, is the best model for the analyzed cases. Combustion performance was observed using a BFB reactor and the composition of flue gas after combustion was analyzed, and the conversion of NOx and SO2 was taken into account. The relatively low SO2 emission in the case of PO combustion can be attributed to the impact of the sulphur self-retention (SSR process. The results were compared to the combustion of wood biomass and Turow lignite. The results showed the good combustion performance of PO.

  16. Experimental study of a cocurrent upflow packed bed bubble column reactor: pressure drop, holdup and interfacial area

    NARCIS (Netherlands)

    Molga, E.J.; Westerterp, K.R.

    1997-01-01

    Gas¿liquid interfacial areas have been determined by means of chemically enhanced absorption of CO2 into DEA in a packed bed bubble column reactor with an inner diameter of 156 mm. The influence of the gas velocity and particle diameter on the interfacial areas, pressure drops and liquid holdups has

  17. Numerical Modelling of a Fast Pyrolysis Process in a Bubbling Fluidized Bed Reactor

    Science.gov (United States)

    Jalalifar, S.; Ghiji, M.; Abbassi, R.; Garaniya, V.; Hawboldt, K.

    2017-07-01

    In this study, the Eulerian-Granular approach is applied to simulate a fast pyrolysis bubbling fluidized bed reactor. Fast pyrolysis converts biomass to bio-products through thermochemical conversion in absence of oxygen. The aim of this study is to employ a numerical framework for simulation of the fast pyrolysis process and extend this to more complex reactor geometries. The framework first needs to be validated and this was accomplished by modelling a lab-scale pyrolysis fluidized bed reactor in 2-D and comparing with published data. A multi-phase CFD model has been employed to obtain clearer insights into the physical phenomena associated with flow dynamics and heat transfer, and by extension the impact on reaction rates. Biomass thermally decomposes to solid, condensable and non-condensable and therefore a multi-fluid model is used. A simplified reaction model is sued where the many components are grouped into a solid reacting phase, condensable/non-condensable phase, and non-reacting solid phase (the heat carrier). The biomass decomposition is simplified to four reaction mechanisms based on the thermal decomposition of cellulose. A time-splitting method is used for coupling of multi-fluid model and reaction rates. A good agreement is witnessed in the products yield between the CFD simulation and the experiment.

  18. A One-Dimensional (1-D) Three-Region Model for a Bubbling Fluidized-Bed Adsorber

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Andrew; Miller, David C.

    2012-01-01

    A general one-dimensional (1-D), three-region model for a bubbling fluidized-bed adsorber with internal heat exchangers has been developed. The model can predict the hydrodynamics of the bed and provides axial profiles for all temperatures, concentrations, and velocities. The model is computationally fast and flexible and allows for any system of adsorption and desorption reactions to be modeled, making the model applicable to any adsorption process. The model has been implemented in both gPROMS and Aspen Custom Modeler, and the behavior of the model has been verified.

  19. Study on the shape and flow characteristics of the formed bubbles in a pressurized fluidized bed. For the case of formed bubble from single nozzle; Kaatsu ryudosonai seisei kiho no keijo to sono ryudo ni kansuru kenkyu. Tan'itsu nozzle kara hasseisuru kiho no baa

    Energy Technology Data Exchange (ETDEWEB)

    Kato, Y.; Miyamoto, M.; Guo, Z. [Yamaguchi University, Yamaguchi (Japan); Kishimoto, Y. [Mitsubishi Kakoki Kaisha, Ltd., Tokyo (Japan)

    2000-12-25

    It is most important factors that were dealt with the size and production frequency of formed bubble and the rising state of bubble in the distributor vicinity at a solid-gas fluidized bed for the mixing and reacting process of the fluidized bed. Especially it is more complicated in the case of the pressurized fluidized bed. In order to understand the mechanism and behavior of the formed bubble, the investigations on the shape and flow characteristics of the formed bubble in a pressurized bed was carried out and bubbles were formed at a single nozzle in the pressurized solid-gas fluidized bed with distributor. Experimental data were obtained from visualized image of the bubble using the shadow-graph method and were analyzed. Those results indicate that the size and rising velocity of bubble were increased with relation to increase of the nozzle flow rate and these bubble behavior were varied with increase of the pressure in bed. (author)

  20. Experimental observations of dry powder inhaler dose fluidisation.

    Science.gov (United States)

    Tuley, Rob; Shrimpton, John; Jones, Matthew D; Price, Rob; Palmer, Mark; Prime, Dave

    2008-06-24

    Dry powder inhalers (DPIs) are widely used to deliver respiratory medication as a fine powder. This study investigates the physical mechanism of DPI operation, assessing the effects of geometry, inhalation and powder type on dose fluidisation. Patient inhalation through an idealised DPI was simulated as a linearly increasing pressure drop across three powder dose reservoir geometries permitting an analysis of shear and normal forces on dose evacuation. Pressure drop gradients of 3.3, 10 and 30 kPa s(-1)were applied to four powder types (glass, aluminium, and lactose 6 and 16% fines) and high speed video of each powder dose fluidisation was recorded and quantitatively analysed. Two distinct mechanisms are identified, labelled 'fracture' and 'erosion'. 'Fracture' mode occurs when the initial evacuation occurs in several large agglomerates whilst 'erosion' mode occurs gradually, with successive layers being evacuated by the high speed gas flow at the bed/gas interface. The mechanism depends on the powder type, and is independent of the reservoir geometries or pressure drop gradients tested. Both lactose powders exhibit fracture characteristics, while aluminium and glass powders fluidise as an erosion. Further analysis of the four powder types by an annular shear cell showed that the fluidisation mechanism cannot be predicted using bulk powder properties.

  1. Natural gas drying of the solid of slurry in a fluidized bed; Sechage au gaz naturel sur lit fluidise a jet de la partie solide du lisier

    Energy Technology Data Exchange (ETDEWEB)

    Duphily, C. [Centre des technologies du gaz naturel, Boucherville, PQ (Canada)

    1999-11-01

    On the invitation and the initiative of Gas Metropolitan, le centre des technologies du gaz naturel (CTGN) received a mandate for developing a technology that could handle a problem concerning a surplus of swine manure. This problem expressed itself in four main forms: 1) a surplus of manure on the farm-site, 2) a regional surplus of the same, 3) a release of odours, and 4) environmental concerns on the surrounding countryside. In collaboration with the Polytechniqie du Montreal, a management tool, PROGEST, was developed for these wastes. This process permits the drying of the swine wastes using natural gas on a jet fluidized bed followed by a heat treatment of the drying fumes in a combustion chamber. The deposits consisting of nearly 15% solids are sent along to a drying chamber where they dried and sterilized at 120 degrees C. The dried deposit recovered in the form of a powder in an assembly of a cyclone-deduster at the exit of the dryer can be granulated as needed and sold as a co-product. For example, it can be used as a fertilizer ingredient or as an ingredient in animal feed.

  2. 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.

  3. Validation of a two-fluid model used for the simulation of dense fluidized beds; Validation d`un modele a deux fluides applique a la simulation des lits fluidises denses

    Energy Technology Data Exchange (ETDEWEB)

    Boelle, A.

    1997-02-17

    A two-fluid model applied to the simulation of gas-solid dense fluidized beds is validated on micro scale and on macro scale. Phase coupling is carried out in the momentum and energy transport equation of both phases. The modeling is built on the kinetic theory of granular media in which the gas action has been taken into account in order to get correct expressions of transport coefficients. A description of hydrodynamic interactions between particles in high Stokes number flow is also incorporated in the model. The micro scale validation uses Lagrangian numerical simulations viewed as numerical experiments. The first validation case refers to a gas particle simple shear flow. It allows to validate the competition between two dissipation mechanisms: drag and particle collisions. The second validation case is concerted with sedimenting particles in high Stokes number flow. It allows to validate our approach of hydrodynamic interactions. This last case had led us to develop an original Lagrangian simulation with a two-way coupling between the fluid and the particles. The macro scale validation uses the results of Eulerian simulations of dense fluidized bed. Bed height, particles circulation and spontaneous created bubbles characteristics are studied and compared to experimental measurement, both looking at physical and numerical parameters. (author) 159 refs.

  4. Destruction and formation of PCDD/Fs in a fluidised bed combustor co-incinerating automotive shredder residue with refuse derived fuel and wastewater treatment sludge.

    Science.gov (United States)

    Van Caneghem, J; Vermeulen, I; Block, C; Van Brecht, A; Van Royen, P; Jaspers, M; Wauters, G; Vandecasteele, C

    2012-03-15

    During an eight day trial automotive shredder residue (ASR) was added to the usual waste feed of a Fluidized Bed Combustor (FBC) for waste-to-energy conversion; the input waste mix consisted of 25% ASR, 25% refuse-derived fuel (RDF) and 50% wastewater treatment (WWT) sludge. All inputs and outputs were sampled and the concentration of the 17 PCDD/Fs with TEF-values was determined in order to obtain "PCDD/F fingerprints". The ASR contained approximately 9000 ng PCDD/Fs/kg(DW), six times more than the RDF and 10 times more than the WWT sludge. The fingerprint of ASR and RDF was dominated by HpCDD and OCDD, which accounted for 90% of the total PDDD/F content, whereas the WWT sludge contained relatively more HpCDFs and OCDF (together 70%). The flue gas cleaning residue (FGCR) and fly and boiler ash contained approximately 30,000 and 2500 ng PCDD/Fs/kg(DW), respectively. The fingerprints of these outputs were also dominated by HpCDFs and OCDF. The bottom ash contained only OCDD and OCDF, in total 8 ng PCDD/Fs/kg (DW). From the comparison of the bottom ash fingerprints with the fingerprints of the other output fractions and of the inputs, it could be concluded that the PCDD/Fs in the waste were destroyed and new PCDD/Fs were formed in the post combustion process by de novo synthesis. During the ASR-co-incineration, the PCDD/F congener concentrations in the fly and boiler ash, FGCR and flue gas were 1.25-10 times higher compared to the same output fractions generated during incineration of the usual waste mix (70% RDF and 30% WWT sludge). The concentration of the higher chlorinated PCDD/Fs increased most. As these congeners have the lowest TEF-factors, the total PCDD/F output, expressed in kg TEQ/year, of the FBC did not increase significantly when ASR was co-incinerated. Due to the relatively high copper levels in the ASR, the copper concentrations in the FBCs outputs increased. As copper catalysis the de novo syntheses, this could explain the increase in PCDD

  5. CFD study of the minimum bubbling velocity of Geldart A particles in gas-fluidized beds

    NARCIS (Netherlands)

    Wang, J.; van der Hoef, Martin Anton; Kuipers, J.A.M.

    2010-01-01

    The minimum bubbling velocity, which demarcates the homogeneous and heterogeneous fluidization regimes, plays a pivotal role in gas fluidization of Geldart A particles. We systematically study the effect of gas and particle properties on the minimum bubbling velocity of Geldart A particles in

  6. Redistribution of velocity and bed-shear stress in straight and curved open channels by means of a bubble screen: laboratory experiments

    NARCIS (Netherlands)

    Blanckaert, K.; Buschman, F.A.; Schielen, R.; Wijbenga, J.H.A.

    2008-01-01

    Open-channel beds show variations in the transverse direction due to the interaction between downstream flow, cross-stream flow, and bed topography, which may reduce the navigable width or endanger the foundations of structures. The reported preliminary laboratory study shows that a bubble screen

  7. 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.

  8. Co-Fuelling of peat with meat and bone meal in a pilot scale bubbling bed reactor

    Energy Technology Data Exchange (ETDEWEB)

    McDonnell, K.; Cummins, E. J.; Fagan, C. C. [Biosystems Engineering, Bioresources Research Centre, UCD School of Agriculture, Food Science and Veterinary Medicine, Belfield, University College Dublin, Dublin 4 (Iran, Islamic Republic of); Orjala, M. [VTT Bioenergy, Koivurannantie, P.O. Box 1603, FIN- 40101 Jyvaeskylae (Finland)

    2010-07-15

    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/m{sup 3} limit upon combustion of pure MBM. SO{sub 2} emissions were found to be over the limit of 50 mg/m{sup 3}, while in all trials NO{sub x} emissions were below the limit of 300 mg/m{sup 3}. The HCl content of the flue gases was found to vary near the limit of 30 mg/m{sup 3}. VOCs however were within their limits. The problem of bed agglomeration was avoided when the bed temperature was about 850 {sup o}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. (authors)

  9. Overall modelling of circulating fluidised bed boilers

    Energy Technology Data Exchange (ETDEWEB)

    Werner, A.; Grausam, M.; Linzer, W. [Technische Univ., Vienna (Austria). Inst. fuer Technische Waermelehre; Loeffler, G.; Winter, F.; Hofbauer, H. [Technische Univ., Vienna (Austria). Inst. for Chemical Engineering, Fuel and Environmental Technology

    1999-07-01

    In the following an engineering simulation program for CFB-boilers is presented, which has been developed during the last years at ITW. Some parts of the model have been designed during a cooperation of different departments of TU. As a result the NO{sub x}/N{sub 2}O-model, which will be described more detailed in the following, was contributed from the Institute for Chemical Engineering. Studies about secondary air injection (and mixing) where done from the Institute of Fluid Dynamics and Heat Transfer. The main purposes of the simulator are the calculation of composition and size distribution of the boiler's inventory material, the determination of the heat flows at the heat exchanger surfaces installed to the furnace and the determination of flue gas composition, where especially the nitrogen compounds and SO{sub 2} are considered. (orig.)

  10. Sensitivity Analysis and Accuracy of a CFD-TFM Approach to Bubbling Bed Using Pressure Drop Fluctuations.

    Science.gov (United States)

    Tricomi, Leonardo; Melchiori, Tommaso; Chiaramonti, David; Boulet, Micaël; Lavoie, Jean Michel

    2017-01-01

    Based upon the two fluid model (TFM) theory, a CFD model was implemented to investigate a cold multiphase-fluidized bubbling bed reactor. The key variable used to characterize the fluid dynamic of the experimental system, and compare it to model predictions, was the time-pressure drop induced by the bubble motion across the bed. This time signal was then processed to obtain the power spectral density (PSD) distribution of pressure fluctuations. As an important aspect of this work, the effect of the sampling time scale on the empirical power spectral density (PSD) was investigated. A time scale of 40 s was found to be a good compromise ensuring both simulation performance and numerical validation consistency. The CFD model was first numerically verified by mesh refinement process, after what it was used to investigate the sensitivity with regards to minimum fluidization velocity (as a calibration point for drag law), restitution coefficient, and solid pressure term while assessing his accuracy in matching the empirical PSD. The 2D model provided a fair match with the empirical time-averaged pressure drop, the relating fluctuations amplitude, and the signal's energy computed as integral of the PSD. A 3D version of the TFM was also used and it improved the match with the empirical PSD in the very first part of the frequency spectrum.

  11. Sensitivity Analysis and Accuracy of a CFD-TFM Approach to Bubbling Bed Using Pressure Drop Fluctuations

    Directory of Open Access Journals (Sweden)

    Leonardo Tricomi

    2017-06-01

    Full Text Available Based upon the two fluid model (TFM theory, a CFD model was implemented to investigate a cold multiphase-fluidized bubbling bed reactor. The key variable used to characterize the fluid dynamic of the experimental system, and compare it to model predictions, was the time-pressure drop induced by the bubble motion across the bed. This time signal was then processed to obtain the power spectral density (PSD distribution of pressure fluctuations. As an important aspect of this work, the effect of the sampling time scale on the empirical power spectral density (PSD was investigated. A time scale of 40 s was found to be a good compromise ensuring both simulation performance and numerical validation consistency. The CFD model was first numerically verified by mesh refinement process, after what it was used to investigate the sensitivity with regards to minimum fluidization velocity (as a calibration point for drag law, restitution coefficient, and solid pressure term while assessing his accuracy in matching the empirical PSD. The 2D model provided a fair match with the empirical time-averaged pressure drop, the relating fluctuations amplitude, and the signal’s energy computed as integral of the PSD. A 3D version of the TFM was also used and it improved the match with the empirical PSD in the very first part of the frequency spectrum.

  12. Sensitivity Analysis and Accuracy of a CFD-TFM Approach to Bubbling Bed Using Pressure Drop Fluctuations

    Science.gov (United States)

    Tricomi, Leonardo; Melchiori, Tommaso; Chiaramonti, David; Boulet, Micaël; Lavoie, Jean Michel

    2017-01-01

    Based upon the two fluid model (TFM) theory, a CFD model was implemented to investigate a cold multiphase-fluidized bubbling bed reactor. The key variable used to characterize the fluid dynamic of the experimental system, and compare it to model predictions, was the time-pressure drop induced by the bubble motion across the bed. This time signal was then processed to obtain the power spectral density (PSD) distribution of pressure fluctuations. As an important aspect of this work, the effect of the sampling time scale on the empirical power spectral density (PSD) was investigated. A time scale of 40 s was found to be a good compromise ensuring both simulation performance and numerical validation consistency. The CFD model was first numerically verified by mesh refinement process, after what it was used to investigate the sensitivity with regards to minimum fluidization velocity (as a calibration point for drag law), restitution coefficient, and solid pressure term while assessing his accuracy in matching the empirical PSD. The 2D model provided a fair match with the empirical time-averaged pressure drop, the relating fluctuations amplitude, and the signal’s energy computed as integral of the PSD. A 3D version of the TFM was also used and it improved the match with the empirical PSD in the very first part of the frequency spectrum. PMID:28695119

  13. Study of a 30 MW bubbling fluidized bed combustor based on co ...

    Indian Academy of Sciences (India)

    determined distinctly. Singh et al (2013). 1. This paper summarized the CFD modeling tool to. 1. Due to variation in size of biomass particles the Eulerian– study combustion and gasification of fuels in fluidized. Eulerian approach with biomass considering bed devices combustion/gasification issues in dense fluidized beds is ...

  14. Study of a 30 MW bubbling fluidized bed combustor based on co ...

    Indian Academy of Sciences (India)

    During experimental investigations, the study of bed temperatures and steam temperatures at different zones has been done for coal fired and biomass fired combustors with 30% share. No clear effects of co-firing on boiler performance are observed. However, the operational behavior of the boiler in terms of bed ...

  15. Combustion of Biosolids in a Bubbling Fluidized Bed, Part 1: Main Ash-Forming Elements and Ash Distribution with a Focus on Phosphorus.

    Science.gov (United States)

    Skoglund, Nils; Grimm, Alejandro; Ohman, Marcus; Boström, Dan

    2014-02-20

    This is the first in a series of three papers describing combustion of biosolids in a 5-kW bubbling fluidized bed, the ash chemistry, and possible application of the ash produced as a fertilizing agent. This part of the study aims to clarify whether the distribution of main ash forming elements from biosolids can be changed by modifying the fuel matrix, the crystalline compounds of which can be identified in the raw materials and what role the total composition may play for which compounds are formed during combustion. The biosolids were subjected to low-temperature ashing to investigate which crystalline compounds that were present in the raw materials. Combustion experiments of two different types of biosolids were conducted in a 5-kW benchscale bubbling fluidized bed at two different bed temperatures and with two different additives. The additives were chosen to investigate whether the addition of alkali (K 2 CO 3 ) and alkaline-earth metal (CaCO 3 ) would affect the speciation of phosphorus, so the molar ratios targeted in modified fuels were P:K = 1:1 and P:K:Ca = 1:1:1, respectively. After combustion the ash fractions were collected, the ash distribution was determined and the ash fractions were analyzed with regards to elemental composition (ICP-AES and SEM-EDS) and part of the bed ash was also analyzed qualitatively using XRD. There was no evidence of zeolites in the unmodified fuels, based on low-temperature ashing. During combustion, the biosolid pellets formed large bed ash particles, ash pellets, which contained most of the total ash content (54%-95% (w/w)). This ash fraction contained most of the phosphorus found in the ash and the only phosphate that was identified was a whitlockite, Ca 9 (K,Mg,Fe)(PO 4 ) 7 , for all fuels and fuel mixtures. With the addition of potassium, cristobalite (SiO 2 ) could no longer be identified via X-ray diffraction (XRD) in the bed ash particles and leucite (KAlSi 2 O 6 ) was formed. Most of the alkaline-earth metals

  16. Improving the action of sulfur sorbents in the fluidized-bed combustion of coal

    Energy Technology Data Exchange (ETDEWEB)

    Schmal, D.

    1985-01-01

    As part of an investigation of the fluidised-bed combustion of coal and its environmental aspects, a study of the sorption of SO/sub 2/ as a combustion product has been undertaken. Special attention is being paid to the reactivation of fluidised-bed ash by treatment with water or water vapour, followed by heating to fluidised-bed temperatures. A laboratory research programme was carried out on the sulphation and reactivation of sorbents on their own, and of sorbent-containing ashes from a 4MW atmospheric fluidized-bed combustor. The experiments show that reactivation can be a versatile method for improving the efficiency of the sorbents.

  17. Fluidized bed Heat processing of domestic wastes. Evaluation of the 5 french operations assisted by the ADEME; Traitement thermique des dechets menagers en lit fluidise. Bilan des 5 operations francaises aidees par l'ADEME

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2002-03-01

    The fluidized bed combustion is a known technic for the coal or sewage sludges. Its application to the domestic wastes processing is more recent in France. Five units have been implemented in France. This document presents an evaluation of these five units operating. (A.L.B.)

  18. Effect of operating conditions on performance of silica gel-water air-fluidised desiccant cooler

    Science.gov (United States)

    Rogala, Zbigniew; Kolasiński, Piotr; Gnutek, Zbigniew

    2017-11-01

    Fluidised desiccant cooling is reported in the literature as an efficient way to provide cooling for air-conditioning purposes. The performance of this technology can be described by electric and thermal Coefficients of Performance (COP) and Specific Cooling Power (SCP). In this paper comprehensive theoretical study was carried out in order to assess the effect of operating conditions such as: superficial air velocity, desiccant particle diameter, bed switching time and desiccant filling height on the performance of fluidised desiccant cooler (FDC). It was concluded that FDC should be filled with as small as possible desiccant particles featuring diameters and should not be operated with shorter switching times than optimum. Moreover in order to efficiently run such systems superficial air velocities during adsorption and desorption should be similar. At last substantial effect of desiccant filling height on performance of FDC was presented.

  19. Experimental study of the mechanisms of CO{sub 2} capture by calcium cycle under circulating fluidized bed conditions; Etude experimentale des mecanismes de capture du CO{sub 2} par cycle calcium en lit fluidise circulant

    Energy Technology Data Exchange (ETDEWEB)

    Hoteit, A

    2006-06-15

    The work undertaken in this Thesis in partnership with department R and D of ALSTOM Power Boilers, CEMEX and the ADEME, relates to the experimental study of various phenomena associated to CO{sub 2} capture under circulating fluidized bed conditions. The size of particles, temperature and the CO{sub 2} concentration have an influence on the limestone calcination reaction. The reaction of carbonation of lime is not total. During successive cycles of calcination/carbonation, the rate of carbonation obtained with hydrated lime is increasingly higher than that obtained with the lime. Under continuously reducing conditions, the decomposition of sulphates present in the bed ashes is not total. This decomposition is total under reduction/oxidation cycles. A modeling of calcination allowed to determine the intrinsic kinetic constants of calcination and carbonation. (author)

  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. 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.

  2. Study of the behaviour of gaseous pollutants during the incineration of municipal solid waste in a circulating fluidized bed; Etude du devenir des polluants gazeux lors de l`incineration d`ordures menageres en lit fluidise circulant

    Energy Technology Data Exchange (ETDEWEB)

    Desroches-Ducarne, E.

    1997-09-30

    The Circulating Fluidized Bed (CFB) combustor seems to be a promising tool, being able to burn a variety of fuels whilst maintaining low emissions levels. The present work describes an experimental and theoretical investigation into the formation and destruction of acid gases (HCl and SO{sub 2}) and nitrogen oxides (NO and N{sub 2}O) during Municipal Solid Waste incineration. Experiments were conducted on six different fuels (namely MSW, mixtures of wood, paper, plastics, polyethylene...). The effect of five parameters (temperature, excess air, air staging, calcium addition and moisture) on the emissions levels was investigated. A statistical study on the experimental data allowed us to quantify the impact of the operating conditions and the influence of the fuel characteristics. A mathematical model has been developed which includes the main physical and chemical steps of combustion in CFB and which predicts the pollutant emissions under various operating conditions. A parametric study of the influence of operating conditions on emissions showed that in most cases the trends predicted by the model are in agreement with the experimental observations. (author) 175 refs.

  3. Numerical modelling 2 D and 3 D of circulating fluidized bed: application to the realization of regime diagrams; Modelisation numerique 2D et 3D de lit fluidise circulant: application a la realisation du diagramme des regimes

    Energy Technology Data Exchange (ETDEWEB)

    Begis, J.; Balzer, G.

    1997-02-01

    The numerical modelling of internal CFB boilers flows faced with complex phenomenons due to the flows un-stationariness, the heterogeneousness of the particle size distribution, and interactions between the two phases and the walls. Our study consisted in applying numerical models to the experimental configuration of cold circulating fluidized bed studied at the Cerchar. Special attention was given to the analysis of particles - wall interactions models, stemming from Jenkins (1992) and Louge`s (1994) theories, as well as the influence of the particles on fluid turbulence. In order to realize numerical simulations, we have used Eulerian two-phases flow codes developed at NHL medolif(2D), ESTET-ASTRID(3D). From different tests we have deducted that the most appropriate model for the realization of CFB`s prediction is the model taking in account the influence of particles on fluid turbulence. Then, to evaluate the validity limits of this model, we have built the regime diagram, and we have compared it with the experimental diagram. We have concluded that the simulation allows to describe the different CFB`s working regimes, and especially transitions. We have also noticed the importance of the choice of the mean diameter of the simulated particles. In this way, making a correction of the simulated particles` diameter in comparison with Sauter mean particle diameter, we obtained numerical results in good agreement with experimental data. (authors) 13 refs.

  4. CFD-DEM Simulation of Minimum Fluidisation Velocity in Two Phase Medium

    Directory of Open Access Journals (Sweden)

    H Khawaja

    2016-09-01

    Full Text Available In this work, CFD-DEM (computational fluid dynamics - discrete element method has been used to model the 2 phase flow composed of solid particle and gas in the fluidised bed. This technique uses the Eulerian and the Langrangian methods to solve fluid and particles respectively. Each particle is treated as a discrete entity whose motion is governed by Newton's laws of motion. The particle-particle and particle-wall interaction is modelled using the classical contact mechanics. The particles motion is coupled with the volume averaged equations of the fluid dynamics using drag law. In fluidised bed, particles start experiencing drag once the fluid is passing through. The solid particles response to it once drag experienced is just equal to the weight of the particles. At this moment pressure drop across the bed is just equal to the weight of particles divide by the cross-section area. This is the first regime of fluidization, also referred as ‘the regime of minimum fluidization’. In this study, phenomenon of minimum fluidization is studied using CFD-DEM simulation with 4 different sizes of particles 0.15 mm, 0.3 mm, 0.6 mm, and 1.2 mm diameters. The results are presented in the form of pressure drop across the bed with the fluid superficial velocity. The achieved results are found in good agreement with the experimental and theoretical data available in literature.

  5. Formation and destruction mechanisms of nitrogen oxides during coal combustion in circulating fluidized beds; Mecanismes de formation et de destruction des oxydes d`azote lors de la combustion du charbon en lit fluidise circulant

    Energy Technology Data Exchange (ETDEWEB)

    Borrel, G.; Lecuyer, I. [Universite du Haut-Rhin, 68 - Mulhouse (France)

    1997-01-01

    Formation and reduction of nitrogen oxides (NO and N{sub 2}O) during coal combustion in a circulating fluidized bed (CFBC) are very complicated and yet badly known. The aim of the present study was to better characterize these phenomena on a small-sized experimental unit (reactor diameter: 5 cm), with the possibility to re-inject the solids in the bottom of the furnace, as in a real industrial unit. This should allow then to develop a numerical set of chemical reactions involving the nitrogen oxides. The experimental results showed that coal ash plays a great role in reducing nitrogen oxides, the determining parameter being the quantity of unburnt carbon remaining in the ash. The study then detailed the interaction between nitrogen oxides and de-volatilized (char) according to the temperature, NO{sub x} concentration and the mass of solid. In the absence of oxygen small quantities of char can very significantly reduce NO as well as N{sub 2}O. It was possible to establish destruction kinetics on these particles, and orders of reaction could be determined versus the NO{sub x} concentration and the char particle mass (heterogeneous phase chemical reactions). Then, the coal pyrolysis study enabled to identify the products released during coal devolatilization and thermogravimetric analyses displayed several successive weight losses due CO, CO{sub 2} and CH{sub 4} releases, during a linear temperature increase. Lastly coal combustion was studied in the small pilot with variable experimental conditions. Using the previous experimental was studied in the small pilot with variable experimental conditions. Using the previous experimental results, a model was developed to calculate NO{sub x} concentrations during the coal combustion and validated. The NO and N{sub 2}O contents calculated are thoroughly correlated with the experimental data whatever the injection carbon/oxygen ratio is. (author) 96 refs.

  6. Bottom ash from fluidising bed boilers as filler material in district heating pipe culverts. Chemical and geotechnical characterisation; Pannsand som kringfyllnadsmaterial foer fjaerrvaermeroergravar. Kemisk och geoteknisk karaktaerisering av fluidbaeddsand

    Energy Technology Data Exchange (ETDEWEB)

    Pettersson, Roger; Rogbeck, Jan; Suer, Pascal

    2004-01-01

    Bottom ashes from fluid bed boilers have been characterised, both geotechnically and chemically, in order to investigate the possibility to use them as filler material in district heating pipe culverts. Bottom ashes from both biofuel boilers and waste boilers are represented in this project. The companies which ashes have been characterised are Sundsvall Energi AB, Sydkraft OestVaerme AB, Sydkraft MaelarVaerme AB, Eskilstuna Miljoe och Energi, Stora Enso Fors, Soederenergi and Fortum Vaerme. A total of ten ashes have been analysed where three ashes originates from Sundsvall Energi AB, two from Sydkraft OestVaerme AB and one from the each of the remaining companies. The chemical analyses have been performed both on fresh ashes and on ashes aged for three months. The geotechnical analyses performed are grain size distribution, packing abilities and permeability. Chemical analyses performed are total content, available content, leaching tests (leaching both by shaking method and column procedure) and organic analyses (PAH, EOX, TOC, dioxin and fenol). The geotechnical analyses show that the ashes fulfils the demands that are put on the filler material used in district heating pipe culverts. When using the ashes in applications, light compaction should be performed due to the risk of crushing the material which may cause an increased amount of fine material. The leachability of fine material is larger than for coarse material. The ashes are relatively insensitive to precipitation. Bio fuel based bottom ashes have a lower content of environmental affecting substances than waste fuel based ashes. This is also shown in the leaching analyses. The leaching water from fresh ashes contains a higher concentration of leachable components than aged ashes. When aged the pH in the ashes decreases due to carbon uptake and hydration and this makes metals as Pb, Cu, Cr and Zn less mobile. On the other hand, an increase in leachability of Sb, Mo and SO{sub 4} is shown when the ashes

  7. Bubbling bed catalytic hydropyrolysis process utilizinig larger catalyst particles and small biomass particles featuring an anti-slugging reactor

    Science.gov (United States)

    Marker, Terry L.; Felix, Larry G.; Linck, Martin B.; Roberts, Michael J.

    2016-12-06

    This invention relates to a process for thermochemically transforming biomass or other oxygenated feedstocks into high quality liquid hydrocarbon fuels. In particular, a catalytic hydropyrolysis reactor, containing a deep bed of fluidized catalyst particles is utilized to accept particles of biomass or other oxygenated feedstocks that are significantly smaller than the particles of catalyst in the fluidized bed. The reactor features an insert or other structure disposed within the reactor vessel that inhibits slugging of the bed and thereby minimizes attrition of the catalyst. Within the bed, the biomass feedstock is converted into a vapor-phase product, containing hydrocarbon molecules and other process vapors, and an entrained solid char product, which is separated from the vapor stream after the vapor stream has been exhausted from the top of the reactor. When the product vapor stream is cooled to ambient temperatures, a significant proportion of the hydrocarbons in the product vapor stream can be recovered as a liquid stream of hydrophobic hydrocarbons, with properties consistent with those of gasoline, kerosene, and diesel fuel. Separate streams of gasoline, kerosene, and diesel fuel may also be obtained, either via selective condensation of each type of fuel, or via later distillation of the combined hydrocarbon liquid.

  8. Behaviour of fluidised particles explained by a new theory

    Energy Technology Data Exchange (ETDEWEB)

    Rowe, P.N.; Furusawa, Takehiko

    1988-10-05

    The fine particles, less than 70 microns, to be used for the fluid catalytic cracker, are different from the coarse particles and expand the bed without generating bubbles at a higher fluid speed than the solid-gas fluid starting speed, because both the fluidization and bubble generating speeds are different from each other. Geldart classified, by using the particle diameter and gas density as indexes, the difference of particles in the fluid condition, which however is to be under the ordinary temperature and pressure, without the applicability to the high temperature and pressure fluid. Foscolo and Gibiraro submitted the theory to test clearly established it. Both the elastic wave and void factor propagation speeds, in the all Reynolds numbers' range where the bubble fluid appears, were conducted and derived. By that theory, the classification of high temperature and pressure particles is possible. As the fluid catalytic cracker is strongly influenced by the solid-gas catalytic condition in the bed, the movement of bubbles is important. By that theory together with formulas, the group of particles is clearly understandable in behavior, which also enables the prediction of important properties for practical use. (9 figs, 8 refs)

  9. Reactive Gas Solids Flow in Circulating Fluidised Beds

    DEFF Research Database (Denmark)

    Hjertager, Bjørn Helge; Solberg, Tron; Hansen, Kim Granly

    2005-01-01

    Progress in modelling and simulation of flow processes in gas/particle systems carried out at the authors? research group are presented. Emphasis is given to computational fluid dynamics (CFD) models that use the multi-dimensional multi fluid techniques. Turbulence modelling strategies for gas....../particle flows based on the kinetic theory for granular flows are given. Sub models for the interfacial transfer processes and chemical kinetics modelling are presented. Examples are shown for several gas/particle systems including flow in risers, segregation by size and reacting systems....

  10. Chemical Processes Related to Combustion in Fluidised Bed

    Energy Technology Data Exchange (ETDEWEB)

    Steenari, Britt-Marie; Lindqvist, Oliver [Chalmers Univ. of Technology, Goeteborg (Sweden). Dept. of Environmental Inorganic Chemistry

    2002-12-01

    This report covers work that has been carried out in the combustion chemistry group at the Dept. of Environmental Inorganic Chemistry, Chalmers, within the STEM project 12859-1, during the period 2000-07-01 to 2002-06-30. The work was comprised of the following parts: Sulphur chemistry under pressurised and atmospheric conditions; Gas/solid reactions related to sintering and fouling; Chemistry of volatile metals in combustion; Ash leaching properties; Theoretical modelling of the interactions between ions in a solution and mineral surfaces; Some related issues and co-operations with other departments. The work on sulphur chemistry has been a central issue in our group and it has now been finalised with a PhD thesis discussing some aspects of the sulphation of limestone under pressurised conditions. The influence of a number of parameters on the sulphation efficiency was investigated and compared with similar studies under atmospheric conditions. In a special study it was shown that the influence of alternating calcining - non-calcining conditions on the conversion was substantial. In addition, the oxidation of CaS and sulphided limestone was studied and a regeneration method for the sulphide sorbent was proposed. In the project part concerning gas - solid reactions that are relevant to sintering and fouling, the application of an on-line measurement technique for the study of alkali metal capture by kaolin or other sorbents is described. A new reactor set-up has been constructed and the initial results from this set up are promising. The chemistry of cadmium in combustion of MSW and biomass is the object of a PhD project. This work has been concentrated on the task of identifying Cd-compounds in fly ash samples. It has now come to a point where enough data has been collected to make it possible to give an indication about the Cd speciation in some ash types. In MSW ash particles, cadmium seem to occur mainly as chloride, oxide and sulphate. The work will continue with evaluation of other biomass ash particles and, as an extension, the speciation of Cu and Zn will be studied as well. Ash fractions from combustion of MSW in a BFB boiler have been investigated regarding composition and leaching properties, i.e. environmental impact risks. The release of salts from the cyclone ash fraction can be minimised by the application of a simple washing process, thus securing that the leaching of soluble substances stays within the regulative limits. The MSW ash - water systems contain some interesting chemical issues, such as the interactions between Cr(VI) and reducing substances like Al-metal. The understanding of such chemical processes is important since it gives a possibility to predict effects of a change in ash composition. An even more detailed understanding of interactions between a solution containing ions and particle surfaces can be gained by theoretical modelling. In this project (and with additional unding from Aangpannefoereningens Forskningsstiftelse) a theoretical description of ion-ion interactions and the solid-liquid-interface has been developed. Some related issues are also included in this report. The publication of a paper on the reactions of ammonia in the presence of a calcining limestone surface is one of them. A review paper on the influence of combustion conditions on the properties of fly ash and its applicability as a cement replacement in concrete is another. The licentiate thesis describing the sampling and measurement of Cd in flue gas is also included since it was finalised during the present period. A co-operation project involving the Geology Dept. at Goeteborg Univ. and our group is briefly discussed. This project concerns the utilisation of granules produced from wood ash and dolomite as nutrient source for forest soil. Finally, the plans for our flue gas simulator facility are discussed.

  11. Sustainable nitrification in fluidised bed reactor with immobilised ...

    African Journals Online (AJOL)

    2012-02-01

    Feb 1, 2012 ... +-N concentration was increased from 40 mg·ℓ-1 to 320 mg·ℓ-1, as soon as NH4. +-N removal efficiency of Reactor A reached 80%, in order to increase the capability of ... Additionally, in order to evaluate the impact of organic load on nitrification ... (2) where: k is the reaction rate of the nitrification reaction.

  12. Sustainable nitrification in fluidised bed reactor with immobilised ...

    African Journals Online (AJOL)

    2012-02-01

    Feb 1, 2012 ... pH (Ciudad et al., 2007). However, some options are not easily practicable. The inhibition of NOB may not be effective because of microbial adaptation ability. A relatively low DO is a crucial factor to achieve stable partial nitrification(Garrido et al., 1997) but a low-DO condition may cause the growth of ...

  13. Allothermal steam gasification of biomass in cyclic multi-compartment bubbling fluidized-bed gasifier/combustor - new reactor concept.

    Science.gov (United States)

    Iliuta, Ion; Leclerc, Arnaud; Larachi, Faïçal

    2010-05-01

    A new reactor concept of allothermal cyclic multi-compartment fluidized bed steam biomass gasification is proposed and analyzed numerically. The concept combines space and time delocalization to approach an ideal allothermal gasifier. Thermochemical conversion of biomass in periodic time and space sequences of steam biomass gasification and char/biomass combustion is simulated in which the exothermic combustion compartments provide heat into an array of interspersed endothermic steam gasification compartments. This should enhance unit heat integration and thermal efficiency and procure N(2)-free biosyngas with recourse neither to oxygen addition in steam gasification nor contact between flue and syngas. The dynamic, one-dimensional, multi-component, non-isothermal model developed for this concept accounts for detailed solid and gas flow dynamics whereupon gasification/combustion reaction kinetics, thermal effects and freeboard-zone reactions were tied. Simulations suggest that allothermal operation could be achieved with switch periods in the range of a minute supporting practical feasibility for portable small-scale gasification units. Copyright 2009 Elsevier Ltd. All rights reserved.

  14. Heat transfer to immersed horizontal tubes in gas fluidized bed dryers

    Energy Technology Data Exchange (ETDEWEB)

    Jonassen, Ola

    1999-10-01

    The main objective of this study was to construct heat pump fluidized bed dryers of the FHT type with improved dewatering capacity for a given size of the dryer. The use of heat exchangers immersed in the fluidized bed drying chambers is an important part of the FHT (Fluidized Bed High Temperature Heat Pump Dryer) concept. A pilot plant FHT dryer was built and successfully tested on fish meal raw material and seaweed. The plant included two fluidized bed drying chambers with immersed heat exchangers. The gain in water vapor of the drying air through the chambers was increased up to four times that of adiabatic drying. The energy saving concept was retained as a SMER ratio of 3.5 to 4.7 was measured in the same tests. Therefore optimization of the immersed heat exchangers was considered the most important single objective for this work. The optimization study of the heat exchangers was confined to the actual operating conditions for the dryers using: (1) Bubbling gas fluidized beds were used, (2) air as the only type of fluidising gas, (3) beds at atmospheric pressure, (4) bed temperatures below 100 {sup o}C, (5) fluidized particles of Geldart classes B and D, (6) horizontal tube banks for the immersed heat exchanger, and the influence of radiation heat transfer was ignored. The heat transfer study was confined to the fluidized bed side of the heat exchanger surface. It was concluded early in this work that the bubbles play a major role in generating the particle circulation inside the bed and hence also in heat transfer. Publications describing the most important bubble induced mechanisms contributing to high rates of heat transfer were found to be limited. Therefore the first part of this study was aimed at establishing a method for locating and measuring the size and rise velocity of bubbles inside the bed. The method established through this work using differential pressure measurements from two static pressure probes was used later in the study of heat transfer

  15. Reactions homogenes en phase gazeuse dans les lits fluidises

    Science.gov (United States)

    Laviolette, Jean-Philippe

    This thesis presents a study on homogeneous gas-phase reactions in fluidized beds. The main objective is to develop new tools to model and characterize homogeneous gas-phase reactions in this type of reactor. In the first part of this work, the non-premixed combustion of C 1 to C4 n-alkanes with air was investigated inside a bubbling fluidized bed of inert sand particles at intermediate temperatures: 923 K ≤ TB ≤ 1123 K. For ethane, propane and n-butane, combustion occurred mainly in the freeboard region at bed temperatures below T1 = 923 K. On the other hand, complete conversion occurred within 0.2 m of the injector at: T2 = 1073 K. For methane, the measured values of T1 and T2 were significantly higher at 1023 K and above 1123 K, respectively. The fluidized bed combustion was accurately modeled with first-order global kinetics and two one-phase PFR models in series: one PFR to model the region close to the injector and another to represent the main fluidized bed body. The measured global reaction rates for C2 to C4 n-alkanes were characterized by a uniform Arrhenius expression, while the global reaction rate for methane was significantly slower. Reactions in the injector region either led to significant conversion in that zone or an autoignition delay inside the main fluidized bed body. The conversion in the injector region increased with rising fluidized bed temperature and decreased with increasing jet velocity. To account for the promoting and inhibiting effects, an analogy was made with the concept of induction time: the PFR length (bi) of the injector region was correlated to the fluidized bed temperature and jet velocity using an Arrhenius expression. In the second part of this work, propane combustion experiments were conducted in the freeboard of a fluidized bed of sand particles at temperatures between 818 K and 923 K and at superficial gas velocity twice the minimum fluidization velocity. The freeboard region was characterized by simultaneous

  16. 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....

  17. Batch top-spray fluid bed coating: Scale-up insight using dynamic heat- and mass-transfer modelling

    DEFF Research Database (Denmark)

    Hede, Peter Dybdahl; Bach, P.; Jensen, Anker Degn

    2009-01-01

    A mathematical model was developed for batch top-spray fluid bed coating processes based on Ronsse et al. [2007a.b. Combined population balance and thermodynamic modelling of the batch top-spray fluidised bed coating process. Part I-model development and validation. journal of Food Engineering 78......, 296-307; Combined population balance and thermodynamic modelling of the batch top-spray fluidised bed coating process. Part II-model and process analysis. journal of Food Engineering 78, 308-322]. The model is based on one-dimensional discretisation of the fluid bed into a number of well-mixed control...

  18. Kinetics of gasification and combustion of residues, biomass and coal in a bubbling fluidized bed; Die Kinetik der Vergasung und Verbrennung unterschiedlicher Abfaelle, Biomassen und Kohlen in der blasenbildenden Wirbelschicht

    Energy Technology Data Exchange (ETDEWEB)

    Hamel, S.; Krumm, W. [Siegen Univ. (Gesamthochschule) (Germany). Lehrstuhl fuer Energie- und Umweltverfahrenstechnik

    1998-09-01

    The combustion and gasification characteristics of Rhenish brown coal, domestic waste, waste plastics, wood and sewage sludge were investigated in a bubbling atmospheric fluidized bed in the laboratory scale. The materials were pyrolyzed in the fluidized bed in a nitrogen atmosphere. The residual coke was combuted in the presence of oxygen with varying operating parameters or else gasified in the presence of carbon dioxide. The different materials were characterized by global combustion rates, and kinetic parameters were determined for residual coke combustion. (orig.) [Deutsch] Das Verbrennungs- und Vergasungsverhalten von Rheinischer Braunkohle, Hausmuell, Restkunststoff, Holz und Klaerschlamm wurde in einer blasenbildenden, atmosphaerischen Laborwirbelschicht untersucht. Die Einsatzstoffe wurden in der mit Stickstoff fluidisierten Wirbelschicht pyrolysiert. Der verbleibende Restkoks wurde anschliessend unter Variation der Betriebsparameter mit Sauerstoff verbrannt oder mit Kohlendioxid vergast. Die unterschiedlichen Einsatzstoffe wurden durch globale Vebrennungsraten charakterisiert. Fuer die Restkoksverbrennung wurden kinetische Parameter ermittelt. (orig.)

  19. Bubble coalescence

    NARCIS (Netherlands)

    Orvalho, Sandra; Ruzicka, Marek C.; Olivieri, Giuseppe; Marzocchella, Antonio

    2015-01-01

    The goal of this study is to present new experimental data on the effect of the bubble approach velocity and liquid viscosity on pairwise bubble coalescence. Measurements were performed to investigate the dynamics of bubble coalescence under well-defined laboratory conditions. Air and pure

  20. 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...

  1. 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

  2. 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)

  3. Bulk solid temperature or regulating process by means of a fluidized or mobile bed multicompartemented heat exchanger. Procede et dispositif de regulation ou controle du niveau thermique d'un solide pulverulent, comportant un echangeur de chaleur a compartiments en lit fluidise ou mobile

    Energy Technology Data Exchange (ETDEWEB)

    Pontier, R.; Hoffmann, F.

    1990-12-16

    A process and apparatus are disclosed for thermal regulation of mobile or fluidized catalyst beds. The apparatus comprises a fluidized or mobile bed heat exchanger. According to the invention, a pulverulent solid is made to circulate essentially at the base of an enclosure in a heat exchanger containing an internal separation partition which defines two elongated and adjacent compartments communicating by their lower part. In the compartment where the pulverulent solid flows downwards, the fluidization velocity is within the range of 0.1 cm/s and 2 m/s, while in the compartment where the rising of the pulverulent solid in the heat exchanger is carried out, the fluidization velocity is within the range of 0.1 and 6 m/s. The invention is applicable notably to refining reactions such as catalytic reforming, to the regeneration of a catalytic cracking catalyst, or to coal combustion. 4 figs., 1 tab.

  4. Bubble diagnostics

    Science.gov (United States)

    Visuri, Steven R.; Mammini, Beth M.; Da Silva, Luiz B.; Celliers, Peter M.

    2003-01-01

    The present invention is intended as a means of diagnosing the presence of a gas bubble and incorporating the information into a feedback system for opto-acoustic thrombolysis. In opto-acoustic thrombolysis, pulsed laser radiation at ultrasonic frequencies is delivered intraluminally down an optical fiber and directed toward a thrombus or otherwise occluded vessel. Dissolution of the occlusion is therefore mediated through ultrasonic action of propagating pressure or shock waves. A vapor bubble in the fluid surrounding the occlusion may form as a result of laser irradiation. This vapor bubble may be used to directly disrupt the occlusion or as a means of producing a pressure wave. It is desirable to detect the formation and follow the lifetime of the vapor bubble. Knowledge of the bubble formation and lifetime yields critical information as to the maximum size of the bubble, density of the absorbed radiation, and properties of the absorbing material. This information can then be used in a feedback system to alter the irradiation conditions.

  5. Filter Bubble vs. Preference Bubble

    OpenAIRE

    Lindström, Hanna-Stiina; Soliman, Gabriela

    2016-01-01

    Tämän opinnäytetyön aiheena oli internetin personointi ja siitä aiheutuva filter bubble –ilmiö. Tarkoituksena oli tutkia kuluttajien suhtautumista ilmiöön, jota Suomessa ei vielä tunnisteta laajasti. Suhtautuminen haluttiin tuoda esiin vastakkainasettelun avulla. Filter bubble –näkökulma edusti tässä työssä ilmiön negatiivista suhtautumistapaa ja preference bubble –näkökulma positiivista. Opinnäytetyö oli tietopaketti yrityksille Filter bubble –ilmiön ominaisuuksista sekä sen käyttäytymisestä...

  6. Leverage bubble

    Science.gov (United States)

    Yan, Wanfeng; Woodard, Ryan; Sornette, Didier

    2012-01-01

    Leverage is strongly related to liquidity in a market and lack of liquidity is considered a cause and/or consequence of the recent financial crisis. A repurchase agreement is a financial instrument where a security is sold simultaneously with an agreement to buy it back at a later date. Repurchase agreement (repo) market size is a very important element in calculating the overall leverage in a financial market. Therefore, studying the behavior of repo market size can help to understand a process that can contribute to the birth of a financial crisis. We hypothesize that herding behavior among large investors led to massive over-leveraging through the use of repos, resulting in a bubble (built up over the previous years) and subsequent crash in this market in early 2008. We use the Johansen-Ledoit-Sornette (JLS) model of rational expectation bubbles and behavioral finance to study the dynamics of the repo market that led to the crash. The JLS model qualifies a bubble by the presence of characteristic patterns in the price dynamics, called log-periodic power law (LPPL) behavior. We show that there was significant LPPL behavior in the market before that crash and that the predicted range of times predicted by the model for the end of the bubble is consistent with the observations.

  7. 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.

  8. A CFD-DEM study of single bubble formation in gas fluidization of spherical and non-spherical particles

    Directory of Open Access Journals (Sweden)

    Shrestha Siddhartha

    2017-01-01

    Full Text Available Bubble dynamics significantly affect the hydrodynamics of gas-solid fluidized bed since they influence the gas-solid mixing. In this study, simulations using CFD-DEM were carried out to characterize the bubble size and shape for a bubble formed at a single orifice in gas-solid fluidized bed. Impact of parameters such as jet velocity, orifice size and particle shape on bubble equivalent diameter and bubble aspect ratio were analysed and discussed. Bubble equivalent diameter was found to increase with increasing jet velocity, decreasing bed width to orifice width ratio, and particle shape deviating from spherical. The bubble shape illustrated by aspect ratio, was found to elongate more as it rise through the bed and then commence to expand horizontally after it was detached from the orifice. Aspect ratio was found to be closer to a circle for the bubble at higher jet velocity, lower orifice width to bed ratio and for non-spherical particles.

  9. A CFD-DEM study of single bubble formation in gas fluidization of spherical and non-spherical particles

    Science.gov (United States)

    Shrestha, Siddhartha; Zhou, Zongyan

    2017-06-01

    Bubble dynamics significantly affect the hydrodynamics of gas-solid fluidized bed since they influence the gas-solid mixing. In this study, simulations using CFD-DEM were carried out to characterize the bubble size and shape for a bubble formed at a single orifice in gas-solid fluidized bed. Impact of parameters such as jet velocity, orifice size and particle shape on bubble equivalent diameter and bubble aspect ratio were analysed and discussed. Bubble equivalent diameter was found to increase with increasing jet velocity, decreasing bed width to orifice width ratio, and particle shape deviating from spherical. The bubble shape illustrated by aspect ratio, was found to elongate more as it rise through the bed and then commence to expand horizontally after it was detached from the orifice. Aspect ratio was found to be closer to a circle for the bubble at higher jet velocity, lower orifice width to bed ratio and for non-spherical particles.

  10. Bubble bath soap poisoning

    Science.gov (United States)

    ... medlineplus.gov/ency/article/002762.htm Bubble bath soap poisoning To use the sharing features on this page, please enable JavaScript. Bubble bath soap poisoning occurs when someone swallows bubble bath soap. ...

  11. Bubble wake dynamics in liquids and liquid-solid suspensions

    CERN Document Server

    Fan, Liang-Shih; Brenner, Howard

    1990-01-01

    This book is devoted to a fundamental understanding of the fluid dynamic nature of a bubble wake, more specifically the primary wake, in liquids and liquid-solid suspensions, an dto the role it plays in various important flow phenomena of multiphase systems. Examples of these phenomena are liquid/solids mixing, bubble coalescence and disintergration, particle entrainment to the freeboard, and bed contraction.

  12. Fluidised Bed Microencapsulation of Ascorbic Acid: Effectiveness of Protection under Simulated Tropical Storage Conditions

    Science.gov (United States)

    2012-01-01

    ranged from soft to firm finger pressure. The adhesion may be due to the combination of the vacuum packed microcapsules being firmly pressed together...foods. Current Opinion in Biotechnology , 18: 184–190. UNCLASSIFIED DSTO-TR-2789 UNCLASSIFIED 26 Chulia, D. 1994. Powder technology and...alginate–pectin capsules in Cheddar cheese as a food carrier for the delivery of folic acid. LWT, 39:146–151. Marshall, P. A., Trenerry, V. C. and

  13. Experience gained in bench scale and pilot scale fluidised bed processing

    CSIR Research Space (South Africa)

    Hadley, TD

    2005-01-01

    Full Text Available capture to reduce the sulphur dioxide off-gas content. Additionally, work has been conducted on a number of sulphur bearing ores. More recently attention has been placed on the oxidative and reductive roasting of ilmenite to affect the downstream recovery...

  14. Fluidised bed gasification of high-ash South African coals: An experimental and modelling study

    CSIR Research Space (South Africa)

    Engelbrecht, AS

    2011-11-01

    Full Text Available ). Chapter 1. In: Kinetics of Coal Gasification, New York: Wiley. 17 VILIENSKI, T. AND HEZMALIAN, D.M., (1978). Dynamics of the Combustion of Pulverized Fuel. Energia, Moscow, 246p 18 FRANKS, R.G.E., (1967). Mathematical Modelling in Chemical Engineering...

  15. Optimum diameter of a circulating fluidised bed combustor with negative wall heat flux

    CSIR Research Space (South Africa)

    Baloyi, J

    2015-07-01

    Full Text Available process was modelled by a non-premixed combustion model, with a P1 radiation model. Simulations were run using a steady Reynolds averaged Navier Stokes model. The analytical expression predicted the optimum diameter that results in minimum...

  16. Wall heat flux influence on the thermodynamic optimisation of irreversibilities of a circulating fluidised bed combustor

    CSIR Research Space (South Africa)

    Baloyi, J

    2016-07-01

    Full Text Available was varied from a rich to a lean mixture. A non-adiabatic non-premixed combustion model of a numerical code (ANSYS FLUENT 16.2) was used to simulate the combustion process where the solid fuel was modelled by using the ultimate analysis data...

  17. Nitrogen compounds in pressurised fluidised bed gasification of biomass and fossil fuels

    NARCIS (Netherlands)

    De Jong, W.

    2005-01-01

    Fossil fuels still dominate the energy supply in modern societies. The resources, however, are depleting. Therefore, other energy sources are to be exploited further within this century. Biomass is one of the practically CO2 neutral, renewable contributors to the future energy production. Nowadays

  18. Developments in the fluidised bed process for fibre recovery from thermoset composites

    OpenAIRE

    Pickering, S. J.; Turner, T A; Meng, F.; Morris, C.N.; Heil, J.P.; Wong, K H; Melendi-Espina, Sonia

    2015-01-01

    Carbon fibre reinforced plastic (CFRP) is being used in increasing quantities particularly in the transport industry to reduce carbon emissions through weight reduction and in the energy industries for renewable technologies, such as wind turbines. As a high value and energy intensive material to manufacture a good case can be made for recovering and reusing carbon fibre from waste material. A number of companies in Europe and the USA are now in the early stages of commercial operation, but t...

  19. Co-gasification of biomass and coal in a pressurised fluidised bed gasifier

    Energy Technology Data Exchange (ETDEWEB)

    Andries, L.; Hein, K.R.G. [Lab. for Thermal Power Engineering, Dept. of Mechanical Engineering and Marine Technology, Delft Univ. of Technology (Netherlands)

    1996-12-31

    The Laboratory for Thermal Power Engineering of the Delft University of Technology is participating in an EU funded, international, R + D project which is designed to aid European industry in addressing issues regarding co-utilisation of biomass and/or waste in advanced coal conversion processes. The project comprises three main programmes, each of which includes a number of smaller subprogrammes. The three main programmes are: Coal-biomass systems component development and design; Coal-biomass environmental studies; Techno-economic assessment studies. (orig)

  20. 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......, there is evidence of an explosive component in stock market valuation ratios, consistent with a rational bubble........ 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...

  1. Measuring bubbles in a bubbly wake flow

    Science.gov (United States)

    Lee, Seung-Jae; Kawakami, Ellison; Arndt, Roger E. A.

    2012-11-01

    This paper presents measurements of the velocity and size distribution of bubbles in a bubbly wake. This was carried out by utilizing particle shadow velocimetry (PSV). This technique is a non-scattering approach that relies on direct in-line volume illumination by a pulsed source such as a light-emitting diode (LED). A narrow depth-of-field (DoF) is required for imaging a 2-dimensional plane within a flow volume. Shadows of the bubbles were collected by a high-speed camera. Once a reference image, taken when no bubbles were present in the flow, was subtracted from the images, the image was segmented using an edge detection technique. The Canny algorithm was determined to be best suited for this application. A curvature profile method was employed to distinguish individual bubbles within a cluster of highly overlapping bubbles. The utilized algorithm was made to detect partly overlapping bubbles and reconstruct the missing parts. The movement of recognized individual bubbles was tracked on a two dimensional plane within a flow volume. In order to obtain quantitative results, the wake of a ventilated hydrofoil was investigated by applying the shadowgraphy technique and the described bubble detection algorithm. These experiments were carried out in the high speed cavitation tunnel at Saint Anthony Falls Laboratory (SAFL) of the University of Minnesota. This research is jointly sponsored by the Office of Naval Re- search, Dr. Ron Joslin, program manager, and the Department of Energy, Golden Field Office.

  2. Fama on Bubbles

    DEFF Research Database (Denmark)

    Engsted, Tom

    2016-01-01

    . 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......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...

  3. Soap Bubbles and Crystals

    Indian Academy of Sciences (India)

    volume work summarizing his decades of research into soap bubbles and related phe- nomena due to surface tension. He gave the rules governing the geometry of bubbles, without any proof. It is a remarkable achievement as these experiments.

  4. 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)

  5. Economic Growth with Bubbles

    OpenAIRE

    Alberto Martin

    2010-01-01

    This paper presents a stylized model of economic growth with bubbles. This model views asset price bubbles as a market-generated device to moderate the effects of frictions in financial markets, improving the allocation of investments and raising the capital stock and welfare. It shows that, contrary to conventional wisdom, bubbles can arise even if all investments in the economy are dynamically efficient.

  6. Soap Films and Bubbles.

    Science.gov (United States)

    Rice, Karen

    1986-01-01

    Develops and explains a format for a workshop which focuses on soap films and bubbles. The plan consists of: a discussion to uncover what children know about bubbles; explanations of the demonstration equipment; the presentation itself; the assembly of the workshop kit; and time to play with the bubbles. (ML)

  7. Cavitation bubble dynamics.

    Science.gov (United States)

    Lauterborn, W; Ohl, C D

    1997-04-01

    The dynamics of cavitation bubbles on water is investigated for bubbles produced optically and acoustically. Single bubble dynamics is studied with laser produced bubbles and high speed photography with framing rates up to 20.8 million frames per second. Examples for jet formation and shock wave emission are given. Acoustic cavitation is produced in water in the interior of piezoelectric cylinders of different sizes (up to 12 cm inner diameter). The filementary structure composed of bubbles is investigated and their light emission (sonoluminescence) studied for various driving strengths.

  8. An investigation of particle mixing in a gas-fluidized bed

    Science.gov (United States)

    Carlson, R. E.; Gabor, J. D.

    1968-01-01

    Mechanism for particle movement in gas-fluidized beds was studied both from the theoretical and experimental points of view. In a two-dimensional fluidized bed particle trajectories were photographed when a bubble passed through.

  9. Effect of bubble deformability on the vertical channel bubbly flow

    OpenAIRE

    Dabiri, Sadegh; Lu, Jiacai; Tryggvason, Gretar

    2012-01-01

    This article describes the fluid dynamics video: "Effect of bubble deformability on the vertical channel bubbly flow". The effect of bubble deformability on the flow rate of bubbly upflow in a turbulent vertical channel is examined using direct numerical simulations. A series of simulations with bubbles of decreasing deformability reveals a sharp transition from a flow with deformable bubbles uniformly distributed in the middle of the channel to a flow with nearly spherical bubbles with a wal...

  10. Spray-dried fluid-bed sorbents tests - CMP-5

    Energy Technology Data Exchange (ETDEWEB)

    Gangwal, S.K.; Gupta, R.P.

    1995-12-01

    The objective of this study is to determine the feasibility of manufacturing highly reactive and attrition-resistant zinc titanate sorbents by spray drying, suitable for bubbling (conventional) as well as transport-type fluidized-bed reactor systems.

  11. Fluidized bed gasification of selected South African coals

    CSIR Research Space (South Africa)

    Engelbrecht, AD

    2010-05-01

    Full Text Available An investigation was undertaken to ascertain the suitability of four selected low grade, South African coals for gasification in a bubbling fluidized bed for production of synthesis gas and for the development of integrated gasification combined...

  12. Planar Soap Bubbles

    OpenAIRE

    Vaughn, Rick

    1998-01-01

    The generalized soap bubble problem seeks the least perimeter way to enclose and separate n given volumes in R^m. We study the possible configurations for perimeter minimizing bubble complexes enclosing more than two regions. We prove that perimeter minimizing planar bubble complexes with equal pressure regions and without empty chambers must have connected regions. As a consequence, we show that the least perimeter planar graph that...

  13. Magnetic bubble materials.

    Science.gov (United States)

    Giess, E A

    1980-05-23

    Physicists, materials scientists, and engineers combined to bring solid-state bubble devices into the computer memory and recording marketplace. Devices with smaller bubbles are being developed for increased data capacity and lower cost. Epitaxial garnet films made by isothermal dipping in molten solutions helped put the technology in place and will probably satisfy the material needs of future devices with bubbles scaled down from 2 to 0.5 micrometer in size.

  14. 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. Copyright © 2014 Elsevier B.V. All rights reserved.

  15. 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

  16. Ash related bed agglomeration during fluidized bed combustion, further development of the classification method based on CCSEM; CCSEM-luokitusmenetelmaen jatkokehittaeminen tuhkan aiheuttaman agglomeroitumisen tutkimisessa leiju- ja kiertopetipoltossa

    Energy Technology Data Exchange (ETDEWEB)

    Laitinen, R.; Patrikainen, T.; Heikkinen, R.; Tiainen, M.; Virtanen, M. [Oulu Univ. (Finland). Inst. of Chemistry

    1997-10-01

    The scope of this project is to use the information and experience gained from the development of classification method to predict ash related problems like bed agglomeration during fluidised combustion. If boilers have to be shut down due to slagging or agglomeration of the bed material may cause significant economic losses for the entire energy production chain. Mineral classification methods based on the scanning electron microscopy are commonly used for coal ash investigation. In this work different biomass, peat, and peat-wood ash, fluidised-bed materials, and bed agglomerates were analysed with SEM-EDS combined with automatic image analysis software. The properties of ash particles are different depending on the fuel type. If biomass like wood or bark are added to peat the resulting ash has different properties. Due to the low mineral content in the original peat and to the fact that the majority of inorganic material is bound to the organic matrix, the classification has turned out to be less informative than was hoped. However, good results are obtained the by use of quasiternary diagrams. With these diagrams the distribution of particle composition is easily illustrated and thus meaningful prediction can be made of the slagging and agglomerating properties of ash. The content of ten different elements are determined for each particle by SEM-EDS combined with Link AIA software. The composition of the diagram corners can be varied Freely within these ten elements. (orig.)

  17. Bubbles, Banks, and Financial Stability

    OpenAIRE

    Kosuke Aoki; Kalin Nikolov

    2011-01-01

    This paper asks two main questions: (1) What makes some asset price bubbles more costly for the real economy than others? and (2) When do costly bubbles occur? We construct a model of rational bubbles under credit frictions and show that when bubbles held by banks burst this is followed by a costly financial crisis. In contrast, bubbles held by ordinary savers have relatively muted effects. Banks tend to invest in bubbles when financial liberalisation decreases their profitability.

  18. Single bubble sonoluminescence

    NARCIS (Netherlands)

    Brenner, Michael P.; Hilgenfeldt, Sascha; Lohse, Detlef

    2002-01-01

    Single-bubble sonoluminescence occurs when an acoustically trapped and periodically driven gas bubble collapses so strongly that the energy focusing at collapse leads to light emission. Detailed experiments have demonstrated the unique properties of this system: the spectrum of the emitted light

  19. 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...

  20. Understanding the bubbles

    DEFF Research Database (Denmark)

    Turcan, Romeo V.

    that are identified to exist between the Internet and housing market bubbles: uncertainty and sentiments. The iteration between uncertainty and sentiments leads to the emergence of the third commonality: residue. The residue is the difference between the actors’ overall sentiment about exaggerated future prospects......Understanding how and why bubbles occur as well as whether these could be anticipated, managed, or even prevented is equally important as to know how to recover from them. To address these questions, a model of bubble emergence is put forward. The model builds on two fundamental commonalities...... 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 maintained...

  1. CFD-DEM Simulation of Propagation of Sound Waves in Fluid Particles Fluidised Medium

    Directory of Open Access Journals (Sweden)

    H Khawaja

    2016-09-01

    Full Text Available In this work, speed of sound in 2 phase mixture has been explored using CFD-DEM (Computational Fluid Dynamcis - Discrete Element Modelling. In this method volume averaged Navier Stokes, continuity and energy equations are solved for fluid. Particles are simulated as individual entities; their behaviour is captured by Newton's laws of motion and classical contact mechanics. Particle-fluid interaction is captured using drag laws given in literature. The speed of sound in a medium depends on physical properties. It has been found experimentally that speed of sound drops significantly in 2 phase mixture of fluidised particles because of its increased density relative to gas while maintaining its compressibility. Due to the high rate of heat transfer within 2 phase medium as given in Roy et al. (1990, it has been assumed that the fluidised gas-particle medium is isothermal. The similar phenomenon has been tried to be captured using CFD-DEM numerical simulation. The disturbance is introduced and fundamental frequency in the medium is noted to measure the speed of sound for e.g. organ pipe. It has been found that speed of sound is in agreement with the relationship given in Roy et al. (1990. Their assumption that the system is isothermal also appears to be valid.

  2. Oxidative coupling of methane over a La{sub 2}O{sub 3}/CaO catalyst. Optimization of reaction conditions in a bubbling fluidized-bed reactor

    Energy Technology Data Exchange (ETDEWEB)

    Mleczko, L.; Pannek, U.; Rothaemel, M.; Baerns, M. [Bochum Univ. (Germany). Technische Chemie

    1996-04-01

    Oxidative coupling of methane (OCM) over a La{sub 2}O{sub 3}/CaO catalyst was investigated in laboratory-scale fluidized-bed reactors in various ranges of reaction conditions. The catalyst proved to be a very active and selective material for OCM. It was fluidizable in the whole range of operating conditions, and catalytically stable. Axial gas concentration profiles showed that C{sub 2}+ selectivity was not only influenced by oxidative consecutive reactions, but also by steam reforming of ethylene. Two methods for improving C{sub 2}+ selectivity were tested: (1) dilution of the catalytic bed, and (2) operation with lean feed. Dilution of the catalyst led to a slight (1-2%) decrease in selectivity. Dilution of the feed gas with nitrogen resulted in a small improvement (<2%) in C{sub 2}+ selectivity. Although not currently viable economically, given certain changes in the future, this catalyst may find application in OCM, which is the potentially prospective route for the direct conversion of methane. 33 refs., 5 figs.

  3. Bubble impacts with microcantilevers.

    Science.gov (United States)

    Stegmeir, Matthew; Longmire, Ellen; Ali, Mubassar; Mantell, Susan

    2006-11-01

    In the current study, we investigate bubbles in laminar channel flows impacting microcantilever obstacles. Static and resonating cantilevers instrumented with integrated strain gages are mounted perpendicular to the mean flow in a vertically-oriented channel with thickness 2mm, span 10mm, and length 585 mm. Steady, fully-developed upward flows with channel Reynolds numbers based on mean fluid velocity and hydraulic diameter of 0-2500 are considered. Bubbles of diameter 200-1000μm are introduced upstream of the test section, and impacts are observed using a microscope equipped with a high frame rate camera. Observations are made along the length of cantilevers backlit with white light. Strain gage signals are monitored and correlated to impact events. The effect of obstacles on bubble motion and deformation as well as the effect of bubble impacts on the cantilever will be discussed. The flow studies are part of a larger research program examining reliability and performance of vibrating microbeams.

  4. Chemistry in Soap Bubbles.

    Science.gov (United States)

    Lee, Albert W. M.; Wong, A.; Lee, H. W.; Lee, H. Y.; Zhou, Ning-Huai

    2002-01-01

    Describes a laboratory experiment in which common chemical gases are trapped inside soap bubbles. Examines the physical and chemical properties of the gases such as relative density and combustion. (Author/MM)

  5. Bubble dynamics in DNA

    Energy Technology Data Exchange (ETDEWEB)

    Hanke, Andreas [Institut fuer Theoretische Physik, Universitaet Stuttgart, Pfaffenwaldring 57, D-70550 Stuttgart (Germany); Metzler, Ralf [NORDITA-Nordic Institute for Theoretical Physics, Blegdamsvej 17, DK-2100 Copenhagen O (Denmark)

    2003-09-12

    The formation of local denaturation zones (bubbles) in double-stranded DNA is an important example of conformational changes of biological macromolecules. We study the dynamics of bubble formation in terms of a Fokker-Planck equation for the probability density to find a bubble of size n base pairs at time t, on the basis of the free energy in the Poland-Scheraga model. Characteristic bubble closing and opening times can be determined from the corresponding first passage time problem, and are sensitive to the specific parameters entering the model. A multistate unzipping model with constant rates recently applied to DNA breathing dynamics (Altan-Bonnet et al 2003 Phys. Rev. Lett. 90 138101) emerges as a limiting case. (letter to the editor)

  6. Analysis of bubble plume spacing produced by regular breaking waves

    Science.gov (United States)

    Phaksopa, J.; Haller, M. C.

    2012-12-01

    The breaking wave process in the ocean is a significant mechanism for energy dissipation, splash, and entrainment of air. The relationship between breaking waves and bubble plume characteristics is still a mystery because of the complexity of the breaking wave mechanism. This study takes a unique approach to quantitatively analyze bubble plumes produced by regular breaking waves. Various previous studies have investigated the formation and the characteristics of bubble plumes using either field observations, laboratory experiments, or numerical modeling However, in most observational work the plume characteristics have been studied from the underneath the water surface. In addition, though numerical simulations are able to include much of the important physics, the computational costs are high and bubble plume events are only simulated for short times. Hence, bubble plume evolution and generation throughout the surf zone is not yet computationally feasible. In the present work we take a unique approach to analyzing bubble plumes. These data may be of use for model/data comparisons as numerical simulations become more tractable. The remotely sensed video data from freshwater breaking waves in the OSU Large Wave Flume (Catalan and Haller, 2008) are analyzed. The data set contains six different regular wave conditions and the video intensity data are used to estimate the spacing of plume events (wavenumber spectrum), to calculate the spectral width (i.e. the range of plume spacing), and to relate these with the wave conditions. The video intensity data capture the evolution of the wave passage over a fixed bed arranged in a bar-trough morphology. Bright regions represent the moving path or trajectory coincident with bubble plume of each wave. It also shows the bubble foam were generated and released from wave crest shown in the form of bubble tails with almost regular spacing for each wave. The bubble tails show that most bubbles did not move along with wave. For the

  7. 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.

  8. A Bubble Bursts

    Science.gov (United States)

    2005-01-01

    RCW 79 is seen in the southern Milky Way, 17,200 light-years from Earth in the constellation Centaurus. The bubble is 70-light years in diameter, and probably took about one million years to form from the radiation and winds of hot young stars. The balloon of gas and dust is an example of stimulated star formation. Such stars are born when the hot bubble expands into the interstellar gas and dust around it. RCW 79 has spawned at least two groups of new stars along the edge of the large bubble. Some are visible inside the small bubble in the lower left corner. Another group of baby stars appears near the opening at the top. NASA's Spitzer Space Telescope easily detects infrared light from the dust particles in RCW 79. The young stars within RCW 79 radiate ultraviolet light that excites molecules of dust within the bubble. This causes the dust grains to emit infrared light that is detected by Spitzer and seen here as the extended red features.

  9. Artificial neural network models for biomass gasification in fluidized bed gasifiers

    DEFF Research Database (Denmark)

    Puig Arnavat, Maria; Hernández, J. Alfredo; Bruno, Joan Carles

    2013-01-01

    Artificial neural networks (ANNs) have been applied for modeling biomass gasification process in fluidized bed reactors. Two architectures of ANNs models are presented; one for circulating fluidized bed gasifiers (CFB) and the other for bubbling fluidized bed gasifiers (BFB). Both models determine...

  10. Thermodynamic optimisation and computational analysis of irreversibilities in a small-scale wood-fired circulating fluidised bed adiabatic combustor

    CSIR Research Space (South Africa)

    Baloyi, J

    2014-06-01

    Full Text Available An analysis of irreversibilities generated due to combustion in an adiabatic combustor burning wood was conducted. This was done for a reactant mixture varying from a rich to a lean mixture. A non-adiabatic non-premixed combustion model of a...

  11. Fluidised bed membrane reactor for ultrapure hydrogen production via methane steam reforming: Experimental demonstration and model validation

    NARCIS (Netherlands)

    Patil, C.S.; van Sint Annaland, M.; Kuipers, J.A.M.

    2007-01-01

    Hydrogen is emerging as a future alternative for mobile and stationary energy carriers in addition to its use in chemical and petrochemical applications. A novel multifunctional reactor concept has been developed for the production of ultrapure hydrogen View the MathML source from light hydrocarbons

  12. A Three-Dimensional Numerical Study of Gas-Particle Flow and Chemical Reactions in Circulating Fluidised Bed Reactors

    DEFF Research Database (Denmark)

    Hansen, Kim Granly

    of the particulate phase is modeled using the kinetic theory for granular flow, and the gas phase turbulence is modeled using a Sub-Grid-Scale model. A computational study of a cold flowing CFB riser has been performed. The results have been compared to experimental findings of particle volume fraction, particle...... with experimental findings of both mass flux and pressure profile, but further improvements are proposed and investigated. A parameter study shows that mesh refinement, choice of particle diameter and choice of drag model are crucial when simulating FCC riser flow. The isothermal decomposition of ozone has been...... using two-fluid modeling to predict riser flows there have been difficulties in predicting the solids hold up in risers represented by the correct pressure drop profile. Mesh refinement has shown to improve the axial segregation of particles in the riser, but when simulating a riser with a large L...

  13. Optimization of bubble column performance for nanoparticle collection.

    Science.gov (United States)

    Cadavid-Rodriguez, M C; Charvet, A; Bemer, D; Thomas, D

    2014-04-30

    Fibrous media embody the most effective and widely used method of separating ultrafine particles from a carrier fluid. The main problem associated with them is filter clogging, which induces an increasingly marked pressure drop with time and thus imposes regular media cleaning or replacement. This context has prompted the idea of investigating bubble columns, which operate at constant pressure drop, as alternatives to fibrous filters. This study examines the influence of different operating conditions, such as liquid height, air flow rate, bubble size and presence of granular beds on ultrafine particle collection. Experimental results show that bubble columns are characterised by high collection efficiency, when they feature a large liquid height and small diameter bubbling orifices, while their efficiencies remain lower than those of fibrous filters. Gas velocity does not greatly influence collection efficiency, but the inclusion of a granular bed, composed of beads, increases the bubble residence time in the column, thereby increasing the column collection efficiency. Copyright © 2014 Elsevier B.V. All rights reserved.

  14. 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.

  15. Multivariate bubbles and antibubbles

    Science.gov (United States)

    Fry, John

    2014-08-01

    In this paper we develop models for multivariate financial bubbles and antibubbles based on statistical physics. In particular, we extend a rich set of univariate models to higher dimensions. Changes in market regime can be explicitly shown to represent a phase transition from random to deterministic behaviour in prices. Moreover, our multivariate models are able to capture some of the contagious effects that occur during such episodes. We are able to show that declining lending quality helped fuel a bubble in the US stock market prior to 2008. Further, our approach offers interesting insights into the spatial development of UK house prices.

  16. Hydrodynamic studies of the flow of fine particles through a fluidized dense bed of coarse solids

    Energy Technology Data Exchange (ETDEWEB)

    Talukdar, J.

    1993-12-31

    This study explains the hydrodynamics of a circulating fluidized bed (CFB) system, the Battelle Multi-Solids Fluidized Bed System (MSFB). It consists of a circulating fluidized bed of fine particles superimposed on a bubbling bed of coarse solids. One way to characterize such a system is to describe the mechanism of gas-solid flow through the bed. The gas flow in systems like these is through bubbles or slugs (regions of voids containing little or no solids). Bubbles are typically characterized by their size (length or diameter), their rise velocity, and their frequency. Another task of the initial phase of this study is to characterize an L-valve, a solids-recirculating device commonly used in an MSFB. Next, the mechanism of fine particle movement through a bubbling region of coarse fluidized solids is studied in considerable detail. Bubble characteristics are studied in a variety of systems of coarse particles with fines passing through at high velocity. Amongst numerous optical, electrical and other techniques available for the study of the passage of bubbles, the pressure fluctuation technique is the most robust. In this investigation, pressure probes are connected to pressure transducers which are in turn linked to an on-line data acquisition system supported on a microcomputer. A commercially available software package (Notebook) is used to sample pressure at specified points in the fluidized bed at extremely fast rates, of up to 200 Hz. This resulted in pressure-time traces which are analysed to give bubble length, bubble rise velocity, and bubble frequency. Another important objective of this study is to estimate the fine particle residence time in the dense bed section. A defluidization technique is utilized in experimentally measuring the solids holdup in the dense bed. A mathematical model is developed from first principles, based on a momentum balance on the fine particles.

  17. A novel technique for particle tracking in cold 2-dimensional fluidized beds - simulating fuel dispersion

    Energy Technology Data Exchange (ETDEWEB)

    David Pallares; Filip Johnsson [Chalmers University of Technology, Goeteborg (Sweden). Department of Energy and Environment, Energy Conversion

    2006-04-15

    This paper presents a novel technique for particle tracking in 2-dimensional fluidized beds operated under ambient conditions. The method is applied to study the mixing mechanisms of fuel particles in fluidized beds and is based on tracking a phosphorescent tracer particle by means of video recording with subsequent digital image analysis. From this, concentration, velocity and dispersion fields of the tracer particle can be obtained with high accuracy. Although the method is restricted to 2-dimensional, it can be applied under flow conditions qualitatively resembling a fluidized-bed combustor. Thus, the experiments cover ranges of bed heights, gas velocities and fuel-to-bed material density and size ratios typical for fluidized-bed combustors. Also, several fluidization regimes (bubbling, turbulent, circulating and pneumatic) are included in the runs. A pattern found in all runs is that the mixing pattern of the tracer (fuel) solids is structured in horizontally aligned vortexes induced by the bubble flow. The main bubble paths always give a low concentration of tracer solids and with the tracer moving upwards, while the downflow of tracer particles in the dense bottom bed is found to take place in zones with low bubble density and at the sidewalls. The amount of bed material (bed height) has a strong influence on the bottom bed dynamics (development and coalescence of bubbles) and, consequently, on the solids mixing process. Local dispersion coefficients reach maximum values around the locations of bubble eruptions, while, in the presence of a dense bottom bed, an increase in fluidization velocity or amount of bed material enhances dispersion. Dispersion is found to be larger in the vertical than in the horizontal direction, confirming the critical character of lateral fuel dispersion in fluidized-bed combustors of large cross section.

  18. Experimental study on solids circulation patterns and bubble behavior using particle imagevelocimetry combined with digital image analysis

    NARCIS (Netherlands)

    Laverman, J.A.; Roghair, Ivo; van Sint Annaland, M.; Kuipers, J.A.M.

    2008-01-01

    The hydrodynamics, viz. the solids circulation patterns and bubble behavior, of a freely bubbling gas-solid fluidized bed has been investigated experimentally using Particle Image Velocimetry (PIV) combined with Digital Image Analysis (DIA). Coupling of these non-invasive measuring techniques allows

  19. Interpretation of CT-Scan Sinograms to Study the Dynamic Flow Properties of a Fluidized Bed

    Science.gov (United States)

    Bennett, M. A.; Kryuchkov, S.; Kantzas, A.

    2007-06-01

    Fast moving objects typically produce poor quality images and motion-artifacts in Computed Tomography (CT) scans. The imaging of bubbling gas-solid fluidized beds, where many bubbles may pass through the sensing cross-section in a tomographic measurement, gives such a problem. Previously, one method of dealing with this problem was to remove artifacts from the reconstructed image itself through low pass filtering. However, this method leads to lost information from the images. When the concentration of bubbles is low, and their shape is close to cylindrically symmetric, analysis of consecutive scans in the raw data sinogram can also provide valuable information about the frequency of bubbles passing, and about their individual size, shape and position. Then, utilizing the inverse Abel transform, this information can then also be used to contribute to time averaged properties of the bed's behaviour such as voidage distribution, bubble phase area fraction and spatial bubble number distribution.

  20. The Liberal Arts Bubble

    Science.gov (United States)

    Agresto, John

    2011-01-01

    The author expresses his doubt that the general higher education bubble will burst anytime soon. Although tuition, student housing, and book costs have all increased substantially, he believes it is still likely that the federal government will continue to pour billions into higher education, largely because Americans have been persuaded that it…

  1. BEBC bubble chamber

    CERN Multimedia

    CERN PhotoLab

    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.

  2. 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.

  3. Heavy liquid bubble chamber

    CERN Multimedia

    CERN PhotoLab

    1965-01-01

    The CERN Heavy liquid bubble chamber being installed in the north experimental hall at the PS. On the left, the 1180 litre body; in the centre the magnet, which can produce a field of 26 800 gauss; on the right the expansion mechanism.

  4. Bubble properties of heterogeneous bubbly flow in a square bubble column

    NARCIS (Netherlands)

    Bai, W.; Deen, N.G.; Kuipers, J.A.M.

    2010-01-01

    The present work focuses on the measurements of bubble properties in heterogeneous bubbly flows in a square bubble column. A four-point optical fibre probe was used for this purpose. The accuracy and intrusive effect of the optical probe was investigated first. The results show that the optical

  5. Characteristics of bubble plumes, bubble-plume bubbles and waves from wind-steepened wave breaking

    NARCIS (Netherlands)

    Leifer, I.; Caulliez, G.; Leeuw, G. de

    2007-01-01

    Observations of breaking waves, associated bubble plumes and bubble-plume size distributions were used to explore the coupled evolution of wave-breaking, wave properties and bubble-plume characteristics. Experiments were made in a large, freshwater, wind-wave channel with mechanical wind-steepened

  6. Bubbling controlled by needle movement

    Energy Technology Data Exchange (ETDEWEB)

    Vejrazka, Jiri; Fujasova, Maria; Stanovsky, Petr; Ruzicka, Marek C; Drahos, JirI [Institute of Chemical Process Fundamentals, Academy of Sciences of the Czech Republic, Rozvojova 135, 165 02 Prague (Czech Republic)], E-mail: vejrazka@icpf.cas.cz

    2008-07-30

    A device for 'on-demand' production of bubbles is presented. The device is based on a movable needle, through which air is injected. Bubbling is controlled by a rapid needle movement, which induces the bubble detachment. Conditions for proper function of the device include the restriction on the flow rate through the needle, sufficient needle pressure drop and adequate needle acceleration. Functionality of the device is demonstrated. Bubbling from a stationary needle is also discussed and a scaling for bubble size is proposed for the case of short needles, to which a constant flow rate is imposed through tubes of a finite volume.

  7. 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...

  8. Ring Bubbles of Dolphins

    Science.gov (United States)

    Shariff, Karim; Marten, Ken; Psarakos, Suchi; White, Don J.; Merriam, Marshal (Technical Monitor)

    1996-01-01

    The article discusses how dolphins create and play with three types of air-filled vortices. The underlying physics is discussed. Photographs and sketches illustrating the dolphin's actions and physics are presented. The dolphins engage in this behavior on their own initiative without food reward. These behaviors are done repeatedly and with singleminded effort. The first type is the ejection of bubbles which, after some practice on the part of the dolphin, turn into toroidal vortex ring bubbles by the mechanism of baroclinic torque. These bubbles grow in radius and become thinner as they rise vertically to the surface. One dolphin would blow two in succession and guide them to fuse into one. Physicists call this a vortex reconnection. In the second type, the dolphins first create an invisible vortex ring in the water by swimming on their side and waving their tail fin (also called flukes) vigorously. This vortex ring travels horizontally in the water. The dolphin then turns around, finds the vortex and injects a stream of air into it from its blowhole. The air "fills-out" the core of the vortex ring. Often, the dolphin would knock-off a smaller ring bubble from the larger ring (this also involves vortex reconnection) and steer the smaller ring around the tank. One other dolphin employed a few other techniques for planting air into the fluke vortex. One technique included standing vertically in the water with tail-up, head-down and tail piercing the free surface. As the fluke is waved to create the vortex ring, air is entrained from above the surface. Another technique was gulping air in the mouth, diving down, releasing air bubbles from the mouth and curling them into a ring when they rose to the level of the fluke. In the third type, demonstrated by only one dolphin, the longitudinal vortex created by the dorsal fin on the back is used to produce 10-15 foot long helical bubbles. In one technique she swims in a curved path. This creates a dorsal fin vortex since

  9. Bubble dynamics in drinks

    Directory of Open Access Journals (Sweden)

    Broučková Zuzana

    2014-03-01

    Full Text Available This study introduces two physical effects known from beverages: the effect of sinking bubbles and the hot chocolate sound effect. The paper presents two simple „kitchen” experiments. The first and second effects are indicated by means of a flow visualization and microphone measurement, respectively. To quantify the second (acoustic effect, sound records are analyzed using time-frequency signal processing, and the obtained power spectra and spectrograms are discussed.

  10. Quantum Subcritical Bubbles

    Science.gov (United States)

    Uesugi, T.; Morikawa, M.; Shiromizu, T.

    1996-08-01

    We quantize subcritical bubbles which are formed in the weakly first order phase transition. We find that the typical size of the thermal fluctuation reduces in quantum-statistical physics. We estimate the typical size and the amplitude of thermal fluctuations near the critical temperature in the electroweak phase transition using a quantum statistical average. Furthermore, based on our study, we discuss implications for the dynamics of phase transitions.

  11. Popping the filter bubble

    OpenAIRE

    Hughes, Katie; Cronin, G; Welch, L

    2017-01-01

    So-called “fake news” is everywhere and is having a major impact on daily life from politics to education. The rapid growth of information and the numbers of people who can create it means that we need more sophisticated tools to process the news we receive. Join us to learn about different methods you can use to be your own fact checker and pop your filter bubble.

  12. BubbleDeck

    OpenAIRE

    ECT Team, Purdue

    2013-01-01

    Conventional horizontal concrete slabs are heavy that limit their spans. Enhancement of span results in addition of beams that increases the cost of the structure. Thus, there is a need for a technology that will help in increasing the span by reducing weight of the span. BubbleDeck is a revolutionary construction method that virtually eliminates concrete from the middle of a floor slab between columns that does not perform any structural function, thereby dramatically reducing structural dea...

  13. The ash chemistry in fluidized bed gasification of biomass fuels. Part 1: predicting the chemistry of melting ashes and ash-bed material interaction

    Energy Technology Data Exchange (ETDEWEB)

    Zevenhoven-Onderwater, M.; Backman, R.; Skrifvars, B.-J.; Hupa, M. [Aabo Akademi University, Turku (Finland). Dept. of Chemical Engineering, Combustion Chemistry Research Group

    2001-08-10

    This paper describes the modelling of the ash-chemistry of seven biomass fuels under reducing, pressurised conditions in fluidised bed gasification by means of thermodynamic multi-phase multi-component equilibrium (TPCE) calculations. The fuels considered were Salix, a Scandinavian forest residue, Miscanthus, Reed Canary Grass, Eucalyptus, Arundo Donax and Lucerne. The composition and amount of phases have been calculated for the gasification of the fuel as such and in presence of an excess amount of calcite, dolomite, magnesium olivine sand and sand by using TPCE calculations in a temperature interval of 600-900{degree}C and a pressure of 10 bar. It was found that interaction of inorganic compounds released from the fuels with bed material is a prerequisite for the formation of bed agglomerates. The presence of an excess of dolomite decreased the amount of alkali components in the bed, thereby increasing the amount of alkali components volatilised. A silica bed, however, binds most alkali released from the fuel, retaining it in the bed as low melting alkali silicates. The chances of experiencing operating problems due to bed agglomeration may increase hereby significantly. Calculations at atmospheric pressure show that the amounts of melt present will be smaller when compared to pressurised conditions, thereby decreasing the chances of bed agglomeration. In a pressurised gasifier using calcite or dolomite as bed material a small amount of an alkali carbonate rich melt can be expected at temperatures above 620{degree}C with each of the seven biomass fuels fired. In silica-rich cases melt can be expected at temperatures above 770{degree}C. The amount of melt is rather high. In the case of a magnesium olivine sand bed an alkali melt can be expected at 620{degree}C. At temperatures above 800{degree}C, a silicate melt can form as well. The amount of melt was high showing a significant contribution of the bed material. 39 refs., 15 figs., 2 tabs.

  14. Atmospheric and pressurized fluidized bed technology

    Energy Technology Data Exchange (ETDEWEB)

    Anthony, E.J.B. [Natural Resources Canada, Ottawa, ON (Canada). CANMET Energy Technology Centre

    2003-07-01

    Fluidization states, bubbling and circulating fluidized beds, and the basics of pressurized fluidized bed combustion are outlined. PFBC demonstration plants, cogeneration, operational units and possible new plants, growth of PFBC capacity, sulphur capture, sulphation, phase composition of ashes, and actual performance in reduction of sulphur dioxide and nitrogen oxides are described. Problems occurring during operation show that turbines need to be protected and that hot gas filters degrade and are unreliable. It is concluded that the future of PFBC depends on Asian development and that the technology may be stimulated by stricter pollution controls. 5 figs., 4 tabs.

  15. Lits fluidisés pour l'industrie chimique. Extrapolation et amélioration des catalyseurs. Première partie : Etudes et modèles. Enseignements issus des pilotes Fluidized Beds in Chemical Industry. Scale Up and Catalysts Improvement. First Part: Studies, Models, Learning from Pilot Plants

    Directory of Open Access Journals (Sweden)

    Botton R.

    2006-12-01

    est intitulée Études théoriques, réalités expérimentales, suggestions . Les bulles des lits fluidisés ont fait l'objet de très nombreux travaux, dont les résultats sont très souvent explicités sous la forme de modèles mécanistiques à un paramètre qui est le diamètre des bulles. Pour confronter ces modèles à l'expérience, une relation est établie entre le diamètre des bulles et la vitesse minimum de fluidisation de comportement. Des suggestions sont alors faites pour améliorer les modèles, et l'on propose des conclusions générales sur les lits fluidisés. The firsts catalytic fluidized beds appear near 1942 in petroleum industry and near 1960 in chemical industry. We only consider very high performances chemical fluidized bed reactors (> 99%. In the past, they were developed through the use of very expensive pilot plants of about 0. 5 m diameter and 10 in high. We will demonstrate that direct scale up from laboratory data is possible. This possibility gives also a simple method to improve catalysts used into operating units and opens fluidized bed technique to products that need only low production. Presentation is made with three articles:- In the first, Studies, Models, Learning from Pilot Plants : after a description of the major scale-up problems, studies to solve then are summarized. Then scale-up works of two processes with the use of about 0. 5 m diameter pilot plant are given. From the results it is deduced the possible performances of a catalytic fluidized bed and how to operate to obtain then. - In the second*, Scale up with Only Laboratory Data , it is experimentally demonstrated that the information's scale-up can be obtained in a laboratory. A strategy to obtain them is suggested. An another result of theses experimental studies is that all physical properties of catalytic fluidized bed depends of only one parameter. It is called comportment incipient fluidization velocity . - In the third*, Theoretical Studies, Experimental

  16. 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...... 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 the sources of bubble...

  17. Capacitor model to interpret the electric behavior of fluidized beds. Influence of apparatus geometry

    Energy Technology Data Exchange (ETDEWEB)

    Rojo, V.; Guardiola, J.; Vian, A.

    1986-01-01

    This work provides a model to know the degree of electrification in fluidized beds on the basis of voltage measurements between an electric probe and a metallic distributor. The model is based on the similarity of behavior between the probe-bed-distributor system and a capacitor. The influence of three variables related to apparatus geometry - height of probe, column diameter and height of bed - has been studied in an air fluidized bed of glass beads. The results show that the degree of bed electrification is not influenced by the column diameter; the effect of bed height depends on the quality of fluidization: with a bubbling bed the degree of electrification increases with bed height whereas the opposite effect is observed with a slugging bed. Additional fixed bed experiments make clear that the rate of charge dissipation grows for increasing values of bed height and column diameter, and for decreasing values of probe height.

  18. In Search of the Big Bubble

    Science.gov (United States)

    Simoson, Andrew; Wentzky, Bethany

    2011-01-01

    Freely rising air bubbles in water sometimes assume the shape of a spherical cap, a shape also known as the "big bubble". Is it possible to find some objective function involving a combination of a bubble's attributes for which the big bubble is the optimal shape? Following the basic idea of the definite integral, we define a bubble's surface as…

  19. On the Influence of Particle Entrainment from an Inhomogeneous Fluidized Bed on the Hydrodynamics of the Vortex Over-Bed Zone

    Science.gov (United States)

    Pitsukha, E. A.; Teplitskii, Yu. S.

    2017-01-01

    Experimental investigation of the radial distributions of tangential air velocity and total pressure in the vortex overbed zone of a fluidized bed of diameter 0.393 m has been carried out. The influence of the entrainment of particles from the bed in the exhaust trails of gas bubbles on the maximum values of tangential velocity and total pressure has been established.

  20. Bubble measuring instrument and method

    Science.gov (United States)

    Kline-Schoder, Robert (Inventor); Magari, Patrick J. (Inventor)

    2003-01-01

    Method and apparatus are provided for a non-invasive bubble measuring instrument operable for detecting, distinguishing, and counting gaseous embolisms such as bubbles over a selectable range of bubble sizes of interest. A selected measurement volume in which bubbles may be detected is insonified by two distinct frequencies from a pump transducer and an image transducer, respectively. The image transducer frequency is much higher than the pump transducer frequency. The relatively low-frequency pump signal is used to excite bubbles to resonate at a frequency related to their diameter. The image transducer is operated in a pulse-echo mode at a controllable repetition rate that transmits bursts of high-frequency ultrasonic signal to the measurement volume in which bubbles may be detected and then receives the echo. From the echo or received signal, a beat signal related to the repetition rate may be extracted and used to indicate the presence or absence of a resonant bubble. In a preferred embodiment, software control maintains the beat signal at a preselected frequency while varying the pump transducer frequency to excite bubbles of different diameters to resonate depending on the range of bubble diameters selected for investigation.

  1. Electroweak bubble wall speed limit

    Science.gov (United States)

    Bödeker, Dietrich; Moore, Guy D.

    2017-05-01

    In extensions of the Standard Model with extra scalars, the electroweak phase transition can be very strong, and the bubble walls can be highly relativistic. We revisit our previous argument that electroweak bubble walls can "run away," that is, achieve extreme ultrarelativistic velocities γ ~ 1014. We show that, when particles cross the bubble wall, they can emit transition radiation. Wall-frame soft processes, though suppressed by a power of the coupling α, have a significance enhanced by the γ-factor of the wall, limiting wall velocities to γ ~ 1/α. Though the bubble walls can move at almost the speed of light, they carry an infinitesimal share of the plasma's energy.

  2. 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.

  3. Co-combustion of automotive shredder residue (ASR) and sewage sludge with a mixture of industrial and household waste in an 20MW fluidized bed combustor; Samfoerbraenning av bilfluff, roetslam och avfall i en 20 MW fluidbaeddpanna - Studier av braenslesammansaettningens paaverkan paa belaeggningsbildning

    Energy Technology Data Exchange (ETDEWEB)

    Eskilsson, David; Johansson, Andreas; Johansson, Linda; Wikstroem-Blomqvist, Evalena

    2007-07-01

    In order to prevent a further increased use of resources and to decrease the environmental impact from landfills, organic wastes are today diverted towards material and energy recovery. This creates a waste market with an increasing number of waste fractions that needs to be treated properly. As an example, in Sweden it has recently been prohibited to landfill source separated combustible waste (2002) and organic waste (2005). Wastes as automotive shredder residue (ASR) and sewage sludge can no longer be landfilled and needs to be either material or energy recovered, which challenge the waste treatment sector. This work investigates the effects of ASR and sewage sludge co-combustion in a 20 MW Energy-from-Waste plant (bubbling fluidised bed). The long term objective of the work is to increase the fuel flexibility, the boiler availability and the power production. This report focus on boiler operation and combustion performance in terms of agglomeration, deposit rates and emissions. In addition to the tests with ASR and sewage sludge, repeated measurements were performed during normal load as a reference. The results show that the co-combusted fractions of ASR and sewage sludge, which on mass basis constituted 6 % and 15 % respectively, did not increase the risk for agglomeration or deposits on heat-exchanging surfaces. Instead, compared to the two reference cases, the deposit rates decreased when sewage sludge was added. Only minor variation in the emissions was seen between the different cases. The levels of I-TEQs were far below the legislated values in all cases

  4. Na emission and bubble instability in single-bubble sonoluminescence.

    Science.gov (United States)

    Choi, Pak-Kon; Takumori, Keisuke; Lee, Hyang-Bok

    2017-09-01

    Na emission in single-bubble sonoluminescence (SBSL) was observed from 0.1mM sodium dodecyl sulfate (SDS) solution containing a dissolved noble gas at a low acoustic pressure, at which a continuous spectral component was negligible. High-speed shadowgraph movies were captured at a frame rate of 30,000fps, which indicated that bubble dancing is responsible for the Na emission. The measured bubble path length was well correlated with the Na intensity. The disintegration of a daughter bubble followed by immediate coalescence was frequently observed, which may have been the cause of the bubble dancing. A comparison of the Na spectra obtained in SBSL and multibubble SL showed that the conditions under which Na emission is generated are twofold. A narrow component was observed in the Na spectrum in SBSL, while narrow and broad components were observed in MBSL. Copyright © 2017 Elsevier B.V. All rights reserved.

  5. Sonoporation from jetting cavitation bubbles

    NARCIS (Netherlands)

    Ohl, C.D.; Arora, M.; Ikink, Roy; de Jong, N.; Versluis, Michel; Delius, Michael; Lohse, Detlef

    2006-01-01

    The fluid dynamic interaction of cavitation bubbles with adherent cells on a substrate is experimentally investigated. We find that the nonspherical collapse of bubbles near to the boundary is responsible for cell detachment. High-speed photography reveals that a wall bounded flow leads to the

  6. Sonoporation from jetting cavitation bubbles

    NARCIS (Netherlands)

    C.-D. Ohl (Claus-Dieter); M. Arora (Manish); R. Ikink (Roy); N. de Jong (Nico); M. Versluis (Michel); M. Delius (Michael); D. Lohse (Detlef)

    2006-01-01

    textabstractThe fluid dynamic interaction of cavitation bubbles with adherent cells on a substrate is experimentally investigated. We find that the nonspherical collapse of bubbles near to the boundary is responsible for cell detachment. High-speed photography reveals that a wall bounded flow leads

  7. Bubble size distribution of foam

    NARCIS (Netherlands)

    den Engelsen, C.W.; den Engelsen, C.W.; Isarin, J.C.; Warmoeskerken, Marinus; Groot Wassink, J.; Groot Wassink, J.

    2002-01-01

    A procedure based upon image analysis has been adopted to study the influence of several physical parameters on bubble size in foam. A procedure has been described to account for the distribution of bubble size. Foam was generated in a rotor-stator mixer. In the present research, the nature of the

  8. Hadron bubbles in nuclear matter

    Energy Technology Data Exchange (ETDEWEB)

    Troitskii, M.A.; Khodel' , V.A.

    1983-08-25

    Nonlinear effects in the interaction of hadrons with a nucleus are analyzed. It is shown that K/sup +/ mesons form bubbles in nuclear matter which are similar to electron bubbles in liquid helium. Charged pions produced in collisions of heavy relativistic ions may collect and form droplets approx.5--7 Fm in size containing approx.10/sup 2/ particles.

  9. Mr. Bubble Gum: "Not Now!"

    National Research Council Canada - National Science Library

    1989-01-01

    PreS-Gr 2-- Mr. Bubble Gum is a Level 3 book, the most difficult in this series. In four short stories of varying lengths, an older brother tells about his younger brother Eli, who "sticks to me like bubble gum...

  10. 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.

  11. Bubble columns : Structures or stability?

    NARCIS (Netherlands)

    Harteveld, W.K.

    2005-01-01

    The aim of the thesis is to contribute to the understanding of the hydrodynamics of the gravity driven bubbly flow that can be found in bubble columns. Special attention is paid to the large scale structures that have a strong impact on several key parameters such as the degree of mixing, mass and

  12. Phase diagrams for sonoluminescing bubbles

    NARCIS (Netherlands)

    Hilgenfeldt, Sascha; Lohse, Detlef; Brenner, Michael P.

    1996-01-01

    Sound driven gas bubbles in water can emit light pulses. This phenomenon is called sonoluminescence (SL). Two different phases of single bubble SL have been proposed: diffusively stable and diffusively unstable SL. We present phase diagrams in the gas concentration versus forcing pressure state

  13. Bubble coalescence in breathing DNA

    DEFF Research Database (Denmark)

    Novotný, Tomas; Pedersen, Jonas Nyvold; Ambjörnsson, Tobias

    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...

  14. Growing bubbles rising in line

    Directory of Open Access Journals (Sweden)

    John F. Harper

    2001-01-01

    Full Text Available Over many years the author and others have given theories for bubbles rising in line in a liquid. Theory has usually suggested that the bubbles will tend towards a stable distance apart, but experiments have often showed them pairing off and sometimes coalescing. However, existing theory seems not to deal adequately with the case of bubbles growing as they rise, which they do if the liquid is boiling, or is a supersaturated solution of a gas, or simply because the pressure decreases with height. That omission is now addressed, for spherical bubbles rising at high Reynolds numbers. As the flow is then nearly irrotational, Lagrange's equations can be used with Rayleigh's dissipation function. The theory also works for bubbles shrinking as they rise because they dissolve.

  15. Scaling of pressurized fluidized beds

    Energy Technology Data Exchange (ETDEWEB)

    Guralnik, S.; Glicksman, L.R.

    1994-10-01

    The project has two primary objectives. The first is to verify a set of hydrodynamic scaling relationships for commercial pressurized fluidized bed combustors (PFBC). The second objective is to investigate solids mixing in pressurized bubbling fluidized beds. American Electric Power`s (AEP) Tidd combined-cycle demonstration plant will provide time-varying pressure drop data to serve as the basis for the scaling verification. The verification will involve demonstrating that a properly scaled cold model and the Tidd PFBC exhibit hydrodynamically similar behavior. An important issue in PFBC design is the spacing of fuel feed ports. The feed spacing is dictated by the fuel distribution and the mixing characteristics within the bed. After completing the scaling verification, the cold model will be used to study the characteristics of PFBCs. A thermal tracer technique will be utilized to study mixing both near the fuel feed region and in the far field. The results allow the coal feed and distributor to be designed for optimal heating.

  16. Foam preparation at high-throughput using a novel packed bed system

    NARCIS (Netherlands)

    Nazir, A.; Maan, A.A.; Sahin, S.; Boom, R.M.; Schroën, C.G.P.H.

    2015-01-01

    We investigated the formation of food foams using a novel packed bed system at different operating pressures.The foaming process was based on simultaneous injection of continuous (whey protein solution) and dispersed(nitrogen gas) phases into a column containing a packed bed of glass beads. Bubbles

  17. Effects and control of humidity and particle mixing in fluid-bed granulation

    NARCIS (Netherlands)

    Schaafsma, SH; Kossen, NWF; Mos, MT; Blauw, L; Hoffmann, AC

    The novel technique of spraying binder liquid in pulses of short duration on a bubbling fluidized bed was used to study the effect liquid distribution, mixing, and relative humidity has on granule growth. Two important mixing zones in the fluid-bed granulation process are identified. First, the

  18. The bubble legacy

    Science.gov (United States)

    Hecht, Jeff

    2010-05-01

    Imagine an optics company - let's call it JDS Uniphase - with a market capitalization approaching the gross domestic product (GDP) of Ireland. Now imagine it merging with a laser company - say, SDL - that has a stock valuation of 41bn, higher than the GDP of Costa Rica. Finally, imagine a start-up with 109m in venture capital in its pocket but no product to its name (Novalux) turning down an offer of 500m as insufficient. It may be hard to believe, but these tales are true: they occurred in the year 2000 - an era when the laser, fibre-optics and photonics industries were the darlings of the financial world. Such was the madcap nature of that brief period that survivors call it simply "the bubble".

  19. Particle pressures in fluidized beds. Second year annual report

    Energy Technology Data Exchange (ETDEWEB)

    Campbell, C.S.; Rahman, K.; Hu, X.; Jin, C.

    1993-12-31

    Campbell and Wang (1991) showed that the particle pressures in gas-fluidized beds were largely generated by the passage of bubbles. In particular, they showed that the average particle pressure exerted on the side walls scaled with the average size of the bubble. This immediately brings to mind two questions: (1) what is it about bubbles that leads to particle pressure generation and (2) would there be measurable particle pressures in liquid-fluidized beds which, while unstable, do not bubble? This project is largely aimed at answering these two questions. To attack the first problem, the authors have built a two-dimensional gas-fluidized bed into which bubbles may be injected and the distribution of particle-pressure measured. For the latter, other experiments are being performed in liquid fluidized beds. However, it soon became apparent that the particle pressures generated in the liquid beds are extremely small. This has pointed that phase of the research in two directions. The first is the design and construction of a third, and more sensitive, from of the particle pressure transducer. The second approach arose from reflection on what ultimately was the utility of the current research. This led to the development of a generic stability model, in which all modeled terms are left unspecified. From analyzing this model, they have developed an experimental plan that, by measuring the characteristics of voidage disturbances and comparing with the theory, will allow them to back out appropriate values for the modeled terms. The results will not only yield insight into the particle pressure, but also of the fluid drag. The latter results may be used to evaluate common models for these terms.

  20. Bubble size distribution and inner surface in a bubble flow

    Science.gov (United States)

    Žitek, P.; Valenta, V.

    2017-09-01

    This paper follows the reports [4] and gives instructions on how to theoretically determine the bubble size and its distribution using the distribution function of Nukiyama-Tanasawa with friction factors.

  1. 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

  2. Partial coalescence of soap bubbles

    Science.gov (United States)

    Harris, Daniel M.; Pucci, Giuseppe; Bush, John W. M.

    2015-11-01

    We present the results of an experimental investigation of the merger of a soap bubble with a planar soap film. When gently deposited onto a horizontal film, a bubble may interact with the underlying film in such a way as to decrease in size, leaving behind a smaller daughter bubble with approximately half the radius of its progenitor. The process repeats up to three times, with each partial coalescence event occurring over a time scale comparable to the inertial-capillary time. Our results are compared to the recent numerical simulations of Martin and Blanchette and to the coalescence cascade of droplets on a fluid bath.

  3. Bubble stimulation efficiency of dinoflagellate bioluminescence.

    Science.gov (United States)

    Deane, Grant B; Stokes, M Dale; Latz, Michael I

    2016-02-01

    Dinoflagellate bioluminescence, a common source of bioluminescence in coastal waters, is stimulated by flow agitation. Although bubbles are anecdotally known to be stimulatory, the process has never been experimentally investigated. This study quantified the flash response of the bioluminescent dinoflagellate Lingulodinium polyedrum to stimulation by bubbles rising through still seawater. Cells were stimulated by isolated bubbles of 0.3-3 mm radii rising at their terminal velocity, and also by bubble clouds containing bubbles of 0.06-10 mm radii for different air flow rates. Stimulation efficiency, the proportion of cells producing a flash within the volume of water swept out by a rising bubble, decreased with decreasing bubble radius for radii less than approximately 1 mm. Bubbles smaller than a critical radius in the range 0.275-0.325 mm did not stimulate a flash response. The fraction of cells stimulated by bubble clouds was proportional to the volume of air in the bubble cloud, with lower stimulation levels observed for clouds with smaller bubbles. An empirical model for bubble cloud stimulation based on the isolated bubble observations successfully reproduced the observed stimulation by bubble clouds for low air flow rates. High air flow rates stimulated more light emission than expected, presumably because of additional fluid shear stress associated with collective buoyancy effects generated by the high air fraction bubble cloud. These results are relevant to bioluminescence stimulation by bubbles in two-phase flows, such as in ship wakes, breaking waves, and sparged bioreactors. Copyright © 2015 John Wiley & Sons, Ltd.

  4. New evidence on the first financial bubble

    NARCIS (Netherlands)

    Frehen, R.G.P.; Goetzmann, W.; Rouwenhorst, K.G.

    2013-01-01

    The Mississippi Bubble, South Sea Bubble and the Dutch Windhandel of 1720 together represent the world's first global financial bubble. We hand-collect cross-sectional price data and investor account data from 1720 to test theories about market bubbles. Our tests suggest that innovation was a key

  5. Aspherical bubble dynamics and oscillation times

    Energy Technology Data Exchange (ETDEWEB)

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

    1999-06-01

    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 by time-resolved photography and numerical simulations. The growth-collapse period of cylindrical bubbles of large aspect ratio (length:diameter {approximately}20) differs only slightly 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 size and energy even for aspherical bubbles. The change of the oscillation period of bubbles near solid walls and elastic (tissue-like) boundaries relative to that of isolated spherical bubbles is also investigated.

  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. Magnetism. Blowing magnetic skyrmion bubbles.

    Science.gov (United States)

    Jiang, Wanjun; Upadhyaya, Pramey; Zhang, Wei; Yu, Guoqiang; Jungfleisch, M Benjamin; Fradin, Frank Y; Pearson, John E; Tserkovnyak, Yaroslav; Wang, Kang L; Heinonen, Olle; te Velthuis, Suzanne G E; Hoffmann, Axel

    2015-07-17

    The formation of soap bubbles from thin films is accompanied by topological transitions. Here we show how a magnetic topological structure, a skyrmion bubble, can be generated in a solid-state system in a similar manner. Using an inhomogeneous in-plane current in a system with broken inversion symmetry, we experimentally "blow" magnetic skyrmion bubbles from a geometrical constriction. The presence of a spatially divergent spin-orbit torque gives rise to instabilities of the magnetic domain structures that are reminiscent of Rayleigh-Plateau instabilities in fluid flows. We determine a phase diagram for skyrmion formation and reveal the efficient manipulation of these dynamically created skyrmions, including depinning and motion. The demonstrated current-driven transformation from stripe domains to magnetic skyrmion bubbles could lead to progress in skyrmion-based spintronics. Copyright © 2015, American Association for the Advancement of Science.

  8. Microstreaming from Sessile Semicylindrical Bubbles

    Science.gov (United States)

    Hilgenfeldt, Sascha; Rallabandi, Bhargav; Guo, Lin; Wang, Cheng

    2014-03-01

    Powerful steady streaming flows result from the ultrasonic driving of microbubbles, in particular when these bubbles have semicylindrical cross section and are positioned in contact with a microfluidic channel wall. We have used this streaming in experiment to develop novel methods for trapping and sorting of microparticles by size, as well as for micromixing. Theoretically, we arrive at an analytical description of the streaming flow field through an asymptotic computation that, for the first time, reconciles the boundary layers around the bubble and along the substrate wall, and also takes into account the oscillation modes of the bubble. This approach gives insight into changes in the streaming pattern with bubble size and driving frequency, including a reversal of the flow direction at high frequencies with potentially useful applications. Present address: Mechanical and Aerospace Engineering, Missouri S &T.

  9. Experimental Investigation of Radial Gas Dispersion Coefficients in a Fluidized Bed

    Directory of Open Access Journals (Sweden)

    Jiří Štefanica

    2012-01-01

    Full Text Available In a fluidized bed boiler, the combustion efficiency, the NOX formation rate, flue gas desulphurization and fluidized bed heat transfer are all ruled by the gas distribution. In this investigation, the tracer gas method is used for evaluating the radial gas dispersion coefficient. CO2 is used as a tracer gas, and the experiment is carried out in a bubbling fluidized bed cold model. Ceramic balls are used as the bed material. The effect of gas velocity, radial position and bed height is investigated.

  10. 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=L(3)/6π(2), and this is indeed the case of a free soap bubble, for instance. Surprisingly, we show that for Vbubble 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<αL(3)/6π(2) cannot be stable and should not exist in foams, for instance.

  11. Bubbles and foams in microfluidics.

    Science.gov (United States)

    Huerre, Axel; Miralles, Vincent; Jullien, Marie-Caroline

    2014-09-28

    Microfluidics offers great tools to produce highly-controlled dispersions of gas into liquid, from isolated bubbles to organized microfoams. Potential technological applications are manifold, from novel materials to scaffolds for tissue engineering or enhanced oil recovery. More fundamentally, microfluidics makes it possible to investigate the physics of complex systems such as foams at scales where the capillary forces become dominant, in model experiments involving few well-controlled parameters. In this context, this review does not have the ambition to detail in a comprehensive manner all the techniques and applications involving bubbles and foams in microfluidics. Rather, it focuses on particular consequences of working at the microscale, under confinement, and hopes to provide insight into the physics of such systems. The first part of this work focuses on bubbles, and more precisely on (i) bubble generation, where the confinement can suppress capillary instabilities while inertial effects may play a role, and (ii) bubble dynamics, paying special attention to the lubrication film between bubble and wall and the influence of confinement. The second part addresses the formation and dynamics of microfoams, emphasizing structural differences from macroscopic foams and the influence of the confinement.

  12. From rational bubbles to crashes

    Science.gov (United States)

    Sornette, D.; Malevergne, Y.

    2001-10-01

    We study and generalize in various ways the model of rational expectation (RE) bubbles introduced by Blanchard and Watson in the economic literature. Bubbles are argued to be the equivalent of Goldstone modes of the fundamental rational pricing equation, associated with the symmetry-breaking introduced by non-vanishing dividends. Generalizing bubbles in terms of multiplicative stochastic maps, we summarize the result of Lux and Sornette that the no-arbitrage condition imposes that the tail of the return distribution is hyperbolic with an exponent μbubble model to arbitrary dimensions d: a number d of market time series are made linearly interdependent via d× d stochastic coupling coefficients. We derive the no-arbitrage condition in this context and, with the renewal theory for products of random matrices applied to stochastic recurrence equations, we extend the theorem of Lux and Sornette to demonstrate that the tails of the unconditional distributions associated with such d-dimensional bubble processes follow power laws, with the same asymptotic tail exponent μmodel and the non-stationary growth rate model) of the RE bubble model that provide two ways of reconciliation with the stylized facts of financial data.

  13. Measuring online social bubbles

    Directory of Open Access Journals (Sweden)

    Dimitar Nikolov

    2015-12-01

    Full Text Available Social media have become a prevalent channel to access information, spread ideas, and influence opinions. However, it has been suggested that social and algorithmic filtering may cause exposure to less diverse points of view. Here we quantitatively measure this kind of social bias at the collective level by mining a massive datasets of web clicks. Our analysis shows that collectively, people access information from a significantly narrower spectrum of sources through social media and email, compared to a search baseline. The significance of this finding for individual exposure is revealed by investigating the relationship between the diversity of information sources experienced by users at both the collective and individual levels in two datasets where individual users can be analyzed—Twitter posts and search logs. There is a strong correlation between collective and individual diversity, supporting the notion that when we use social media we find ourselves inside “social bubbles.” Our results could lead to a deeper understanding of how technology biases our exposure to new information.

  14. 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

  15. CFD study of a fluidized bed

    OpenAIRE

    Lundberg, Joachim

    2008-01-01

    The aim of this thesis is to investigate the momentum exchange between the phases in a bubbling fluidized bed. The momentum exchange can be described by a drag model. Several drag models with different assumptions are developed. The drag models investigated in this work is the Syamlal O’Brien model, the Gidaspow model, Hill Koch Ladd model, the RUC model and an iterative version of the Syamlal O’Brien called the Richardson Zaki model. The models have been derived and studied in detail. S...

  16. BUBBLE FORMATION EXPERIMENTS IN SNOW DENSIFICATION

    OpenAIRE

    イシイ, セイゴ; ナリタ, ヒデキ; マエノ, ノリカズ; Seigo, ISHII; Hideki, NARITA; Norikazu, MAENO

    1995-01-01

    Bubble formation experiments were conducted for snow composed of ice spheres 303μm in diameter at various temperatures and applied pressures. By measuring volumes of closed-off bubbles at various densities, the bubble formation density (ρ_f) and the bubble close-off density (ρ_c) were obtained. ρ_f, that is the density at which bubble formation begins, decreased with lowering temperature or pressure. On the other hand, ρ_c, that is the density at which bubble formation finishes, increased wit...

  17. Spherical Solutions of an Underwater Explosion Bubble

    Directory of Open Access Journals (Sweden)

    Andrew B. Wardlaw

    1998-01-01

    Full Text Available The evolution of the 1D explosion bubble flow field out to the first bubble minimum is examined in detail using four different models. The most detailed is based on the Euler equations and accounts for the internal bubble fluid motion, while the simplest links a potential water solution to a stationary, Isentropic bubble model. Comparison of the different models with experimental data provides insight into the influence of compressibility and internal bubble dynamics on the behavior of the explosion bubble.

  18. On the Inception of Financial Representative Bubbles

    Directory of Open Access Journals (Sweden)

    Massimiliano Ferrara

    2017-11-01

    Full Text Available In this work, we aim to formalize the inception of representative bubbles giving the condition under which they may arise. We will find that representative bubbles may start at any time, depending on the definition of a behavioral component. This result is at odds with the theory of classic rational bubbles, which are those models that rely on the fulfillment of the transversality condition by which a bubble in a financial asset can arise just at its first trade. This means that a classic rational bubble (differently from our model cannot follow a cycle since if a bubble exists, it will burst by definition and never arise again.

  19. Bubble rearrangements dynamics in foams

    Science.gov (United States)

    Le Merrer, Marie; Costa, Severine; Cohen-Addad, Sylvie; Hoehler, Reinhard

    2011-11-01

    Liquid foams are jammed dispersions of gas bubbles in a surfactant solution. Their structure evolves with time because surface tension drives a diffusive gas exchange between neighboring bubbles. This coarsening leads to a build-up of stresses which are relaxed upon local intermittent bubble rearrangements. These events govern the slow viscoelastic foam response, and similar bubble rearrangements are the elementary processes of plastic flow. Thus, the rearrangement duration is a key parameter describing how the microstructure dynamics control the macroscopic rheological response. We probe the duration of coarsening-induced rearrangements in 3D foams using a multiple light scattering technique (time resolved Diffusing-Wave Spectroscopy) as a function of the surfactant chemistry and the liquid fraction. As the foam becomes wetter, the confinement pressure of the packing goes to zero and the contacts between bubbles vanish. For mobile interfaces, we find that the rearrangements slow down as the jamming point is approached. These findings are compared to scaling laws which reveal an analogy between rearrangements dynamics in foams and granular suspensions.

  20. Ethnic diversity deflates price bubbles

    Science.gov (United States)

    Levine, Sheen S.; Apfelbaum, Evan P.; Bernard, Mark; Bartelt, Valerie L.; Zajac, Edward J.; Stark, David

    2014-01-01

    Markets are central to modern society, so their failures can be devastating. Here, we examine a prominent failure: price bubbles. Bubbles emerge when traders err collectively in pricing, causing misfit between market prices and the true values of assets. The causes of such collective errors remain elusive. We propose that bubbles are affected by ethnic homogeneity in the market and can be thwarted by diversity. In homogenous markets, traders place undue confidence in the decisions of others. Less likely to scrutinize others’ decisions, traders are more likely to accept prices that deviate from true values. To test this, we constructed experimental markets in Southeast Asia and North America, where participants traded stocks to earn money. We randomly assigned participants to ethnically homogeneous or diverse markets. We find a marked difference: Across markets and locations, market prices fit true values 58% better in diverse markets. The effect is similar across sites, despite sizeable differences in culture and ethnic composition. Specifically, in homogenous markets, overpricing is higher as traders are more likely to accept speculative prices. Their pricing errors are more correlated than in diverse markets. In addition, when bubbles burst, homogenous markets crash more severely. The findings suggest that price bubbles arise not only from individual errors or financial conditions, but also from the social context of decision making. The evidence may inform public discussion on ethnic diversity: it may be beneficial not only for providing variety in perspectives and skills, but also because diversity facilitates friction that enhances deliberation and upends conformity. PMID:25404313

  1. Ethnic diversity deflates price bubbles.

    Science.gov (United States)

    Levine, Sheen S; Apfelbaum, Evan P; Bernard, Mark; Bartelt, Valerie L; Zajac, Edward J; Stark, David

    2014-12-30

    Markets are central to modern society, so their failures can be devastating. Here, we examine a prominent failure: price bubbles. Bubbles emerge when traders err collectively in pricing, causing misfit between market prices and the true values of assets. The causes of such collective errors remain elusive. We propose that bubbles are affected by ethnic homogeneity in the market and can be thwarted by diversity. In homogenous markets, traders place undue confidence in the decisions of others. Less likely to scrutinize others' decisions, traders are more likely to accept prices that deviate from true values. To test this, we constructed experimental markets in Southeast Asia and North America, where participants traded stocks to earn money. We randomly assigned participants to ethnically homogeneous or diverse markets. We find a marked difference: Across markets and locations, market prices fit true values 58% better in diverse markets. The effect is similar across sites, despite sizeable differences in culture and ethnic composition. Specifically, in homogenous markets, overpricing is higher as traders are more likely to accept speculative prices. Their pricing errors are more correlated than in diverse markets. In addition, when bubbles burst, homogenous markets crash more severely. The findings suggest that price bubbles arise not only from individual errors or financial conditions, but also from the social context of decision making. The evidence may inform public discussion on ethnic diversity: it may be beneficial not only for providing variety in perspectives and skills, but also because diversity facilitates friction that enhances deliberation and upends conformity.

  2. 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.

  3. Modeling an oil shale fluid bed combustor

    Energy Technology Data Exchange (ETDEWEB)

    Vasalos, I.A.; Lefkopoulos, A.; Georgiadou, M.

    1988-02-01

    Oil shale retorting involves heating of solid particles and pyrolysis of the organic matter to produce hydrocarbon liquid shale oil. During the pyrolysis process, part of the organic material remains in the inorganic matrix as coke residue. Combustion of the coke residue can provide the energy necessary for retorting. In this paper the use of a fluid bed combustor to burn the coke residue is examined. The basis for predicting the performance of the fluid bed combustor is the application of the two-phase theory of fluidization. The carbon burning efficiency was calculated as a function of temperature, pressure, and bubble size. For the same conditions, the carbonate decomposition and the associated energy loss were also established. Conditions were found which make feasible complete carbon combustion with minimum carbonate decomposition.

  4. Modeling an oil shale fluid bed combustor

    Energy Technology Data Exchange (ETDEWEB)

    Vasalos, I.A.; Lefkopoulos, A.; Georgiadou, M.

    1985-01-01

    Oil shale retorting involves heating of solid particles and pyrolysis of the organic matter to produce hydrocarbon liquid--shale oil. During the pyrolysis process part of the organic material remains in the inorganic matrix as coke residue. Combustion of the coke residue can provide the energy necessary for retorting. In this paper the use of a fluid bed combustor to burn the coke residue is examined. The basis for predicting the performance of the fluid bed combustor is the application of the two-phase theory of fluidization. The carbon burning efficiency was calculated as a function of temperature, pressure, and bubble size. For the same conditions the carbonate decomposition and the associated energy loss was also established.

  5. Soap Bubbles on a Cold Day.

    Science.gov (United States)

    Waiveris, Charles

    1994-01-01

    Discusses the effects of blowing bubbles in extremely cold weather. Describes the freezing conditions of the bubbles and some physical properties. Suggests using the activity with all ages of students. (MVL)

  6. Unorthodox bubbles when boiling in cold water

    Science.gov (United States)

    Parker, Scott; Granick, Steve

    2014-01-01

    High-speed movies are taken when bubbles grow at gold surfaces heated spotwise with a near-infrared laser beam heating water below the boiling point (60-70 °C) with heating powers spanning the range from very low to so high that water fails to rewet the surface after bubbles detach. Roughly half the bubbles are conventional: They grow symmetrically through evaporation until buoyancy lifts them away. Others have unorthodox shapes and appear to contribute disproportionately to heat transfer efficiency: mushroom cloud shapes, violently explosive bubbles, and cavitation events, probably stimulated by a combination of superheating, convection, turbulence, and surface dewetting during the initial bubble growth. Moreover, bubbles often follow one another in complex sequences, often beginning with an unorthodox bubble that stirs the water, followed by several conventional bubbles. This large dataset is analyzed and discussed with emphasis on how explosive phenomena such as cavitation induce discrepancies from classical expectations about boiling.

  7. 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

  8. Bubble nucleation in an explosive micro-bubble actuator

    NARCIS (Netherlands)

    van den Broek, D.M.; Elwenspoek, Michael Curt

    2008-01-01

    Explosive evaporation occurs when a thin layer of liquid reaches a temperature close to the critical temperature in a very short time. At these temperatures spontaneous nucleation takes place. The nucleated bubbles instantly coalesce forming a vapour film followed by rapid growth due to the pressure

  9. Does monetary policy generate asset price bubbles ?

    OpenAIRE

    Blot, Christophe; Hubert, Paul; Labondance, Fabien

    2017-01-01

    This paper empirically assesses the effect of monetary policy on asset price bubbles and aims to disentangle the competing predictions of theoretical bubble models. First, we take advantage of the model averaging feature of Principal Component Analysis to estimate bubble indicators, for the stock, bond and housing markets in the United States and Euro area, based on the structural, econometric and statistical approaches proposed in the literature to measure bubbles. Second, we ...

  10. Behavior of a Large Bubble in a Horizontal Channel : 2nd Report, Large Bubble Penetrating into Running Liquid

    OpenAIRE

    坂口, 忠司; 小澤, 守; 浜口, 八朗; 福永, 毅

    1990-01-01

    The behavior of a large bubble penetrating into running liquid in a horizontal pipe has been studied experimentally. The flow regime of the large bubble is classified into the following three regimes : a steadily moving bubble regime, a transition regime and a stationary bubble regime. In the steadily moving bubble regime, the large bubble penetrates at constant velocity and the shape of the bubble nose does not change along the pipe. An analysis of the behavior of the large bubble has been c...

  11. Vapor Bubbles in Flow and Acoustic Fields

    NARCIS (Netherlands)

    Prosperetti, Andrea; Hao, Yue; Sadhal, S.S

    2002-01-01

    A review of several aspects of the interaction of bubbles with acoustic and flow fields is presented. The focus of the paper is on bubbles in hot liquids, in which the bubble contains mostly vapor, with little or no permanent gas. The topics covered include the effect of translation on condensation

  12. Bubble Size Distributions in Coastal Seas

    NARCIS (Netherlands)

    Leeuw, G. de; Cohen, L.H.

    1995-01-01

    Bubble size distributions have been measured with an optical system that is based on imaging of a small sample volume with a CCD camera system, and processing of the images to obtain the size of individual bubbles in the diameter range from 30 to lOOO^m. This bubble measuring system is deployed from

  13. Mechanics of gas-vapor bubbles

    NARCIS (Netherlands)

    Hao, Yue; Zhang, Yuhang; Prosperetti, Andrea

    2017-01-01

    Most bubbles contain a mixture of vapor and incondensible gases. While the limit cases of pure vapor and pure gas bubbles are well studied, much less is known about the more realistic case of a mixture. The bubble contents continuously change due to the combined effects of evaporation and

  14. 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.

  15. Low-grade coal and biomass co-combustion on fluidized bed: exergy analysis

    Energy Technology Data Exchange (ETDEWEB)

    Martin, C.; Villamanan, M.A.; Chamorro, C.R.; Segovia, J.J. [University of Valladolid (Spain). Dept. of Energy; Otero, J.; Cabanillas, A. [Environment and Technology Ciemat, Madrid (Spain). Dept. of Fossil Fuels

    2006-03-01

    The purpose of this work is to prove the technical feasibility of the bubbling fluidized bed co-combustion, using biomass and low-grade coal mixtures and applying the exergy method. The pilot plant modelled is an atmospheric bubbling fluidized bed combustion chamber with a nominal capacity of 1 MWth. We have applied the mass balance, the energy balance and the exergy balance to the plant in nine experiments, which have been performed at different operation conditions. The exergy analysis includes the calculation of the exergy destruction and the exergetic efficiency of the plant for these experiments. An estimation of the irreversibility cost is also evaluated. (author)

  16. Introduction to Bed Bugs

    Science.gov (United States)

    ... Agency Search Search Bed Bugs Contact Us Share Introduction to Bed Bugs Photo credit: CDC/ CDC-DPDx; ... and Guidance Regulations About EPA EPA Administrator Current Leadership Organization Chart Staff Directory Planning, Budget and Results ...

  17. Practice Hospital Bed Safety

    Science.gov (United States)

    ... Updates Practice Hospital Bed Safety Share Tweet Linkedin Pin it More sharing options Linkedin Pin it Email Print Hospital Bed Entrapment Zones An ... the side edge of the head or foot board 7. between the head or foot board and ...

  18. Affirmative Discrimination and the Bubble

    Science.gov (United States)

    Clegg, Roger

    2011-01-01

    In this essay, the author discusses how affirmative action contributed to an unnatural rise in enrollments in college. In considering the higher education bubble, he makes the case that as the opposition to preferences continues to build, the momentum of this trend will only increase as funding shrinks. He offers some tentative answers to a series…

  19. The Coming Law School Bubble

    Science.gov (United States)

    Krauss, Michael I.

    2011-01-01

    In this article, the author explains how forty years of politicized hiring in the law schools has left its destructive mark. The results are potentially catastrophic: Market forces and internal law school policies may be combining to produce a legal education bubble the likes of which the country has never seen. (Contains 11 footnotes.)

  20. Models of cylindrical bubble pulsation

    Science.gov (United States)

    Ilinskii, Yurii A.; Zabolotskaya, Evgenia A.; Hay, Todd A.; Hamilton, Mark F.

    2012-01-01

    Three models are considered for describing the dynamics of a pulsating cylindrical bubble. A linear solution is derived for a cylindrical bubble in an infinite compressible liquid. The solution accounts for losses due to viscosity, heat conduction, and acoustic radiation. It reveals that radiation is the dominant loss mechanism, and that it is 22 times greater than for a spherical bubble of the same radius. The predicted resonance frequency provides a basis of comparison for limiting forms of other models. The second model considered is a commonly used equation in Rayleigh-Plesset form that requires an incompressible liquid to be finite in extent in order for bubble pulsation to occur. The radial extent of the liquid becomes a fitting parameter, and it is found that considerably different values of the parameter are required for modeling inertial motion versus acoustical oscillations. The third model was developed by V. K. Kedrinskii [Hydrodynamics of Explosion (Springer, New York, 2005), pp. 23–26] in the form of the Gilmore equation for compressible liquids of infinite extent. While the correct resonance frequency and loss factor are not recovered from this model in the linear approximation, it provides reasonable agreement with observations of inertial motion. PMID:22978863

  1. The Big European Bubble Chamber

    CERN Multimedia

    1977-01-01

    The 3.70 metre Big European Bubble Chamber (BEBC), dismantled on 9 August 1984. During operation it was one of the biggest detectors in the world, producing direct visual recordings of particle tracks. 6.3 million photos of interactions were taken with the chamber in the course of its existence.

  2. Explosive micro-bubble actuator

    NARCIS (Netherlands)

    van den Broek, D.M.; Elwenspoek, Michael Curt

    2007-01-01

    Explosive evaporation occurs when a thin layer of liquid reaches a very high temperature in a very short time. At these temperatures homogeneous nucleation takes place. The nucleated bubbles almost instantly coalesce forming a vapour film followed by rapid growth due to the pressure impulse and

  3. Droplets, Bubbles and Ultrasound Interactions

    NARCIS (Netherlands)

    Shpak, O.; Verweij, M.; de Jong, N.; Versluis, Michel; Escoffre, J.M.; Bouakaz, A.

    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

  4. Electrolysis Bubbles Make Waterflow Visible

    Science.gov (United States)

    Schultz, Donald F.

    1990-01-01

    Technique for visualization of three-dimensional flow uses tiny tracer bubbles of hydrogen and oxygen made by electrolysis of water. Strobe-light photography used to capture flow patterns, yielding permanent record that is measured to obtain velocities of particles. Used to measure simulated mixing turbulence in proposed gas-turbine combustor and also used in other water-table flow tests.

  5. 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.

  6. "Financial Bubbles" and Monetary Policy

    Science.gov (United States)

    Tikhonov, Yuriy A.; Pudovkina, Olga E.; Permjakova, Juliana V.

    2016-01-01

    The relevance of this research is caused by the need of strengthening a role of monetary regulators to prevent financial bubbles in the financial markets. The aim of the article is the analysis of a problem of crisis phenomena in the markets of financial assets owing to an inadequate growth of their cost, owing to subjective reasons. The leading…

  7. Turbulence, aeration and bubble features of air-water flows in macro- and intermediate roughness conditions

    Directory of Open Access Journals (Sweden)

    Stefano Pagliara

    2011-06-01

    Full Text Available Free surface flows in macro- and intermediate roughness conditions have a high aeration potential causing the flow characteristics to vary with slopes and discharges. The underlying mechanism of two-phase flow characteristics in macro- and intermediate roughness conditions were analyzed in an experimental setup assembled at the Laboratory of Hydraulic Protection of the Territory (PITLAB of the University of Pisa, Italy. Crushed angular rocks and hemispherical boulders were used to intensify the roughness of the bed. Flow rates per unit width ranging between 0.03 m2/s and 0.09 m2/s and slopes between 0.26 and 0.46 were tested over different arrangements of a rough bed. Analyses were mainly carried out in the inner flow region, which consists of both bubbly and intermediate flow regions. The findings revealed that the two-phase flow properties over the rough bed were much affected by rough bed arrangements. Turbulence features of two-phase flows over the rough bed were compared with those of the stepped chute data under similar flow conditions. Overall, the results highlight the flow features in the inner layers of the two-phase flow, showing that the maximum turbulence intensity decreases with the relative submergence, while the bubble frequency distribution is affected by the rough bed elements.

  8. Developments in fluidized bed conversion of solid fuels

    Directory of Open Access Journals (Sweden)

    Leckner Bo

    2016-01-01

    Full Text Available A summary is given on the development of fluidized bed conversion (combustion and gasification of solid fuels. First, gasification is mentioned, following the line of development from the Winkler gasifier to recent designs. The combustors were initially bubbling beds, which were found unsuitable for combustion of coal because of various drawbacks, but they proved more useful for biomass where these drawbacks were absent. Instead, circulating fluidized bed boilers became the most important coal converters, whose design now is quite mature, and presently the increments in size and efficiency are the most important development tasks. The new modifications of these conversion devices are related to CO2 capture. Proposed methods with this purpose, involving fluidized bed, are single-reactor systems like oxy-fuel combustion, and dual-reactor systems, including also indirect biomass gasifiers.

  9. Studies on thermoelectric power generation consuming municipal solid waste (MSW) and using bubbling fluidized bed gasifier : Estudos em geração termelétrica a partir de resíduos sólidos urbanos (RSU) utilizando gaseificadores de leito fluidizado borbulhante

    OpenAIRE

    Andres Felipe Rodriguez Torres

    2016-01-01

    Resumo: O presente trabalho introduz novos desenvolvimentos da estratégia no conceito Fuel-Slurry Integrated Gasifier/Gas Turbine para a geração de potência termoelétrica aplicada ao caso de Resíduos Sólidos Urbanos (RSU). O processo FSIG/GT permite a alimentação do combustível num gaseificador pressurizado utilizando bombas de lama disponíveis no mercado, evitando a necessidade de sistemas de silos em cascata. O gaseificador opera em regime de Leito Fluidizado Borbulhante (Bubbling Fluidized...

  10. Bubble bouncing at a clean water surface.

    Science.gov (United States)

    Zawala, Jan; Dorbolo, Stéphane; Vandewalle, Nicolas; Malysa, Kazimierz

    2013-10-28

    Experiments on the coalescence time of submillimeter bubbles colliding with a distilled water/air interface either being at rest (undisturbed) or vibrating vertically (with controlled amplitude and frequency) were carried out. It was found that the outcome of the bubble collision (coalescence or bounce) depends on impact velocity and size of the bubble, i.e. the parameters determining the bubble deformation degree. With the surface at rest, when the deformation of the bubble was sufficiently high, bubble bouncing was observed. It was caused by the fact that the radius of the intervening liquid film formed between the colliding bubble and water/air interface was large enough to prevent the liquid layer from reaching its thickness of rupture within the time of bubble-interface contact. Coalescence occurred in a consecutive collision if the bubble deformation was below a threshold value, as a result of dissipation of the kinetic energy associated with the bubble motion. The hypothesis about the crucial role of the bubble deformation and size of the liquid film formed in the bouncing mechanism was confirmed in a series of experiments where the bubble collided with a vibrating water/air interface. It was shown that when the kinetic energy was properly re-supplied from an external source (interface vibrations), the spectacular phenomenon of "immortal" bubbles, dancing indefinitely at the water/air interface, was achieved. It was shown that "immortal" bubble formation is a consequence of a similarly high degree of the bubble shape deformation and consequently a large enough radius of the liquid film formed.

  11. Robust acoustic wave manipulation of bubbly liquids

    Energy Technology Data Exchange (ETDEWEB)

    Gumerov, N. A., E-mail: gumerov@umiacs.umd.edu [Institute for Advanced Computer Studies, University of Maryland, College Park, Maryland 20742 (United States); Center for Micro- and Nanoscale Dynamics of Dispersed Systems, Bashkir State University, Ufa 450076 (Russian Federation); Akhatov, I. S. [Center for Design, Manufacturing and Materials, Skolkovo Institute of Science and Technology, Moscow 143026 (Russian Federation); Ohl, C.-D. [Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371 (Singapore); Center for Micro- and Nanoscale Dynamics of Dispersed Systems, Bashkir State University, Ufa 450076 (Russian Federation); Sametov, S. P. [Center for Micro- and Nanoscale Dynamics of Dispersed Systems, Bashkir State University, Ufa 450076 (Russian Federation); Khazimullin, M. V. [Center for Micro- and Nanoscale Dynamics of Dispersed Systems, Bashkir State University, Ufa 450076 (Russian Federation); Institute of Molecule and Crystal Physics, Ufa Research Center of Russian Academy of Sciences, Ufa 450054 (Russian Federation); Gonzalez-Avila, S. R. [Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371 (Singapore)

    2016-03-28

    Experiments with water–air bubbly liquids when exposed to acoustic fields of frequency ∼100 kHz and intensity below the cavitation threshold demonstrate that bubbles ∼30 μm in diameter can be “pushed” away from acoustic sources by acoustic radiation independently from the direction of gravity. This manifests formation and propagation of acoustically induced transparency waves (waves of the bubble volume fraction). In fact, this is a collective effect of bubbles, which can be described by a mathematical model of bubble self-organization in acoustic fields that matches well with our experiments.

  12. Bubbles generated from wind-steepened breaking waves: 2. Bubble plumes, bubbles, and wave characteristics

    NARCIS (Netherlands)

    Leifer, I.; Caulliez, G.; Leeuw, G.de

    2006-01-01

    Measurements of breaking-wave-generated bubble plumes were made in fresh (but not clean) water in a large wind-wave tunnel. To preserve diversity, a classification scheme was developed on the basis of plume dimensions and "optical density," or the plume's ability to obscure the background. Optically

  13. Simulations of Rising Hydrodynamic and Magnetohydrodynamic Bubbles

    Science.gov (United States)

    Ricker, P. M.; Robinson, K.; Dursi, L. J.; Rosner, R.; Calder, A. C.; Zingale, M.; Truran, J. W.; Linde, T.; Caceres, A.; Fryxell, B.; Olson, K.; Riley, K.; Siegel, A.; Vladimirova, N.

    Motivated by recent Chandra and XMM-Newton observations of X-ray emission voids in galaxy cluster cooling flows, we have investigated the behavior of rising bubbles in stratified atmospheres using the FLASH adaptive-mesh simulation code. We present results from two-dimensional simulations with and without the effects of magnetic fields, and with varying bubble sizes and background stratifications. We find purely hydrodynamic bubbles to be unstable; a dynamically important magnetic field is required to maintain a bubble's integrity. This suggests that, even absent thermal conduction, for bubbles to be persistent enough to be regularly observed, they must be supported in large part by magnetic fields. We also observe that magnetically supported bubbles leave a tail as they rise. The structure of these tails may provide clues to the bubble's dynamical history.

  14. Tests with blast furnace slag as bed material in a 12 MW waste fired BFB boiler; Fullskalefoersoek med Hyttsand som baeddmaterial i 12 MW avfallseldad BFB-panna

    Energy Technology Data Exchange (ETDEWEB)

    Eklund, Anders; Oehman, Marcus

    2004-11-01

    A full-scale trial has been performed at Saeverstaverket twin 12 MWth BFB boilers in Bollnaes using Hyttsand (a proprietary blast furnace slag) as bed material. The purpose has been to investigate if Hyttsand can be used as bed material in FB boilers for difficult types of fuels. Used fuel has been municipal waste, recovered wood fuel and different types of bio fuels. The test period was 19 days and nearly 100 tons of Hyttsand was used. The most important conclusions are: Good fluidisation can be achieved with Hyttsand as bed material. Hyttsand can fluidise without any changes in boiler settings. Hyttsand can also be mixed with Baskarpsand (a natural sand with over 90% SiO{sub 2}) and used as bed material without any negative changes to the boiler performance. Bed material make-up rate is reduced with up to 30 % when using Hyttsand compared to using Baskarpsand. Other conclusions are: Bed temperature increased slightly and bed temperature deviation decreased. Emissions was in general not affected, however emissions of SO{sub 2} increased slightly. More deposit containing more sulphur was formed on superheater surfaces when using Hyttsand. The increased amount of sulphur when using Hyttsand could be an effect of higher content of sulphur in the fuel or, which is more likely, that sulphur is released from Hyttsand and forms gaseous sulphurous gases. No significant change in produced amounts of fly-, cyclone- or bottom ash. Hyttsand and Baskarpsand had both similar coatings on their particles and similar agglomeration tendencies. There have been some start-up problems during the trials, including two more severe boiler disturbances, but most of these disturbances can be explained and avoided in the future. Previous investigations in laboratory scale using Hyttsand as bed material when firing different bio fuels have shown the advantage of Hyttsand with its higher resistance against a chemical reaction with alkali in the fuel ash compared to conventional bed materials

  15. Double bubble with the big-bubble technique during deep anterior lamellar keratoplasty.

    Science.gov (United States)

    Wise, Stephanie; Dubord, Paul; Yeung, Sonia N

    2017-04-28

    To report a case of intraoperative double bubble that formed during big-bubble DALK surgery in a patient with corneal scarring secondary to herpetic stromal keratitis. Case report. A 22 year old woman presented with a large corneal scar, likely secondary to previous herpetic stromal keratitis. She underwent big-bubble DALK surgery for visual rehabilitation. Intraoperatively, a mixed bubble with persistent type 2 bubble postoperatively was noted. The second bubble resorbed with clearance of the graft and good visual outcome after 6 weeks. This case report describes the unusual development of a mixed bubble during big-bubble DALK surgery. This graft cleared with resolution of the second bubble postoperatively without further surgical intervention.

  16. Collaborative Strategy on Bed Bugs

    Science.gov (United States)

    The Collaborative Strategy on Bed Bugs was developed by the Federal Bed Bug Workgroup to clarify the federal role in bed bug control and highlight ways that government, community, academia and private industry can work together on bed bug issues.

  17. Application of Defocusing Technique to Bubble Depth Measurement

    OpenAIRE

    Mugikura, Yuki

    2017-01-01

    The thesis presents a defocusing technique to extract bubble depth information. Typically, when a bubble is out of focus in an image, the bubble is ignored by applying a filter or thresholding. However, it is known that a bubble image becomes blurred as the bubble moves away from the focal plane. Then, this technique is applied to determine the bubble distance along the optical path based on the blurriness or intensity gradient information of the bubble. Using the image processing algorithm, ...

  18. Cavitation inception from bubble nuclei

    DEFF Research Database (Denmark)

    Mørch, Knud Aage

    2015-01-01

    . 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......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...

  19. 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...

  20. 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.

  1. Soap bubbles in paintings: Art and science

    Science.gov (United States)

    Behroozi, F.

    2008-12-01

    Soap bubbles became popular in 17th century paintings and prints primarily as a metaphor for the impermanence and fragility of life. The Dancing Couple (1663) by the Dutch painter Jan Steen is a good example which, among many other symbols, shows a young boy blowing soap bubbles. In the 18th century the French painter Jean-Simeon Chardin used soap bubbles not only as metaphor but also to express a sense of play and wonder. In his most famous painting, Soap Bubbles (1733/1734) a translucent and quavering soap bubble takes center stage. Chardin's contemporary Charles Van Loo painted his Soap Bubbles (1764) after seeing Chardin's work. In both paintings the soap bubbles have a hint of color and show two bright reflection spots. We discuss the physics involved and explain how keenly the painters have observed the interaction of light and soap bubbles. We show that the two reflection spots on the soap bubbles are images of the light source, one real and one virtual, formed by the curved surface of the bubble. The faint colors are due to thin film interference effects.

  2. Informational pathologies and interest bubbles

    DEFF Research Database (Denmark)

    Hendricks, Vincent Fella; Wiewiura, Joachim Schmidt

    2017-01-01

    This article contends that certain configurations of information networks facilitate specific cognitive states that are instrumental for decision and action on social media. Group-related knowledge and belief states—in particular common knowledge and pluralistic ignorance—may enable strong public...... signals. Indeed, some network configurations and attitude states foster informational pathologies that may fuel interest bubbles affecting agenda-setting and the generation of narratives in public spheres....

  3. BEBC Big European Bubble Chamber

    CERN Multimedia

    CERN PhotoLab

    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.

  4. Bubble-induced cave collapse.

    Science.gov (United States)

    Girihagama, Lakshika; Nof, Doron; Hancock, Cathrine

    2015-01-01

    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.

  5. Bubble capture by a propeller

    Science.gov (United States)

    Caillé, François; Clanet, Christophe; Magnaudet, Jacques

    2006-08-01

    A small air bubble (radius a) is injected in water (kinematic viscosity nu) in the vicinity (distance r_0) of a propeller (radius r_p, angular frequency omega). We study experimentally and theoretically the conditions under which the bubble can be ‘captured’, i.e. deviated from its vertical trajectory (imposed by gravity g) and moved toward the centre of the propeller (r {=} 0). We show that the capture frequency omega_{scriptsizecapt} follows the relationship [omega_{hboxriptsizeit capt}=left(frac{2ga^2}{9betanu r_p f(hboxRe_b)}right)left(frac{r_0}{r_p}right)^2(1+\\cos\\varphi_0),] where beta is a dimensionless parameter characterizing the propeller, f(Re_b) is an empirical correction to Stokes' drag law which accounts for finite-Reynolds-number effects and pi/2-varphi_0 is the angle between the axis of the propeller and the line between the centre of the propeller and the point where the bubble is injected. This law is found to be valid as long as the distance d between the propeller and the water surface is larger than 3r_0. For smaller distances, the capture frequency increases; using an image technique, we show how the above expression is modified by the presence of the surface.

  6. Interaction of positive streamers in air with bubbles floating on liquid surfaces: conductive and dielectric bubbles

    Science.gov (United States)

    Babaeva, Natalia Yu; Naidis, George V.; Kushner, Mark J.

    2018-01-01

    The interaction of plasmas sustained in humid air with liquids produces reactive species in both the gas phase and liquid for applications ranging from medicine to agriculture. In several experiments, enhanced liquid reactivity has been produced when the liquid is a foam or a bubble coated liquid. To investigate the phenomena of streamers interacting with bubbles a two-dimensional computational investigation has been performed of streamer initiation and propagation on and inside hemispherical bubble-shells floating on a liquid surface. Following prior experiments, water and oil bubble-shells with an electrode located outside and inside the bubble were investigated. We found that positive air streamers interact differently with conductive water and dielectric oil bubbles. The streamer propagates along the external surface of a water bubble while not penetrating through the bubble due to screening of the electric field by the conducting shell. If the electrode is inserted inside the bubble, the path of the streamer depends on how deeply the electrode penetrates. For shallow penetration, the streamer propagates along the inner surface of the bubble. Due to the low conductivity of oil bubble-shells, the electric field from an external electrode penetrates into the interior of the bubble. The streamer can then be re-initiated inside the bubble.

  7. Materials problems in fluidized-bed combustion systems. Appendix 2. Test specimen preparation, handling, and posttest evaluation. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Rogers, E.A.; Holder, J.C.; Minchener, A.J.; Page, A.J.; La Nauze, R.D.

    1980-05-01

    Appendix 2 presents the metallographic data compiled by the National Coal Board, Coal Research Establishment, on materials tested for the Electric Power Research Institute Contract R P 388-1 with Combustion Systems Ltd., UK. Two 1000 h tests were carried out to investigate the corrosion performance of boiler and gas turbine alloys exposed in and above a fluidised bed coal combustor. Details are given of the preparation, handling, and examination procedures. Results of metallographic examination and chemical analyses on the samples examined by CRE are provided. This appendix does not attempt to draw any conclusions from the data: such conclusions appear in the main report. Description of the tests and plant performance data are given in Appendix 1 of this report.

  8. Computational fluid dynamic modeling of fluidized-bed polymerization reactors

    Energy Technology Data Exchange (ETDEWEB)

    Rokkam, Ram [Iowa State Univ., Ames, IA (United States)

    2012-01-01

    Polyethylene is one of the most widely used plastics, and over 60 million tons are produced worldwide every year. Polyethylene is obtained by the catalytic polymerization of ethylene in gas and liquid phase reactors. The gas phase processes are more advantageous, and use fluidized-bed reactors for production of polyethylene. Since they operate so close to the melting point of the polymer, agglomeration is an operational concern in all slurry and gas polymerization processes. Electrostatics and hot spot formation are the main factors that contribute to agglomeration in gas-phase processes. Electrostatic charges in gas phase polymerization fluidized bed reactors are known to influence the bed hydrodynamics, particle elutriation, bubble size, bubble shape etc. Accumulation of electrostatic charges in the fluidized-bed can lead to operational issues. In this work a first-principles electrostatic model is developed and coupled with a multi-fluid computational fluid dynamic (CFD) model to understand the effect of electrostatics on the dynamics of a fluidized-bed. The multi-fluid CFD model for gas-particle flow is based on the kinetic theory of granular flows closures. The electrostatic model is developed based on a fixed, size-dependent charge for each type of particle (catalyst, polymer, polymer fines) phase. The combined CFD model is first verified using simple test cases, validated with experiments and applied to a pilot-scale polymerization fluidized-bed reactor. The CFD model reproduced qualitative trends in particle segregation and entrainment due to electrostatic charges observed in experiments. For the scale up of fluidized bed reactor, filtered models are developed and implemented on pilot scale reactor.

  9. Combustion studies in a fluidised bed-The link between temperature, NO{sub x} and N{sub 2}O formation, char morphology and coal type

    Energy Technology Data Exchange (ETDEWEB)

    Valentim, B.; Lemos de Sousa, M.J. [Centro de Geologia da Universidade do Porto, Faculdade de Ciencias, Praca de Gomes Teixeira, 4099-002, Porto (Portugal); Abelha, P.; Boavida, D.; Gulyurtlu, I. [Departamento de Engenharia Energetica e Controlo Ambiental (DEECA), Instituto Nacional de Engenharia, Tecnologia e Inovacao (INETI), Estrada do Paco do Lumiar, 22, Edif. J, 1649-038, Lisboa (Portugal)

    2006-06-06

    Five commercially available high volatile bituminous coals from different origins were studied with the objective of characterizing their petrographic nature with respect to emissions of NO{sub x} and N{sub 2}O. The chars produced [at temperatures ranging from 700 to 1000 {sup o}C] from these coals were also petrographic ally analyzed to assess the contribution of char to NO{sub x} and N{sub 2}O formation during combustion. Vitrinite-rich coals produced higher porous chars (cenospheres and tenuinetworks) than those that are rich in inertinite. The former coals were, however, found to release lower concentrations of NO. Consistent with previous works, N{sub 2}O emissions were observed to decrease significantly with temperature, however, on the whole, the N{sub 2}O emissions from vitrinite-rich high volatile coals were less than those from inertinite-rich coals. Additionally, high porous chars were found to give rise to lower emissions of NO and N{sub 2}O. (author)

  10. Fluid-bed combustion

    Energy Technology Data Exchange (ETDEWEB)

    Hunt, G.; Schoebotham, N.

    1981-02-01

    In Energy Equipment Company's two-stage fluidized bed system, partial combustion in a fluidized bed is followed by burn-off of the generated gases above the bed. The system can be retrofitted to existing boilers, and can burn small, high ash coal efficiently. It has advantages when used as a hot gas generator for process drying. Tests on a boiler at a Cadbury Schweppes plant are reported.

  11. Bernoulli Suction Effect on Soap Bubble Blowing?

    Science.gov (United States)

    Davidson, John; Ryu, Sangjin

    2015-11-01

    As a model system for thin-film bubble with two gas-liquid interfaces, we experimentally investigated the pinch-off of soap bubble blowing. Using the lab-built bubble blower and high-speed videography, we have found that the scaling law exponent of soap bubble pinch-off is 2/3, which is similar to that of soap film bridge. Because air flowed through the decreasing neck of soap film tube, we studied possible Bernoulli suction effect on soap bubble pinch-off by evaluating the Reynolds number of airflow. Image processing was utilized to calculate approximate volume of growing soap film tube and the volume flow rate of the airflow, and the Reynolds number was estimated to be 800-3200. This result suggests that soap bubbling may involve the Bernoulli suction effect.

  12. Single DNA denaturation and bubble dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Metzler, Ralf [Physics Department, Technical University of Munich, James Franck Strasse, 85747 Garching (Germany); Ambjoernsson, Tobias [Chemistry Department, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States); Hanke, Andreas [Department of Physics and Astronomy, University of Texas, 80 Fort Brown, Brownsville (United States); Fogedby, Hans C [Department of Physics and Astronomy, University of Arhus, Ny Munkegade, 8000 Arhus C (Denmark)], E-mail: metz@ph.tum.de

    2009-01-21

    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.

  13. Direct Numerical Simulation of the Lift Force in Bubbly Flows

    NARCIS (Netherlands)

    Dijkhuizen, W.; van Sint Annaland, M.; Kuipers, J.A.M.

    2008-01-01

    It is well-known that the lift force is responsible for the segregation of small and large bubbles encountered in bubbly flows through pipes and bubble columns: in the case of up flow small spherical bubbles move to the wall, while larger deformed bubbles move to the core region. Depending on the

  14. Heat transfer to immersed horizontal tubes in gas fluidized bed dryers

    Energy Technology Data Exchange (ETDEWEB)

    Jonassen, Ola

    1999-07-01

    The main objective of this study was to construct heat pump fluidized bed dryers of the FHT type with improved dewatering capacity for a given size of the dryer. The use of heat exchangers immersed in the fluidized bed drying chambers is an important part of the FHT (Fluidized Bed High Temperature Heat Pump Dryer) concept. A pilot plant FHT dryer was built and successfully tested on fish meal raw material and seaweed. The plant included two fluidized bed drying chambers with immersed heat exchangers. The gain in water vapor of the drying air through the chambers was increased up to four times that of adiabatic drying. The energy saving concept was retained as a SMER ratio of 3.5 to 4.7 was measured in the same tests. Therefore optimization of the immersed heat exchangers was considered the most important single objective for this work. The optimization study of the heat exchangers was confined to the actual operating conditions for the dryers using: (1) Bubbling gas fluidized beds were used, (2) air as the only type of fluidizing gas,(3) beds at atmospheric pressure, (4) bed temperatures below 100 {sup o}C, (5) fluidized particles of Geldart classes B and D, (6) horizontal tube banks for the immersed heat exchanger and the influence of radiation heat transfer was ignored. The heat transfer study was confined to the fluidized bed side of the heat exchanger surface. It was concluded early in this work that the bubbles play a major role in generating the particle circulation inside the bed and hence also in heat transfer. Publications describing the most important bubble induced mechanisms contributing to high rates of heat transfer were found to be limited. Therefore the first part of this study was aimed at establishing a method for locating and measuring the size and rise velocity of bubbles inside the bed. The method established through this work using differential pressure measurements from two static pressure probes was used later in the study of heat transfer

  15. Bed Bugs FAQs

    Science.gov (United States)

    ... CDC.gov . Bed Bugs Frequently Asked Questions (FAQs) Biology Resources for Health Professionals Publications Additional Resources Get Email Updates To receive email updates about this page, enter ...

  16. Bursting the bubble of melt inclusions

    Science.gov (United States)

    Lowenstern, Jacob B.

    2015-01-01

    Most silicate melt inclusions (MI) contain bubbles, whose significance has been alternately calculated, pondered, and ignored, but rarely if ever directly explored. Moore et al. (2015) analyze the bubbles, as well as their host glasses, and conclude that they often hold the preponderance of CO2 in the MI. Their findings entreat future researchers to account for the presence of bubbles in MI when calculating volatile budgets, saturation pressures, and eruptive flux.

  17. Cusped Bubbles Rising through Polyelectrolyte Solutions

    Science.gov (United States)

    Belmonte, Andrew; Sostarecz, Michael

    2000-11-01

    It is well known that a bubble rising in a polymer fluid can have a cusp-like tail. We report on an experimental study of bubbles rising through solutions of glycerol/water with the addition of the polymer xanthan gum, a polyelectrolyte which becomes more rigid as the free ion concentration is increased. The addition of salt also decreases the elasticity of the xanthan gum solutions, and we observe its effects on the velocity and shape of the cusped bubble.

  18. Detailed Jet Dynamics in a Collapsing Bubble

    Science.gov (United States)

    Supponen, Outi; Obreschkow, Danail; Kobel, Philippe; Farhat, Mohamed

    2015-12-01

    We present detailed visualizations of the micro-jet forming inside an aspherically collapsing cavitation bubble near a free surface. The high-quality visualizations of large and strongly deformed bubbles disclose so far unseen features of the dynamics inside the bubble, such as a mushroom-like flattened jet-tip, crown formation and micro-droplets. We also find that jetting near a free surface reduces the collapse time relative to the Rayleigh time.

  19. Asset Bubbles, Endogenous Growth, and Financial Frictions

    OpenAIRE

    Hirano, Tomohiro; Yanagawa, Noriyuki

    2016-01-01

    This paper analyzes the effects of bubbles in an infinitely-lived agent model of endogenous growth with financial frictions and heterogeneous agents. We provide a complete characterization on the relationship between financial frictions and the existence of bubbles. Our model predicts that if the degree of pledgeability is sufficiently high or sufficiently low, bubbles can not exist. They can only arise at an intermediate degree. This suggests that improving the financial market condition mig...

  20. Bubbles, Financial Crises, and Systemic Risk

    OpenAIRE

    Markus K. Brunnermeier; Martin Oehmke

    2012-01-01

    This chapter surveys the literature on bubbles, financial crises, and systemic risk. The first part of the chapter provides a brief historical account of bubbles and financial crisis. The second part of the chapter gives a structured overview of the literature on financial bubbles. The third part of the chapter discusses the literatures on financial crises and systemic risk, with particular emphasis on amplification and propagation mechanisms during financial crises, and the measurement of sy...

  1. COMPUTATIONAL AND EXPERIMENTAL MODELING OF THREE-PHASE SLURRY-BUBBLE COLUMN REACTOR

    Energy Technology Data Exchange (ETDEWEB)

    Isaac K. Gamwo; Dimitri Gidaspow

    1999-09-01

    Considerable progress has been achieved in understanding three-phase reactors from the point of view of kinetic theory. In a paper in press for publication in Chemical Engineering Science (Wu and Gidaspow, 1999) we have obtained a complete numerical solution of bubble column reactors. In view of the complexity of the simulation a better understanding of the processes using simplified analytical solutions is required. Such analytical solutions are presented in the attached paper, Large Scale Oscillations or Gravity Waves in Risers and Bubbling Beds. This paper presents analytical solutions for bubbling frequencies and standing wave flow patterns. The flow patterns in operating slurry bubble column reactors are not optimum. They involve upflow in the center and downflow at the walls. It may be possible to control flow patterns by proper redistribution of heat exchangers in slurry bubble column reactors. We also believe that the catalyst size in operating slurry bubble column reactors is not optimum. To obtain an optimum size we are following up on the observation of George Cody of Exxon who reported a maximum granular temperature (random particle kinetic energy) for a particle size of 90 microns. The attached paper, Turbulence of Particles in a CFB and Slurry Bubble Columns Using Kinetic Theory, supports George Cody's observations. However, our explanation for the existence of the maximum in granular temperature differs from that proposed by George Cody. Further computer simulations and experiments involving measurements of granular temperature are needed to obtain a sound theoretical explanation for the possible existence of an optimum catalyst size.

  2. Thermal decomposition of selected chlorinated hydrocarbons during gas combustion in fluidized bed

    Science.gov (United States)

    2013-01-01

    Background The process of thermal decomposition of dichloromethane (DCM) and chlorobenzene (MCB) during the combustion in an inert, bubbling fluidized bed, supported by LPG as auxiliary fuel, have been studied. The concentration profiles of C6H5CI, CH2Cl2, CO2, CO, NOx, COCl2, CHCl3, CH3Cl, C2H2, C6H6, CH4 in the flue gases were specified versus mean bed temperature. Results The role of preheating of gaseous mixture in fluidized bed prior to its ignition inside bubbles was identified as important factor for increase the degree of conversion of DCM and MCB in low bed temperature, in comparison to similar process in the tubular reactor. Conclusions Taking into account possible combustion mechanisms, it was identified that autoignition in bubbles rather than flame propagation between bubbles is needed to achieve complete destruction of DCM and MCB. These condition occurs above 900°C causing the degree of conversion of chlorine compounds of 92-100%. PMID:23289764

  3. Thermal decomposition of selected chlorinated hydrocarbons during gas combustion in fluidized bed

    Directory of Open Access Journals (Sweden)

    Olek Malgorzata

    2013-01-01

    Full Text Available Abstract Background The process of thermal decomposition of dichloromethane (DCM and chlorobenzene (MCB during the combustion in an inert, bubbling fluidized bed, supported by LPG as auxiliary fuel, have been studied. The concentration profiles of C6H5CI, CH2Cl2, CO2, CO, NOx, COCl2, CHCl3, CH3Cl, C2H2, C6H6, CH4 in the flue gases were specified versus mean bed temperature. Results The role of preheating of gaseous mixture in fluidized bed prior to its ignition inside bubbles was identified as important factor for increase the degree of conversion of DCM and MCB in low bed temperature, in comparison to similar process in the tubular reactor. Conclusions Taking into account possible combustion mechanisms, it was identified that autoignition in bubbles rather than flame propagation between bubbles is needed to achieve complete destruction of DCM and MCB. These condition occurs above 900°C causing the degree of conversion of chlorine compounds of 92-100%.

  4. 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. Copyright © 2014 Elsevier B.V. All rights reserved.

  5. Improvised bubble continuous positive airway pressure (BCPAP ...

    African Journals Online (AJOL)

    Improvised bubble continuous positive airway pressure (BCPAP) device at the National Hospital Abuja gives immediate improvement in respiratory rate and oxygenation in neonates with respiratory distress.

  6. Liquid jet formation through the interactions of a laser-induced bubble and a gas bubble

    Science.gov (United States)

    Han, Bing; Liu, Liu; Zhao, Xiong-Tao; Ni, Xiao-Wu

    2017-10-01

    The mechanisms of the liquid jet formation from the interaction of the laser-induced and gas bubble pair are investigated and compared with the jet formation from the interaction of the laser-induced anti-phase bubble pair. The strobe photography experimental method and numerical simulations are implemented to obtain the parameter space of the optimum liquid jet, i.e. highest speed and lowest diameter. It is found that due to the enhanced "catapult effect", which is induced by the protrusion of the first bubble into the second bubble and the flip back of the elongated part of the first bubble, the optimum liquid jet of the second bubble of the laser-induced anti-phase bubble pair compared to that of the laser-induced and gas bubble pair is 54 %, 65 % and 11 % faster in speed, and 4 %, 44 % and 64 % smaller in diameter, for the 500 μm, 50 μm and 5 μm sized bubbles, respectively. The optimum dimensionless distance for the optimum jet of the laser-induced and the gas bubble is around 0.7, when the maximum bubble radius increases from ˜ 5μm to ˜500 μm, which is different from the laser-induced anti-phase bubble pairs. Besides, the optimum jet of the laser-induced bubble appeared when the bubbles are equal sized, while that of the gas bubble is independent of the relative bubble size, i.e. the liquid jet of the gas bubble has higher robustness in real liquid jet assisted applications when the laser-induced bubble size varies. However, the jet of bubble 2 could maintain a high speed (20 m/s - 35 m/s) and a low diameter (˜5 % of the maximum bubble diameter) over a big range of the dimensionless distance (0.6 - 0.9) for both of the 50 μm and 500 μm sized laser-induced equal sized anti-phase bubble pairs.

  7. Modeling of fuel mixing in fluidized bed combustors

    Energy Technology Data Exchange (ETDEWEB)

    David Pallares; Filip Johnsson [Chalmers University of Technology, Goeteborg (Sweden). Department of Energy and Environment

    2008-12-15

    This paper presents a three-dimensional model for fuel mixing in fluidized bed combustors. The model accounts for mixing patterns which were experimentally shown to govern mixing in risers with geometry and operational conditions representative for furnaces in fluidized bed combustors. The mixing process is modeled for three different solid phases in the furnace and the model, which includes the return leg, can be applied both under bubbling and circulating regimes. The semi-empirical basis of the model was previously validated in different large-scale fluidized bed combustors and is combined with a model for fuel particle conversion to obtain the fuel concentration field. Model results are compared with experimental data from the Chalmers 12 MW{sub th} CFB combustor, yielding a reasonable agreement.

  8. Colorful Demos with a Long-Lasting Soap Bubble.

    Science.gov (United States)

    Behroozi, F.; Olson, D. W.

    1994-01-01

    Describes several demonstrations that feature interaction of light with soap bubbles. Includes directions about how to produce a long-lasting stationary soap bubble with an easily changeable size and describes the interaction of white light with the bubble. (DDR)

  9. Neural basis of economic bubble behavior.

    Science.gov (United States)

    Ogawa, A; Onozaki, T; Mizuno, T; Asamizuya, T; Ueno, K; Cheng, K; Iriki, A

    2014-04-18

    Throughout human history, economic bubbles have formed and burst. As a bubble grows, microeconomic behavior ceases to be constrained by realistic predictions. This contradicts the basic assumption of economics that agents have rational expectations. To examine the neural basis of behavior during bubbles, we performed functional magnetic resonance imaging while participants traded shares in a virtual stock exchange with two non-bubble stocks and one bubble stock. The price was largely deflected from the fair price in one of the non-bubble stocks, but not in the other. Their fair prices were specified. The price of the bubble stock showed a large increase and battering, as based on a real stock-market bust. The imaging results revealed modulation of the brain circuits that regulate trade behavior under different market conditions. The premotor cortex was activated only under a market condition in which the price was largely deflected from the fair price specified. During the bubble, brain regions associated with the cognitive processing that supports order decisions were identified. The asset preference that might bias the decision was associated with the ventrolateral prefrontal cortex and the dorsolateral prefrontal cortex (DLPFC). The activity of the inferior parietal lobule (IPL) was correlated with the score of future time perspective, which would bias the estimation of future price. These regions were deemed to form a distinctive network during the bubble. A functional connectivity analysis showed that the connectivity between the DLPFC and the IPL was predominant compared with other connectivities only during the bubble. These findings indicate that uncertain and unstable market conditions changed brain modes in traders. These brain mechanisms might lead to a loss of control caused by wishful thinking, and to microeconomic bubbles that expand, on the macroscopic scale, toward bust. Copyright © 2014 The Authors. Published by Elsevier Ltd.. All rights reserved.

  10. Intraoperative review of different bubble types formed during pneumodissection (big-bubble) deep anterior lamellar keratoplasty.

    Science.gov (United States)

    Goweida, Mohamed Bahgat Badawi

    2015-06-01

    To evaluate the preoperative factors and intraoperative complications of the 2 bubble types formed during big-bubble deep anterior lamellar keratoplasty (DALK). This is a retrospective review of medical records of a series of patients who underwent DALK using the big-bubble technique from September 2009 to March 2014. A total of 134 eyes were included in this study-89 eyes with advanced keratoconus, 35 eyes with post-microbial keratitis corneal scars, 8 eyes with stromal dystrophies, and 2 eyes with post-laser in situ keratomileusis ectasia. A type 1 bubble (white margin) was achieved in 56 eyes (41.8%), whereas a type 2 bubble (clear margin) was formed in 14 eyes (10.4%) and a mixed bubble was formed in 2 eyes (1.5%). Big-bubble formation failed in 62 (46.3%). All eyes with the type 1 bubble were completed as DALK; microperforation occurred in 4 eyes. Twelve of 14 eyes with the type 2 bubble were converted to penetrating keratoplasty because of large perforations. The type 2 bubble is more likely to form in elderly patients and those with deep corneal scars and thin corneas. Because of the high rate of conversion to penetrating keratoplasty, better surgical strategies may be needed to manage type 2 bubbles.

  11. Measurement of Bubble Size Distribution Based on Acoustic Propagation in Bubbly Medium

    Science.gov (United States)

    Wu, Xiongjun; Hsiao, Chao-Tsung; Choi, Jin-Keun; Chahine, Georges

    2013-03-01

    Acoustic properties are strongly affected by bubble size distribution in a bubbly medium. Measurement of the acoustic transmission becomes increasingly difficulty as the void fraction of the bubbly medium increases due to strong attenuation, while acoustic reflection can be measured more easily with increasing void fraction. The ABS ACOUSTIC BUBBLE SPECTROMETER®\\copyright, an instrument for bubble size measurement that is under development tries to take full advantage of the properties of acoustic propagation in bubbly media to extract bubble size distribution. Properties of both acoustic transmission and reflection in the bubbly medium from a range of short single-frequency bursts of acoustic waves at different frequencies are measured in an effort to deduce the bubble size distribution. With the combination of both acoustic transmission and reflection, assisted with validations from photography, the ABS ACOUSTIC BUBBLE SPECTROMETER®\\copyright has the potential to measure bubble size distributions in a wider void fraction range. This work was sponsored by Department of Energy SBIR program

  12. Bubble aspect ratio in dense bubbly flows: experimental studies in low Morton-number systems

    Science.gov (United States)

    Besagni, G.; Inzoli, F.; Ziegenhein, T.; Hessenkemper, H.; Lucas, D.

    2017-11-01

    Almost every modelling approach of bubbly flows includes assumptions concerning the bubble shape. Such assumptions are usually made based on single bubble experiments in quiescent flows, which is far away from the flow field observed in large-scale multiphase facilities. Considering low Morton-numbers and the highly deformable interface at medium and large Eötvös-numbers, the evaluation of the bubble shape in such systems under real flow conditions is highly desirable. In this study, we experimentally evaluate the bubble shape (in terms of aspect ratio), at low Morton-numbers, in different bubble column setups and a pipe flow setup under different operating conditions. The bubble shape in the bubble column experiments were obtained with cameras at Politecnico di Milano and Helmholtz-Zentrum Dresden Rossendorf (HZDR) whereas the shapes in the pipe flows were measured by the ultrafast electron beam X-ray tomography system (ROFEX) at HZDR. In the bubble column experiments almost the same shape is observed; conversely, the shape in the pipe flows distinctly depends on the flow conditions. In conclusion, in bubble columns the assumption of a constant shape regardless of the flow conditions is valid whereas in pipe flows the turbulence and shear rates can be strong enough to deform distinctly the bubbles.

  13. Bubble Movement on Inclined Hydrophobic Surfaces.

    Science.gov (United States)

    Kibar, Ali; Ozbay, Ridvan; Sarshar, Mohammad Amin; Kang, Yong Tae; Choi, Chang-Hwan

    2017-10-31

    The movement of a single air bubble on an inclined hydrophobic surface submerged in water, including both the upward- and downward-facing sides of the surface, was investigated. A planar Teflon sheet with an apparent contact angle of a sessile water droplet of 106° was used as a hydrophobic surface. The volume of a bubble and the inclination angle of a Teflon sheet varied in the ranges 5-40 μL and 0-45°, respectively. The effects of the bubble volume on the adhesion and dynamics of the bubble were studied experimentally on the facing-up and facing-down surfaces of the submerged hydrophobic Teflon sheet, respectively, and compared. The result shows that the sliding angle has an inverse relationship with the bubble volume for both the upward- and downward-facing surfaces. However, at the same given volume, the bubble on the downward-facing surface spreads over a larger area of the hydrophobic surface than the upward-facing surface due to the greater hydrostatic pressure acting on the bubble on the downward-facing surface. This makes the lateral adhesion force of the bubble greater and requires a larger inclination angle to result in sliding.

  14. The Minnaert Bubble: An Acoustic Approach

    Science.gov (United States)

    Devaud, Martin; Hocquet, Thierry; Bacri, Jean-Claude; Leroy, Valentin

    2008-01-01

    We propose an "ab initio" introduction to the well-known Minnaert pulsating bubble at graduate level. After a brief recall of the standard stuff, we begin with a detailed discussion of the radial movements of an air bubble in water. This discussion is managed from an acoustic point of view, and using the Lagrangian rather than the Eulerian…

  15. The life and death of film bubbles

    Science.gov (United States)

    Poulain, S.; Villermaux, E.; Bourouiba, L.

    2017-11-01

    Following its burst, the fragmentation of a large bubble (film bubble) at the air-water interface can release hundreds of micrometer-sized film-drops in the air we breathe. This mechanism of droplet formation is one of the most prominent sources of sea spray. Indoor or outdoor, pathogens from contaminated water are transported by these droplets and have also been linked to respiratory infection. The lifetime and thickness of bubbles govern the number and size of the droplets they produce. Despite these important implications, little is known about the factors influencing the life and death of surface film bubbles. In particular, the fundamental physical mechanisms linking bubble aging, thinning, and lifetime remain poorly understood. To address this gap, we present the results of an extensive investigation of the aging of film-drop-producing bubbles in various ambient air, water composition, and temperature conditions. We present and validate a generalized physical picture and model of bubble cap thickness evolution. The model and physical picture are linked to the lifetime of bubbles via a series of cap rupture mechanisms of increasing efficiency.

  16. Steady State Vapor Bubble in Pool Boiling.

    Science.gov (United States)

    Zou, An; Chanana, Ashish; Agrawal, Amit; Wayner, Peter C; Maroo, Shalabh C

    2016-02-03

    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.

  17. 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.

  18. Microfluidics with ultrasound-driven bubbles

    NARCIS (Netherlands)

    Marmottant, P.; Marmottant, P.G.M.; Raven, J.P.; Gardeniers, Johannes G.E.; Bomer, Johan G.; Hilgenfeldt, Sascha; Hilgenfeldt, S.

    2006-01-01

    Microstreaming from oscillating bubbles is known to induce vigorous vortex flow. Here we show how to harness the power of bubble streaming in an experiment to achieve directed transport flow of high velocity, allowing design and manufacture of microfluidic MEMS devices. By combining oscillating

  19. Videotaping the Lifespan of a Soap Bubble.

    Science.gov (United States)

    Ramme, Goran

    1995-01-01

    Describes how the use of a videotape to record the history of a soap bubble allows a study of many interesting events in considerable detail including interference fringes, convection and turbulence patterns on the surface, formation of black film, and the ultimate explosion of the bubble. (JRH)

  20. The Interaction of Two Underwater Explosion Bubbles

    Science.gov (United States)

    Milligan, Charles; Duncan, James

    1996-11-01

    The interaction between two growing and collapsing underwater explosion bubbles is studied experimentally and numerically. In the experiments, the bubbles are generated by detonating small Lead Azide explosive charges submerged in a transparent water tank, and the resulting interactions are photographed using a high-speed camera. The parametric studies include simultaneous detonation of two charges of different sizes, and detonation of identically sized charges at staggered times. When the time delay between detonations is significant, the collapsing first bubble forms a jet directed away from the expanding second bubble and then re-expands nonspherically. During the re-expansion of the first bubble, a micro-jet forms in the second bubble. Eventually this micro-jet pierces the side of the second bubble farthest from the first and vortex rings are formed. Numerical simulations of the interaction phenomena are achieved using a boundary element method. By partitioning the system into computational sub-domains it is possible to replicate many relevant physical details including jet formation, fluid-fluid impact, and bubble re-expansion after complete jet penetration. The numerical results are in qualitative agreement with the experimental findings.

  1. Interaction of cavitation bubbles on a wall

    NARCIS (Netherlands)

    Bremond, Nicolas; Bremond, N.P.; Arora, M.; Dammer, S.M.; Lohse, Detlef

    2006-01-01

    We report experimental and numerical investigations on the dynamics of the cavitation of bubbles on a solid surface and the interaction between them with the help of controlled cavitation nuclei: hemispherical bubbles are nucleated from hydrophobic microcavities that act as gas traps when the

  2. Clustering and Lagrangian Statistics of Bubbles

    NARCIS (Netherlands)

    Martinez Mercado, J.

    2011-01-01

    Due to their relevance and occurrence in both natural phenomena and in industrial applications, the study and understanding of bubbly flows is currently an important topic for fluid dynamicists. Bubble columns are commonly used in bio- and petrochemical industries to enhance mixing, mass and heat

  3. The charged bubble oscillator: Dynamics and thresholds

    Indian Academy of Sciences (India)

    Technology-Bangalore (IIIT-B), 26/C Electronics City, Hosur Road, Bengaluru 560 100, India. 2School of Natural Sciences & Engineering, .... liquid, the difference in pressure causes expansion and rapid collapse of the bubble, followed ... of the dimensions of the bubble, we define an expansion- compression ratio that we ...

  4. The use of microholography in bubble chambers

    CERN Document Server

    Royer, H

    1981-01-01

    In-line holography has been used for the first time in a bubble chamber for the account of the CERN (Geneva, CH). The holograms were recorded with the help of a single-mode pulse laser. Bubble tracks of 25 microns in diameter have been reconstructed with a resolution of 2 microns. (12 refs).

  5. Laminar separation bubbles: Dynamics and control

    Indian Academy of Sciences (India)

    it thus are essential prerequisites for efficient design of these aerodynamic devices. Gaster. (1967) was the first to systematically explore the stability characteristics associated with the transition taking place in separation bubble. Many recent studies have been directed towards exploring the dynamics of separation bubbles ...

  6. Laminar separation bubbles: Dynamics and control

    Indian Academy of Sciences (India)

    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.

  7. Cavitation inception from bubble nuclei

    Science.gov (United States)

    Mørch, K. A.

    2015-01-01

    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

  8. Investigation of Multiphase Flow in a Packed Bed Reactor Under Microgravity Conditions

    Science.gov (United States)

    Lian, Yongsheng; Motil, Brian; Rame, Enrique

    2016-01-01

    In this paper we study the two-phase flow phenomena in a packed bed reactor using an integrated experimental and numerical method. The cylindrical bed is filled with uniformly sized spheres. In the experiment water and air are injected into the bed simultaneously. The pressure distribution along the bed will be measured. The numerical simulation is based on a two-phase flow solver which solves the Navier-Stokes equations on Cartesian grids. A novel coupled level set and moment of fluid method is used to construct the interface. A sequential method is used to position spheres in the cylinder. Preliminary experimental results showed that the tested flow rates resulted in pulse flow. The numerical simulation revealed that air bubbles could merge into larger bubbles and also could break up into smaller bubbles to pass through the pores in the bed. Preliminary results showed that flow passed through regions where the porosity is high. Comparison between the experimental and numerical results in terms of pressure distributions at different flow injection rates will be conducted. Comparison of flow phenomena under terrestrial gravity and microgravity will be made.

  9. 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

  10. Constraining hadronic models of the Fermi bubbles

    Science.gov (United States)

    Razzaque, Soebur

    2018-01-01

    The origin of sub-TeV gamma rays detected by Fermi-LAT from the Fermi bubbles at the Galactic center is unknown. In a hadronic model, acceleration of protons and/or nuclei and their subsequent interactions with gas in the bubble volume can produce observed gamma ray. Such interactions naturally produce high-energy neutrinos, and detection of those can discriminate between a hadronic and a leptonic origin of gamma rays. Additional constraints on the Fermi bubbles gamma-ray flux in the PeV range from recent HAWC observations restrict hadronic model parameters, which in turn disfavor Fermi bubbles as the origin of a large fraction of neutrino events detected by IceCube along the bubble directions. We revisit our hadronic model and discuss future constraints on parameters from observations in very high-energy gamma rays by CTA and in neutrinos.

  11. 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)

  12. Bubble mobility in mud and magmatic volcanoes

    Science.gov (United States)

    Tran, Aaron; Rudolph, Maxwell L.; Manga, Michael

    2015-03-01

    The rheology of particle-laden fluids with a yield stress, such as mud or crystal-rich magmas, controls the mobility of bubbles, both the size needed to overcome the yield stress and their rise speed. We experimentally measured the velocities of bubbles and rigid spheres in mud sampled from the Davis-Schrimpf mud volcanoes adjacent to the Salton Sea, Southern California. Combined with previous measurements in the polymer gel Carbopol, we obtained an empirical model for the drag coefficient and bounded the conditions under which bubbles overcome the yield stress. Yield stresses typical of mud and basaltic magmas with sub-mm particles can immobilize millimeter to centimeter sized bubbles. At Stromboli volcano, Italy, a vertical yield stress gradient in the shallow conduit may immobilize bubbles with diameter ≲ 1 cm and hinder slug coalescence.

  13. Mesoporous hollow spheres from soap bubbling.

    Science.gov (United States)

    Yu, Xianglin; Liang, Fuxin; Liu, Jiguang; Lu, Yunfeng; Yang, Zhenzhong

    2012-02-01

    The smaller and more stable bubbles can be generated from the large parent bubbles by rupture. In the presence of a bubble blowing agent, hollow spheres can be prepared by bubbling a silica sol. Herein, the trapped gas inside the bubble acts as a template. When the porogen, i.e., other surfactant, is introduced, a mesostructured shell forms by the co-assembly with the silica sol during sol-gel process. Morphological evolution emphasizes the prerequisite of an intermediate interior gas flow rate and high exterior gas flow rate for hollow spheres. The method is valid for many compositions from inorganic, polymer to their composites. Copyright © 2011 Elsevier Inc. All rights reserved.

  14. Primordial black hole formation by vacuum bubbles

    Science.gov (United States)

    Deng, Heling; Vilenkin, Alexander

    2017-12-01

    Vacuum bubbles may nucleate during the inflationary epoch and expand, reaching relativistic speeds. After inflation ends, the bubbles are quickly slowed down, transferring their momentum to a shock wave that propagates outwards in the radiation background. The ultimate fate of the bubble depends on its size. Bubbles smaller than certain critical size collapse to ordinary black holes, while in the supercritical case the bubble interior inflates, forming a baby universe, which is connected to the exterior region by a wormhole. The wormhole then closes up, turning into two black holes at its two mouths. We use numerical simulations to find the masses of black holes formed in this scenario, both in subcritical and supercritical regime. The resulting mass spectrum is extremely broad, ranging over many orders of magnitude. For some parameter values, these black holes can serve as seeds for supermassive black holes and may account for LIGO observations.

  15. Interacting bubble clouds and their sonochemical production

    CERN Document Server

    Stricker, Laura; Rivas, David Fernandez; Lohse, Detlef

    2013-01-01

    Acoustically driven air pockets trapped in artificial crevices on a sur- face can emit bubbles which organize in (interacting) bubble clusters. With increasing driving power Fernandez Rivas et al. [Angew. Chem. Int. Ed., 2010] observed three different behaviors: clusters close to the very pits out of which they had been created, clusters pointing toward each other, and merging clusters. The latter behavior is highly undesired for technological purposes as it is associated with a reduction of the radical production and an enhancement of the erosion of the reactor walls. The dependence on the control parameters such as the distance of the pits and the conditions for cluster-merging are examined. The underlying mechanism, governed by the secondary Bjerknes forces, turns out to be strongly influenced by the nonlinearity of the bubble oscillations and not directly by the number of nucleated bubbles. The Bjerknes forces are found to dampen the bubble oscillations, thus reducing the radical production. Therefore, th...

  16. Bubble streams rising beneath an inclined surface

    Science.gov (United States)

    Bird, James; Brasz, Frederik; Kim, Dayoung; Menesses, Mark; Belden, Jesse

    2017-11-01

    Bubbles released beneath a submerged inclined surface can tumble along the wall as they rise, dragging the surrounding fluid with them. This effect has recently regained attention as a method to mitigate biofouling in marine environment, such as a ship hull. It appears that the efficacy of this approach may be related to the velocity of the rising bubbles and the extent that they spread laterally as they rise. Yet, it is unclear how bubble stream rise velocity and lateral migration depend on bubble size, flow rate, and inclination angle. Here we perform systematic experiments to quantify these relationships for both individual bubble trajectories and ensemble average statistics. Research supported by the Office of Naval Research under Grant Number award N00014-16-1-3000.

  17. Fluorination of UF{sub 4} in a mini-tapered fluidized bed and mathematical modeling

    Energy Technology Data Exchange (ETDEWEB)

    Khani, M.H., E-mail: mhkhani@aeoi.org.i [Nuclear Fuel Cycle Research School, Nuclear Science and Technology Research Institute, P.O. Box 14395, 836 Tehran (Iran, Islamic Republic of); Ghannadi, M. [Nuclear Fuel Cycle Research School, Nuclear Science and Technology Research Institute, P.O. Box 14395, 836 Tehran (Iran, Islamic Republic of); Pahlavanzadeh, H. [Department of Chemical Engineering, Faculty of Engineering, Tarbiat Modares University, P.O. Box 11365, 8486 Tehran (Iran, Islamic Republic of)

    2010-09-15

    A mini-tapered fluidized bed reactor can be used for fluorination reaction of UF{sub 4} to produce uranium hexafluoride. By adopting the mini-tapered bed the problems associated with fluidization in a cylindrical bed such as entrainment of particles and the limitation of operating velocity can be overcome, consequently the performance of the reactor can be enhanced. Simulation of the reactor was performed employing two-phase models, bubble phase with piston flow and emulsion phase with piston (D.P-P model) or perfectly mixed flow (D.P-M model). The voidage of the emulsion and bubble phases were estimated from the distribution two-phase structure hydrodynamic model. The model predictions have been compared with the results from a pilot-scale experiment. The D.P-P model gives good agreement between computed and empirical results. The effects of various parameters on the reactor performance are discussed using the model.

  18. Gas bubble dynamics in soft materials.

    Science.gov (United States)

    Solano-Altamirano, J M; Malcolm, John D; Goldman, Saul

    2015-01-07

    Epstein and Plesset's seminal work on the rate of gas bubble dissolution and growth in a simple liquid is generalized to render it applicable to a gas bubble embedded in a soft elastic solid. Both the underlying diffusion equation and the expression for the gas bubble pressure were modified to allow for the non-zero shear modulus of the medium. The extension of the diffusion equation results in a trivial shift (by an additive constant) in the value of the diffusion coefficient, and does not change the form of the rate equations. But the use of a generalized Young-Laplace equation for the bubble pressure resulted in significant differences on the dynamics of bubble dissolution and growth, relative to an inviscid liquid medium. Depending on whether the salient parameters (solute concentration, initial bubble radius, surface tension, and shear modulus) lead to bubble growth or dissolution, the effect of allowing for a non-zero shear modulus in the generalized Young-Laplace equation is to speed up the rate of bubble growth, or to reduce the rate of bubble dissolution, respectively. The relation to previous work on visco-elastic materials is discussed, as is the connection of this work to the problem of Decompression Sickness (specifically, "the bends"). Examples of tissues to which our expressions can be applied are provided. Also, a new phenomenon is predicted whereby, for some parameter values, a bubble can be metastable and persist for long times, or it may grow, when embedded in a homogeneous under-saturated soft elastic medium.

  19. Observation of Microhollows Produced by Bubble Cloud Cavitation

    Science.gov (United States)

    Yamakoshi, Yoshiki; Miwa, Takashi

    2012-07-01

    When an ultrasonic wave with sound pressure less than the threshold level of bubble destruction irradiates microbubbles, the microbubbles aggregate by an acoustic radiation force and form bubble clouds. The cavitation of bubble clouds produces a large number of microhollows (microdips) on the flow channel wall. In this study, microhollow production by bubble cloud cavitation is evaluated using a blood vessel phantom made of N-isopropylacrylamide (NIPA) gel. Microbubble dynamics in bubble cloud cavitation is observed by a microscope with a short pulse light emitted diode (LED) light source. Microhollows produced on the flow channel wall are evaluated by a confocal laser microscope with a water immersion objective. It is observed that a mass of low-density bubbles (bubble mist) is formed by bubble cloud cavitation. The spatial correlation between the bubble mist and the microhollows shows the importance of the bubble mist in microhollow production by bubble cloud cavitation.

  20. Tapered bed bioreactor

    Science.gov (United States)

    Scott, Charles D.; Hancher, Charles W.

    1977-01-01

    A vertically oriented conically shaped column is used as a fluidized bed bioreactor wherein biologically catalyzed reactions are conducted in a continuous manner. The column utilizes a packing material a support having attached thereto a biologically active catalytic material.

  1. Bed Bugs - Multiple Languages

    Science.gov (United States)

    ... Supplements Videos & Tools You Are Here: Home → Multiple Languages → All Health Topics → Bed Bugs URL of this page: https://medlineplus.gov/languages/bedbugs.html Other topics A-Z Expand Section ...

  2. Nonlinear ultrasonic waves in bubbly liquids with nonhomogeneous bubble distribution: Numerical experiments.

    Science.gov (United States)

    Vanhille, Christian; Campos-Pozuelo, Cleofé

    2009-06-01

    This paper deals with the nonlinear propagation of ultrasonic waves in mixtures of air bubbles in water, but for which the bubble distribution is nonhomogeneous. The problem is modelled by means of a set of differential equations which describes the coupling of the acoustic field and bubbles vibration, and solved in the time domain via the use and adaptation of the SNOW-BL code. The attenuation and nonlinear effects are assumed to be due to the bubbles exclusively. The nonhomogeneity of the bubble distribution is introduced by the presence of bubble layers (or clouds) which can act as acoustic screens, and alters the behaviour of the ultrasonic waves. The effect of the spatial distribution of bubbles on the nonlinearity of the acoustic field is analyzed. Depending on the bubble density, dimension, shape, and position of the layers, its effects on the acoustic field change. Effects such as shielding and resonance of the bubbly layers are especially studied. The numerical experiments are carried out in two configurations: linear and nonlinear, i.e. for low and high excitation pressure amplitude, respectively, and the features of the phenomenon are compared. The parameters of the medium are chosen such as to reproduce air bubbly water involved in the stable cavitation process.

  3. Effect of bubble's arrangement on the viscous torque in bubbly Taylor-Couette flow

    Science.gov (United States)

    Fokoua, G. Ndongo; Gabillet, C.; Aubert, A.; Colin, C.

    2015-03-01

    An experimental investigation of the interactions between bubbles, coherent motion, and viscous drag in a Taylor-Couette flow with the outer cylinder at rest is presented. The cylinder radii ratio η is 0.91. Bubbles are injected inside the gap through a needle at the bottom of the apparatus. Different bubbles sizes are investigated (ratio between the bubble diameter and the gap width ranges from 0.05 to 0.125) for very small void fraction (α ≤ 0.23%). Different flow regimes are studied corresponding to Reynolds number Re based on the gap width and velocity of the inner cylinder, ranging from 6 × 102 to 2 × 104. Regarding these Re values, Taylor vortices are persistent leading to an axial periodicity of the flow. A detailed characterization of the vortices is performed for the single-phase flow. The experiment also develops bubbles tracking in a meridian plane and viscous torque of the inner cylinder measurements. The findings of this study show evidence of the link between bubbles localisation, Taylor vortices, and viscous torque modifications. We also highlight two regimes of viscous torque modification and various types of bubbles arrangements, depending on their size and on the Reynolds number. Bubbles can have a sliding and wavering motion near the inner cylinder and be either captured by the Taylor vortices or by the outflow areas near the inner cylinder. For small buoyancy effect, bubbles are trapped, leading to an increase of the viscous torque. When buoyancy induced bubbles motion is increased by comparison to the coherent motion of the liquid, a decrease in the viscous torque is rather observed. The type of bubble arrangement is parameterized by the two dimensionless parameters C and H introduced by Climent et al. ["Preferential accumulation of bubbles in Couette-Taylor flow patterns," Phys. Fluids 19, 083301 (2007)]. Phase diagrams summarizing the various types of bubbles arrangements, viscous torque modifications, and axial wavelength evolution are

  4. Detonation wave phenomena in bubbled liquid

    Science.gov (United States)

    Gülhan, A.; Beylich, A. E.

    1990-07-01

    Shock wave propagation was investigated in two phase media consisting of diluted glycerin (85%) and reactive gas bubbles. To understand these complex phenomena, we first performed a numerical analysis and experimental studies of single bubbles containing a reactive gas-mixture. For the two-phase mixtures, a needle matrix bubble-generator enabled us to produce a homogeneous bubble distribution with a size dispersion less than 5%. The void fraction β0 was varied over one order of magnitude, β0=0.2-2%. It was found that there exists a critical value of shock strength above which bubble explosion starts. Once a bubble explodes, it stimulates the adjacent bubbles to explode due to emission of a blast wave; this process is followed by a series of similar events. A steady detonationlike wave propagates as a precurser with a constant velocity which is much higher than that of the first wave. To study the structure of the detonation wave the measured pressured profiles were averaged by superimposing 50 shots.

  5. The rheology of gravity driven bubbly liquids

    Science.gov (United States)

    Martinez-Mercado, Julian; Zenit, Roberto

    2002-11-01

    Experiments on a vertical channel were performed to to study the behavior of a monodispersed bubble suspension. Using water and water-glycerin mixtures, we were able to obtain measurements for a range of Reynolds and Weber numbers. To generate a uniform stream of bubbles an array of identical capillaries was used. To avoid the coalescence effects, a small amount of salt was added to the interstitial fluid, which did not affect the fluid properties significantly. Measurements of the bubble phase velocity were obtained using a dual impedance probe and through high speed digital video processing. We also obtained measurements of the bubble size and shape as a function of the gas volume fraction for the different flow regimes. We found that, for all cases, the bubble velocity decreases as mean gas volume fraction increases. The flow agitation, characterized with the bubble velocity variance, increases with bubble concentration. The flow becomes unstable for lower gas concentrations as the viscosity of the interstitial fluid increases.

  6. Shock waves from nonspherical cavitation bubbles

    Science.gov (United States)

    Supponen, Outi; Obreschkow, Danail; Kobel, Philippe; Tinguely, Marc; Dorsaz, Nicolas; Farhat, Mohamed

    2017-09-01

    We present detailed observations of the shock waves emitted at the collapse of single cavitation bubbles using simultaneous time-resolved shadowgraphy and hydrophone pressure measurements. The geometry of the bubbles is systematically varied from spherical to very nonspherical by decreasing their distance to a free or rigid surface or by modulating the gravity-induced pressure gradient aboard parabolic flights. The nonspherical collapse produces multiple shocks that are clearly associated with different processes, such as the jet impact and the individual collapses of the distinct bubble segments. For bubbles collapsing near a free surface, the energy and timing of each shock are measured separately as a function of the anisotropy parameter ζ , which represents the dimensionless equivalent of the Kelvin impulse. For a given source of bubble deformation (free surface, rigid surface, or gravity), the normalized shock energy depends only on ζ , irrespective of the bubble radius R0 and driving pressure Δ p . Based on this finding, we develop a predictive framework for the peak pressure and energy of shock waves from nonspherical bubble collapses. Combining statistical analysis of the experimental data with theoretical derivations, we find that the shock peak pressures can be estimated as jet impact-induced hammer pressures, expressed as ph=0.45 (ρc2Δ p ) 1 /2ζ-1 at ζ >10-3 . The same approach is found to explain the shock energy decreasing as a function of ζ-2 /3.

  7. Performance Tests for Bubble Blockage Device

    Energy Technology Data Exchange (ETDEWEB)

    Ha, Kwang Soon; Wi, Kyung Jin; Park, Rae Joon; Wan, Han Seong [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2014-05-15

    Postulated severe core damage accidents have a high threat risk for the safety of human health and jeopardize the environment. Versatile measures have been suggested and applied to mitigate severe accidents in nuclear power plants. To improve the thermal margin for the severe accident measures in high-power reactors, engineered corium cooling systems involving boiling-induced two-phase natural circulation have been proposed for decay heat removal. A boiling-induced natural circulation flow is generated in a coolant path between a hot vessel wall and cold coolant reservoir. In general, it is possible for some bubbles to be entrained in the natural circulation loop. If some bubbles entrain in the liquid phase flow passage, flow instability may occur, that is, the natural circulation mass flow rate may be oscillated. A new device to block the entraining bubbles is proposed and verified using air-water test loop. To avoid bubbles entrained in the natural circulation flow loop, a new device was proposed and verified using an air-water test loop. The air injection and liquid circulation loop was prepared, and the tests for the bubble blockage devices were performed by varying the geometry and shape of the devices. The performance of the bubble blockage device was more effective as the area ratio of the inlet to the down-comer increased, and the device height decreased. If the device has a rim to generate a vortex zone, the bubbles will be most effectively blocked.

  8. Bubbles in live-stranded dolphins.

    Science.gov (United States)

    Dennison, S; Moore, M J; Fahlman, A; Moore, K; Sharp, S; Harry, C T; Hoppe, J; Niemeyer, M; Lentell, B; Wells, R S

    2012-04-07

    Bubbles in supersaturated tissues and blood occur in beaked whales stranded near sonar exercises, and post-mortem in dolphins bycaught at depth and then hauled to the surface. To evaluate live dolphins for bubbles, liver, kidneys, eyes and blubber-muscle interface of live-stranded and capture-release dolphins were scanned with B-mode ultrasound. Gas was identified in kidneys of 21 of 22 live-stranded dolphins and in the hepatic portal vasculature of 2 of 22. Nine then died or were euthanized and bubble presence corroborated by computer tomography and necropsy, 13 were released of which all but two did not re-strand. Bubbles were not detected in 20 live wild dolphins examined during health assessments in shallow water. Off-gassing of supersaturated blood and tissues was the most probable origin for the gas bubbles. In contrast to marine mammals repeatedly diving in the wild, stranded animals are unable to recompress by diving, and thus may retain bubbles. Since the majority of beached dolphins released did not re-strand it also suggests that minor bubble formation is tolerated and will not lead to clinically significant decompression sickness.

  9. Inert gas bubbles in bcc Fe

    Energy Technology Data Exchange (ETDEWEB)

    Gai, Xiao, E-mail: windgx22@hotmail.com; Smith, Roger, E-mail: r.smith@lboro.ac.uk; Kenny, S.D., E-mail: masdk@lboro.ac.uk

    2016-03-15

    The properties of inert gas bubbles in bcc Fe is examined using a combination of static energy minimisation, molecular dynamics and barrier searching methods with empirical potentials. Static energy minimisation techniques indicate that for small Ar and Xe bubbles, the preferred gas to vacancy ratio at 0 K is about 1:1 for Ar and varies between 0.5:1 and 0.9:1 for Xe. In contrast to interstitial He atoms and small He interstitial clusters, which are highly mobile in the lattice, Ar and Xe atoms prefer to occupy substitutional sites and any interstitials present in the lattice soon displace Fe atoms and become substitutional. If a pre-existing bubble is present then there is a capture radius around a bubble which extends up to the 6th neighbour position. Collision cascades can also enlarge an existing bubble by the capture of vacancies. Ar and Xe can diffuse through the lattice through vacancy driven mechanisms but with relatively high energy barriers of 1.8 and 2.0 eV respectively. This indicates that Ar and Xe bubbles are much harder to form than bubbles of He and that such gases produced in a nuclear reaction would more likely be dispersed at substitutional sites without the help of increased temperature or radiation-driven mechanisms.

  10. Biodegradation of phenolic wastewaters in a three-phase fluidized bed bioreactor with the KMT{reg_sign} biomass support

    Energy Technology Data Exchange (ETDEWEB)

    Sokol, W.; Halfini, M.R. [Univ. of Dar es Salaam (Tanzania, United Republic of)

    1996-12-31

    A treatment of wastewater from a local refinery in a three-phase fluidised bed bioreactor with the KMT{sup R} biomass support was investigated. It was found that after adding mineral salts to the wastewater to be treated, a reduction in the COD values increased from about 55% to almost 90%. The reduction in COD was increasing with an increase in both a superficial air velocity and a ratio of bed volume to bioreactor volume (V{sub b}/V{sub r}). The highest value of (V{sub b}/V{sub r}) which could be applied in the experiments was 0.7, because at larger (V{sub b}/V{sub r}) movement of the whole bed was impossible. The bioreactor as operated was not successful in degrading thiocyanates, cyanides, nitrates and ammonia. However, results of independent experiments that have been started to adapt the symbiotic populations of microorganisms that may effectively degrade those compounds are promising. Stratification of the support media coated with the biomass led to their movement to the base of the bioreactor where concentration of organic compounds was highest. This was desirable since the compounds could penetrate far into the biofilm so most of the biomass grown on the support was active. 6 refs., 3 figs.

  11. Pressure waves in a supersaturated bubbly magma

    Science.gov (United States)

    Kurzon, I.; Lyakhovsky, V.; Navon, O.; Chouet, B.

    2011-01-01

    We study the interaction of acoustic pressure waves with an expanding bubbly magma. The expansion of magma is the result of bubble growth during or following magma decompression and leads to two competing processes that affect pressure waves. On the one hand, growth in vesicularity leads to increased damping and decreased wave amplitudes, and on the other hand, a decrease in the effective bulk modulus of the bubbly mixture reduces wave velocity, which in turn, reduces damping and may lead to wave amplification. The additional acoustic energy originates from the chemical energy released during bubble growth. We examine this phenomenon analytically to identify conditions under which amplification of pressure waves is possible. These conditions are further examined numerically to shed light on the frequency and phase dependencies in relation to the interaction of waves and growing bubbles. Amplification is possible at low frequencies and when the growth rate of bubbles reaches an optimum value for which the wave velocity decreases sufficiently to overcome the increased damping of the vesicular material. We examine two amplification phase-dependent effects: (1) a tensile-phase effect in which the inserted wave adds to the process of bubble growth, utilizing the energy associated with the gas overpressure in the bubble and therefore converting a large proportion of this energy into additional acoustic energy, and (2) a compressive-phase effect in which the pressure wave works against the growing bubbles and a large amount of its acoustic energy is dissipated during the first cycle, but later enough energy is gained to amplify the second cycle. These two effects provide additional new possible mechanisms for the amplification phase seen in Long-Period (LP) and Very-Long-Period (VLP) seismic signals originating in magma-filled cracks.

  12. Optical diagnostics study of air flow and powder fluidisation in Nexthaler®--Part I: Studies with lactose placebo formulation.

    Science.gov (United States)

    Pasquali, I; Merusi, C; Brambilla, G; Long, E J; Hargrave, G K; Versteeg, H K

    2015-12-30

    Effective drug delivery to the lungs by a DPI device requires the air-stream through the device to have sufficient power to aerosolise the powder. Furthermore, sufficient turbulence must be induced, along with particle-wall and particle-particle collisions, in order to de-aggregate small drug particles from large carrier particles. As a result, the emitted and the fine particle doses produced by many commercially available DPI devices tend to be strongly affected by the natural inter-patient variability of the inhaled air flow. The Nexthaler® is a multi-dose breath-actuated dry-powder inhaler with minimum drug delivery-flow rate dependency and incorporating a dose protector. The actuation mechanism of the dose-protector ensures that the dose is only exposed to the inhaled air flow if the flow has sufficient power to cause complete aerosolisation. For this study, a proprietary lactose placebo powder blend was filled into "transparent" Nexthaler® to allow application of high-speed imaging and particle image velocimetry (PIV) techniques to successfully interrogate and reveal details of the powder entrainment and emission processes coupled with characterisation of the flow environment in the vicinity of the mouthpiece exit. The study showed that fluidisation of the bulk of the powder occurs very quickly (∼20ms) after withdrawal of the dose protector followed by powder emission from the device within ∼50ms thereafter. The bulk of the metered placebo dose was emitted within 100-200ms. The visualisation study also revealed that a very small fraction of powder fines is emitted whilst the dose protector still covers the dosing cup as the flow rate through the device accelerates. The PIV results show that the flow exiting the device is highly turbulent with a rotating flow structure, which forces the particles to follow internal paths having a high probability of wall impacts, suggesting that the flow environment inside the Nexthaler® DPI will be very beneficial for

  13. Bed mixing dryer for high moisture content fuels

    Energy Technology Data Exchange (ETDEWEB)

    Hulkkonen, S.; Heinonen, O. [Imatran Voima Oy, Vantaa (Finland)

    1997-12-31

    Bed mixing dryer is a new type of fuel drying technology for fluidized bed combustion. The idea is to extract hot bed material from the fluidized bed and use it as a heat source for drying the fuel. Drying occurs at steam atmosphere which makes it possible to recover the latent heat of evaporation to process. This improves the thermal efficiency of the power plant process considerably, especially in combined heat and power applications. Imatran Voima Oy (IVO) has developed the Bed Mixing Dryer technology since early 1990s. The first pilot plant was built in 1994 to IVO`s Kuusamo peat and wood fired power plant. The capacity of the plant is 6 MW{sub e} and 20 MW of district heat. In Kuusamo the dryer is connected to a bubbling fluidized bed. Since it`s commissioning the dryer has been used successfully for about 3000 hours during the heating season in wintertime. The second application of the technology will be a demonstration project in Oerebro (S). IVO Power Engineering Ltd will supply in 1997 a dryer to Oerebro Energi`s peat, wood and coal fired CHP plant equipped with circulating fluidized bed boiler. The fuel to be dried is sawdust with fuel input of about 60 MW. In Kuusamo the dryer produces 3 MW of additional district heat and in Oerebro 6 MW. The fuels in Kuusamo are peat, saw dust and bark. In addition to the municipal heat production this type of drying technology has its benefits in pulp and paper industry processes. Disposal of paper mill sludges is becoming more difficult and costly which has resulted in need of alternative treatment. Drying of the sludge before combustion in a boiler for power production is an attractive option. At the moment IVO is carrying out several studies to apply the Bed Mixing Dryer in pulp and paper industry processes. Economy of drying the sludge looks promising

  14. Numerical investigation of bubble nonlinear dynamics characteristics

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Jie, E-mail: shijie@hrbeu.edu.cn; Yang, Desen; Shi, Shengguo; Hu, Bo [Acoustic Science and Technology Laboratory, Harbin Engineering University, Harbin 150001 (China); College of Underwater Acoustic Engineering, Harbin Engineering University, Harbin 150001 (China); Zhang, Haoyang; Jiang, Wei [College of Underwater Acoustic Engineering, Harbin Engineering University, Harbin 150001 (China)

    2015-10-28

    The complicated dynamical behaviors of bubble oscillation driven by acoustic wave can provide favorable conditions for many engineering applications. On the basis of Keller-Miksis model, the influences of control parameters, including acoustic frequency, acoustic pressure and radius of gas bubble, are discussed by utilizing various numerical analysis methods, Furthermore, the law of power spectral variation is studied. It is shown that the complicated dynamic behaviors of bubble oscillation driven by acoustic wave, such as bifurcation and chaos, further the stimulated scattering processes are revealed.

  15. Single DNA denaturation and bubble dynamics

    DEFF Research Database (Denmark)

    Metzler, Ralf; Ambjörnsson, Tobias; Hanke, Andreas

    2009-01-01

    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...

  16. A view inside the Gargamelle bubble chamber

    CERN Multimedia

    1970-01-01

    Gargamelle was the name given to a big bubble chamber built at the Saclay Laboratory in France during the late 1960s. It was designed principally for the detection at CERN of the elusive particles called neutrinos. A bubble chamber contains a liquid under pressure, which reveals the tracks of electrically charged particles as trails of tiny bubbles when the pressure is reduced. Neutrinos have no charge, and so leave no tracks, but the aim with Gargamelle was "see neutrinos" by making visible any charged particles set in motion by the interaction of neutrinos in the liquid

  17. Experimental investigation of shock wave - bubble interaction

    Energy Technology Data Exchange (ETDEWEB)

    Alizadeh, Mohsen

    2010-04-09

    In this work, the dynamics of laser-generated single cavitation bubbles exposed to lithotripter shock waves has been investigated experimentally. The energy of the impinging shock wave is varied in several steps. High-speed photography and pressure field measurements simultaneously with image acquisition provide the possibility of capturing the fast bubble dynamics under the effect of the shock wave impact. The pressure measurement is performed using a fiber optic probe hydrophone (FOPH) which operates based on optical diagnostics of the shock wave propagating medium. After a short introduction in chapter 1 an overview of the previous studies in chapter 2 is presented. The reported literatures include theoretical and experimental investigations of several configurations of physical problems in the field of bubble dynamics. In chapter 3 a theoretical description of propagation of a shock wave in a liquid like water has been discussed. Different kinds of reflection of a shock wave at an interface are taken into account. Undisturbed bubble dynamics as well as interaction between a planar shock wave and an initially spherical bubble are explored theoretically. Some physical parameters which are important in this issue such as the velocity of the shock-induced liquid jet, Kelvin impulse and kinetic energy are explained. The shock waves are generated in a water filled container by a focusing piezoelectric generator. The shock wave profile has a positive part with pulse duration of ∼1 μs followed by a longer tension tail (i.e. ∼3 μs). In chapter 4 high-speed images depict the propagation of a shock wave in the water filled tank. The maximum pressure is also derived for different intensity levels of the shock wave generator. The measurement is performed in the free field (i.e. in the absence of laser-generated single bubbles). In chapter 5 the interaction between lithotripter shock waves and laserinduced single cavitation bubbles is investigated experimentally. An

  18. Arrested Bubble Rise in a Narrow Tube

    Science.gov (United States)

    Lamstaes, Catherine; Eggers, Jens

    2017-05-01

    If a long air bubble is placed inside a vertical tube closed at the top it can rise by displacing the fluid above it. However, Bretherton found that if the tube radius, R, is smaller than a critical value Rc=0.918 ℓ _c, where ℓ _c=√{γ /ρ g} is the capillary length, there is no solution corresponding to steady rise. Experimentally, the bubble rise appears to have stopped altogether. Here we explain this observation by studying the unsteady bubble motion for Rmotion.

  19. The bubbling galactic plane: fertilization or sterilization?

    Science.gov (United States)

    Testi, Leonardo; Cunningham, Maria; Zavagno, Annie; Deharveng, Lise; Leurini, Silvia; Molinari, Sergio

    2010-04-01

    Spitzer surveys have revealed that the galactic plane has a high density of bubbles. Many of these show evidence of being associated with star formation. Followup observations collected so far have failed to conclusively determine the relationship (if any) between the bubbles and the triggering of star formation. We propose to obtain MOPRA molecular line pointed observations towards bubbles detected with APEX in the millimeter continuum and with Herschel in the far infrared/submm to reveal the presence and kinematics of dense gas and to search for evidence of the initial phases of star formation.

  20. Bubble Size Distributions on the North Atlantic and North Sea

    NARCIS (Netherlands)

    Leeuw, G. de; Cohen, L.H.

    2002-01-01

    Bubble size distributions were measured at open sea with optical bubble measuring systems(BMS)deployed from buoys at depths from 0.4 to l.5m. The BMS measures the bubbles in a small sample volume that is monitored with a video camera. The images are analyzed to obtain bubble size distributions in

  1. MARANGONI CONVECTION AROUND A VENTILATED AIR BUBBLE UNDER MICROGRAVITY CONDITIONS

    NARCIS (Netherlands)

    HOEFSLOOT, HCJ; JANSSEN, LPBM; HOOGSTRATEN, HW

    Under microgravity conditions in both parabolic and sounding rocket flights, the mass-transfer-induced Marangoni convection around an air bubble was studied. To prevent the bubble from becoming saturated, the bubble was ventilated. It turned out that the flow rate of the air through the bubble

  2. Stability of a bubble expanding and translating through an inviscid ...

    Indian Academy of Sciences (India)

    A bubble expands adiabatically and translates in an incompressible and inviscid liquid. We investigate the number of equilibrium points of the bubble and the nature of stability of the bubble at these points. We find that there is only one equilibrium point and the bubble is stable there.

  3. Approach to universality in axisymmetric bubble pinch-off

    NARCIS (Netherlands)

    Gekle, S.; Snoeijer, Jacobus Hendrikus; Lohse, Detlef; van der Meer, Roger M.

    2009-01-01

    The pinch-off of an axisymmetric air bubble surrounded by an inviscid fluid is compared in four physical realizations: (i) cavity collapse in the wake of an impacting disk, (ii) gas bubbles injected through a small orifice, (iii) bubble rupture in a straining flow, and (iv) a bubble with an

  4. 21 CFR 870.4205 - Cardiopulmonary bypass bubble detector.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Cardiopulmonary bypass bubble detector. 870.4205... bypass bubble detector. (a) Identification. A cardiopulmonary bypass bubble detector is a device used to detect bubbles in the arterial return line of the cardiopulmonary bypass circuit. (b) Classification...

  5. Stochastic DSMC method for dense bubbly flows : Methodology

    NARCIS (Netherlands)

    Kamath, S.; Padding, J.T.; Buist, K. A.; Kuipers, J.

    2018-01-01

    A stochastic Direct Simulation Monte Carlo (DSMC) method has been extended for handling bubble-bubble and bubble-wall collisions. Bubbly flows are generally characterized by highly correlated velocities due to presence of the surrounding liquid. The DSMC method has been improved to account for

  6. 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.

  7. Removal of dichloromethane from waste gas streams using a hybrid bubble column/biofilter bioreactor.

    Science.gov (United States)

    Abtahi, Mehrnoosh; Naddafi, Kazem; Mesdaghinia, Alireza; Yaghmaeian, Kamyar; Nabizadeh, Ramin; Jaafarzadeh, Nematollah; Rastkari, Noushin; Nazmara, Shahrokh; Saeedi, Reza

    2014-01-09

    The performance of a hybrid bubble column/biofilter (HBCB) bioreactor for the removal of dichloromethane (DCM) from waste gas streams was studied in continuous mode for several months. The HBCB bioreactor consisted of two compartments: bubble column bioreactor removing DCM from liquid phase and biofilter removing DCM from gas phase. Effect of inlet DCM concentration on the elimination capacity was examined in the DCM concentration range of 34-359 ppm with loading rates ranged from 2.2 to 22.8 g/m3.h and constant total empty bed retention time (EBRT) of 200 s. In the equal loading rates, the elimination capacity and removal efficiency of the biofilter were higher than the corresponding values of the bubble column bioreactor. The maximum elimination capacity of the HBCB bioreactor was determined to be 15.7 g/m3.h occurred in the highest loading rate of 22.8 g/m3.h with removal efficiency of 69%. The overall mineralization portion of the HBCB bioreactor was in the range of 72-79%. The mixed liquor acidic pH especially below 5.5 inhibited microbial activity and decreased the elimination capacity. Inhibitory effect of high ionic strength was initiated in the mixed liquor electrical conductivity of 12.2 mS/cm. This study indicated that the HBCB bioreactor could benefit from advantages of both bubble column and biofilter reactors and could remove DCM from waste gas streams in a better manner.

  8. IMPLEMENTATION OF SERIAL AND PARALLEL BUBBLE SORT ON FPGA

    Directory of Open Access Journals (Sweden)

    Dwi Marhaendro Jati Purnomo

    2016-06-01

    Full Text Available Sorting is common process in computational world. Its utilization are on many fields from research to industry. There are many sorting algorithm in nowadays. One of the simplest yet powerful is bubble sort. In this study, bubble sort is implemented on FPGA. The implementation was taken on serial and parallel approach. Serial and parallel bubble sort then compared by means of its memory, execution time, and utility which comprises slices and LUTs. The experiments show that serial bubble sort required smaller memory as well as utility compared to parallel bubble sort. Meanwhile, parallel bubble sort performed faster than serial bubble sort

  9. Time-Dependent Changes in a Shampoo Bubble

    Science.gov (United States)

    Chattopadhyay, Arun

    2000-10-01

    This article demonstrates the fascinating phenomenon of time evolution of a shampoo bubble through experiments that can be performed by undergraduate students. The changes in thickness of the bubble films with time are followed by UV-vis spectroscopy. The change in chemical composition as a bubble film evolves is monitored by FTIR spectroscopy. It is observed that the change in thickness of a typical shampoo bubble film enclosed in a container is gradual and slow, and the hydrocarbon components of the bubble drain from the bubble much more slowly than water. An additional agent, such as acetonitrile, strikingly alters the dynamics of evolution of such a bubble.

  10. Lattice Boltzmann Simulation of Multiple Bubbles Motion under Gravity

    Directory of Open Access Journals (Sweden)

    Deming Nie

    2015-01-01

    Full Text Available The motion of multiple bubbles under gravity in two dimensions is numerically studied through the lattice Boltzmann method for the Eotvos number ranging from 1 to 12. Two kinds of initial arrangement are taken into account: vertical and horizontal arrangement. In both cases the effects of Eotvos number on the bubble coalescence and rising velocity are investigated. For the vertical arrangement, it has been found that the coalescence pattern is similar. The first coalescence always takes place between the two uppermost bubbles. And the last coalescence always takes place between the coalesced bubble and the bottommost bubble. For four bubbles in a horizontal arrangement, the outermost bubbles travel into the wake of the middle bubbles in all cases, which allows the bubbles to coalesce. The coalescence pattern is more complex for the case of eight bubbles, which strongly depends on the Eotvos number.

  11. Import coal in the circulating fluidized bed plant of Stadtwerke Duisburg AG; Importkohleeinsatz in der zirkulierenden atmosphaerischen Wirbelschichtfeuerung des Heizkraftwerkes I der Stadtwerke Duisburg AG

    Energy Technology Data Exchange (ETDEWEB)

    Heidenhof, N.; Althoff, F.W. [Stadtwerke Duisburg AG (Germany)

    2003-07-01

    Since 1985 Stadtwerke Duisburg AG has operated a Circulating Fluidised Bed Plant (CFB). Because of the end of the so called 'Jahrhundertvertrag' (a special arrangement to promote national coal) more import coal is used than domestic coal. First tests indicated that besides the known parameters the handling of the ash particle erosion is of critical importance. A CFB plant requires sufficient circulating ash material. To properly examine new coals before the first burning a laboratory test called 'Ash Erosion Test' has been developed. This test allows to check the suitability of unknown coals in CFB plants. (orig.) [German] Neben den bekannten Parametern fuer die Beurteilung von Kohlen benoetigen Wirbelschichtfeuerungen zusaetzlich eine spezifische Information zur Beurteilung der Einsetzbarkeit. Der neue Parameter ist der Ascheabrieb. Die Stadtwerke Duisburg entwickelten ein Verfahren, mit dem man in der Lage ist, vor dem ersten Verbrennungsversuch in der ZAWSF festzustellen, ob die Kohlensorte umlauffaehiges Aschematerial erzeugt. (orig.)

  12. Optimization of the bubble radius in a moving single bubble sonoluminescence

    Energy Technology Data Exchange (ETDEWEB)

    Mirheydari, Mona; Sadighi-Bonabi, Rasoul; Rezaee, Nastaran; Ebrahimi, Homa, E-mail: sadighi@sharif.ir [Department of Physics, Sharif University of Technology, 11365-91, Tehran (Iran, Islamic Republic of)

    2011-05-01

    A complete study of the hydrodynamic force on a moving single bubble sonoluminescence in N-methylformamide is presented in this work. All forces exerted, trajectory, interior temperature and gas pressure are discussed. The maximum values of the calculated components of the hydrodynamic force for three different radii at the same driving pressure were compared, while the optimum bubble radius was determined. The maximum value of the buoyancy force appears at the start of bubble collapse, earlier than the other forces whose maximum values appear at the moment of bubble collapse. We verified that for radii larger than the optimum radius, the temperature peak value decreases.

  13. Chaotic behavior in bubble formation dynamics

    Science.gov (United States)

    Tufaile, A.; Sartorelli, J. C.

    2000-01-01

    We constructed an experimental apparatus to study the dynamics of the formation of air bubbles in a submerged nozzle in a water/glycerin solution inside a cylindrical tube. The delay time between successive bubbles was measured with a laser-photodiode system. It was observed bifurcations, chaotic behavior, and sudden changes in a periodic regime as a function of the decreasing air pressure in a reservoir. We also observed dynamical effects by applying a sound wave tuned to the fundamental frequency of the air column above the solution. As a function of the sound wave amplitude, we obtained a limit cycle, a flip bifurcation, chaotic behavior, and the synchronization of the bubbling with sound wave frequency. We related some of the different dynamical behaviors to coalescent effects and bubble sizes.

  14. Large bubble entrainment in drop impact

    Science.gov (United States)

    Thoraval, Marie-Jean; Li, Yangfan; Thoroddsen, Sigurdur T.

    2015-11-01

    A drop impacting on a pool of the same liquid can entrap air bubbles in many different ways. A peculiar entrapment was observed by Pumphrey and Elmore (1990) and remained unexplained until now. For a small range of parameters, the cavity produced by the impacting drop spreads radially in a dish-shape and then closes to entrap a bubble larger than the drop. We demonstrate that the large bubble is caused by a vortex ring produced in the liquid during the impact of the drop. We combine experiments and numerical simulations to show that the vortex ring pulls on the interface on the side of the cavity to stretch it radially, explaining the shape of the cavity. Only prolate drops are able to generate large bubbles. This is due to the self-destruction of the vortex earlier during the impact for flatter drops.

  15. On the shape of giant soap bubbles.

    Science.gov (United States)

    Cohen, Caroline; Darbois Texier, Baptiste; Reyssat, Etienne; Snoeijer, Jacco H; Quéré, David; Clanet, Christophe

    2017-03-07

    We study the effect of gravity on giant soap bubbles and show that it becomes dominant above the critical size [Formula: see text], where [Formula: see text] is the mean thickness of the soap film and [Formula: see text] is the capillary length ([Formula: see text] stands for vapor-liquid surface tension, and [Formula: see text] stands for the liquid density). We first show experimentally that large soap bubbles do not retain a spherical shape but flatten when increasing their size. A theoretical model is then developed to account for this effect, predicting the shape based on mechanical equilibrium. In stark contrast to liquid drops, we show that there is no mechanical limit of the height of giant bubble shapes. In practice, the physicochemical constraints imposed by surfactant molecules limit the access to this large asymptotic domain. However, by an exact analogy, it is shown how the giant bubble shapes can be realized by large inflatable structures.

  16. The Soap-Bubble-Geometry Contest.

    Science.gov (United States)

    Morgan, Frank; Melnick, Edward R.; Nicholson, Ramona

    1997-01-01

    Presents an activity on soap-bubble geometry using a guessing contest, explanations, and demonstrations that allow students to mesh observation and mathematical reasoning to discover that mathematics is much more than just number crunching. (ASK)

  17. TE Scattering From Bubbles In RAM

    National Research Council Canada - National Science Library

    Cochran, John

    1999-01-01

    ... (00) to 450 and at a frequency range from 2-18 GHz, TE polarization. The results from the absolute RCS measurement of the various sized RAM bubbles are discussed in terms of a frequency dependent increase in RCS...

  18. Test and evaluation of bubble memories

    Science.gov (United States)

    Bahm, E.

    1978-01-01

    A description is presented of a test program which has shown that well-constructed bubble memories can operate reliably over long periods of time and at low error rates. Even the relatively high error rate of one memory during burn-in can be considered acceptable if compared with tape recorder standards. No wear-out mechanism or aging could be detected. Bubble memories are now considered suitable for long-duration space missions and certainly are suitable for many military and commercial applications. It must be recognized, however, that bubble memories are complex devices and not yet fully understood. While the particular memory tested may never find practical applications, it nevertheless has provided insight into performance characteristics considered typical of bubble memories.

  19. Electron acceleration in the bubble regime

    Energy Technology Data Exchange (ETDEWEB)

    Jansen, Oliver

    2014-02-03

    The bubble regime of laser-wakefield acceleration has been studied over the recent years as an important alternative to classical accelerators. Several models and theories have been published, in particular a theory which provides scaling laws for acceleration parameters such as energy gain and acceleration length. This thesis deals with numerical simulations within the bubble regime, their comparison to these scaling laws and data obtained from experiments, as well as some specific phenomenona. With a comparison of the scaling laws with numerical results a parameter scan was able to show a large parameter space in which simulation and theory agree. An investigation of the limits of this parameter space revealed boundaries to other regimes, especially at very high (a{sub 0} > 100) and very low laser amplitudes (a{sub 0} < 4). Comparing simulation data with data from experiments concerning laser pulse development and electron energies, it was found that experimental results can be adequately reproduced using the Virtual-Laser-Plasma-Laboratory code. In collaboration with the Institut fuer Optik und Quantenelektronik at the Friedrich-Schiller University Jena synchrotron radiation emitted from the inside of the bubble was investigated. A simulation of the movement of the electrons inside the bubble together with time dependent histograms of the emitted radiation helped to prove that the majority of radiation created during a bubble acceleration originates from the inside of the bubble. This radiation can be used to diagnose the amplitude of oscillation of the trapped electrons. During a further study it was proven that the polarisation of synchrotron radiation from a bubble contains information about the exact oscillation direction. This oscillation was successfully controlled by using either a laser pulse with a tilted pulse front or an asymmetric laser pulse. First results of ongoing studies concerning injecting electrons into an existing bubble and a scheme called

  20. Experimental and computational studies of hydrodynamics in three-phase and two-phase fluidized beds

    Energy Technology Data Exchange (ETDEWEB)

    Bahary, M.

    1994-12-01

    The objective of the present study was to investigate the hydrodynamics of three-phase fluidized beds, their rheology, and experimentally verify a predictive three fluid hydrodynamic model developed at the Illinois Institute of Technology, Chicago. The recent reviews show that there exist no such models in the literature. The IIT hydrodynamic model computes the phase velocities and the volume fractions of gas, liquid, and particulate phases. Model verification involves a comparison of these computed velocities and volume fractions to experimental values. In this thesis, a three fluid model is presented. The input into the model can be particulate viscosities either measured with a Brookfield viscometer or derived using the mathematical techniques of kinetic theory of granular flows pioneered by Savage and others. The computer simulation of a three-phase fluidized bed in an asymmetric mode qualitatively predicts the gas, liquid and solid hold-ups (volume fractions) and flow patterns in the industrially important churn-turbulent (bubbly coalesced) regimes. The computations in a fluidized bed with a symmetric distributor incorrectly showed no bubble coalescence. A combination of X-ray and {gamma}-ray densitometers was used to measure the solids and the liquid volume fractions in a two dimensional bed in the bubble coalesced regime. There is a good agreement between the theory for an asymmetric distributor and the experiments.

  1. Numerical simulation of single bubble boiling behavior

    Directory of Open Access Journals (Sweden)

    Junjie Liu

    2017-06-01

    Full Text Available The phenomena of a single bubble boiling process are studied with numerical modeling. The mass, momentum, energy and level set equations are solved using COMSOL multi-physics software. The bubble boiling dynamics, the transient pressure field, velocity field and temperature field in time are analyzed, and reasonable results are obtained. The numeral model is validated by the empirical equation of Fritz and could be used for various applications.

  2. Test ventilation with smoke, bubbles, and balloons

    Energy Technology Data Exchange (ETDEWEB)

    Pickering, P.L.; Cucchiara, A.L.; McAtee, J.L.; Gonzales, M.

    1987-01-01

    The behavior of smoke, bubbles, and helium-filled balloons was videotaped to demonstrate the mixing of air in the plutonium chemistry laboratories, a plutonium facility. The air-distribution patterns, as indicated by each method, were compared. Helium-filled balloons proved more useful than bubbles or smoke in the visualization of airflow patterns. The replay of various segments of the videotape proved useful in evaluating the different techniques and in identifying airflow trends responsible for air mixing. 6 refs.

  3. Biomass ash-bed material interactions leading to agglomeration in FBC

    DEFF Research Database (Denmark)

    Visser, H.J.M.; van Lith, Simone Cornelia; Kiel, J.H.A.

    2008-01-01

    In (bubbling) fluidized-bed combustion and gasification of biomass, several potential problems are associated with the inorganic components of the fuel. A major problem area is defluidization due to bed agglomeration. The most common found process leading to defluidization in commercial-scale ins......In (bubbling) fluidized-bed combustion and gasification of biomass, several potential problems are associated with the inorganic components of the fuel. A major problem area is defluidization due to bed agglomeration. The most common found process leading to defluidization in commercial......-scale installations is "coating-induced" agglomeration. During reactor operation, a coating is formed on the surface of bed material grains and at certain critical conditions (e.g., coating thickness or temperature) sintering of the coatings initiates the agglomeration. In an experimental approach, this work...... describes a fundamental study on the mechanisms of defluidization. For the studied process of bed defluidization due to sintering of grain-coating layers, it was found that the onset of the process depends on (a) a critical coating thickness, (b) on the fluidization velocity when it is below approximately...

  4. Fluid dynamics of bubbles in liquid

    Directory of Open Access Journals (Sweden)

    C.M. SCHEID

    1999-12-01

    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.

  5. Gas Bubble Dynamics under Mechanical Vibrations

    Science.gov (United States)

    Mohagheghian, Shahrouz; Elbing, Brian

    2017-11-01

    The scientific community has a limited understanding of the bubble dynamics under mechanical oscillations due to over simplification of Navier-Stockes equation by neglecting the shear stress tensor and not accounting for body forces when calculating the acoustic radiation force. The current work experimental investigates bubble dynamics under mechanical vibration and resulting acoustic field by measuring the bubble size and velocity using high-speed imaging. The experimental setup consists of a custom-designed shaker table, cast acrylic bubble column, compressed air injection manifold and an optical imaging system. The mechanical vibrations resulted in accelerations between 0.25 to 10 times gravitational acceleration corresponding to frequency and amplitude range of 8 - 22Hz and 1 - 10mm respectively. Throughout testing the void fraction was limited to bubble size is larger than resonance size and smaller than acoustic wavelength. The amplitude of acoustic pressure wave was estimated using the definition of Bjerknes force in combination with Rayleigh-Plesset equation. Physical behavior of the system was capture and classified. Bubble size, velocity as well as size and spatial distribution will be presented.

  6. Fearless versus fearful speculative financial bubbles

    Science.gov (United States)

    Andersen, J. V.; Sornette, D.

    2004-06-01

    Using a recently introduced rational expectation model of bubbles, based on the interplay between stochasticity and positive feedbacks of prices on returns and volatility, we develop a new methodology to test how this model classifies nine time series that have been previously considered as bubbles ending in crashes. The model predicts the existence of two anomalous behaviors occurring simultaneously: (i) super-exponential price growth and (ii) volatility growth, that we refer to as the “fearful singular bubble” regime. Out of the nine time series, we find that five pass our tests and can be characterized as “fearful singular bubbles”. The four other cases are the information technology Nasdaq bubble and three bubbles of the Hang Seng index ending in crashes in 1987, 1994 and 1997. According to our analysis, these four bubbles have developed with essentially no significant increase of their volatility. This paper thus proposes that speculative bubbles ending in crashes form two groups hitherto unrecognized, namely those accompanied by increasing volatility (reflecting increasing risk perception) and those without change of volatility (reflecting an absence of risk perception).

  7. A Study of the Influence of Numerical Diffusion on Gas-Solid Flow Predictions in Fluidized Beds

    Science.gov (United States)

    Ghandriz, Ronak; Sheikhi, Reza

    2015-11-01

    In this work, an investigation is made of the influence of numerical diffusion on the accuracy of gas-solid flow predictions in fluidized beds. This is an important issue particularly in bubbling fluidized beds since numerical error greatly affects the dynamics of bubbles and their associated mixing process. A bed of coal (classified as Geldart A) is considered which becomes fluidized as the velocity of nitrogen stream into the reactor is gradually increased. The fluidization process is simulated using various numerical schemes as well as grid resolutions. Simulations involve Eulerian-Eulerian two-phase flow modeling approach and results are compared with experimental data. It is shown that higher order schemes equipped with flux limiter give favorable prediction of bubble and particle dynamics and hence, the mixing process within the reactor. The excessive numerical diffusion associated with lower order schemes results in unrealistic prediction of bubble shapes and bed height. Comparison is also made of computational efficiency of various schemes. It is shown that the Monotonized Central scheme with down wind factor results in the shortest simulation time because of its efficient parallelization on distributed memory platforms.

  8. Fluidized bed coal desulfurization

    Science.gov (United States)

    Ravindram, M.

    1983-01-01

    Laboratory scale experiments were conducted on two high volatile bituminous coals in a bench scale batch fluidized bed reactor. Chemical pretreatment and posttreatment of coals were tried as a means of enhancing desulfurization. Sequential chlorination and dechlorination cum hydrodesulfurization under modest conditions relative to the water slurry process were found to result in substantial sulfur reductions of about 80%. Sulfur forms as well as proximate and ultimate analyses of the processed coals are included. These studies indicate that a fluidized bed reactor process has considerable potential for being developed into a simple and economic process for coal desulfurization.

  9. Bed bug deterrence

    Directory of Open Access Journals (Sweden)

    Haynes Kenneth F

    2010-09-01

    Full Text Available Abstract A recent study in BMC Biology has determined that the immature stage of the bed bug (the nymph signals its reproductive status to adult males using pheromones and thus avoids the trauma associated with copulation in this species. The success of this nymphal strategy of deterrence is instructive. Against the background of increasing problems with bed bugs, this research raises the question whether pheromones might be used to control them. See research article http://www.biomedcentral.com/1741-7007/8/121

  10. The Scientometric Bubble Considered Harmful.

    Science.gov (United States)

    Génova, Gonzalo; Astudillo, Hernán; Fraga, Anabel

    2016-02-01

    This article deals with a modern disease of academic science that consists of an enormous increase in the number of scientific publications without a corresponding advance of knowledge. Findings are sliced as thin as salami and submitted to different journals to produce more papers. If we consider academic papers as a kind of scientific 'currency' that is backed by gold bullion in the central bank of 'true' science, then we are witnessing an article-inflation phenomenon, a scientometric bubble that is most harmful for science and promotes an unethical and antiscientific culture among researchers. The main problem behind the scenes is that the impact factor is used as a proxy for quality. Therefore, not only for convenience, but also based on ethical principles of scientific research, we adhere to the San Francisco Declaration on Research Assessment when it emphasizes "the need to eliminate the use of journal-based metrics in funding, appointment and promotion considerations; and the need to assess research on its own merits rather on the journal in which the research is published". Our message is mainly addressed to the funding agencies and universities that award tenures or grants and manage research programmes, especially in developing countries. The message is also addressed to well-established scientists who have the power to change things when they participate in committees for grants and jobs.

  11. Hydrodynamics of a hybrid circulating fluidized bed reactor with a partitioned loop seal system

    Energy Technology Data Exchange (ETDEWEB)

    Bae, Dal-Hee; Moon, Jong-Ho; Jin, Gyoung Tae; Shun, Dowon [Korea Institute of Energy Research, Daejeon (Korea, Republic of); Yun, Minyoung; Park, Chan Seung; Norbeck, Joseph M. [University of California, Riverside (United States)

    2015-07-15

    A circulating fluidized bed (CFB) with a hybrid design has been developed and optimized for steam hydrogasification. The hybrid CFB is composed of a bubbling fluidized bed (BFB) type combustor and a fast fluidized bed (FB) type gasifier. Char is burnt in the combustor and the generated heat is supplied to the gasifier along with the bed materials. Two different types of fluidized beds are connected to each other with a newly developed partitioned loop seal to avoid direct contact between two separate gas streams flowing in each fluidized bed. Gas mixing tests were carried out with Air and Argon in a cold model hybrid CFB to test the loop seal efficiency. Increase in solid inventory in the loop seal can improve the gas separation efficiency. It can be realized at higher gas velocity in fast bed and with higher solid inventory in the loop seal system. In addition, bed hydrodynamics was investigated with varying gas flow conditions and particle sizes in order to obtain a full understanding of changes of solid holdup in the FB. The solid holdup in the FB increased with increasing gas velocity in the BFB. Conversely, increase in gas velocity in the FB contributed to reducing the solid holdup in the FB. It was observed that changing the particle size of bed material does not have a big impact on hydrodynamic parameters.

  12. Carbon Shale Combustion in the Fluidized Bed Reactor

    Directory of Open Access Journals (Sweden)

    Olek Małgorzata

    2014-06-01

    Full Text Available The purpose of this article is to present the possibilities of coal shale combustion in furnaces with bubbling fluidized bed. Coal shale can be autothermally combusted in the fluidized bed, despite the low calorie value and high ash content of fuel. Established concentrations of CO (500 ppm and VOC (30 mg/m3 have indicated a high conversion degree of combustible material during combustion process. Average concentrations of SO2 and NOx in the flue gas were higher than this received from the combustion of high quality hard coal, 600 ppm and 500 ppm, respectively. Optional reduction of SO2 and NOx emission may require the installation of flue gas desulphurization and de-NOx systems.

  13. Bed Bug Myths

    Science.gov (United States)

    Learn the truth about bed bugs, such as how easy they are to see with the naked eye, their preferred habitat, whether they transmit diseases, their public health effects, and whether pesticides are the best way to deal with an infestation.

  14. Bubbles and semi-bubbles as a new kind of superheavy nuclei

    CERN Document Server

    Dechargé, J; Girod, M; Dietrich, K G

    2003-01-01

    Applying the HFB theory with the effective interaction D1S of Gogny, two kinds of 'hyperheavy nuclei' were discovered: true 'bubbles' with practically vanishing nuclear density in the central region of the nucleus, and 'semi-bubbles' ('unsaturated nuclei') with a reduced but finite density near the nuclear center. Semi-bubbles are found to be stable with regard to the emission of a neutron or a proton for nucleon numbers A and charge numbers Z in the ranges 292 < or approx. 750 and 120 < or approx. 240, and true bubbles for 750 < or approx. 920 and 240 < or approx. 280, respectively. For a limited number of nuclear species, a third type of hyperheavy nuclei with a finite, strongly reduced, halo-like central density ('internal halo nuclei') is found. Coexistence of bubble and semi-bubble solutions for given nucleon and charge numbers is frequently obtained, the semi-bubbles being the ground states for A < or approx. 240, and the true bubbles for the heavier nuclear species. The dominant disinteg...

  15. The importance of bubble deformability for strong drag reduction in bubbly turbulent Taylor-Couette flow

    NARCIS (Netherlands)

    van Gils, Dennis Paulus Maria; Narezo Guzman, Daniela; Sun, Chao; Lohse, Detlef

    2013-01-01

    Bubbly turbulent Taylor–Couette (TC) flow is globally and locally studied at Reynolds numbers of Re=5×105 to 2×106 with a stationary outer cylinder and a mean bubble diameter around 1 mm. We measure the drag reduction (DR) based on the global dimensional torque as a function of the global gas volume

  16. Dynamics and switching processes for magnetic bubbles in nanoelements

    Science.gov (United States)

    Moutafis, C.; Komineas, S.; Bland, J. A. C.

    2009-06-01

    We study numerically the dynamics of a magnetic bubble in a disk-shaped magnetic element which is probed by a pulse of a magnetic field gradient. Magnetic bubbles are nontrivial magnetic configurations which are characterized by a topological (skyrmion) number N and they have been observed in mesoscopic magnetic elements with strong perpendicular anisotropy. For weak fields we find a skew deflection of the axially symmetric N=1 bubble and a subsequent periodic motion around the center of the dot. This gyrotropic motion of the magnetic bubble is shown here for the first time. Stronger fields induce switching of the N=1 bubble to a bubble which contains a pair of Bloch lines and has N=0 . The N=0 bubble can be switched back to a N=1 bubble by applying again an external field gradient. Detailed features of the unusual bubble dynamics are described by employing the skyrmion number and the moments of the associated topological density.

  17. Energy, cost and design aspects of coarse- and fine-bubble aeration systems in the MBBR IFAS process.

    Science.gov (United States)

    Sander, S; Behnisch, J; Wagner, M

    2017-02-01

    With the MBBR IFAS (moving bed biofilm reactor integrated fixed-film activated sludge) process, the biomass required for biological wastewater treatment is either suspended or fixed on free-moving plastic carriers in the reactor. Coarse- or fine-bubble aeration systems are used in the MBBR IFAS process. In this study, the oxygen transfer efficiency (OTE) of a coarse-bubble aeration system was improved significantly by the addition of the investigated carriers, even in-process (∼1% per vol-% of added carrier material). In a fine-bubble aeration system, the carriers had little or no effect on OTE. The effect of carriers on OTE strongly depends on the properties of the aeration system, the volumetric filling rate of the carriers, the properties of the carrier media, and the reactor geometry. This study shows that the effect of carriers on OTE is less pronounced in-process compared to clean water conditions. When designing new carriers in order to improve their effect on OTE further, suppliers should take this into account. Although the energy efficiency and cost effectiveness of coarse-bubble aeration systems can be improved significantly by the addition of carriers, fine-bubble aeration systems remain the more efficient and cost-effective alternative for aeration when applying the investigated MBBR IFAS process.

  18. Convective mass transfer around a dissolving bubble

    Science.gov (United States)

    Duplat, Jerome; Grandemange, Mathieu; Poulain, Cedric

    2017-11-01

    Heat or mass transfer around an evaporating drop or condensing vapor bubble is a complex issue due to the interplay between the substrate properties, diffusion- and convection-driven mass transfer, and Marangoni effects, to mention but a few. In order to disentangle these mechanisms, we focus here mainly on the convective mass transfer contribution in an isothermal mass transfer problem. For this, we study the case of a millimetric carbon dioxide bubble which is suspended under a substrate and dissolved into pure liquid water. The high solubility of CO2 in water makes the liquid denser and promotes a buoyant-driven flow at a high (solutal) Rayleigh number (Ra˜104 ). The alteration of p H allows the concentration field in the liquid to be imaged by laser fluorescence enabling us to measure both the global mass flux (bubble volume, contact angle) and local mass flux around the bubble along time. After a short period of mass diffusion, where the boundary layer thickens like the square root of time, convection starts and the CO2 is carried by a plume falling at constant velocity. The boundary layer thickness then reaches a plateau which depends on the bubble cross section. Meanwhile the plume velocity scales like (dV /d t )1 /2 with V being the volume of the bubble. As for the rate of volume loss, we recover a constant mass flux in the diffusion-driven regime followed by a decrease in the volume V like V2 /3 after convection has started. We present a model which agrees well with the bubble dynamics and discuss our results in the context of droplet evaporation, as well as high Rayleigh convection.

  19. Scaling laws and dynamics of bubble coalescence

    Science.gov (United States)

    Anthony, Christopher R.; Kamat, Pritish M.; Thete, Sumeet S.; Munro, James P.; Lister, John R.; Harris, Michael T.; Basaran, Osman A.

    2017-08-01

    The coalescence of bubbles and drops plays a central role in nature and industry. During coalescence, two bubbles or drops touch and merge into one as the neck connecting them grows from microscopic to macroscopic scales. The hydrodynamic singularity that arises when two bubbles or drops have just touched and the flows that ensue have been studied thoroughly when two drops coalesce in a dynamically passive outer fluid. In this paper, the coalescence of two identical and initially spherical bubbles, which are idealized as voids that are surrounded by an incompressible Newtonian liquid, is analyzed by numerical simulation. This problem has recently been studied (a) experimentally using high-speed imaging and (b) by asymptotic analysis in which the dynamics is analyzed by determining the growth of a hole in the thin liquid sheet separating the two bubbles. In the latter, advantage is taken of the fact that the flow in the thin sheet of nonconstant thickness is governed by a set of one-dimensional, radial extensional flow equations. While these studies agree on the power law scaling of the variation of the minimum neck radius with time, they disagree with respect to the numerical value of the prefactors in the scaling laws. In order to reconcile these differences and also provide insights into the dynamics that are difficult to probe by either of the aforementioned approaches, simulations are used to access both earlier times than has been possible in the experiments and also later times when asymptotic analysis is no longer applicable. Early times and extremely small length scales are attained in the new simulations through the use of a truncated domain approach. Furthermore, it is shown by direct numerical simulations in which the flow within the bubbles is also determined along with the flow exterior to them that idealizing the bubbles as passive voids has virtually no effect on the scaling laws relating minimum neck radius and time.

  20. Modelling of NOx emissions from pressurized fluidized bed combustion - A parameter study

    DEFF Research Database (Denmark)

    Jensen, Anker; Johnsson, Jan Erik

    1997-01-01

    -1273 K, 20-30% of the fuel-N in the form of NH3 is oxidized catalytically to N-2 over bed material and so this reaction is important for a low conversion of fuel-N to NO. The importance of the homogeneous oxidation of NH3 to NO and reduction of NO by NH3 increases with increasing temperature....... The sensitivity of the simulated NO emission with respect to hydrodynamic and combustion parameters in the model is investigated and the mechanisms by which the parameters influence the emission of NO is explained. The analysis shows that the most important hydrodynamic parameters are the minimum fluidization...... velocity, the bubble size, the bubble rise velocity and the gas interchange coefficient between bubble and dense phase. The most important combustion parameters are the rates of CO and CH4 combustion and the CO/(CO + CO2) ratio from char combustion. (C) 1997 Elsevier Science Ltd....

  1. Financial Bubbles, Real Estate Bubbles, Derivative Bubbles, and the Financial and Economic Crisis

    Science.gov (United States)

    Sornette, Didier; Woodard, Ryan

    The financial crisis of 2008, which started with an initially well-defined epicenter focused on mortgage backed securities (MBS), has been cascading into a global economic recession, whose increasing severity and uncertain duration has led and is continuing to lead to massive losses and damage for billions of people. Heavy central bank interventions and government spending programs have been launched worldwide and especially in the USA and Europe, with the hope to unfreeze credit and bolster consumption. Here, we present evidence and articulate a general framework that allows one to diagnose the fundamental cause of the unfolding financial and economic crisis: the accumulation of several bubbles and their interplay and mutual reinforcement have led to an illusion of a "perpetual money machine" allowing financial institutions to extract wealth from an unsustainable artificial process. Taking stock of this diagnostic, we conclude that many of the interventions to address the so-called liquidity crisis and to encourage more consumption are ill-advised and even dangerous, given that precautionary reserves were not accumulated in the "good times" but that huge liabilities were. The most "interesting" present times constitute unique opportunities but also great challenges, for which we offer a few recommendations.

  2. Turbulence, aeration and bubble features of air-water flows over macro- and intermediate roughness

    Directory of Open Access Journals (Sweden)

    Stefano PAGLIARA

    2011-06-01

    Full Text Available Free surface flows in macro- and intermediate roughness conditions have a high aeration potential in which the flow characteristics vary with slopes and discharges. The underlying phenomenon of two phase flow characteristics in the macro and intermediate roughness conditions were analyzed in a setup assembled at the PITLAB center of the University of Pisa, Italy. Crushed angular rocks and hemispherical boulders were used to intensify the roughness nature of the bed. Flow discharges per unit width ranging between 0.03 m2/s and 0.09 m2/s and slopes between 0.26 and 0.46 were tested over different arrangements of rough bed. Analyses were mainly concentrated in the inner flow region which constitutes both bubbly and intermediate flow region. The findings revealed that two phase flow properties over rough bed were very much affected by the different rough bed arrangement. Turbulence features of two phase flows over rough beds were compared with that of the stepped chute data under similar flow conditions. Overall the results highlighted the flow features in the inner layers of the two phase flow.

  3. Research of bubble flow characteristics in microfluidic chip

    Science.gov (United States)

    Qiu, Chao; Cheng, Han; Chen, Shuxian

    2017-04-01

    Bubble is the heart of the microfluidic chip, which takes a significant role in drug release, biological detection and so on. In this case, bubble flow characteristics in microfluidic chip are the key to realize its function. In this paper, bubble flow characteristics in the microfluidic chip have been studied with high speed photography system by controlling the wettability and the heat flux of the microelectrode surface. The result shows that bubble flows faster on the electrode with hydrophobic surface. In addition, loading current to the electrode with hydrophilic surface could also speed up the movement of bubble, and the flow rate of bubble increases with the increasing heat flux of the electrode.

  4. Modeling the film condensate fluid dynamics and heat transfer within the bubble membrane radiator

    Energy Technology Data Exchange (ETDEWEB)

    Pauley, K.A. [Pacific Northwest Lab., Richland, WA (United States); Thornborrow, J.O. [National Aeronautics and Space Administration, Houston, TX (United States). Lyndon B. Johnson Space Center

    1992-01-01

    An analytical model of the fluid dynamics and heat transfer characteristics of the condensate within the rotating Bubble Membrane Radiator is developed. The steady-state, three-dimensional heat transfer and flow equations were reduced to a set of third-order ordinary differential equations by employing similarity transformation techniques. These equations are then solved for the radial, axial, and angular flow distributions in the film condensate. Pressure, temperature, heat transfer, film thickness and mass flow rate distributions are also calculated. The analytical model is the basis of the SCRABBLE code which is used both as a zero-g design tool and a ground-test bed analyzer.

  5. Herds of methane chambers grazing bubbles

    Science.gov (United States)

    Grinham, Alistair; Dunbabin, Matthew

    2014-05-01

    Water to air methane emissions from freshwater reservoirs can be dominated by sediment bubbling (ebullitive) events. Previous work to quantify methane bubbling from a number of Australian sub-tropical reservoirs has shown that this can contribute as much as 95% of total emissions. These bubbling events are controlled by a variety of different factors including water depth, surface and internal waves, wind seiching, atmospheric pressure changes and water levels changes. Key to quantifying the magnitude of this emission pathway is estimating both the bubbling rate as well as the areal extent of bubbling. Both bubbling rate and areal extent are seldom constant and require persistent monitoring over extended time periods before true estimates can be generated. In this paper we present a novel system for persistent monitoring of both bubbling rate and areal extent using multiple robotic surface chambers and adaptive sampling (grazing) algorithms to automate the quantification process. Individual chambers are self-propelled and guided and communicate between each other without the need for supervised control. They can maintain station at a sampling site for a desired incubation period and continuously monitor, record and report fluxes during the incubation. To exploit the methane sensor detection capabilities, the chamber can be automatically lowered to decrease the head-space and increase concentration. The grazing algorithms assign a hierarchical order to chambers within a preselected zone. Chambers then converge on the individual recording the highest 15 minute bubbling rate. Individuals maintain a specified distance apart from each other during each sampling period before all individuals are then required to move to different locations based on a sampling algorithm (systematic or adaptive) exploiting prior measurements. This system has been field tested on a large-scale subtropical reservoir, Little Nerang Dam, and over monthly timescales. Using this technique

  6. The stability of large oscillating bubbles

    Science.gov (United States)

    Blake, John; Pearson, Antony

    2002-11-01

    In a most remarkable paper, in October 1942, Penney & Price developed a theory for the stability of large oscillating bubbles; in their case they were interested in underwater explosions. Much of our current understanding on the stability of oscillating bubbles can be traced to the theoretical and experimental insight shown in this paper. While interest in this particular area continues with regard ship survivability to underwater explosions, other newer areas include the oscillatory behaviour of of seismic airgun generated bubbles. Apart from large volume oscillations with a characteristic period, the other dominant parameter is associated with buoyancy. An appropriate parameter is chosen that provides a measure of the distance of migration of a bubble over one period. An analytical and computational analysis of this class of problem reveals that this pressure gradient driven instability, normally observed in the form of a high speed liquid jet threading the bubble, is the most dominant surface instability, a characteristic feature borne out in most experimental and practical applications due to the presence of an incipient pressure gradient associated with hydrostatics, dynamics or boundaries

  7. Argonne Bubble Experiment Thermal Model Development III

    Energy Technology Data Exchange (ETDEWEB)

    Buechler, Cynthia Eileen [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2018-01-11

    This report describes the continuation of the work reported in “Argonne Bubble Experiment Thermal Model Development” and “Argonne Bubble Experiment Thermal Model Development II”. The experiment was performed at Argonne National Laboratory (ANL) in 2014. A rastered 35 MeV electron beam deposited power in a solution of uranyl sulfate, generating heat and radiolytic gas bubbles. Irradiations were performed at beam power levels between 6 and 15 kW. Solution temperatures were measured by thermocouples, and gas bubble behavior was recorded. The previous report2 described the Monte-Carlo N-Particle (MCNP) calculations and Computational Fluid Dynamics (CFD) analysis performed on the as-built solution vessel geometry. The CFD simulations in the current analysis were performed using Ansys Fluent, Ver. 17.2. The same power profiles determined from MCNP calculations in earlier work were used for the 12 and 15 kW simulations. The primary goal of the current work is to calculate the temperature profiles for the 12 and 15 kW cases using reasonable estimates for the gas generation rate, based on images of the bubbles recorded during the irradiations. Temperature profiles resulting from the CFD calculations are compared to experimental measurements.

  8. Drop impact entrapment of bubble rings

    KAUST Repository

    Thoraval, M.-J.

    2013-04-29

    We use ultra-high-speed video imaging to look at the initial contact of a drop impacting on a liquid layer. We observe experimentally the vortex street and the bubble-ring entrapments predicted numerically, for high impact velocities, by Thoraval et al. (Phys. Rev. Lett., vol. 108, 2012, article 264506). These dynamics mainly occur within 50 -s after the first contact, requiring imaging at 1 million f.p.s. For a water drop impacting on a thin layer of water, the entrapment of isolated bubbles starts through azimuthal instability, which forms at low impact velocities, in the neck connecting the drop and pool. For Reynolds number Re above -12 000, up to 10 partial bubble rings have been observed at the base of the ejecta, starting when the contact is -20% of the drop size. More regular bubble rings are observed for a pool of ethanol or methanol. The video imaging shows rotation around some of these air cylinders, which can temporarily delay their breakup into micro-bubbles. The different refractive index in the pool liquid reveals the destabilization of the vortices and the formation of streamwise vortices and intricate vortex tangles. Fine-scale axisymmetry is thereby destroyed. We show also that the shape of the drop has a strong influence on these dynamics. 2013 Cambridge University Press.

  9. The Quest for the Most Spherical Bubble

    CERN Document Server

    Obreschkow, Danail; Dorsaz, Nicolas; Kobel, Philippe; de Bosset, Aurele; Farhat, Mohamed

    2013-01-01

    We describe a recently realized experiment producing the most spherical cavitation bubbles today. The bubbles grow inside a liquid from a point-plasma generated by a nanosecond laser pulse. Unlike in previous studies, the laser is focussed by a parabolic mirror, resulting in a plasma of unprecedented symmetry. The ensuing bubbles are sufficiently spherical that the hydrostatic pressure gradient caused by gravity becomes the dominant source of asymmetry in the collapse and rebound of the cavitation bubbles. To avoid this natural source of asymmetry, the whole experiment is therefore performed in microgravity conditions (ESA, 53rd and 56th parabolic flight campaign). Cavitation bubbles were observed in microgravity (~0g), where their collapse and rebound remain spherical, and in normal gravity (1g) to hyper-gravity (1.8g), where a gravity-driven jet appears. Here, we describe the experimental setup and technical results, and overview the science data. A selection of high-quality shadowgraphy movies and time-res...

  10. Bubble growth in a narrow horizontal space

    Energy Technology Data Exchange (ETDEWEB)

    Stutz, Benoit; Goulet, Remi [CETHIL, UMR5008, CNRS, INSA-Lyon, Universite Lyon1 (France); Passos, Julio Cesar [Universidade Federal de Santa Catarina (UFSC), Florianopolis, SC (Brazil). Dept. de Engenharia Mecanica. LABSOLAR

    2009-07-01

    The purpose of this work is to develop an axis-symmetric two-phase flow model describing the growth of a single bubble squeezed between a horizontal heated upward-facing disc and an insulating surface placed parallel to the heated surface. Heat transfers at the liquid-vapour interfaces are predicted by the kinetic limit of vaporisation. The depths of the liquid films deposed on the surfaces (heated surface and confinement space) are determined using the Moriyama and Inoue correlation (1996). Transient heat transfers within the heated wall are taken into account. The model is applied to pentane bubble growth. The influence of the gap size, the initial temperature of the system, the thermal effusivity of the heated wall and the kinetic limit of vaporisation are studied. The results show that the expansion of the bubbles strongly depends on the gap size and can be affected by the effusivity of the material. Mechanical inertia effects are mainly dominant at the beginning of the bubble expansion. Pressure drop induced by viscous effects have to be taken into account for high capillary numbers. Heat transfers at the meniscus are negligible except at the early stages of the bubble growth. (author)

  11. Ash and heavy metals in fluidized bed-combustion; Tuhka ja raskasmetallit puuperaeisen jaetteen kerrosleijupoltossa

    Energy Technology Data Exchange (ETDEWEB)

    Kaessi, T.; Aittoniemi, P. [IVO International, Vantaa (Finland)

    1996-12-01

    Combustion ashes and submicron fly ash particles were characterized in two industrial boilers (bubbling vs. circulating fluidized bed) burning paper mill deinking sludge and bark or wood as support fuel. Bulk samples from fly ash, circulating ash and bottom ash were analyzed. Fine particles in fly ash were monitored and sampled for microscopic studies. The mass size distribution of fly ash was measured and the chemical composition according to particle size was analyzed. The results showed that ash consists of large and friable clusters formed by sintering of small mineral particles originating from paper fillers. Very few ash particles were fused and they were found only among the smallest particles. No agglomerates of fused particles were found. If the residence time in furnace is long enough sintering may proceed further and ash structure grows more dense. No indication of ash vaporization was detected. These results were similar for bubbling and circulating fluidized bed boilers. (author)

  12. VA National Bed Control System

    Data.gov (United States)

    Department of Veterans Affairs — The VA National Bed Control System records the levels of operating, unavailable and authorized beds at each VAMC, and it tracks requests for changes in these levels....

  13. 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

  14. Scale-up guidelines for a circulating fluidized bed biomass pyrolyzer

    Energy Technology Data Exchange (ETDEWEB)

    Haslinger, W.; Hofbauer, H. [Technische Univ., Vienna (Austria); Gavriil, L.; Boukis, I. [Center for Renewable Energy Sources (Greece)

    1999-07-01

    A new circulating fluidized bed design has been proposed and successfully operated at lab scale (10 kg/h biomass feed). This fluidized bed system consists of a bubbling bottom bed, above this bottom bed a riser, a cyclone and a return leg. The heat necessary for the pyrolysis process is produced in the bottom bed by burning some solid residue from the pyrolysis that circulates together with the bed material as the bottom bed is fluidized with air. The flue gas from the bottom bed enters into the riser and serves there as transport gas. The circulation rate is very sensitive to the amount of bed inventory and the fluidization velocities. As the riser uses the flue gas of the dense bottom bed the ratio of the cross sections of the two fluidized beds has to be in a certain range to get a satisfying operation. The fluid mechanic behavior of this new circulating fluidized bed pyrolyzer has been studied using three different cold flow models. One cold flow model was built for the existing 10 kg/h lab scale pyrolyzer according to Glicksman's (1984) similarity rules. The purpose of this cold model was to study the fluid mechanics and optimize the performance with respect to the pyrolysis process. For scale-up purposes further cold flow models (135 kg/h, 1000 kg/h) have been designed, built and investigated intensively. The idea and the new design of the pyrolyzer, the results of the experimental work as well as the scale-up criteria will be presented. (orig.)

  15. CIRCULATING MOVING BED COMBUSTION PROOF OF CONCEPT

    Energy Technology Data Exchange (ETDEWEB)

    Jukkola, Glen

    2010-06-30

    Circulating Moving Bed (CMB) combustion technology has its roots in traditional circulating fluidized bed technology and involves a novel method of solid fuel combustion and heat transfer. CMB technology represents a step change in improved performance and cost relative to conventional PC and FBC boilers. The CMB heat exchanger preheats the energy cycle working fluid, steam or air, to the high temperature levels required in systems for advanced power generation. Unique features of the CMB are the reduction of the heat transfer surfaces by about 60% as a result of the enhanced heat transfer rates, flexibility of operation, and about 30% lower cost over existing technology. The CMB Phase I project ran from July 2001 through March 2003. Its objective was to continue development of the CMB technology with a series of proof of concept tests. The tests were conducted at a scale that provided design data for scale up to a demonstration plant. These objectives were met by conducting a series of experiments in ALSTOM Power’s Multi-use Test Facility (MTF). The MTF was modified to operate under CMB conditions of commercial interest. The objective of the tests were to evaluate gas-to-solids heat transfer in the upper furnace, assess agglomeration in the high temperature CMB bubbling bed, and evaluate solids-to-tube heat transfer in the moving bed heat exchanger. The Phase I program results showed that there are still some significant technical uncertainties that needed to be resolved before the technology can be confidently scaled up for a successful demonstration plant design. Work remained in three primary areas: • scale up of gas to solid heat transfer • high temperature finned surface design • the overall requirements of mechanical and process design. The CMB Phase II workscope built upon the results of Phase I and specifically addressed the remaining technical uncertainties. It included a scaled MTF heat transfer test to provide the necessary data to scale up gas

  16. Bed Prism Spectacles

    Science.gov (United States)

    Ribeiro, Jair Lúcio Prados

    2018-01-01

    We only became aware of the existence of bed prism spectacles when a student brought them to the classroom and asked us about how they work. The device proved to be a fertile source of curiosity among the students, and, to be properly understood, it required us to develop a comparison between reflection in a typical mirror and total internal reflection in a prism. In this article we explain the physics behind this unfamiliar device, supported by geometrical optics principles.

  17. Bed agglomeration in fluidized combustor fueled by wood and rice straw blends

    Energy Technology Data Exchange (ETDEWEB)

    Thy, P.; Lesher, C.E. [Department of Geology, University of California, One Shields Avenue, Davis, CA 95616 (United States); Jenkins, B.M.; Williams, R.B. [Department of Biological and Agricultural Engineering, University of California, One Shields Avenue, Davis, CA 95616 (United States); Bakker, R.R. [Wageningen University and Research Centre, Agrotechnology and Food Sciences Group, Postbus 17, 6700 AA Wageningen (Netherlands)

    2010-11-15

    Petrographic techniques have been used to examine bed materials from fluidized bed combustion experiments that utilized wood and rice straw fuel blends. The experiments were conducted using a laboratory-scale combustor with mullite sand beds, firing temperatures of 840 to 1030 C, and run durations of 5.5 h. A narrow continuous zone borders virtually all bed particles. The highest concentrations of potassium are found in this surface zone that also is enriched in appreciable amounts of other elements. Thin discontinuous films of adhesive cement, formed preferentially on surfaces and contact areas between bed particles, ultimately led to bed agglomeration. The interfaces and the presence of gas bubbles in the cement suggest a bonding material with a high surface tension and a liquid state. The cement films originate by filling of irregularities on individual and partially agglomerated bed particle surfaces by accumulation of liquid droplets preferentially in areas sheltered from turbulence and mechanical interaction. The composition of the film suggests melting of locally accumulated dust or aerosol mixture of ash particles and mullite. The film only locally enlarged bed particles. Large straw ash particles appear to have mostly been passively incorporated into the adhesive melt without melting or reaction. (author)

  18. High energy neutrinos from the Fermi bubbles.

    Science.gov (United States)

    Lunardini, Cecilia; Razzaque, Soebur

    2012-06-01

    Recently the Fermi-LAT data have revealed two gamma-ray emitting bubble-shaped structures at the Galactic center. If the observed gamma rays have hadronic origin (collisions of accelerated protons), the bubbles must emit high energy neutrinos as well. This new, Galactic, neutrino flux should trace the gamma-ray emission in spectrum and spatial extent. Its highest energy part, above 20-50 TeV, is observable at a kilometer-scale detector in the northern hemisphere, such as the planned KM3NeT, while interesting constraints on it could be obtained by the IceCube Neutrino Observatory at the South Pole. The detection or exclusion of neutrinos from the Fermi bubbles will discriminate between hadronic and leptonic models, thus bringing unique information on the still mysterious origin of these objects and on the time scale of their formation.

  19. Root Causes of the Housing Bubble

    Science.gov (United States)

    Kaizoji, Taisei

    In this chapter we investigate root causes of the recent US housing bubble which has been caused a serious downturn in US economic growth since autumn of 2008. We propose a simple model of housing markets in order to indicate the possible determinants of recent housing prices. Utilizing the model, we verify a number of hypotheses which have been proposed in the recent literature on the housing bubbles. We suggest that the main causes of the housing bubble from 2000 to 2006 are (1) non-elastic housing supply in the metropolitan areas, and (2) declines in the mortgage loan rate and the housing premium by the massive mortgage credit expansion. We also suggest that these factors were strongly influenced by policies that governments and the Federal Reserve Board performed.

  20. Toward a Metatheory of Economic Bubbles

    DEFF Research Database (Denmark)

    Dholakia, Nikhilesh; Turcan, Romeo V.

    Dholakia and Turcan present their interdisciplinary metatheory of bubbles with short case studies of minor and major bubbles. They comprehensively identify and exemplify constructs of the theory, set its temporal and contextual boundaries, and examine the underlying economic, psychological......, and social dynamics assumptions, explaining how these elements are related. By doing so, they provide a partial window into the precarious nature of contemporary finance-driven capitalism and suggest some possible ways of overcoming the wrenching ups and downs of the prevalent system. The case studies...... and original research in Toward a Metatheory of Economic Bubbles have far-reaching implications for the study and practice of entrepreneurship and marketing, public and corporate finance, and public policies towards innovation, economy, and finance. It contributes to the defining issues for economic sociology...

  1. Rational speculative bubbles: A critical view

    Directory of Open Access Journals (Sweden)

    Radonjić Ognjen

    2007-01-01

    Full Text Available According to the theory of rational bubbles, the bubble is present whenever asset prices progressively diverge from their fundamental value, which occurs because agents expect that asset prices will continue to grow exponentially (self-fulfilling prophecies far in the future and consistently, which promises the realization of ever larger capital gains. In our opinion, the basic shortcoming of this theory refers to the assumption that all market agents are perfectly informed and rational and, accordingly, form homogeneous expectations. The model does not explain decision-making processes or expectation formation, nor does it detect potential psychological and institutional factors that might significantly influence decision making processes and market participants’ reactions to news. Since assumptions of the model critically determine its validity, we conclude that comprehensiveness of the rational bubble model is, to put it mildly, limited.

  2. Bubbles, shocks and elementary technical trading strategies

    Science.gov (United States)

    Fry, John

    2014-01-01

    In this paper we provide a unifying framework for a set of seemingly disparate models for bubbles, shocks and elementary technical trading strategies in financial markets. Markets operate by balancing intrinsic levels of risk and return. This seemingly simple observation is commonly over-looked by academics and practitioners alike. Our model shares its origins in statistical physics with others. However, under our approach, changes in market regime can be explicitly shown to represent a phase transition from random to deterministic behaviour in prices. This structure leads to an improved physical and econometric model. We develop models for bubbles, shocks and elementary technical trading strategies. The list of empirical applications is both interesting and topical and includes real-estate bubbles and the on-going Eurozone crisis. We close by comparing the results of our model with purely qualitative findings from the finance literature.

  3. Topological vacuum bubbles by anyon braiding.

    Science.gov (United States)

    Han, Cheolhee; Park, Jinhong; Gefen, Yuval; Sim, H-S

    2016-03-31

    According to a basic rule of fermionic and bosonic many-body physics, known as the linked cluster theorem, physical observables are not affected by vacuum bubbles, which represent virtual particles created from vacuum and self-annihilating without interacting with real particles. Here we show that this conventional knowledge must be revised for anyons, quasiparticles that obey fractional exchange statistics intermediate between fermions and bosons. We find that a certain class of vacuum bubbles of Abelian anyons does affect physical observables. They represent virtually excited anyons that wind around real anyonic excitations. These topological bubbles result in a temperature-dependent phase shift of Fabry-Perot interference patterns in the fractional quantum Hall regime accessible in current experiments, thus providing a tool for direct and unambiguous observation of elusive fractional statistics.

  4. Moving with bubbles: a review of the interactions between bubbles and the microorganisms that surround them.

    Science.gov (United States)

    Walls, Peter L L; Bird, James C; Bourouiba, Lydia

    2014-12-01

    Bubbles are ubiquitous in biological environments, emerging during the complex dynamics of waves breaking in the open oceans or being intentionally formed in bioreactors. From formation, through motion, until death, bubbles play a critical role in the oxygenation and mixing of natural and artificial ecosystems. However, their life is also greatly influenced by the environments in which they emerge. This interaction between bubbles and microorganisms is a subtle affair in which surface tension plays a critical role. Indeed, it shapes the role of bubbles in mixing or oxygenating microorganisms, but also determines how microorganisms affect every stage of the bubble's life. In this review, we guide the reader through the life of a bubble from birth to death, with particular attention to the microorganism-bubble interaction as viewed through the lens of fluid dynamics. © The Author 2014. Published by Oxford University Press on behalf of the Society for Integrative and Comparative Biology. All rights reserved. For permissions please email: journals.permissions@oup.com.

  5. "Bubble-on-demand" generator with precise adsorption time control.

    Science.gov (United States)

    Zawala, J; Niecikowska, A

    2017-09-01

    The paper presents the principles of our new single bubble generator, which allows a precise control of bubble formation in pure liquids and surfactant solutions, i.e., their detachment frequency and the adsorption time at their motionless surface. We show that the bubbles with equilibrium size can be produced at the capillaries of various orifice diameters (0.022-0.128 mm) on demand and with outstanding reproducibility. Moreover, it is shown that a fully automatized and programmable bubble trap, synchronized with bubble detachment frequency, can be used to (i) control the radius of the released bubble and (ii) precisely adjust the initial adsorption coverage over the surface of detaching bubble, and hence to study the influence of adsorption coverage degree on kinetics of dynamic adsorption layer formation at the rising bubble surface.

  6. Simulations of Bubble Motion in an Oscillating Liquid

    Science.gov (United States)

    Kraynik, A. M.; Romero, L. A.; Torczynski, J. R.

    2010-11-01

    Finite-element simulations are used to investigate the motion of a gas bubble in a liquid undergoing vertical vibration. The effect of bubble compressibility is studied by comparing "compressible" bubbles that obey the ideal gas law with "incompressible" bubbles that are taken to have constant volume. Compressible bubbles exhibit a net downward motion away from the free surface that does not exist for incompressible bubbles. Net (rectified) velocities are extracted from the simulations and compared with theoretical predictions. The dependence of the rectified velocity on ambient gas pressure, bubble diameter, and bubble depth are in agreement with the theory. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  7. "Bubble-on-demand" generator with precise adsorption time control

    Science.gov (United States)

    Zawala, J.; Niecikowska, A.

    2017-09-01

    The paper presents the principles of our new single bubble generator, which allows a precise control of bubble formation in pure liquids and surfactant solutions, i.e., their detachment frequency and the adsorption time at their motionless surface. We show that the bubbles with equilibrium size can be produced at the capillaries of various orifice diameters (0.022-0.128 mm) on demand and with outstanding reproducibility. Moreover, it is shown that a fully automatized and programmable bubble trap, synchronized with bubble detachment frequency, can be used to (i) control the radius of the released bubble and (ii) precisely adjust the initial adsorption coverage over the surface of detaching bubble, and hence to study the influence of adsorption coverage degree on kinetics of dynamic adsorption layer formation at the rising bubble surface.

  8. Cavitation Bubble Dynamics in Ammoniacal Fluids Transferred by Centrifugal Pumps

    Directory of Open Access Journals (Sweden)

    Jorge Reyes-Cruz

    2016-10-01

    Full Text Available An experiment with water and ammoniacal liquor at 27% and 34% concentrations of ammonia was carried out in order to determine the pressure dynamics during the formation of bubbles and their movement when causing cavitations in centrifugal pumps. The dynamics of bubbles was calculated numerically by applying the Rayleigh-Plesset equation using the bubble radius and the bubble build-up time. It is concluded that the pressure to form the bubbles at 22 ºC is 10,135.103 Pa for water and 45,468.103 Pa for the ammoniacal liquor at a concentration of 34 %. The radius of the bubbles found in ammoniacal liquor is in the range of 30 to 120 times the original bubble radius while the bubbles formed in water are only in the range of 15 times the original radius value.

  9. Bubble Dynamics in a Two-Phase Medium

    CERN Document Server

    Jayaprakash, Arvind; Chahine, Georges

    2010-01-01

    The spherical dynamics of a bubble in a compressible liquid has been studied extensively since the early work of Gilmore. Numerical codes to study the behavior, including when large non-spherical deformations are involved, have since been developed and have been shown to be accurate. The situation is however different and common knowledge less advanced when the compressibility of the medium surrounding the bubble is provided mainly by the presence of a bubbly mixture. In one of the present works being carried out at DYNAFLOW, INC., the dynamics of a primary relatively large bubble in a water mixture including very fine bubbles is being investigated experimentally and the results are being provided to several parallel on-going analytical and numerical approaches. The main/primary bubble is produced by an underwater spark discharge from two concentric electrodes placed in the bubbly medium, which is generated using electrolysis. A grid of thin perpendicular wires is used to generate bubble distributions of vary...

  10. A note on effects of rational bubble on portfolios

    Science.gov (United States)

    Wang, Chan; Nie, Pu-yan

    2018-02-01

    In general, demand increases in wealth and decreases in price in microeconomics. We thereby propose a completely different perspective. By establishing expected utility function of investors, this article introduces one rational bubble asset and one bubble free asset in portfolios and focuses on the effects of bubble on investment portfolios from wealth and price perspectives. All conclusions are obtained by theoretical analysis with microeconomics theory. We argue that inferior goods and Giffen behavior can occur for the bubble free asset in microeconomic fields. The results can help investors to recognize bubble assets and bubble free assets more scientifically. Both bubble and bubble free assets can be inferior goods under some conditions, so we cannot to say which asset better than the other one absolutely.

  11. Surface magnetostatic oscillations in elliptical bubble domains

    Science.gov (United States)

    Popov, M. A.; Zavislyak, I. V.

    2009-01-01

    A theory of surface magnetostatic oscillations in magnetic bubble domains with an elliptical cross section is presented. The dependences of the eigenfrequencies of resonant modes on the applied magnetic field are analyzed for a barium hexaferrite sample with allowance made for the change in the domain size due to a variation in the bias magnetic field. The range of frequency tuning in response to a magnetic field ranging from the elliptical instability field to the collapse field is estimated. It is demonstrated that elliptical bubble domains can be used as microminiature resonators operating in the millimeter range.

  12. Partial coalescence from bubbles to drops

    KAUST Repository

    Zhang, F. H.

    2015-10-07

    The coalescence of drops is a fundamental process in the coarsening of emulsions. However, counter-intuitively, this coalescence process can produce a satellite, approximately half the size of the original drop, which is detrimental to the overall coarsening. This also occurs during the coalescence of bubbles, while the resulting satellite is much smaller, approximately 10 %. To understand this difference, we have conducted a set of coalescence experiments using xenon bubbles inside a pressure chamber, where we can continuously raise the pressure from 1 up to 85 atm and thereby vary the density ratio between the inner and outer fluid, from 0.005 up to unity. Using high-speed video imaging, we observe a continuous increase in satellite size as the inner density is varied from the bubble to emulsion-droplet conditions, with the most rapid changes occurring as the bubble density grows up to 15 % of that of the surrounding liquid. We propose a model that successfully relates the satellite size to the capillary wave mode responsible for its pinch-off and the overall deformations from the drainage. The wavelength of the primary wave changes during its travel to the apex, with the instantaneous speed adjusting to the local wavelength. By estimating the travel time of this wave mode on the bubble surface, we also show that the model is consistent with the experiments. This wavenumber is determined by both the global drainage as well as the interface shapes during the rapid coalescence in the neck connecting the two drops or bubbles. The rate of drainage is shown to scale with the density of the inner fluid. Empirically, we find that the pinch-off occurs when 60 % of the bubble fluid has drained from it. Numerical simulations using the volume-of-fluid method with dynamic adaptive grid refinement can reproduce these dynamics, as well as show the associated vortical structure and stirring of the coalescing fluid masses. Enhanced stirring is observed for cases with second

  13. Impact of money supply on stock bubbles

    Directory of Open Access Journals (Sweden)

    Martin Širůček

    2013-01-01

    Full Text Available This article focuses on the effect and implications of changes in money supply in the US on stock bubble rise on the US capital market, which is represented by the Dow Jones Industrial Average index. This market was chosen according to the market capitalization. The attention of the paper is drawn to issues – if according to the results of empirical analysis, the money supply is a significant factor which causes the bubbles and if during the time the significance and impact of this macroeconomic factor on stock index increase.

  14. On the maximum drawdown during speculative bubbles

    Science.gov (United States)

    Rotundo, Giulia; Navarra, Mauro

    2007-08-01

    A taxonomy of large financial crashes proposed in the literature locates the burst of speculative bubbles due to endogenous causes in the framework of extreme stock market crashes, defined as falls of market prices that are outlier with respect to the bulk of drawdown price movement distribution. This paper goes on deeper in the analysis providing a further characterization of the rising part of such selected bubbles through the examination of drawdown and maximum drawdown movement of indices prices. The analysis of drawdown duration is also performed and it is the core of the risk measure estimated here.

  15. Stochastic modelling for financial bubbles and policy

    Directory of Open Access Journals (Sweden)

    John Fry

    2015-12-01

    Full Text Available In this paper, we draw upon the close relationship between statistical physics and mathematical finance to develop a suite of models for financial bubbles and crashes. By modifying previous approaches, we are able to derive novel analytical formulae for evaluation problems and for the expected timing of future change points. In particular, we help to explain why previous approaches have systematically overstated the timing of changes in market regime. The list of potential empirical applications is deep and wide ranging, and includes contemporary housing bubbles, the Eurozone crisis and the Crash of 2008.

  16. Intraalveolar bubbles and bubble films: III. Vulnerability and preservation in the laboratory.

    Science.gov (United States)

    Scarpelli, E M; Mautone, A J; Chinoy, M R; Defouw, D O; Clutario, B C

    1997-08-01

    Having confirmed (Scarpelli et al. 1996. Anat. Rec. 244:344-357 and 246:245-270) the discovery of intraalveolar bubbles and films as the normal anatomical infrastructure of aerated alveoli at all ages, we now address three questions. Why have these structures been so elusive? Visible in fresh lungs from the in vivo state, can they be preserved by known laboratory methods? Can they be preserved intact for study in tissue sections? Lungs of adult rabbits and pups were examined in thorax directly from the in vivo state to confirm normal bubbles both at functional residual capacity and at maximal volume; other lungs were permitted to deflate naturally to minimal volume. The fate of bubbles in situ (either intact, transected, or diced lung tissue) and of isolated bubbles was assessed (1) during conventional histopreparative processing, (2) during inflation-deflation after degassing, (3) after drying in air, (4) during and after quick freezing in liquid N2, and (5) after preservation in fixed and stained tissue sections prepared by a new double-impregnation procedure in which glutaraldehyde-fixed tissue was preembedded in agar, dehydrated and clarified chemically, embedded in paraffin, sectioned, and stained. Control studies included both blocking of bubble formation by rinsing the air spaces with Tween 20 prior to double impregnation and preparation of normal tissue without preembedding in agar. (1) Each of the following procedures in conventional processing dislocated and disrupted bubbles and films: osmium tetroxide and glutaraldehyde:formaldehyde:tannic acid mixture fixation; chemical dehydration (70-100% ethanol) and clarification (xylene and acetone); and embedding in paraffin or epoxy resin. Transection and dicing of the tissue aggravated the untoward effects. In contrast, bubbles and films remained stable in either glutaraldehyde or formaldehyde, which, however, did not protect against the other agents. (2) Degassing destroyed all bubbles as expected; however

  17. Microstructure, morphology and lifetime of armored bubbles exposed to surfactants

    OpenAIRE

    Subramaniam, Anand Bala; Mejean, Cecile; Abkarian, Manouk; Stone, Howard A.

    2006-01-01

    We report the behavior of particle-stabilized bubbles (armored bubbles) when exposed to various classes and concentrations of surfactants. The bubbles are non-spherical due to the jamming of the particles on the interface and are stable to dissolution prior to the addition of surfactant. We find that the dissolving bubbles exhibit distinct morphological, microstructural, and lifetime changes, which correlate with the concentration of surfactant employed. For low concentrations of surfactant a...

  18. Measurement of Entrained Air Bubbles and Vortices in Breaking Waves

    OpenAIRE

    大塚, 淳一; 渡部, 靖憲; Junichi, Otsuka; Yasunori, Watanabe; 北海道大学大学院工学研究科; School of Engineering, Hokkaido University

    2007-01-01

    Breaking waves produce numbers of vortices through a jet splashing process and also entrain many air bubbles, forming complicated air-water two-phase turbulent flow field in a surf zone. In this research, a simultaneous velocity measurement technique of water and bubble flows in breaking waves is developed for characterizing water-bubble interactions within vortices in a surf zone. The bubbles and neutral buoyant tracers are separately recorded by two different digital video cameras on the ba...

  19. A COINTEGRATION TEST TO VERIFY THE HOUSING BUBBLE

    OpenAIRE

    Bala Arshanapalli; William Nelson

    2008-01-01

    Housing prices in the US rose rapidly from 2000-2007Q3. Based on this evidence, the financial and general press concluded the US experienced a housing bubble. The efficient market theory denies the possibility of a bubble. This paper applies the statistical technique of cointegration to substantiate the presence of a housing bubble. The paper finds the statistical evidence consistent with the presence of a housing bubble in the period 2000-2007Q3 and not the underlying economic conditions.

  20. DEM Study of Wet Cohesive Particles in the Presence of Liquid Bridges in a Gas Fluidized Bed

    Directory of Open Access Journals (Sweden)

    Yurong He

    2014-01-01

    Full Text Available A modified discrete element method (DEM was constructed by compositing an additional liquid-bridge module into the traditional soft-sphere interaction model. Simulations of particles with and without liquid bridges are conducted in a bubbling fluidized bed. The geometry of the simulated bed is the same as the one in Müller’s experiment (Müller et al., 2008. A comparison between the dry and the wet particular systems is carried out on the bubble behavior, the bed fluctuation, and the mixing process. The bubble in the dry system possesses a regular round shape and falling of scattered particles exists while the bubble boundary of the wet particles becomes rough with branches of agglomerates stretching into it. The mixing of the dry system is quicker than that of the wet system. Several interparticle liquid contents are applied in this work to find their influence on the kinetic characteristic of the wet particle flow. With an increase of liquid content, the mixing process costs more time to be completed. Symmetrical profiles of the velocity and granular temperature are found for two low liquid contents (0.001% and 0.01%, while it is antisymmetrical for the highest liquid content (0.1%.

  1. Air bubble migration is a random event post embryo transfer.

    Science.gov (United States)

    Confino, E; Zhang, J; Risquez, F

    2007-06-01

    Air bubble location following embryo transfer (ET) is the presumable placement spot of embryos. The purpose of this study was to document endometrial air bubble position and migration following embryo transfer. Multicenter prospective case study. Eighty-eight embryo transfers were performed under abdominal ultrasound guidance in two countries by two authors. A single or double air bubble was loaded with the embryos using a soft, coaxial, end opened catheters. The embryos were slowly injected 10-20 mm from the fundus. Air bubble position was recorded immediately, 30 minutes later and when the patient stood up. Bubble marker location analysis revealed a random distribution without visible gravity effect when the patients stood up. The bubble markers demonstrated splitting, moving in all directions and dispersion. Air bubbles move and split frequently post ET with the patient in the horizontal position, suggestive of active uterine contractions. Bubble migration analysis supports a rather random movement of the bubbles and possibly the embryos. Standing up changed somewhat bubble configuration and distribution in the uterine cavity. Gravity related bubble motion was uncommon, suggesting that horizontal rest post ET may not be necessary. This report challenges the common belief that a very accurate ultrasound guided embryo placement is mandatory. The very random bubble movement observed in this two-center study suggests that a large "window" of embryo placement maybe present.

  2. Optical measurement of bubbles: System design and application

    NARCIS (Netherlands)

    Leifer, I.; Leeuw, G.de; Cohen, L.H.

    2003-01-01

    Affordable high quality charge-coupled device (CCD) video cameras and image processing software are powerful tools for bubble measurements. Because of the wide variation between bubble populations, different bubble measurement systems (BMSs) are required depending upon the application. Two BMSs are

  3. Rhetoric, Risk, and Markets: The Dot-Com Bubble

    Science.gov (United States)

    Goodnight, G. Thomas; Green, Sandy Edward, Jr.

    2010-01-01

    Post-conventional economic theories are assembled to inquire into the contingent, mimetic, symbolic, and material spirals unfolding the dot-com bubble, 1992-2002. The new technologies bubble is reconstructed as a rhetorical movement across the practices of the hybrid market-industry risk culture of communications. The legacies of the bubble task…

  4. Modeling of flow in microchannel with bubbles layer on surface

    Directory of Open Access Journals (Sweden)

    Gluzdov Dmitriy

    2017-01-01

    Full Text Available Results of 2D numerical solution of liquid flow in microchannel with bubbles layers on surface are presented. Bubbles layers are modeled by setting of bubble size and Navier slip condition. Calculations have been done using OpenFoam PISO method. The results of modeling compared with analytical solution.

  5. Nanoemulsions obtained via bubble bursting at a compound interface

    NARCIS (Netherlands)

    Feng, J.; Roche, M.; Vigolo, D.; Arnaudov, L.N.; Stoyanov, S.D.; Gurkov, T.D.; Tsutsumanova, G.G.; Stone, H.A.

    2014-01-01

    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

  6. Bubbles as a means for the deaeration of water bodies

    NARCIS (Netherlands)

    Zhang, Yuhang; Zhou, Gedi; Prosperetti, Andrea

    2017-01-01

    Occasional dissolved-air supersaturation - such as may occur, for instance, downstream of dams - is harmful to fish because it causes gas bubble disease. A counterintuitive but effective means of reducing dissolved air content is the injection of bubbles in the supersaturated water. The bubbles

  7. Shape oscillation of bubbles in the acoustic field

    OpenAIRE

    Matsumoto, Keishi; Ueno, Ichiro

    2009-01-01

    The authors introduce dynamics of multiple air bubbles exposed to ultrasonic wave while ascending in water in the present fluid dynamics video. The authors pay attention to the shape oscillation and the transition from the volume to the shape oscillations of the bubble. Correlation between the bubble size and the mechanism of the excitation of the shape oscillation is introduced.

  8. Variability Of Plasma Bubble In The Equatorial Ionosphere At Midnight

    African Journals Online (AJOL)

    There are various types of ionospheric irregularities. Among these is the plasma bubble occurrence. They are most prominent at night time in the equatorial ionosphere. Many of the bubbles drift with approximately the velocity of the background plasma, but it is possible to infer that most bubbles have moved upward at some ...

  9. Maximal air bubble entrainment at liquid-drop impact

    NARCIS (Netherlands)

    Bouwhuis, W.; van der Veen, Roeland; Tran, Tuan; Keij, D.L.; Winkels, K.G.; Peters, I.R.; van der Meer, Roger M.; Sun, Chao; Snoeijer, Jacobus Hendrikus; Lohse, Detlef

    2012-01-01

    At impact of a liquid drop on a solid surface, an air bubble can be entrapped. Here, we show that two competing effects minimize the (relative) size of this entrained air bubble: for large drop impact velocity and large droplets, the inertia of the liquid flattens the entrained bubble, whereas for

  10. Drag an lift forces on bubbles in a rotating flow

    NARCIS (Netherlands)

    van Nierop, Ernst A.; Luther, S.; Bluemink, J.J.; Magnaudet, Jacques; Prosperetti, Andrea; Lohse, Detlef

    2007-01-01

    The motion of small air bubbles in a horizontal solid-body rotating flow is investigated experimentally. Bubbles with a typical radius of 1mm are released in a liquid-filled horizontally rotating cylinder. We measure the transient motion of the bubbles in solid-body rotation and their final

  11. Calibrating optical bubble size by the displaced-mass method.

    NARCIS (Netherlands)

    Leifer, I.; Leeuw, G. de; Kunz, G.; Cohen, L.H.

    2003-01-01

    Bubble sizing by optical means is very common, but requires calibration by non-optical means. This is particularly important since apparent bubble size increases with decreasing threshold intensity. A calibration experiment was conducted comparing the displaced water mass from captured bubbles with

  12. Sustainable generation of bioenergy in fluidized bed boilers

    Energy Technology Data Exchange (ETDEWEB)

    Offenbacher, Elmar

    2010-07-01

    Full text: These days, reflecting a growing demand of heat and power, increasing cost for fossil fuels and more environmental issues (limitation of greenhouse gases, regulations for landfill etc.), the sustainable conversion of renewable fuels to bioenergy is becoming increasingly important. Renewable fuels cover a wide range, from traditional wood, bark, harvesting residues to all kind of sludges, and contain a remarkable calorific value that can easily compete with fossil fuels such as brown coal and lignite. The combustion of these renewable fuels does not create any greenhouse gases. The favourable technology for combusting renewable fuels is the fluidized bed technology, bubbling fluidized bed and circulating fluidized bed, as this system provides maximum fuel flexibility combined with high combustion efficiency and low emissions. Neither a variation of the water content and the heating value nor different sources of the material streams have a negative impact on the combustion. Fluidized bed boilers can switch from one fuel to the other quiet easily and can also be fired with conventional fuels that ensure a smooth and reliable generation of process heat and/or power in any case. The reasons that make fluidized bed boilers the most sustainable combustion technology for renewable fuels are various: The main feature of this technology is the principle of staged combustion of the fuel: The oxygen level in the fluidized bed is limited and hence only a part of the fuel is combusted, whereas the rest of the fuel is gasified. The staged combustion concept results in a homogenous temperature profile of less than 850 deg. C in the furnace and low NO{sub x} emission as a consequence. The turbulences in the furnace result and an efficient combustion that is combined with very low CO and TOC emissions in the flue gas. This paper will describe design features of the latest fluidized bed technology especially suitable for firing renewable fuels, and the research results of

  13. Multi-Dimensional Analysis of the Forced Bubble Dynamics Associated with Bubble Fusion Phenomena. Final Topical Report

    Energy Technology Data Exchange (ETDEWEB)

    Lahey, Jr., Richard T. [Rensselaer Polytechnic Inst., Troy, NY (United States). Center for Multiphase Research and Dept. of Mechanical, Aeronautical and Nuclear Engineering; Jansen, Kenneth E. [Rensselaer Polytechnic Inst., Troy, NY (United States). Center for Multiphase Research and Dept. of Mechanical, Aeronautical and Nuclear Engineering; Nagrath, Sunitha [Rensselaer Polytechnic Inst., Troy, NY (United States). Center for Multiphase Research and Dept. of Mechanical, Aeronautical and Nuclear Engineering

    2002-12-02

    A new adaptive grid, 3-D FEM hydrodynamic shock (ie, HYDRO )code called PHASTA-2C has been developed and used to investigate bubble implosion phenomena leading to ultra-high temperatures and pressures. In particular, it was shown that nearly spherical bubble compressions occur during bubble implosions and the predicted conditions associated with a recent ORNL Bubble Fusion experiment [Taleyarkhan et al, Science, March, 2002] are consistent with the occurrence of D/D fusion.

  14. Influence of the bubble-bubble interaction on destruction of encapsulated microbubbles under ultrasound.

    Science.gov (United States)

    Yasui, Kyuichi; Lee, Judy; Tuziuti, Toru; Towata, Atsuya; Kozuka, Teruyuki; Iida, Yasuo

    2009-09-01

    Influence of the bubble-bubble interaction on the pulsation of encapsulated microbubbles has been studied by numerical simulations under the condition of the experiment reported by Chang et al. [IEEE Trans. Ultrason Ferroelectr. Freq. Control 48, 161 (2001)]. It has been shown that the natural (resonance) frequency of a microbubble decreases considerably as the microbubble concentration increases to relatively high concentrations. At some concentration, the natural frequency may coincide with the driving frequency. Microbubble pulsation becomes milder as the microbubble concentration increases except at around the resonance condition due to the stronger bubble-bubble interaction. This may be one of the reasons why the threshold of acoustic pressure for destruction of an encapsulated microbubble increases as the microbubble concentration increases. A theoretical model for destruction has been proposed.

  15. Coal Bed Methane Primer

    Energy Technology Data Exchange (ETDEWEB)

    Dan Arthur; Bruce Langhus; Jon Seekins

    2005-05-25

    During the second half of the 1990's Coal Bed Methane (CBM) production increased dramatically nationwide to represent a significant new source of income and natural gas for many independent and established producers. Matching these soaring production rates during this period was a heightened public awareness of environmental concerns. These concerns left unexplained and under-addressed have created a significant growth in public involvement generating literally thousands of unfocused project comments for various regional NEPA efforts resulting in the delayed development of public and fee lands. The accelerating interest in CBM development coupled to the growth in public involvement has prompted the conceptualization of this project for the development of a CBM Primer. The Primer is designed to serve as a summary document, which introduces and encapsulates information pertinent to the development of Coal Bed Methane (CBM), including focused discussions of coal deposits, methane as a natural formed gas, split mineral estates, development techniques, operational issues, producing methods, applicable regulatory frameworks, land and resource management, mitigation measures, preparation of project plans, data availability, Indian Trust issues and relevant environmental technologies. An important aspect of gaining access to federal, state, tribal, or fee lands involves education of a broad array of stakeholders, including land and mineral owners, regulators, conservationists, tribal governments, special interest groups, and numerous others that could be impacted by the development of coal bed methane. Perhaps the most crucial aspect of successfully developing CBM resources is stakeholder education. Currently, an inconsistent picture of CBM exists. There is a significant lack of understanding on the parts of nearly all stakeholders, including industry, government, special interest groups, and land owners. It is envisioned the Primer would being used by a variety of

  16. Heat transfer in high temperature fluidized beds with immersed tubes for coal combustion service. Final report, October 1, 1977-March 31, 1981

    Energy Technology Data Exchange (ETDEWEB)

    Welty, J. R.

    1984-01-01

    The project involved two parts: analytical and experimental. The progression of work includes the following major divisions: analytical studies involving studies of heat transfer, hydrodynamics of gas flow within the bed, and some considerations of bubble and adjacent tube influences on the heat transfer; experimental apparatus including the instrumented tubes for heat transfer measurements, digital data acquisition, and the high temperature fluidized bed test facility; experimental results; and experimental validation of the analytical model.

  17. Is Education Facing a "Tech Bubble"?

    Science.gov (United States)

    Davis, Michelle R.

    2013-01-01

    Educational technology companies and entrepreneurs may face the risk of a "tech bubble," similar to the massive boom-and-bust that rocked the technology market in the late 1990s, according to market analysts and a recently released paper. A relatively new focus on K-12 educational technology as an investment vehicle, a surge of investors looking…

  18. Ultrasound contrast agents : dynamics of coated bubbles

    NARCIS (Netherlands)

    Overvelde, M.L.J.

    2010-01-01

    Contrast-enhanced ultrasound imaging relies on the nonlinear scattering of microbubbles suspended in an ultrasound contrast agent. The bubble dynamics is described by a Rayleigh-Plesset-type equation, and the success of harmonic imaging using contrast agents has always been attributed to the

  19. Bubble growth on an impulsively powered microheater

    NARCIS (Netherlands)

    Yin, Z.; Prosperetti, Andrea; Kim, J.

    2004-01-01

    The dynamics of single vapor bubbles in FC-72 generated by a transient heat pulse applied to a square 260 × 260 μm2 microheater are investigated for different heat fluxes between 3 and 44 MW/m2. It is found that in all cases the growth consists of two steps, a first relatively violent one, followed

  20. Inert gas accumulation in sonoluminescing bubbles

    NARCIS (Netherlands)

    Lohse, Detlef; Hilgenfeldt, Sascha

    1997-01-01

    In this paper we elaborate on the idea [Lohse et al., Phys. Rev. Lett. 78, 1359-1362 (1997)] that (single) sonoluminescing air bubbles rectify argon. The reason for the rectification is that nitrogen and oxygen dissociate and their reaction products dissolve in water. We give further experimental

  1. Radiolytic and thermolytic bubble gas hydrogen composition

    Energy Technology Data Exchange (ETDEWEB)

    Woodham, W. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2017-12-11

    This report describes the development of a mathematical model for the estimation of the hydrogen composition of gas bubbles trapped in radioactive waste. The model described herein uses a material balance approach to accurately incorporate the rates of hydrogen generation by a number of physical phenomena and scale the aforementioned rates in a manner that allows calculation of the final hydrogen composition.

  2. Argonne Bubble Experiment Thermal Model Development II

    Energy Technology Data Exchange (ETDEWEB)

    Buechler, Cynthia Eileen [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-07-01

    This report describes the continuation of the work reported in “Argonne Bubble Experiment Thermal Model Development”. The experiment was performed at Argonne National Laboratory (ANL) in 2014. A rastered 35 MeV electron beam deposited power in a solution of uranyl sulfate, generating heat and radiolytic gas bubbles. Irradiations were performed at three beam power levels, 6, 12 and 15 kW. Solution temperatures were measured by thermocouples, and gas bubble behavior was observed. This report will describe the Computational Fluid Dynamics (CFD) model that was developed to calculate the temperatures and gas volume fractions in the solution vessel during the irradiations. The previous report described an initial analysis performed on a geometry that had not been updated to reflect the as-built solution vessel. Here, the as-built geometry is used. Monte-Carlo N-Particle (MCNP) calculations were performed on the updated geometry, and these results were used to define the power deposition profile for the CFD analyses, which were performed using Fluent, Ver. 16.2. CFD analyses were performed for the 12 and 15 kW irradiations, and further improvements to the model were incorporated, including the consideration of power deposition in nearby vessel components, gas mixture composition, and bubble size distribution. The temperature results of the CFD calculations are compared to experimental measurements.

  3. Non-Abelian bubbles in microstate geometries

    Science.gov (United States)

    Ramírez, Pedro F.

    2016-11-01

    We find the first smooth bubbling microstate geometries with non-Abelian fields. The solutions constitute an extension of the BPS three-charge smooth microstates. These consist in general families of regular supersymmetric solutions with non-trivial topology, i.e. bubbles, of {N}=d , d = 5 Super-Einstein-Yang-Mills theory, having the asymptotic charges of a black hole or black ring but with no horizon. The non-Abelian fields make their presence at the very heart of the microstate structure: the physical size of the bubbles is affected by the non-Abelian topological charge they carry, which combines with the Abelian flux threading the bubbles to hold them up. Interestingly the non-Abelian fields carry a set of adjustable continuous parameters that do not alter the asymptotics of the solutions but modify the local geometry. This feature can be used to obtain a classically infinite number of microstate solutions with the asymptotics of a single black hole or black ring.

  4. Big Bubbles in Boiling Liquids: Students' Views

    Science.gov (United States)

    Costu, Bayram

    2008-01-01

    The aim of this study was to elicit students' conceptions about big bubbles in boiling liquids (water, ethanol and aqueous CuSO[subscript 4] solution). The study is based on twenty-four students at different ages and grades. The clinical interviews technique was conducted to solicit students' conceptions and the interviews were analyzed to…

  5. Four-bubble clusters and Menelaus' theorem

    Science.gov (United States)

    Fischer, Fred

    2002-10-01

    We discuss a relatively easy way to construct a stable cluster of four soap bubbles using the radii of four selected spherical films out of a total of ten. To this end, we extend Menelaus' theorem, a geometrical relation between a triangle and a straight line in the plane, to three and higher dimensions.

  6. Soap-bubble Optimization of Gaits

    Science.gov (United States)

    Ramasamy, Suresh; Hatton, Ross

    We present a geometric gait optimizer that applies Lie bracket theory to identify optimal cost-of-transport (displacement divided by effort) gaits. This optimizer builds on our previous work, where we have shown that for drag-dominated systems, the efficiency of a gait corresponds to a ratio between ``metric-weighted perimeter length of the cycle and the area integral of the Lie bracket it encloses. In this work, we encode this geometric insight into a variational gait optimizer. For a system with two shape variables, the dynamics of this optimizer are similar to the dynamics of a soap bubble, with the Lie bracket providing internal pressure which causes the boundary of the bubble to expand, the metric-weighted path length providing surface tension constraining the growth of the soap bubble, and a pace-balancing term corresponding to the concentration gradient that evenly distributes soap across the surface of the bubble. In systems with three shape variables, the dynamics are more akin to a windsock, capturing maximum flux through a loop. The variational form of the optimizer allows us to extend it to higher dimensional shape spaces beyond these physical analogies.

  7. Condensation of vapor bubble in subcooled pool

    Science.gov (United States)

    Horiuchi, K.; Koiwa, Y.; Kaneko, T.; Ueno, I.

    2017-02-01

    We focus on condensation process of vapor bubble exposed to a pooled liquid of subcooled conditions. Two different geometries are employed in the present research; one is the evaporation on the heated surface, that is, subcooled pool boiling, and the other the injection of vapor into the subcooled pool. The test fluid is water, and all series of the experiments are conducted under the atmospheric pressure condition. The degree of subcooling is ranged from 10 to 40 K. Through the boiling experiment, unique phenomenon known as microbubble emission boiling (MEB) is introduced; this phenomenon realizes heat flux about 10 times higher than the critical heat flux. Condensation of the vapor bubble is the key phenomenon to supply ambient cold liquid to the heated surface. In order to understand the condensing process in the MEB, we prepare vapor in the vapor generator instead of the evaporation on the heated surface, and inject the vapor to expose the vapor bubble to the subcooled liquid. Special attention is paid to the dynamics of the vapor bubble detected by the high-speed video camera, and on the enhancement of the heat transfer due to the variation of interface area driven by the condensation.

  8. BUBBLE - an urban boundary layer meteorology project

    DEFF Research Database (Denmark)

    Rotach, M.W.; Vogt, R.; Bernhofer, C.

    2005-01-01

    The Basel urban Boundary Layer Experiment (BUBBLE) was a year-long experimental effort to investigate in detail the boundary layer structure in the City of Basel, Switzerland. At several sites over different surface types (urban, sub-urban and rural reference) towers up to at least twice the main...

  9. Non-Abelian bubbles in microstate geometries

    Energy Technology Data Exchange (ETDEWEB)

    Ramírez, Pedro F. [Instituto de Física Teórica UAM/CSIC,C/ Nicolás Cabrera, 13-15, C.University Cantoblanco, E-28049 Madrid (Spain); Institut de Physique Théorique, Université Paris Saclay, CEA, CNRS,Orme des Merisiers bâtiment 774, F-91191 Gif-sur-Yvette (France)

    2016-11-24

    We find the first smooth bubbling microstate geometries with non-Abelian fields. The solutions constitute an extension of the BPS three-charge smooth microstates. These consist in general families of regular supersymmetric solutions with non-trivial topology, i.e. bubbles, of N=1, d=5 Super-Einstein-Yang-Mills theory, having the asymptotic charges of a black hole or black ring but with no horizon. The non-Abelian fields make their presence at the very heart of the microstate structure: the physical size of the bubbles is affected by the non-Abelian topological charge they carry, which combines with the Abelian flux threading the bubbles to hold them up. Interestingly the non-Abelian fields carry a set of adjustable continuous parameters that do not alter the asymptotics of the solutions but modify the local geometry. This feature can be used to obtain a classically infinite number of microstate solutions with the asymptotics of a single black hole or black ring.

  10. Heat transport in bubbling turbulent convection.

    Science.gov (United States)

    Lakkaraju, Rajaram; Stevens, Richard J A M; Oresta, Paolo; Verzicco, Roberto; Lohse, Detlef; Prosperetti, Andrea

    2013-06-04

    Boiling is an extremely effective way to promote heat transfer from a hot surface to a liquid due to numerous mechanisms, many of which are not understood in quantitative detail. An important component of the overall process is that the buoyancy of the bubble compounds with that of the liquid to give rise to a much-enhanced natural convection. In this article, we focus specifically on this enhancement and present a numerical study of the resulting two-phase Rayleigh-Bénard convection process in a cylindrical cell with a diameter equal to its height. We make no attempt to model other aspects of the boiling process such as bubble nucleation and detachment. The cell base and top are held at temperatures above and below the boiling point of the liquid, respectively. By keeping this difference constant, we study the effect of the liquid superheat in a Rayleigh number range that, in the absence of boiling, would be between 2 × 10(6) and 5 × 10(9). We find a considerable enhancement of the heat transfer and study its dependence on the number of bubbles, the degree of superheat of the hot cell bottom, and the Rayleigh number. The increased buoyancy provided by the bubbles leads to more energetic hot plumes detaching from the cell bottom, and the strength of the circulation in the cell is significantly increased. Our results are in general agreement with recent experiments on boiling Rayleigh-Bénard convection.

  11. A method for indication and improving the position stability of the bubble in single-bubble cavitation experiments

    Science.gov (United States)

    Plocek, Jaroslav

    2017-10-01

    A newly developed method for indication of the bubble state in classical single-bubble cavitation experiments is introduced. The method is based on processing the signal from a sensor, positioned on the flask from outside. The technical means of the method are further explored to improve the position stability of the bubble.

  12. Modeling of mass transfer and chemical reactions in a bubble column reactor using a discrete bubble model

    NARCIS (Netherlands)

    Darmana, D.; Deen, N.G.; Kuipers, J.A.M.

    2004-01-01

    A 3D discrete bubble model is adopted to investigate complex behavior involving hydrodynamics, mass transfer and chemical reactions in a gas-liquid bubble column reactor. In this model a continuum description is adopted for the liquid phase and additionally each individual bubble is tracked in a

  13. Detailed modeling of hydrodynamics mass transfer and chemical reactions in a bubble column using a discrete bubble model

    NARCIS (Netherlands)

    Darmana, D.; Deen, N.G.; Kuipers, J.A.M.

    2005-01-01

    A 3D discrete bubble model is adopted to investigate complex behavior involving hydrodynamics, mass transfer and chemical reactions in a gas¿liquid bubble column reactor. In this model a continuum description is adopted for the liquid phase and additionally each individual bubble is tracked in a

  14. A derivation of the stable cavitation threshold accounting for bubble-bubble interactions.

    Science.gov (United States)

    Guédra, Matthieu; Cornu, Corentin; Inserra, Claude

    2017-09-01

    The subharmonic emission of sound coming from the nonlinear response of a bubble population is the most used indicator for stable cavitation. When driven at twice their resonance frequency, bubbles can exhibit subharmonic spherical oscillations if the acoustic pressure amplitude exceeds a threshold value. Although various theoretical derivations exist for the subharmonic emission by free or coated bubbles, they all rest on the single bubble model. In this paper, we propose an analytical expression of the subharmonic threshold for interacting bubbles in a homogeneous, monodisperse cloud. This theory predicts a shift of the subharmonic resonance frequency and a decrease of the corresponding pressure threshold due to the interactions. For a given sonication frequency, these results show that an optimal value of the interaction strength (i.e. the number density of bubbles) can be found for which the subharmonic threshold is minimum, which is consistent with recently published experiments conducted on ultrasound contrast agents. Copyright © 2017 Elsevier B.V. All rights reserved.

  15. Cavitation Bubble Nucleation by Energetic Particles

    Energy Technology Data Exchange (ETDEWEB)

    West, C.D.

    1998-12-01

    In the early sixties, experimental measurements using a bubble chamber confirmed quantitatively the thermal spike theory of bubble nucleation by energetic particles: the energy of the slow, heavy alpha decay recoils used in those experiments matched the calculated bubble nucleation energy to within a few percent. It was a triumph, but was soon to be followed by a puzzle. Within a couple of years, experiments on similar liquids, but well below their normal boiling points, placed under tensile stress showed that the calculated bubble nucleation energy was an order of magnitude less than the recoil energy. Why should the theory work so well in the one case and so badly in the other? How did the liquid, or the recoil particle, "know" the difference between the two experiments? Another mathematical model of the same physical process, introduced in 1967, showed qualitatively why different analyses would be needed for liquids with high and low vapor pressures under positive or negative pressures. But, the quantitative agreement between the calculated nucleation energy and the recoil energy was still poor--the former being smaller by a factor of two to three. In this report, the 1967 analysis is extended and refined: the qualitative understanding of the difference between positive and negative pressure nucleation, "boiling" and "cavitation" respectively, is retained, and agreement between the negative pressure calculated to be needed for nucleation and the energy calculated to be available is much improved. A plot of the calculated negative pressure needed to induce bubble formation against the measured value now has a slope of 1.0, although there is still considerable scatter in the individual points.

  16. Relationship between Liquidity and Price Bubble in Tehran's Asset Market

    Directory of Open Access Journals (Sweden)

    J. Khodaparast SHIRAZI

    2012-12-01

    Full Text Available In this paper, according to Austrian school, the existence of bubbles in asset market of Tehran from 1998 to 2009 is attributed to the unexpected fluctuations of liquidity. To find out the process of bubble, the state space form and Kalman filter are used and bubble is brought out as unobserved variable of price series. In order to determine the long run relationship between liquidity and price bubble the VAR method proposed by Johanson and Jelisus is used. The result confirms that variation of liquidity has a significant effect on the creating of bubble in long run.

  17. Path instabilities of air bubbles rising in clean water

    CERN Document Server

    Wu, M; Wu, Mingming; Gharib, Moteza

    1998-01-01

    Experiments are conducted to study the path and shape of single air bubbles (diameter range 0.10- 0.20cm) rising freely in clean water. The experimental results demonstrate that the bubble shape has a bistable state, i. e. the bubble chooses to be in spherical or ellipsoidal shape depending on its generation mechanism. The path of a spherical/ellipsoidal bubble is found to change from a straight path to a zigzag/spiral path via a supercritical/subcritical bifurcation when the Reynolds number of the bubble exceeds a threshold.

  18. Champagne experiences various rhythmical bubbling regimes in a flute.

    Science.gov (United States)

    Liger-Belair, Gérard; Tufaile, Alberto; Jeandet, Philippe; Sartorelli, José-Carlos

    2006-09-20

    Bubble trains are seen rising gracefully from a few points on the glass wall (called nucleation sites) whenever champagne is poured into a glass. As time passes during the gas-discharging process, the careful observation of some given bubble columns reveals that the interbubble distance may change suddenly, thus revealing different rhythmical bubbling regimes. Here, it is reported that the transitions between the different bubbling regimes of some nucleation sites during gas discharging is a process which may be ruled by a strong interaction between tiny gas pockets trapped inside the nucleation site and/or also by an interaction between the tiny bubbles just blown from the nucleation site.

  19. A note on the dynamics of two aligned bubbles perpendicular to and above a thin membrane

    Energy Technology Data Exchange (ETDEWEB)

    Aghdam, A Hajizadeh [Department of Mechanical Engineering, Arak University of Technology, Arak 3818141167 (Iran, Islamic Republic of); Khoo, B C, E-mail: Hajizadeh@arakut.ac.ir [Department of Mechanical Engineering, National University of Singapore, 10 Kent Ridge Crescent, Singapore 119260 (Singapore)

    2015-06-15

    The interaction of two perpendicular bubbles of a similar size (upper bubble and lower bubble) and the thin elastic membrane beneath them is studied experimentally. The dynamical behavior of the lower bubble (Bubble1), which is placed between the membrane and upper bubble (Bubble2), is rather complex. Observed phenomena such as the splitting of Bubble1 into the ‘mushroom shape’ and ‘masher shape’, the bubble-collapse induced jetting toward Bubble2 and even the coalescence effect are found and systematically categorized by the stated dimensionless parameters. (paper)

  20. Predawn plasma bubble cluster observed in Southeast Asia

    Science.gov (United States)

    Watthanasangmechai, Kornyanat; Yamamoto, Mamoru; Saito, Akinori; Tsunoda, Roland; Yokoyama, Tatsuhiro; Supnithi, Pornchai; Ishii, Mamoru; Yatini, Clara

    2016-06-01

    Predawn plasma bubble was detected as deep plasma depletion by GNU Radio Beacon Receiver (GRBR) network and in situ measurement onboard Defense Meteorological Satellite Program F15 (DMSPF15) satellite and was confirmed by sparse GPS network in Southeast Asia. In addition to the deep depletion, the GPS network revealed the coexisting submesoscale irregularities. A deep depletion is regarded as a primary bubble. Submesoscale irregularities are regarded as secondary bubbles. Primary bubble and secondary bubbles appeared together as a cluster with zonal wavelength of 50 km. An altitude of secondary bubbles happened to be lower than that of the primary bubble in the same cluster. The observed pattern of plasma bubble cluster is consistent with the simulation result of the recent high-resolution bubble (HIRB) model. This event is only a single event out of 76 satellite passes at nighttime during 3-25 March 2012 that significantly shows plasma depletion at plasma bubble wall. The inside structure of the primary bubble was clearly revealed from the in situ density data of DMSPF15 satellite and the ground-based GRBR total electron content.