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Sample records for flux particle bed

  1. A review of dryout heat fluxes and coolability of particle beds. APRI 4, Stage 2 Report

    Energy Technology Data Exchange (ETDEWEB)

    Lindholm, Ilona [VTT Energy, Helsinki (Finland)

    2002-04-01

    Dryout heat flux experiments on particle beds have been reviewed. The observed dryout heat flux varies from some tens of kW/m{sup 2} to well over 1 MW/m 2 . The variation can be qualitatively and to some extent also quantitatively explained. The effect of particle diameter has been clearly demonstrated. For particles having diameter less than about 1 mm, the dryout heat flux on the order of 100-200 kW/m{sup 2}, and increases on square of the particle diameter. For larger than 1 mm particles the dryout heat flux increases on square root of the particle diameter. Typical values for {approx} 5 mm particles is 500 kW/m{sup 2} to 1 MW/m{sup 2} . An effect of bed thickness can be seen for small particles and medium range (50-500 mm) beds. For thick beds, > 500 mm, the dryout heat flux does not any more change as the bed height increases. The dryout heat flux increases with increasing coolant pressure. This can be explained by the increasing vapour density, which can remove more latent heat from the bed. Debris bed stratification, with small particles on top, clearly decreases the dryout heat flux. The dryout heat flux in a stratified bed can even be smaller than a heat flux of an equivalent debris bed consisting of the smaller particles alone. This is due to the capillary force, which draws liquid towards the smaller particles and causes the dryout to occur at the interface of the particle layers. A model has been developed by Lipinski to estimate dryout heat fluxes in a particle bed. The model has been derived based on solution of momentum, energy and mass conservation equations for two phases. The 1-D model can take into account variable particle sizes (stratification) along the bed and different coolant entry positions. It has been shown that the model can quite well predict the observed dryout characteristics in most experiments. The simpler 0-D model can give reasonable estimates for non-stratified beds. Results and observations of several tests on melt jet

  2. A Numerical Simulation of Gas-Particle Two-Phase Flow in a Suspension Bed Using Diffusion Flux Model

    Institute of Scientific and Technical Information of China (English)

    尚智; 杨瑞昌; FUKUDAKenji; 钟勇; 巨泽建

    2003-01-01

    A mathematical model of two-dimensional turbulent gas-particle two-phase flow based on the modified diffusion flux model (DFM) and a numerical simulation method to analyze the gas-particle flow structures are developed. The modified diffusion flux model, in which the acceleration due to various forces is taken into account for the calculation of the diffusion velocity of particles, is applicable to the analysis of multi-dimensional gas-particle two-phase turbulent flow. In order to verify its accuracy and efficiency, the numerical simulation by DFM is compared with experimental studies and the prediction by κ-ε-κp two-fluid model, which shows a reasonable agreement. It is confirmed that the modified diffusion flux model is suitable for simulating the multi-dimensional gas-particle two-phase flow.

  3. Forces on stationary particles in near-bed turbulent flows

    Science.gov (United States)

    Schmeeckle, M.W.; Nelson, J.M.; Shreve, R.L.

    2007-01-01

    In natural flows, bed sediment particles are entrained and moved by the fluctuating forces, such as lift and drag, exerted by the overlying flow on the particles. To develop a better understanding of these forces and the relation of the forces to the local flow, the downstream and vertical components of force on near-bed fixed particles and of fluid velocity above or in front of them were measured synchronously at turbulence-resolving frequencies (200 or 500 Hz) in a laboratory flume. Measurements were made for a spherical test particle fixed at various heights above a smooth bed, above a smooth bed downstream of a downstream-facing step, and in a gravel bed of similarly sized particles as well as for a cubical test particle and 7 natural particles above a smooth bed. Horizontal force was well correlated with downstream velocity and not correlated with vertical velocity or vertical momentum flux. The standard drag formula worked well to predict the horizontal force, but the required value of the drag coefficient was significantly higher than generally used to model bed load motion. For the spheres, cubes, and natural particles, average drag coefficients were found to be 0.76, 1.36, and 0.91, respectively. For comparison, the drag coefficient for a sphere settling in still water at similar particle Reynolds numbers is only about 0.4. The variability of the horizontal force relative to its mean was strongly increased by the presence of the step and the gravel bed. Peak deviations were about 30% of the mean force for the sphere over the smooth bed, about twice the mean with the step, and 4 times it for the sphere protruding roughly half its diameter above the gravel bed. Vertical force correlated poorly with downstream velocity, vertical velocity, and vertical momentum flux whether measured over or ahead of the test particle. Typical formulas for shear-induced lift based on Bernoulli's principle poorly predict the vertical forces on near-bed particles. The

  4. Particle Pressures in Fluidized Beds. Final report

    Energy Technology Data Exchange (ETDEWEB)

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

    1996-09-01

    This project studies the particle pressure, which may be thought of as the force exerted by the particulate phase of a multiphase mixture, independently of that exerted by other phases. The project is divided into two parts, one concerning gas and the other liquid fluidized beds. Previous work on gas fluidized beds had suggested that the particle pressures are generated by bubbling action. Thus, for these gas fluidized bed studies, the particle pressure is measured around single bubbles generated in 2-D fluidized beds, using special probes developed especially for this purpose. Liquid beds are immune from bubbling and the particle pressures proved too small to measure directly. However, the major interest in particle pressures in liquid beds lies in their stabilizing effect that arises from the effective elasticity (the derivative of the particle pressure with respect to the void fraction): they impart to the bed. So rather than directly measure the particle pressure, we inferred the values of the elasticity from measurements of instability growth in liquid beds the inference was made by first developing a generic stability model (one with all the normally modeled coefficients left undetermined)and then working backwards to determine the unknown coefficients, including the elasticity.

  5. Particle pressures in fluidized beds. Final report

    Energy Technology Data Exchange (ETDEWEB)

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

    1996-09-01

    This project studies the particle pressure, which may be thought of as the force exerted by the particulate phase of a multiphase mixture, independently of that exerted by other phases. The project is divided into two parts, one concerning gas and the other liquid fluidized beds. Previous work on gas fluidized beds had suggested that the particle pressures are generated by bubbling action. Thus, for these gas fluidized bed studies, the particle pressure is measured around single bubbles generated in 2-D fluidized beds, using special probes developed especially for this purpose. Liquid beds are immune from bubbling and the particle pressures proved too small to measure directly. However, the major interest in particle pressures in liquid beds lies in their stabilizing effect that arises from the effective elasticity (the derivative of the particle pressure with respect to the void fraction), they impart to the bed. So rather than directly measure the particle pressure, the authors inferred the values of the elasticity from measurements of instability growth in liquid beds; the inference was made by first developing a generic stability model (one with all the normally modeled coefficients left undetermined) and then working backwards to determine the unknown coefficients, including the elasticity.

  6. Acoustic observations of near-bed sediment concentration and flux statistics above migrating sand dunes

    Science.gov (United States)

    Wilson, G. W.; Hay, A. E.

    2016-06-01

    A coherent Doppler profiler was used to measure coincident time series of velocity (u,w), sediment mass concentration (c), and sediment grain size (d), above mobile sand dunes in unidirectional flow (˜1 m/s, ˜1 m water depth). The measurements are used to extract statistical distributions of sediment concentration and flux just above the bed. Observed mass fluxes (uc,wc) were well fit by quasi-exponential distributions, at all positions along the dune profile, similar to previous observations of single-particle momenta for bed load over flat beds. Observed concentrations of moving particles were well fit by negative-binomial distributions, also similar to previous observations over flat beds. These probability distributions relate to two recent stochastic theories, previously derived and verified for uniform flow over flat beds. It is hypothesized that these theories may also be used as a local approximation in natural-scale flows with bed forms.

  7. Ultra high temperature particle bed reactor design

    Science.gov (United States)

    Lazareth, Otto; Ludewig, Hans; Perkins, K.; Powell, J.

    1990-01-01

    A direct nuclear propulsion engine which could be used for a mission to Mars is designed. The main features of this reactor design are high values for I(sub sp) and very efficient cooling. This particle bed reactor consists of 37 cylindrical fuel elements embedded in a cylinder of beryllium which acts as a moderator and reflector. The fuel consists of a packed bed of spherical fissionable fuel particles. Gaseous H2 passes over the fuel bed, removes the heat, and is exhausted out of the rocket. The design was found to be neutronically critical and to have tolerable heating rates. Therefore, this particle bed reactor design is suitable as a propulsion unit for this mission.

  8. Shock Interaction with Random Spherical Particle Beds

    Science.gov (United States)

    Neal, Chris; Mehta, Yash; Salari, Kambiz; Jackson, Thomas L.; Balachandar, S. "Bala"; Thakur, Siddharth

    2016-11-01

    In this talk we present results on fully resolved simulations of shock interaction with randomly distributed bed of particles. Multiple simulations were carried out by varying the number of particles to isolate the effect of volume fraction. Major focus of these simulations was to understand 1) the effect of the shockwave and volume fraction on the forces experienced by the particles, 2) the effect of particles on the shock wave, and 3) fluid mediated particle-particle interactions. Peak drag force for particles at different volume fractions show a downward trend as the depth of the bed increased. This can be attributed to dissipation of energy as the shockwave travels through the bed of particles. One of the fascinating observations from these simulations was the fluctuations in different quantities due to presence of multiple particles and their random distribution. These are large simulations with hundreds of particles resulting in large amount of data. We present statistical analysis of the data and make relevant observations. Average pressure in the computational domain is computed to characterize the strengths of the reflected and transmitted waves. We also present flow field contour plots to support our observations. U.S. Department of Energy, National Nuclear Security Administration, Advanced Simulation and Computing Program, as a Cooperative Agreement under the Predictive Science Academic Alliance Program, under Contract No. DE-NA0002378.

  9. Evaluating Energy Flux in Vibrofluidized Granular Bed

    Directory of Open Access Journals (Sweden)

    N. A. Sheikh

    2013-01-01

    Full Text Available Granular flows require sustained input of energy for fluidization. A level of fluidization depends on the amount of heat flux provided to the flow. In general, the dissipation of the grains upon interaction balances the heat inputs and the resultant flow patterns can be described using hydrodynamic models. However, with the increase in packing fraction, the heat fluxes prediction of the cell increases. Here, a comparison is made for the proposed theoretical models against the MD simulations data. It is observed that the variation of packing fraction in the granular cell influences the heat flux at the base. For the elastic grain-base interaction, the predictions vary appreciably compared to MD simulations, suggesting the need to accurately model the velocity distribution of grains for averaging.

  10. FBR and RBR particle bed space reactors

    Energy Technology Data Exchange (ETDEWEB)

    Powell, J.R.; Botts, T.E.

    1983-01-01

    Compact, high-performance nuclear reactor designs based on High-Temperature Gas Reactors (HTGRs) particulate fuel are investigated. The large surface area available with the small-diameter (approx. 500 microns) particulate fuel allows very high power densities (MW's/liter), small temperature differences between fuel and coolant (approx. 10/sup 0/K), high coolant-outlet temperatures (1500 to 3000/sup 0/K, depending on design), and fast reactor startup (approx. 2 to 3 seconds). Two reactor concepts are developed - the Fixed Bed Reactor (FBR), where the fuel particles are packed into a thin annular bed between two porous cylindrical drums, and the Rotating Bed Reactor (RBR), where the fuel particles are held inside a cold rotating (typically approx. 500 rpm) porous cylindrical drum. The FBR can operate steady-state in the closed-cycle He-cooled mode or in the open-cycle H/sub 2/-cooled mode. The RBR will operate only in the open-cycle H/sub 2/-cooled mode.

  11. Cooling of an internal-heated debris bed with fine particles

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Z.L.; Sehgal, B.R. [Royal Institute of Technology, Div. of Nuclear Power Safety, Stockholm (Sweden)

    2001-07-01

    In this paper, an analytical model on dryout heat flux of ex-vessel debris beds with fines particles under top flooding conditions has been developed. The parametric study is performed on the effect of the stratification of the debris beds on the dryout heat flux. The calculated results show that the stratification configuration of the debris beds with smaller particles and lower porosity layer resting on the top of another layer of the beds has profound effect on the dryout heat flux for the debris beds both with and without a downcomer. The enhancement of the dryout heat flux by the downcomer is significant. The efficiency of the single downcomer on the enhancement of the dryout heat flux is also analyzed. This, in general, agrees well with experimental data. The model is also employed to perform the assessment on the coolability of the ex-vessel debris bed under representative accidental conditions. One conservative case is chosen, and it is found that the downcomer could be efficient measure to cool the debris bed and hence terminate the severe accident. (authors)

  12. Methods of forming a fluidized bed of circulating particles

    Science.gov (United States)

    Marshall, Douglas W [Blackfoot, ID

    2011-05-24

    There is disclosed an apparatus for forming a fluidized bed of circulating particles. In an embodiment, the apparatus includes a bottom portion having a sidewall, the sidewall defining a curvilinear profile, and the bottom portion configured to contain a bed of particles; and a gas inlet configured to produce a column of gas to carry entrained particles therein. There is disclosed a method of forming a fluidized bed of circulating particles. In an embodiment, the method includes positioning particles within a bottom portion having a sidewall, the sidewall defining a curvilinear profile; producing a column of gas directed upwardly through a gas inlet; carrying entrained particles in the column of gas to produce a fountain of particles over the fluidized bed of circulating particles and subside in the particle bed until being directed inwardly into the column of gas within the curvilinear profile.

  13. Heat flux distribution on circulating fluidized bed boiler water wall

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The future of circulating fluidized bed (CFB)combustion technology is in raising the steam parameters to supercritical levels.Understanding the heat flux distribution on the water wall is one of the most important issues in the design and operation of supercritical pressure CFB boilers.In the present paper,the finite element analysis (FEA) method is adopted to predict the heat transfer coefficient as well as the heat flux of the membrane wall and the results are validated by direct measurement of the temperature around the tube.Studies on the horizontal heat flux distribution were conducted in three CFB boilers with different furnace size,tube dimension and water temperature.The results are useful in supercritical pressure CFB boiler design.

  14. Fluidized Bed Sputtering for Particle and Powder Metallization

    Science.gov (United States)

    2013-04-01

    Fluidized Bed Sputtering for Particle and Powder Metallization by Daniel M. Baechle, J. Derek Demaree, James K. Hirvonen, and Eric D...5069 ARL-TR-6435 April 2013 Fluidized Bed Sputtering for Particle and Powder Metallization Daniel M. Baechle, J. Derek Demaree, James K...YYYY) April 2013 2. REPORT TYPE Final 3. DATES COVERED (From - To) June 2008–June 2012 4. TITLE AND SUBTITLE Fluidized Bed Sputtering for

  15. Computational and Experimental Study of Spherocylinder Particles in Fluidized Beds

    Science.gov (United States)

    Mahajan, Vinay; Kuipers, Hans; Padding, Johan; Multiphase Reactors Group, TU Eindhoven Team

    2016-11-01

    Non-spherical particle flows are often encountered in fluidized process equipment. A coupled computational fluid dynamics (CFD) and discrete element method(DEM) approach has been extensively applied in recent years to study these flows at the particle scale. However, most of these studies focus on spherical particles while in reality, the constituent particles are seldom spherical. Particle shape can significantly affect the hydrodynamical response in fluidized beds. The drag force acting on a non-spherical particle can vary considerably with particle shape, orientation of the particle, Reynolds number and packing fraction. In this work, a CFD-DEM approach has been extended to model a lab scale quasi-2D fluidized bed of spherocylinder (rod-like) particles. These particles can be classified as Geldart D particles and have an aspect ratio of 4. Numerical results for the pressure drop, bed height and solid circulation patterns are compared with results from a complementary laboratory experiment. We also present results on particle orientations close to the confining walls, which provides interesting insight regarding the particle alignment. Thus the capability of the CFD-DEM approach to efficiently account for global bed dynamics in fluidized bed of rod-like particle is demonstrated. This research work is funded by ERC Grant.

  16. 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.

  17. The effect of vibration on bed voidage behaviors in fluidized beds with large particles

    Energy Technology Data Exchange (ETDEWEB)

    Jin, H.; Zhang, J.; Zhang, B.

    2007-07-01

    The effects of vibration parameters, operating conditions and material properties on bed voidage were investigated using an optical fiber probe approach in a vibrating fluidized bed with a diameter of 148 mm. Variables studied included frequency (0-282 s{sup -1}), amplitude (0 mm-1 mm), bed height (0.1 m-0.4 m) as well as four kinds of particles (belonging to Geldart's B and D groups). The axial and radial voidage distribution with vibration is compared with that without vibration, which shows vibration can aid in the fluidization behaviors of particles. For a larger vibration amplitude, the vibration seriously affects bed voidage. The vibration energy can damp out for particle layers with increasing the bed height. According to analysis of experimental data, an empirical correlation for predicting bed voidage, giving good agreement with the experimental data and a deviation within {+-}15%, was proposed. 20 refs., 8 figs., 2 tabs.

  18. The effect of vibration on bed voidage behaviors in fluidized beds with large particles

    Directory of Open Access Journals (Sweden)

    H. Jin

    2007-09-01

    Full Text Available The effects of vibration parameters, operating conditions and material properties on bed voidage were investigated using an optical fiber probe approach in a vibrating fluidized bed with a diameter of 148 mm. Variables studied included frequency (0-282 s-1, amplitude (0 mm-1 mm, bed height (0.1 m-0.4 m as well as four kinds of particles (belonging to Geldart's B and D groups. The axial and radial voidage distribution with vibration is compared with that without vibration, which shows vibration can aid in the fluidization behaviors of particles. For a larger vibration amplitude, the vibration seriously affects bed voidage. The vibration energy can damp out for particle layers with increasing the bed height. According to analysis of experimental data, an empirical correlation for predicting bed voidage, giving good agreement with the experimental data and a deviation within ±15%, was proposed.

  19. Early motion in a rapidly decompressed particle bed

    Science.gov (United States)

    Zunino, Heather; Adrian, Ronald; Clarke, Amanda

    2016-11-01

    Rapid expansion of dense, pressurized beds of fine particles subjected to rapid reduction of the external pressure is studied in a vertical shock tube. Located at bottom of a high pressure chamber below the shock tube diaphragm, a particle bed expands when the diaphragm bursts, releasing a near-sonic expansion wave that impinges on the particle bed-gas interface. The expansion wave presents a very rapid unloading to the particle bed. A high-speed video camera and pressure sensors capture events occurring during bed expansion. Interesting structures during the first few milliseconds include two-dimensional instabilities of the particle bed's surface and roughly spatially periodic regions void of particles within the bed. One-dimensional and two-dimensional Fourier analyses are used to measure their frequencies in space-time. It is found that the frequencies and patterns exhibit a clear dependence on particle diameter in which cell frequency decreases and cell size increases with increasing particle size. This work is supported by the U.S. Department of Energy, National Nuclear Security Administration, Advanced Simulation and Computing Program, as a Cooperative Agreement under the Predictive Science and Academic Alliance Program, under Contract No. DE-NA0002378.

  20. Effect of bed particles to combustion of gases in fluidized bed

    Energy Technology Data Exchange (ETDEWEB)

    Raiko, R.; Wallen, V.; Etelaeaho, R.; Correia, S. [Tampere Univ. of Technology (Finland). Energy and Process Engineering

    1997-10-01

    The objective of this project was to obtain experimental data on effects of sand particles to the combustion of gases. The effect of the surface area of the particles was tested using different sized particles. The fluidized bed reactor used in these experiments was a stainless-steel tube with an internal diameter of 42 mm surrounded by an electric heater. The test rig was built in the Laboratory of Energy and Process Engineering at Tampere University of Technology. In order to elucidate the possible changes of particle surface, microscopic and porosimetric studies were conducted with both fresh bed particles and used bed particles. These measurements indicate that carbon monoxide significantly reacts with oxygen in the particulate or emulsion phase of a fluidized bed, if the residence time is long enough. The reaction rate depends mainly on temperature, air coefficient, residence time and particle size of the solids. It seems that the combustion enhances if the average particle size increases. Whether this is caused by increased free path length or reduced specific surface area of the bed is yet unknown. The first might be more probable cause because the majority of reactions often took place in the freeboard right above the bed. It was clear that the bed hindered proper combustion in several cases. (orig.)

  1. Particle motions in oscillatory flow over a smooth bed

    DEFF Research Database (Denmark)

    Jensen, Karsten Lindegård; Sumer, B. Mutlu; Fredsøe, Jørgen;

    2014-01-01

    such as the probability distribution of particle position in the vertical, and the horizontal and vertical particle velocities, among others, are determined. The particle is observed to reach heights of 2.5-3d, similar to that characterizing a typical bedload particle in sediment transport.......This study investigates particle motions near the bed in an oscillating tunnel with a smooth bed. Trajectories of a heavy particle were recorded in two dimensions (horizontal and vertical) and in time. The wave boundary layer Reynolds number is Re = 520000. Kinematical quantities...

  2. EFFECT OF VERTICAL BAFFLES ON PARTICLE MIXING AND DRYING IN FLUIDIZED BEDS OF GROUP D PARTICLES

    Institute of Scientific and Technical Information of China (English)

    Chung Lim Law; Siti Masrinda Tasirin; Wan Ramli Wan Daud; Derek Geldart

    2003-01-01

    This study reports the effect of vertical baffles on the group D powder mixing and drying characteristics in a batch fluidized bed dryer. Results obtained in this study showed that operating the fluidized bed dryer with vertical baffles gave better particle mixing. This is due to the fact that the vertical baffles acted to limit the growth of small bubbles into large bubbles and the small bubbles caused more vigorous mixing in the bed of particles before finally erupting at the bed surface. Thus, insertion of vertical baffles is a useful way to process group D particles in a fluidized bed, especially when the fluidized bed is large.

  3. Particle transport in fluidized beds : experiments and stochastic models

    NARCIS (Netherlands)

    Dechsiri, Chutima

    2004-01-01

    Fluidization is a process in which solids are caused to behave like fluid by blowing gas or liquid upwards through the solid-filled reactor. The behavior of a bed of particles within the reactor during the process is very complex and difficult to predict. To make sure that a fluidized bed reactor is

  4. Stochastic analysis of particle movement over a dune bed

    Science.gov (United States)

    Lee, Baum K.; Jobson, Harvey E.

    1977-01-01

    Stochastic models are available that can be used to predict the transport and dispersion of bed-material sediment particles in an alluvial channel. These models are based on the proposition that the movement of a single bed-material sediment particle consists of a series of steps of random length separated by rest periods of random duration and, therefore, application of the models requires a knowledge of the probability distributions of the step lengths, the rest periods, the elevation of particle deposition, and the elevation of particle erosion. The procedure was tested by determining distributions from bed profiles formed in a large laboratory flume with a coarse sand as the bed material. The elevation of particle deposition and the elevation of particle erosion can be considered to be identically distributed, and their distribution can be described by either a ' truncated Gaussian ' or a ' triangular ' density function. The conditional probability distribution of the rest period given the elevation of particle deposition closely followed the two-parameter gamma distribution. The conditional probability distribution of the step length given the elevation of particle erosion and the elevation of particle deposition also closely followed the two-parameter gamma density function. For a given flow, the scale and shape parameters describing the gamma probability distributions can be expressed as functions of bed-elevation. (Woodard-USGS)

  5. Visualization of stress propagation in dynamically compacted wetted particle beds

    Science.gov (United States)

    Marr, Bradley J.; Frost, David L.

    2017-01-01

    The high-strain-rate response of granular media has received considerable attention due to increasing interest in granular penetration. Introduction of a liquid phase into the particle bed alters the global deformation response of the system as the liquid is capable of supporting stresses. In the present study, we investigate the response of arrays of stacked glass rods, both dry and immersed in liquid, under varying drop weight-induced stress loadings. We examine the role of saturation on particle and bed deformation, using well-defined loading conditions and particle bed arrangements. Using high-speed photograph and the photoelastic nature of the glass rods, the propagation of the stress wave through the two-phase system can be visualized. The liquid phase was seen to contribute to the mean stress transfer within the system, resulting in reduced total driver displacements as well as increased bed strains at the time when particle fracturing was first observed.

  6. Control of the Bed Temperature of a Circulating Fluidized Bed Boiler by using Particle Swarm Optimization

    Directory of Open Access Journals (Sweden)

    AYGUN, H.

    2012-05-01

    Full Text Available Circulating fluidized bed boilers are increasingly used in the power generation due to their higher combustion efficiency and lower pollutant emissions. Such boilers require an effective control of the bed temperature, because it influences the boiler combustion efficiency and the rate of harmful emissions. A Particle-Swarm-Optimization-Proportional-Integrative-Derivative (PSO-PID controller for the bed temperature of a circulating fluidized bed boiler is presented. In order to prove the capability of the proposed controller, its performances are compared at different boiler loads with those of a Fuzzy Logic (FL controller. The simulation results demonstrate some advantages of the proposed controller.

  7. A particle counting system for calculation of bedload fluxes

    Science.gov (United States)

    Mendes, Luís; Antico, Federica; Sanches, Pedro; Alegria, Francisco; Aleixo, Rui; Ferreira, Rui M. L.

    2016-12-01

    Channel bed morphology depends on bedload fluxes which are difficult to determine even in controlled laboratory conditions. Particle counting can provide time resolved bedload fluxes. Determination of particle rates by means of digital image processing is computationally expensive and the requirement for optical access is not always met. Weighing methods are limited by short dynamic ranges. To overcome these difficulties this paper presents a prototype of a particle counter device that works by detecting impacts on a sensitive surface. The accuracy of the device is validated, by means of laboratory experiments, contrasting its results against those obtained by means of digital image analysis. This device proved to be capable of measuring bedload fluxes, determining long time series of bedload transport rates, in particles per unit time, with high accuracy and with a much lower computation cost relatively to digital image processing. The device is also able to gather meaningful data in real-time, like particle arrival time-series and real-time lateral bedload distribution. The parameters involved in the detection criterion must be previously set through a heuristic procedure. However, the method itself is direct—it requires no calibration between the acquired signal and bedload transport rates. Particle counts can be transformed in bedload discharges by a simple binning process or by taking finite differences of the cumulative mass function. First and second order moments of bedload discharge are in agreement with the values obtained by direct counting. The low requirement for data storage, allowing for very large data series, the real time analysis capabilities, the low cost of such system when compared with a digital image acquisition system constitute the main advantages of the device for the study of integral scales of bedload and bedload intermittency.

  8. Gas-particle interactions in dense gas-fluidised beds

    NARCIS (Netherlands)

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

    2003-01-01

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

  9. Particle Distribution in a Fixed Bed Down Draft Wood Gasifier

    DEFF Research Database (Denmark)

    Hindsgaul, Claus

    2005-01-01

    Char particle samples were collected from six distances above the grate in a fixed bed of a down draft biomass gasifier. Each sample was separated into twelve size fractions by screening through standard sieves in order to determine the local particle size distribution. The ash contents of each...

  10. Particle Dynamics and Gravel-Bed Adjustments

    Science.gov (United States)

    1993-05-01

    detecteur des movement des sediments fins. Societe hydrotechnique de France. Transport Hydraulique et Decantation des Materiaux Solides. pp3 9 p. 38...Kirkby, MJ. (Eds.) Channel Ndork Hydrology. Wiley. Chichester. pp 129-173. 67. Lapointe, M.F. (1992) Burst-like sediment suspension events in a sand bed...alluvial sand suspension by eddy correlation. Earth Surface Processes & Landforms, 11, (in press). 69. Soulsby, R.L. (1983) The bottom boundary layer of

  11. Single particle behaviour in circulating fluidized bed combustors

    DEFF Research Database (Denmark)

    Erik Weinell, Claus

    1994-01-01

    of fuel particles in a boiler. A cold pilot scale model of a circulating fluidized bed combustor was used. Here sand was recirculated by means of air. Pressure measurements along the riser determined suspension density. A radioactive tracking facility to determined the dynamic picture of the particle....... The tracer particles moved between the zones with a mean frequency of ca. 1 Hz. The upwards particle velocity in the upper dilute transport zone decreased with particle size and density, resulting in a decreased number of particle observations for the larger particles with the riser height. The particles...... kept their axial course within relatively short ranges but this pattern was wiped out at larger distances. The mean particle residence time in the zone above and below the secondary air inlet was almost independent of particle characteristics, but was proportional to the magnitude of the internal...

  12. Confined fluidization of fines in fixed bed of coarse particles

    Directory of Open Access Journals (Sweden)

    Buczek Bronisław

    2016-12-01

    Full Text Available Experiments on a confined fluidized bed system with various shapes of particles have been presented in the paper. Its influence on hydrodynamic properties in the whole range of gas velocity has been analysed. Relations allowing calculation of the Richardson-Zaki-type equation coefficients, including description of inter-particle void and gas pressure drop in such systems have been determined. Necessary condition for confined fluidization of non-spherical coarse particles has also been determined.

  13. Flux-assisted infiltration of molten 6063-Al into TiC beds

    Energy Technology Data Exchange (ETDEWEB)

    Lopez, V.H.; Kennedy, A.R. [Advanced Materials Group, School of Mechanical, Materials, Mfg. Engineering and Management, Nottingham Univ. (United Kingdom)

    2003-07-01

    This study details trials to produce aluminium metal matrix composites reinforced with TiC particles by means of a flux-assisted infiltration technique. TiC and mixtures of TiC/flux powders were packed into 6063-aluminium tubes and heated to temperatures between 680 C and 1100 C in an Ar atmosphere. No infiltration of pure TiC beds occurred but the effect of using a K-Al-F flux was dramatic. Full infiltration occurred in less than 15 minutes and at low temperatures, 680 C. Differential scanning calorimetry (DSC) experiments indicate that only two significant thermal events take place in the process, melting of the flux at approximately 545 C and melting of the aluminium alloy at 630 C. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) showed TiC-free regions, slight reaction of the TiC to form TiAl{sub 3}, and in some cases Al{sub 4}C{sub 3}, and a random distribution of flux trapped in the aluminum matrix. (orig.)

  14. Estimation of particle concentration profiles in a three-phase fluidized bed from experimental data and using the wake model

    Directory of Open Access Journals (Sweden)

    Knesebeck A.

    2004-01-01

    Full Text Available Particles with a size distribution in the range of 34 to 468 µm were fluidized in a three-phase bed using low liquid and gas velocities. Particle size distribution and pressure profile measurements were carried out at different locations in the bed in order to study the influence of fluid velocities on segregation and dispersion of particles in different size classes. The influence of gas velocity on particle mixing was analyzed in terms of internal solid fluxes, calculated by means of the wake model. Based on the experimental results, different particle distribution patterns were identified. Although no significant tendencies were observed for radial profiles, particles of different sizes have significantly different axial profiles, which are mainly affected by the velocity of the liquid phase. Thus, depending on the liquid velocity, smaller particles reach a maximum concentration at different bed heights.

  15. Deleterious Thermal Effects Due To Randomized Flow Paths in Pebble Bed, and Particle Bed Style Reactors

    Science.gov (United States)

    Moran, Robert P.

    2013-01-01

    A review of literature associated with Pebble Bed and Particle Bed reactor core research has revealed a systemic problem inherent to reactor core concepts which utilize randomized rather than structured coolant channel flow paths. For both the Pebble Bed and Particle Bed Reactor designs; case studies reveal that for indeterminate reasons, regions within the core would suffer from excessive heating leading to thermal runaway and localized fuel melting. A thermal Computational Fluid Dynamics model was utilized to verify that In both the Pebble Bed and Particle Bed Reactor concepts randomized coolant channel pathways combined with localized high temperature regions would work together to resist the flow of coolant diverting it away from where it is needed the most to cooler less resistive pathways where it is needed the least. In other words given the choice via randomized coolant pathways the reactor coolant will take the path of least resistance, and hot zones offer the highest resistance. Having identified the relationship between randomized coolant channel pathways and localized fuel melting it is now safe to assume that other reactor concepts that utilize randomized coolant pathways such as the foam core reactor are also susceptible to this phenomenon.

  16. Dynamics of fine particles in liquid-solid fluidized beds

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    On the basis of the Local Equilibrium Model (LEM), fine particles with large Richardson-Zaki exponent n show, under certain conditions during bed expansion and collapse, different dynamic behavior from particles with small n. For an expansion process there may be a concentration discontinuity propagating upward from the distributor, and, on the contrary, for a collapse process there may be a progressively broadening and upward-propagating continuous transition zone instead of discontinuity. The predictions of the bed height variation and the discontinuity trace have been validated experimentally.

  17. Diffusion of bed load particles subject to different flow conditions

    Science.gov (United States)

    Cecchetto, Martina; Cotterle, Luca; Tregnaghi, Matteo; Tait, Simon; Marion, Andrea

    2015-04-01

    An in-depth understanding of sediment motion in rivers has acquired increasing importance lately in order to plan restoration activities that provide ecological benefit. River beds constitute the interfacial environment where several species live and mass exchange of sediments/nutrients/pollutants can take place. Moving grains interacting with the bed deposit and can locally change the bed surface topography they can also act as carriers for contaminants associated with the grains. Study the motion of grains on the bed, in particular the extent and variability of their travel distance with regards to the flow conditions can provide information on the transport of grain associated contaminants. The results of a series of experimental tests, in which increasing levels of boundary shear stress were applied over a bed deposit of natural river gravel, are reported. Image databases consisted of a series of bed images acquired at a frequency of 45 Hz were collected. Analysis of the images has provided time and position data to plot the trajectories of more than 200 moving grains for each test. This data enables the derivation of the statistics of the un-truncated probability distribution of the detected particles' step length, which is consider as the distance moved by a particle from the moment it is entrained to the instant it stops on the bed. In recent studies the movement of bed load material has been indicated as diffusive, but little is known about the spatial and temporal scales of this diffusion. The analysis of the longitudinal and transverse trajectories for the tracked particles has here revealed three regimes of diffusion: a ballistic diffusion which takes place at the very beginning of particles motion, an anomalous intermediate regime, and a normal subdiffusion which occurs for larger times. Characteristic time scales separate these three diffusive regimes. Results show that in experiments with higher shear stresses the time scale separating the ballistic

  18. Dynamics and mechanics of bed-load tracer particles

    Directory of Open Access Journals (Sweden)

    C. B. Phillips

    2014-12-01

    Full Text Available Understanding the mechanics of bed load at the flood scale is necessary to link hydrology to landscape evolution. Here we report on observations of the transport of coarse sediment tracer particles in a cobble-bedded alluvial river and a step-pool bedrock tributary, at the individual flood and multi-annual timescales. Tracer particle data for each survey are composed of measured displacement lengths for individual particles, and the number of tagged particles mobilized. For single floods we find that measured tracer particle displacement lengths are exponentially distributed; the number of mobile particles increases linearly with peak flood Shields stress, indicating partial bed load transport for all observed floods; and modal displacement distances scale linearly with excess shear velocity. These findings provide quantitative field support for a recently proposed modeling framework based on momentum conservation at the grain scale. Tracer displacement is weakly negatively correlated with particle size at the individual flood scale; however cumulative travel distance begins to show a stronger inverse relation to grain size when measured over many transport events. The observed spatial sorting of tracers approaches that of the river bed, and is consistent with size-selective deposition models and laboratory experiments. Tracer displacement data for the bedrock and alluvial channels collapse onto a single curve – despite more than an order of magnitude difference in channel slope – when variations of critical Shields stress and flow resistance between the two are accounted for. Results show how bed load dynamics may be predicted from a record of river stage, providing a direct link between climate and sediment transport.

  19. Dynamical simulation of fluidized beds - hydrodynamically interacting granular particles

    CERN Document Server

    Ichiki, K; Ichiki, Kengo; Hayakawa, Hisao

    1995-01-01

    A numerical simulation of a gas-fluidized bed is performed without introduction of any empirical parameters. Realistic bubbles and slugs are observed in our simulation. It is found that the convective motion of particles is important for the bubbling phase and there is no convection in the slugging phase. From the simulation results, non-Gaussian distributions are found in the particle velocities and the relation between the deviation from Gaussian and the local density of particles is suggested. It is also shown that the power spectra of particle velocities obey power laws. A brief explanation on the relationship between the simulation results and the Kolmogorov scaling argument is discussed.

  20. Experimental Study on an On-Line Measurement of High Temperature Circulating Ash Flux in a Circulating Fluidized Bed Boiler

    Institute of Scientific and Technical Information of China (English)

    Lu Xiaofeng; Li Yourong

    2001-01-01

    A new kind of measuring method that may be used to measure high temperature circulating solid particles flux in a circulating fluidized bed boiler is studied in this paper. The measuring method is founded on the principle of thermal equilibrium. A series of cold tests and hot tests were carried to optimize the structure and collocation of water-cooling tubes and showed that the method had the advantage of simple, accurate, reliable and good applicability for on-line usage in a circulating fluidized bed boiler.

  1. Particle-scale simulation of fluidized bed with immersed tubes

    Institute of Scientific and Technical Information of China (English)

    Yongzhi ZHAO; Maoqiang JIANG; Yi CHENG

    2008-01-01

    In order to simulate gas-solids flows with complex geometry,the boundary element method was incorporated into the implementation of a combined model of computational fluid dynamics and discrete element method.The resulting method was employed to simulate hydrodynamics in a fluidized bed with immersed tubes.The transient simulation results showed particle and bubble dynamics.The bubble coalescence and break-up behavior when passing the immersed tubes was successfully predicted.The gas-solid flow pattern in the fluidized bed is changed greatly because of the immersed tubes.As particles and gas are come in contact with the immersed tubes,the gas bubbles will be deformed.The collisions between particles arid tubes will make the tubes sur-rounded by air pockets most of the time and this is unfavorable for the heat transfer between particles and tubes.

  2. DISCRETE PARTICLE SIMULATION OF SIZE SEGREGATION OF PARTICLE MIXTURES IN A GAS FLUIDIZED BED

    Institute of Scientific and Technical Information of China (English)

    Y. Q. Feng; A. B. Yu

    2006-01-01

    This paper presents a study of the mixing/segregation behaviour of particle mixtures in a gas fluidized bed by use of the discrete particle simulation. Spherical particles with diameters 2 mm (jetsam) and 1 mm (flotsam) and density 2 500 kg·m-3 are used as solid mixtures with different volume fractions. The particles are initially packed uniformly in a rectangular bed and then fluidized by gas uniformly injected at the bottom of the bed. The gas injection velocities vary to cover fixed, partially and fully fluidized bed conditions. Segregation/mixing behaviour is discussed in terms of flow patterns, solid concentration profile and mixing kinetics. The results show that segregation, as a transient fluidization process, is strongly affected by gas injection velocities for a given particle mixture. With the increase of the volume fraction of flotsam, size segregation appears at lower velocities.

  3. Single-particle behaviour in circulating fluidized beds

    DEFF Research Database (Denmark)

    Weinell, Claus Erik; Dam-Johansen, Kim; Johnsson, Jan Erik

    1997-01-01

    This paper describes an experimental investigation of single-particle behaviour in a cold pilot-scale model of a circulating fluidized bed combustor (CFBC). In the system, sand is recirculated by means of air. Pressure measurements along the riser are used to determine the suspension density...

  4. Universal shape evolution of particles by bed-load

    Science.gov (United States)

    Jerolmack, D. J.; Domokos, G.; Shaw, S.; Sipos, A.; Szabo, T.

    2016-12-01

    River currents, wind and waves drive bed-load transport, in which sediment particles collide with each other and the Earth's surface. A generic consequence is erosion and rounding of particles as a result of chipping, often referred to in geological literature as abrasion. Recent studies have shown that the erosion of river pebbles can be modeled as diffusion of surface curvature, indicating that geometric aspects of chipping erosion are insensitive to details of collisions and material properties. Here we present data from fluvial, aeolian and coastal environments that suggest a universal relation between particle circularity and mass lost due to bed-load chipping. Simulations and experiments support the diffusion model and demonstrate that three constraints are required to produce this universal curve: (i) initial particles are fragments; (ii) erosion is dominated by collisions among like-sized particles; and (iii) collision energy is small enough that chipping dominates over fragmentation. We show that the mechanics of bedrock weathering and bed-load transport select these constraints, providing the foundation to estimate a particle's erosion rate from its shape alone in most sedimentary environments. These findings may be used to determine the contribution of chipping to downstream fining in rivers and deserts, and to infer transport conditions using only images of sediment grains.

  5. Annual particle flux observations over a heterogeneous urban area

    DEFF Research Database (Denmark)

    Järvi, L.; Rannik, Ü.; Mammarella, I.;

    2009-01-01

    in different wind directions on the measured fluxes. The particle number fluxes were highest in the direction of a local road on weekdays, with a daytime median flux of 0.8×109 m−2 s−1. The particle fluxes showed a clear dependence on traffic rates and on the mixing conditions of the boundary layer....... The measurement footprint was estimated by the use of both numerical and analytical models. Using the crosswind integrated form of the footprint function, we estimated the emission factor for the mixed vehicle fleet, yielding a median particle number emission factor per vehicle of 3.0×1014 # km−1. Particle fluxes...... stationary combustion sources are also highest. Particle number fluxes were compared with the simultaneously measured CO2 fluxes and similarity in their sources was distinguishable. For CO2, the median emission factor of vehicles was estimated to be 370 g km−1....

  6. Heat-transfer characteristics of flowing and stationary particle-bed-type fusion-reactor blankets

    Energy Technology Data Exchange (ETDEWEB)

    Nietert, R.E.

    1983-02-01

    The following five appendices are included: (1) physical properties of materials, (2) thermal entrance length Nusselt number variations, (3) stationary particle bed temperature variations, (4) falling bed experimental data and calculations, and (5) stationary bed experimental data and calculations. (MOW)

  7. A turbulent bed contactor: energetic efficiency for particle collection

    Directory of Open Access Journals (Sweden)

    M. L. Gimenes

    2007-03-01

    Full Text Available Particle collection experiments were conducted in a fluidizing irrigated bed to evaluate the performance of mobile packings: 38 x 50 mm plain oblate spheroids 38 mm ID plain spheres and alternative perforated spheres with a 38 mm ID and 10% and 25% free areas were used as fluidizing media in a 0.264 m diameter and 1.20 m high turbulent bed contactor (TBC. Particle collection experiments were carried out above the minimum fluidization velocity, using as particulate test powder polysized alumina (size 1.5 to 5.5 mm. Experimental results demonstrated that the perforated spheres performed better in collecting particles than the other packings tested. The efficiency of particle collection was analysed based on energy consumption in the TBC, using the energetic efficiency concept. It was verified that not much more energy was consumed per unit of gas flow in fluidized beds of perforated packings than in those of conventional plain sphere packings, since the perforated spheres were more energetically efficient for particle collection than plain spheres and oblate spheroid packings.

  8. High power density reactors based on direct cooled particle beds

    Science.gov (United States)

    Powell, J. R.; Horn, F. L.

    Reactors based on direct cooled High Temperature Gas Cooled Reactor (HTGR) type particle fuel are described. The small diameter particle fuel is packed between concentric porous cylinders to make annular fuel elements, with the inlet coolant gas flowing inwards. Hot exit gas flows out along the central channel of each element. Because of the very large heat transfer area in the packed beds, power densities in particle bed reactors (PBRs) are extremely high resulting in compact, lightweight systems. Coolant exit temperatures are high, because of the ceramic fuel temperature capabilities, and the reactors can be ramped to full power and temperature very rapidly. PBR systems can generate very high burst power levels using open cycle hydrogen coolant, or high continuous powers using closed cycle helium coolant. PBR technology is described and development requirements assessed.

  9. HYDRODYNAMIC CHARACTERISTICS OF FLUIDIZED BEDS CONTAINING LARGE POLYDISPERSED PARTICLES

    Directory of Open Access Journals (Sweden)

    K. TANNOUS

    1998-03-01

    Full Text Available This paper presents a hydrodynamic study of fluidized beds containing large polydispersed particles (B and D categories of Geldart’s classification. The experiments have been carried out with particle samples characterized by the Rosin-Rammler-Sperling (RRS size distribution. The parameters analyzed in this study are the dispersion index and the average particle diameter obtained from the RRS size distribution model. Correlations to estimate the initial and complete fluidization velocities and the segregation velocity as a function of these two size distribution parameters have been established.

  10. Measurement of magnetic fluctuation-induced particle flux (invited).

    Science.gov (United States)

    Ding, W X; Brower, D L; Yates, T Y

    2008-10-01

    Magnetic field fluctuation-induced particle transport has been directly measured in the high-temperature core of the MST reversed field pinch plasma. Measurement of radial particle transport is achieved by combining various interferometry techniques, including Faraday rotation, conventional interferometry, and differential interferometry. It is observed that electron convective particle flux and its divergence exhibit a significant increase during a sawtooth crash. In this paper, we describe the basic techniques employed to determine the particle flux.

  11. On vertical particle fluxes in the Caspian Sea

    Science.gov (United States)

    Lukashin, V. N.; Lisitzin, A. P.; Novigatsky, A. N.; Musaeva, E. I.; Ambrosimov, A. K.; Gayvoronskaya, L. A.

    2014-03-01

    The first results of studies of vertical fluxes of sediment particles using the sediment traps at the Trans-Caspian section are presented. The flux values and distribution regularities are established. The fluxes of particles forming the sediment are also determined. The intra-annual variability in the fluxes corresponds to the seasonal variability of the biological activity. Above the northern slope of the Derbent Basin, the maximum vertical fluxes are recorded in the winter, which is caused by the intensification of the near-bottom currents.

  12. Cementation of copper onto brass particles in a packed bed

    Directory of Open Access Journals (Sweden)

    Stanković Velizar D.

    2004-01-01

    Full Text Available The process of copper ion cementation from dilute solution was investigated using a packed bed column filled with brass particles. The influence of initial pH value of the treated solution, particle size and the solution flow rate on the cementation process was determined. It was observed that, in general, the process rate passes through an initial period of particle surface activation; a period of constant rate and a period of decreasing rate. Increasing the initial pH value of treated solution, the rate of cementation has significantly been slowed down and, at pH > 2.6, the process becomes very slow due to an H+-ions consumption and consequently measurable change of pH during the process. Using a packed bed of brass particles, it is possible to remove copper ions from feeding stream to a degree higher than 95% for about 20 - 30 minutes, i.e. an initial copper concentration of about 250 mg/dm3can be reduced to less than 10 mg/dm3. For an hour of the process time the initial level of Cu2+ can reach a value less than 1 ppm, meaning the investigated process is highly efficient. The concentration of zinc in the solution after cementation is about twice higher than the initial copper concentration in the feeding solution. The method of packed bed cementation, using brass particles, which are usually a secondary material for re-melting, could particularly be favorable instead of the conventional one, because zinc dust is being substituted with some less valuable starting material that could be upgraded on copper before its re-melting.

  13. Suprathermal Charged Particle Acceleration by Small-scale Flux Ropes.

    Science.gov (United States)

    Zank, G. P.; le Roux, J. A.; Webb, G. M.

    2015-12-01

    We consider different limits of our recently developed kinetic transport theory to investigate the potential of super-Alvenic solar wind regions containing several small-scale flux ropes to explain the acceleration of suprathermal ions to power-law spectra as observations show. Particle acceleration is modeled in response to flux-rope activity involving contraction, merging (reconnection), and collisions in the limit where the particle gyoradius is smaller than the characteristic flux-rope scale length. The emphasis is mainly on the statistical variance in the electric fields induced by flux-rope dynamics rather than on the mean electric field induced by multiple flux ropes whose acceleration effects are discussed elsewhere. Our steady-state analytical solutions suggest that particle drift acceleration by flux ropes, irrespective of whether displaying incompressible or compressible behavior, can yield power laws asymptotically at higher energies whereas an exponential spectral rollover results asymptotically when field-aligned guiding center motion acceleration occur by reconnection electric fields from merging flux ropes. This implies that at sufficiently high particle energies, drift acceleration might dominate. We also expect compressive flux ropes to yield harder power-law spectra than incompressible flux ropes. Preliminary results will be discussed to illustrate how particle acceleration might be affected when both diffusive shock and small-scale flux acceleration occur simultaneously at interplanetary shocks.

  14. Simultaneous coastal measurements of ozone deposition fluxes and iodine-mediated particle emission fluxes with subsequent CCN formation

    Directory of Open Access Journals (Sweden)

    J. D. Whitehead

    2010-01-01

    Full Text Available Here we present the first observations of simultaneous ozone deposition fluxes and ultrafine particle emission fluxes over an extensive infra-littoral zone. Fluxes were measured by the eddy covariance technique at the Station Biologique de Roscoff, on the coast of Brittany, north-west France. This site overlooks a very wide (3 km littoral zone controlled by very deep tides (9.6 m exposing extensive macroalgae beds available for significant iodine mediated photochemical production of ultrafine particles. The aspect at the Station Biologique de Roscoff provides an extensive and relatively flat, uniform fetch within which micrometeorological techniques may be utilized to study links between ozone deposition to macroalgae (and sea water and ultrafine particle production.

    Ozone deposition to seawater at high tide was significantly slower (vd[O3]=0.302±0.095 mm s−1 than low tidal deposition. A statistically significant difference in the deposition velocities to macroalgae at low tide was observed between night time (vd[O3]=1.00±0.10 mm s−1 and daytime (vd[O3]=2.05±0.16 mm s−1 when ultrafine particle formation results in apparent particle emission. Very high emission fluxes of ultrafine particles were observed during daytime periods at low tides ranging from 50 000 particles cm−2 s−1 to greater than 200 000 particles cm−2 s−1 during some of the lowest tides. These emission fluxes exhibited a significant relationship with particle number concentrations comparable with previous observations at another location. Apparent particle growth rates were estimated to be in the range 17–150 nm h−1 for particles in the size range 3–10 nm. Under certain conditions, particle growth may be inferred to continue to greater than 120 nm over tens

  15. Model for boiling and dryout in particle beds. [LMFBR

    Energy Technology Data Exchange (ETDEWEB)

    Lipinski, R. J.

    1982-06-01

    Over the last ten years experiments and modeling of dryout in particle beds have produced over fifty papers. Considering only volume-heated beds, over 250 dryout measurements have been made, and are listed in this work. In addition, fifteen models to predict dryout have been produced and are discussed. A model is developed in this report for one-dimensional boiling and dryout in a porous medium. It is based on conservation laws for mass, momentum, and energy. The initial coupled differential equations are reduced to a single first-order differential equation with an algebraic equation for the upper boundary condition. The model includes the effects of both laminar and turbulent flow, two-phase friction, and capillary force. The boundary condition at the bed bottom includes the possibility of inflowing liquid and either an adiabatic or a bottom-cooled support structure. The top of the bed may be either channeled or subcooled. In the first case the channel length and the saturation at the base of the channels are predicted. In the latter case, a criterion for penetration of the subcooled zone by channels is obtained.

  16. SPOUTED BED DESIGN CONSIDERATIONS FOR COATED NUCLEAR FUEL PARTICLES

    Energy Technology Data Exchange (ETDEWEB)

    Marshall, Douglas W.

    2017-07-01

    High Temperature Gas Cooled Reactors (HTGRs) are fueled with tristructural isotropic (TRISO) coated nuclear fuel particles embedded in a carbon-graphite fuel body. TRISO coatings consist of four layers of pyrolytic carbon and silicon carbide that are deposited on uranium ceramic fuel kernels (350µm – 500µm diameters) in a concatenated series of batch depositions. Each layer has dedicated functions such that the finished fuel particle has its own integral containment to minimize and control the release of fission products into the fuel body and reactor core. The TRISO coatings are the primary containment structure in the HTGR reactor and must have very high uniformity and integrity. To ensure high quality TRISO coatings, the four layers are deposited by chemical vapor deposition (CVD) using high purity precursors and are applied in a concatenated succession of batch operations before the finished product is unloaded from the coating furnace. These depositions take place at temperatures ranging from 1230°C to 1550°C and use three different gas compositions, while the fuel particle diameters double, their density drops from 11.1 g/cm3 to 3.0 g/cm3, and the bed volume increases more than 8-fold. All this is accomplished without the aid of sight ports or internal instrumentation that could cause chemical contamination within the layers or mechanical damage to thin layers in the early stages of each layer deposition. The converging section of the furnace retort was specifically designed to prevent bed stagnation that would lead to unacceptably high defect fractions and facilitate bed circulation to avoid large variability in coating layer dimensions and properties. The gas injection nozzle was designed to protect precursor gases from becoming overheated prior to injection, to induce bed spouting and preclude bed stagnation in the bottom of the retort. Furthermore, the retort and injection nozzle designs minimize buildup of pyrocarbon and silicon carbide on the

  17. Hydrodynamics of multi-sized particles in stable regime of a swirling bed

    Energy Technology Data Exchange (ETDEWEB)

    Miin, Chin Swee; Sulaiman, Shaharin Anwar; Raghavan, Vijay Raj; Heikal, Morgan Raymond; Naz, Muhammad Yasin [Universiti Teknologi PETRONAS, Perak (Malaysia)

    2015-11-15

    Using particle imaging velocimetry (PIV), we observed particle motion within the stable operating regime of a swirling fluidized bed with an annular blade distributor. This paper presents velocity profiles of particle flow in an effort to determine effects from blade angle, particle size and shape and bed weight on characteristics of a swirling fluidized bed. Generally, particle velocity increased with airflow rate and shallow bed height, but decreased with bed weight. A 3 .deg. increase in blade angle reduced particle velocity by approximately 18%. In addition, particle shape, size and bed weight affected various characteristics of the swirling regime. Swirling began soon after incipience in the form of a supra-linear curve, which is the characteristic of a swirling regime. The relationship between particle and gas velocities enabled us to predict heat and mass transfer rates between gas and particles.

  18. Particle fluctuation velocity in gas-fluidized beds

    Science.gov (United States)

    Cody, George

    1998-11-01

    The stability of the uniform state of a gas-fluidized bed was first discussed by Wilhelm and Kwauk in 1948, modeled by Jackson in 1963, and summarized in empirical rules by Geldart in 1973. Particles (Geldart-A) below a critical diameter fluidize before bubbling, and those above that diameter (Geldart-B) bubble at fluidization - why? The critical stability parameter is the mean-squared particle fluctuation velocity, or granular temperature, T*. It was first measured for monodispersed glass spheres by acoustic shot-noise excitation of the wall (Cody et al., 1996), and by diffusing-wave optical spectroscopy at the wall (Menon and Durian, 1997). For Geldart-B spheres the data agree, and both agree with a recent statistical model for T* based on random particle impact (Buyevich and Kapbasov, 1998). T* of Cody et al. jumps by tenfold at the Geldart-B/A transition, sufficient to make these Geldart-A spheres stable in the Jackson theory. It is proposed that the absence of this jump in the Menon and Durian data reflects the significant difference in bed geometry and circulation in the two experiments, and the dominant effect of random shear fluctuations on T* for sphere diameters in the Geldart-A regime (Cody, Kapbasov, Buyevich, Symp. B-1, Annual Meeting. AIChE 11/15-20/98).

  19. Ultrafine particle number flux over and in a deciduous forrest

    DEFF Research Database (Denmark)

    Pryor, S.C.; Barthelmie, R.J.; Larsen, Søren Ejling

    2017-01-01

    Ultrafine particles (UFP, particles with diameters (Dp) particles. Long-term flux measurements from a deciduous forest in the Midwestern USA (taken during December...... 2012 to May 2014) show that although a substantial fraction of the data period indicates upward fluxes of UFP, on average, the forest is a net sink for UFP during both leaf-active and leaf-off periods. The overall mean above-canopy UFP number flux computed from this large data set is −4.90 × 106 m−2 s...... the canopy mean flux is shown to be downward throughout the day (except at 23.00) with largest-magnitude fluxes during the middle of the day. On average, nearly three quarters of the total UFP capture by this ecosystem occurs at the canopy. This fraction increases to 78% during the leaf-active period...

  20. Experimental study of sediment particle diffusion on a granular bed.

    Science.gov (United States)

    Antico, Federica; Sanches, Pedro; Fent, Ilaria; Ferreira, Rui M. L.

    2016-04-01

    Particle diffusion in a cohesionless granular bed, hydraulically fully rough, subjected to a steady-uniform turbulent open-channel flow is investigated. Experiments were carried out under conditions of weak bedload transport in a 12.5 m long and 40.5 cm wide glass-sided flume recirculating water and sediment through independent circuits at the Laboratory of Hydraulics and Environment of Instituto Superior Técnico, Lisbon. The flume bed was divided in two reaches: a fixed reach comprising 1.5 m of large boulders, followed by 3.0 m of smooth bottom (PVC) and 2.5 m of one layer glued 5.0 mm diameter spherical glass beads; a mobile reach 4.0 m long and 2.5 cm deep filled with 5.0 mm diameter glass packed beads. Particle velocities were obtained introducing 5.0 mm diameter white-coated beads in the flow. Particle motion was registered from above using a high-speed camera AVT Bonito CL-400 with resolution set to 2320 x 1000 px2and frame rate of 170 fps. The field of view recorded was 77.0 cm long and 38.0 cm wide, covering almost all the width of the flume. Image processing allowed detecting and locating the centre of mass of the particles with sub-pixel accuracy. Particle trajectories were reconstructed by tracking the beads in the images; particle velocities were obtained as bead displacement over time interval between two consecutive frames (1/170 s). The computation of lagrangian statistics of particle velocities for a Shields parameter θ=0.014, Froude number Fr=0.756, boundary Reynolds number Re*=182.9 and run duration of 20 min (during which 1218 particle trajectories were collected) provided information about particle diffusion within the local and intermediate range of temporal and space scales. Mean particle velocities, second, third and fourth order moments were obtained for both longitudinal and transverse velocity components. A relatively large ballistic range, approximately two particle diameters, was observed, mainly due to the simple bed topography of

  1. Some parametric flow analyses of a particle bed fuel element

    Energy Technology Data Exchange (ETDEWEB)

    Dobranich, D.

    1993-05-01

    Parametric calculations are performed, using the SAFSIM computer program, to investigate the fluid mechanics and heat transfer performance of a particle bed fuel element. Both steady-state and transient calculations are included, addressing such issues as flow stability, reduced thrust operation, transpiration drag, coolant conductivity enhancement, flow maldistributions, decay heat removal, flow perturbations, and pulse cooling. The calculations demonstrate the dependence of the predicted results on the modeling assumptions and thus provide guidance as to where further experimental and computational investigations are needed. The calculations also demonstrate that both flow instability and flow maldistribution in the fuel element are important phenomena. Furthermore, results are encouraging that geometric design changes to the element can significantly reduce problems related to these phenomena, allowing improved performance over a wide range of element power densities and flow rates. Such design changes will help to maximize the operational efficiency of space propulsion reactors employing particle bed fuel element technology. Finally, the results demonstrate that SAFSIM is a valuable engineering tool for performing quick and inexpensive parametric simulations addressing complex flow problems.

  2. Turbulent particle flux to a perfectly absorbing surface

    DEFF Research Database (Denmark)

    Mann, J.; Ott, Søren; Pecseli, H.L.

    2005-01-01

    average of the inward particle flux through the surface of this moving sphere. The variation of the flux with the radius in the sphere of interception, as well as the variation with basic flow parameters is described well by a simple model, in particular for radii smaller than a characteristic length...

  3. Particle size effects in particle-particle triboelectric charging studied with an integrated fluidized bed and electrostatic separator system

    Science.gov (United States)

    Bilici, Mihai A.; Toth, Joseph R.; Sankaran, R. Mohan; Lacks, Daniel J.

    2014-10-01

    Fundamental studies of triboelectric charging of granular materials via particle-particle contact are challenging to control and interpret because of foreign material surfaces that are difficult to avoid during contacting and measurement. The measurement of particle charge itself can also induce charging, altering results. Here, we introduce a completely integrated fluidized bed and electrostatic separator system that charges particles solely by interparticle interactions and characterizes their charge on line. Particles are contacted in a free-surface fluidized bed (no reactor walls) with a well-controlled fountain-like flow to regulate particle-particle contact. The charged particles in the fountain are transferred by a pulsed jet of air to the top of a vertically-oriented electrostatic separator consisting of two electrodes at oppositely biased high voltage. The free-falling particles migrate towards the electrodes of opposite charge and are collected by an array of cups where their charge and size can be determined. We carried out experiments on a bidisperse size mixture of soda lime glass particles with systematically varying ratios of concentration. Results show that larger particles fall close to the negative electrode and smaller particles fall close to the positive electrode, consistent with theory and prior experiments that larger particles charge positively and smaller particles charge negatively. The segregation of particles by charge for one of the size components is strongest when its collisions are mostly with particles of the other size component; thus, small particles segregate most strongly to the negative sample when their concentration in the mixture is small (and analogous results occur for the large particles). Furthermore, we find additional size segregation due to granular flow, whereby the fountain becomes enriched in larger particles as the smaller particles are preferentially expelled from the fountain.

  4. Statistics of Flux Vacua for Particle Physics

    CERN Document Server

    Watari, Taizan

    2015-01-01

    Supersymmetric flux compactification of F-theory in the geometric phase yields numerous vacua, and provides an ensemble of low-energy effective theories with different symmetry, matter multiplicity and Lagrangian parameters. Theoretical tools have already been developed so that we can study how the statistics of flux vacua depend on the choice of symmetry and some of Lagrangian parameters. In this article, we estimate the fraction of i) vacua that have a U(1) symmetry for spontaneous R-parity violation, and ii) those that realise ideas which achieve hierarchical eigenvalues of the Yukawa matrices. We also learn a lesson that the number of flux vacua is reduced very much when the unbroken $U(1)_Y$ symmetry is obtained from a non-trivial Mordell--Weil group, while it is not when $U(1)_Y$ is in SU(5) unification. It also turns out that vacua with an approximate U(1) symmetry forms a locus of accumulation points of the flux vacua distribution.

  5. The role of particle-particle interactions in bubbling gas-fluidized beds of Geldart A particles: A discrete particle study

    NARCIS (Netherlands)

    Wang, Junwu; Hoef, van der M.A.; Kuipers, J.A.M.

    2009-01-01

    Discrete particle simulations are by now well established as an effective tool to study the mechanics of complex gas-solid flows in gas-fluidized beds. In this study, a state-of-the-art discrete particle model is used to explore the role of particle-particle interactions in bubbling gas-fluidized be

  6. The suspended sediment transport equation and its near-bed sediment flux

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The suspended sediment transport equation and its near-bed sediment flux are one of the key problems of sediment transport research under nonequilibrium condition. Based on the three-dimensional primitive suspended transport equation, the two-dimensional suspended sediment transport equation is deduced. The derived process indicates that the physical essence of the near-bed sediment flux is right the bottom boundary condition for the suspended sediment transport equation. This paper analyzes the internal relations between the two methods of sediment carrying capacity and shear stress in common use, points out the consistency of these two methods in terms of form and physical meaning, and unifies these two methods theoretically. Furthermore, based on the analysis and comparison of the expressions of the near-bed sediment flux, this paper summarizes some problems to which attention should be paid, thus offering a novel approach to the study and the solution of the problems of suspended sediment transport and exchange flux of near-bed water sediment.

  7. 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

    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...

  8. The suspended sediment transport equation and its near-bed sediment flux

    Institute of Scientific and Technical Information of China (English)

    LI RuiJie; LUO Feng; ZHU WenJin

    2009-01-01

    The suspended sediment transport equation and its near-bed sediment flux are one of the key prob-lems of sediment transport research under nonequilibrium condition. Based on the three-dimensional primitive suspended transport equation, the two-dimensional suspended sediment transport equation is deduced. The derived process indicates that the physical essence of the near-bed sediment flux is right the bottom boundary condition for the suspended sediment transport equation. This paper ana-lyzes the internal relations between the two methods of sediment carrying capacity and shear stress in common use, points out the consistency of these two methods in terms of form and physical meaning, and unifies these two methods theoretically. Furthermore, based on the analysis and comparison of the expressions of the near-bed sediment flux, this paper summarizes some problems to which attention should be paid, thus offering a novel approach to the study and the solution of the problems of sus-pended sediment transport and exchange flux of near-bed water sediment.

  9. 用扩散流动模型分析悬浮床内的气固两相向上流动%A Numerical Simulation of Gas-Particle Two-Phase Flow in a Suspension Bed Using Diffusion Flux Model

    Institute of Scientific and Technical Information of China (English)

    尚智; 杨瑞昌; FUKUDA Kenji; 钟勇; 巨泽建

    2003-01-01

    A mathematical model of two-dimensional turbulent gas-particle two-phase flow based on the modified diffusion flux model (DFM) and a numerical simulation method to analyze the gas-particle flow structures are developed. The modified diffusion flux model, in which the acceleration due to various forces is taken into account for the calculation of the diffusion velocity of particles, is applicable to the analysis of multi-dimensional gas-particle two-phase turbulent flow. In order to verify its accuracy and efficiency, the numerical simulation by DFM is compared with experimental studies and the prediction by κ-ε-κp two-fluid model, which shows a reasonable agreement. It is confirmed that the modified diffusion flux model is suitable for simulating the multi-dimensional gas-particle two-phase flow.

  10. Quantifying Particle Numbers and Mass Flux in Drifting Snow

    Science.gov (United States)

    Crivelli, Philip; Paterna, Enrico; Horender, Stefan; Lehning, Michael

    2016-12-01

    We compare two of the most common methods of quantifying mass flux, particle numbers and particle-size distribution for drifting snow events, the snow-particle counter (SPC), a laser-diode-based particle detector, and particle tracking velocimetry based on digital shadowgraphic imaging. The two methods were correlated for mass flux and particle number flux. For the SPC measurements, the device was calibrated by the manufacturer beforehand. The shadowgrapic imaging method measures particle size and velocity directly from consecutive images, and before each new test the image pixel length is newly calibrated. A calibration study with artificially scattered sand particles and glass beads provides suitable settings for the shadowgraphical imaging as well as obtaining a first correlation of the two methods in a controlled environment. In addition, using snow collected in trays during snowfall, several experiments were performed to observe drifting snow events in a cold wind tunnel. The results demonstrate a high correlation between the mass flux obtained for the calibration studies (r ≥slant 0.93) and good correlation for the drifting snow experiments (r ≥slant 0.81). The impact of measurement settings is discussed in order to reliably quantify particle numbers and mass flux in drifting snow. The study was designed and performed to optimize the settings of the digital shadowgraphic imaging system for both the acquisition and the processing of particles in a drifting snow event. Our results suggest that these optimal settings can be transferred to different imaging set-ups to investigate sediment transport processes.

  11. Quantifying Particle Numbers and Mass Flux in Drifting Snow

    Science.gov (United States)

    Crivelli, Philip; Paterna, Enrico; Horender, Stefan; Lehning, Michael

    2016-06-01

    We compare two of the most common methods of quantifying mass flux, particle numbers and particle-size distribution for drifting snow events, the snow-particle counter (SPC), a laser-diode-based particle detector, and particle tracking velocimetry based on digital shadowgraphic imaging. The two methods were correlated for mass flux and particle number flux. For the SPC measurements, the device was calibrated by the manufacturer beforehand. The shadowgrapic imaging method measures particle size and velocity directly from consecutive images, and before each new test the image pixel length is newly calibrated. A calibration study with artificially scattered sand particles and glass beads provides suitable settings for the shadowgraphical imaging as well as obtaining a first correlation of the two methods in a controlled environment. In addition, using snow collected in trays during snowfall, several experiments were performed to observe drifting snow events in a cold wind tunnel. The results demonstrate a high correlation between the mass flux obtained for the calibration studies (r ≥slant 0.93 ) and good correlation for the drifting snow experiments (r ≥slant 0.81 ). The impact of measurement settings is discussed in order to reliably quantify particle numbers and mass flux in drifting snow. The study was designed and performed to optimize the settings of the digital shadowgraphic imaging system for both the acquisition and the processing of particles in a drifting snow event. Our results suggest that these optimal settings can be transferred to different imaging set-ups to investigate sediment transport processes.

  12. EXPERIMENTAL STUDY ON THE DYNAMICS OF A SPOUTED BED WITH PARTICLE FEED THROUGH THE BASE

    Directory of Open Access Journals (Sweden)

    Freitas L.A.P.

    1997-01-01

    Full Text Available A draft tube spouted bed was constructed with a screw conveyor attached at its base to feed particles into the column. Results on fluid dynamic characteristics and particle movement in this system are presented and discussed. Two methods of measuring the superficial air velocity in the annular region are compared. The particle velocity and recirculation rates have been determined in a half column with transparent walls. The effects of the particle feed rate, air flow rate and bed height on the spouted bed dynamics have been analysed and compared with those in the literature. Keywords: Spouted bed, continuous feed, dynamics

  13. Entrainment, motion, and deposition of coarse particles transported by water over a sloping mobile bed

    Science.gov (United States)

    Heyman, J.; Bohorquez, P.; Ancey, C.

    2016-10-01

    In gravel bed rivers, bed load transport exhibits considerable variability in time and space. Recently, stochastic bed load transport theories have been developed to address the mechanisms and effects of bed load transport fluctuations. Stochastic models involve parameters such as particle diffusivity, entrainment, and deposition rates. The lack of hard information on how these parameters vary with flow conditions is a clear impediment to their application to real-world scenarios. In this paper, we determined the closure equations for the above parameters from laboratory experiments. We focused on shallow supercritical flow on a sloping mobile bed in straight channels, a setting that was representative of flow conditions in mountain rivers. Experiments were run at low sediment transport rates under steady nonuniform flow conditions (i.e., the water discharge was kept constant, but bed forms developed and migrated upstream, making flow nonuniform). Using image processing, we reconstructed particle paths to deduce the particle velocity and its probability distribution, particle diffusivity, and rates of deposition and entrainment. We found that on average, particle acceleration, velocity, and deposition rate were responsive to local flow conditions, whereas entrainment rate depended strongly on local bed activity. Particle diffusivity varied linearly with the depth-averaged flow velocity. The empirical probability distribution of particle velocity was well approximated by a Gaussian distribution when all particle positions were considered together. In contrast, the particles located in close vicinity to the bed had exponentially distributed velocities. Our experimental results provide closure equations for stochastic or deterministic bed load transport models.

  14. The preferential erosion and deposition of heavy particles over erodible beds

    Science.gov (United States)

    Salesky, Scott; Giometto, Marco; Lehning, Michael; Parlange, Marc

    2016-11-01

    The erosion, transport, and deposition of heavy particles over erodible beds by turbulent flow is a significant process in the context of sediment transport, aeolian processes, and snow transport in alpine and polar regions. While it is well-known that terrain features can lead to spatially inhomogeneous deposition velocities, a systematic study considering the effects of terrain and particle properties has not been conducted to date using large eddy simulation (LES). Using a recently developed Eulerian finite-volume model for the transport of heavy particles over complex terrain in LES, we perform simulations of the transport, erosion, and deposition of heavy particles over idealized surface topography. A new model for particle ejection in the saltation layer subject to the constraints of energy and momentum conservation is adapted for use in an Eulerian framework. A suite of simulations is conducted in order to explore the governing parameters relevant for erosion and deposition (e.g. Stokes number, Rouse number, Shields number, surface cohesion) and to investigate the influence of the mean flow vs. turbulent fluxes for the observed erosion and deposition patterns. Implications for model development will be highlighted, and numerical considerations will be discussed.

  15. Fluidized-bed reactor model with generalized particle balances. Part 1. Formulation and solution

    Energy Technology Data Exchange (ETDEWEB)

    Overturf, B.W.; Reklaitis, G.V.

    1983-09-01

    In this first part, a particle balance model is developed for a fluidized-bed gas-solid reactor which accommodates particle distributions dependent on both size and density, as well as populations consisting of multiple solids.

  16. Online monitoring of particle mass flow rate in bottom spray fluid bed coating--development and application.

    Science.gov (United States)

    Wang, Li Kun; Heng, Paul Wan Sia; Liew, Celine Valeria

    2010-08-16

    The primary purpose of this study is to develop a visiometric process analyzer for online monitoring of particle mass flow rate in the bottom spray fluid bed coating process. The secondary purpose is to investigate the influences of partition gap and air accelerator insert size on particle mass flow rate using the developed visiometric process analyzer. Particle movement in the region between the product chamber and partition column was captured using a high speed camera. Mean particle velocity and number of particles in the images were determined by particle image velocimetry and morphological image processing method respectively. Mass flow rate was calculated using particle velocity, number of particles in the images, particle density and size information. Particle velocity and number findings were validated using image tracking and manual particle counting techniques respectively. Validation experiments showed that the proposed method was accurate. Partition gap was found to influence particle mass flow rate by limiting the rate of solids flux into the partition column; the air accelerator insert was found to influence particle mass flow rate by a Venturi effect. Partition gap and air accelerator insert diameter needed to be adjusted accordingly in relation to the other variability sources and diameter of coating cores respectively. The potential, challenges and possible solutions of the proposed visiometric process analyzer were further discussed. Copyright (c) 2010 Elsevier B.V. All rights reserved.

  17. Clustering behavior of solid particles in two-dimensional liquid-solid fluidized-beds

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    In this paper, the clustering behavior of solid particles in a two-dimensional (2D) liquid-solid fluidized-bed was studied by using the charge coupled devices (CCD) imaging measuring and processing technique and was characterized by fractal analysis. CCD images show that the distribution of solid particles in the 2D liquid-solid fluidised-bed is not uniform and self-organization behavior of solid particles was observed under the present experimental conditions. The solid particles move up in the 2D fluidized-bed in groups or clusters whose configurations are often in the form of horizontal strands. The box fractal dimension of the cluster images in the 2D liquid-solid fluidized-bed increases with the rising of solid holdup and reduces with the increment of solid particle diameter and superficial liquid velocity. At given solid holdup and solid particle size,the lighter particles show smaller fractal dimensions.

  18. Pebble bed reactor fuel cycle optimization using particle swarm algorithm

    Energy Technology Data Exchange (ETDEWEB)

    Tavron, Barak, E-mail: btavron@bgu.ac.il [Planning, Development and Technology Division, Israel Electric Corporation Ltd., P.O. Box 10, Haifa 31000 (Israel); Shwageraus, Eugene, E-mail: es607@cam.ac.uk [Department of Engineering, University of Cambridge, Trumpington Street, Cambridge CB2 1PZ (United Kingdom)

    2016-10-15

    Highlights: • Particle swarm method has been developed for fuel cycle optimization of PBR reactor. • Results show uranium utilization low sensitivity to fuel and core design parameters. • Multi-zone fuel loading pattern leads to a small improvement in uranium utilization. • Thorium mixes with highly enriched uranium yields the best uranium utilization. - Abstract: Pebble bed reactors (PBR) features, such as robust thermo-mechanical fuel design and on-line continuous fueling, facilitate wide range of fuel cycle alternatives. A range off fuel pebble types, containing different amounts of fertile or fissile fuel material, may be loaded into the reactor core. Several fuel loading zones may be used since radial mixing of the pebbles was shown to be limited. This radial separation suggests the possibility to implement the “seed-blanket” concept for the utilization of fertile fuels such as thorium, and for enhancing reactor fuel utilization. In this study, the particle-swarm meta-heuristic evolutionary optimization method (PSO) has been used to find optimal fuel cycle design which yields the highest natural uranium utilization. The PSO method is known for solving efficiently complex problems with non-linear objective function, continuous or discrete parameters and complex constrains. The VSOP system of codes has been used for PBR fuel utilization calculations and MATLAB script has been used to implement the PSO algorithm. Optimization of PBR natural uranium utilization (NUU) has been carried out for 3000 MWth High Temperature Reactor design (HTR) operating on the Once Trough Then Out (OTTO) fuel management scheme, and for 400 MWth Pebble Bed Modular Reactor (PBMR) operating on the multi-pass (MEDUL) fuel management scheme. Results showed only a modest improvement in the NUU (<5%) over reference designs. Investigation of thorium fuel cases showed that the use of HEU in combination with thorium results in the most favorable reactor performance in terms of

  19. Riser simulation and radial porosity distribution characterization for gas-fluidized bed of cork particles

    Science.gov (United States)

    Wu, Guorong; Ouyang, Jie; Li, Qiang

    2014-08-01

    Numerical simulations are carried out for gas-solid fluidized bed of cork particles, using discrete element method. Results exhibit the existence of a so-called anti core-annular porosity profile with lower porosity in the core and higher porosity near the wall for non-slugging fluidization. The tendency to form this unfamiliar anti core-annular porosity profile is stronger when the solid flux is higher. There exist multiple inflection points in the simulated axial solid volume fraction profile for non-slugging fluidization. Results also show that the familiar core-annular porosity profile still appears for slugging fluidization. In addition, the classical choking phenomenon can be captured at the superficial gas velocity slightly lower than the correlated transport velocity.

  20. Mass transfer from the wall of a column to the fluid in a fluidized bed of inert spherical particles

    Directory of Open Access Journals (Sweden)

    Brzić Danica V.

    2004-01-01

    Full Text Available Mass transfer in fluidized beds is an important operation for separation processes. Two effects can be achieved by using fluidized beds in mass transfer processes increasing interface area and relative movement between the phases. These effects are both desirable because they lead to greater process rates. This paper presents an experimental investigation regarding mass transfer from the wall of a column to the fluid in a fluidized bed of inert spherical particles. The experiments were conducted in column 40 mm in diameter with spherical particles 0,8-3 mm in diameter and water as one fluidizing fluid. The method of dissolution of benzoic acid was used to provide very low mass flux. The average wall-to-fluid mass transfer coefficients were determined for two systems: single-phase fluid flow and a fluidized bed of inert particles The measurements encompassed a Reynolds number range from 100-4000 for single-phase flow and 600-4000 in fluidized beds. The mass transfer coefficients for both systems were calculated from weight loss of benzoic acid. The effects of superficial liquid velocity and particle diameter on the mass transfer coefficient were investigated. It was found that mass transfer was more intensive in the fluidized bed in comparison with single phase flow. The best conditions for mass transfer were reached at a minimum fluidization velocity, when the mass transfer coefficient had the greatest value. The experimental data were correlated in the form: jd = f(Re, where jd is the dimensionless mass transfer factor and Re the Reynolds number.

  1. Increased particle flux to the deep ocean related to monsoons

    Digital Repository Service at National Institute of Oceanography (India)

    Nair, R.R.; Ittekkot, V.; Manganini, S.J.; Ramaswamy, V.; Haake, B.; Degens, E.T.; Desai, B.N.; Honjo, S.

    . To assess the impact of monsoon-driven processes on the downward particle flux variations in the open ocean we deployed three moored arrays consisting of six time-series sediment traps at selected locations in the western, central and eastern parts...

  2. Plasma–Surface Interactions Under High Heat and Particle Fluxes

    Directory of Open Access Journals (Sweden)

    Gregory De Temmerman

    2013-01-01

    Full Text Available The plasma-surface interactions expected in the divertor of a future fusion reactor are characterized by extreme heat and particle fluxes interacting with the plasma-facing surfaces. Powerful linear plasma generators are used to reproduce the expected plasma conditions and allow plasma-surface interactions studies under those very harsh conditions. While the ion energies on the divertor surfaces of a fusion device are comparable to those used in various plasma-assited deposition and etching techniques, the ion (and energy fluxes are up to four orders of magnitude higher. This large upscale in particle flux maintains the surface under highly non-equilibrium conditions and bring new effects to light, some of which will be described in this paper.

  3. Stress analysis of an agitated particle bed with different particle aspect ratios by the discrete element method

    Directory of Open Access Journals (Sweden)

    Goh Wei Pin

    2017-01-01

    Full Text Available The size distribution, shape and aspect ratio of particles are the common factors that affect their packing in a particle bed. Agitated powder beds are commonly used in the process industry for various applications. The stresses arising as a result of shearing the bed could result in undesirable particle breakage with adverse impact on manufacturability. We report on our work on analysing the stress distribution within an agitated particle bed with several particle aspect ratios by the Discrete Element Method (DEM. Rounded cylinders with different aspect ratios are generated and incorporated into the DEM simulation. The void fraction of the packing of the static and agitated beds with different particle aspect ratios is analysed. Principal and deviatoric stresses are quantified in the regions of interest along the agitating impeller blade for different cases of particle aspect ratios. The relationship between the particle aspect ratio and the stress distribution of the bed over the regions of interest is then established and will be presented.

  4. Experimental investigations on the coolability of prototypical particle beds with respect to reactor safety; Experimentelle Untersuchungen der Kuehlbarkeit prototypischer Schuettungskonfigurationen unter dem Aspekt der Reaktorsicherheit

    Energy Technology Data Exchange (ETDEWEB)

    Leininger, Simon

    2017-02-22

    In case of a severe accident in a light water reactor, continuous unavailability of cooling water to the reactor core may result in overheating of the fuel elements and finally the loss of core integrity. Under such conditions, a structure of heat-releasing particles of different size and shape may be formed by fragmentation of molten core material in several stages of the accident. The long-term coolability of such beds is of prime im-portance to avoid any damage to the reactor pressure vessel or even a release of fission products to the environment. In the frame of this work, specific experiments were con-ducted under prototypical conditions employing the existing DEBRIS test facility in order to gain further knowledge about the thermohydraulic behavior of such beds. In steady state boiling experiments, the pressure gradients in particle beds were meas-ured both for one- and multi-dimensional cooling water flow conditions and compared with one another in order to assess the flow behavior inside the bed. For these different flow conditions as well as for stratified bed configurations, the maximum removable heat flux densities were determined in the dryout experiments. E. g., it was found that an axial stratification of the permeability can significantly reduce the bed's coolability. For the first time, the quenching behavior of dry, superheated beds was investigated at elevated system pressure up to 0.5 MPa. In these experiments, the effect of system pressure on the coolability was quantified by means of the quenching time (time period to cool down the bed to saturation temperature). The investigated particle beds mainly consisted of non-spherical particles with well-defined geometry (cylinders and screws). It was shown that the effect of the particles geometry on the flow in a particle bed can be best estimated by using an equivalent particle diameter calculated for monodisperse particle beds from the product of the Sauter diameter and a shape factor and for

  5. Propagation of a Strong Shock Over a Random Bed of Spherical Particles

    Energy Technology Data Exchange (ETDEWEB)

    Mehta, Y. [Univ. of Florida, Gainesville, FL (United States); Neal, C. [Univ. of Florida, Gainesville, FL (United States); Salari, K. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Jackson, T. L. [Univ. of Florida, Gainesville, FL (United States); Balachandar, S. [Univ. of Florida, Gainesville, FL (United States); Thakur, S. [Univ. of Florida, Gainesville, FL (United States)

    2017-04-11

    Propagation of a strong shock through a bed of particles results in complex wave dynamics such as a reflected shock, a transmitted shock, and highly unsteady flow inside the particle bed. In this paper we present three-dimensional numerical simulations of shock propagation in air over a random bed of particles. We assume the flow is inviscid and governed by the Euler equations of gas dynamics. Simulations are carried out by varying the volume fraction of the particle bed at a fixed shock Mach number. We compute the unsteady inviscid streamwise and transverse drag coefficients as a function of time for each particle in the random bed as a function of volume fraction. We show that (i) there are significant variations in the peak drag for the particles in the bed, (ii) the mean peak drag as a function of streamwise distance through the bed decreases with a slope that increases as the volume fraction increases, and (iii) the deviation from the mean peak drag does not correlate with local volume fraction. We also present the local Mach number and pressure contours for the different volume fractions to explain the various observed complex physical mechanisms occurring during the shock-particle interactions. Since the shock interaction with the random bed of particles leads to transmitted and reflected waves, we compute the average flow properties to characterize the strength of the transmitted and reflected shock waves and quantify the energy dissipation inside the particle bed. Finally, to better understand the complex wave dynamics in a random bed, we consider a simpler approximation of a planar shock propagating in a duct with a sudden area change. We obtain Riemann solutions to this problem, which are used to compare with fully resolved numerical simulations.

  6. A New Method for Tracking Individual Particles During Bed Load Transport in a Gravel-Bed River

    Science.gov (United States)

    Tremblay, M.; Marquis, G. A.; Roy, A. G.; Chaire de Recherche Du Canada En Dynamique Fluviale

    2010-12-01

    Many particle tracers (passive or active) have been developed to study gravel movement in rivers. It remains difficult, however, to document resting and moving periods and to know how particles travel from one deposition site to another. Our new tracking method uses the Hobo Pendant G acceleration Data Logger to quantitatively describe the motion of individual particles from the initiation of movement, through the displacement and to the rest, in a natural gravel river. The Hobo measures the acceleration in three dimensions at a chosen temporal frequency. The Hobo was inserted into 11 artificial rocks. The rocks were seeded in Ruisseau Béard, a small gravel-bed river in the Yamaska drainage basin (Québec) where the hydraulics, particle sizes and bed characteristics are well known. The signals recorded during eight floods (Summer and Fall 2008-2009) allowed us to develop an algorithm which classifies the periods of rest and motion. We can differentiate two types of motion: sliding and rolling. The particles can also vibrate while remaining in the same position. The examination of the movement and vibration periods with respect to the hydraulic conditions (discharge, shear stress, stream power) showed that vibration occurred mostly before the rise of hydrograph and allowed us to establish movement threshold and response times. In all cases, particle movements occurred during floods but not always in direct response to increased bed shear stress and stream power. This method offers great potential to track individual particles and to establish a spatiotemporal sequence of the intermittent transport of the particle during a flood and to test theories concerning the resting periods of particles on a gravel bed.

  7. Dynamics of bed load particles in supercritical flows close to the onset of motion

    CERN Document Server

    Heyman, J; Ancey, C

    2016-01-01

    The fair understanding of bed load dynamics in established transport conditions contrasts with the relatively poor knowledge and the rich variety of phenomena occurring close to the initiation of transport. Steep streams are also known to resist most of the existing predictive theories. In order to gain knowledge of the principal mechanisms involved in such transport cases, it seems necessary to refine our vision of the transport process down to the individual grain dynamics. Here, we present 10 experiments carried out in a steep, shallow water flume made of an erodible bed of natural, uniform gravel at low transport conditions. We simultaneously recorded bed load particle motions and bed and water elevations using two high-speed cameras. 8~km of particle trajectories were reconstructed with the help of a robust and original tracking algorithm. We propose a statistical analysis of this data in order to estimate how dependent particle velocity, particle acceleration, particle diffusivity, particle entrainment,...

  8. An analysis of the chaotic motion of particles of different sizes in a gas fluidized bed

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The dynamic behavior of individual particles during the mixing/segregation process of particle mixtures in a gas fluidized bed is analyzed. The analysis is based on the results generated from discrete particle simulation, with the focus on the trajectory of and forces acting on individual particles.Typical particles are selected representing three kinds of particle motion:a flotsam particle which is initially at the bottom part of the bed and finally fluidized at the top part of the bed; a jetsam particle which is initially at the top part of the bed and finally stays in the bottom de-fluidized layer of the bed; and a jetsam particle which is intermittently joining the top fluidized and bottom de-fluidized layers. The results show that the motion of a particle is chaotic at macroscopic or global scale, but can be well explained at a microscopic scale in terms of its interaction forces and contact conditions with other particles, particle-fluid interaction force, and local flow structure. They also highlight the need for establishing a suitable method to link the information generated and modeled at different time and length scales.

  9. PARTICLE COATING BY CHEMICAL VAPOR DEPOSITION IN A FLUIDI7ED BED REACTOR

    Institute of Scientific and Technical Information of China (English)

    Gregor; Czok; Joachim; Werther

    2005-01-01

    Aluminum coatings were created onto glass beads by chemical vapor deposition in a fluidized bed reactor at different temperatures. Nitrogen was enriched with Triisobutylaluminum (TIBA) vapor and the latter was thermally decomposed inside the fluidized bed to deposit the elemental aluminum. To ensure homogeneous coating on the bed material, the fluidizing conditions necessary to avoid agglomeration were investigated for a broad range of temperatures.The deposition reaction was modeled on the basis of a discrete particle simulation to gain insight into homogeneity and thickness of the coating throughout the bed material. In particular, the take-up of aluminum was traced for selected particles that exhibited a large mass of deposited aluminum.

  10. Positron emission tomography in pebble beds. Part 1: Liquid particle deposition

    Energy Technology Data Exchange (ETDEWEB)

    Barth, T., E-mail: t.barth@hzdr.de [Helmholtz-Zentrum Dresden-Rossendorf, Institute of Fluid Dynamics (IFD), Bautzner Landstraße 400, 01328 Dresden (Germany); Ludwig, M. [Helmholtz-Zentrum Dresden-Rossendorf, Institute of Fluid Dynamics (IFD), Bautzner Landstraße 400, 01328 Dresden (Germany); Kulenkampff, J.; Gründig, M. [Helmholtz-Zentrum Dresden-Rossendorf, Institute of Resource Ecology (IRE), Permoserstraße 15, 04318 Leipzig (Germany); Franke, K. [Helmholtz-Zentrum Dresden-Rossendorf, Institute of Resource Ecology (IRE), Permoserstraße 15, 04318 Leipzig (Germany); Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmacy (IRP), Permoserstraße 15, 04318 Leipzig (Germany); Lippmann-Pipke, J. [Helmholtz-Zentrum Dresden-Rossendorf, Institute of Resource Ecology (IRE), Permoserstraße 15, 04318 Leipzig (Germany); Hampel, U. [Helmholtz-Zentrum Dresden-Rossendorf, Institute of Fluid Dynamics (IFD), Bautzner Landstraße 400, 01328 Dresden (Germany); Helmholtz-Zentrum Dresden-Rossendorf, AREVA Endowed Chair of Imaging Techniques in Energy and Process Engineering, Technische Universität Dresden, 01062 Dresden (Germany)

    2014-02-15

    Highlights: • Particle deposition in a pebble bed was recorded by positron emission tomography. • The particles were radioactively labelled and their spatial distribution was recorded. • Particle deposition was mainly driven by particle inertia and turbulent dispersion. • Particle deposits form hot spots on the upstream face of the single pebbles. - Abstract: Accidental scenarios such as the depressurisation of the primary circuit of high temperature gas cooled pebble bed reactors may lead to the release of fission products via the discharge of radioactive graphite dust. For a detailed source term assessment in such accident scenarios knowledge of the flow mechanics of dust transport in complex coolant circuit components, like pebble beds, recuperator structures and pipe systems is necessary. In this article an experimental study of aerosol deposition in a pebble bed is described. We investigated the deposition of radiolabelled liquid aerosol particles in a scaled pebble bed in an air-driven small-scale aerosol flow test facility under isothermal ambient conditions. The aerosol particles were generated by means of a condensational aerosol generator with potassium-fluoride (KF) condensation nuclei. Particle concentration measurements upstream and downstream of the pebble bed were performed by isokinetic sampling and particle counting. The results agree with typical deposition curves for turbulent and inertia driven particle deposition. Furthermore, positron emission tomography (PET) was performed to visualize and measure particle deposition distributions in the pebble bed. Results of a selected deposition experiment with moderately large particles (d{sub aero} = 3.5 μm, Re{sup ′}{sub pb}=2200) show that the deposited particles are located in the vicinity of the upstream stagnation points of the pebbles. These findings support the thesis that inertia driven particle deposition is predominating.

  11. The influence of fine char particles burnout on bed agglomeration during the fluidized bed combustion of a biomass fuel

    Energy Technology Data Exchange (ETDEWEB)

    Scala, Fabrizio; Chirone, Riccardo [Istituto di Ricerche sulla Combustione, CNR, P.le V. Tecchio, 80-80125 Naples (Italy); Salatino, Piero [Dipartimento di Ingegneria Chimica, Universita degli Studi di Napoli Federico II, P.le V. Tecchio, 80-80125 Naples (Italy)

    2003-11-15

    The combustion of biomass char in a bubbling fluidized bed is hereby addressed, with specific reference to the influence that the combustion of fine char particles may exert on ash deposition and bed agglomeration phenomena. Experiments of steady fluidized bed combustion (FBC) of powdered biomass were carried out with the aim of mimicking the postcombustion of attrited char fines generated in the fluidized bed combustion of coarse char. Experimental results showed that the char elutriation rate is much smaller than expected on the basis of the average size of the biomass powder and of the carbon loading in the combustor. Samples of bed material collected after prolonged operation of the combustor were characterized by scanning electron microscopy (SEM)-EDX analysis and revealed the formation of relatively coarse sand-ash-carbon aggregates. The phenomenology is consistent with the establishment of a char phase attached to the bed material as a consequence of adhesion of char fines onto the sand particles. Combustion under sound-assisted fluidization conditions was also tested. As expected, enhancement of fines adhesion on bed material and further reduction of the elutriation rate were observed. Experimental results are interpreted in the light of a simple model which accounts for elutriation of free fines, adhesion of free fines onto bed material and detachment of attached fines by attrition of char-sand aggregates. Combustion of both free and attached char fines is considered. The parameters of the model are assessed on the basis of the measured carbon loadings and elutriation rates. Model computations are directed to estimate the effective size and the peak temperature of char-sand aggregates. The theoretical estimates of the effective aggregate size match fairly well those observed in the experiments.

  12. Friction factor for water flow through packed beds of spherical and non-spherical particles

    Directory of Open Access Journals (Sweden)

    Kaluđerović-Radoičić Tatjana

    2017-01-01

    Full Text Available The aim of this work was the experimental evaluation of different friction factor correlations for water flow through packed beds of spherical and non-spherical particles at ambient temperature. The experiments were performed by measuring the pressure drop across the bed. Packed beds made of monosized glass spherical particles of seven different diameters were used, as well as beds made of 16 fractions of quartz filtration sand obtained by sieving (polydisperse non-spherical particles. The range of bed voidages was 0.359–0.486, while the range of bed particle Reynolds numbers was from 0.3 to 286 for spherical particles and from 0.1 to 50 for non-spherical particles. The obtained results were compared using a number of available literature correlations. In order to improve the correlation results for spherical particles, a new simple equation was proposed in the form of Ergun’s equation, with modified coefficients. The new correlation had a mean absolute deviation between experimental and calculated values of pressure drop of 9.04%. For non-spherical quartz filtration sand particles the best fit was obtained using Ergun’s equation, with a mean absolute deviation of 10.36%. Surface-volume diameter (dSV necessary for correlating the data for filtration sand particles was calculated based on correlations for dV = f(dm and Ψ = f(dm. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. ON172022

  13. Influence of particle flux on morphology changes of tungsten

    Energy Technology Data Exchange (ETDEWEB)

    Buzi, Luxherta; Schweer, Bernd; Terra, Alexis; Unterberg, Bernhard [Institut fuer Energie- und Klimaforschung - Plasmaphysik, Forschungszentrum Juelich GmbH, Association EURATOM-FZJ, Juelich (Germany); Temmerman, Greg de [FOM-DIFFER, Association EURATOM-FOM, Nieuwegein (Netherlands); Oost, Guido van [Department of Applied Physics, Ghent University (Belgium)

    2013-07-01

    Tungsten is currently considered as the main candidate material for high heat flux components of future fusion devices. Bombardment of tungsten surfaces by large fluences of low energy particles such as hydrogen isotopes and helium can lead to strong microstructural changes which are mechanically unstable. The occurrence of those effects is strongly dependent on the surface temperature and particle flux. In this contribution we present the experiments done at PSI-2 linear plasma device in order to generate surface modifications on tungsten. The power flux density delivered to the target at PSI-2 is up to 2 MWm{sup -2} and the ion flux density is of the order of 10{sup 22}-10{sup 23} m{sup -2}s{sup -1}. A dedicated actively heated sample holder was designed and tested in order to provide the required temperature range from 300 K to 1800 K. We present here the first measurements performed at PSI-2 whereas subsequent experiments are foreseen at Pilot-PSI and MAGNUM-PSI linear plasma devices with higher flux densities up to 10{sup 25} m{sup -2}s{sup -1}.

  14. Effect of particle distribution on the compaction behavior of granular beds

    Science.gov (United States)

    Lowe, C. A.; Longbottom, A. W.

    2006-06-01

    This research determines how particle size and particle distribution affects the compaction of granular beds. A modelling and experimental effort was recently designed to compare the compaction behavior of two types of granular HMX: prepressed conventional (coarse) HMX material (mean diameter of 40μm) and microfine HMX (mean diameter Journal of Applied Physics 97, 093521 (2005)]. The microfine material demonstrated higher levels of granular bed strength. Mesoscale modelling of granular beds that are of fixed initial solid volume fraction but vary in particle size and distribution have been undertaken that include a simple elastic-plastic strength model. These suggest that it is not inherently the "size" of a particle that controls the bed strength but the morphology and distribution of particle grains. These solutions are compared with the behavior predicted from continuum scale models of material compaction.

  15. A RELATION FOR THE VOID FRACTION OF RANDOMLY PACKED PARTICLE BEDS

    NARCIS (Netherlands)

    HOFFMANN, AC; FINKERS, HJ

    1995-01-01

    The void fractions of loosely packed and tapped beds of particles of continuous size distributions are correlated by means of a proposed new semi-empirical relation. In this relation four parameters describing the following particle properties are included: (i) mean particle size, (ii) spread of the

  16. Investigation of Gas Solid Fluidized Bed Dynamics with Non-Spherical Particles

    Energy Technology Data Exchange (ETDEWEB)

    Choudhuri, Ahsan

    2013-06-30

    One of the largest challenges for 21st century is to fulfill global energy demand while also reducing detrimental impacts of energy generation and use on the environment. Gasification is a promising technology to meet the requirement of reduced emissions without compromising performance. Coal gasification is not an incinerating process; rather than burning coal completely a partial combustion takes place in the presence of steam and limited amounts of oxygen. In this controlled environment, a chemical reaction takes place to produce a mixture of clean synthetic gas. Gas-solid fluidized bed is one such type of gasification technology. During gasification, the mixing behavior of solid (coal) and gas and their flow patterns can be very complicated to understand. Many attempts have taken place in laboratory scale to understand bed hydrodynamics with spherical particles though in actual applications with coal, the particles are non-spherical. This issue drove the documented attempt presented here to investigate fluidized bed behavior using different ranges of non-spherical particles, as well as spherical. For this investigation, various parameters are controlled that included particle size, bed height, bed diameter and particle shape. Particles ranged from 355 µm to 1180 µm, bed diameter varied from 2 cm to 7 cm, two fluidized beds with diameters of 3.4 cm and 12.4 cm, for the spherical and non-spherical shaped particles that were taken into consideration. Pressure drop was measured with increasing superficial gas velocity. The velocity required in order to start to fluidize the particle is called the minimum fluidization velocity, which is one of the most important parameters to design and optimize within a gas-solid fluidized bed. This minimum fluidization velocity was monitored during investigation while observing variables factors and their effect on this velocity. From our investigation, it has been found that minimum fluidization velocity is independent of bed

  17. SIMULATION OF PARTICLE COATING IN THE SUPERCRITICAL FLUIDIZED BED

    Institute of Scientific and Technical Information of China (English)

    Carsten; Vogt; Ernst-Ulrich; Hartge; Joachim; Werther; Gerd; Brunner

    2005-01-01

    Fluidized bed technology using supercritical carbon dioxide both as a fluidizing gas and as a solvent for the coating material makes possible the production of thin, uniform and solvent-free coatings. But operation at low fluidizing velocities, which is favorable to facilitate gas cleaning under the high pressure conditions, may lead to uneven distribution of the coating in the fluidized bed and to unstable operation due to agglomeration. Therefore a model has been developed which describes local fluid dynamics within the high pressure fluidized bed. Based on this model, the coating process is described and the distribution of the coating inside the fluidized bed is calculated. Furthermore a submodel for the calculation of local concentrations of liquid paraffin has been set up, which may be used as a basis for the prediction of agglomeration and thus stability of operation.

  18. NUMERICAL PREDICTION OF PARTICLE MIXING BEHAVIOR IN A BUBBLING FLUIDIZED BED

    Institute of Scientific and Technical Information of China (English)

    WU Chun-liang; ZHAN Jie-min

    2007-01-01

    In this article the hard-sphere Discrete Particle Model (DPM) is used to study the mixing behavior of particles in the 2-D fluidized bed. Different flow patterns in the bed for two kinds of inlet configurations, namely free bubbling and jet bubbling mode, are captured by the numerical model, under specific superficial gas velocities. To examine the degree of particle mixing, the Fan index is applied. The numerical results show that the rate of particle mixing is larger in the jet bubbling than that in the free bubbling mode. The gross circulations of particles in the jet bubbling bed give a higher degree of mixing because of the involvement of a greater number of particles.

  19. Investigation on Horizontal Mixing of Particles in Dense Bed in Circulating Fluidized Bed(CFB)

    Institute of Scientific and Technical Information of China (English)

    XiaoPing; YanGuizhang; 等

    1998-01-01

    A two dimensional cold CFB test rig has been established.investigation on horizontal mixing of particles in dense bed has been caried out on this test rig.Miaing model has been used in data reduction,the horizontal mixing coefficients of particles in different experimental conditions and in different structures of dense bed have been obtained and compared.By using dimensional analysis,non-dimensional expression of experimental condition and mixing coefficient have been obtained.

  20. Analysis of sand particles' lift-off and incident velocities in wind-blown sand flux

    Institute of Scientific and Technical Information of China (English)

    Tian-Li Bo; Xiao-Jing Zheng; Shao-Zhen Duan; Yi-Rui Liang

    2013-01-01

    In the research of windblown sand movement,the lift-off and incident velocities of saltating sand particles play a significant role in bridging the spatial and temporal scales from single sand particle's motion to windblown sand flux.In this paper,we achieved wind tunnel measurements of the movement of sand particles near sand bed through improving the wind tunnel experimental scheme of paticle image velocimetry (PIV) and data processing method.And then the influence of observation height on the probability distributions of lift-off and incident velocities of sand particles was analyzed.The results demonstrate that the observation height has no obvious influence on the distribution pattern of the lift-off and incident velocities of sand particles,i.e.,the probability distribution of horizontal and vertical velocities of lift-off and incident sand particles follow a Gaussian distribution and a negative exponential distribution,respectively.However,it influences the center of the Gaussian distribution,the decay constant and the amplitude of the negative exponential distribution.

  1. Coupling fine particle and bedload transport in gravel-bedded streams

    Science.gov (United States)

    Park, Jungsu; Hunt, James R.

    2017-09-01

    Fine particles in the silt- and clay-size range are important determinants of surface water quality. Since fine particle loading rates are not unique functions of stream discharge this limits the utility of the available models for water quality assessment. Data from 38 minimally developed watersheds within the United States Geological Survey stream gauging network in California, USA reveal three lines of evidence that fine particle release is coupled with bedload transport. First, there is a transition in fine particle loading rate as a function of discharge for gravel-bedded sediments that does not appear when the sediment bed is composed of sand, cobbles, boulders, or bedrock. Second, the discharge at the transition in the loading rate is correlated with the initiation of gravel mobilization. Third, high frequency particle concentration and discharge data are dominated by clockwise hysteresis where rising limb discharges generally have higher concentrations than falling limb discharges. These three observations across multiple watersheds lead to a conceptual model that fine particles accumulate within the sediment bed at discharges less than the transition and then the gravel bed fluidizes with fine particle release at discharges above the transition discharge. While these observations were individually recognized in the literature, this analysis provides a consistent conceptual model based on the coupling of fine particle dynamics with filtration at low discharges and gravel bed fluidization at higher discharges.

  2. Simple stochastic cellular automaton model for starved beds and implications about formation of sand topographic features in terms of sand flux

    Science.gov (United States)

    Endo, Noritaka

    2016-12-01

    A simple stochastic cellular automaton model is proposed for simulating bedload transport, especially for cases with a low transport rate and where available sediments are very sparse on substrates in a subaqueous system. Numerical simulations show that the bed type changes from sheet flow through sand patches to ripples as the amount of sand increases; this is consistent with observations in flume experiments and in the field. Without changes in external conditions, the sand flux calculated for a given amount of sand decreases over time as bedforms develop from a flat bed. This appears to be inconsistent with the general understanding that sand flux remains unchanged under the constant-fluid condition, but it is consistent with the previous experimental data. For areas of low sand abundance, the sand flux versus sand amount (flux-density relation) in the simulation shows a single peak with an abrupt decrease, followed by a long tail; this is very similar to the flux-density relation seen in automobile traffic flow. This pattern (the relation between segments of the curve and the corresponding bed states) suggests that sand sheets, sand patches, and sand ripples correspond respectively to the free-flow phase, congested phase, and jam phase of traffic flows. This implies that sand topographic features on starved beds are determined by the degree of interference between sand particles. Although the present study deals with simple cases only, this can provide a simplified but effective modeling of the more complicated sediment transport processes controlled by interference due to contact between grains, such as the pulsatory migration of grain-size bimodal mixtures with repetition of clustering and scattering.

  3. Fluidized bed spray granulation: analysis of heat and mass transfers and dynamic particle populations

    Directory of Open Access Journals (Sweden)

    S. Heinrich

    2005-06-01

    Full Text Available A model was developed taking into consideration the heat and mass transfer processes in liquid-sprayed fluidized beds. Such fluidized beds (FB are used for granulation, coating and agglomeration. Conclusions are drawn on the relevance of particle dispersion, spraying and drying to temperature and concentrations distributions. In extension, the model was coupled with a population balance model to describe the particle size distribution and the seeds formation for continuous external FBSG (fluidized bed spray granulation with non-classifying product discharge and a screening and milling unit in the seeds recycle. The effects of seeds formation on the stability of the process is discussed.

  4. The Influence of an Acoustic Field on the Bed Expansion of Fine Particles

    Institute of Scientific and Technical Information of China (English)

    Akash M. Langde; R.L.Sonolikar

    2011-01-01

    Fine particles are difficult to fluidize due to strong interparticle attraction.An attempt has been made to study the bed expansion of silica gel(dp=25μm) powder in presence of an acoustic field.A 135 mm diameter fluidized bed activated by an acoustic field with sound intensity up to 145 dB and frequency from 90 Hz to 170 Hz was studied.The effects of sound pressure level,sound frequency and particle loading on the bed expansion were investigated.Experimental results showed that,bed expansion was good in presence of acoustic field of particular frequency.In addition,it was observed that in presence of acoustic field the bed collapses slowly.

  5. Sorting it out: bedding particle size and nesting material processing method affect nest complexity.

    Science.gov (United States)

    Robinson-Junker, Amy; Morin, Amelia; Pritchett-Corning, Kathleen; Gaskill, Brianna N

    2017-04-01

    As part of routine husbandry, an increasing number of laboratory mice receive nesting material in addition to standard bedding material in their cages. Nesting material improves health outcomes and physiological performance in mice that receive it. Providing usable nesting material uniformly and efficiently to various strains of mice remains a challenge. The aim of this study was to determine how bedding particle size, method of nesting material delivery, and processing of the nesting material before delivery affected nest building in mice of strong (BALB/cAnNCrl) and weak (C3H/HeNCrl) gathering abilities. Our data suggest that processing nesting material through a grinder in conjunction with bedding material, although convenient for provision of bedding with nesting material 'built-in', negatively affects the integrity of the nesting material and subsequent nest-building outcomes. We also found that C3H mice, previously thought to be poor nest builders, built similarly scored nests to those of BALB/c mice when provided with unprocessed nesting material. This was true even when nesting material was mixed into the bedding substrate. We also observed that when nesting material was mixed into the bedding substrate, mice of both strains would sort their bedding by particle size more often than if it were not mixed in. Our findings support the utility of the practice of distributing nesting material mixed in with bedding substrate, but not that of processing the nesting material with the bedding in order to mix them.

  6. Data assimilation tool to reconstruct particle flux measurements

    Science.gov (United States)

    Bourdarie, Sebastien A.; Maget, Vincent; Lazaro, Didier; Sandberg, Ingmar

    2014-05-01

    In the framework of the EU-FP7 MAARBLE project, the Salammbô code and an ensemble Kalman filter is being used to reproduce the electron radiation belt dynamics during storms: (1) The ONERA data assimilation tool has been improved to ingest count rates instead of flux when the instrument response function is available. As an example, the ESA/SREM radiation monitor has complex response functions (proton and electron events are mixed, and for a given specie the instrument responds to a broad range of energies with different efficiencies) which makes very challenging to get fluxes out of count rates. (2) INTEGRAL/SREM, GIOVE-B/SREM, XMM/ERMD and GOES/SEM data assimilation is performed to reproduce with high fidelity the electron belt dynamics during magnetic storms. (3) Because the outputs of the tool are phase space densities, it is then possible to reconstruct INTEGRAL/SREM and GIOVE-B/SREM fluxes time series. In the present talk, an overview of the data assimilation tool will be given. The advantage of using assimilation tool to reconstruct particle flux measurements will be discussed. MAARBLE has received fundings from the European Community's Seventh Framework Programme (FP7-SPACE-.2010-1, SP1 Cooperation, Collaborative project) under grant agreement n284520. This paper reflects only the authors' views and the European Union is not liable for any use that may be made of the information contained therein.

  7. Characteristics of flow in wet conical spouted beds of unequal-sized spherical Particles

    Directory of Open Access Journals (Sweden)

    M. S. Bacelos

    2008-03-01

    Full Text Available Interparticle forces, developed in wet spouted beds composed of a mixture of spherical particles with different size distributions, intensify particle segregation mechanisms interfering in gas distribution inside the bed and, consequently, in the spouting flow characteristics. Therefore, this paper is aimed at describing the effect of interparticle forces on the air-solid flow distribution in conical spouted beds of unequal-sized particles coated by a thin glycerol film. Experimental results show that both the minimum spouting airflow rate and the minimum spouting pressure drop decrease as the amount of glycerol added to the bed increases. In addition, simulated results of the annular air velocity along the bed height showed that, at the base of the column, the radial component of the inertial force is high enough to break liquid bridges between particles and carry these particles out along the spout. Moreover, as the glycerol concentration increases, the spout diameter increases along the bed height. Such changes in the air-solid flow can maintain the spouting regime for higher glycerol concentrations as shown by experimental data.

  8. Project SOLWIND: Space radiation exposure. [evaluation of particle fluxes

    Science.gov (United States)

    Stassinopoulos, E. G.

    1975-01-01

    A special orbital radiation study was conducted for the SOLWIND project to evaluate mission-encountered energetic particle fluxes. Magnetic field calculations were performed with a current field model, extrapolated to the tentative spacecraft launch epoch with linear time terms. Orbital flux integrations for circular flight paths were performed with the latest proton and electron environment models, using new improved computational methods. Temporal variations in the ambient electron environment are considered and partially accounted for. Estimates of average energetic solar proton fluences are given for a one year mission duration at selected integral energies ranging from E greater than 10 to E greater than 100 MeV; the predicted annual fluence is found to relate to the period of maximum solar activity during the next solar cycle. The results are presented in graphical and tabular form; they are analyzed, explained, and discussed.

  9. DEM simulation of polydisperse systems of particles in a fluidized bed

    Institute of Scientific and Technical Information of China (English)

    Nobuyuki Tagami; Ajit Mujumdar; Masayuki Horio

    2009-01-01

    Numerical simulations based on three-dimensional discrete element model (DEM) are conducted for mono-disperse, binary and ternary systems of particles in a fluidized bed. Fluid drag force acting on each particle depending on its size and relative velocity is assigned. The drag coefficient corresponding to Ergun's correlation is applied to the system of fluidized bed with particle size ratios of 1:1 for the mono-disperse system, 1:1.2, 1:1.4 and 1:2 for the binary system and 1:1.33:2 for the ternary system by keeping total volume and surface area of the particles constant. Results indicated that a reasonable estimation of drag force based on individual particle diameters as compared to that of the mean diameter of the particles is achieved in the fluid cells. The total translational kinetic energy of the particles is found to increase as the particle size ratio increases, suggesting an enhanced momentum transfer in polydisperse particle systems. Systems with wide particle size distribution exhibited higher particle velocities around bubbles, resulting in faster bubble growth and its subsequent rise through the fluidized bed.

  10. Study of the Interaction of Fluxes of Annihilating Particles

    Science.gov (United States)

    Nazarov, A. A.; Feropontova, N. M.

    2015-12-01

    A study of interacting particle fluxes in the form of an infinite linear queueing system with positive and negative requests is presented for different types of such systems. For the first class of systems with exponential service a stationary probability distribution of the number of positive requests in the system has been found. For the second class of systems, for the case of arbitrary service, the study is performed by the method of asymptotic analysis. Asymptotic equivalence of the systems under consideration is demonstrated.

  11. A MODEL FOR FINE PARTICLE AGGLOMERATION IN CIRCULATING FLUIDIZED BED ABSORBERS

    Science.gov (United States)

    A model for fine particle agglomeration in circulating fluidized bed absorbers (CFBAS) has been developed. It can model the influence of different factors on agglomeration, such as the geometry of CFBAs, superficial gas velocity, initial particle size distribution, and type of ag...

  12. The influence of particle residence time distribution on the reactivity in fluidized bed reactors

    NARCIS (Netherlands)

    Heesink, A.B.M.; Klaus, J.; Swaaij, van W.P.M.

    1994-01-01

    The influence of particle residence time distribution on the average conversion rate (or reactivity) of particles undergoing a non-catalytic gas-solid reaction inside a continuously operated fluidized bed reactor is evaluated. A so called ß-factor is defined as the ratio of the actual reactivity in

  13. Devolatilization and ignition of coal particles in a two-dimensional fluidized bed

    NARCIS (Netherlands)

    Prins, W.; Siemons, R.; Swaaij, van W.P.M.

    1989-01-01

    In a two-dimensional (15 × 200 × 400 mm) high-temperature fluidized bed, devolatilization ignition and combustion phenomena of single coal particles have been studied. The particles, with diameters of 4–9 mm, were selected from three coal types of widely different rank: brown coal, bituminous coal,

  14. DEM simulation of particle percolation in a packed bed

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The phenomenon of spontaneous particle percolation under gravity is investigated by means of the discrete element method. Percolation behaviors such as percolation velocity,residence time distribution and radial dispersion are examined under various conditions. It is shown that the vertical velocity of a percolating particle moving down through a packing of larger particles decreases with increasing the restitution coefficient between particles and diameter ratio of the percolating to packing particles. With the increase of the restitution coefficient,the residence time and radial dispersion of the percolating particles increase. The packing height affects the residence time and radial dispersion. But,the effect can be eliminated in the analysis of the residence time and radial dispersion when they are normalized by the average residence time and the product of the packing height and packing particle diameter,respectively.In addition,the percolation velocity is shown to be related to the vertical acceleration of the percolating particle when an extra constant vertical force is applied. Increasing the feeding rate of percolating particles decreases the dispersion coefficient.

  15. MULTI-SCALE AGGREGATION OF PARTICLES IN GAS-SOLIDS FLUIDIZED BEDS

    Institute of Scientific and Technical Information of China (English)

    Hongzhong Li

    2004-01-01

    The multi-scale characteristics of clusters in a fast fluidized bed and of agglomerates in a fluidized bed of cohesive particles are discussed on the basis of large amounts of experiments. The cluster size and concentration are dominated by the local voidage of the bed. A cluster consists of many sub-clusters with different sizes and discrete particles, and the sub-cluster size probability density distribution appears as a negative exponential function. The agglomerates in a fluidized bed of cohesive particles also possess the multi-scale nature. The large agglomerates form a fixed bed at the bottom, the medium agglomerates are fluidized in the middle, and the small agglomerates and discrete particles become the dilute-phase region in the upper part of the bed. The agglomerate size is mainly affected by cohesive forces and gas velocity. The present models for predicting the size of clusters and agglomerates can not tackle the intrinsic mechanism of the multi-scale aggregation, and a challenging problem for establishing mechanistic model is put forward.

  16. Mass Loss of Coal Particles Burning in Fluidized Bed

    Science.gov (United States)

    Pełka, Piotr

    2017-06-01

    In this work many conclusions resulting from research carried out on the coal combustion process of the chosen coal type and its accompanying erosion in a two-phase flow of inert material have been presented. The purpose of this flow was to present a model of the conditions of the central and upper zone of the combustion chamber of the fluidized boiler. In the opinion of many authors (Basu, 1999; Chirone et al., 1991), the erosion process results from the contact of a fuel particle with particles of inert material that is responsible for generating fine fuel particles of less than 100 mm. If the particles are in the upper zone of the boiler where there is oxygen deficit, they can increase the loss of incomplete combustion substantially. The results of research do not confirm this common thesis, but rather indicate that the process of comminution that results from erosion under oxidative conditions contributes to the increase of substantial mass loss of a coal particle, however the increased mass loss of particle during combustion is first and foremost due to the whole process of removal of ash from the reactionary surface of a fuel particle. Nevertheless, in the conditions of oxygen deficit the comminution of particles as a result of the erosion process is negligible

  17. Non-Gaussian properties of global momentum and particle fluxes in a cylindrical laboratory plasma

    Energy Technology Data Exchange (ETDEWEB)

    Nagashima, Yoshihiko; Yamada, Takuma [Graduate School of Frontier Sciences, University of Tokyo, Kashiwa 277-8561 (Japan); Itoh Research Center for Plasma Turbulence, Kyushu University, Kasuga 816-8580 (Japan); Itoh, Sanae-I.; Inagaki, Shigeru; Fujisawa, Akihide; Yagi, Masatoshi [Itoh Research Center for Plasma Turbulence, Kyushu University, Kasuga 816-8580 (Japan); Research Institute for Applied Mechanics, Kyushu University, Kasuga 816-8580 (Japan); Arakawa, Hiroyuki [Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Kasuga 816-8580 (Japan); Kasuya, Naohiro; Itoh, Kimitaka [Itoh Research Center for Plasma Turbulence, Kyushu University, Kasuga 816-8580 (Japan); National Institute for Fusion Science, Toki 509-5292 (Japan); Kamataki, Kunihiro [Center for Research and Advancement in Higher Education, Kyushu University, Fukuoka 816-8580 (Japan); Shinohara, Shunjiro [Institute of Engineering, Tokyo University of Agriculture and Technology, Koganei 184-8588 (Japan); Oldenbuerger, Stella [Itoh Research Center for Plasma Turbulence, Kyushu University, Kasuga 816-8580 (Japan); Takase, Yuichi [Graduate School of Frontier Sciences, University of Tokyo, Kashiwa 277-8561 (Japan); Diamond, Patrick H. [Itoh Research Center for Plasma Turbulence, Kyushu University, Kasuga 816-8580 (Japan); Center for Astrophysics and Space Sciences, University of California San Diego, La Jolla, California 92093 (United States)

    2011-07-15

    Non-Gaussian statistical properties of the azimuthally averaged momentum and particle fluxes driven by turbulence have been simultaneously observed in inhomogeneous magnetized plasmas for the first time. We identified the stretched Gaussian distribution of the both fluxes and the transition from the point-wise distribution to averaged ones was confirmed. The change of the particle flux precedes that of the momentum flux, demonstrating that the momentum flux is induced by the relaxation of density gradient.

  18. The Indianapolis Flux Experiment (INFLUX: A test-bed for developing urban greenhouse gas emission measurements

    Directory of Open Access Journals (Sweden)

    Kenneth J. Davis

    2017-05-01

    Full Text Available The objective of the Indianapolis Flux Experiment (INFLUX is to develop, evaluate and improve methods for measuring greenhouse gas (GHG emissions from cities. INFLUX’s scientific objectives are to quantify CO2 and CH4 emission rates at 1 km2 resolution with a 10% or better accuracy and precision, to determine whole-city emissions with similar skill, and to achieve high (weekly or finer temporal resolution at both spatial resolutions. The experiment employs atmospheric GHG measurements from both towers and aircraft, atmospheric transport observations and models, and activity-based inventory products to quantify urban GHG emissions. Multiple, independent methods for estimating urban emissions are a central facet of our experimental design. INFLUX was initiated in 2010 and measurements and analyses are ongoing. To date we have quantified urban atmospheric GHG enhancements using aircraft and towers with measurements collected over multiple years, and have estimated whole-city CO2 and CH4 emissions using aircraft and tower GHG measurements, and inventory methods. Significant differences exist across methods; these differences have not yet been resolved; research to reduce uncertainties and reconcile these differences is underway. Sectorally- and spatially-resolved flux estimates, and detection of changes of fluxes over time, are also active research topics. Major challenges include developing methods for distinguishing anthropogenic from biogenic CO2 fluxes, improving our ability to interpret atmospheric GHG measurements close to urban GHG sources and across a broader range of atmospheric stability conditions, and quantifying uncertainties in inventory data products. INFLUX data and tools are intended to serve as an open resource and test bed for future investigations. Well-documented, public archival of data and methods is under development in support of this objective.

  19. Autonomous, high-resolution observations of particle flux in the oligotrophic ocean

    Directory of Open Access Journals (Sweden)

    M. L. Estapa

    2013-01-01

    Full Text Available Observational gaps limit our understanding of particle flux attenuation through the upper mesopelagic because available measurements (sediment traps and radiochemical tracers have limited temporal resolution, are labor-intensive, and require ship support. Here, we conceptually evaluate an autonomous, optical proxy-based method for high-resolution observations of particle flux. We present four continuous records of particle flux collected with autonomous, profiling floats in the western Sargasso Sea and the subtropical North Pacific, as well as one shorter record of depth-resolved particle flux near the Bermuda Atlantic Timeseries Study (BATS and Oceanic Flux Program (OFP sites. These observations illustrate strong variability in particle flux over very short (~1 day timescales, but at longer timescales they reflect patterns of variability previously recorded during sediment trap timeseries. While particle flux attenuation at BATS/OFP agreed with the canonical power-law model when observations were averaged over a month, flux attenuation was highly variable on timescales of 1–3 days. Particle fluxes at different depths were decoupled from one another and from particle concentrations and chlorophyll fluorescence in the immediately-overlying surface water, consistent with horizontal advection of settling particles. We finally present an approach for calibrating this optical proxy in units of carbon flux, discuss in detail the related, inherent physical and optical assumptions, and look forward toward the requirements for the quantitative application of this method in highly time-resolved studies of particle export and flux attenuation.

  20. Autonomous, high-resolution observations of particle flux in the oligotrophic ocean

    Directory of Open Access Journals (Sweden)

    M. L. Estapa

    2013-08-01

    Full Text Available Observational gaps limit our understanding of particle flux attenuation through the upper mesopelagic because available measurements (sediment traps and radiochemical tracers have limited temporal resolution, are labor-intensive, and require ship support. Here, we conceptually evaluate an autonomous, optical proxy-based method for high-resolution observations of particle flux. We present four continuous records of particle flux collected with autonomous profiling floats in the western Sargasso Sea and the subtropical North Pacific, as well as one shorter record of depth-resolved particle flux near the Bermuda Atlantic Time-series Study (BATS and Oceanic Flux Program (OFP sites. These observations illustrate strong variability in particle flux over very short (~1-day timescales, but at longer timescales they reflect patterns of variability previously recorded during sediment trap time series. While particle flux attenuation at BATS/OFP agreed with the canonical power-law model when observations were averaged over a month, flux attenuation was highly variable on timescales of 1–3 days. Particle fluxes at different depths were decoupled from one another and from particle concentrations and chlorophyll fluorescence in the immediately overlying surface water, consistent with horizontal advection of settling particles. We finally present an approach for calibrating this optical proxy in units of carbon flux, discuss in detail the related, inherent physical and optical assumptions, and look forward toward the requirements for the quantitative application of this method in highly time-resolved studies of particle export and flux attenuation.

  1. Vertical variation of particle speed and flux density in aeolian saltation: Measurement and modeling

    Science.gov (United States)

    Rasmussen, Keld R.; SøRensen, Michael

    2008-06-01

    Particle dynamics in aeolian saltation has been studied in a boundary layer wind tunnel above beds composed of quartz grains having diameters of either 242 μm or 320 μm. The cross section of the tunnel is 600 mm × 900 mm, and its thick boundary layer allows precise estimation of the fluid friction speed. Saltation is modeled using a numerical saltation model, and predicted grain speeds agree fairly well with experimental results obtained from laser-Doppler anemometry. The use of laser-Doppler anemometry to study aeolian saltation is thoroughly discussed and some pitfalls are identified. At 80 mm height the ratio between air speed and grain speed is about 1.1 and from there it increases toward the bed so that at 5 mm it is about 2.0. All grain speed profiles converge toward a common value of about 1 m/s at 2-3 mm height. Moreover, the estimated launch velocity distributions depend only very weakly on the friction speed in contrast to what has often been assumed in the literature. Flux density profiles measured with a laser-Doppler appear to be similar to most other density profiles measured with vertical array compartment traps; that is, two exponential segments will fit data between heights from a few millimeters to 100-200 mm. The experimental flux density profiles are found to agree well with model predictions. Generally, validation rates are low from 30 to 50% except at the highest level of 80 mm, where they approach 80%. When flux density profiles based on the validated data are used to estimate the total mass transport rate results are in fair agreement with measured transport rates except for conditions near threshold where as much as 50% difference is observed.

  2. Computational study of fluid flow and heat transfer in composite packed beds of spheres with low tube to particle diameter ratio

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Jian, E-mail: yangjian81@mail.xjtu.edu.cn [Key Laboratory of Thermo-Fluid Science and Engineering, Ministry of Education, School of Energy and Power Engineering, Xi’an Jiaotong University, Xi’an, Shaanxi 710049 (China); Wu, Jiangquan [CSR Research of Electrical Technology and Material Engineering, Zhuzhou, Hunan 412001 (China); Zhou, Lang; Wang, Qiuwang [Key Laboratory of Thermo-Fluid Science and Engineering, Ministry of Education, School of Energy and Power Engineering, Xi’an Jiaotong University, Xi’an, Shaanxi 710049 (China)

    2016-04-15

    Highlights: • Flow and heat transfer in composite packed beds with low d{sub t}/d{sub pe} are investigated. • The wall effect would be restrained with radially layered composite packing (RLM). • Heat flux and overall heat transfer efficiency can be improved with RLM packing. - Abstract: The effect of the tube wall on the fluid flow and heat transfer would be important in the packed bed with low tube to particle diameter ratio, which may lead to flow and temperature maldistributions inside, and the heat transfer performance may be lowered. In the present paper, the flow and heat transfer performances in both the composite and uniform packed beds of spheres with low tube to particle diameter were numerically investigated, where the composite packing means randomly packing with non-uniform spheres and the uniform packing means randomly packing with uniform spheres, including radially layered composite packing (RLM), axially layered composite packing (ALM), randomly composite packing (RCM) and randomly uniform packing (RPM). Both the composite and uniform packings were generated with discrete element method (DEM), and the influence of the wall effect on the flow and heat transfer in the packed beds were carefully studied and compared with each other. Firstly, it is found that, the wall effect on the velocity and temperature distributions in the randomly packed bed of uniform spheres (RPM) with low tube to particle diameter ratio were obvious. The average velocity of the near-tube-wall region is higher than that of the inner-tube region in the bed. When the tube wall is adiabatic, the average temperature of the near-tube-wall region is lower. With radially layered composite packing method (RLM), smaller pores would be formed close to the tube wall and big flow channels would be formed in the inner-tube region of the bed, which would be benefit to restrain the wall effect and improve heat transfer in the bed with low tube to particle diameter ratio. Furthermore, it

  3. Discrete particle modeling of granular temperature distribution in a bubbling fluidized bed

    Institute of Scientific and Technical Information of China (English)

    Yurong He; Tianyu Wang; Niels Deen; Martin van Sint Annaland; Hans Kuipers; Dongsheng Wen

    2012-01-01

    The discrete hard sphere particle model (DPM) is applied in this work to study numerically the distributions of particle and bubble granular temperatures in a bubbling fluidized bed.The dimensions of the bed and other parameters are set to correspond to those of Müller et al.(2008).Various drag models and operational parameters are investigated to find their influence on particle and bubble granular temperatures.Various inlet superficial gas velocities are used in this work to obtain their effect on flow characteristics.It is found that the superficial gas velocity has the most important effect on granular temperatures including bubble granular temperature,particle translational granular temperature and particle rotational granular temperature.The drag force model affects more seriously the large scale variables such as the bubble granular temperature.Restitution coefficient influences all granular temperatures to some degree.Simulation results are compared with experimental results by Müller et al.(2008) showing reasonable agreement.

  4. Orientation of cylindrical particles in gas-solid circulating fluidized bed

    Institute of Scientific and Technical Information of China (English)

    Jie Cai; Qihe Li; Zhulin Yuan

    2012-01-01

    The orientation of cylindrical particles in a gas-solid circulating fluidized bed was investigated by establishing a three-dimensional Euler-Lagrange model on the basis of rigid kinetics,impact kinetics and gas-solid two-phase flow theory.The resulting simulation indicated that the model could well illustrate the orientation of cylindrical particles in a riser during fluidization,The influences of bed structure and operation parameters on orientation of cylindrical particles were then studied and compared with related experimental results.The simulation results showed that the majority of cylindrical particles move with small nutation angles in the riser,the orientation of cylindrical particles is affected more obviously by their positions than by their slenderness and local gas velocities.The simulation results well agree with experiments,thus validating the proposed model and computation.

  5. A Determination of Particle Density Distributions Above Fluidized Beds.

    Science.gov (United States)

    1985-03-01

    suggested by Lewis et al (31 and Kunii and Levenspiel E1 to model the particle loading within the freeboard. 7Z 1 J 4:W-,W T- i7e.7 7 U1 T 7..C.. C Z R A i...at the nose of a bubble and would therefore have the bubbles velocity. To determine the bubble velocity, Kunii and Levenspiel (I give the follouing...REFERENCES [1] 0. Kunii and 0. Levenspiel , Fluidization Engineerina

  6. EXPERIMENTAL STUDY ON INCIPIENT MOTION OF SEDIMENT PARTICLES ON GENERALIZED SLOPING FLUVIAL BEDS

    Institute of Scientific and Technical Information of China (English)

    Subhasish DEY

    2001-01-01

    This paper presents an experimental investigation on incipient motion of non-cohesive uniform sediment under a steady-uniform stream flow on generalized sloping fluvial beds (combined lateral and stream-wise slope). The characteristic parameters affecting the incipient motion of sediment particles, identified based on the physical reasoning and dimensional analysis, are the threshold shear stress ratio (ratio of threshold shear stress for sloping bed to that for horizontal bed), lateral slope,stream-wise slope and angle of repose of sediment particles. Experiments were carried out in two ducts (closed-conduit flow) having section of semicircular invert with three types of sediments. In an open channel flow (laboratory flume study), the uniform flow is a difficult, if not impossible,proposition for a steeply sloping channel and is impossible to obtain in an adversely sloping channel.To avoid this problem, the tests were conducted with a closed-conduit flow. Equation of critical bed shear stress for the initial movement of sediment particles on generalized sloping beds was obtained using the experimental data.

  7. Experimental validation of granular dynamics simulations of gas-fluidised beds with homogeneous inflow conditions using Positron Emission Particle Tracking

    NARCIS (Netherlands)

    Hoomans, B.P.B.; Kuipers, J.A.M.; Mohd Salleh, M.; Seville, J.P.

    2001-01-01

    A hard-sphere granular dynamics model of a two-dimensional gas-fluidised bed was experimentally validated using Positron Emission Particle Tracking (PEPT). In the model the Newtonian equations of motion are solved for each solid particle while taking into account the particle¿particle and particle¿w

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  9. Bubbling bed catalytic hydropyrolysis process utilizing larger catalyst particles and smaller biomass particles featuring an anti-slugging reactor

    Science.gov (United States)

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

    2014-09-23

    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.

  10. 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.

  11. Tube array heat transfer in fluidized beds; a study of particle size effects

    Energy Technology Data Exchange (ETDEWEB)

    Chung, T.Y.; Welty, J.R. (Oregon State Univ., Corvallis, OR (USA). Dept. of Mechanical Engineering)

    1989-07-01

    Experiments were performed with an array of horizontal tubes, arranged in a regular equilateral triangular pattern, immersed in a fluidized bed operating at 812 {Kappa}. Data are reported for heat transfer between the bed and a centrally-located tube in the array. Both total and radiative heat transfer rates were measured for superficial velocities spanning the range from packed bed conditions to over twice the minimum fluidization velocity. Results are presented for five different-size particles. Local heat transfer values, measured around the tube periphery, and integrated averages are reported for all test conditions. Comparisons are also made between the heat transfer behavior of a tube in an array and that for a single tube in a hot fluidized bed under the same overall operating conditions. The results of this comparison suggests that the two mechanisms, gas convection and radiation, are competing effects.

  12. Experiments and Modeling of the Preparation of Ultrafine Calcium Carbonate in Spouted Beds with Inert Particles

    Institute of Scientific and Technical Information of China (English)

    林诚; 朱涛; 朱跃姿; 张济宇

    2003-01-01

    A novel reaction-drying process was carried out in a spouted bed reactor with inert particles and used to prepare ultrafine CaCO3 particles. Effects of concentrations of CO2 and Ca(OH)2, and reaction temperature on Ca(OH)2 conversion were experimentally investigated. The particle sizes and composition of CaCO3 produced were characterized with transmission electron microscopy (TEM) and X-ray diffraction (XRD). The results indicated that ultrafine CaCO3 particles with mean size of 80 nm could be obtained with this novel process.By modifying the Arrhenius Equation and considering the Ca(OH)2 state, a kinetic model was established to describe the process in the spouted bed. The model parameters estimated from the reaction-drying experiments were found to fit well the experimental data, indicating the applicability of the proposed kinetic model.

  13. MULTIFRACTAL ANALYSIS OF PARTICLE-FLUID SYSTEM IN A CIRCULATING FLUIDIZED BED

    Institute of Scientific and Technical Information of China (English)

    Liping; Ma; Weixing; Huang; Yanfu; Shi; Huarui; Yu; Jingxu; Zhu

    2005-01-01

    In this paper, multifractal analysis together with wavelet transform modulus maxima (WTMM) method is used to analyze the fluctuating signals of circulating fluidized bed (CFB). Singularity spectrum shows that the gas-particle flow in CFB has multifractal character. Motion behavior of the particle-fluid system of CFB can be described by singularity spectrum. Intermittency index can be used to determine the transition of flow regime from fast fluidization to pneumatic conveying.

  14. Fluidized-bed reactor model with generalized particle balances. Part 2. Coal combustion application

    Energy Technology Data Exchange (ETDEWEB)

    Overturf, B.W.; Reklaitis, G.V.

    1983-09-01

    In the second part, the model is applied to the study of an atmospheric fluidized-bed coal combustor. Case studies are investigated to show the effects of a number of parameters. Proper representation of the grid region and use of actual feed distributions are shown to be essential to the prediction of combustor performance. Better particle elutriation and single-particle combustion sub-models are found to be key requirements for improved combustor modelling.

  15. Influence of tube and particle diameter on heat transport in packed beds

    NARCIS (Netherlands)

    Borkink, J.G.H.; Borkink, J.G.H.; Westerterp, K.R.

    1992-01-01

    Influence of the tube and particle diameter and shape, as well as their ratio, on the radial heat transport in packed beds has been studied. Heat transport experiments were performed with four different packings in three wall-cooled tubes, which differed in inner diameter only. Experimental values f

  16. Influence of tube and particle diameter on heat transport in packed beds

    NARCIS (Netherlands)

    Borkink, J.G.H.; Borkink, J.G.H.; Westerterp, K.R.

    1992-01-01

    Influence of the tube and particle diameter and shape, as well as their ratio, on the radial heat transport in packed beds has been studied. Heat transport experiments were performed with four different packings in three wall-cooled tubes, which differed in inner diameter only. Experimental values

  17. Drying of suspension and pastes in fluidized bed of inert particles

    Directory of Open Access Journals (Sweden)

    ZORANA LJ. ARSENIJEVIC

    2000-12-01

    Full Text Available A fluid bed dryer with inert particles was used for the drying of suspensions and pastes. The effects of the operating conditions on the dryer throughput and on the product quality were investigated. Experiments were performed in a cylindrical column 215 mm in diameter and 1200 mm in height with 0.925 mm diameter glass spheres as the fluidizing media. Cineb fungicide, copper hydroxide and pure water were used as the feed material. With respect to the main efficiency criteria, i.e., specific water evaporation rate, specific heat consumption and specific air consumption, a fluid bed dryer with inert particles represents a very attractive alternative to other drying technologies. A high drying efficiency results from the large contact area and from the large temperature difference between the inlet and outlet air. A rapid mixing of the particles, due to aggregative fluidization and mechanical agitation, leads to nearly isothermal conditions throughout the bed. In our experiments, suspensions and very dense pastes were successfully treated. Suspension and product hold-up in the bed varies between 6 and 8 % by mass and a product with the same particle size as the raw material is obtained.

  18. PARTICLE FLOW, MIXING, AND CHEMICAL REACTION IN CIRCULATING FLUIDIZED BED ABSORBERS

    Science.gov (United States)

    A mixing model has been developed to simulate the particle residence time distribution (RTD) in a circulating fluidized bed absorber (CFBA). Also, a gas/solid reaction model for sulfur dioxide (SO2) removal by lime has been developed. For the reaction model that considers RTD dis...

  19. Particle Flow Cell Formation at Minimum Fluidization Flow Rates in a Rectangular Gas-Fluidized Bed.

    Science.gov (United States)

    1981-03-01

    Kunii and Levenspiel Model ----------------- 66 C. FLUIDIZED BED VARIABLES THAT AFFECT HEAT TRANSFER ---------------------------------- 69 5 1...and Levenspiel Model -------------------------- 68 25. Heat transfer coefficient vs. mass velocity --------- 72 26. Contact geometry of surface-particle...becomes a very important factor. According to Kunii and Levenspiel [34], distributors should have a sufficient pressure drop to achieve equal flow

  20. 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 no

  1. Particle Dispersion Behaviors of Dense Gas-Particle Flows in Bubble Fluidized Bed

    OpenAIRE

    Xue Liu; Guohui Li; Sihao Lv

    2013-01-01

    An Euler-Euler two-fluid model incorporating a developed momentum transfer empirical coefficient is developed to study the particle dispersion behaviors of dense gas-particle flows in gas-fluidization reactor. In this model, the four-way couplings among gas-particles, particle-gas, and particle-particle collisions are fully considered based on kinetic theory of granular flows and an improved smooth continuous drag coefficient is utilized. Gas turbulent flow is solved by large eddy simulation....

  2. Improving flow properties of ibuprofen by fluidized bed particle thin-coating.

    Science.gov (United States)

    Ehlers, Henrik; Räikkönen, Heikki; Antikainen, Osmo; Heinämäki, Jyrki; Yliruusi, Jouko

    2009-02-23

    The surfaces of ibuprofen particles (d(50) 42 microm) were modified by coating the particles with diluted aqueous hydroxypropyl methylcellulose (HPMC) solution in an instrumentated top-spray fluid bed granulator. The objective was to evaluate whether an extremely thin polymer coating could be an alternative to granulation in enhancing powder flow and processing properties. The studied variables were inlet air temperature and spray rate. The treated powders showed a clear improvement in flow rate as measured with a flow meter designed for powders with poor flow properties. The particle size was determined using optical microscopy and image analysis. The particle size, size distribution and circularity of the treated and untreated ibuprofen batches showed no difference from each other. Consequently, the improvement in flow properties can be attributed to the trace amounts of hydroxypropyl methylcellulose applied onto the particle surfaces. In conclusion, fluidized bed particle thin-coating (PTC) alters the surface of ibuprofen powder particles and improves the flow properties of ibuprofen powder with changes in neither particle size, size distribution nor morphology.

  3. Surface-particle-emulsion heat transfer model between fluidized bed and horizontal immersed tube

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A mathematical model, surface-particle-emulsion heat transfer model, is presented by considering voidage variance in emulsion in the vicinity of an immersed surface. Heat transfer near the surface is treated by dispersed particles touching the surface and through the emulsion when the distance from the surface is greater than the diameter of a particle. A film with an adjustable thickness which separates particles from the surface is not introduced in this model. The coverage ratio of particles on the surface is calculated by a stochastic model of particle packing density on a surface. By comparison of theoretical solutions with experimental data from some references, the mathematical model shows better qualitative and quantitative prediction for local heat transfer coefficients around a horizontal immersed tube in a fluidized bed.

  4. Temperatures of coal particle during devolatilization in fluidized bed combustion reactor

    Energy Technology Data Exchange (ETDEWEB)

    Komatina, M.; Manovic, V.; Saljnikov, A. [University of Belgrade, Belgrade (Serbia). Faculty of Mechanical Engineering

    2006-11-15

    The purpose of this study was to investigate the thermal behavior of coal during devolatilization in fluidized bed. Temperatures in the center of single coal particle were measured by thermocouple. Two coals were tested (brown coal Bogovina and lignite Kosovo), using dry coal particle, shaped into spherical form of diameters 7 and 10 mm, in temperature range from 300 to 850{sup o}C. Unsteady behavior of coal particle during heating and devolatilization in fluidized bed was described by a model that takes into account heat transfer between bed and particle surface, heat transfer through particle and an endothermic chemical reaction of first-order. Based on the mathematical model analysis and compared with experimental results, values of heat conductivity {lambda}{sub C} and heat capacity (C-p) of coal were determined. The best agreement was obtained for constant thermal properties, for brown coal {lambda}{sub C} = 0.20 W/mK and C{sub p} = 1200 J/kgK and for lignite {lambda}{sub C} = 0.17 W/mK and C-p = 1100 J/kgK.

  5. Characteristic Studies of Micron Zinc Particle Hydrolysis in a Fixed Bed Reactor

    Directory of Open Access Journals (Sweden)

    Lv Ming

    2015-09-01

    Full Text Available Zinc fuel is considered as a kind of promising energy sources for marine propeller. As one of the key steps for zinc marine energy power system, zinc hydrolysis process had been studied experimentally in a fixed bed reactor. In this study, we focus on the characteristics of micron zinc particle hydrolysis. The experimental results suggested that the steam inner diffusion is the controlling step of accumulative zinc particles hydrolysis reaction at a relative lower temperature and a relative higher water partial pressure. In other conditions, the chemical reaction kinetics was the controlling step. And two kinds of chemical reaction kinetics appeared in experiments: the surface reaction and the gas-gas reaction. The latter one occurs usually for larger zinc particles and high reaction temperature. Temperature seems to be one of the most important parameters for the dividing of different reaction mechanisms. Several parameters of the hydrolysis process including heating rate, water partial pressure, the particle size and temperature were also studied in this paper. Results show that the initial reaction temperature of zinc hydrolysis in fixed bed is about 410°C. And the initial reaction temperature increases as the heating rate increases and as the water partial pressure decreases. The total hydrogen yield increases as the heating rate decreases, as the water partial pressure increases, as the zinc particle size decreases, and as the reaction temperature increases. A hydrogen yield of more than 81.5% was obtained in the fixed bed experiments.

  6. Modeling of laser radiation transport in powder beds with high-dispersive metal particles

    Energy Technology Data Exchange (ETDEWEB)

    Kharanzhevskiy, Evgeny, E-mail: eh@udsu.ru [Udmurt State University, 426034 Universitetskaya St., 1, Izhevsk (Russian Federation); Kostenkov, Sergey [Udmurt State University, 426034 Universitetskaya St., 1, Izhevsk (Russian Federation)

    2014-02-15

    Highlights: ► Transport of laser energy in dispersive powder beds was numerically simulated. ► The results of simulating are compared with physicals experiments. ► We established the dependence of the extinction coefficient from powder properties. ► A confirmation of a geometric optic approach for monodisperse powders was proposed. -- Abstract: Two-dimensional transfer of laser radiation in a high-dispersive powder heterogeneous media is numerically calculated. The size of particles is comparable with the wave length of laser radiation so the model takes into account all known physical effects that are occurred on the vacuum–metal surface interface. It is shown that in case of small particles size both morphology of powder particles and porosity of beds influence on absorptance by the solid phase and laser radiation penetrate deep into the area of geometric shadow. Intensity of laser radiation may be described as a function corresponded to the Beer–Lambert–Bouguer law.

  7. Study of Influence of Experimental Technique on Measured Particle Velocity Distributions in Fluidized Bed

    Science.gov (United States)

    Gopalan, Balaji; Shaffer, Frank

    2013-11-01

    Fluid flows that are loaded with high concentration of solid particles are common in oil and chemical processing industries. However, the opaque nature of the flow fields and the complex nature of the flow have hampered the experimental and computational study of these processes. This has led to the development of a number of customized experimental techniques for high concentration particle flows for evaluation and improvement of CFD models. This includes techniques that track few individual particles, measures average particle velocity over a small sample volume and those over a large sample volume. In this work novel high speed PIV (HsPIV), with individual particle tracking, was utilized to measure velocities of individual particles in gas-particle flow fields at the walls circulating and bubbling fluidized bed. The HsPIV measurement technique has the ability to simultaneously recognize and track thousands of individual particles in flows of high particle concentration. To determine the effect of the size of the sample volume on particle velocity measurements, the PDF of Lagrangian particle velocity was compared with the PDF of Eulerian for different domain sizes over a range of flow conditions. The results will show that measured particle velocity distribution can vary from technique to technique and this bias has to be accounted in comparison with CFD simulations.

  8. Motion behavior of particles in air-solid magnetically stabilized fluidized beds for separation

    Institute of Scientific and Technical Information of China (English)

    Song Shulei; Zhao Yuemin; Luo Zhenfu; Tang Ligang

    2012-01-01

    In order to study the settling mechanism of particles in an air-solid magnetically stabilized fluidized bed (MSFB) for separation,we carried out free settling and quasi-zero settling tests on the tracing particles.The results show that the main resistance forces as the tracing particles settled in an air-solid MSFB were motion resistance force and yield force.The motion resistance and yield forces greatly hindered the free settling of the particles by greatly decreasing the acceleration for settling process of the particles.The acceleration decreased from 3022.62 cm/s2 to zero in 0.1 s,and in the end,the particles stopped in the air-solid MSFB.The yield force on particles increased with increasing the magnetic field intensity,resulting in decrease of the quasi-zero settling displacement.However,the yield force on particles decreased with increasing the fluidized air velocity,leading to increase of the quasi-zero settling displacement.When the structure and operating parameters of the air-solid MSFB were set up,the yield stress on particles stopped in an air-solid MSFB was a function of diameter and density of particles.The settling displacements of equal diameter particles increased with increasing their densities,and the settling displacements of equal density particles increased with increasing their diameters.

  9. Effect of particle size and interparticle force on the fluidization behavior of gas-fluidized beds.

    Science.gov (United States)

    Valverde, J M; Castellanos, A; Mills, P; Quintanilla, M A S

    2003-05-01

    Gas-fluidized powders of fine particles display a fluidlike regime in which the bed does not have a yield strength, it expands uniformly as the gas velocity is increased and macroscopic bubbles are absent. In this paper we test the extension of this fluidlike regime as a function of particle size and interparticle attractive force. Our results show that for sufficiently large particles, bubbling initiates just after the solidlike fluidized regime as it is obtained experimentally by other workers. A scaling behavior of the solid-phase pressure in the fluidlike regime and a predictive criterion for the onset of macroscopic bubbling are analyzed in the light of these results.

  10. NONUNIFORMITIES OF TWO-PHASE COOLANT DISTRIBUTION IN A HEAT GENERATING PARTICLES BED

    Directory of Open Access Journals (Sweden)

    V. V. Sorokin

    2014-01-01

    Full Text Available Sufficient atomic power generation safety increase may be done with microfuel adapting to reactor plants with water coolant. Microfuel particle is a millimeter size grain containing fission material core in a protecting coverage. The coverage protects fuel contact with coolant and provides isolation of fission products inside. Well thermophysical properties of microfuel bed in a direct contact with water coolant excludes fuel overheating when accidents. Microfuel use was suggested for a VVER, а direct flow reactor for superheat steam generation, a reactor with neutron spectra adjustment by the steam partial content varying in the coolant.Nonuniformities of two-phase coolant distribution in a heat generating particles bed are predicted by calculations in this text. The one is due to multiple-valuedness of pressure drop across the bed on the steam quality dependency. The nonuniformity decreases with flow rate and particle size growths absolute pressure diminishing while porosity effect is weak. The worse case is for pressure quality of order of one. Some pure steam filled pores appears parallel to steam water mixture filled pores, latter steam quality is less than the mean of the bed. Considering this regime for the direct flow reactor for superheat steam generation we predict some water drops at the exit flow. The two-phase coolant filtration with subcooled water feed is unstable to strong disturbance effects are found. Uniformity of two-phase coolant distribution is worse than for one-phase in the same radial type reactor.

  11. Modeling the injection of gas-liquid jets into fluidized bed of fine particles

    Energy Technology Data Exchange (ETDEWEB)

    Aryiapadi, S.; Berutti, F.; Briens, C.; Hulet, C. [Western Ontario University, Dept. of Chemical and Biochemical Engineeering, London, ON (Canada); Griffith, P. [Massachussetts Institute of Technology, Dept. of Mechanical Engineering, Cambridge, MA (United States)

    2003-08-01

    A simplified momentum-based approach to calculate the solid entrainment rate into a gas-liquid jet injected into a fluidized bed is described. The model is verified by a recently developed experimental technique. The paper also addresses correction factors to the initial momentum calculated from the homogenous model. The solids entrainment rates predicted by the model were found to be very close to experimentally obtained values. It is suggested that the model can be usefully employed in characterizing the behaviour of gas-liquid jets injected into fluidized beds of fine particles. 21 refs., 8 figs.

  12. Spatial and Temporal Patterns of Bed Mobility Revealed Through the Use of Hydrodynamic Modeling and Motion-Sensing Radio Tagged Particles in a Large Gravel-Bed River

    Science.gov (United States)

    May, C. L.; Smith Pryor, B.; Lisle, T. E.; Lang, M. M.

    2010-12-01

    Flow conditions that initiate bedload transport, and an understanding of the spatial and temporal variability in bed mobility, provide important insight into the dynamics of riverine habitat. However, quantifying these processes at the reach scale has been elusive, especially in large river systems. Our approach coupled hydrodynamic modeling and empirical measures of bed mobility based on traditional tracers and motion-sensing radio tagged particles to determine flow conditions at initial motion and the spatial extent of bed mobility in the Trinity River of northern California. High-resolution bathymetric surveying and grain size measurements were used as input for hydrodynamic modeling. A narrow band Acoustic Doppler Profiler positioned using a Real Time Kinematic global positioning system provided separate calibration and validation data during flood events. Model-predicted Shields stress identified spatially explicit zones of differential bed mobility and indicated that a potential zone of full mobility was limited to a central core that expanded with increasing flow strength. Model-predicted zones of full mobility were well validated by patches of traditional painted rock tracer particles. In addition to traditional tracers, motion-sensing radio tagged particles were used to identify the timing of initial motion. By simultaneously measuring discharge, and modeling bed forces at that discharge, shear stress at initial motion was calculated. These calculations revealed that initial motion of bed particles varied substantially between flood events. Temporal variability in the distribution of critical shear stress suggests that the sequence of flood events is an important determinant of bed strength and, thus, resistance to motion. The combined use of high-resolution instrumentation and flow modeling revealed important insight into the importance of bed conditioning by previous floods on bed mobility.

  13. Processes determining seasonality and interannual variability of settling particle fluxes to the deep Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Haake, B.; Rixen, T.; Reemtsma, T.; Ramaswamy, V.; Ittekkot, V.

    stream_size 20 stream_content_type text/plain stream_name Particle_Flux_Ocean_Chapter_14_1996_251.pdf.txt stream_source_info Particle_Flux_Ocean_Chapter_14_1996_251.pdf.txt Content-Encoding ISO-8859-1 Content-Type text...

  14. Fresh water influx and particle flux variability in the Bay of Bengal

    Digital Repository Service at National Institute of Oceanography (India)

    Schafer, P.; Ittekkot, V.; Bartsch, M.; Nair, R.R.; Tiemann, J.

    stream_size 22 stream_content_type text/plain stream_name Particle_Flux_Ocean_Chapter_15_1996_271.pdf.txt stream_source_info Particle_Flux_Ocean_Chapter_15_1996_271.pdf.txt Content-Encoding ISO-8859-1 Content-Type text...

  15. Increased particle fluxes at the INDEX site attributable to simulated benthic disturbance

    Digital Repository Service at National Institute of Oceanography (India)

    Parthiban, G.

    Indian Basin. The predisturbance particle fluxes varied between 22.3 to 55.1 mg m sup(-2) day sup(-1). Increased and variable particle fluxes were recorded by the sediment traps during the disturbance period. The increase observed was 0.5 to 4 times more...

  16. Particle fluxes in the Bay of Bengal measurEd. by sediment traps

    Digital Repository Service at National Institute of Oceanography (India)

    Ramaswamy, V.; Parthiban, G.

    Particle fluxes were measured between October, 1987 and March, 1988 using six automated time series sediment traps at three locations in the northern, central and southern Bay of Bengal. Particle fluxes varied between 16.8 and 345 mg m/2 day/1...

  17. Evaluation of energetic particle parameters in the near-Earth magnetotail derived from flux asymmetry observations

    Directory of Open Access Journals (Sweden)

    Z. Y. Pu

    Full Text Available The flux asymmetries measured by spectrometers on board spacecraft contain information on particle parameters. The net flux intensity (NFI method provides a tool to evaluate these parameters. The NFI method is valid when both the spin period of the spacecraft and the time resolution of the particle spectrometers are much shorter than the characteristic time-scale of the particle flux variations. We apply the NFI analysis to the flux asymmetry measurements made by GEOS 2 at the nightside geosynchronous orbit in the late substorm growth phase. The cross-tail current of energetic ions, their pressure gradient and average drift velocity, as well as a field-aligned flows are investigated. Current disruption at substorm onset and the "convection surge" mechanism during dipolarization of the magnetic field are directly observed.

    Key words. Flux asymmetry · Net flux intensity · GEOS 2 · Energetic particles

  18. Comparative analysis of CFD models for jetting fluidized beds: Effect of particle-phase viscosity

    Institute of Scientific and Technical Information of China (English)

    Pei Pei; Kai Zhang; Gang Xu; Yongping Yang; Dongsheng Wen

    2012-01-01

    Under the Eulerian-Eulerian framework of simulating gas-solid two-phase flow,the accuracy of the hydrodynamic prediction is strongly affected by the selection of rheology of the particulate phase,for which a detailed assessment is still absent.Using a jetting fluidized bed as an example,this work investigates the influence of solid theology on the hydrodynamic behavior by employing different particle-phase viscosity models.Both constant particle-phase viscosity model (CVM) with different viscosity values and a simple two-fluid model without particle-phase viscosity (NVM) are incorporated into the classical twofluid model and compared with the experimental measurements.Qualitative and quantitative results show that the jet penetration depth,jet frequency and averaged bed pressure drop are not a strong function of the particle-phase viscosity.Compared to CVM,the NVM exhibits better predictions on the jet behaviors,which is more suitable for investigating the hydrodynamics of gas-solid fluidized bed with a central jet.

  19. Effect of Fluidized Bed Stirring on Drying Process of Adhesive Particles

    Directory of Open Access Journals (Sweden)

    P. Hoffman

    2017-04-01

    Full Text Available This paper presents an attempt to optimize fluidized bed drying of wet and adhesive particles (with an initial diameter of about 580 mm with the use of stirring, and discusses the influence of stirring on the total drying time. The goal was to demonstrate the positive effect of stirring a fluidized bed to the drying time, to find the optimal parameters (stirrer design, speed, and size. Experiments were conducted on a drying chamber in batch operation. The objective was to evaluate the effect of stirring on the total drying time. The drying chambers were 85 mm, 100 mm, and 140 mm in diameter. An optimal stirrer shape and speed were specified. Our arrangement of the fluidized bed resulted in a decrease in drying time by up to 40 %.

  20. Formation of abrasive hollow particles in lignite-fired fluidised bed boilers; Bildung abrasiver Hohlpartikel in braunkohlenbefeuerten Wirbelschichtkessel

    Energy Technology Data Exchange (ETDEWEB)

    Kappler, Uta [RWE Power AG, Koeln (Germany). Forschung und Entwicklung Hauptverwaltung; Roeper, Bernhard [RWE Power AG, Grevenbroich (Germany). Technische Dienste Kraftwerk Frimmersdorf; Voss, Petra [RWE Power AG, Bergheim (Germany). Forschung und Entwicklung Kraftwerk Niederaussem

    2013-04-01

    The formation of voluminous and highly abrasive hollow particles in raw-lignite-fired circulating fluidised-bed (CFB) boilers of RWE Power AG is a well-known phenomenon. Operational measures were taken to avoid particle formation and related damage. By the end of 2011 another boiler damage occurred. Within the scope of root cause analyses the hollow particles were investigated and a model for particle genesis was developed. Based on these results further measures for the avoidance of particle formation were shown. The formation probability of similar hollow particles in biomass-fired fluidised-bed plants was assessed theoretically.

  1. Particle descending velocity near the wall of a rolling circulating fluidized bed

    Science.gov (United States)

    Zhao, Tong; Takei, Masahiro; Murata, Hiroyuki; Liu, Kai

    2014-04-01

    As part of the study to develop compact and efficient marine exhaust gas treatment system with circulating fluidized bed (CFB), effects of the swing motion of a ship on gas-solid flow in the CFB was investigated. The heat transfer efficiency of the CFB is closely related with the particle flow near the wall of riser. As a trial to evaluate the particle flow near the wall of riser quantitatively, descending velocity of particles at upright and swing condition was measured by a particle image velocimetry (PIV) system. Particle motion near the wall of riser was recorded through an observation window by a high speed camera. The recorded images were processed to evaluate the local descending velocity of particles under different swing amplitude and period. As results, the swing motion affects the down-flow of particles, namely, descending particle flow along the wall of riser. The time-averaged descending velocity near the wall of riser is remarkably decreased by the motion. Effect of the swing period on the particle descending velocity is really small. But as the swing amplitude increases, the descending velocity of particle decreased significantly.

  2. Dry particle generation with a 3-D printed fluidized bed generator

    Directory of Open Access Journals (Sweden)

    M. Roesch

    2017-06-01

    Full Text Available Here we describe the design and testing of PRIZE (PRinted fluidIZed bed gEnerator, a compact fluidized bed aerosol generator manufactured using stereolithography (SLA printing. Dispersing small quantities of powdered materials – due to either rarity or expense – is challenging due to a lack of small, low-cost dry aerosol generators. With this as motivation, we designed and built a generator that uses a mineral dust or other dry powder sample mixed with bronze beads that sit atop a porous screen. A particle-free airflow is introduced, dispersing the sample as airborne particles. Total particle number concentrations and size distributions were measured during different stages of the assembling process to show that the SLA 3-D printed generator did not generate particles until the mineral dust sample was introduced. Time-series measurements with Arizona Test Dust (ATD showed stable total particle number concentrations of 10–150 cm−3, depending on the sample mass, from the sub- to super-micrometer size range. Additional tests with collected soil dust samples are also presented. PRIZE is simple to assemble, easy to clean, inexpensive and deployable for laboratory and field studies that require dry particle generation.

  3. Dry particle generation with a 3-D printed fluidized bed generator

    Science.gov (United States)

    Roesch, Michael; Roesch, Carolin; Cziczo, Daniel J.

    2017-06-01

    Here we describe the design and testing of PRIZE (PRinted fluidIZed bed gEnerator), a compact fluidized bed aerosol generator manufactured using stereolithography (SLA) printing. Dispersing small quantities of powdered materials - due to either rarity or expense - is challenging due to a lack of small, low-cost dry aerosol generators. With this as motivation, we designed and built a generator that uses a mineral dust or other dry powder sample mixed with bronze beads that sit atop a porous screen. A particle-free airflow is introduced, dispersing the sample as airborne particles. Total particle number concentrations and size distributions were measured during different stages of the assembling process to show that the SLA 3-D printed generator did not generate particles until the mineral dust sample was introduced. Time-series measurements with Arizona Test Dust (ATD) showed stable total particle number concentrations of 10-150 cm-3, depending on the sample mass, from the sub- to super-micrometer size range. Additional tests with collected soil dust samples are also presented. PRIZE is simple to assemble, easy to clean, inexpensive and deployable for laboratory and field studies that require dry particle generation.

  4. Particle Dispersion Behaviors of Dense Gas-Particle Flows in Bubble Fluidized Bed

    Directory of Open Access Journals (Sweden)

    Sihao Lv

    2013-01-01

    Full Text Available An Euler-Euler two-fluid model incorporating a developed momentum transfer empirical coefficient is developed to study the particle dispersion behaviors of dense gas-particle flows in gas-fluidization reactor. In this model, the four-way couplings among gas-particles, particle-gas, and particle-particle collisions are fully considered based on kinetic theory of granular flows and an improved smooth continuous drag coefficient is utilized. Gas turbulent flow is solved by large eddy simulation. The particle fraction, the time-averaged axial particle velocity, the histogram of particle fluctuation velocity, and the wavelet analysis of pressure signals are obtained. The results are in good agreement with experimental measurements. The mean value and the variance of axial particle velocity are greater than those of radial particle velocities. Particle collision frequencies at bubble vibrant movement regions along axial direction are much higher than those of radial direction and attenuated along height increase. Low-frequency component of pressure signal indicating the bubble movement behaviors in the center of reactor is stronger than wall regions. Furthermore, the negative values represent the passed bubble and positive peak values disclose the continuous motion of single bubble.

  5. Particle size distribution of main-channel-bed sediments along the upper Mississippi River, USA

    Science.gov (United States)

    Remo, Jonathan W. F.; Heine, Reuben A.; Ickes, Brian S.

    2016-07-01

    In this study, we compared pre-lock-and-dam (ca. 1925) with a modern longitudinal survey of main-channel-bed sediments along a 740-km segment of the upper Mississippi River (UMR) between Davenport, IA, and Cairo, IL. This comparison was undertaken to gain a better understanding of how bed sediments are distributed longitudinally and to assess change since the completion of the UMR lock and dam navigation system and Missouri River dams (i.e., mid-twentieth century). The comparison of the historic and modern longitudinal bed sediment surveys showed similar bed sediment sizes and distributions along the study segment with the majority (> 90%) of bed sediment samples having a median diameter (D50) of fine to coarse sand. The fine tail (≤ D10) of the sediment size distributions was very fine to medium sand, and the coarse tail (≥ D90) of sediment-size distribution was coarse sand to gravel. Coarsest sediments in both surveys were found within or immediately downstream of bedrock-floored reaches. Statistical analysis revealed that the particle-size distributions between the survey samples were statistically identical, suggesting no overall difference in main-channel-bed sediment-size distribution between 1925 and present. This was a surprising result given the magnitude of river engineering undertaken along the study segment over the past ~ 90 years. The absence of substantial differences in main-channel-bed-sediment size suggests that flow competencies within the highly engineered navigation channel today are similar to conditions within the less-engineered historic channel.

  6. Particle size distribution of main-channel-bed sediments along the upper Mississippi River, USA

    Science.gov (United States)

    Remo, Jonathan; Heine, Ruben A.; Ickes, Brian

    2016-01-01

    In this study, we compared pre-lock-and-dam (ca. 1925) with a modern longitudinal survey of main-channel-bed sediments along a 740-km segment of the upper Mississippi River (UMR) between Davenport, IA, and Cairo, IL. This comparison was undertaken to gain a better understanding of how bed sediments are distributed longitudinally and to assess change since the completion of the UMR lock and dam navigation system and Missouri River dams (i.e., mid-twentieth century). The comparison of the historic and modern longitudinal bed sediment surveys showed similar bed sediment sizes and distributions along the study segment with the majority (> 90%) of bed sediment samples having a median diameter (D50) of fine to coarse sand. The fine tail (≤ D10) of the sediment size distributions was very fine to medium sand, and the coarse tail (≥ D90) of sediment-size distribution was coarse sand to gravel. Coarsest sediments in both surveys were found within or immediately downstream of bedrock-floored reaches. Statistical analysis revealed that the particle-size distributions between the survey samples were statistically identical, suggesting no overall difference in main-channel-bed sediment-size distribution between 1925 and present. This was a surprising result given the magnitude of river engineering undertaken along the study segment over the past ~ 90 years. The absence of substantial differences in main-channel-bed-sediment size suggests that flow competencies within the highly engineered navigation channel today are similar to conditions within the less-engineered historic channel.

  7. Development of methanogenic consortia in fluidized-bed batches using sepiolite of different particle size.

    Science.gov (United States)

    Sánchez, J M; Rodríguez, F; Valle, L; Muñoz, M A; Moriñigo, M A; Borrego, J J

    1996-09-01

    The addition of support materials, such as sepiolite, to fluidized-bed anaerobic digesters enhances the methane production by increasing the colonization by syntrophic microbiota. However, the efficiency in the methanogenesis depends on the particle size of the support material, the highest level of methane production being obtained by the smaller particle size sepiolite. Because of the porosity and physico-chemical characteristics of these support materials, the anaerobic microbial consortia formed quickly (after one week of incubation). The predominant methanogenic bacteria present in the active granules, detected both by immunofluorescence using specific antibodies and by scanning electron microscopy, were acetoclastic methanogens, mainly Methanosarcina and Methanosaeta.

  8. Experimental analysis of sand particles' lift-off and incident velocities in wind-blown sand flux

    Institute of Scientific and Technical Information of China (English)

    Li Xie; Zhibao Dong; Xiaojing Zheng

    2005-01-01

    The probability distributions of sand particles' lift-off and incident velocities in a wind-blown sand flux play very important roles in the simulation of the wind-blown sand movement. In this paper, the vertical and the horizontal speeds of sand particles located at 1.0 mm above a sand-bed in a wind-blown sand flux are observed with the aid of Phase Doppler Anemometry (PDA) in a wind tunnel. Based on the experimental data, the probability distributions of not only the vertical lift-off speed but also the lift-off velocity as well as its horizontal component and the incident velocity as well as its vertical and horizontal components can be obtained by the equal distance histogram method. It is found, according to the results of the χ2-test for these probability distributions, that the probability density functions (pdf's) of the sand particles' lift-off and incident velocities as well as their vertical components are described by the Gamma density function with different peak values and shapes and the downwind incident and lift-off horizontal speeds, respectively, can be described by the lognormal and the Gamma density functions. These pdf's depend on not only the sand particle diameter but also the wind speed.

  9. Particle concentration and flux dynamics in the atmospheric boundary layer as the indicator of formation mechanism

    DEFF Research Database (Denmark)

    Lauros, J.; Sogachev, Andrey; Smolander, S.

    2011-01-01

    We carried out column model simulations to study particle fluxes and deposition and to evaluate different particle formation mechanisms at a boreal forest site in Finland. We show that kinetic nucleation of sulphuric acid cannot be responsible for new particle formation alone as the simulated...

  10. Particle concentration and flux dynamics in the atmospheric boundary layer as the indicator of formation mechanism

    DEFF Research Database (Denmark)

    Lauros, J.; Sogachev, Andrey; Smolander, S.

    2010-01-01

    We carried out column model simulations to study particle fluxes and deposition and to evaluate different particle formation mechanisms at a boreal forest site in Finland. We show that kinetic nucleation of sulphuric acid cannot be responsible for new particle formation alone as the vertical...

  11. Gas-Solid Turbulent Flow in a Circulating Fluidized Bed Riser; Numerical Study of Binary Particle Mixtures

    NARCIS (Netherlands)

    He, Y.; Deen, N.G.; Sint Annaland, van M.; Kuipers, J.A.M.

    2008-01-01

    A numerical simulation was performed on a turbulent gas-particle multi-phase flow in a circulating fluidized bed riser based on a hard-sphere discrete particle model (DPM) for the particle phase and the Navier-Stokes equations for the gas phase. The sub-grid scale stresses (SGS) were modeled with th

  12. Three dimensional model for particle saltation close to stream beds, including a detailed description of the particle interaction with turbulence and inter-particle collisions

    KAUST Repository

    Moreno, Pablo M.

    2011-05-19

    We present in this paper a new three-dimensional (3-D) model for bed-load sediment transport, based on a Lagrangian description. We analyze generalized sub-models for the velocities after collision and the representation of the bed-roughness. The free-flight sub-model includes the effect of several forces, such as buoyancy, drag, virtual mass, lift, Basset and Magnus, and also addresses the particle rotation. A recent methodology for saving computational time in the Basset force is also employed. The sub-models for the post-collision velocity and rotation are based on the conservation of linear and angular momentum during the collision with the bed. We develop a new 3-D representation for the bed roughness by using geometric considerations. In order to address the interaction of particles with the turbulent flow, we tracked the particles through a computed turbulent velocity field for a smooth flat plate. This velocity field was used as a surrogate of the 3-D turbulent conditions close to the bed in streams. We first checked that the basic turbulence statistics for this velocity field could be used to approximate those in an open-channel flow. We then analyzed the interaction of the sediment and the turbulence for a single and multiple particles. We compared numerical results with experimental data obtained by Niño and García (1998b). We show that model predictions are in good agreement with existing data, in the sand size range. © 2011 ASCE.

  13. Drying of suspensions and solutions on inert particle surface in mechanically spouted bed dryer

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    To eliminate some disadvantages of the conventional spouted bed dryers the mechanically spouted bed (MSB) system was developed. This dryer type is convenient to use inert particles providing an increased surface area for drying of materials of high-moisture content and heat sensitive materials. On three different drying tasks are demonstrated the experimental optimization of process parameters to obtain products of demanded quality. The main object was at drying of AlO(OH) suspension to preserve the particle size under 2.5 μm and to obtain product with a moisture content of about 0.05 kg/kg (d.b.). For this reason a very thin particle coating and intensive abrasion had to be assured. At drying of tomato concentrates the thermoplasticity makes the process very difficult. To jump over the deliquescent and sticky state developed at the critical temperature-moisture content values a very short drying time (8-10 s) must be provided. The third task was to form powder-like product from bovine serum albumin (BSA) solution having very low solid content (2-4%). The selected process parameters given in this paper resulted in a mean particle size of less than 20 μm while the soluble preserved protein content was higher than 90%.

  14. Holdup and Flow Behavior of Fluidized Solid Particles in a Liquid-Solid Circulating Fluidized Bed

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Dae Ho; Lim, Ho; Jin, Hae Ryong; Kang, Yong [Chungnam National University, Daejeon (Korea, Republic of)

    2014-06-15

    Characteristics of holdup and flow behavior of fluidized solid particles were investigated in a liquid-solid circulating fluidized bed (0.102 m x 3.5 m). Effects of liquid velocity (U{sub L}), particle size (d{sub P}) and solid circulation rate (G{sub S}) on the solid holdup, overall particle rising velocity, slip velocity between liquid and particles and hydrodynamic energy dissipation rate in the riser were examined. The particle holdup increased with increasing d{sub P} or G{sub S} but decreased with increasing U{sub L}. The overall particle rising velocity increased with increasing U{sub L} or G{sub S} but decreased with increasing d{sub P}. The slip velocity increased with increasing U{sub L} or d{sub P} but did not change considerably with G{sub S}. The energy dissipation rate, which was found to be closely related to the contacting frequency of micro eddies, increased with increasing d{sub P}, G{sub S} or U{sub L}. The solid particle holdup was well correlated with operating variables such as U{sub L}, d{sub P} and G{sub S}.

  15. Group stability of bed particles near the critical threshold of motion

    Science.gov (United States)

    Simeonov, J.; Calantoni, J.

    2012-12-01

    The unsteady flow above a rough bed and its interaction with a group of mobile spherical particles is investigated with Direct Numerical Simulations. The velocity and pressure are resolved at sub-particle scales using a new Cartesian grid method based on a discontinuous extension of the pressure Poisson equation across particle boundaries. The hydrodynamics is fully resolved everywhere except in the gap between colliding particles when the latter becomes smaller than the grid step. The particle hydrodynamic forces are determined as a combination of the numerically resolved pressure/shear outside the gap and an analytical contribution for the unresolved gap dynamics. Theoretical Stokes flow models are used to estimate the unresolved lubrication pressure/shear force in the subgrid gap. For the mechanical contact, we use a soft-sphere approach where the normal and tangential forces are modeled using a linear elastic-plastic law and a history dependent friction law, respectively. The proposed collision model is validated against experimental data for normal and oblique immersed collisions of spherical particles. We find that the lubrication corrections for the unresolved gap flow are essential to correctly predict the observed decrease in the coefficient of restitution with decreasing collisional Stokes number including the value of the critical Stokes number where collisions cease to rebound. The low collisional Stokes number effects are important for dissipating the momentum of flow-induced vibrations of surface particles. The results from our numerical simulations for the initiation of motion are compared with existing laboratory data.

  16. Particle concentration and flux dynamics in the atmospheric boundary layer as the indicator of formation mechanism

    Directory of Open Access Journals (Sweden)

    J. Lauros

    2010-08-01

    Full Text Available We carried out column model simulations to study particle fluxes and deposition and to evaluate different particle formation mechanisms at a boreal forest site in Finland. We show that kinetic nucleation of sulphuric acid cannot be responsible for new particle formation alone as the vertical profile of particle number distribution does not correspond to observations. Instead organic induced nucleation leads to good agreement confirming the relevance of the aerosol formation mechanism including organic compounds emitted by biosphere.

    Simulation of aerosol concentration inside the atmospheric boundary layer during nucleation days shows highly dynamical picture, where particle formation is coupled with chemistry and turbulent transport. We have demonstrated suitability of our turbulent mixing scheme in reproducing most important characteristics of particle dynamics inside the atmospheric boundary layer. Deposition and particle flux simulations show that deposition affects noticeably only the smallest particles at the lowest part of the atmospheric boundary layer.

  17. DETERMINATION OF PARTICLE DENSITY BY MERCURY POROSIMETRY FOR BIOMASS FLUID DYNAMIC STUDY IN MOVING BEDS

    Directory of Open Access Journals (Sweden)

    Juan F. Saldarriaga

    2014-06-01

    Full Text Available Determination of the particle density is required to address the hydrodynamic study of a moving bed contactor. The measurement of this parameter is complicated when particles are irregularly shaped. In this study, two different techniques were use: compaction by mechanical compression and an alternative proposal, which contemplates the potential of mercury porosimetry for determining the surface and structural properties. It was observed that the results obtained by compacting in all cases are higher than expected. However, the values obtained by mercury porosimetry are more consistent with expected values. For example in the sawdust valued at 500kg/m3, very similar to the value of the original wood (502kg/m3. Values obtained by this procedure adequately represent the relationship between mass and volume of the particle and therefore are valid for hydrodynamic characterization of the biomass.

  18. Heat transfer from a horizontal finned tube bundle in bubbling fluidized beds of small and large particles

    Energy Technology Data Exchange (ETDEWEB)

    Devaru, C.B. [Jayachamaraja College of Engineering, Mysore (India). Dept. of Mechanical Engineering; Kolar, A.K. [Indian Inst. of Technology, Madras (India). Dept. of Mechanical Engineering

    1995-12-31

    Steady state average heat transfer coefficient measurements were made by the local thermal simulation technique in a cold, square, bubbling air-fluidized bed (0.305 m x 0.305 m) with immersed horizontal finned tube bundles (in-line and staggered) with integral 60{degree} V-thread. Studies were conducted using beds of small (average particle diameter less than 1 mm) sand particles and of large (average particle diameter greater thin 1 mm) particles (raagi, mustard, millet and coriander). The fin pitch varied from 0.8 to 5.0 mm and the fin height varied from 0.69 to 4.4 mm. The tube pitch ratios used were 1.75 and 3.5. The influence of bed particle diameter, fluidizing velocity, fin pitch, and tube pitch ratio on average heat transfer coefficient was studied. Fin pitch and bed particle diameter are the most significant parameters affecting heat transfer coefficient within the range of experimental conditions. Bed pressure drop depends only on static bed height. New direct correlations, incorporating easily measurable quantities, for average heat transfer coefficient for finned tube bundles (in-line and staggered) are proposed.

  19. Particle-based simulations of powder coating in additive manufacturing suggest increase in powder bed roughness with coating speed

    Directory of Open Access Journals (Sweden)

    Parteli Eric J. R.

    2017-01-01

    Full Text Available We have developed the first particle-based numerical tool to simulate the coating of powder particles in additive manufacturing devices. Our Discrete Element Method considers realistic particle shapes and incorporates attractive interaction (van-der-Waals forces between the particles. From simulations of powder coating using a roller as coating device, we find that the surface roughness of the powder bed scales with the square of coating speed. Moreover, we find that using fine, highly polydisperse powders may lead to larger powder bed roughness, compared to process simulations using coarser powders, due to the formation of agglomerates resulting from cohesive forces.

  20. Particle-based simulations of powder coating in additive manufacturing suggest increase in powder bed roughness with coating speed

    Science.gov (United States)

    Parteli, Eric J. R.; Pöschel, Thorsten

    2017-06-01

    We have developed the first particle-based numerical tool to simulate the coating of powder particles in additive manufacturing devices. Our Discrete Element Method considers realistic particle shapes and incorporates attractive interaction (van-der-Waals) forces between the particles. From simulations of powder coating using a roller as coating device, we find that the surface roughness of the powder bed scales with the square of coating speed. Moreover, we find that using fine, highly polydisperse powders may lead to larger powder bed roughness, compared to process simulations using coarser powders, due to the formation of agglomerates resulting from cohesive forces.

  1. Landau Damping of Transverse Waves in the Exosphere by Fast Particle Fluxes

    Science.gov (United States)

    Tidman, D. A.; Jaggi, R. K.

    1962-01-01

    We have investigated the Landau damping of transverse waves propagating in the thermal exospheric plasma, by fast particle fluxes which also exist in these regions. The most intense non-thermal fluxes so far detected are those of the auroral producing electrons and protons measured by McIlwain. We find that these fluxes may considerably damp the propagation of whistler modes through some regions. The damping of hydromagnetic waves in the exosphere by this mechanism is negligible.

  2. Influence of particle flux density and temperature on surface modifications of tungsten and deuterium retention

    NARCIS (Netherlands)

    Buzi, L.; De Temmerman, G.; Unterberg, B.; M. Reinhart,; Litnovsky, A.; Philipps, V.; Van Oost, G.; Möller, S.

    2014-01-01

    Systematic study of deuterium irradiation effects on tungsten was done under ITER - relevant high particle flux density, scanning a broad surface temperature range. Polycrystalline ITER - like grade tungsten samples were exposed in linear plasma devices to two different ranges of deuterium ion flux

  3. Two-flux method for radiation heat transfer in anisotropic gas-particles media

    Institute of Scientific and Technical Information of China (English)

    WANG Fei; CEN Kefa; T. Girasole; A. Garo; G. Gréhan; YAN Jianhua

    2004-01-01

    Two-flux method can be used, as a simplification for the radiative heat transfer, to predict heat flux in a slab consisting of gas and particles. In the original two-flux method (Schuster, 1905 and Schwarzschild, 1906), the radiation field was assumed to be isotropic. But for gas-particles mixture in combustion environments, the scatterings of particles are usually anisotropic, and the original two-flux method gives critical errors when ignoring this anisotropy. In the present paper, a multilayer four-flux model developed by Rozé et al. (2001) is extended to calculate the radiation heat flux in a slab containing participating particles and gas mixture. The analytic resolution of the radiative transfer equation in the framework of a two-flux approach is presented. The average crossing parameter ε And the forward scattering ratio ζ are defined to describe the anisotropy of the radiative field. To validate the model, the radiation transfer in a slab has been computed. Comparisons with the exact analytical result of Modest (1993) and the original two-flux model show the exactness and the improvement. The emissivity of a slab containing flyash/CO2/H2O mixture is obtained using the new model. The result is identical with that of Goodwin (1989).

  4. A mechanistic particle flux model applied to the oceanic phosphorus cycle

    Directory of Open Access Journals (Sweden)

    T. DeVries

    2014-03-01

    Full Text Available The sinking and decomposition of particulate organic matter are critical processes in the ocean's biological pump, but are poorly understood and crudely represented in biogeochemical models. Here we present a mechanistic model for particle fluxes in the ocean that solves the evolution of the particle size distribution with depth. The model can represent a wide range of particle flux profiles, depending on the surface particle size distribution, the relationships between particle size, mass and velocity, and the rate of particle mass loss during decomposition. Spatially variable flux profiles are embedded in a data-constrained ocean circulation model, where the most uncertain parameters governing particle dynamics are tuned to achieve an optimal fit to the global distribution of phosphate. The resolution of spatially variable particle sizes has a significant effect on modeled organic matter production rates, increasing production in oligotrophic regions and decreasing production in eutrophic regions compared to a model that assumes spatially uniform particle sizes and sinking fluxes. The mechanistic particle model can reproduce global nutrient distributions better than, and sediment trap fluxes as well as, other commonly used empirical formulas. However, these independent data constraints cannot be simultaneously matched in a closed P budget commonly assumed in ocean models. Through a systematic addition of model processes, we show that the apparent discrepancy between particle flux and nutrient data can be resolved through P burial, but only if that burial is associated with a slowly decaying component of organic matter as might be achieved through protection by ballast minerals. Moreover, the model solution that best matches both datasets requires a larger rate of P burial (and compensating inputs than have been previously estimated. Our results imply a marine PO4 inventory with a residence time of a few thousand years, similar to that of the

  5. Modeling the temperature in coal char particle during fluidized bed combustion

    Energy Technology Data Exchange (ETDEWEB)

    Vasilije Manovic; Mirko Komatina; Simeon Oka [University of Belgrade, Belgrade (Serbia)

    2008-05-15

    The temperatures of a coal char particle in hot bubbling fluidized bed (FB) were analyzed by a model of combustion. The unsteady model includes phenomena of heat and mass transfer through a porous char particle, as well as heterogeneous reaction at the interior char surface and homogeneous reaction in the pores. The parametric analysis of the model has shown that above 550{sup o}C combustion occurs under the regime limited by diffusion. The experimental results of temperature measurements by thermocouple in the particle center during FB combustion at temperatures in the range 590-710{sup o}C were compared with the model predictions. Two coals of different rank were used: lignite and brown coal, with particle size in the range 5-10 mm. The comparisons have shown that the model can adequately predict the histories of temperatures in char particles during combustion in FB. In the first order, the model predicts the influence of the particle size, coal rank (via porosity), and oxygen concentration in its surroundings. 53 refs., 6 figs., 2 tabs.

  6. Stress Analysis of Coated Particle Fuel in the Deep-Burn Pebble Bed Reactor Design

    Energy Technology Data Exchange (ETDEWEB)

    B. Boer; A. M. Ougouag

    2010-05-01

    High fuel temperatures and resulting fuel particle coating stresses can be expected in a Pu and minor actinide fueled Pebble Bed Modular Reactor (400 MWth) design as compared to the ’standard’ UO2 fueled core. The high discharge burnup aimed for in this Deep-Burn design results in increased power and temperature peaking in the pebble bed near the inner and outer reflector. Furthermore, the pebble power in a multi-pass in-core pebble recycling scheme is relatively high for pebbles that make their first core pass. This might result in an increase of the mechanical failure of the coatings, which serve as the containment of radioactive fission products in the PBMR design. To investigate the integrity of the particle fuel coatings as a function of the irradiation time (i.e. burnup), core position and during a Loss Of Forced Cooling (LOFC) incident the PArticle STress Analysis code (PASTA) has been coupled to the PEBBED code for neutronics, thermal-hydraulics and depletion analysis of the core. Two deep burn fuel types (Pu with or without initial MA fuel content) have been investigated with the new code system for normal and transient conditions including the effect of the statistical variation of thickness of the coating layers.

  7. Statistics of F-theory flux vacua for particle physics

    Energy Technology Data Exchange (ETDEWEB)

    Watari, Taizan [Kavli Institute for the Physics and Mathematics of the Universe,University of Tokyo, Kashiwa-no-ha 5-1-5, 277-8583 (Japan)

    2015-11-10

    Supersymmetric flux compactification of F-theory in the geometric phase yields numerous vacua, and provides an ensemble of low-energy effective theories with a variety of symmetry, matter multiplicity and Lagrangian parameters. Theoretical tools have already been developed so that we can study how the statistics of those flux vacua depend on the choice of symmetry and some of the Lagrangian parameters. In this article, we estimate the fraction of i) vacua that have a U(1) symmetry for spontaneous R-parity violation, and ii) those that realise ideas which achieve hierarchical eigenvalues of the Yukawa matrices. We also learn a lesson that the number of flux vacua is reduced very much when the unbroken U(1){sub Y} symmetry is obtained from a non-trivial Mordell-Weil group, while it is not, when U(1){sub Y} is in SU(5) unification. It also turns out to be likely that vacua with an approximate U(1) symmetry form a locus of accumulation points of the flux vacua distribution.

  8. Size-resolved flux measurement of sub-micrometer particles over an urban area

    Directory of Open Access Journals (Sweden)

    Malte Julian Deventer

    2013-12-01

    Full Text Available From April 11th to May 27th, 2011, the turbulent exchange of sub-micrometer particles between the urban surface and the urban boundary-layer was measured above the city area of Münster (NW Germany. The scope of the study is to examine the contributions of particles of different size classes to the total measured fluxes. Eddy-covariance measurements were performed at 65 m above ground. The particle concentrations in 99 size bins with particle diameters ranging from 55 to 1000 nm were measured with an optical particle spectrometer. For flux calculations we grouped these 99 original bins into 18 wider channels with an upper cut-off of 320 nm, and a further rather coarse channel for particles up to 1 ?m. The overall results reveal that Münster is a relevant source of about 2.8 · 108 particles m?2 d?1 on weekdays and 1.8 · 108 particles m?2 d?1 on Sundays within the indicated size range. These emissions are predominantly driven by secondary particles of the Aitken mode, which are most likely caused by traffic. Hence traffic hotspots are a major contribution to the net fluxes. On the other hand, considering the mass fluxes, Münster is a sink of 0.53 ?g m?2 d?1 on weekdays and 0.08 ?g m?2 d?1 on Sundays. Here, mainly particles of the accumulation mode with diameters above 167 nm lead to deposition fluxes. Number and mass fluxes exhibit distinct daily and weekly patterns.

  9. Numerical study of cavitation and pinning effects due to gas injection through a bed of particles: application to a radial-flow moving-bed reactor

    Science.gov (United States)

    Vinay, Guillaume; Vasquez, Felaurys; Richard, Florence; Applied Mechanics Team

    2016-11-01

    In the petroleum and chemical industries, radial-flow moving-bed reactors are used to carry out chemical reactions such as catalytic reforming. Radial-flow reactors provide high capacity without increased pressure drop or greatly increased vessel dimensions. This is done by holding the catalyst in a basket forming an annular bed, and causing the gas to flow radially between the outer annulus and the central tube. Catalyst enter the top of the reactor, move through the vessel by gravity to the bottom where it is removed and then regenerated. Within the catalytic bed, the combined effects of particles motion and radial injection of the gas may lead to cavitation and pinning phenomenon that may clearly damage the reactor. We study both cavitation and pinning effects using an in-house numerical software, named PeliGRIFF (www.peligriff.com/), designed to simulate particulate flows at different scales; from the particle scale, where fluid/particle interactions are directly solved, to the particles suspension scale where the fluid/solid interactions are modeled. In the past, theoretical and experimental studies have already been conducted in order to understand the way cavitation and pinning occur. Here, we performed simulations involving a few thousands of particles aiming at reproducing experimental experiments. We will present comparisons between our numerical results and experimental results in terms of pressure drop, velocity, porosity.

  10. Dynamics of particle loading in deep-bed filter. Transport, deposition and reentrainment

    Directory of Open Access Journals (Sweden)

    Przekop Rafał

    2016-09-01

    Full Text Available Deep bed filtration is an effective method of submicron and micron particle removal from the fluid stream. There is an extensive body of literature regarding particle deposition in filters, often using the classical continuum approach. However, the approach is not convenient for studying the influence of particle deposition on filter performance (filtration efficiency, pressure drop when non-steady state boundary conditions have to be introduced. For the purposes of this work the lattice-Boltzmann model describes fluid dynamics, while the solid particle motion is modeled by the Brownian dynamics. For aggregates the effect of their structure on displacement is taken into account. The possibility of particles rebound from the surface of collector or reentrainment of deposits to fluid stream is calculated by energy balanced oscillatory model derived from adhesion theory. The results show the evolution of filtration efficiency and pressure drop of filters with different internal structure described by the size of pores. The size of resuspended aggregates and volume distribution of deposits in filter were also analyzed. The model enables prediction of dynamic filter behavior. It can be a very useful tool for designing filter structures which optimize maximum lifetime with the acceptable values of filtration efficiency and pressure drop.

  11. Heated submicron particle fluxes using an optical particle counter in urban environment

    Science.gov (United States)

    Vogt, M.; Johansson, C.; Mårtensson, M.; Struthers, H.; Ahlm, L.; Nilsson, D.

    2013-03-01

    From May 2008 to March 2009 aerosol emissions were measured using the eddy covariance method covering the size range 0.25 to 2.5 μm diameter (Dp) from a 105 m tower, in central Stockholm, Sweden. Supporting chemical aerosol data were collected at roof and street level. Results show that the inorganic fraction of sulfate, nitrate, ammonium and sea salt accounts for approximately 15% of the total aerosol mass traffic (as inferred from the ratio of the incremental concentrations of nitrogen oxides (NOx) and BC measured on a densely trafficked street) and the fluxes of non-volatile material at tower level are in close agreement, suggesting a traffic source of BC. We have estimated the emission factors (EFs) for non-volatile particles traffic activity data. Light (LDV) and heavy duty vehicle (HDV) EFs were estimated using multiple linear regression and reveal that for non-volatile particulate matter in the 0.25 to 0.6 μm Dp range, the EFHDV is approximately twice as high as the EFLDV, the difference not being statistically significant.

  12. Influence of temperature and particle size on the fixed bed pyrolysis of orange peel residues

    Energy Technology Data Exchange (ETDEWEB)

    Aguiar, L. [Departamento de Mecanica, Universidad de Pinar del Rio, Cuba. Calle Marti 270, final, Pinar del Rio (Cuba); Marquez-Montesinos, F. [Departamento de Quimica, Universidad de Pinar del Rio, Cuba. Calle Marti 270, final, Pinar del Rio (Cuba); Gonzalo, A.; Sanchez, J.L.; Arauzo, J. [Thermochemical Processes Group (GPT), Aragon Institute for Engineering Research (I3A), University of Zaragoza, Maria de Luna 3, 50018 Zaragoza (Spain)

    2008-09-15

    Orange peel is a residue from the production of juice. Its energetic valorisation could be interesting in areas where a different use, such as animal feed, is not possible. In order to investigate the viability of energy recovery, the pyrolysis of orange peel residues was studied in a fixed bed reactor, as an initial assessment of this process. The influence of pyrolysis temperature (300-600 C) and particle size (d{sub p}<300{mu}m and d{sub p}>800{mu}m) on product distribution, gas composition and char heating value has been investigated using a factorial design of experiments. Gas, char and water are the main products obtained; tar is only about 6 wt.% of the initial residue. Temperature was found to be the parameter which exerts a more important influence on the results than particle size. (author)

  13. FLASH PYROLYSIS OF BIOMASS PARTICLES IN FLUIDIZED BED FOR BIO-OIL PRODUCTION

    Institute of Scientific and Technical Information of China (English)

    Shurong Wang; Mengxiang Fang; Chunjiang Yu; Zhongyang Luo; Kefa Cen

    2005-01-01

    Biomass utilization could relieve the pressure caused by conventional energy shortage and environmental pollution. Advantage should be taken of the abundant biomass in China as clean energy source to substitute for traditional fossil fuels. At present, flash pyrolysis appears to be an efficient method to produce high yields of liquids that could either be directly used as fuel or converted to other valuable chemicals. Experiments were carried out of pyrolyzing biomass particles in a hot dense fluidized bed of sand to obtain high-quality bio-oil. Among four kinds of biomass species adopted in our experiment, Padauk Wood had the best characteristics in producing bio-oil. GC-MS analysis showed bio-oil to be a complex mixture consisting of many compounds. Furthermore, an integrated model was proposed to reveal how temperature influences biomass pyrolysis. Computation indicated that biomass particles underwent rapid heating before pyrolysis.

  14. Effect of pressure on gas-solid flow behavior in dense gas-fluidised beds: a discrete particle simulation study

    NARCIS (Netherlands)

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

    2002-01-01

    A computational study has been carried out to assess the influence of pressure on the flow structures and regime transitions in dense gas-fluidized beds using the discrete particle simulation (DPS) approach. By employing particle level simulation, the particle–particle–fluid interactions were analyz

  15. Visualization of particle flux in the human body on the surface of Mars

    Science.gov (United States)

    Saganti, Premkumar B.; Cucinotta, Francis A.; Wilson, John W.; Schimmerling, Walter

    2002-01-01

    For a given galactic cosmic ray (GCR) environment, information on the particle flux of protons, alpha particles, and heavy ions, that varies with respect to the topographical altitude on the Martian surface, are needed for planning exploration missions to Mars. The Mars Global Surveyor (MGS) mission with its Mars Orbiter Laser Altimeter (MOLA) instrument has been providing precise topographical surface map of the Mars. With this topographical data, the particle flux at the Martian surface level through the CO2 atmospheric shielding for solar minimum and solar maximum conditions are calculated. These particle flux calculations are then transported first through an anticipated shielding of a conceptual shelter with several water equivalent shield values (up to 50 g/cm2 of water in steps of 5 g/cm2) considered to represent a surface habitat, and then into the human body. Model calculations are accomplished utilizing the HZETRN, QMSFRG, and SUM-MARS codes. Particle flux calculations for 12 different locations in the human body were considered from skin depth to the internal organs including the blood-forming organs (BFO). Visualization of particle flux in the human body at different altitudes on the Martian surface behind a known shielding is anticipated to provide guidance for assessing radiation environment risk on the Martian surface for future human missions.

  16. Effects of process parameters on solid self-microemulsifying particles in a laboratory scale fluid bed.

    Science.gov (United States)

    Mukherjee, Tusharmouli; Plakogiannis, Fotios M

    2012-01-01

    The purpose of this study was to select the critical process parameters of the fluid bed processes impacting the quality attribute of a solid self-microemulsifying (SME) system of albendazole (ABZ). A fractional factorial design (2(4-1)) with four parameters (spray rate, inlet air temperature, inlet air flow, and atomization air pressure) was created by MINITAB software. Batches were manufactured in a laboratory top-spray fluid bed at 625-g scale. Loss on drying (LOD) samples were taken throughout each batch to build the entire moisture profiles. All dried granulation were sieved using mesh 20 and analyzed for particle size distribution (PSD), morphology, density, and flow. It was found that as spray rate increased, sauter-mean diameter (D(s)) also increased. The effect of inlet air temperature on the peak moisture which is directly related to the mean particle size was found to be significant. There were two-way interactions between studied process parameters. The main effects of inlet air flow rate and atomization air pressure could not be found as the data were inconclusive. The partial least square (PLS) regression model was found significant (P < 0.01) and predictive for optimization. This study established a design space for the parameters for solid SME manufacturing process.

  17. Signatures of Energy Flux in Particle Production: A Black Hole Birth Cry and Death Gasp

    CERN Document Server

    Good, Michael R R

    2015-01-01

    It is recently argued that if the Hawking radiation process is unitary, then a black hole's mass cannot be monotonically decreasing. We examine the time dependent particle count and negative energy flux in the non-trivial conformal vacuum via the moving mirror approach. A new, exactly unitary solution is presented which emits a characteristic above-thermal positive energy burst, a thermal plateau, and negative energy flux. It is found that the characteristic positive energy flare and thermal plateau is observed in the particle outflow. However, the results of time dependent particle production show no overt indication of negative energy flux. Therefore, a black hole's birth cry is detectable by asymptotic observers via particle count, whereas its death gasp is not.

  18. Signatures of energy flux in particle production: a black hole birth cry and death gasp

    Science.gov (United States)

    Good, Michael R. R.; Ong, Yen Chin

    2015-07-01

    It is recently argued that if the Hawking radiation process is unitary, then a black hole's mass cannot be monotonically decreasing. We examine the time dependent particle count and negative energy flux in the non-trivial conformal vacuum via the moving mirror approach. A new, exactly unitary solution is presented which emits a characteristic above-thermal positive energy burst, a thermal plateau, and negative energy flux. It is found that the characteristic positive energy flare and thermal plateau is observed in the particle outflow. However, the results of time dependent particle production show no overt indication of negative energy flux. Therefore, a black hole's birth cry is detectable by asymptotic observers via particle count, whereas its death gasp is not.

  19. Signatures of energy flux in particle production: a black hole birth cry and death gasp

    Energy Technology Data Exchange (ETDEWEB)

    Good, Michael R.R. [Department of Physics, Nazarbayev University,53 Kabanbay Batyr Ave., Astana, Republic of (Kazakhstan); Ong, Yen Chin [Nordic Institute for Theoretical Physics, KTH Royal Institute of Technology Stockholm University,Roslagstullsbacken 23, SE-106 91 Stockholm (Sweden)

    2015-07-27

    It is recently argued that if the Hawking radiation process is unitary, then a black hole’s mass cannot be monotonically decreasing. We examine the time dependent particle count and negative energy flux in the non-trivial conformal vacuum via the moving mirror approach. A new, exactly unitary solution is presented which emits a characteristic above-thermal positive energy burst, a thermal plateau, and negative energy flux. It is found that the characteristic positive energy flare and thermal plateau is observed in the particle outflow. However, the results of time dependent particle production show no overt indication of negative energy flux. Therefore, a black hole’s birth cry is detectable by asymptotic observers via particle count, whereas its death gasp is not.

  20. Simultaneous estimation of bidirectional particle flow and relative flux using MUSIC-OCT: phantom studies

    Science.gov (United States)

    Yousefi, Siavash; Wang, Ruikang K.

    2014-11-01

    In an optical coherence tomography (OCT) scan from a living tissue, red blood cells (RBCs) are the major source of backscattering signal from moving particles within microcirculatory system. Measuring the concentration and velocity of RBC particles allows assessment of RBC flux and flow, respectively, to assess tissue perfusion and oxygen/nutrition exchange rates within micro-structures. In this paper, we propose utilizing spectral estimation techniques to simultaneously quantify bi-directional particle flow and relative flux by spectral estimation of the received OCT signal from moving particles within capillary tubes embedded in tissue mimicking phantoms. The proposed method can be directly utilized for in vivo quantification of capillaries and microvessels. Compared to the existing methods in the literature that can either quantify flow direction or power, our proposed method allows simultaneous flow (velocity) direction and relative flux (power) estimation.

  1. The causal relation between turbulent particle flux and density gradient

    Energy Technology Data Exchange (ETDEWEB)

    Milligen, B. Ph. van; Martín de Aguilera, A.; Hidalgo, C. [CIEMAT - Laboratorio Nacional de Fusión, Avda. Complutense 40, 28040 Madrid (Spain); Carreras, B. A. [BACV Solutions, 110 Mohawk Road, Oak Ridge, Tennessee 37830 (United States); García, L.; Nicolau, J. H. [Universidad Carlos III, 28911 Leganés, Madrid (Spain)

    2016-07-15

    A technique for detecting the causal relationship between fluctuating signals is used to investigate the relation between flux and gradient in fusion plasmas. Both a resistive pressure gradient driven turbulence model and experimental Langmuir probe data from the TJ-II stellarator are studied. It is found that the maximum influence occurs at a finite time lag (non-instantaneous response) and that quasi-periodicities exist. Furthermore, the model results show very long range radial influences, extending over most of the investigated regions, possibly related to coupling effects associated with plasma self-organization. These results clearly show that transport in fusion plasmas is not local and instantaneous, as is sometimes assumed.

  2. Multispecies Density and Temperature Gradient Dependence of Quasilinear Particle and Energy Fluxes

    Energy Technology Data Exchange (ETDEWEB)

    G. Rewoldt; R.V. Budny; W.M. Tang

    2004-08-09

    The variations of the normalized quasilinear particle and energy fluxes with artificial changes in the density and temperature gradients, as well as the variations of the linear growth rates and real frequencies, for ion temperature gradient and trapped-electron modes, are calculated. The quasilinear fluxes are normalized to the total energy flux, summed over all species. Here, realistic cases for tokamaks and spherical torii are considered which have two impurity species. For situations where there are substantial changes in the normalized fluxes, the ''diffusive approximation,'' in which the normalized fluxes are taken to be linear in the gradients, is seen to be inaccurate. Even in the case of small artificial changes in density or temperature gradients, changes in the fluxes of different species (''off-diagonal'') generally are significant, or even dominant, compared to those for the same species (''diagonal'').

  3. Particle Filter-Based Recursive Data Fusion With Sensor Indexing for Large Core Neutron Flux Estimation

    Science.gov (United States)

    Tamboli, Prakash Kumar; Duttagupta, Siddhartha P.; Roy, Kallol

    2017-06-01

    We introduce a sequential importance sampling particle filter (PF)-based multisensor multivariate nonlinear estimator for estimating the in-core neutron flux distribution for pressurized heavy water reactor core. Many critical applications such as reactor protection and control rely upon neutron flux information, and thus their reliability is of utmost importance. The point kinetic model based on neutron transport conveniently explains the dynamics of nuclear reactor. The neutron flux in the large core loosely coupled reactor is sensed by multiple sensors measuring point fluxes located at various locations inside the reactor core. The flux values are coupled to each other through diffusion equation. The coupling facilitates redundancy in the information. It is shown that multiple independent data about the localized flux can be fused together to enhance the estimation accuracy to a great extent. We also propose the sensor anomaly handling feature in multisensor PF to maintain the estimation process even when the sensor is faulty or generates data anomaly.

  4. An investigation into the fluidization and heat transfer of low density particles in a fluidized bed with applications

    Science.gov (United States)

    Modlin, J. M.

    1985-05-01

    The lack of reliable data on the fluidization and heat transfer characteristics of low density particles in a fluidized bed has prompted an experimental and analytical investigation into this subject. Seven groups of particles ranging in diameter from 0.25 mm to 2.0 mm and density from 2.5 to 32 pcf have been successfully fluidized and shown to be generally well predicted by classical fluidization and fluidized bed heat transfer theory. Two other groups of particles, also in this approximate range of particle diameter and density, are, however, unable to be fluidized due to significant inter-particle and static electric attractions. Using the experimental data and results as a basis of analysis, two application of low density particle fluidization in a building efficient energy management program are discussed. A fluidized bed can be incorporated into the wall cavity of a building for use as either a collector of solar energy or as a heat exchange medium in a building space heating/cooling program. As a solar collector, it is shown that the low density particle fluidized bed would thermally perform between comparable conventional liquid and air-cooled flat plate solar collectors. It would require less water pumping power and plumbing than the liquid collector and less air pumping power than the air collector.

  5. Performance of fluidized bed bioreactor containing wire-mesh sponge particles in wastewater treatment

    Energy Technology Data Exchange (ETDEWEB)

    Kargi, F.; Karapinar, I. [Dokuz Eyluel Univ., Izmir (Turkey). Dept. of Environmental Engineering

    1997-12-31

    Synthetic wastewater treatment performance of a continuous-flow, fluidized bed bioreactor was investigated at different particle number densities. Porous-sponge particles surrounded by steel wires were used as support material. COD removal rate and efficiency increased from r = 1,150 mg l{sup {minus}1} h{sup {minus}1} and E = 68% to r = 1,400 mg l{sup {minus}1} h{sup {minus}1} and E = 96% when particle number density (PND) increased from PND = 551{sup {minus}1} to PND = 4,401l{sup {minus}1} at a constant hydraulic residence time (HRT) of 9 h. The system`s performance was also evaluated at different hydraulic residence times ({Theta}{sub H} = 3--9 h) with a high particle number density of PND = 6,701{sup {minus}1}. Synthetic wastewater used throughout the studies consisted of diluted molasses, urea, K{sub 2}HPO{sub 4} and MgSO{sub 4} resulting in a ratio of COD/N/P = 100/10/1. Zooglea ramigera was the dominant microorganism in the FBBR. Apparent Monod kinetic constants of the system were determined as r{sub m} = 1,250 mg l{sup {minus}1} h{sup {minus}1} and K{sub s} = 1,150 mg l{sup {minus}1} by using the experimental data for PND = 6,701{sup {minus}1}.

  6. Deposition flux of aerosol particles and 15 polycyclic aromatic hydrocarbons in the North China Plain.

    Science.gov (United States)

    Wang, Xilong; Liu, Shuzhen; Zhao, Jingyu; Zuo, Qian; Liu, Wenxin; Li, Bengang; Tao, Shu

    2014-04-01

    The present study examined deposition fluxes of aerosol particles and 15 polycyclic aromatic hydrocarbons (PAHs) associated with the particles in the North China Plain. The annual mean deposition fluxes of aerosol particles and 15 PAHs were 0.69 ± 0.46 g/(m(2) ×d) and 8.5 ± 6.2 μg/(m(2) ×d), respectively. Phenanthrene, fluoranthene, pyrene, chrysene, benzo[b]fluoranthene, and benzo[k]fluoranthene were the dominant PAHs bound to deposited aerosol particles throughout the year. The total concentration of 15 PAHs in the deposited aerosol particles was the highest in winter but lowest in spring. The highest PAH concentration in the deposited aerosol particles in winter was because the heating processes highly increased the concentration in atmospheric aerosol particles. Low temperature and weak sunshine in winter reduced the degradation rate of deposited aerosol particle-bound PAHs, especially for those with low molecular weight. The lowest PAH concentration in deposited aerosol particles in spring resulted from the frequently occurring dust storms, which diluted PAH concentrations. The mean deposition flux of PAHs with aerosol particles in winter (16 μg/[m(2) ×d]) reached 3 times to 5 times that in other seasons (3.5-5.0 μg/[m(2) ×d]). The spatial variation of the deposition flux of PAHs with high molecular weight (e.g., benzo[a]pyrene) was consistent with their concentrations in the atmospheric aerosol particles, whereas such a phenomenon was not observed for those with low molecular weight (e.g., phenanthrene) because of their distinct hydrophobicity, Henry's law constant, and the spatially heterogeneous meteorological conditions.

  7. Numerical Simulation of Particle Flow Motion in a Two-Dimensional Modular Pebble-Bed Reactor with Discrete Element Method

    OpenAIRE

    Guodong Liu; Yining Zhang; Huilin Lu; Ersheng You; Xiang Li

    2013-01-01

    Modular pebble-bed nuclear reactor (MPBNR) technology is promising due to its attractive features such as high fuel performance and inherent safety. Particle motion of fuel and graphite pebbles is highly associated with the performance of pebbled-bed modular nuclear reactor. To understand the mechanism of pebble’s motion in the reactor, we numerically studied the influence of number ratio of fuel and graphite pebbles, funnel angle of the reactor, height of guide ring on the distribution of pe...

  8. Particle Acceleration At Small-Scale Flux Ropes In The Heliosphere

    Science.gov (United States)

    Zank, G. P.; Hunana, P.; Mostafavi, P.; le Roux, J. A.; Li, G.; Webb, G. M.; Khabarova, O.; Cummings, A. C.; Stone, E. C.; Decker, R. B.

    2015-12-01

    An emerging paradigm for the dissipation of magnetic turbulence in the supersonic solar wind is via localized small-scale reconnection processes, essentially between quasi-2D interacting magnetic islands or flux roped. Charged particles trapped in merging magnetic islands can be accelerated by the electric field generated by magnetic island merging and the contraction of magnetic islands. We discuss the basic physics of particle acceleration by single magnetic islands and describe how to incorporate these ideas in a distributed "sea of magnetic islands". We describe briefly some observations, selected simulations, and then introduce a transport approach for describing particle acceleration at small-scale flux ropes. We discuss particle acceleration in the supersonic solar wind and extend these ideas to particle acceleration at shock waves. These models are appropriate to the acceleration of both electrons and ions. We describe model predictions and supporting observations.

  9. Upward- directed charged particle flux detection in the MSL/RAD instrument

    Science.gov (United States)

    Appel, Jan Kristoffer; Zeitlin, Cary; Koehler, Jan; Hassler, Donald M.; Rafkin, Scot; Guo, Jingnan; Ehresmann, Bent; Wimmer-Schweingruber, Robert; Matthiä, Daniel; Lohf, Henning

    2016-07-01

    The Mars Science Laboratory rover Curiosity, operating on the surface of Mars, is exposed to radiation fluxes from above and below. Galactic Cosmic Rays travel through the Martian atmosphere, producing a modified spectrum consisting of both primary and secondary particles at ground level. These particles produce an upward- directed secondary particle spectrum as they interact with the Martian soil.These upward- directed particles then pass through the rover and enter the Radiation Assessment Detector onboard the rover from below. Here, we characterize the upward- and downward- directed spectra measured by the detector through a combination of GEANT4 and Planetocosmics simulations. We develop and demonstrate a method to discriminate between upward- and downward- directed particle fluxes during the MSL cruise phase to Mars and the surface science phase. This method enables us to extend the energy range and directionality of RAD beyond its design limits.

  10. DNA-induced inter-particle cross-linking during expanded bed adsorption chromatography - Impact on future support design

    DEFF Research Database (Denmark)

    Theodossiou, Irini; Thomas, Owen R. T.

    2002-01-01

    We have investigated the effects of adsorbent size, ionic capacity and surface immobilised polymers on dynamic capacity and changes occurring to beds of anion-exchangers during the binding of DNA. During application of low concentrations of "3-20 kilobase" calf thymus DNA feeds to expanded beds o...... exhibited a three-fold higher tendency to interact with neighbouring particles in the presence of DNA than that of the dextran DEAE support. The implications of these findings on the design of future expanded bed materials for separation of both proteins and nucleic acids are discussed....

  11. Segregation/Mixing Behavior ofBinary Particles and Formation of Doubl e-Density-Fl uidized Bed

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The current separator with air-dense-medium fluidized bed can only turn out two products at the sametime with a single separating density. The double-density-fluidized bed means that two separating areas with differ-ent densities are formed in a fluidized cascade. In each separating area, the bed density is uniform and meets thetechnical requirement of coal preparation respectively. Therefore, the processed materials can be separated intcthree products according to density. In this paper, the fluidized behaviors of binary dense media were experimental-ly studied and the distribution characteristics of particle concentration and bed density in different bed structurewere discussed. The segregation and mixing mechanisms of binary dense media were analyzed. It was testified thatthe pyramidal part designed in the bed structure played a key role in the formation of double-density-fluidized bed.The pyramidal part intensified the segregation of binary particles between two separating areas and strengthened themixing in the low density area, which made for the density uniform of the area.

  12. Mathematical modelling of particle mixing effect on the combustion of municipal solid wastes in a packed-bed furnace.

    Science.gov (United States)

    Yang, Yao Bin; Swithenbank, Jim

    2008-01-01

    Packed bed combustion is still the most common way to burn municipal solid wastes. In this paper, a dispersion model for particle mixing, mainly caused by the movement of the grate in a moving-burning bed, has been proposed and transport equations for the continuity, momentum, species, and energy conservation are described. Particle-mixing coefficients obtained from model tests range from 2.0x10(-6) to 3.0x10(-5)m2/s. A numerical solution is sought to simulate the combustion behaviour of a full-scale 12-tonne-per-h waste incineration furnace at different levels of bed mixing. It is found that an increase in mixing causes a slight delay in the bed ignition but greatly enhances the combustion processes during the main combustion period in the bed. A medium-level mixing produces a combustion profile that is positioned more at the central part of the combustion chamber, and any leftover combustible gases (mainly CO) enter directly into the most intensive turbulence area created by the opposing secondary-air jets and thus are consumed quickly. Generally, the specific arrangement of the impinging secondary-air jets dumps most of the non-uniformity in temperature and CO into the gas flow coming from the bed-top, while medium-level mixing results in the lowest CO emission at the furnace exit and the highest combustion efficiency in the bed.

  13. Study of Particle Motion in He II Counterflow Across a Wide Heat Flux Range

    Science.gov (United States)

    Mastracci, Brian; Takada, Suguru; Guo, Wei

    2017-01-01

    Some discrepancy exists in the results of He II counterflow experiments obtained using particle image velocimetry (PIV) when compared with those obtained using particle tracking velocimetry (PTV): using PIV, it was observed that tracer particles move at roughly half the expected normal fluid velocity, v_n/2 , while tracer particles observed using PTV moved at approximately v_n . A suggested explanation is that two different flow regimes were examined since the range of heat flux applied in each experiment was adjacent but non-overlapping. Another PTV experiment attempted to test this model, but the applied heat flux did not overlap with any PIV experiments. We report on the beginnings of a study of solid D_2 particle motion in counterflow using PTV, and the heat flux range overlaps that of all previous visualization studies. The observed particle velocity distribution transitions from a two-peak structure to a single peak as the heat flux is increased. Furthermore, the mean value of one peak in the bi-modal distributions grows at approximately the same rate as v_n , while the mean value of the single-peak distributions grows at roughly 0.4v_n , in reasonable agreement with both previous experiments and with the suggested model.

  14. 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 In the study the comparison of irreversibilities was done when the wall condition of the combustor was changed from adiabatic to negative heat flux, for incoming air temperature of 400 K. The reactant mixture of solid pitch pine wood fuel and air...

  15. Investigation of SOL parameters and divertor particle flux from electric probe measurements in KSTAR

    Energy Technology Data Exchange (ETDEWEB)

    Bak, J.G., E-mail: jgbak@nfri.re.kr [National Fusion Research Institute, Daejeon (Korea, Republic of); Kim, H.S. [National Fusion Research Institute, Daejeon (Korea, Republic of); Bae, M.K. [Hanyang University, Seoul (Korea, Republic of); Juhn, J.W.; Seo, D.C.; Bang, E.N. [National Fusion Research Institute, Daejeon (Korea, Republic of); Shim, S.B. [Pusan National University, Pusan (Korea, Republic of); Chung, K.S. [Hanyang University, Seoul (Korea, Republic of); Lee, H.J. [Pusan National University, Pusan (Korea, Republic of); Hong, S.H. [National Fusion Research Institute, Daejeon (Korea, Republic of)

    2015-08-15

    The upstream scrape-off layer (SOL) profiles and downstream particle fluxes are measured with a fast reciprocating Langmuir probe assembly (FRLPA) at the outboard mid-plane and a fixed edge Langmuir probe array (ELPA) at divertor region, respectively in the KSTAR. It is found that the SOL has a two-layer structure in the outboard wall-limited (OWL) ohmic and L-mode: a near SOL (∼5 mm zone) with a narrow feature and a far SOL with a broader profile. The near SOL width evaluated from the SOL profiles in the OWL plasmas is comparable to the scaling for the L-mode divertor plasmas in the JET and AUG. In the SOL profiles and the divertor particle flux profile during the ELMy H-modes, the characteristic e-folding lengths of electron temperature, plasma density and particle flux during an ELM phase are about two times larger than ones at the inter ELM.

  16. Multifield measurement of magnetic fluctuation-induced particle flux in a high-temperature toroidal plasma

    Science.gov (United States)

    Lin, L.; Ding, W. X.; Brower, D. L.

    2016-12-01

    Magnetic fluctuation-induced particle transport is explored in the high-temperature, high-beta interior of the Madison symmetric torus (MST) reversed-field pinch by performing a multifield measurement of the correlated product of magnetic and density fluctuations associated with global resistive tearing modes. Local density fluctuations are obtained by inverting the line-integrated interferometry data after resolving the mode helicity through correlation techniques. The local magnetic and current density fluctuations are then reconstructed using a parameterized fit of Faraday-effect polarimetry measurements. Reconstructed 2D images of density and current density perturbations in a poloidal cross section exhibit significantly different spatial structure. Combined with their relative phase, the magnetic-fluctuation-induced particle transport flux and its spatial distribution are resolved. The convective magnetic fluctuation-induced particle flux profile is measured for both standard and high-performance plasmas in MST with tokamak-like confinement, showing large reduction in the flux during improved confinement.

  17. HIGH-ENERGY PARTICLES FLUX ORIGIN IN THE CLOUDS, DARK LIGHTNING

    Directory of Open Access Journals (Sweden)

    Kuznetsov, V.V.

    2016-11-01

    Full Text Available Problem of high-energy particles flux origin in clouds is discussed. Conditions in which dark lightning preceding the ordinary one and creating additional ionization, fluxes of fast electrons with MeV energy prior to the earthquake detected among lightning initiating ball-lightning, glow, sprites are considered. All above phenomena appear to be of general nature founded on quantum entanglement of hydrogen bonds protons in water clasters inside clouds.

  18. Sinking Particle Flux in the Sea Ice Zone of the Amundsen Shelf, Antarctica

    Science.gov (United States)

    Kim, M.; Hwang, J.; Kim, H. J.; Kim, D.; Ducklow, H. W.; Lee, S. H.; Yang, E. J.; Lee, S.

    2014-12-01

    We have examined the flux, compositions of biogenic components, and isotopic values of sinking particles collected by a sediment trap deployed in the sea ice zone (SIZ) of the Amundsen Sea from January 2011 for one year. Major portion of the particle flux occurred during the austral summer in January and February when sea ice concentration was reduced to below 60 %. Biogenic components, dominated by opal, accounted for over 75 % during this high flux period. The dominant source of sinking particles shifted from diatoms to soft-tissued organisms, evidenced by high particulate organic carbon (POC) content (> 30 %) during the polar night. CaCO3 content and its contribution to total particle flux were low throughout the study period. Contribution of aged POC likely supplied from sediment resuspension was considerable only from October to December, evidenced by low radiocarbon content and relatively high (30-50 %) content of the non-biogenic component. When compared to POC flux inside the Amundsen Sea polynya obtained by the US Amundsen Sea Polynya International Research Expedition (ASPIRE), the POC flux integrated over the austral summer in the SIZ was virtually identical although maximum POC flux was about half that inside the Amundsen Sea polynya. This comparatively high POC flux in the SIZ may be caused by persistence of phytoplankton bloom for longer period and more efficient export of organic matter owing to the diatom-dominant plankton community. If this observation is a general phenomenon on the Amundsen shelf, the role of the SIZ compared to the polynyas need to be examined more carefully when trying to characterize the POC export in this region.

  19. Behavior of TPC`s in a high particle flux environment

    Energy Technology Data Exchange (ETDEWEB)

    Etkin, A.; Eisemann, S.E.; Foley, K.J.; Hackenburg, R.W.; Longacre, R.S.; Love, W.A.; Morris, T.W.; Platner, E.D.; Saulys, A.C. [Brookhaven National Lab., Upton, NY (United States); Lindenbaum, S.J. [Brookhaven National Lab., Upton, NY (United States)]|[City Coll., New York, NY (United States); Chan, C.S.; Kramer, M.A.; Zhao, K.H.; Zhu, Y. [City Coll., New York, NY (United States); Hallman, T.J.; Madansky, L. [Johns Hopkins Univ., Baltimore, MD (United States); Ahmad, S.; Bonner, B.E.; Buchanan, J.A.; Chiou, C.N.; Clement, J.M.; Mutchler, G.S.; Roberts, J.B. [Rice Univ., Houston, TX (United States). Bonner Nuclear Labs.

    1991-12-13

    TPC`s (Time Projection Chamber) used in E-810 at the AGS (Alternating Gradient Synchrotron) were exposed to fluxes equivalent to more than 10{sup 7} minimum ionizing particles per second to find if such high fluxes cause gain changes or distortions of the electric field. Initial results of these and other tests are presented and the consequences for the RHIC (Relativistic Heavy Ion Collider) TPC-based experiments are discussed.

  20. Behavior of TPC`s in a high particle flux environment

    Energy Technology Data Exchange (ETDEWEB)

    Etkin, A.; Eiseman, S.E.; Foley, K.J.; Hackenburg, R.W.; Longacre, R.S.; Love, W.A.; Morris, T.W.; Platner, E.D.; Saulys, A.C. [Brookhaven National Lab., Upton, NY (United States); Lindenbaum, S.J. [Brookhaven National Lab., Upton, NY (United States)]|[City Coll., New York, NY (United States); Chan, C.S.; Kramer, M.A.; Zhao, K.H.; Zhu, Y. [City Coll., New York, NY (United States); Hallman, T.J.; Madansky, L. [Johns Hopkins Univ., Baltimore, MD (United States); Ahmad, S.; Bonner, B.E.; Buchanan, J.A.; Chiou, C.N.; Clement, J.M.; Mutchler, G.S.; Roberts, J.B. [Rice Univ., Houston, TX (United States)

    1992-07-08

    TPC`s (Time Projection Chamber) used in E-810 at the AGS (Alternating Gradient Synchrotron) were exposed to fluxes equivalent to more than 10{sup 7} minimum ionizing particles per second to find if such high fluxes cause gain changes or distortions of the electric field. Initial results of these and other tests are presented and the consequences for the RHIC (Relativistic Heavy Ion collider) TPC-based experiments are discussed.

  1. Behavior of TPC`s in a high particle flux environment

    Energy Technology Data Exchange (ETDEWEB)

    Etkin, A.; Eiseman, S.E.; Foley, K.J.; Hackenburg, R.W.; Longacre, R.S.; Love, W.A.; Morris, T.W.; Platner, E.D.; Saulys, A.C.; Lindenbaum, S.J. [Brookhaven National Lab., Upton, NY (United States); Chan, C.S.; Kramer, M.A.; Zhao, K.H.; Zhu, Y. [City College of New York, New York (United States); Hallman, T.J.; Madansky, L. [Johns Hopkins Univ., Baltimore, MD (United States); Ahmad, S.; Bonner, B.E.; Buchanan, J.A.; Chiou, C.N.; Clement, J.M.; Mutchler, G.S.; Roberts, J.B. [Bonner Nuclear Lab., Houston, TX (United States)

    1991-12-31

    TPC`s (Time Projection Chamber) used in E-810 at the TAGS (Alternating Gradient Synchrotron) were exposed to fluxes equivalent to more than 10 minimum ionizing particles per second to find if such high fluxes cause gain changes or distortions of the electric field. Initial results of these and other tests are presented and the consequences for the RHIC (Relativistic Heavy Ion Collider) TPC-based experiments are discussed.

  2. Behavior of TPC`s in a high particle flux environment

    Energy Technology Data Exchange (ETDEWEB)

    Etkin, A.; Eiseman, S.E.; Foley, K.J.; Hackenburg, R.W.; Longacre, R.S.; Love, W.A.; Morris, T.W.; Platner, E.D.; Saulys, A.C. [Brookhaven National Lab., Upton, NY (United States); Lindenbaum, S.J. [Brookhaven National Lab., Upton, NY (United States)]|[City Coll., New York, NY (United States); Chan, C.S.; Kramer, M.A.; Zhao, K.H.; Zhu, Y. [City Coll., New York, NY (United States); Hallman, T.J.; Madansky, L. [Johns Hopkins Univ., Baltimore, MD (United States); Ahmad, S.; Bonner, B.E.; Buchanan, J.A.; Chiou, C.N.; Clement, J.M.; Mutchler, G.S.; Roberts, J.B. [Rice Univ., Houston, TX (United States). Bonner Nuclear Labs.

    1991-12-31

    TPC`s (Time Projection Chamber) used in E-810 at the AGS (Alternating Gradient Synchrotron) were exposed to fluxes equivalent to more than 10{sup 7} minimum ionizing particles per second to find if such high fluxes cause gain changes or distortions of the electric field. Initial results of these and other tests are presented and the consequences for the RHIC (Relativistic Heavy Ion Collider) TPC-based experiments are discussed.

  3. Reversal of particle flux in collisional-finite beta tokamak discharges

    Energy Technology Data Exchange (ETDEWEB)

    Ma, J.; Wang, G. [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei (China); Weiland, J. [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei (China); Chalmers University of Technology and EURATOM-VR Association, Gothenburg (Sweden); Rafiq, T.; Kritz, A. H. [Department of Physics, Lehigh University, Bethlehem, Pennsylvania 18015 (United States)

    2015-01-15

    The mixed gradient method [Zhong et al. Phys. Rev. Lett. 111, 265001 (2013)] is adopted and effects of collisions and finite beta are included in the Weiland 9-equation fluid model. The particle flux and particle pinch, obtained using the Weiland anomalous transport fluid model, are compared with Tore Supra experimental results. Particle transport is also studied using predictive simulation data for an experimental advanced superconducting tokamak discharge in which neutral beam heating is utilized. The effects of collisions on particle transport are studied by turning collisions on and off in the Weiland model. It is found that the particle pinch region is related to the mode structure. The particle pinch region coincides with the region where the strong ballooning modes are present due to large gradients. The general properties of the fluid model are examined by finding regions where collisions can enhance the particle pinch.

  4. Core Fueling and Edge Particle Flux Analysis in Ohmically and Auxiliary Heated NSTX Plasmas

    Energy Technology Data Exchange (ETDEWEB)

    V.A. Soukhanovskii; R. Maingi; R. Raman; H.W. Kugel; B.P. LeBlanc; L. Roquemore; C.H. Skinner; NSTX Research Team

    2002-06-12

    The Boundary Physics program of the National Spherical Torus Experiment (NSTX) is focusing on optimization of the edge power and particle flows in b * 25% L- and H-mode plasmas of t {approx} 0.8 s duration heated by up to 6 MW of high harmonic fast wave and up to 5 MW of neutral beam injection. Particle balance and core fueling efficiencies of low and high field side gas fueling of L-mode homic and NBI heated plasmas have been compared using an analytical zero dimensional particle balance model and measured ion and neutral fluxes. Gas fueling efficiencies are in the range of 0.05-0.20 and do not depend on discharge magnetic configuration, density or poloidal location of the injector. The particle balance modeling indicates that the addition of HFS fueling results in a reversal of the wall loading rate and higher wall inventories. Initial particle source estimates obtained from neutral pressure and spectroscopic measurements indicate that ion flux into the divertor greatly exceeds midplane ion flux from the main plasma, suggesting that the scrape-off cross-field transport plays a minor role in diverted plasmas. Present analysis provides the basis for detailed fluid modeling of core and edge particle flows and particle confinement properties of NSTX plasmas. This research was supported by the U.S. Department of Energy under contracts No. DE-AC02-76CH03073, DE-AC05-00OR22725, and W-7405-ENG-36.

  5. Analytical model of particle and heat flux collection by dust immersed in dense magnetized plasmas

    Science.gov (United States)

    Vignitchouk, L.; Ratynskaia, S.; Tolias, P.

    2017-10-01

    A comprehensive analytical description is presented for the particle and heat fluxes collected by dust in dense magnetized plasmas. Compared to the widely used orbital motion limited theory, the suppression of cross-field transport leads to a strong reduction of the electron fluxes, while ion collection is inhibited by thin-sheath effects and the formation of a potential overshoot along the field lines. As a result, the incoming heat flux loses its sensitivity to the floating potential, thereby diminishing the importance of electron emission processes in dust survivability. Numerical simulations implementing the new model for ITER-like detached divertor plasmas predict a drastic enhancement of the dust lifetime.

  6. Surface Modification of Fine Particle by Plasma Grafting in a Circulating Fluidized Bed Reactor under Reduced Pressure

    Energy Technology Data Exchange (ETDEWEB)

    Park, Sounghee [Woosuk University, Jinchon (Korea, Republic of)

    2015-10-15

    A plasma surface modification of powders has been carried out in a circulating fluidized bed reactor under reduced pressure. Polystyrene (PS) particles treated by plasma are grafted with polyethylene glycol (PEG) on the surface. The virgin, plasma-treated and grafted powders were characterized by DPPH method, FTIR, SEM and contact angle meter. The plasma-treated PS powders have well formed peroxide on the surface, By PEG grafting polymerization, PEG is well grafted and dispersed on the surface of the plasma-treated PS powders. The PEG-g-PS particle was successfully synthesized using the plasma circulating fluidized bed reactor under reduced pressure.

  7. Influence of particle flux density and temperature on surface modifications of tungsten and deuterium retention

    Energy Technology Data Exchange (ETDEWEB)

    Buzi, Luxherta, E-mail: l.buzi@fz-juelich.de [Ghent University, Department of Applied Physics, Sint-Pietersnieuwstraat 41, B-9000 Ghent (Belgium); FOM Institute DIFFER-Dutch Institute for Fundamental Energy Research, Edisonbaan 14, 3439 MN, PO Box 1207, 3430 BE Nieuwegein (Netherlands); Institut für Energie und Klimaforschung – Plasmaphysik, Forschungszentrum Jülich GmbH, Leo-Brandt-Straße, 52425 Jülich (Germany); Université de Lorraine, Institut Jean Lamour, CNRS UMR 7198, Bvd. des Aiguillettes, F-54506 Vandoeuvre (France); Temmerman, Greg De [FOM Institute DIFFER-Dutch Institute for Fundamental Energy Research, Edisonbaan 14, 3439 MN, PO Box 1207, 3430 BE Nieuwegein (Netherlands); Unterberg, Bernhard; Reinhart, Michael; Litnovsky, Andrey; Philipps, Volker [Institut für Energie und Klimaforschung – Plasmaphysik, Forschungszentrum Jülich GmbH, Leo-Brandt-Straße, 52425 Jülich (Germany); Oost, Guido Van [Ghent University, Department of Applied Physics, Sint-Pietersnieuwstraat 41, B-9000 Ghent (Belgium); Möller, Sören [Institut für Energie und Klimaforschung – Plasmaphysik, Forschungszentrum Jülich GmbH, Leo-Brandt-Straße, 52425 Jülich (Germany)

    2014-12-15

    Systematic study of deuterium irradiation effects on tungsten was done under ITER – relevant high particle flux density, scanning a broad surface temperature range. Polycrystalline ITER – like grade tungsten samples were exposed in linear plasma devices to two different ranges of deuterium ion flux densities (high: 3.5–7 · 10{sup 23} D{sup +}/m{sup 2} s and low: 9 · 10{sup 21} D{sup +}/m{sup 2} s). Particle fluence and ion energy, respectively 10{sup 26} D{sup +}/m{sup 2} and ∼38 eV were kept constant in all cases. The experiments were performed at three different surface temperatures 530 K, 630 K and 870 K. Experimental results concerning the deuterium retention and surface modifications of low flux exposure confirmed previous investigations. At temperatures 530 K and 630 K, deuterium retention was higher at lower flux density due to the longer exposure time (steady state plasma operation) and a consequently deeper diffusion range. At 870 K, deuterium retention was found to be higher at high flux density according to the thermal desorption spectroscopy (TDS) measurements. While blisters were completely absent at low flux density, small blisters of about 40–50 nm were formed at high flux density exposure. At the given conditions, a relation between deuterium retention and blister formation has been found which has to be considered in addition to deuterium trapping in defects populated by diffusion.

  8. Performance of ERNE in particle flux anisotropy measurement

    Directory of Open Access Journals (Sweden)

    E. Riihonen

    Full Text Available The HED particle detector of the ERNE experiment to be flown on the SOHO spacecraft is unique compared to the earlier space-born detectors in its high directional resolution (better than 2°, depending on the track inclination. Despite the fixed view cone due to the three-axis stabilization of the spacecraft, the good angular and temporal resolution of the detector provides a new kind of opportunity for monitoring in detail the development of the anisotropies pertaining, for example, to the onset of SEP events, or passage of shock fronts related to gradual events. In order to optimize the measurement parameters, we have made a preflight simulation study of the HED anisotropy measurement capabilities. The purpose was to prove the feasibility of the selected measurement method and find the physical limits for the HED anisotropy detection. The results show HED to be capable of detecting both strong anisotropies related to impulsive events, and smoother anisotropies associated with gradual events.

  9. Separation and Recovery of Fine Particles from Waste Circuit Boards Using an Inflatable Tapered Diameter Separation Bed

    Directory of Open Access Journals (Sweden)

    Chenlong Duan

    2014-01-01

    Full Text Available Recovering particle materials from discarded printed circuit boards can enhance resource recycling and reduce environmental pollution. Efficiently physically separating and recovering fine metal particles (−0.5 mm from the circuit boards are a key recycling challenge. To do this, a new type of separator, an inflatable tapered diameter separation bed, was developed to study particle motion and separation mechanisms in the bed’s fluid flow field. For 0.5–0.25 mm circuit board particles, metal recovery rates ranged from 87.56 to 94.17%, and separation efficiencies ranged from 87.71 to 94.20%. For 0.25–0.125 mm particles, metal recovery rates ranged from 84.76 to 91.97%, and separation efficiencies ranged from 84.74 to 91.86%. For superfine products (−0.125 mm, metal recovery rates ranged from 73.11 to 83.04%, and separation efficiencies ranged from 73.00 to 83.14%. This research showed that the inflatable tapered diameter separation bed achieved efficient particle separation and can be used to recover fine particles under a wide range of operational conditions. The bed offers a new mechanical technology to recycle valuable materials from discarded printed circuit boards, reducing environmental pollution.

  10. Effect of particle shape of active pharmaceutical ingredients prepared by fluidized-bed jet-milling on cohesiveness.

    Science.gov (United States)

    Fukunaka, Tadashi; Sawaguchi, Kohta; Golman, Boris; Shinohara, Kunio

    2005-05-01

    Milling is a common procedure to improve bioavailability of many active pharmaceutical ingredients (APIs), which typically have low solubility in water. But such micronization can yield an increase in the cohesiveness of particles. Although particle cohesiveness is desirable for tablet strength in the subsequent formulation process, increased particle cohesiveness can lead to operational difficulties in a milling equipment due to compaction of particles inside. In this article, the impact of milling via a fluidized-bed jet-mill on the cohesive strength and interparticle force was studied using Ethenzamide as a pharmaceutical model compound. As a result, the particle shape was found to affect both the tensile strength of powder bed and the interparticle cohesive force. A powder bed, having relatively high void fraction by direct tensile test, shows a positive correlation between the cohesive force and the particle sphericity, while powders with low void fraction by diametral compression test show a positive correlation between the cohesive force and the angularity of the particle.

  11. The prediction of variability occurring in fluidized bed coating equipment. I. The measurement of particle circulation rates in a bottom-spray fluidized bed coater.

    Science.gov (United States)

    Cheng, X X; Turton, R

    2000-01-01

    The purpose of this work was to investigate the effect that changes in design and process variables had on the movement of particles around a fluidized bed coating apparatus. To measure the mean and variance of the particle cycle time distribution (CTD), the number of passages taken by a magnetic tracer particle through the spray zone was measured by a detector coil wound around the partition. The reproducibility of the measurement technique was tested by taking repeated measurements of the tracer particle movement, using similar bed operating conditions, and the method was found to give reproducible results. A series of experiments was carried out by varying operating conditions such as the partition gap, fluidizing air rate, and partition diameter and length, and measuring the change in the rate at which the tracer particle circulated in the coating device. The results of the experiments showed that, over the range of parameters tested in this work, the partition gap had the strongest influence on the rate of particle circulation. Moreover, for the 6-in.-diameter Wurster process used in the current work, the mean circulation time for the 1.1-mm-diameter Nu-Pareil particles was found to vary over the range of 2.2-10.4 sec. In addition, the mean and standard deviation of the CTD could be linearly correlated over a wide range of operating conditions, with a correlation coefficient of 0.80. Finally, an estimate of the variability in mass coating uniformity was made based on the results from the cycle time distributions. It was concluded that the effect of variability in the CTD could account for only a small fraction of the variability in the observed mass coating distribution.

  12. Particle fluxes in the deep Eastern Mediterranean basins: the role of ocean vertical velocities

    Directory of Open Access Journals (Sweden)

    L. Patara

    2008-08-01

    Full Text Available This paper analyzes the relationship between deep sedimentary fluxes and ocean current vertical velocities in an offshore area of the Ionian Sea, the deepest basin of the Eastern Mediterranean Sea. Sediment trap data are collected at 500 m and 2800 m depth in two successive moorings covering the period September 1999–May 2001. A tight coupling is observed between the upper and deep traps and the estimated particle sinking rates are higher than 200 m day−1. The current vertical velocity field is computed from a high resolution Ocean General Circulation Model simulation and from the wind stress curl. Current vertical velocities are larger and more variable than Ekman vertical velocities, yet the general patterns are alike. Current vertical velocities are generally smaller than 1 m day−1: we therefore exclude a direct effect of downward velocities in determining high sedimentation rates. However, we find that upward velocities in the subsurface layers of the water column are positively correlated with deep particle fluxes. We thus hypothesize that upwelling would produce an increase in upper ocean nutrient levels – thus stimulating primary production and grazing – a few weeks before an enhanced vertical flux is found in the sediment traps. By analyzing the delayed effects of ocean vertical velocities on deep particle fluxes we envisage a spectrum of particle sinking speeds ranging from about 100 m day−1 to more than 200 m day−1. High particle sedimentation rates may be attained by means of rapidly sinking fecal pellets produced by gelatinous macro-zooplankton. Other sedimentation mechanisms, such as dust deposition, are also considered in explaining large pulses of deep particle fluxes. The fast sinking rates estimated in this study might be an evidence of the efficiency of the biological pump in sequestering organic carbon from the surface layers of the deep Eastern Mediterranean basins.

  13. Resonant cyclotron acceleration of particles by a time periodic singular flux tube

    CERN Document Server

    Asch, Joachim; Stovicek, Pavel

    2010-01-01

    We study the dynamics of a classical nonrelativistic charged particle moving on a punctured plane under the influence of a homogeneous magnetic field and driven by a periodically time-dependent singular flux tube through the hole. We observe an effect of resonance of the flux and cyclotron frequencies. The particle is accelerated to arbitrarily high energies even by a flux of small field strength which is not necessarily encircled by the cyclotron orbit; the cyclotron orbits blow up and the particle oscillates between the hole and infinity. We support this observation by an analytic study of an approximation for small amplitudes of the flux which is obtained with the aid of averaging methods. This way we derive asymptotic formulas that are afterwards shown to represent a good description of the accelerated motion even for fluxes which are not necessarily small. More precisely, we argue that the leading asymptotic terms may be regarded as approximate solutions of the original system in the asymptotic domain as...

  14. {sup 10}Be/{sup 230}Th ratios as proxy for particle flux in the equatorial Pacific ocean

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, R.F.; Fleisher, M.Q. [LDEO of Columbia Univ. (United States); Kubik, P.W. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Suter, M. [Eidgenoessische Technische Hochschule, Zurich (Switzerland)

    1997-09-01

    Particulate {sup 10}Be/{sup 230}Th ratios collected by sediment traps in the central equatorial Pacific Ocean exhibit a positive correlation with particle flux, but little or no correlation with particle composition. (author) 1 fig., 4 refs.

  15. Observation of Up-gradient Particle Flux in Collisional Drift-ITG Turbulence

    Science.gov (United States)

    Cui, Lang

    2015-11-01

    We report the observation of a net inward, up-gradient turbulent particle flux from two independent diagnostics in collisional drift-ITG plasma turbulence. At low magnetic fields (B = 1.2 kG) the drift-waves persist, an up-gradient inward particle flux develops, fluctuations propagating in the ion diamagnetic drift direction develop and a pronounced steepening of the ion temperature and mean density gradients occurs. The two different types of fluctuation features modulate and compete with each other and dominate in different radial location and magnetic field region. Linear stability analyses show that a robust ITG instability is excited for these conditions. The onset of net inward flux also coincides with the development of a strong intrinsic parallel flow shear that can drive an inward pinch when it is coupled with grad-Ti. However, we find that the ITG-driven inward pinch is more dominant in our experiments. This basic experiment provides for a detailed examination of turbulent-driven particle pinches and up-gradient fluxes in the presence of multiple free-energy sources. Moreover, the coexistence and competition of DWs and ITG have been observed to influence tokamak transport and remains a topic of interest for both magnetically confined fusion plasmas and space plasma systems. A detailed experimental study complemented by theory and linear and nonlinear simulations of these experiments is used to elucidate the physics of up-gradient particle transport. Supported by DOE (DE- SC0001961).

  16. Production of high transient heat and particle fluxes in a linear plasma device

    NARCIS (Netherlands)

    De Temmerman, G.; Zielinski, J. J.; van der Meiden, H.; Melissen, W.; Rapp, J.

    2010-01-01

    We report on the generation of high transient heat and particle fluxes in a linear plasma device by pulsed operation of the plasma source. A capacitor bank is discharged into the source to transiently increase the discharge current up to 1.7 kA, allowing peak densities and temperature of 70x10(20) m

  17. A New Solar Chemical Reactor with an Internally Circulating Fluidized bed for Direct Irradiation of Reacting Particles

    Energy Technology Data Exchange (ETDEWEB)

    Kodama, T.; Enomoto, S.; Hatamachi, T.; Gokon, N.

    2006-07-01

    Solar thermochemical processes require the development of a high temperature solar reactor operating at 1000-1500 degree celsius, such as solar gasification of coal and the thermal reduction of metal oxides as part of a two-step water splitting cycle. Direct solar energy absorption by reacting particles of coal or metal oxides provides efficient heat transfer directly to the reaction site. The present paper describes a new type of the windowed solar chemical reactor directly illuminating reacting particles in an internally circulating fluidized bed. The reactor body is made of stainless steel having a quartz window on the top as aperture. A draft tube is centrally inserted in the fluidized bed region. Gases such as steam, CO2, or N2 are introduced into the draft tube and annulus regions in the bed separately. The concentrated solar radiation passes downwards TROUGH the window and directly heats the internally circulating fluidized bed of reacting particles. The prototype reactor was constructed in a laboratory scale and demonstrated on CO2 gasification of coal coke using solar-simulated, concentrated visible light from sun-simulator as the energy source. About 12% of the maximum chemical storage efficiency was obtained by the solar-simulated gasification of the coke. This new reactor will be also applied for a two-step water splitting cycle using redox metal-oxide particles. (Author)

  18. Research on the detection of fluxes and spectra of charged particles in space

    CERN Document Server

    Sha Jian Jun; Yu Jin Nan; Zhang Wei Guo; Xiang Hong Wen; Wu Zhong Xiang; Cai Zhen Bo; Zhu Wen Ming

    2002-01-01

    A multi-functional spectrometer-identifier was developed for studying fluxes and spectra of protons, alpha particles, oxygen and iron ions in the near-earth space. The telescope system of this spectrometer consists of three Au-Si surface barrier detectors with different thickness and scintillation CsI (Tl). Owing to adopting the DELTA E-E method in particles identification and improved fast response electronics system in data processing and acquisition system, the spectrometer can be used to simultaneously and separately detect the fluxes and spectra of protons of 1-200 MeV, alpha particles of 1-200 MeV/u(nucleon), oxygen ions of 1.7-496 MeV/u and iron ions of 2.5 MeV-1.0 GeV/u

  19. Maximum available flux of charged particles from the laser ablation plasma

    Science.gov (United States)

    Sakai, Yasuo; Itagaki, Tomonobu; Horioka, Kazuhiko

    2016-12-01

    The laser ablation plasma was characterized for high-flux sources of ion and electron beams. An ablation plasma was biased to a positive or a negative high voltage, and the fluxes of charged particles through a pair of extraction electrodes were measured as a function of the laser intensity IL. Maximum available fluxes and the ratios of electron and ion beam currents Je/Ji were evaluated as a function of the laser irradiance. The ion and the electron fluxes increased with a laser intensity and the current ratio was around 40 at IL = 1.3 × 108 W/cm2 which monotonically decreased with an increase of the laser intensity. The current ratios Je/Ji were correlated to the parameters of ablation plasma measured by the electrostatic probes. The results showed that the ion fluxes are basically enhanced by super-sonically drifting ions in the plasma and the electron fluxes are also enhanced by the drift motion together with a reduction of the sheath potential due to the enhanced ion flux to the surrounding wall.

  20. Sources, transport, and mixing of particle-bound PAHs fluxes in the upper Neckar River basin

    Science.gov (United States)

    Schwientek, Marc; Rügner, Hermann; Qin, Xintong; Scherer, Ulrike; Grathwohl, Peter

    2016-04-01

    Transport of many urban pollutants in rivers is coupled to transport of suspended particles. The degree of contamination of these suspended particles depends on the mixture of "polluted" urban and "clean" background particles. Recent results have shown that, in several meso-scale catchments studied in southwestern and eastern Germany, the loading of particles with polycyclic aromatic hydrocarbons (PAHs) was stable over time and characteristic for each catchment. The absence of significant long-term trends or pronounced changes of the catchment-specific loadings indicate that either input and output of PAHs into the stream networks are largely at steady state or that storage of PAHs in the sediments within the stream network are sufficient to smooth out larger fluctuations. Moreover, it was shown that the contamination of sediments and suspended particles with PAHs is proportional to the number of inhabitants per suspended sediment flux in a catchment. These processes are being further studied at larger scale in the upper Neckar River basin (2300 km²) in southwestern Germany. This basin, located between the mountain ranges of the Black Forest and the Swabian Alb, comprises sub-catchments that are diverse in terms of urban impact, geology (ranging from gypsum and limetstones to siliceous sandstones) and hydrology (dynamics driven either by summerly convective events or by winterly frontal systems and snow melt). Accordingly, quality and quantity of particles being released in the sub-catchments as potential vectors for hydrophobic pollutants differ; and so do the events that mobilize the particles. These settings enable the investigation of how particle-bound pollutant fluxes generated at the meso-scale are mixed and transported at larger scales when introduced into a higher order river. A prominent research question is whether varying contributions from contrasting sub-catchments lead to changing contamination patterns in the main stem or if the sediment storage in

  1. Short-term variability in particle flux: Storms, blooms and river discharge in a coastal sea

    Science.gov (United States)

    Johannessen, Sophia C.; Macdonald, Robie W.; Wright, Cynthia A.; Spear, David J.

    2017-07-01

    The flux and composition of particles sinking in the surface ocean vary on a wide range of time scales. This variability is a component of underwater weather that is analogous to rain. The rain of particles in the coastal ocean is affected by atmospheric events, such as rainstorms and windstorms; by events on land, such as peaks in river discharge or coastal erosion; and by events within the surface ocean, such as phytoplankton blooms. Here, we use a four-year record of sinking particles collected using sediment traps moored at 50 m depth at two locations in the Strait of Georgia, a coastal sea off the west coast of Canada, to determine the relative importance of short-term events to particle flux. We identify four dominant types of particle-flux events: those associated with 1) summer freshet of the Fraser River, 2) rainstorms, 3) phytoplankton blooms, and 4) a jellyfish bloom. The relative importance of these events differs between the southern Strait, where the Fraser River freshet dominates flux and variability, and the northern Strait, where the effects of phytoplankton blooms, rainstorms and small local rivers are more evident. During 2008-2012, half of each year's total flux accumulated over 10-26% of the year in the southern Strait, mainly during the Fraser River freshet. In the northern Strait half of the annual flux accumulated over 22-36% of the year, distributed among small events during spring to fall. The composition of the sinking particulate matter also varied widely, with organic carbon and biogenic silica ranging over 0.70-5.7% (excluding one event) and 0.4-14%, respectively, in the south, compared with 0.17-22% and 0.31-33% in the north. Windstorms had no immediate effect on particle flux in either basin. A large phytoplankton bloom in April 2011, in the northern Strait contributed 25% of the year's organic carbon at that site and 53% of the biogenic silica. A jellyfish bloom in July 2008 contributed 16% of the year's nitrogen and 12% of the year

  2. Effect of Particle Size Distribution on Wall Heat Flux in Pulverized-Coal Furnaces and Boilers

    Science.gov (United States)

    Lu, Jun

    A mathematical model of combustion and heat transfer within a cylindrical enclosure firing pulverized coal has been developed and tested against two sets of measured data (one is 1993 WSU/DECO Pilot test data, the other one is the International Flame Research Foundation 1964 Test (Beer, 1964)) and one independent code FURN3D from the Argonne National Laboratory (Ahluwalia and IM, 1992). The model called PILC assumes that the system is a sequence of many well-stirred reactors. A char burnout model combining diffusion to the particle surface, pore diffusion, and surface reaction is employed for predicting the char reaction, heat release, and evolution of char. The ash formation model included relates the ash particle size distribution to the particle size distribution of pulverized coal. The optical constants of char and ash particles are calculated from dispersion relations derived from reflectivity, transmissivity and extinction measurements. The Mie theory is applied to determine the extinction and scattering coefficients. The radiation heat transfer is modeled using the virtual zone method, which leads to a set of simultaneous nonlinear algebraic equations for the temperature field within the furnace and on its walls. This enables the heat fluxes to be evaluated. In comparisons with the experimental data and one independent code, the model is successful in predicting gas temperature, wall temperature, and wall radiative flux. When the coal with greater fineness is burnt, the particle size of pulverized coal has a consistent influence on combustion performance: the temperature peak was higher and nearer to burner, the radiation flux to combustor wall increased, and also the absorption and scattering coefficients of the combustion products increased. The effect of coal particle size distribution on absorption and scattering coefficients and wall heat flux is significant. But there is only a small effect on gas temperature and fuel fraction burned; it is speculated

  3. Further studies of a zinc-air cell employing a packed bed anode. Pt. 2; Regeneration of zinc particles and electrolyte by fluidized bed electrodeposition

    Energy Technology Data Exchange (ETDEWEB)

    Savaskan, G.; Evans, J.W. (Lawrence Berkeley Lab., CA (United States) California Univ., Berkeley, CA (United States). Dept. of Materials Science and Mineral Engineering); Huh, T. (Pusan National Univ. (Korea, Republic of). Dept. of Metallurgical Engineering)

    1992-10-01

    Fluidized bed zinc electrodeposition appears to be an efficient way of regenerating zinc particles and electrolyte from the discharge products of the cell. Using a laboratory cell, various electrode materials were examined to determine their suitability for this electrodeposition. The effects of current density and zincate concentration on the performance of the cell were determined. The lowest d.c. electrical energy consumption achieved was 1.92 kWh kg[sup -1] of zinc at 1000 A m[sup -2] superficial current density. The corresponding figure at 2000 A m[sup -2] was 2.08 kWh kg[sup -1]. (Author).

  4. A model for GCR-particle fluxes in stony meteorites and production rates of cosmogenic nuclides

    Science.gov (United States)

    Reedy, R. C.

    1985-02-01

    A model is presented for the differential fluxes of galactic-cosmic-ray (GCR) particles with energies above 1 MeV inside any spherical stony meteorite as a function of the meteorite's radius and the sample's depth. This model is based on the Reedy-Arnold equations for the energy-dependent fluxes of GCR particles in the moon and is an extension of flux parameters that were derived for several meteorites of various sizes. This flux is used to calculate the production rates of many cosmogenic nuclides as a function of radius and depth. The peak production rates for most nuclides made by the reactions and energetic GCR particles occur near the centers of meteorites with radii of 40 to 70 g/cm (2). Although the model has some limitations, it reproduces well the basic trends for the depth-dependent production of cosmogenic nuclides in stony meteorites of various radii. These production profiles agree fairly well with measurments of cosmogenic nuclides in meteorites. Some of these production profiles are different than those calculated by others. The chemical dependence of the production rates for several nuclides varies with size and depth.

  5. Flux induced growth of sub-Kelvin nano-particles by organic vapor

    Science.gov (United States)

    Wang, J.; McGraw, R. L.; Kuang, C.

    2011-12-01

    New particle formation (NPF) in the atmosphere strongly influences the concentration of atmospheric aerosol, and therefore its impact on climate. New particle formation is a two-stage process consisting of homogeneous nucleation of thermodynamically stable clusters followed by growth of these clusters to a detectable size (> 3 nm). Due to the large coagulation rate of clusters smaller than 3 nm with the pre-existing aerosol population, for new particle formation to take place, these clusters need to grow sufficiently fast before being removed by coagulation. While some previous modeling and field studies have indicated that condensation of low-volatility organic vapor may play an important role in the initial growth of the clusters, it is suggested that due to the small size of the clusters, the strong Kelvin effect may prevent typical ambient organics from condensing on these clusters. Here we show that the particle number flux induced by the heterogeneous nucleation of organics vapor can effectively grow clusters substantially smaller than the Kelvin diameter, traditionally considered as the minimum size of particles that can be grown through condensation. Including this flux can lead to a factor of 10 or higher increases in the predicted rates of new particle formation and the production of cloud condensation nuclei.

  6. Artificial neural network prediction model for geosynchronous electron fluxes: Dependence on satellite position and particle energy

    Science.gov (United States)

    Shin, Dae-Kyu; Lee, Dae-Young; Kim, Kyung-Chan; Hwang, Junga; Kim, Jaehun

    2016-04-01

    Geosynchronous satellites are often exposed to energetic electrons, the flux of which varies often to a large extent. Since the electrons can cause irreparable damage to the satellites, efforts to develop electron flux prediction models have long been made until recently. In this study, we adopt a neural network scheme to construct a prediction model for the geosynchronous electron flux in a wide energy range (40 keV to >2 MeV) and at a high time resolution (as based on 5 min resolution data). As the model inputs, we take the solar wind variables, geomagnetic indices, and geosynchronous electron fluxes themselves. We also take into account the magnetic local time (MLT) dependence of the geosynchronous electron fluxes. We use the electron data from two geosynchronous satellites, GOES 13 and 15, and apply the same neural network scheme separately to each of the GOES satellite data. We focus on the dependence of prediction capability on satellite's magnetic latitude and MLT as well as particle energy. Our model prediction works less efficiently for magnetic latitudes more away from the equator (thus for GOES 13 than for GOES 15) and for MLTs nearer to midnight than noon. The magnetic latitude dependence is most significant for an intermediate energy range (a few hundreds of keV), and the MLT dependence is largest for the lowest energy (40 keV). We interpret this based on degree of variance in the electron fluxes, which depends on magnetic latitude and MLT at geosynchronous orbit as well as particle energy. We demonstrate how substorms affect the flux variance.

  7. The application of a hierarchical Bayesian spatiotemporal model for forecasting the SAA trapped particle flux distribution

    Indian Academy of Sciences (India)

    Wayan Suparta; Gusrizal

    2014-08-01

    We implement a hierarchical Bayesian spatiotemporal (HBST) model to forecast the daily trapped particle flux distribution over the South Atlantic Anomaly (SAA) region. The National Oceanic and Atmospheric Administration (NOAA)-15 data from 1–30 March 2008 with particle energies as < 30 keV (mep0e1) and < 300 keV (mep0e3) for electrons and 80–240 keV (mep0p2) and < 6900 keV (mep0p6) for protons were used as the model input to forecast the flux values on 31 March 2008. Data were transformed into logarithmic values and gridded in a 5° × 5° longitude and latitude size to fulfill the modeling precondition. A Monte Carlo Markov chain (MCMC) was then performed to solve the HBST Gaussian Process (GP) model by using the Gibbs sampling method. The result for this model was interpolated by a Kriging technique to achieve the whole distribution figure over the SAA region. Statistical results of the root mean square error (RMSE), mean absolute percentage error (MAPE), and bias (BIAS) showed a good indicator of the HBST method. The statistical validation also indicated the high variability of particle flux values in the SAA core area. The visual validation showed a powerful combination of HBST-GP model with Kriging interpolation technique. The Kriging also produced a good quality of the distribution map of particle flux over the SAA region as indicated by its small variance value. This suggests that the model can be applied in the development of a Low Earth Orbit (LEO)-Equatorial satellite for monitoring trapped particle radiation hazard.

  8. Drying of oil palm frond particles in a fluidized bed dryer with inert medium

    Directory of Open Access Journals (Sweden)

    Yun May Tee

    2013-01-01

    Full Text Available Drying characteristic of oil palm frond fibres was investigated in a fluidized bed dryer with the presence of inert particles. Sand was used as inert material. Effects of air temperature (60, 70 and 80ºC, air velocity (0.79 and 0.85 m/s and mass ratio of fibres to sand (1:0, 1:1 and 1:2 on the drying curves were investigated. The results showed that the shortest drying time was obtained with the highest air temperature, air velocity and fibres to sand mass ratio. The experimental drying data were fitted to nine existing drying models namely Lewis, Page, Modified Page, Henderson and Pabis, Logarithmic, Two-term, Two-term exponential and Wang and Singh models and a proposed new model. The goodness-of-fit was determined based on the values of r2, c2 and RMSE. The results showed that the best quality of the fit was obtained using the proposed model. The new model was also validated for the superheated steam drying of oil palm empty fruit bunch from other work.

  9. Particle size, moisture, and fluidization variations described by indirect in-line physical measurements of fluid bed granulation.

    Science.gov (United States)

    Lipsanen, Tanja; Närvänen, Tero; Räikkönen, Heikki; Antikainen, Osmo; Yliruusi, Jouko

    2008-01-01

    The aim of this study was to evaluate an instrumentation system for a bench scale fluid bed granulator to determine the parameters expressing the changing conditions during the spraying phase of a fluid bed process. The study focused mainly on four in-line measurements (dependent variables): fluidization parameter (calculated by inlet air flow rate and rotor speed), pressure difference over the upper filters, pressure difference over the granules (lower filter), and temperature of the fluidizing mass. In-line particle size measured by the spatial filtering technique was an essential predictor variable. Other physical process measurements of the automated granulation system, 25 direct and 12 derived parameters, were also utilized for multivariate modeling. The correlation and partial least squares analyses revealed significant relationships between various process parameters highlighting the particle size, moisture, and fluidization effect. Fluidization parameter and pressure difference over upper filters were found to correlate with in-line particle size and therefore could be used as estimates of particle size during granulation. The pressure difference over the granules and the temperature of the fluidizing mass expressed the moisture conditions of wet granulation. The instrumentation system evaluated here is an invaluable aid to gaining more control for fluid bed processing to obtain repeatable granules for further processing.

  10. 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%.

  11. Export and mesopelagic particle flux during a North Atlantic spring diatom bloom

    Science.gov (United States)

    Martin, Patrick; Lampitt, Richard S.; Jane Perry, Mary; Sanders, Richard; Lee, Craig; D'Asaro, Eric

    2011-04-01

    Spring diatom blooms are important for sequestering atmospheric CO 2 below the permanent thermocline in the form of particulate organic carbon (POC). We measured downward POC flux during a sub-polar North Atlantic spring bloom at 100 m using thorium-234 ( 234Th) disequilibria, and below 100 m using neutrally buoyant drifting sediment traps. The cruise followed a Lagrangian float, and a pronounced diatom bloom occurred in a 600 km 2 area around the float. Particle flux was low during the first three weeks of the bloom, between 10 and 30 mg POC m -2 d -1. Then, nearly 20 days after the bloom had started, export as diagnosed from 234Th rose to 360-620 mg POC m -2 d -1, co-incident with silicate depletion in the surface mixed layer. Sediment traps at 600 and 750 m depth collected 160 and 150 mg POC m -2 d -1, with a settled volume of particles of 1000-1500 mL m -2 d -1. This implies that 25-43% of the 100 m POC export sank below 750 m. The sinking particles were ungrazed diatom aggregates that contained transparent exopolymer particles (TEP). We conclude that diatom blooms can lead to substantial particle export that is transferred efficiently through the mesopelagic. We also present an improved method of calibrating the Alcian Blue solution against Gum Xanthan for TEP measurements.

  12. Edge Particle Flux with Temperature Fluctuation in the HL-2A Tokamak

    Institute of Scientific and Technical Information of China (English)

    CHENG Jun; YAN Long-Wen; HONG Wen-Yu; QIAN Jun; ZHAO Kai-Jun

    2007-01-01

    Electron temperature, density, plasma potential and their fluctuation profiles at edge plasmas are measured simultaneously with a reciprocating probe system in HL-2A. The analysis results of four-tip data indicate that the temperature fluctuation has relative amplitude of 10-15%, gives more contribution to particle flux in lower (0- 25 kHz) and higher frequency (50-250 kHz) ranges. The coherence between temperature fluctuation's and density or potential fluctuations implies that their coupling will impact anomalous transport. The measured diffusion coefficient is about three times of the Bohm diffusion coefficient when considering the temperature fluctuation. The particle flux with temperature fluctuation is discussed in HL-2A for the first time.

  13. Sputtering yields of carbon based materials under high particle flux with low energy

    Science.gov (United States)

    Nakamura, K.; Nagase, A.; Dairaku, M.; Akiba, M.; Araki, M.; Okumura, Y.

    1995-04-01

    A new ion source which can produce high particle flux beams at low energies has been developed. This paper presents preliminary results on the sputtering yield of the carbon fiber reinforced composites (CFCs) measured with the new ion source. The sputtering yields of 1D and 2D CFCs, which are candidate materials for the divertor armour tiles, have been measured by the weight loss method under the hydrogen and deuterium particle fluxes of 2 ˜ 7 × 10 20/m 2 s at 50 ˜ 150 eV. Preferential sputtering of the matrix was observed on CFCs which included the matrix of 40 ˜ 60 w%. The energy dependence of the sputtering yields was weak. The sputtering yields of CFCs normally irradiated with deuterium beam were from 0.073 to 0.095, and were around three times larger than those with hydrogen beam.

  14. Particle flux on the continental shelf in the Amundsen Sea Polynya and Western Antarctic Peninsula

    Directory of Open Access Journals (Sweden)

    Hugh W. Ducklow

    2015-04-01

    Full Text Available Abstract We report results from a yearlong, moored sediment trap in the Amundsen Sea Polynya (ASP, the first such time series in this remote and productive ecosystem. Results are compared to a long-term (1992–2013 time series from the western Antarctic Peninsula (WAP. The ASP trap was deployed from December 2010 to December 2011 at 350 m depth. We observed two brief, but high flux events, peaking at 8 and 5 mmol C m−2 d−1 in January and December 2011, respectively, with a total annual capture of 315 mmol C m−2. Both peak fluxes and annual capture exceeded the comparable WAP observations. Like the overlying phytoplankton bloom observed during the cruise in the ASP (December 2010 to January 2011, particle flux was dominated by Phaeocystis antarctica, which produced phytodetrital aggregates. Particles at the start of the bloom were highly depleted in 13C, indicating their origin in the cold, CO2-rich winter waters exposed by retreating sea ice. As the bloom progressed, microscope visualization and stable isotopic composition provided evidence for an increasing contribution by zooplankton fecal material. Incubation experiments and zooplankton observations suggested that fecal pellet production likely contributed 10–40% of the total flux during the first flux event, and could be very high during episodic krill swarms. Independent estimates of export from the surface (100 m were about 5–10 times that captured in the trap at 350 m. Estimated bacterial respiration was sufficient to account for much of the decline in the flux between 50 and 350 m, whereas zooplankton respiration was much lower. The ASP system appears to export only a small fraction of its production deeper than 350 m within the polynya region. The export efficiency was comparable to other polar regions where phytoplankton blooms were not dominated by diatoms.

  15. Impact of a hollow density profile on turbulent particle fluxes: Gyrokinetic and fluid simulations

    Science.gov (United States)

    Tegnered, D.; Oberparleiter, M.; Strand, P.; Nordman, H.

    2017-07-01

    Hollow density profiles may occur in connection with pellet fuelling and L to H transitions. A positive density gradient could potentially stabilize the turbulence or change the relation between convective and diffusive fluxes, thereby reducing the turbulent transport of particles towards the center, making the pellet fuelling scheme inefficient. In the present work, the particle transport driven by Ion Temperature Gradient/Trapped Electron (ITG/TE) mode turbulence in hollow density profiles is studied by fluid as well as gyrokinetic simulations. The fluid model used, an extended version of the Weiland transport model, Extended Drift Wave Model (EDWM), incorporates an arbitrary number of ion species in a multi-fluid description and an extended wavelength spectrum. The fluid model, which is fast and hence suitable for use in predictive simulations, is compared to gyrokinetic simulations using the code GENE. Typical tokamak parameters are used based on the Cyclone Base Case. Parameter scans in key plasma parameters like plasma β, R/LT, and magnetic shear are investigated. In addition, the effects of a fast species are studied and global ITG simulations in a simplified physics description are performed in order to investigate nonlocal effects. It is found that β in particular, has a stabilizing effect in the negative R/Ln region. Both nonlinear GENE and EDWM simulations show a decrease in inward flux for negative R/Ln and a change in the direction from inward to outward for positive R/Ln. Moreover, the addition of fast particles was shown to decrease the inward main ion particle flux in the positive gradient region further. This might have serious consequences for pellet fuelling of high β plasmas. Additionally, the heat flux in global ITG turbulence simulations indicates that nonlocal effects can play a different role from usual in connection with pellet fuelling.

  16. Particle fluxes in the deep Eastern Mediterranean basins: the role of ocean vertical velocities

    Directory of Open Access Journals (Sweden)

    L. Patara

    2009-03-01

    Full Text Available This paper analyzes the relationship between deep sedimentary fluxes and ocean current vertical velocities in an offshore area of the Ionian Sea, the deepest basin of the Eastern Mediterranean Sea. Sediment trap data are collected at 500 m and 2800 m depth in two successive moorings covering the period September 1999–May 2001. A tight coupling is observed between the upper and deep traps and the estimated particle sinking rates are more than 200 m day−1. The current vertical velocity field is computed from a 1/16°×1/16° Ocean General Circulation Model simulation and from the wind stress curl. Current vertical velocities are larger and more variable than Ekman vertical velocities, yet the general patterns are alike. Current vertical velocities are generally smaller than 1 m day−1: we therefore exclude a direct effect of downward velocities in determining high sedimentation rates. However we find that upward velocities in the subsurface layers of the water column are positively correlated with deep particle fluxes. We thus hypothesize that upwelling would produce an increase in upper ocean nutrient levels – thus stimulating primary production and grazing – a few weeks before an enhanced vertical flux is found in the sediment traps. High particle sedimentation rates may be attained by means of rapidly sinking fecal pellets produced by gelatinous macro-zooplankton. Other sedimentation mechanisms, such as dust deposition, are also considered in explaining large pulses of deep particle fluxes. The fast sinking rates estimated in this study might be an evidence of the efficiency of the biological pump in sequestering organic carbon from the surface layers of the deep Eastern Mediterranean basins.

  17. Particle and heat flux estimates in Proto-MPEX in Helicon Mode with IR imaging

    Science.gov (United States)

    Showers, M. A.; Biewer, T. M.; Caughman, J. B. O.; Donovan, D. C.; Goulding, R. H.; Rapp, J.

    2016-10-01

    The Prototype Material Plasma Exposure eXperiment (Proto-MPEX) at Oak Ridge National Laboratory (ORNL) is a linear plasma device developing the plasma source concept for the Material Plasma Exposure eXperiment (MPEX), which will address plasma material interaction (PMI) science for future fusion reactors. To better understand how and where energy is being lost from the Proto-MPEX plasma during ``helicon mode'' operations, particle and heat fluxes are quantified at multiple locations along the machine length. Relevant diagnostics include infrared (IR) cameras, four double Langmuir probes (LPs), and in-vessel thermocouples (TCs). The IR cameras provide temperature measurements of Proto-MPEX's plasma-facing dump and target plates, located on either end of the machine. The change in surface temperature is measured over the duration of the plasma shot to determine the heat flux hitting the plates. The IR cameras additionally provide 2-D thermal load distribution images of these plates, highlighting Proto-MPEX plasma behaviors, such as hot spots. The LPs and TCs provide additional plasma measurements required to determine particle and heat fluxes. Quantifying axial variations in fluxes will help identify machine operating parameters that will improve Proto-MPEX's performance, increasing its PMI research capabilities. This work was supported by the U.S. D.O.E. contract DE-AC05-00OR22725.

  18. The Influence of Filaments in the Private Flux Region on Divertor Particle and Power Deposition

    CERN Document Server

    Harrison, J R; Thornton, A J; Walkden, N R

    2015-01-01

    The transport of particles via intermittent filamentary structures in the private flux region of plasmas in the MAST tokamak has been investigated using a fast framing camera recording visible light emission from the volume of the lower divertor, as well as Langmuir probes and IR thermography monitoring particle and power fluxes to plasma-facing surfaces in the divertor. The visible camera data suggests that, in the divertor volume, fluctuations in light emission above the X-point are strongest in the scrape-off layer (SOL). Conversely, in the region below the X-point, it is found that these fluctuations are strongest in the private flux region (PFR) of the inner divertor leg. Detailed analysis of the appearance of these filaments in the camera data suggests that they are approximately circular, around 1-2cm in diameter. The most probable toroidal mode number is between 2 and 3. These filaments eject plasma deeper into the private flux region, sometimes by the production of secondary filaments, moving at a sp...

  19. A mechanistic-stochastic formulation of bed load particle motions: From individual particle forces to the Fokker-Planck equation under low transport rates

    Science.gov (United States)

    Fan, Niannian; Zhong, Deyu; Wu, Baosheng; Foufoula-Georgiou, Efi; Guala, Michele

    2014-03-01

    Bed load transport is a highly complex process. The probability density function (PDF) of particle velocities results from the local particle momentum variability in response to fluid drag and interactions with the bed. Starting from the forces exerted on a single particle under low transport rates (i.e., rolling and sliding regimes), we derive here the nonlinear stochastic Langevin equation (LE) to describe the dynamics of a single particle, accounting for both the deterministic and the stochastic components of such forces. Then, the Fokker-Planck equation (FPE), which describes the evolution of the PDF of the ensemble particle velocities, is derived from the LE. We show that the theoretical PDFs of both streamwise and cross-stream velocities obtained by solving the FPE under equilibrium conditions have exponential form (PDFs of both positive and negative velocities decay exponentially), consistent with the experimental data by Roseberry et al. Moreover, we theoretically show how the exponential-like PDF of an ensemble of particle velocities results from the forces exerted on a single particle. We also show that the simulated particle motions using the proposed Langevin model exhibit an emergent nonlinear relationship between hop distances and travel times (power law with exponent 5/3), in agreement with the experimental data, providing a statistical description of the particles' random motion in the context of a stochastic transport process. Finally, our study emphasizes that the motion of individual particles, described by the LE, and the behavior of the ensemble, described by the FPE, are connected within a statistical mechanics framework.

  20. Development of a fluidized bed agglomeration modeling methodology to include particle-level heterogeneities in ash chemistry and granular physics

    Science.gov (United States)

    Khadilkar, Aditi B.

    The utility of fluidized bed reactors for combustion and gasification can be enhanced if operational issues such as agglomeration are mitigated. The monetary and efficiency losses could be avoided through a mechanistic understanding of the agglomeration process and prediction of operational conditions that promote agglomeration. Pilot-scale experimentation prior to operation for each specific condition can be cumbersome and expensive. So the development of a mathematical model would aid predictions. With this motivation, the study comprised of the following model development stages- 1) development of an agglomeration modeling methodology based on binary particle collisions, 2) study of heterogeneities in ash chemical composition and gaseous atmosphere, 3) computation of a distribution of particle collision frequencies based on granular physics for a poly-disperse particle size distribution, 4) combining the ash chemistry and granular physics inputs to obtain agglomerate growth probabilities and 5) validation of the modeling methodology. The modeling methodology comprised of testing every binary particle collision in the system for sticking, based on the extent of dissipation of the particles' kinetic energy through viscous dissipation by slag-liquid (molten ash) covering the particles. In the modeling methodology developed in this study, thermodynamic equilibrium calculations are used to estimate the amount of slag-liquid in the system, and the changes in particle collision frequencies are accounted for by continuously tracking the number density of the various particle sizes. In this study, the heterogeneities in chemical composition of fuel ash were studied by separating the bulk fuel into particle classes that are rich in specific minerals. FactSage simulations were performed on two bituminous coals and an anthracite to understand the effect of particle-level heterogeneities on agglomeration. The mineral matter behavior of these constituent classes was studied

  1. The dynamics of large particles in a four-compartment interconnected fluidized bed

    NARCIS (Netherlands)

    Snieders, FF; Hoffmann, AC; Cheesman, D; Yates, JG; Stein, M; Seville, JPK

    1999-01-01

    In order to investigate the potential of a four-compartment interconnected fluidized bed for the combustion of biomass, the behaviour of cylindrical pellets in a bed material of glass ballotini was characterized as a function of the operational parameters. This involved (a) studying the distribution

  2. Probability distributions of bed load particle velocities, accelerations, hop distances, and travel times informed by Jaynes's principle of maximum entropy

    Science.gov (United States)

    Furbish, David J.; Schmeeckle, Mark; Schumer, Rina; Fathel, Siobhan L.

    2016-01-01

    We describe the most likely forms of the probability distributions of bed load particle velocities, accelerations, hop distances, and travel times, in a manner that formally appeals to inferential statistics while honoring mechanical and kinematic constraints imposed by equilibrium transport conditions. The analysis is based on E. Jaynes's elaboration of the implications of the similarity between the Gibbs entropy in statistical mechanics and the Shannon entropy in information theory. By maximizing the information entropy of a distribution subject to known constraints on its moments, our choice of the form of the distribution is unbiased. The analysis suggests that particle velocities and travel times are exponentially distributed and that particle accelerations follow a Laplace distribution with zero mean. Particle hop distances, viewed alone, ought to be distributed exponentially. However, the covariance between hop distances and travel times precludes this result. Instead, the covariance structure suggests that hop distances follow a Weibull distribution. These distributions are consistent with high-resolution measurements obtained from high-speed imaging of bed load particle motions. The analysis brings us closer to choosing distributions based on our mechanical insight.

  3. Characterization of fluidization regime in circulating fluidized bed reactor with high solid particle concentration using computational fluid dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Chalermsinsuwan, Benjapon; Thummakul, Theeranan; Piumsomboon, Pornpote [Chulalongkorn University, Bangkok (Thailand); Gidaspow, Dimitri [Armour College of Engineering, Chicago (United States)

    2014-02-15

    The hydrodynamics inside a high solid particle concentration circulating fluidized bed reactor was investigated using computational fluid dynamics simulation. Compared to a low solid particle reactor, all the conventional fluidization regimes were observed. In addition, two unconventional fluidization regimes, circulating-turbulent and dense suspension bypassing regimes, were found with only primary gas injection. The circulating-turbulent fluidization regime showed uniformly dense solid particle distribution in all the system directions, while the dense suspension bypassing fluidization regime exhibited the flow of solid particles at only one side system wall. Then, comprehensive fluidization regime clarification and mapping were evaluated using in-depth system parameters. In the circulating-turbulent fluidization regime, the total granular temperature was low compared to the adjacent fluidization regimes. In the dense suspension bypassing fluidization regime, the highest total granular temperature was obtained. The circulating-turbulent and dense suspension bypassing fluidization regimes are suitable for sorption and transportation applications, respectively.

  4. Solar energetic particle events: trajectory analysis and flux reconstruction with PAMELA

    CERN Document Server

    Bruno, A; Barbarino, G C; Bazilevskaya, G A; Bellotti, R; Boezio, M; Bogomolov, E A; Bongi, M; Bonvicini, V; Bottai, S; Bravar, U; Cafagna, F; Campana, D; Carbone, R; Carlson, P; Casolino, M; Castellini, G; Christian, E C; De Donato, C; de Nolfo, G A; De Santis, C; De Simone, N; Di Felice, V; Formato, V; Galper, A M; Karelin, A V; Koldashov, S V; Koldobskiy, S; Krutkov, S Y; Kvashnin, A N; Lee, M; Leonov, A; Malakhov, V; Marcelli, L; Martucci, M; Mayorov, A G; Menn, W; Mergè, M; Mikhailov, V V; Mocchiutti, E; Monaco, A; Mori, N; Munini, R; Osteria, G; Palma, F; Panico, B; Papini, P; Pearce, M; Picozza, P; Ricci, M; Ricciarini, S B; Ryan, J M; Sarkar, R; Scotti, V; Simon, M; Sparvoli, R; Spillantini, P; Stochaj, S; Stozhkov, Y I; Vacchi, A; Vannuccini, E; Vasilyev, G I; Voronov, S A; Yurkin, Y T; Zampa, G; Zampa, N; Zverev, V G

    2016-01-01

    The PAMELA satellite experiment is providing first direct measurements of Solar Energetic Particles (SEPs) with energies from about 80 MeV to several GeV in near-Earth space, bridging the low energy data by other space-based instruments and the Ground Level Enhancement (GLE) data by the worldwide network of neutron monitors. Its unique observational capabilities include the possibility of measuring the flux angular distribution and thus investigating possible anisotropies. This work reports the analysis methods developed to estimate the SEP energy spectra as a function of the particle pitch-angle with respect to the Interplanetary Magnetic Field (IMF) direction. The crucial ingredient is provided by an accurate simulation of the asymptotic exposition of the PAMELA apparatus, based on a realistic reconstruction of particle trajectories in the Earth's magnetosphere. As case study, the results for the May 17, 2012 event are presented.

  5. Infrared experiment on the wall temperature distribution for a particle packed channel with constant heat flux

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    With constant heat flux, wall temperature distribution for a particle filled channel was measured using infrared thermal vision technology. It was found that nonuniform relative high-temperature regions were randomly distributed on the heating wall, possibly due to the lower flow velocity, or even due to the blocked flow near the points where particles contact with the heating wall directly. Not only porosity but also the size and shape of the pores are changed in the wall region of particle-packed structures,because of the limitation of the wall, and the changes affect largely the fluid flow and heat transfer. The transition of the flow pattern in pores can be inferred according to the variation of Nu with Re, where the area weighted wall temperature is adopted to calculate the Nu.``

  6. A model for the distribution of particle flux in the mid-water column controlled by subsurface biotic interactions

    Science.gov (United States)

    Jackson, George A.; Burd, Adrian B.

    The sub-euphotic zone water column is important in controlling the downward transport of material falling from the surface waters. Descriptions of the carbon flux as a function of depth have focused on empirical relationships that neglect biological processes that might control them. We develop here a series of simple models of the region that describe changes in flux in terms of the population dynamics of a particle feeder and its predator. One model predicts that the flux and predator concentration at steady state decrease exponentially with depth while the concentration of the particle feeders is constant; a second predicts that flux, particle feeder, and predator concentrations are proportional and decrease at rates that are approximately inversely proportional to depth. Away from steady state, variations in particle flux leaving the surface can induce oscillations in the near-surface animal populations but not the deeper populations. As a result of the animal oscillations associated with the surface flux variations, there can be large swings in the deep vertical particle flux that are not synchronized to the surface variations for one model formulation; a second formulation predicts that fluctuations in surface flux are damped out near the bottom. The differences in predictions for the various models make it possible to verify the utility of one or the other formulation.

  7. On the structure of turbulent gravel bed flow: Implications for sediment transport

    Science.gov (United States)

    Mohajeri, Seyed Hossein; Righetti, Maurizio; Wharton, Geraldene; Romano, Giovanni Paolo

    2016-06-01

    The main objective of this study was to examine the turbulent flow field over gravel particles as a first step towards understanding sediment transport in a gravel bed river. Specifically, the vertical momentum flux in gravel bed turbulent flow was investigated with particular attention to the near-bed region. Spatial organization of vertical momentum flux was studied with stereoscopic Particle Image Velocimetry (PIV) measurements in a horizontal layer 1mm above the gravel crests. The vertical momentum flux through the water column was described with digital PIV measurements in three vertical planes. The data showed that near the gravel bed, net turbulent momentum flux spatially varies with respect to bed topography. Analysis of the vertical velocity data revealed that near the gravel particle crests, there is a significant net vertical form-induced momentum flux approximately with the same order of magnitude as the net vertical turbulent momentum flux. Above the crests, total net vertical momentum flux is positive. However, below the crests, despite noticeable positive form-induced momentum flux, total net vertical momentum flux is negative. Results of quadrant analysis show that variation of turbulent net vertical momentum flux through water column is in agreement with prevalence of upward movement of low velocity flow (known as ejection) above gravel crests and downward movement of high velocity flow (known as sweep) below gravel crests. Below gravel crests (- 0.1 particles but their contribution is not sufficient to move fine particles in the longitudinal direction.

  8. 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

  9. Time evolution of the particle and heat flux of the detached plasma

    Science.gov (United States)

    Pianpanit, Theerasarn; Ishiguro, Seiji; Hasegawa, Hiroki

    2016-10-01

    The detached plasma is a regime when the particle and heat flux of the plasma are largely reduced before reaching the divertor target. Linear devices experiment data show that when the neutral gas pressure in front of the target increases the heat flux to the target largely decreases. The 1D-3V particle simulation with Monte Carlo collision and cumulative scattering angle Coulomb collision has been developed to study the kinetic effect of the detached plasma. The simulation was performed with the constant temperature and pressure of neutral gas in front of the target. A large decrease in the electron temperature from 5eV to below 1 eV follows a large decrease in the ion temperature inside the neutral gas area in the case with high neutral gas pressure in front of the target. The energy flux at the target decreases in the process of attaining the detached state. This work was performed with the support and under the auspices of the NIFS Collaboration Research programs NIFS14KNXN279 and NIFS14KNSS059.

  10. Investigation of a dual-particle liquid-solid circulating fluidized bed bioreactor for extractive fermentation of lactic acid.

    Science.gov (United States)

    Patel, Manoj; Bassi, Amarjeet S; Zhu, Jesse J-X; Gomaa, Hassan

    2008-01-01

    A dual-particle liquid-solid circulating fluidized bed (DP-LSCFB) bioreactor has been constructed and investigated for the simultaneous production and extraction of lactic acid using immobilized Lactobacillus bulgaricus and ion-exchange resins. The apparatus consisted of a downer fluidized bed, 13 cm I.D. and 4.75 m tall, and a riser fluidized bed, 3.8 cm I.D. and 5.15 m in height. The lactic acid production and removal was carried out in the downer, while the riser was used for the recovery of lactic acid. A continuously recirculating bed of ion-exchange resin was used for adsorption of the produced acid as well as for maintaining optimum pH for bioconversion, thus eliminating the need for costly and complex chemical control approach used in conventional techniques. Studies using lactic acid aqueous solution as feed and sodium hydroxide solution as regeneration stream showed 93% lactic acid removal from the downer and 46% recovery in the riser under the conditions investigated. Such results prove the functionality of using the newly developed bioreactor design for the continuous production and recovery of products of biotechnological significance.

  11. Particle acceleration in three-dimensional reconnection of flux-tube disconnection

    Science.gov (United States)

    Akbari, Z.; Hosseinpour, M.; Mohammadi, M. A.

    2016-11-01

    "Flux-tube disconnection" is a type of steady-state three-dimensional magnetic reconnection with O-point at the origin of the resistive diffusion region. Magnetic reconnection is accepted as a potential mechanism for particle acceleration in astrophysical and space plasmas, especially in solar flares. By using the static magnetic and electric fields for flux-tube disconnection, features of test particle acceleration with input parameters for the solar corona are investigated. We show that a proton injected close to origin of the diffusion region can be accelerated to a very high kinetic energy along the magnetic field lines. The efficient acceleration takes place at the radial point where the electric drift velocity has its maximum magnitude. However, a proton injected at radial distances far away from the origin is not accelerated efficiently and even may be trapped in the field lines. The final kinetic energy of the particle depends significantly on the amplitude of the electric field rather than the amplitude of magnetic field.

  12. Observation of the flux line lattice in MPMG-processed YBCO using a decoration technique of ferromagnetic particles

    Science.gov (United States)

    Higashida, Yutaka; Kubo, Yukio; Murakami, Masato; Fujimoto, Hiroyuki; Yamaguchi, Koji; Takata, Tsutomu; Kondoh, Akihiro; Koshizuka, Naoki

    1991-12-01

    Observation of the flux line distribution in MPMG-processed YBa2Cu3O7 has been conducted using a decoration technique of ferromagnetic particles. It has been found that the flux lines are trapped mainly at Y2BaCuO5 inclusions or the interface between the inclusion and the superconducting matrix.

  13. Flux induced growth of atmospheric nano-particles by organic vapors

    Directory of Open Access Journals (Sweden)

    J. Wang

    2012-09-01

    Full Text Available Atmospheric aerosols play critical roles in air quality, public health, and visibility. In addition, they strongly influence climate by scattering solar radiation and by changing the reflectivity and lifetime of clouds. One major but still poorly understood source of atmospheric aerosol is new particle formation, which consists of the formation of thermodynamically stable clusters from trace gas molecules (homogeneous nucleation followed by growth of these clusters to a detectable size (~3 nm. Because freshly nucleated clusters are most susceptible to loss due to high rate of coagulation with pre-existing aerosol population, the initial growth rate strongly influences the rate of new particle formation and ambient aerosol population. Whereas many field observations and modeling studies indicate that organics enhance the initial growth of the clusters and therefore new particle formation, thermodynamic considerations would suggest that the strong increase of equilibrium vapor concentration due to cluster surface curvature (Kelvin effect may prevent ambient organics from condensing on these small clusters. Here the initial condensational growth of freshly nucleated clusters is described as heterogeneous nucleation of organic molecules onto these clusters. We find that the strong gradient in cluster population with respect to its size lead to positive cluster number flux, and therefore driving the growth of clusters substantially smaller than the Kelvin diameter, conventionally considered as the minimum particle size that can be grown through condensation. The conventional approach neglects this contribution from the cluster concentration gradient, and underestimates the rate of new particle formation by a factor of up to 60.

  14. Flux induced growth of atmospheric nano-particles by organic vapors

    Science.gov (United States)

    Wang, J.; McGraw, R. L.; Kuang, C.

    2012-09-01

    Atmospheric aerosols play critical roles in air quality, public health, and visibility. In addition, they strongly influence climate by scattering solar radiation and by changing the reflectivity and lifetime of clouds. One major but still poorly understood source of atmospheric aerosol is new particle formation, which consists of the formation of thermodynamically stable clusters from trace gas molecules (homogeneous nucleation) followed by growth of these clusters to a detectable size (~3 nm). Because freshly nucleated clusters are most susceptible to loss due to high rate of coagulation with pre-existing aerosol population, the initial growth rate strongly influences the rate of new particle formation and ambient aerosol population. Whereas many field observations and modeling studies indicate that organics enhance the initial growth of the clusters and therefore new particle formation, thermodynamic considerations would suggest that the strong increase of equilibrium vapor concentration due to cluster surface curvature (Kelvin effect) may prevent ambient organics from condensing on these small clusters. Here the initial condensational growth of freshly nucleated clusters is described as heterogeneous nucleation of organic molecules onto these clusters. We find that the strong gradient in cluster population with respect to its size lead to positive cluster number flux, and therefore driving the growth of clusters substantially smaller than the Kelvin diameter, conventionally considered as the minimum particle size that can be grown through condensation. The conventional approach neglects this contribution from the cluster concentration gradient, and underestimates the rate of new particle formation by a factor of up to 60.

  15. From particle counts to flux: Wind tunnel testing and calibration of the 'Wenglor' aeolian sediment transport sensor

    Science.gov (United States)

    Barchyn, Thomas E.; Hugenholtz, Chris H.; Li, Bailiang; Neuman, Cheryl McKenna; Steven Sanderson, R.

    2014-12-01

    Despite almost a century of study, aeolian sediment transport remains difficult to measure. Low temporal resolution sediment traps filter sub-second scale variability hypothesized to be important, and high resolution electronic sensors are poorly tested, inconsistent, and often produce incomparable particle count outputs. No sediment transport prediction model can be validated or applied without quality empirical transport measurements. Here, we test a popular electronic laser gate sensor (Wenglor YH03PCT8, 'the Wenglor') in a wind tunnel. We have 3 goals: (i) assess the reproducibility of Wenglor measurements, (ii) examine saturation potential, and (iii) relate trap-measured sediment flux to particle counts. To assess reproducibility we measured particle counts with two co-located Wenglors. Temporally-autocorrelated sections of the time series occurred where one Wenglor deviated; this is likely the result of lens contamination. To examine saturation potential, we measured saltator velocity to calculate particle concentration within the airstream. Particle concentrations suggest the mean number of particles within the laser sampling volume is consistently less than one. To relate trap-measured sediment flux to particle counts, we used particle size samples to calculate an average mass per counted particle. We relate count predicted mass fluxes to trap-measured mass fluxes with linear regression and obtain the relation: trap flux = 2.1 * Wenglor predicted flux (r2 = 0.99). The constant represents aspects of the Wenglor operation that cannot be directly evaluated. Together, these investigations suggest the Wenglor provides a consistent and low-cost method to measure aeolian saltation flux at a high resolution in non-dusty settings.

  16. Downward particle flux and carbon export in the Beaufort Sea, Arctic Ocean; the Malina experiment

    Science.gov (United States)

    Miquel, J.-C.; Gasser, B.; Martín, J.; Marec, C.; Babin, M.; Fortier, L.; Forest, A.

    2015-01-01

    As part of the international, multidisciplinary project Malina, downward particle fluxes were investigated by means of a drifting multi-sediment trap mooring deployed at three sites in the Canadian Beaufort Sea in late summer 2009. Mooring deployments lasted for 28-50 h and targeted the shelf-break and the slope along the Beaufort-Mackenzie continental margin, as well as the edge between the Mackenzie Shelf and the Amundsen Gulf. Besides analyses of C and N, the collected material was investigated for pigments, phyto- and microzooplankton, faecal pellets and swimmers. The measured fluxes were relatively low, in the range of 11-54 mg m-2 d-1 for the total mass, 1-15 mg C m-2 d-1 for organic carbon and 0.2-2.5 mg N m-2 d-1 for nitrogen. Comparison with a long-term trap dataset from the same sampling area showed that the short-term measurements were at the lower end of the high variability characterizing a rather high flux regime during the study period. The sinking material consisted of aggregates and particles that were characterized by the presence of hetero- and autotrophic microzooplankters and diatoms and by the corresponding pigment signatures. Faecal pellets contribution to sinking carbon flux was important, especially at depth where they represented up to 25% of the total carbon flux. The vertical distribution of different morphotypes of pellets showed a marked pattern with cylindrical faeces (produced by calanoid copepods) present mainly within the euphotic zone, whereas elliptical pellets (produced mainly by smaller copepods) were more abundant at mesopelagic depths. These features, together with the density of matter within the pellets, highlighted the role of the zooplankton community in the transformation of carbon issued from the primary production and the transition of that carbon from the productive surface zone to the Arctic Ocean's interior. Our data indicate that sinking carbon flux in this late summer period is primarily the result of a

  17. Downward particle flux and carbon export in the Beaufort Sea, Arctic Ocean; the role of zooplankton

    Science.gov (United States)

    Miquel, J.-C.; Gasser, B.; Martín, J.; Marec, C.; Babin, M.; Fortier, L.; Forest, A.

    2015-08-01

    As part of the international, multidisciplinary project Malina, downward particle fluxes were investigated by means of a drifting multi-sediment trap mooring deployed at three sites in the Canadian Beaufort Sea in late summer 2009. Mooring deployments lasted between 28 and 50 h and targeted the shelf-break and the slope along the Beaufort-Mackenzie continental margin, as well as the edge between the Mackenzie Shelf and the Amundsen Gulf. Besides analyses of C and N, the collected material was investigated for pigments, phyto- and microzooplankton, faecal pellets and swimmers. The measured fluxes were relatively low, in the range of 11-54 mg m-2 d-1 for the total mass, 1-15 mg C m-2 d-1 for organic carbon and 0.2-2.5 mg N m-2 d-1 for nitrogen. Comparison with a long-term trap data set from the same sampling area showed that the short-term measurements were at the lower end of the high variability characterizing a rather high flux regime during the study period. The sinking material consisted of aggregates and particles that were characterized by the presence of hetero- and autotrophic microzooplankters and diatoms and by the corresponding pigment signatures. Faecal pellets contribution to sinking carbon flux was important, especially at depths below 100 m, where they represented up to 25 % of the total carbon flux. The vertical distribution of different morphotypes of pellets showed a marked pattern with cylindrical faeces (produced by calanoid copepods) present mainly within the euphotic zone, whereas elliptical pellets (produced mainly by smaller copepods) were more abundant at mesopelagic depths. These features, together with the density of matter within the pellets, highlighted the role of the zooplankton community in the transformation of carbon issued from the primary production and the transition of that carbon from the productive surface zone to the Arctic Ocean's interior. Our data indicate that sinking carbon flux in this late summer period is primarily

  18. Averaging method of particulate systems and its application to particle-fluid flow in a fluidized bed

    Institute of Scientific and Technical Information of China (English)

    ZHU HaiPing; HOU QinFu; ZHOU ZongYan; YU AiBing

    2009-01-01

    A particulate system can be described through the discrete approach at the microscopic level or through the continuum approach at the macroscopic level. It is very significant to develop the method to link the two approaches for the development of models allowing a better understanding of the fun-damentals of particulate systems. Several averaging methods have been proposed for this purpose in the past, but they mainly focused on cohesionless particle systems. In this work, a more general av-eraging method is proposed by extending it for cohesionless particle systems. The application of the method to the particle-fluid flow in a gas fluidized bed is studied. The density, velocity and stress of this flow are examined. A detailed discussion has been conducted to understand the dependence of the averaged variables on sample size.

  19. Case Study of Particle Number Fluxes and Size Distributions during Nucleation Events in Southeastern Italy in the Summer

    Directory of Open Access Journals (Sweden)

    Marianna Conte

    2015-07-01

    Full Text Available Concentrations, size distributions and particle number vertical turbulent fluxes were measured by the eddy-covariance method at an urban background site in southeastern Italy during the summer. CO2/H2O concentrations and fluxes were also determined together with meteorological parameters. Time series show that particles could be divided into two size classes with negatively-correlated temporal trends in diurnal hours: nanoparticles (diameter Dp < 50 nm and larger particles (Dp > 50 nm. Larger particles include part of the Aitken mode and the accumulation mode. Nanoparticles peaked in diurnal hours due to the presence of several days with nucleation events when particles Dp > 50 nm were at minimum concentrations. Nucleation increased diurnal total particle concentration by a factor of 2.5, reducing mean and median diameters from Dmean = 62.3 ± 1.2 nm and Dmedian = 29.1 ± 1.3 nm on non-event days to Dmean = 35.4 ± 0.6 nm and Dmedian = 15.5 ± 0.3 nm on event days. During nucleation events, particle deposition increased markedly (i.e., downward fluxes, but no significant changes in CO2 concentrations and fluxes were observed. This is compatible with new particle formation above the measurement height and a consequent net transport towards the surface. Correlation with meteorology shows that the formation of new particles is correlated with solar radiation and favored at high wind velocity.

  20. Flocculated meltwater particles control Arctic land-sea fluxes of labile iron

    DEFF Research Database (Denmark)

    Markussen, Thor Nygaard; Elberling, Bo; Winter, Christian;

    2016-01-01

    results reveal how flocculation (particle aggregation) involving labile iron may increase horizontal transport rather than enhance deposition close to the source. This is shown by combining field observations in Disko Fjord, West Greenland, and laboratory experiments. Our data show how labile iron affects...... floc sizes, shapes and densities and consequently yields low settling velocities and extended sediment plumes. We highlight the importance of understanding the flocculation mechanisms when examining fluxes of meltwater transported iron in polar regions today and in the future, and we underline...

  1. Fluctuations of the heat flux of a one-dimensional hard particle gas

    Science.gov (United States)

    Brunet, E.; Derrida, B.; Gerschenfeld, A.

    2010-04-01

    Momentum-conserving one-dimensional models are known to exhibit anomalous Fourier's law, with a thermal conductivity varying as a power law of the system size. Here we measure, by numerical simulations, several cumulants of the heat flux of a one-dimensional hard particle gas. We find that the cumulants, like the conductivity, vary as power laws of the system size. Our results also indicate that cumulants higher than the second follow different power laws when one compares the ring geometry at equilibrium and the linear case in contact with two heat baths (at equal or unequal temperatures).

  2. Generating equally weighted test particles from the one-way flux of a drifting Maxwellian

    Science.gov (United States)

    Makkonen, T.; Airila, M. I.; Kurki-Suonio, T.

    2015-01-01

    The problem of generating equally weighted test particles from the one way flux of drifting Maxwellian is tackled. This paper extends previous work on the subject by presenting a simple and efficient rejection sampling algorithm together with C++ source files. The properties of the underlying probability distribution function, having the form of a normal distribution times x with positive support, are also disseminated. The method presented in this paper has been successfully used to combine fluid and kinetic models for trace impurity problems in plasma physics.

  3. A measure of the degree of inhomogeneity in a distribution and its application in characterising the particle circulation in a fluidized bed

    Energy Technology Data Exchange (ETDEWEB)

    Garncarek, Z. (Inst. of Mathematics, Pedagogical Univ. of Opole (Poland)); Przybylski, L. (Inst. of Tech., Pedagogical Univ. of Opole (Poland)); Botterill, J.S.M. (School of Chemical Engineering, Univ. of Birmingham (United Kingdom)); Bridgwater, J. (School of Chemical Engineering, Univ. of Birmingham (United Kingdom)); Broadbent, C.J. (School of Chemical Engineering, Univ. of Birmingham (United Kingdom))

    1994-09-01

    A quantitative method to evaluate variational processes such as particle circulation in a fluidized bed is presented. It involves the calculation of H, an index of the degree of inhomogeneity in the tracer circulation in standard measure. The position of a given particle in a rectangular fluidized bed was followed using Positron Emission Particle Tracking. This technique is able to locate a labelled solid and construct a three-dimensional trajectory of its movement. The degree of inhomogeneity in the tracer distribution was then calculated from the observations. The values of H for the tracer movement when the bed is operated with a differential air supply across the distributor to stimulate gross solids circulation, suggest that there are relatively large regions of the bed in which the presence of the tracer is much less frequent than elsewhere. This lack of homogeneity in the tracer particle circulation is consistent with visual observation of particle circulation in the investigated bed. Increase in H with increasing length of the duration of the test is consistent with a stable circulation pattern. H affords a quantitative measure of how the fluidized bed parameters influence the particles movement. (orig.)

  4. SIDRA instrument for measurements of particle fluxes at satellite altitudes. Laboratory prototype

    Science.gov (United States)

    Dudnik, O. V.; Prieto, M.; Kurbatov, E. V.; Sanchez, S.; Timakova, T. G.; Spassky, A. V.; Dubina, V. N.; Parra, P.

    2013-01-01

    The design concept and first set of results are presented for electronic modules of a laboratory prototype of the small-size satellite instrument SIDRA intended for measurements of charged particle fluxes in outer space. The working prototype consists of a detector assembly based on high-purity silicon and fast scintillation detectors, modules of analogue and digital processing, and a secondary power supply module. The first results are discussed of a Monte-Carlo simulation of the instrument with the use of the GEANT4 toolkit and of measurements of the main parameters of charge-sensitive pre-amplifiers, shapers, and peak detectors. Results of calibration measurements with the use of radioactive sources and beams of accelerated charged particles are presented.

  5. The Oceanic Flux Program: A three decade time-series of particle flux in the deep Sargasso Sea

    Science.gov (United States)

    Weber, J. C.; Conte, M. H.

    2010-12-01

    The Oceanic Flux Program (OFP), 75 km SE of Bermuda, is the longest running time-series of its kind. Initiated in 1978, the OFP has produced an unsurpassed, nearly continuous record of temporal variability in deep ocean fluxes, with a >90% temporal coverage at 3200m depth. The OFP, in conjunction with the co-located Bermuda-Atlantic Time Series (BATS) and the Bermuda Testbed Mooring (BTM) time-series, has provided key observations enabling detailed assessment of how seasonal and non-seasonal variability in the deep ocean is linked with the overlying physical and biogeochemical environment. This talk will focus on the short-term flux variability that overlies the seasonal flux pattern in the Sargasso Sea, emphasizing episodic extreme flux events. Extreme flux events are responsible for much of the year-to-year variability in mean annual flux and are most often observed during early winter and late spring when surface stratification is weak or transient. In addition to biological phenomena (e.g. salp blooms), passage of productive meso-scale features such as eddies, which alter surface water mixing characteristics and surface export fluxes, may initiate some extreme flux events. Yet other productive eddies show a minimal influence on the deep flux, underscoring the importance of upper ocean ecosystem structure and midwater processes on the coupling between the surface ocean environment and deep fluxes. Using key organic and inorganic tracers, causative processes that influence deep flux generation and the strength of the coupling with the surface ocean environment can be identified.

  6. Influence of fixed and moving bed biofilters on micro particle dynamics in a recirculating aquaculture system

    DEFF Research Database (Denmark)

    Fernandes, Paulo; Pedersen, Lars-Flemming; Pedersen, Per Bovbjerg

    2017-01-01

    is the potentialinfluence of biofilters in this aspect.This study describes the effect of fixed bed biofilters (FBB) and moving bed biofilters (MBB) on particlesize distribution and organic matter. It was conducted in an 8.5 m3RAS with four equal biofilters −two FBB and two MBB. The RAS was stocked with rainbow trout....... Nitrate levels ranged between 40and 44 mg N/L, reflecting stable operating conditions and constant feed loading.The trends observed when FBB or MBB were operated separately were also observed when all filterswere operated simultaneously. Differences in biofilm formation, development and maintenance...

  7. Optimally controlled heating of solid particles in a fluidised bed with a dispersive flow of the solid

    Directory of Open Access Journals (Sweden)

    Poświata Artur

    2016-03-01

    Full Text Available In this study the authors minimise the total process cost for the heating of solid particles in a horizontal fluidised bed by an optimal choice of the inlet heating gas temperature profile and the total gas flow. Solid particles flowed along the apparatus and were heated by a hot gas entering from the bottom of the fluidised apparatus. The hydrodynamics of the fluidised bed is described by a two-phase Kunii - Levenspiel model. We assumed that the gas was flowing only vertically, whereas solid particles were flowing horizontally and because of dispersion they could be additionally mixed up in the same direction. The mixing rate was described by the axial dispersion coefficient. As any economic values of variables describing analysing process are subject to local and time fluctuations, the accepted objective function describes the total cost of the process expressed in exergy units. The continuous optimisation algorithm of the Maximum Principle was used for calculations. A mathematical model of the process, including boundary conditions in a form convenient for optimisation, was derived and presented. The optimization results are presented as an optimal profile of inlet gas temperature. The influence of heat transfer kinetics and dispersion coefficients on optimal runs of the heating process is discussed. Results of this discussion constitute a novelty in comparison to information presented in current literature.

  8. Charged particle's flux measurement from PMMA irradiated by 80 MeV/u carbon ion beam

    CERN Document Server

    Agodi, C; Bellini, F; Cirrone, G A P; Collamati, F; Cuttone, G; De Lucia, E; De Napoli, M; Di Domenico, A; Faccini, R; Ferroni, F; Fiore, S; Gauzzi, P; Iarocci, E; Marafini, M; Mattei, I; Muraro, S; Paoloni, A; Patera, V; Piersanti, L; Romano, F; Sarti, A; Sciubba, A; Vitale, E; Voena, C

    2012-01-01

    Hadrontherapy is an emerging technique in cancer therapy that uses beams of charged particles. To meet the improved capability of hadrontherapy in matching the dose release with the cancer position, new dose monitoring techniques need to be developed and introduced into clinical use. The measurement of the fluxes of the secondary particles produced by the hadron beam is of fundamental importance in the design of any dose monitoring device and is eagerly needed to tune Monte Carlo simulations. We report the measurements done with charged secondary particles produced from the interaction of a 80 MeV/u fully stripped carbon ion beam at the INFN Laboratori Nazionali del Sud, Catania, with a Poly-methyl methacrylate target. Charged secondary particles, produced at 90$\\degree$ with respect to the beam axis, have been tracked with a drift chamber, while their energy and time of flight has been measured by means of a LYSO scintillator. Secondary protons have been identified exploiting the energy and time of flight in...

  9. sup(234) Th scavenging and particle export fluxes from the upper 100 m of the Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Sarin, M.M.; Rengarajan, R.; Ramaswamy, V.

    We have determined the particle scavenging rates, export fluxes of sup(234) Th and settling particles from the upper 100 m of the Arabian Sea as a part of the JGOFS (India) Programme. The spatial and temporal measurements made in the open ocean...

  10. Particle-In-Cell simulation concerning heat-flux mitigation using electromagnetic fields

    Science.gov (United States)

    Lüskow, Karl Felix; Duras, Julia; Kemnitz, Stefan; Kahnfeld, Daniel; Matthias, Paul; Bandelow, Gunnas; Schneider, Ralf; Konigorski, Detlev

    2016-10-01

    In space missions enormous amount of money is spent for the thermal protection system for re-entry. To avoid complex materials and save money one idea is to reduce the heat-flux towards the spacecraft. The partially-ionized gas can be controlled by electromagnetic fields. For first-principle tests partially ionized argon flow from an arc-jet was used to measure the heat-flux mitigation created by an external magnetic field. In the successful experiment a reduction of 85% was measured. In this work the Particle-in-Cell (PIC) method was used to simulate this experiment. PIC is able to reproduce the heat flux mitigation qualitatively. The main mechanism is identified as a changed electron transport and by this, modified electron density due to the reaction to the applied magnetic field. Ions follow due to quasi-neutrality and influence then strongly by charge exchange collisions the neutrals dynamics and heat deposition. This work was supported by the German Space Agency DLR through Project 50RS1508.

  11. Particle propagation, wave growth and energy dissipation in a flaring flux tube

    Science.gov (United States)

    White, S. M.; Melrose, D. B.; Dulk, G. A.

    1986-01-01

    Wave amplification by downgoing particles in a common flare model is investigated. The flare is assumed to occur at the top of a coronal magnetic flux loop, and results in the heating of plasma in the flaring region. The hot electrons propagate down the legs of the flux tube towards increasing magnetic field. It is simple to demonstrate that the velocity distributions which result in this model are unstable to both beam instabilities and cyclotron maser action. An explanation is presented for the propagation effects on the distribution, and the properties of the resulting amplified waves are explored, concentrating on cyclotron maser action, which has properties (emission in the z mode below the local gyrofrequency) quite different from maser action by other distributions considered in the context of solar flares. The z mode waves will be damped in the coronal plasma surrounding the flaring flux tube and lead to heating there. This process may be important in the overall energy budget of the flare. The downgoing maser is compared with the loss cone maser, which is more likely to produce observable bursts.

  12. Electrostatic particle-in-cell simulation of heat flux mitigation using magnetic fields

    Science.gov (United States)

    Lüskow, Karl Felix; Kemnitz, S.; Bandelow, G.; Duras, J.; Kahnfeld, D.; Matthias, P.; Schneider, R.; Konigorski, D.

    2016-10-01

    The particle-in-cell (PIC) method was used to simulate heat flux mitigation experiments with partially ionised argon. The experiments demonstrate the possibility of reducing heat flux towards a target using magnetic fields. Modelling using the PIC method is able to reproduce the heat flux mitigation qualitatively. This is driven by modified electron transport. Electrons are magnetised and react directly to the external magnetic field. In addition, an increase of radial turbulent transport is also needed to explain the experimental observations in the model. Close to the target an increase of electron density is created. Due to quasi-neutrality, ions follow the electrons. Charge exchange collisions couple the dynamics of the neutrals to the ions and reduce the flow velocity of neutrals by radial momentum transport and subsequent losses. By this, the dominant heat-transport channel by neutrals gets reduced and a reduction of the heat deposition, similar to the experiment, is observed. Using the simulation a diagnostic module for optical emission is developed and its results are compared with spectroscopic measurements and photos from the experiment. The results of this study are in good agreement with the experiment. Experimental observations such as a shrank bright emission region close to the nozzle exit, an additional emission in front of the target and an overall change in colour to red are reproduced by the simulation.

  13. Enceladus' Supersonic Gas Jets' Role in Diurnal Variability of Particle Flux

    Science.gov (United States)

    Hansen, Candice; Esposito, Larry W.; Portyankina, Ganna; Hendrix, Amanda; Colwell, Joshua E.; Aye, Klaus-Michael

    2016-10-01

    Introduction: The Cassini Ultraviolet Imaging Spectrograph (UVIS) has observed 6 occultations of stars by Enceladus' plume from 2005 to 2011 [1]. Supersonic gas jets were detected, imbedded in the overall expulsion of gas at escape velocity along the tiger stripe fissures that cross Enceladus' south pole [2]. The gas flux can be calculated [1], and is observed to vary just 15% in over 6 years, representing a steady output of ~200 kg/sec. In contrast, the brightness of the particle jets, a proxy for the amount of particles expelled, varies 3x with orbital longitude [3], implicating tidal stresses. This is not necessarily inconsistent with the steady gas flux, which had not been measured at apokrone until now.2016 epsilon Orionis Occultation: In order to investigate whether gas flow increases dramatically at apokrone an occultation observation was inserted into the Cassini tour on March 11, 2016 on orbit 233. Enceladus was at a mean anomaly of 208 at the time of the occultation. Using the same methodology as previously employed the column density has been determined to be 1.5 x 1016 cm-2, giving a gas flux of 250 kg/sec. This value is 20% higher than the average 210 kg/sec, but only 15% higher than the occultations at a mean anomaly of 236; i.e. higher than the others but not by a factor of 2 or 3. The overall expulsion of gas from the south pole of Enceladus thus does not seem to change dramatically with orbital position.Jets: The line of sight to the star pierced the Baghdad I gas jet. The jet data, in contrast to the integrated plume, look significantly different in this dataset. The column density of the jet is higher than observed in previous occultations. The collimation of the jet is more pronounced and from that we derive a mach number of 8-9, compared to a previous value for this jet of 6. We conclude that the higher velocity and increased quantity of gas in the jet close to apokrone indicate that the jets are the primary contributors to the increased

  14. Downward particle fluxes of biogenic matter and Saharan dust across the equatorial North Atlantic

    Science.gov (United States)

    Korte, Laura F.; Brummer, Geert-Jan A.; van der Does, Michèlle; Guerreiro, Catarina V.; Hennekam, Rick; van Hateren, Johannes A.; Jong, Dirk; Munday, Chris I.; Schouten, Stefan; Stuut, Jan-Berend W.

    2017-05-01

    Massive amounts of Saharan dust are blown from the coast of northern Africa across the Atlantic Ocean towards the Americas each year. This dust has, depending on its chemistry, direct and indirect effects on global climate which include reflection and absorption of solar radiation as well as transport and deposition of nutrients and metals fertilizing both ocean and land. To determine the temporal and spatial variability of Saharan dust transport and deposition and their marine environmental effects across the equatorial North Atlantic Ocean, we have set up a monitoring experiment using deep-ocean sediment traps as well as land-based dust collectors. The sediment traps were deployed at five ocean sites along a transatlantic transect between north-west Africa and the Caribbean along 12° N, in a downwind extension of the land-based dust collectors placed at 19° N on the Mauritanian coast in Iouîk. In this paper, we lay out the setup of the monitoring experiment and present the particle fluxes from sediment trap sampling over 24 continuous and synchronized intervals from October 2012 through to November 2013. We establish the temporal distribution of the particle fluxes deposited in the Atlantic and compare chemical compositions with the land-based dust collectors propagating to the downwind sediment trap sites, and with satellite observations of Saharan dust outbreaks. First-year results show that the total mass fluxes in the ocean are highest at the sampling sites in the east and west, closest to the African continent and the Caribbean, respectively. Element ratios reveal that the lithogenic particles deposited nearest to Africa are most similar in composition to the Saharan dust collected in Iouîk. Downwind increasing Al, Fe and K contents suggest a downwind change in the mineralogical composition of Saharan dust and indicate an increasing contribution of clay minerals towards the west. In the westernmost Atlantic Ocean, admixture of re-suspended clay

  15. Membrane flux dynamics in the submerged ultrafiltration hybrid treatment process during particle and natural organic matter removal

    Institute of Scientific and Technical Information of China (English)

    Wei Zhang; Xiaojian Zhang; Yonghong Li; Jun Wang; Chao Chen

    2011-01-01

    Particles and natural organic matter (NOM) are two major concerns in surface water,which greatly influence the membrane filtration process.The objective of this article is to investigate the effect of particles,NOM and their interaction on the submerged ultrafiltration (UF) membrane flux under conditions of solo UF and coagulation and PAC adsorption as the pretreatment of UF.Particles,NOM and their mixture were spiked in tap water to simulate raw water.Exponential relationship,(JP/JP0 =axexp{-k[t-(n- 1)T]}),was developed to quantify the normalized membrane flux dynamics during the filtration period and fitted the results well.In this equation,coefficient a was determined by the value of Jp/Jp0 at the beginning of a filtration cycle,reflecting the flux recovery after backwashing,that is,the irreversible fouling.The coefficient k reflected the trend of flux dynamics.Integrated total permeability (ΣJp) in one filtration period could be used as a quantified indicator for comparison of different hybrid membrane processes or under different scenarios.According to the results,there was an additive effect on membrane flux by NOM and particles during solo UF process.This additive fouling could be alleviated by coagulation pretreatment since particles helped the formation of flocs with coagulant,which further delayed the decrease of membrane flux and benefited flux recovery by backwashing.The addition of PAC also increased membrane flux by adsorbing NOM and improved flux recovery through backwashing.

  16. Dynamic Force Reduction and Heat Transfer Improvement for Horizontal Tubes in Large-Particle Gas-Fluidized Beds

    Institute of Scientific and Technical Information of China (English)

    Yusumi Nagahashi; John R.Grace; Kok-Seng Lim; Yutaka Asako

    2008-01-01

    The effects of tube bank configuration on forces and heat transfer were investigated for both two-dimensional and three-dimensional gas fluidized beds. Effective dynamic forces and heat transfer coefficients were measured for several tube bank configurations, and it was found that the average forces ate smaller than for a single tube. The heat transfer coefficient can be increased by providing sufficient space for particles to descend around both sides of the tube bank. The results provide useful guidelines for optimizing the configuration of tube banks to achieve high heat transfer coefficients while reducing tube erosion due to dynamic forces.

  17. Laser Doppler anemometry measurements in a circulating fluidized bed of metal particles

    DEFF Research Database (Denmark)

    Ibsen, Claus Hübbe; Solberg, Tron; Hjertager, Bjørn Helge;

    2002-01-01

    Laser Doppler Anemometry (LDA) measurements were performed in a 1/9 scale model of a 12 MW circulating fluidized bed (CFB) boiler. The model was operated according to scaling laws. The 2D-LDA system used was positioned in two different ways to obtain the three velocity components u, v and w...

  18. Tailoring the charged particle fluxes across the target surface of Magnum-PSI

    Science.gov (United States)

    Costin, C.; Anita, V.; Popa, G.; Scholten, J.; De Temmerman, G.

    2016-04-01

    Linear plasma generators are plasma devices designed to study fusion-relevant plasma-surface interactions. The first requirement for such devices is to operate with adjustable and well characterized plasma parameters. In the linear plasma device Magnum-PSI, the distribution of the charged particle flux across the target surface can be tailored by the target bias. The process is based on the radial inhomogeneity of the plasma column and it is evidenced by electrical measurements via a 2D multi-probe system installed as target. Typical results are reported for a hydrogen discharge operated at 125 A and confined by a magnetic field strength of 0.95 T in the middle of the coils. The probes were biased in the range of  -80 to  -25 V, while the floating potential of the target was about  -35 V. The results were obtained in steady-state regime of Magnum-PSI, being time-averaged over any type of fluctuations. Depending on the relative value of the target bias voltage with respect to the local floating potential in the plasma column, the entire target surface can be exposed to ion or electron dominated flux, respectively, or it can be divided into two adjacent zones: one exposed to electron flux and the other to ion flux. As a consequence of this effect, a floating conductive surface that interacts with an inhomogeneous plasma is exposed to non-zero local currents despite its overall null current and it is subjected to internal current flows.

  19. CONCENTRATION DISTRIBUTION OF SEDIMENT IN BED LOAD LAYER

    Institute of Scientific and Technical Information of China (English)

    ZHONG De-yu; ZHANG Hong-wu

    2004-01-01

    In this paper the concentration profile in bed load layer is derived based on kinetic theory. According to observations, particles moving in near wall region behave differently during ejection and sweeping of turbulence burst, as indicates that they are subject to different influences from turbulence, and therefore, the forces acting on particles are not the same. Consequently, particles moving in bed load layer are classified into two groups, one lifted upward by ejections, the other carried back to bed by sweepings, and the forces corresponding to upward and downward motions are proposed. By solving the basic transport equation of kinetic theory, the velocity distribution functions, upward and downward fluxes of particles in bed load layer are derived. Upon assumption of equilibrium sediment transport, concentration profile in bed load layer is obtained. Verification is also presented in this paper, which shows that the concentration profile produced by the relation proposed in this paper agrees with observations well.

  20. Antiproton Flux, Antiproton-to-Proton Flux Ratio, and Properties of Elementary Particle Fluxes in Primary Cosmic Rays Measured with the Alpha Magnetic Spectrometer on the International Space Station.

    Science.gov (United States)

    Aguilar, M; Ali Cavasonza, L; Alpat, B; Ambrosi, G; Arruda, L; Attig, N; Aupetit, S; Azzarello, P; Bachlechner, A; Barao, F; Barrau, A; Barrin, L; Bartoloni, A; Basara, L; Başeǧmez-du Pree, S; Battarbee, M; Battiston, R; Bazo, J; Becker, U; Behlmann, M; Beischer, B; Berdugo, J; Bertucci, B; Bindi, V; Boella, G; de Boer, W; Bollweg, K; Bonnivard, V; Borgia, B; Boschini, M J; Bourquin, M; Bueno, E F; Burger, J; Cadoux, F; Cai, X D; Capell, M; Caroff, S; Casaus, J; Castellini, G; Cernuda, I; Cervelli, F; Chae, M J; Chang, Y H; Chen, A I; Chen, G M; Chen, H S; Cheng, L; Chou, H Y; Choumilov, E; Choutko, V; Chung, C H; Clark, C; Clavero, R; Coignet, G; Consolandi, C; Contin, A; Corti, C; Coste, B; Creus, W; Crispoltoni, M; Cui, Z; Dai, Y M; Delgado, C; Della Torre, S; Demirköz, M B; Derome, L; Di Falco, S; Dimiccoli, F; Díaz, C; von Doetinchem, P; Dong, F; Donnini, F; Duranti, M; D'Urso, D; Egorov, A; Eline, A; Eronen, T; Feng, J; Fiandrini, E; Finch, E; Fisher, P; Formato, V; Galaktionov, Y; Gallucci, G; García, B; García-López, R J; Gargiulo, C; Gast, H; Gebauer, I; Gervasi, M; Ghelfi, A; Giovacchini, F; Goglov, P; Gómez-Coral, D M; Gong, J; Goy, C; Grabski, V; Grandi, D; Graziani, M; Guerri, I; Guo, K H; Habiby, M; Haino, S; Han, K C; He, Z H; Heil, M; Hoffman, J; Hsieh, T H; Huang, H; Huang, Z C; Huh, C; Incagli, M; Ionica, M; Jang, W Y; Jinchi, H; Kang, S C; Kanishev, K; Kim, G N; Kim, K S; Kirn, Th; Konak, C; Kounina, O; Kounine, A; Koutsenko, V; Krafczyk, M S; La Vacca, G; Laudi, E; Laurenti, G; Lazzizzera, I; Lebedev, A; Lee, H T; Lee, S C; Leluc, C; Li, H S; Li, J Q; Li, J Q; Li, Q; Li, T X; Li, W; Li, Z H; Li, Z Y; Lim, S; Lin, C H; Lipari, P; Lippert, T; Liu, D; Liu, Hu; Lu, S Q; Lu, Y S; Luebelsmeyer, K; Luo, F; Luo, J Z; Lv, S S; Majka, R; Mañá, C; Marín, J; Martin, T; Martínez, G; Masi, N; Maurin, D; Menchaca-Rocha, A; Meng, Q; Mo, D C; Morescalchi, L; Mott, P; Nelson, T; Ni, J Q; Nikonov, N; Nozzoli, F; Nunes, P; Oliva, A; Orcinha, M; Palmonari, F; Palomares, C; Paniccia, M; Pauluzzi, M; Pensotti, S; Pereira, R; Picot-Clemente, N; Pilo, F; Pizzolotto, C; Plyaskin, V; Pohl, M; Poireau, V; Putze, A; Quadrani, L; Qi, X M; Qin, X; Qu, Z Y; Räihä, T; Rancoita, P G; Rapin, D; Ricol, J S; Rodríguez, I; Rosier-Lees, S; Rozhkov, A; Rozza, D; Sagdeev, R; Sandweiss, J; Saouter, P; Schael, S; Schmidt, S M; Schulz von Dratzig, A; Schwering, G; Seo, E S; Shan, B S; Shi, J Y; Siedenburg, T; Son, D; Song, J W; Sun, W H; Tacconi, M; Tang, X W; Tang, Z C; Tao, L; Tescaro, D; Ting, Samuel C C; Ting, S M; Tomassetti, N; Torsti, J; Türkoğlu, C; Urban, T; Vagelli, V; Valente, E; Vannini, C; Valtonen, E; Vázquez Acosta, M; Vecchi, M; Velasco, M; Vialle, J P; Vitale, V; Vitillo, S; Wang, L Q; Wang, N H; Wang, Q L; Wang, X; Wang, X Q; Wang, Z X; Wei, C C; Weng, Z L; Whitman, K; Wienkenhöver, J; Willenbrock, M; Wu, H; Wu, X; Xia, X; Xiong, R Q; Xu, W; Yan, Q; Yang, J; Yang, M; Yang, Y; Yi, H; Yu, Y J; Yu, Z Q; Zeissler, S; Zhang, C; Zhang, J; Zhang, J H; Zhang, S D; Zhang, S W; Zhang, Z; Zheng, Z M; Zhu, Z Q; Zhuang, H L; Zhukov, V; Zichichi, A; Zimmermann, N; Zuccon, P

    2016-08-26

    A precision measurement by AMS of the antiproton flux and the antiproton-to-proton flux ratio in primary cosmic rays in the absolute rigidity range from 1 to 450 GV is presented based on 3.49×10^{5} antiproton events and 2.42×10^{9} proton events. The fluxes and flux ratios of charged elementary particles in cosmic rays are also presented. In the absolute rigidity range ∼60 to ∼500  GV, the antiproton p[over ¯], proton p, and positron e^{+} fluxes are found to have nearly identical rigidity dependence and the electron e^{-} flux exhibits a different rigidity dependence. Below 60 GV, the (p[over ¯]/p), (p[over ¯]/e^{+}), and (p/e^{+}) flux ratios each reaches a maximum. From ∼60 to ∼500  GV, the (p[over ¯]/p), (p[over ¯]/e^{+}), and (p/e^{+}) flux ratios show no rigidity dependence. These are new observations of the properties of elementary particles in the cosmos.

  1. CrossRef Antiproton Flux, Antiproton-to-Proton Flux Ratio, and Properties of Elementary Particle Fluxes in Primary Cosmic Rays Measured with the Alpha Magnetic Spectrometer on the International Space Station

    CERN Document Server

    Aguilar, M; Alpat, B; Ambrosi, G; Arruda, L; Attig, N; Aupetit, S; Azzarello, P; Bachlechner, A; Barao, F; Barrau, A; Barrin, L; Bartoloni, A; Basara, L; Başeǧmez-du Pree, S; Battarbee, M; Battiston, R; Bazo, J; Becker, U; Behlmann, M; Beischer, B; Berdugo, J; Bertucci, B; Bindi, V; Boella, G; de Boer, W; Bollweg, K; Bonnivard, V; Borgia, B; Boschini, M  J; Bourquin, M; Bueno, E  F; Burger, J; Cadoux, F; Cai, X  D; Capell, M; Caroff, S; Casaus, J; Castellini, G; Cernuda, I; Cervelli, F; Chae, M  J; Chang, Y  H; Chen, A  I; Chen, G  M; Chen, H  S; Cheng, L; Chou, H  Y; Choumilov, E; Choutko, V; Chung, C  H; Clark, C; Clavero, R; Coignet, G; Consolandi, C; Contin, A; Corti, C; Coste, B; Creus, W; Crispoltoni, M; Cui, Z; Dai, Y  M; Delgado, C; Della Torre, S; Demirköz, M  B; Derome, L; Di Falco, S; Dimiccoli, F; Díaz, C; von Doetinchem, P; Dong, F; Donnini, F; Duranti, M; D'Urso, D; Egorov, A; Eline, A; Eronen, T; Feng, J; Fiandrini, E; Finch, E; Fisher, P; Formato, V; Galaktionov, Y; Gallucci, G; García, B; García-López, R  J; Gargiulo, C; Gast, H; Gebauer, I; Gervasi, M; Ghelfi, A; Giovacchini, F; Goglov, P; Gómez-Coral, D  M; Gong, J; Goy, C; Grabski, V; Grandi, D; Graziani, M; Guerri, I; Guo, K  H; Habiby, M; Haino, S; Han, K  C; He, Z  H; Heil, M; Hoffman, J; Hsieh, T  H; Huang, H; Huang, Z  C; Huh, C; Incagli, M; Ionica, M; Jang, W  Y; Jinchi, H; Kang, S  C; Kanishev, K; Kim, G  N; Kim, K  S; Kirn, Th; Konak, C; Kounina, O; Kounine, A; Koutsenko, V; Krafczyk, M  S; La Vacca, G; Laudi, E; Laurenti, G; Lazzizzera, I; Lebedev, A; Lee, H  T; Lee, S  C; Leluc, C; Li, H  S; Li, J  Q; Li, Q; Li, T  X; Li, W; Li, Z  H; Li, Z  Y; Lim, S; Lin, C  H; Lipari, P; Lippert, T; Liu, D; Liu, Hu; Lu, S  Q; Lu, Y  S; Luebelsmeyer, K; Luo, F; Luo, J  Z; Lv, S  S; Majka, R; Mañá, C; Marín, J; Martin, T; Martínez, G; Masi, N; Maurin, D; Menchaca-Rocha, A; Meng, Q; Mo, D  C; Morescalchi, L; Mott, P; Nelson, T; Ni, J  Q; Nikonov, N; Nozzoli, F; Nunes, P; Oliva, A; Orcinha, M; Palmonari, F; Palomares, C; Paniccia, M; Pauluzzi, M; Pensotti, S; Pereira, R; Picot-Clemente, N; Pilo, F; Pizzolotto, C; Plyaskin, V; Pohl, M; Poireau, V; Putze, A; Quadrani, L; Qi, X  M; Qin, X; Qu, Z  Y; Räihä, T; Rancoita, P  G; Rapin, D; Ricol, J  S; Rodríguez, I; Rosier-Lees, S; Rozhkov, A; Rozza, D; Sagdeev, R; Sandweiss, J; Saouter, P; Schael, S; Schmidt, S  M; Schulz von Dratzig, A; Schwering, G; Seo, E  S; Shan, B  S; Shi, J  Y; Siedenburg, T; Son, D; Song, J  W; Sun, W  H; Tacconi, M; Tang, X  W; Tang, Z  C; Tao, L; Tescaro, D; Ting, Samuel C  C; Ting, S  M; Tomassetti, N; Torsti, J; Türkoğlu, C; Urban, T; Vagelli, V; Valente, E; Vannini, C; Valtonen, E; Vázquez Acosta, M; Vecchi, M; Velasco, M; Vialle, J  P; Vitale, V; Vitillo, S; Wang, L  Q; Wang, N  H; Wang, Q  L; Wang, X; Wang, X  Q; Wang, Z  X; Wei, C  C; Weng, Z  L; Whitman, K; Wienkenhöver, J; Willenbrock, M; Wu, H; Wu, X; Xia, X; Xiong, R  Q; Xu, W; Yan, Q; Yang, J; Yang, M; Yang, Y; Yi, H; Yu, Y  J; Yu, Z  Q; Zeissler, S; Zhang, C; Zhang, J; Zhang, J  H; Zhang, S  D; Zhang, S  W; Zhang, Z; Zheng, Z  M; Zhu, Z  Q; Zhuang, H  L; Zhukov, V; Zichichi, A; Zimmermann, N; Zuccon, P

    2016-01-01

    A precision measurement by AMS of the antiproton flux and the antiproton-to-proton flux ratio in primary cosmic rays in the absolute rigidity range from 1 to 450 GV is presented based on 3.49×105 antiproton events and 2.42×109 proton events. The fluxes and flux ratios of charged elementary particles in cosmic rays are also presented. In the absolute rigidity range ∼60 to ∼500  GV, the antiproton p¯, proton p, and positron e+ fluxes are found to have nearly identical rigidity dependence and the electron e− flux exhibits a different rigidity dependence. Below 60 GV, the (p¯/p), (p¯/e+), and (p/e+) flux ratios each reaches a maximum. From ∼60 to ∼500  GV, the (p¯/p), (p¯/e+), and (p/e+) flux ratios show no rigidity dependence. These are new observations of the properties of elementary particles in the cosmos.

  2. Antiproton Flux, Antiproton-to-Proton Flux Ratio, and Properties of Elementary Particle Fluxes in Primary Cosmic Rays Measured with the Alpha Magnetic Spectrometer on the International Space Station

    Science.gov (United States)

    Aguilar, M.; Ali Cavasonza, L.; Alpat, B.; Ambrosi, G.; Arruda, L.; Attig, N.; Aupetit, S.; Azzarello, P.; Bachlechner, A.; Barao, F.; Barrau, A.; Barrin, L.; Bartoloni, A.; Basara, L.; Başeǧmez-du Pree, S.; Battarbee, M.; Battiston, R.; Bazo, J.; Becker, U.; Behlmann, M.; Beischer, B.; Berdugo, J.; Bertucci, B.; Bindi, V.; Boella, G.; de Boer, W.; Bollweg, K.; Bonnivard, V.; Borgia, B.; Boschini, M. J.; Bourquin, M.; Bueno, E. F.; Burger, J.; Cadoux, F.; Cai, X. D.; Capell, M.; Caroff, S.; Casaus, J.; Castellini, G.; Cernuda, I.; Cervelli, F.; Chae, M. J.; Chang, Y. H.; Chen, A. I.; Chen, G. M.; Chen, H. S.; Cheng, L.; Chou, H. Y.; Choumilov, E.; Choutko, V.; Chung, C. H.; Clark, C.; Clavero, R.; Coignet, G.; Consolandi, C.; Contin, A.; Corti, C.; Coste, B.; Creus, W.; Crispoltoni, M.; Cui, Z.; Dai, Y. M.; Delgado, C.; Della Torre, S.; Demirköz, M. B.; Derome, L.; Di Falco, S.; Dimiccoli, F.; Díaz, C.; von Doetinchem, P.; Dong, F.; Donnini, F.; Duranti, M.; D'Urso, D.; Egorov, A.; Eline, A.; Eronen, T.; Feng, J.; Fiandrini, E.; Finch, E.; Fisher, P.; Formato, V.; Galaktionov, Y.; Gallucci, G.; García, B.; García-López, R. J.; Gargiulo, C.; Gast, H.; Gebauer, I.; Gervasi, M.; Ghelfi, A.; Giovacchini, F.; Goglov, P.; Gómez-Coral, D. M.; Gong, J.; Goy, C.; Grabski, V.; Grandi, D.; Graziani, M.; Guerri, I.; Guo, K. H.; Habiby, M.; Haino, S.; Han, K. C.; He, Z. H.; Heil, M.; Hoffman, J.; Hsieh, T. H.; Huang, H.; Huang, Z. C.; Huh, C.; Incagli, M.; Ionica, M.; Jang, W. Y.; Jinchi, H.; Kang, S. C.; Kanishev, K.; Kim, G. N.; Kim, K. S.; Kirn, Th.; Konak, C.; Kounina, O.; Kounine, A.; Koutsenko, V.; Krafczyk, M. S.; La Vacca, G.; Laudi, E.; Laurenti, G.; Lazzizzera, I.; Lebedev, A.; Lee, H. T.; Lee, S. C.; Leluc, C.; Li, H. S.; Li, J. Q.; Li, J. Q.; Li, Q.; Li, T. X.; Li, W.; Li, Z. H.; Li, Z. Y.; Lim, S.; Lin, C. H.; Lipari, P.; Lippert, T.; Liu, D.; Liu, Hu; Lu, S. Q.; Lu, Y. S.; Luebelsmeyer, K.; Luo, F.; Luo, J. Z.; Lv, S. S.; Majka, R.; Mañá, C.; Marín, J.; Martin, T.; Martínez, G.; Masi, N.; Maurin, D.; Menchaca-Rocha, A.; Meng, Q.; Mo, D. C.; Morescalchi, L.; Mott, P.; Nelson, T.; Ni, J. Q.; Nikonov, N.; Nozzoli, F.; Nunes, P.; Oliva, A.; Orcinha, M.; Palmonari, F.; Palomares, C.; Paniccia, M.; Pauluzzi, M.; Pensotti, S.; Pereira, R.; Picot-Clemente, N.; Pilo, F.; Pizzolotto, C.; Plyaskin, V.; Pohl, M.; Poireau, V.; Putze, A.; Quadrani, L.; Qi, X. M.; Qin, X.; Qu, Z. Y.; Räihä, T.; Rancoita, P. G.; Rapin, D.; Ricol, J. S.; Rodríguez, I.; Rosier-Lees, S.; Rozhkov, A.; Rozza, D.; Sagdeev, R.; Sandweiss, J.; Saouter, P.; Schael, S.; Schmidt, S. M.; Schulz von Dratzig, A.; Schwering, G.; Seo, E. S.; Shan, B. S.; Shi, J. Y.; Siedenburg, T.; Son, D.; Song, J. W.; Sun, W. H.; Tacconi, M.; Tang, X. W.; Tang, Z. C.; Tao, L.; Tescaro, D.; Ting, Samuel C. C.; Ting, S. M.; Tomassetti, N.; Torsti, J.; Türkoǧlu, C.; Urban, T.; Vagelli, V.; Valente, E.; Vannini, C.; Valtonen, E.; Vázquez Acosta, M.; Vecchi, M.; Velasco, M.; Vialle, J. P.; Vitale, V.; Vitillo, S.; Wang, L. Q.; Wang, N. H.; Wang, Q. L.; Wang, X.; Wang, X. Q.; Wang, Z. X.; Wei, C. C.; Weng, Z. L.; Whitman, K.; Wienkenhöver, J.; Willenbrock, M.; Wu, H.; Wu, X.; Xia, X.; Xiong, R. Q.; Xu, W.; Yan, Q.; Yang, J.; Yang, M.; Yang, Y.; Yi, H.; Yu, Y. J.; Yu, Z. Q.; Zeissler, S.; Zhang, C.; Zhang, J.; Zhang, J. H.; Zhang, S. D.; Zhang, S. W.; Zhang, Z.; Zheng, Z. M.; Zhu, Z. Q.; Zhuang, H. L.; Zhukov, V.; Zichichi, A.; Zimmermann, N.; Zuccon, P.; AMS Collaboration

    2016-08-01

    A precision measurement by AMS of the antiproton flux and the antiproton-to-proton flux ratio in primary cosmic rays in the absolute rigidity range from 1 to 450 GV is presented based on 3.49 ×1 05 antiproton events and 2.42 ×1 09 proton events. The fluxes and flux ratios of charged elementary particles in cosmic rays are also presented. In the absolute rigidity range ˜60 to ˜500 GV , the antiproton p ¯, proton p , and positron e+ fluxes are found to have nearly identical rigidity dependence and the electron e- flux exhibits a different rigidity dependence. Below 60 GV, the (p ¯/p ), (p ¯/e+), and (p /e+) flux ratios each reaches a maximum. From ˜60 to ˜500 GV , the (p ¯/p ), (p ¯/e+), and (p /e+) flux ratios show no rigidity dependence. These are new observations of the properties of elementary particles in the cosmos.

  3. MONDO: A neutron tracker for particle therapy secondary emission fluxes measurements

    Science.gov (United States)

    Marafini, M.; Patera, V.; Pinci, D.; Sarti, A.; Sciubba, A.; Spiriti, E.

    2016-07-01

    Cancer treatment is performed, in Particle Therapy, using accelerated charged particles whose high irradiation precision and conformity allows the tumor destruction while sparing the surrounding healthy tissues. Dose release monitoring devices using photons and charged particles produced by the beam interaction with the patient body have already been proposed, but no attempt based on the detection of the abundant secondary radiation neutron component has been made yet. The reduced attenuation length of neutrons yields a secondary particle sample that is larger in number when compared to photons and charged particles. Furthermore, neutrons allow for a backtracking of the emission point that is not affected by multiple scattering. Since neutrons can release a significant dose far away from the tumor region, a precise measurement of their flux, production energy and angle distributions is eagerly needed in order to improve the Treatment Planning Systems (TPS) software, so to predict not only the normal tissue toxicity in the target region but also the risk of late complications in the whole body. All the aforementioned issues underline the importance for an experimental effort devoted to the precise characterization of the neutron production gaining experimental access both to the emission point and production energy. The technical challenges posed by a neutron detector aiming for a high detection efficiency and good backtracking precision will be addressed within the MONDO (MOnitor for Neutron Dose in hadrOntherapy) project. The MONDO's main goal is to develop a tracking detector targeting fast and ultrafast secondary neutrons. The tracker is composed by a scintillating fiber matrix (4 × 4 × 8cm3). The full reconstruction of protons, produced in elastic interactions, will be used to measure energy and direction of the impinging neutron. The neutron tracker will measure the neutron production yields, as a function of production angle and energy, using different

  4. Hydrodynamic modelling of dense gas-fluidised beds: comparison of the kinetic theory of granular flow with 3D hard-sphere discrete particle simulations

    NARCIS (Netherlands)

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

    2002-01-01

    A novel technique to sample particle velocity distributions and collision characteristics from dynamic discrete particle simulations of intrinsically unsteady, non-homogeneous systems, such as those encountered in dense gas-fluidised beds, is presented. The results are compared to the isotropic Maxw

  5. Light Particle Tracking Model for Simulating Bed Sediment Transport Load in River Areas

    Directory of Open Access Journals (Sweden)

    Israel E. Herrera-Díaz

    2017-01-01

    Full Text Available In this work a fast computational particles tracer model is developed based on Particle-In-Cell method to estimate the sediment transport in the access zone of a river port area. To apply the particles tracer method, first it is necessary to calculate the hydrodynamic fields of the study zone to determine the velocity fields in the three directions. The particle transport is governed mainly by the velocity fields and the turbulent dispersion. The mechanisms of dispersion and resuspension of particles are based in stochastic models, which describes the movement through a probability function. The developed code was validated using two well known cases with a discrete transformation obtaining a max relative error around 4.8% in both cases. The simulations were carried out with 350,000 particles allowing us to determine under certain circumstances different hydrodynamic scenarios where the zones are susceptible to present erosion and siltation at the entrance of the port.

  6. VERTIGO (VERtical Transport In the Global Ocean): A study of particle sources and flux attenuation in the North Pacific

    Science.gov (United States)

    Buesseler, K. O.; Trull, T. W.; Steinberg, D. K.; Silver, M. W.; Siegel, D. A.; Saitoh, S.-I.; Lamborg, C. H.; Lam, P. J.; Karl, D. M.; Jiao, N. Z.; Honda, M. C.; Elskens, M.; Dehairs, F.; Brown, S. L.; Boyd, P. W.; Bishop, J. K. B.; Bidigare, R. R.

    2008-07-01

    The VERtical Transport In the Global Ocean (VERTIGO) study examined particle sources and fluxes through the ocean's "twilight zone" (defined here as depths below the euphotic zone to 1000 m). Interdisciplinary process studies were conducted at contrasting sites off Hawaii (ALOHA) and in the NW Pacific (K2) during 3-week occupations in 2004 and 2005, respectively. We examine in this overview paper the contrasting physical, chemical and biological settings and how these conditions impact the source characteristics of the sinking material and the transport efficiency through the twilight zone. A major finding in VERTIGO is the considerably lower transfer efficiency ( Teff) of particulate organic carbon (POC), POC flux 500/150 m, at ALOHA (20%) vs. K2 (50%). This efficiency is higher in the diatom-dominated setting at K2 where silica-rich particles dominate the flux at the end of a diatom bloom, and where zooplankton and their pellets are larger. At K2, the drawdown of macronutrients is used to assess export and suggests that shallow remineralization above our 150-m trap is significant, especially for N relative to Si. We explore here also surface export ratios (POC flux/primary production) and possible reasons why this ratio is higher at K2, especially during the first trap deployment. When we compare the 500-m fluxes to deep moored traps, both sites lose about half of the sinking POC by >4000 m, but this comparison is limited in that fluxes at depth may have both a local and distant component. Certainly, the greatest difference in particle flux attenuation is in the mesopelagic, and we highlight other VERTIGO papers that provide a more detailed examination of the particle sources, flux and processes that attenuate the flux of sinking particles. Ultimately, we contend that at least three types of processes need to be considered: heterotrophic degradation of sinking particles, zooplankton migration and surface feeding, and lateral sources of suspended and sinking

  7. VERTIGO (VERtical Transport In the Global Ocean): A study of particle sources and flux attenuation in the North Pacific

    Energy Technology Data Exchange (ETDEWEB)

    Buesseler, K.O.; Trull, T.W.; Steinberg, D.K.; Silver, M.W.; Siegel, D.A.; Saitoh, S.-I.; Lamborg, C.H.; Lam, P.J.; Karl, D.M.; Jiao, N.Z.; Honda, M.C.; Elskens, M.; Dehairs, F.; Brown, S.L.; Boyd, P.W.; Bishop, J.K.B.; Bidigare, R.R.

    2008-06-10

    The VERtical Transport In the Global Ocean (VERTIGO) study examined particle sources and fluxes through the ocean's 'twilight zone' (defined here as depths below the euphotic zone to 1000 m). Interdisciplinary process studies were conducted at contrasting sites off Hawaii (ALOHA) and in the NW Pacific (K2) during 3 week occupations in 2004 and 2005, respectively. We examine in this overview paper the contrasting physical, chemical and biological settings and how these conditions impact the source characteristics of the sinking material and the transport efficiency through the twilight zone. A major finding in VERTIGO is the considerably lower transfer efficiency (T{sub eff}) of particulate organic carbon (POC), POC flux 500/150 m, at ALOHA (20%) vs. K2 (50%). This efficiency is higher in the diatom-dominated setting at K2 where silica-rich particles dominate the flux at the end of a diatom bloom, and where zooplankton and their pellets are larger. At K2, the drawdown of macronutrients is used to assess export and suggests that shallow remineralization above our 150 m trap is significant, especially for N relative to Si. We explore here also surface export ratios (POC flux/primary production) and possible reasons why this ratio is higher at K2, especially during the first trap deployment. When we compare the 500 m fluxes to deep moored traps, both sites lose about half of the sinking POC by >4000 m, but this comparison is limited in that fluxes at depth may have both a local and distant component. Certainly, the greatest difference in particle flux attenuation is in the mesopelagic, and we highlight other VERTIGO papers that provide a more detailed examination of the particle sources, flux and processes that attenuate the flux of sinking particles. Ultimately, we contend that at least three types of processes need to be considered: heterotrophic degradation of sinking particles, zooplankton migration and surface feeding, and lateral sources of

  8. Concentrations and fluxes of aerosol particles during the LAPBIAT measurement campaign in Värriö field station

    Directory of Open Access Journals (Sweden)

    T. M. Ruuskanen

    2007-01-01

    Full Text Available The LAPBIAT measurement campaign took place in the SMEAR I measurement station located in Eastern Lapland in the spring of 2003 between 26 April and 11 May. In this paper we describe the measurement campaign, concentrations and fluxes of aerosol particles, air ions and trace gases, paying special attention to an aerosol particle formation event broken by a polluted air mass approaching from industrial areas of Kola Peninsula, Russia. Aerosol particle number flux measurements show strong downward fluxes during that time. Concentrations of coarse aerosol particles were high for 1–2 days before the nucleation event (i.e. 28–29 April, very low immediately before and during the observed aerosol particle formation event (30 April and increased moderately from the moment of sudden break of the event. In general particle deposition measurements based on snow samples show the same changes. Measurements of the mobility distribution of air ions showed elevated concentrations of intermediate air ions during the particle formation event. We estimated the growth rates in the nucleation mode size range. For particles <10 nm, the growth rate increases with size on 30 April. Dispersion modelling made with model SILAM support the conclusion that the nucleation event was interrupted by an outbreak of sulphate-rich air mass in the evening of 30 April that originated from the industry at Kola Peninsula, Russia. The results of this campaign highlight the need for detailed research in atmospheric transport of air constituents for understanding the aerosol dynamics.

  9. Charged particle's flux measurement from PMMA irradiated by 80 MeV/u carbon ion beam.

    Science.gov (United States)

    Agodi, C; Battistoni, G; Bellini, F; Cirrone, G A P; Collamati, F; Cuttone, G; De Lucia, E; De Napoli, M; Domenico, A Di; Faccini, R; Ferroni, F; Fiore, S; Gauzzi, P; Iarocci, E; Marafini, M; Mattei, I; Muraro, S; Paoloni, A; Patera, V; Piersanti, L; Romano, F; Sarti, A; Sciubba, A; Vitale, E; Voena, C

    2012-09-21

    Hadrontherapy is an emerging technique in cancer therapy that uses beams of charged particles. To meet the improved capability of hadrontherapy in matching the dose release with the cancer position, new dose-monitoring techniques need to be developed and introduced into clinical use. The measurement of the fluxes of the secondary particles produced by the hadron beam is of fundamental importance in the design of any dose-monitoring device and is eagerly needed to tune Monte Carlo simulations. We report the measurements carried out with charged secondary particles produced from the interaction of a 80 MeV/u fully stripped carbon ion beam at the INFN Laboratori Nazionali del Sud, Catania, with a poly-methyl methacrylate target. Charged secondary particles, produced at 90° with respect to the beam axis, have been tracked with a drift chamber, while their energy and time of flight have been measured by means of a LYSO scintillator. Secondary protons have been identified exploiting the energy and time-of-flight information, and their emission region has been reconstructed backtracking from the drift chamber to the target. Moreover, a position scan of the target indicates that the reconstructed emission region follows the movement of the expected Bragg peak position. Exploiting the reconstruction of the emission region, an accuracy on the Bragg peak determination in the submillimeter range has been obtained. The measured differential production rate for protons produced with E(Prod)(kin) > 83 MeV and emitted at 90° with respect to the beam line is dN(P)/(dN(C)dΩ) (E(Prod)(kin) > 83 MeV, θ = 90°) = (2.69 ± 0.08(stat) ± 0.12(sys)) × 10⁻⁴ sr⁻¹.

  10. Direct detection of cosmic rays: through a new era of precision measurements of particle fluxes

    CERN Document Server

    Mocchiutti, Emiliano

    2014-01-01

    In the last years the direct measurement of cosmic rays received a push forward by the possibility of conducting experiments on board long duration balloon flights, satellites and on the International Space Station. The increase in the collected statistics and the technical improvements in the construction of the detectors permit the fluxes measurement to be performed at higher energies with a reduced discrepancy among different experiments respect to the past. However, high statistical precision is not always associated to the needed precision in the estimation of systematics; features in the particle spectra can be erroneously introduced or hidden. A review and a comparison of the latest experimental results on direct cosmic rays measurements will be presented with particular emphasis on their similarities and discrepancies.

  11. Breadboard model of the SIDRA instrument designed for the measurement of charged particle fluxes in space

    Science.gov (United States)

    Prieto, M.; Dudnik, O. V.; Sanchez, S.; Kurbatov, E. V.; Timakova, T. G.; Tejedor, J. I. G.; Titov, K. G.

    2013-04-01

    This report delves into the concept of the SIDRA instrument designed for the measurement of energetic fluxes of charged particles in space. It also presents the preliminary laboratory tests results of the breadboard model electronic units. The SIDRA instrument consists of a detector head made of high purity silicon and high performance scintillation detectors, analog and digital signal processing units, and it also includes a secondary power supply module. Preliminary results of Monte Carlo instrument simulation using the CERN GEANT4 tool are presented and the measured key specifications of charge-to-voltage converters, shapers and peak detectors are discussed. Finally, the performance of the digital processing unit with its software and the parameters of the instrument breadboard model, in particular mass, dimensions and power consumption are also presented.

  12. Flocculated meltwater particles control Arctic land-sea fluxes of labile iron

    Science.gov (United States)

    Markussen, Thor Nygaard; Elberling, Bo; Winter, Christian; Andersen, Thorbjørn Joest

    2016-04-01

    Glacial meltwater systems supply the Arctic coastal ocean with large volumes of sediment and potentially bioavailable forms of iron, nitrogen and carbon. The particulate fraction of this supply is significant but estuarine losses have been thought to limit the iron supply from land. Here, our results reveal how flocculation (particle aggregation) involving labile iron may increase horizontal transport rather than enhance deposition close to the source. This is shown by combining field observations in Disko Fjord, West Greenland, and laboratory experiments. Our data show how labile iron affects floc sizes, shapes and densities and consequently yields low settling velocities and extended sediment plumes. We highlight the importance of understanding the flocculation mechanisms when examining fluxes of meltwater transported iron in polar regions today and in the future, and we underline the influence of terrestrial hotspots on the nutrient and solute cycles in Arctic coastal waters.

  13. Flocculated meltwater particles control Arctic land-sea fluxes of labile iron.

    Science.gov (United States)

    Markussen, Thor Nygaard; Elberling, Bo; Winter, Christian; Andersen, Thorbjørn Joest

    2016-04-06

    Glacial meltwater systems supply the Arctic coastal ocean with large volumes of sediment and potentially bioavailable forms of iron, nitrogen and carbon. The particulate fraction of this supply is significant but estuarine losses have been thought to limit the iron supply from land. Here, our results reveal how flocculation (particle aggregation) involving labile iron may increase horizontal transport rather than enhance deposition close to the source. This is shown by combining field observations in Disko Fjord, West Greenland, and laboratory experiments. Our data show how labile iron affects floc sizes, shapes and densities and consequently yields low settling velocities and extended sediment plumes. We highlight the importance of understanding the flocculation mechanisms when examining fluxes of meltwater transported iron in polar regions today and in the future, and we underline the influence of terrestrial hotspots on the nutrient and solute cycles in Arctic coastal waters.

  14. Flocculated meltwater particles control Arctic land-sea fluxes of labile iron

    DEFF Research Database (Denmark)

    Markussen, Thor Nygaard; Elberling, Bo; Winter, Christian

    2016-01-01

    Glacial meltwater systems supply the Arctic coastal ocean with large volumes of sediment and potentially bioavailable forms of iron, nitrogen and carbon. The particulate fraction of this supply is significant but estuarine losses have been thought to limit the iron supply from land. Here, our...... results reveal how flocculation (particle aggregation) involving labile iron may increase horizontal transport rather than enhance deposition close to the source. This is shown by combining field observations in Disko Fjord, West Greenland, and laboratory experiments. Our data show how labile iron affects...... floc sizes, shapes and densities and consequently yields low settling velocities and extended sediment plumes. We highlight the importance of understanding the flocculation mechanisms when examining fluxes of meltwater transported iron in polar regions today and in the future, and we underline...

  15. An improved design of TRISO particle with porous SiC inner layer by fluidized bed-chemical vapor deposition

    Science.gov (United States)

    Liu, Rongzheng; Liu, Malin; Chang, Jiaxing; Shao, Youlin; Liu, Bing

    2015-12-01

    Tristructural-isotropic (TRISO) particle has been successful in high temperature gas cooled reactor (HTGR), but an improved design is required for future development. In this paper, the coating layers are reconsidered, and an improved design of TRISO particle with porous SiC inner layer is proposed. Three methods of preparing the porous SiC layer, called high methyltrichlorosilane (MTS) concentration method, high Ar concentration method and hexamethyldisilane (HMDS) method, are experimentally studied. It is indicated that porous SiC layer can be successfully prepared and the density of SiC layer can be adjusted by tuning the preparation parameters. Microstructure and characterization of the improved TRISO coated particle are given based on scanning electron microscope (SEM), X-ray diffraction (XRD), Raman scattering and energy dispersive X-ray (EDX) analysis. It can be found that the improved TRISO coated particle with porous SiC layer can be mass produced successfully. The formation mechanisms of porous SiC layer are also discussed based on the fluidized bed-chemical vapor deposition principle.

  16. FORTE satellite constraints on ultra-high energy cosmic particle fluxes

    CERN Document Server

    Lehtinen, N G; Jacobson, A R; Roussel-Dupre, R A; Lehtinen, Nikolai G.; Gorham, Peter W.; Jacobson, Abram R.; Roussel-Dupre, Robert A.

    2004-01-01

    The FORTE (Fast On-orbit Recording of Transient Events) satellite records bursts of electromagnetic waves arising from near the Earth's surface in the radio frequency (RF) range of 30 to 300 MHz with a dual polarization antenna. We investigate the possible RF signature of ultra-high energy cosmic-ray particles in the form of coherent Cherenkov radiation from cascades in ice. We calculate the sensitivity of the FORTE satellite to ultra-high energy (UHE) neutrino fluxes at different energies beyond the Greisen-Zatsepin-Kuzmin (GZK) cutoff. Some constraints on supersymmetry model parameters are also estimated due to the limits that FORTE sets on the UHE neutralino flux. The FORTE database consists of over 4 million recorded events to date, including in principle some events associated with UHE neutrinos. We search for candidate FORTE events in the period from September 1997 to December 1999. The candidate production mechanism is via coherent VHF radiation from a UHE neutrino shower in the Greenland ice sheet. We...

  17. New welding fluxes based on silicomanganese slag for deposition and welding of canopies and crib bed of mine support

    Science.gov (United States)

    Kryukov, R. E.; Kozyrev, N. A.; Usoltsev, A. A.; Kozyreva, O. E.

    2017-09-01

    The paper considers the possibility of efficient use of silicomanganese slag for the production of welding fluxes. The results of studying the use of metallurgical wastes as components of welding fluxes are given. Analysis of the results of mechanical properties of the samples made it possible to determine the optimum content of the pulverized fraction less than 0.45 mm in the flux. The composition and technology of manufacturing a new welding flux using slag of silicomanganese production was developed. The effect of fractional composition on the welding-technological properties of fluxes was studied. The optimal content of liquid glass in the flux, which allows a favorable complex of mechanical properties to be obtained, is 20-30%. To reduce the level of contamination of the weld metal with non-metallic oxide inclusions and to increase the mechanical properties of the welded joint, it is proposed to introduce a carbon-fluorine-containing additive FD-UFS into fluxes based on the slag.

  18. Observation of the flux line lattice in MPMG-processed YBCO using a decoration technique of ferromagnetic particles

    Energy Technology Data Exchange (ETDEWEB)

    Higashida, Yutaka; Kubo, Yukio (Research and Development Lab., Japan Fine Ceramics Center, Nagoya (Japan)); Murakami, Masato; Fujimoto, Hiroyuki; Yamaguchi, Koji; Takata, Tsutomu; Kondoh, Akihiro; Koshizuka, Naoki (Superconductivity Research Lab., International Superconductivity Tech. Center, Tokyo (Japan))

    1991-12-01

    Observations of the flux line distribution in MPMG-processed YBa{sub 2}Cu{sub 3}O{sub 7} has been conducted using a dcecoration technique of ferromagnetic particles. It has been found that the flux lines are trapped mainly at Y{sub 2}BaCuO{sub 5} inclusions or the interface between the inclusion and the superconducting matrix. (orig.).

  19. Evaluation of in-line spatial filter velocimetry as PAT monitoring tool for particle growth during fluid bed granulation.

    Science.gov (United States)

    Burggraeve, A; Van Den Kerkhof, T; Hellings, M; Remon, J P; Vervaet, C; De Beer, T

    2010-09-01

    In this study, the feasibility of spatial filter velocimetry (SFV) as process analytical technology tool for the in-line monitoring of the particle size distribution during top spray fluidized bed granulation was examined. The influence of several process (inlet air temperature during spraying and drying) and formulation variables (HPMC and Tween 20 concentration) upon the particle size distribution during processing, and the end product particle size distribution, tapped density and Hausner ratio was examined using a design of experiments (DOE) (2-level full factorial design, 19 experiments). The trend in end granule particle size distributions of all DOE batches measured with in-line SFV was similar to the off-line laser diffraction (LD) data. Analysis of the DOE results showed that mainly the HPMC concentration and slightly the inlet air temperature during drying had a positive effect on the average end granule size. The in-line SFV particle size data, obtained every 10s during processing, further allowed to explain and better understand the (in)significance of the studied DOE variables, which was not possible based on the LD data as this technique only supplied end granule size information. The variation in tapped density and Hausner ratio among the end granules of the different DOE batches could be explained by their difference in average end granule size. Univariate, multivariate PLS and multiway N-PLS models were built to relate these end granule properties to the in-line-measured particle size distribution. The multivariate PLS tapped density model and the multiway N-PLS Hausner ratio model showed the highest R(2) values in combination with the lowest RMSEE values (R(2) of 82% with an RMSEE of 0.0279 for tapped density and an R(2) of 52% with an RMSEE of 0.0268 for Hausner ratio, respectively). 2010 Elsevier B.V. All rights reserved.

  20. Estimating surface turbulent heat fluxes from land surface temperature and soil moisture observations using the particle batch smoother

    Science.gov (United States)

    Lu, Yang; Dong, Jianzhi; Steele-Dunne, Susan C.; van de Giesen, Nick

    2016-11-01

    Surface heat fluxes interact with the overlying atmosphere and play a crucial role in meteorology, hydrology, and climate change studies, but in situ observations are costly and difficult. It has been demonstrated that surface heat fluxes can be estimated from assimilation of land surface temperature (LST). One approach is to estimate a neutral bulk heat transfer coefficient (CHN) to scale the sum of turbulent heat fluxes, and an evaporative fraction (EF) that represents the partitioning between fluxes. Here the newly developed particle batch smoother (PBS) is implemented. The PBS makes no assumptions about the prior distributions and is therefore well-suited for non-Gaussian processes. It is also particularly advantageous for parameter estimation by tracking the entire prior distribution of parameters using Monte Carlo sampling. To improve the flux estimation on wet or densely vegetated surfaces, a simple soil moisture scheme is introduced to further constrain EF, and soil moisture observations are assimilated simultaneously. This methodology is implemented with the FIFE 1987 and 1988 data sets. Validation against observed fluxes indicates that assimilating LST using the PBS significantly improves the flux estimates at both daily and half-hourly timescales. When soil moisture is assimilated, the estimated EFs become more accurate, particularly when the surface heat flux partitioning is energy-limited. The feasibility of extending the methodology to use remote sensing observations is tested by limiting the number of LST observations. Results show that flux estimates are greatly improved after assimilating soil moisture, particularly when LST observations are sparse.

  1. High-latitude electromagnetic and particle energy flux during an event with sustained strongly northward IMF

    Directory of Open Access Journals (Sweden)

    H. Korth

    2005-06-01

    Full Text Available We present a case study of a prolonged interval of strongly northward orientation of the interplanetary magnetic field on 16 July 2000, 16:00-19:00 UT to characterize the energy exchange between the magnetosphere and ionosphere for conditions associated with minimum solar wind-magnetosphere coupling. With reconnection occurring tailward of the cusp under northward IMF conditions, the reconnection dynamo should be separated from the viscous dynamo, presumably driven by the Kelvin-Helmholtz (KH instability. Thus, these conditions are also ideal for evaluating the contribution of a viscous interaction to the coupling process. We derive the two-dimensional distribution of the Poynting vector radial component in the northern sunlit polar ionosphere from magnetic field observations by the constellation of Iridium satellites together with drift meter and magnetometer observations from the Defense Meteorological Satellite Program (DMSP F13 and F15 satellites. The electromagnetic energy flux is then compared with the particle energy flux obtained from auroral images taken by the far-ultraviolet (FUV instrument on the Imager for Magnetopause to Aurora Global Exploration (IMAGE spacecraft. The electromagnetic energy input to the ionosphere of 51 GW calculated from the Iridium/DMSP observations is eight times larger than the 6 GW due to particle precipitation all poleward of 78° MLAT. This result indicates that the energy transport is significant, particularly as it is concentrated in a small region near the magnetic pole, even under conditions traditionally considered to be quiet and is dominated by the electromagnetic flux. We estimate the contributions of the high and mid-latitude dynamos to both the Birkeland currents and electric potentials finding that high-latitude reconnection accounts for 0.8 MA and 45kV while we attribute <0.2MA and ~5kV to an interaction at lower latitudes having the sense of a viscous interaction. Given that these

  2. A Theory for Self-consistent Acceleration of Energetic Charged Particles by Dynamic Small-scale Flux Ropes

    Science.gov (United States)

    le Roux, J. A.; Zank, G. P.; Khabarova, O.; Webb, G. M.

    2016-12-01

    Simulations of charged particle acceleration in turbulent plasma regions with numerous small-scale contracting and merging (reconnecting) magnetic islands/flux ropes emphasize the key role of temporary particle trapping in these structures for efficient acceleration that can result in power-law spectra. In response, a comprehensive kinetic transport theory framework was developed by Zank et al. and le Roux et al. to capture the essential physics of energetic particle acceleration in solar wind regions containing numerous dynamic small-scale flux ropes. Examples of test particle solutions exhibiting hard power-law spectra for energetic particles were presented in recent publications by both Zank et al. and le Roux et al.. However, the considerable pressure in the accelerated particles suggests the need for expanding the kinetic transport theory to enable a self-consistent description of energy exchange between energetic particles and small-scale flux ropes. We plan to present the equations of an expanded kinetic transport theory framework that will enable such a self-consistent description.

  3. Coefficient of solid-gas heat transfer in particle fixed bed; Coeficiente de transferencia de calor gas-solido em leito fixo de particulas

    Energy Technology Data Exchange (ETDEWEB)

    Fernandes Filho, Francisco

    1991-03-01

    The work presents a study on heat transfer between gas and solid phases for fixed beds in the absence of mass transfer and chemical reactions. Mathematical models presented in the literature were analyzed concerning to the assumptions made on axial dispersion in the fluid phase and interparticle thermal conductivity. Heat transfer coefficients and their dependency on flow conditions, particles and packed bed characteristics were experimentally determined through the solution of the previous mathematical models. Pressure drop behaviour for the packed beds used for the heat transfer study was also included. (author) 32 refs., 12 figs.

  4. Influence of catalyst dilution by inert particles on the effectivity of a catalytical process in a fluidized bed. [Increasing selectivity by decreasing local reaction kinetics

    Energy Technology Data Exchange (ETDEWEB)

    Augenblick, A.A. (Karpov Physico-Chemical Inst., Moscow, USSR); Kernerman, V.A.; Abayev, G.N.; Slin' ko, M.G.; Sergeev, Yu.A.

    1983-01-01

    The method of the increasing a selectivity of catalytic processes in fluidized bed reactor by decreasing local chemical reaction rates together with increasing a reactive volume is discussed. Based on the two-phase model of a fluidized bed it is shown that the dilution of a catalyst by inert particles leads to an increasing of effective interphase exchange coefficients and a decreasing of effective axial mixing coefficients. Restrictions to applications of the method connected with local features of a bed structure are discussed. 3 figures.

  5. Electron heating and particle fluxes in dual frequency atmospheric-pressure helium capacitive discharge

    Science.gov (United States)

    Liu, Dingxin; Yang, Aijun; Wang, Xiaohua; Chen, Chen; Rong, Mingzhe; Kong, Michael G.

    2016-12-01

    In this letter, a 1D fluid model has been used to study the electron heating and particle transport in dual frequency atmospheric-pressure helium capacitive discharge with a high-frequency (HF) voltage of 10 MHz and a low-frequency (LF) voltage of 1 MHz. The electric field is decoupled to three components: the HF, the LF and the direct current (DC) ones, and they have much different effects on the plasmas. The eletrons in plasma bulk are mainly heated by the HF electric field, while in plasma sheath they are heated and cooled by the LF and DC electric fields, respectively. With a fixed total input power, the increase of LF power leads to great enhancement of the electrode fluxes of electrons and ions, especially for the energetic electrons of T e  >  2 eV, because more power is dissipated in the vicinity of electrodes and the inelastic collision is more pronounced. Therefore, the particle transport on the treated sample can be greatly enhanced without additional gas heating in dual frequency plasmas, which meets the application requirements more compared to the single frequency plasmas.

  6. Impurity identifications, concentrations and particle fluxes from spectral measurements of the EXTRAP T2R plasma

    Science.gov (United States)

    Menmuir, S.; Kuldkepp, M.; Rachlew, E.

    2006-10-01

    An absolute intensity calibrated 0.5 m spectrometer with optical multi-channel analyser detector was used to observe the visible-UV radiation from the plasma in the EXTRAP T2R reversed field pinch experiment. Spectral lines were identified indicating the presence of oxygen, chromium, iron and molybdenum impurities in the hydrogen plasma. Certain regions of interest were examined in more detail and at different times in the plasma discharge. Impurity concentration calculations were made using the absolute intensities of lines of OIV and OV measured at 1-2 ms into the discharge generating estimates of the order of 0.2% of ne in the central region rising to 0.7% of ne at greater radii for OIV and 0.3% rising to 0.6% for OV. Edge electron temperatures of 0.5-5 eV at electron densities of 5-10×1011 cm-3 were calculated from the measured relative intensities of hydrogen Balmer lines. The absolute intensities of hydrogen lines and of multiplets of neutral chromium and molybdenum were used to determine particle fluxes (at 4-5 ms into the plasma) of the order 1×1016, 7×1013 and 3×1013 particles cm-2 s-1, respectively.

  7. Particle fluxes in the NW Iberian coastal upwelling system: Hydrodynamical and biological control

    Science.gov (United States)

    Zúñiga, D.; Villacieros-Robineau, N.; Salgueiro, E.; Alonso-Pérez, F.; Rosón, G.; Abrantes, F.; Castro, C. G.

    2016-07-01

    To better understand sources and transport of particulate material in the NW Iberian coastal upwelling system, a mooring line dotted with an automated PPS 4/3 sediment trap was deployed off Cape Silleiro at the base of the photic zone. The samples were collected from November 2008 through June 2012 over sampling periods of 4-12 days. Our study represents the first automated sediment trap database for the NW Iberian margin. The magnitude and composition of the settling material showed strong seasonal variability with the highest fluxes during the poleward and winter mixing periods (averages of 12.9±9.6 g m-2 d-1 and 5.6±5.6 g m-2 d-1 respectively), and comparatively lower fluxes (3.6±4.1 g m-2 d-1) for the upwelling season. Intensive deposition events registered during poleward and winter mixing periods were dominated by the lithogenic fraction (80±3%). They were associated to high energy wave-driven resuspension processes, due to the occurrence of south-westerly storms, and intense riverine inputs of terrestrial material from Minho and Douro rivers. On the other hand, during the spring - summer upwelling season, the share of biogenic compounds (organic matter, calcium carbonate (CaCO3), biogenic silica (bSiO2)) to downward fluxes was higher, reflecting an increase in pelagic sedimentation due to the seasonal intensification of primary production and negligible river inputs and wave-driven resuspended material. Otherwise, the large variations of biogenic settling particles were mainly modulated by upwelling intensity, which by means of upwelling filaments ultimately controlled the offshore transport of the organic carbon fixed by primary producers towards the adjacent ocean. Based on the average downward flux of organic carbon (212 mg C m-2 d-1) and considering an average primary production of 1013 mg C m-2 d-1 from literature, we estimated that about 21% of the fixed carbon is vertically exported during the upwelling season.

  8. Experimental research of the influence of particle size and fluidization velocity on zeolite drying in a two-component fluidized bed

    Directory of Open Access Journals (Sweden)

    Janevski Jelena N.

    2016-01-01

    Full Text Available This paper presents the results of the kinetics research into the drying of fine grained material in a two-component fluidized bed. A review of theoretical and experimental investigations of aerodynamics of the fluidized bed is given, with a special insight into two-component fluidized beds, as well as the basics of heat and material transfer through a fluidized bed. Apart from the theoretical basis of convective drying of wet materials in a stagnant fluidized bed, the paper also emphasizes different approaches to fine grained material drying kinetics. Based on the experimental investigations, where zealots used as a representative of fine grained material and polyethylene as a representative of inert material (another component, an analysis of the influence of working parameters on drying in a two-component fluidized bed is performed. It is established that, apart from the influence of the considered parameters, such as fluidization velocity, diameter of fine grained material particles and drying agent temperature, on the drying curve, the participation of inert material can considerably increase the intensity of heat and material transfer in the fluidized bed. A comparison of the experimental drying curves of fine grained material in the two-component fluidized bed with the results from the studies by other authors shows satisfactory agreement.

  9. Influences of Temperature and Coal Particle Size on the Flash Pyrolysis of Coal in a Fast-entrained Bed

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The experiments on the flash pyrolysis of a lignite were carried out in a fast-entrained bed reactor as a basic study on a so-called 'coal topping process'. The investigation focused on the effects of pyrolysis temperature and coal particle size on the product distribution and composition. The experimental results show that an increase in the pyrolysis temperature results in a higher yield of gaseous products while a larger particle size leads to a decrease of the liquid yield. An optimum temperature for the liquid yield was found to be 650 ℃. A certain amount of phenol groups was found in the liquid products, which may be used to produce high-valued fine chemicals. The FTIR analyses of the coal and chars show that aliphatic structures in the chars are gradually replaced by aromatic structures with the increasing of pyrolysis temperature and coal particle size. The results of this study provide fundamental data and optimal conditions to maximize light oils yields for the coal topping process.

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

    DEFF Research Database (Denmark)

    Hansen, Kim Granly

    shows good agreement. The 3D representation of the reactor geometry gives better predictions of the radial variation in concentration than in a similar 2D simulation, Samuelsberg and Hjertager (1995). A parameter study is performed to investigate improvements in the predicted pressure drop profile. When...... 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...

  11. Experimental investigation of CO{sub 2} capture using sodium hydroxide particles in a fluidized bed

    Energy Technology Data Exchange (ETDEWEB)

    Naeem, Sareh; Ghaemi, Ahad; Shahhosseini, Shahrokh [Iran University of Science and Technology (IUST), Tehran (Iran, Islamic Republic of)

    2016-04-15

    CO{sub 2} capture from air using sodium hydroxide solid sorbent in a laboratory scale fluidized bed reactor was investigated experimentally. The influence of three parameters of temperature, inlet CO{sub 2} volume percentage and inlet air flow rate on the CO{sub 2} removal rate was studied. Experimental results showed that the optimum rate was at 25 oC when the inlet CO{sub 2} volume percentage was 1%. The results also showed that the adsorption process was reactive, and the reaction mechanism depended on the reaction temperature. In addition, empirical observation revealed only one adsorption cycle happened at low temperatures (25-30 oC). As the temperature increased, the second adsorption cycle occurred and, finally, CO{sub 2} desorption cycle took place in the range of 90-115 .deg. C.

  12. Numerical Simulation of Particle Flow Motion in a Two-Dimensional Modular Pebble-Bed Reactor with Discrete Element Method

    Directory of Open Access Journals (Sweden)

    Guodong Liu

    2013-01-01

    Full Text Available Modular pebble-bed nuclear reactor (MPBNR technology is promising due to its attractive features such as high fuel performance and inherent safety. Particle motion of fuel and graphite pebbles is highly associated with the performance of pebbled-bed modular nuclear reactor. To understand the mechanism of pebble’s motion in the reactor, we numerically studied the influence of number ratio of fuel and graphite pebbles, funnel angle of the reactor, height of guide ring on the distribution of pebble position, and velocity by means of discrete element method (DEM in a two-dimensional MPBNR. Velocity distributions at different areas of the reactor as well as mixing characteristics of fuel and graphite pebbles were investigated. Both fuel and graphite pebbles moved downward, and a uniform motion was formed in the column zone, while pebbles motion in the cone zone was accelerated due to the decrease of the cross sectional flow area. The number ratio of fuel and graphite pebbles and the height of guide ring had a minor influence on the velocity distribution of pebbles, while the variation of funnel angle had an obvious impact on the velocity distribution. Simulated results agreed well with the work in the literature.

  13. Characteristics of ash and particle emissions during bubbling fluidised bed combustion of three types of residual forest biomass.

    Science.gov (United States)

    Ribeiro, João Peres; Vicente, Estela Domingos; Alves, Célia; Querol, Xavier; Amato, Fulvio; Tarelho, Luís A C

    2017-04-01

    Combustion of residual forest biomass (RFB) derived from eucalypt (Eucalyptus globulus), pine (Pinus pinaster) and golden wattle (Acacia longifolia) was evaluated in a pilot-scale bubbling fluidised bed reactor (BFBR). During the combustion experiments, monitoring of temperature, pressure and exhaust gas composition has been made. Ash samples were collected at several locations along the furnace and flue gas treatment devices (cyclone and bag filter) after each combustion experiment and were analysed for their unburnt carbon content and chemical composition. Total suspended particles (TSP) in the combustion flue gas were evaluated at the inlet and outlet of cyclone and baghouse filter and further analysed for organic and elemental carbon, carbonates and 57 chemical elements. High particulate matter collection efficiencies in the range of 94-99% were observed for the baghouse, while removal rates of only 1.4-17% were registered for the cyclone. Due to the sand bed, Si was the major element in bottom ashes. Fly ashes, in particular those from eucalypt combustion, were especially rich in CaO, followed by relevant amounts of SiO2, MgO and K2O. Ash characteristics varied among experiments, showing that their inorganic composition strongly depends on both the biomass composition and combustion conditions. Inorganic constituents accounted for TSP mass fractions up to 40 wt%. Elemental carbon, organic matter and carbonates contributed to TSP mass fractions in the ranges 0.58-44%, 0.79-78% and 0.01-1.7%, respectively.

  14. Bathypelagic particle flux signatures from a suboxic eddy in the oligotrophic tropical North Atlantic: production, sedimentation and preservation

    Science.gov (United States)

    Fischer, Gerhard; Karstensen, Johannes; Romero, Oscar; Baumann, Karl-Heinz; Donner, Barbara; Hefter, Jens; Mollenhauer, Gesine; Iversen, Morten; Fiedler, Björn; Monteiro, Ivanice; Körtzinger, Arne

    2016-06-01

    Particle fluxes at the Cape Verde Ocean Observatory (CVOO) in the eastern tropical North Atlantic for the period December 2009 until May 2011 are discussed based on bathypelagic sediment trap time-series data collected at 1290 and 3439 m water depth. The typically oligotrophic particle flux pattern with weak seasonality is modified by the appearance of a highly productive and low oxygen (minimum concentration below 2 µmol kg-1 at 40 m depth) anticyclonic modewater eddy (ACME) in winter 2010. The eddy passage was accompanied by unusually high mass fluxes of up to 151 mg m-2 d-1, lasting from December 2009 to May 2010. Distinct biogenic silica (BSi) and organic carbon flux peaks of ˜ 15 and 13.3 mg m-2 d-1, respectively, were observed in February-March 2010 when the eddy approached the CVOO. The flux of the lithogenic component, mostly mineral dust, was well correlated with that of organic carbon, in particular in the deep trap samples, suggesting a tight coupling. The lithogenic ballasting obviously resulted in high particle settling rates and, thus, a fast transfer of epi-/meso-pelagic signatures to the bathypelagic traps. We suspect that the two- to three-fold increase in particle fluxes with depth as well as the tight coupling of mineral dust and organic carbon in the deep trap samples might be explained by particle focusing processes within the deeper part of the eddy. Molar C : N ratios of organic matter during the ACME passage were around 18 and 25 for the upper and lower trap samples, respectively. This suggests that some productivity under nutrient (nitrate) limitation occurred in the euphotic zone of the eddy in the beginning of 2010 or that a local nitrogen recycling took place. The δ15N record showed a decrease from 5.21 to 3.11 ‰ from January to March 2010, while the organic carbon and nitrogen fluxes increased. The causes of enhanced sedimentation from the eddy in February/March 2010 remain elusive, but nutrient depletion and/or an increased

  15. A "test of concept" comparison of aerodynamic and mechanical resuspension mechanisms for particles deposited on field rye grass ( Secale cercele). Part 1. Relative particle flux rates

    Science.gov (United States)

    Gillette, Dale A.; Lawson, Robert E.; Thompson, Roger S.

    Resuspension of uniform latex micro spheres deposited on a single seed pod of field rye grass stalk and head was investigated experimentally in a wind tunnel. The experiment was designed to distinguish aerodynamic (viscous and turbulent) mechanisms from mechanical resuspension resulting from the oscillatory impact of the grass hitting a stationary object. The experiment was run for deposited spherical latex particles with diameters from 2 to 10 μm. Wind tunnel tests were run for wind speeds from 2 to 18.5 m s -1 and a turbulence intensity (root-mean-square fluctuation wind speed/mean wind speed) of 0.1. Our experiments showed the following for our test of concept experiment: Resuspension particle flux increases when mechanical impacts occur. Mechanical resuspension dominated for 2 μm particles over purely aerodynamic resuspension, but for larger particles aerodynamic mechanisms were roughly equally effective in resuspending particles.

  16. Spatial and temporal variability of Alexandrium cyst fluxes in the Gulf of Maine: Relationship to seasonal particle export and resuspension

    Science.gov (United States)

    Pilskaln, C. H.; Anderson, D. M.; McGillicuddy, D. J.; Keafer, B. A.; Hayashi, K.; Norton, K.

    2014-05-01

    Quantification of Alexandrium cyst fluxes through the Gulf of Maine water column is central to understanding the linkage between the source and fate of annual Alexandrium blooms in the offshore waters. These blooms often lead to paralytic shellfish poisoning (PSP) and extensive closures of shellfish beds. We report here on time-series sediment trap deployments completed at four offshore locations in the gulf between 2005 and 2010 as components of two ECOHAB-GOM field programs. Data presented documents the substantial spatial and temporal fluctuations in Alexandrium fundyense cyst fluxes in the gulf. Cyst delivery out of the euphotic zone peaked primarily between July and August following annual spring-summer Alexandrium blooms and was greatest in the western gulf. At all sites, cyst flux maxima to the subsurface waters were rarely coincident with seasonal peaks in the total mass export of particulate material indicating that cyst delivery was primarily via individually sinking cysts. Where persistent benthic nepheloid layers (BNLs) exist, significant sediment resuspension input of cysts to the near-bottom water column was evidenced by deep cyst fluxes that were up to several orders of magnitude greater than that measured above the BNL. The largest cyst fluxes in the BNL were observed in the eastern gulf, suggesting greater resuspension energy and BNL cyst inventories in this region. Temporal similarities between peak cyst export out of the upper ocean and peak cyst fluxes in the BNL were observed and document the contribution of seasonal, newly formed cysts to the BNL. The data however also suggest that many Alexandrium cells comprising the massive, short-lived blooms do not transition into cysts. Time-series flow measurements and a simple 1D model demonstrate that the BNL cyst fluxes reflect the combined effects of tidal energy-maintained resuspension, deposition, and input of cysts from the overlying water column.

  17. Flux and accumulation of sedimentary particles off the continental slope of Pakistan: a comparison of water column and seafloor estimates from the oxygen minimum zone, NE Arabian Sea

    Directory of Open Access Journals (Sweden)

    H. Schulz

    2013-07-01

    Full Text Available Due to the lack of bioturbation, the laminated muds from the oxygen-minimum zone (OMZ off Pakistan provide a unique opportunity to precisely determine the vertical and lateral sediment fluxes in the near shore part of the northeastern Arabian Sea, and to explore the effects of the margin topography and the low oxygen conditions on the accumulation of organic matter and other particles. West of Karachi, in the Hab river area of EPT and WPT (Eastern and Western PAKOMIN Traps, 16 short sediment profiles from water depths between 250 m and 1970 m on a depth transect crossing the OMZ (~ 120 to ~ 1200 m water depth were investigated, and correlated on the basis of a thick, light-gray- to reddish-colored turbidite layer. Varve counting yielded a date for this layer of AD 1905 to 1888. We adopted the young age which agrees with 210Pb- dating, and used this isochronous stratigraphic marker bed to calculate sediment accumulation rates, that we could directly compare with the flux rates from the sediment traps installed within the water column above. All traps in the area show exceptionally high, pulsed winter fluxes of up to 5000 mg m−2 d−1 in this margin environment. The lithic flux at the sea floor is as high as 4000 mg m−2 d−1 , and agrees remarkably well with the bulk winter flux of material. This holds as well for the individual bulk components (organic carbon, calcium carbonate, opal, lithic fraction. However, the high winter flux events (HFE by their extreme mass of remobilized matter terminated the recording in the shallow traps by clogging the funnels. Based on our comparisons, we argue that HFE for the past 5000 yr most likely occurred as regular events within the upper OMZ off Pakistan. Coarse fraction and foraminiferal accumulation rates from sediment surface samples along the Hab transect show distribution patterns that seem to be a function of water depth and distance from the shelf. Some of these sediment fractions show sudden

  18. Radiation phenomena and particle fluxes in the X-event in JET

    Energy Technology Data Exchange (ETDEWEB)

    Jaeckel, H.J.; Bartlett, D.V.; Falter, H.; Lingertat, J.; Reichle, R. [Commission of the European Communities, Abingdon (United Kingdom). JET Joint Undertaking

    1994-07-01

    The radiation build-up and the particle fluxes in the phase, immediately preceding the X-event, has been studied bolometrically and using spectroscopy. The results show that the H-mode phase in high performance discharges tends to collapse irreversibly. The (calculated) target temperature just before the X-event amounts to about 1400 C. Any deterioration of confinement at this temperature leads to run-away conditions of the target temperature and a final fall-back into L-mode. Possible causes of the confinement deterioration are: MHD activities can cause a fast plasma loss and, hence, a power flash, dumped on the divertor target, leading to a temperature jump of up to 1000 C; enhanced recycling, due to thermal release of trapped deuterium from the graphite target plates causes an effective plasma edge cooling; loose graphite on the target tiles with virtually no thermal coupling to the target bulk can be sublimated and ejected into the main plasma with even small power levels. An active cooling, keeping the bulk target at ambient temperature could make the discharge more resilient against even medium MHD instabilities, as e.g. giant ELMs. 5 refs., 4 figs.

  19. Template-particle stabilized bicontinuous emulsion yielding controlled assembly of hierarchical high-flux filtration membranes.

    Science.gov (United States)

    Hess, Samuel C; Kohll, A Xavier; Raso, Renzo A; Schumacher, Christoph M; Grass, Robert N; Stark, Wendelin J

    2015-01-14

    A novel solvent-evaporation-based process that exploits template-particle stabilized bicontinuous emulsions for the formation of previously unreached membrane morphologies is reported in this article. Porous membranes have a wide range of applications spanning from water filtration, pharmaceutical purification, and battery separators to scaffolds for tissue engineering. Different situations require different membrane morphologies including various pore sizes and pore gradients. However, most of the previously reported membrane preparation procedures are restricted to specific morphologies and morphology alterations require an extensive optimization process. The tertiary system presented in this article, which consists of a poly(ether sulfone)/dimethylacetamide (PES/DMAc) solution, glycerol, and ZnO-nanoparticles, allows simple and exact tuning of pore diameters ranging from sub-20 nm, up to 100 nm. At the same time, the pore size gradient is controlled from 0 up to 840%/μm yielding extreme asymmetry. In addition to structural analysis, water flux rates of over 5600 L m(-2) h(-1) are measured for membranes retaining 45 nm silica beads.

  20. Removal of SO2 with particles of dolomite limestone powder in a binary fluidized bed reactor with bubbling fluidization

    Directory of Open Access Journals (Sweden)

    R. Pisani Jr.

    2003-06-01

    Full Text Available In this work, SO2 was treated by reaction with dolomite limestone (24 µm in a fluidized bed reactor composed of 500-590 µm sand particles. The influence of operating temperature (500, 600, 700 and 800ºC, superficial gas velocity (0.8, 1.0 and 1.2 m/s and Ca/S molar ratio (1, 2 and 3 on SO2 removal efficiency for an inlet concentration of 1000 ppm was examined. Removal of the pollutant was found to be dependent on temperature and Ca/S molar ratio, particularly at 700 and 800ºC. A maximum removal of 76% was achieved at a velocity of 0.8 m/s, a temperature of 800°C and a Ca/S of 3. The main residence time of the powder particles was determined by integrating normalized gas concentration curves as a function of time; the values found ranged from 4.1 to 14.4 min. It was concluded that the reactor operated in bubbling fluidization under every operational condition.

  1. A complete multi-scale simulation of light absorption within a fluidized bed photoreactor using integrated particle, fluid and photon behaviour models.

    Science.gov (United States)

    Braham, R J; Harris, A T

    2013-08-07

    Photocatalysis is a process that offers the ability to degrade a wide range of pollutants through a non-intensive process using renewable light sources. Despite this promise, in practice the take-up of photocatalysis has been slow, in part because little work has been done on the optimal design of photocatalytic reactors. The use of fluidized beds for photocatalytic applications has many advantages through their high illuminated surface area, reduced mass transfer constraints and retention of the photocatalyst. However this photoreactor design has received little attention compared to other possible designs, especially in regards to modelling and simulation. The models that have been developed simplify the behaviour of the fluidized bed, and in doing so lose much of the dynamic behaviour of the system that would be present in most realistic operations. This report details the development of a fully simulated fluidized bed photoreactor, where the movement of the particle and fluid phases was determined by discrete element modelling and computational fluid dynamics, respectively, and the behaviour of the photons was modelled using geometric optics. The accuracy of the model was assessed comparing it to the light transmitted through an experimental fluidized bed. Previously unreported photon absorption behaviour was found, particularly in regards to how the photons are absorbed throughout the space. At lower heights of the bed the photons are overwhelmingly absorbed at the walls of the reaction volume, while higher up the bed there is a broad zone of relatively even absorption throughout the entire space. This has implications for the design of this class of reactor. Two possible fluidized bed photoreactor designs are discussed based on this effect, one having a very small reaction volume and having a very dense particle phase, while the other has large reaction volume with a more distributed particle phase.

  2. Development and Optimization of AAV hFIX Particles by Transient Transfection in an iCELLis(®) Fixed-Bed Bioreactor.

    Science.gov (United States)

    Powers, Alicia D; Piras, Bryan A; Clark, Robert K; Lockey, Timothy D; Meagher, Michael M

    2016-06-01

    Adeno-associated virus (AAV) vectors are increasingly popular in gene therapy because they are unassociated with human disease, replication dependent, and less immunogenic than other viral vectors and can infect a variety of cell types. These vectors have been used in over 130 clinical trials, and one AAV product has been approved for treatment of lipoprotein lipase deficiency in Europe. To meet the demand for the increasing quantities of AAV required for clinical trials and treatment, a scalable high-capacity technology is required. Bioreactors meet these requirements but limited options are available for adherent HEK 293T/17 cells. Here we optimize the transient transfection of HEK293T/17 cells for the production of AAV human factor IX in a disposable fixed-bed bioreactor, the iCELLis(®) Nano (PALL Corporation). A fixed bed in the center of the iCELLis bioreactor is surrounded by culture medium that is pumped through the bed from the bottom of the bioreactor so that a thin film of the medium overflows the bed and is replenished with oxygen and depleted of CO2 as it returns to the surrounding medium reservoir. We show that this fixed-bed bioreactor can support as many as 2.5 × 10(8) cells/ml of fixed bed (1.9 × 10(6) cells/cm(2)). By optimizing culture and transfection parameters such as the concentration of DNA for transfection, day of harvest, size of PEI/DNA particles, and transfection medium, and adding an additional medium change to the process, we increased our yield to as high as 9.0 × 10(14) viral particles per square meter of fixed bed. We also show an average GFP transfection of 97% of cells throughout the fixed bed. These yields make the iCELLis a promising scalable technology for the clinical production of AAV gene therapy products.

  3. Two-flux method for radiation heat transfer in anisotropic gas-particles media

    Institute of Scientific and Technical Information of China (English)

    2004-01-01

    [1]Schuster, A., Radiation through a foggy atmosphere, Astrophysics J., 1905, 21(1): 1-22.[2]Schwarzchild, K., Equilibrium of the Sun's atmosphere, Nachr. Ges. Wiss. Gottingen Math.-Phys. Klasse, 1906, (1): 41-53.[3]Maheu, B., Letoulouzan, J. N., Gouesbet, G., Four-flux models to solve the scattering transfer equation in terms of Loren-Mie parameters, Applied Optics, 1984, 23(19): 3353-3362.[4]Maheu, B., Gouesbet, G., Four-flux models to solve the scattering transfer equation: special cases, Applied Optics, 1986, 25(7): 1122-1128.[5]Roze, C., Girasole, T., Tafforin, A. G., Multiplayer four-flux model of scattering, emitting and absorbing media, Atmospheric Environment, 2001, 35: 5125-5130.[6]Modest, M. F., Radiative Heat Transfer, New York: McGraw-Hill Series in Mechanical Engineering, 1993.[7]Goodwin, D. G., Mitchner, M., Flyash radiative properties and effects on radiative heat transfer in coal-fired systems, International Journal of Heat and Mass Transfer, 1989, 32(4): 627-638.[8]Siegel, R., Howell, J. R., Thermal Radiation Heat Transfer, 2nd ed., New York: Hemisphere Publishing Corporation, 1980.[9]Irvine, T. F., Hartnett, J. P., Advances in Heat Transfer, Vol. 3, New York: Academic Press, 1966.[10]Rozé, C., Girasole, T., Grehan, G. et al., Average crossing parameter and forward scattering ratio values in four-flux model for multiple scattering media, Optics Communication, 2001, 194: 251-263.[11]Wall, T. F., Lowe, A., Wibberley, L. J. et al., Fly ash characteristics and radiative heat transfer in pulverized-coal-fired furnace, Combustion Science and Technology, 1981, 26: 107-121.[12]Ozisik, M. N., Radiative Transfer and Interactions with Conduction and Convection, New York: Wiley, 1973.[13]Gupta, R. P., Wall, T. F., Truelove, J. S., Radiative scatter by fly ash in pulverized-coal-fired furnace: application of the Monte Carlo method to anisotropic scatter, International Journal of Heat and Mass Transfer, 1983

  4. 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.

  5. Kinetic theory of rough spherical particles and numerical simulation of gas-solids flow in fluidiled bed%粗糙颗粒动理学及流化床内气固流动的数值模拟

    Institute of Scientific and Technical Information of China (English)

    陈巨辉; 杜小丽; 孙立岩; 徐鹏飞; 郝振华; 陆慧林

    2011-01-01

    Particle rotation, which has been less considered in particle kinetic model, plays an important role in gas-solids flow. Kinetic theory of rough spherical particles was proposed on the basis of kinetic theory of gases and kinetic theory of granular flow with the consideration of energy transport and dissipation by collision of particles. The models for solids phase stress, thermal flux and collisional energy dissipations of particles were presented by using Chapman-Enskog velocity distributions. Flow behavior of gas and particles was simulated by gas-solids two-phase flow model in a bubbling fluidized bed. Predicted velocity distribution and fluctuating velocity of particles were in agreement with experimental data measured by Yuu et al (2000) in a bubbling fluidized bed. The distribution of granular temperature,changing with concentration tended to be similar with the prediction by kinetic theory of granular flow. The effect of tangential restitution coefficient on fluctuating energy of particles was analyzed. Simulated results showed that at a low concentration of particles the fluctuating kinetic energy of particles increased with increasing tangential restitution coefficient.%基于气体分子动理学和颗粒动理学理论,考虑颗粒旋转流动对颗粒碰撞能量交换和耗散的影响,建立粗糙颗粒动理学.采用Chapman-Enskog颗粒速度分布函数,提出了颗粒相应力、热通量和颗粒碰撞能量耗散计算模型.采用欧拉一欧拉气固双相流模型,数值模拟鼓泡流化床内气体一颗粒两相流动特性.模拟结果得到了床内颗粒相速度和脉动速度分布,与Yuu等实验结果相吻合.分析不同的切向弹性恢复系数对颗粒相拟总温的变化规律,结果表明在低颗粒浓度时颗粒拟总温随切向弹性恢复系数而增加.

  6. Experimental analysis of minimum shear stress to drag particles in a horizontal bed; Analise experimental da tensao de cisalhamento minima para arraste de particulas em um leito horizontal

    Energy Technology Data Exchange (ETDEWEB)

    Dornelas, Breno Almeida; Soares, Edson Jose [Universidade Federal do Espirito Santo. Departamento de Engenharia Mecanica (Brazil)], e-mails: bad@ucl.br, edson@ct.ufes.br; Quirino Filho, Joao Pedro; Loureiro, Bruno Venturini [Faculdade do Centro Leste (UCL). Laboratorio de Fluidos e Fenomenos de Transporte (Brazil)], e-mails: joaoquirino@ucl.br, brunovl@ucl.br

    2009-12-15

    Efficient hole cleaning is still a challenge in well bore drilling to produce oil and gas. The critical point is the horizontal drilling that inherently tends to form a bed of sediment particles at the well bottom during drilling. The cuttings bed erosion depends mainly on the shear stress promoted by the drilling fluid flow. The shear stress required to cause drag in the cuttings bed is investigated according to the fluid and particles properties, using an experimental assembly, composed of: a system for fluid circulation, a particle box, a pump system and measuring equipment. The observation area is a box below the flow line in an acrylic duct used to calibrate sand particles. The test starts with the pumps in a low frequency which is increased in steps. At each frequency level, images are captured of carried particles and the established flow rate is recorded. The images are analyzed when the dragged particle is no longer random and sporadic, but becomes permanent. The shear stress is identified by the PKN correlation (by Prandtl, von Karman, and Nikuradse) for the minimum flow rate necessary to cause drag. Results were obtained for just water and water-glycerin solution flows. (author)

  7. Operational parameters and their influence on particle-side mass transfer resistance in a packed bed bioreactor.

    Science.gov (United States)

    Hussain, Amir; Kangwa, Martin; Yumnam, Nivedita; Fernandez-Lahore, Marcelo

    2015-12-01

    The influence of internal mass transfer on productivity as well as the performance of packed bed bioreactor was determined by varying a number of parameters; chitosan coating, flow rate, glucose concentration and particle size. Saccharomyces cerevisiae cells were immobilized in chitosan and non-chitosan coated alginate beads to demonstrate the effect on particle side mass transfer on substrate consumption time, lag phase and ethanol production. The results indicate that chitosan coating, beads size, glucose concentration and flow rate have a significant effect on lag phase duration. The duration of lag phase for different size of beads (0.8, 2 and 4 mm) decreases by increasing flow rate and by decreasing the size of beads. Moreover, longer lag phase were found at higher glucose medium concentration and also with chitosan coated beads. It was observed that by increasing flow rates; lag phase and glucose consumption time decreased. The reason is due to the reduction of external (fluid side) mass transfer as a result of increase in flow rate as glucose is easily transported to the surface of the beads. Varying the size of beads is an additional factor: as it reduces the internal (particle side) mass transfer by reducing the size of beads. The reason behind this is the distance for reactants to reach active site of catalyst (cells) and the thickness of fluid created layer around alginate beads is reduced. The optimum combination of parameters consisting of smaller beads size (0.8 mm), higher flow rate of 90 ml/min and glucose concentration of 10 g/l were found to be the maximum condition for ethanol production.

  8. On the Effective Thermal Conductivity of Porous Packed Beds with Uniform Spherical Particles

    Science.gov (United States)

    Kandula, Max

    2010-01-01

    Point contact models for the effective thermal conductivity of porous media with uniform spherical inclusions have been briefly reviewed. The model of Zehner and Schlunder (1970) has been further validated with recent experimental data over a broad range of conductivity ratio from 8 to 1200 and over a range of solids fraction up to about 0.8. The comparisons further confirm the validity of Zehner-Schlunder model, known to be applicable for conductivity ratios less than about 2000, above which area contact between the particles becomes significant. This validation of the Zehner-Schlunder model has implications for its use in the prediction of the effective thermal conductivity of water frost (with conductivity ratio around 100) which arises in many important areas of technology.

  9. Asymptotic gravitational wave fluxes from a spinning particle in circular equatorial orbits around a rotating black hole

    CERN Document Server

    Harms, Enno; Bernuzzi, Sebastiano; Nagar, Alessandro

    2015-01-01

    We present a new computation of the asymptotic gravitational wave energy fluxes emitted by a {\\it spinning} particle in circular equatorial orbits about a Kerr black hole. The particle dynamics is computed in the pole-dipole approximation, solving the Mathisson-Papapetrou equations with the Tulczyjew spin-supplementary-condition. The fluxes are computed, for the first time, by solving the 2+1 Teukolsky equation in the time-domain using hyperboloidal and horizon-penetrating coordinates. Denoting by $M$ the black hole mass and by $\\mu$ the particle mass, we cover dimensionless background spins $a/M=(0,\\pm0.9)$ and dimensionless particle spins $-0.9\\leq S/\\mu^2 \\leq +0.9$. Our results span orbits of Boyer-Lindquist coordinate radii $4\\leq r/M \\leq 30$; notably, we investigate the strong-field regime, in some cases even beyond the last-stable-orbit. We confirm, numerically, the Tanaka {\\it et al.} [Phys.\\ Rev.\\ D 54, 3762] 2.5th order accurate Post-Newtonian (PN) predictions for the gravitational wave fluxes of a...

  10. Whole-system metabolism and CO2 fluxes in a Mediterranean Bay dominated by seagrass beds (Palma Bay, NW Mediterranean

    Directory of Open Access Journals (Sweden)

    A. V. Borges

    2004-10-01

    Full Text Available The relationship between whole-system metabolism estimates based on planktonic and benthic incubations (bare sediments and seagrass, Posidonia oceanica meadows, and CO2 fluxes across the air-sea interface were examined in the Bay of Palma (Mallorca, Spain during two cruises in March and June 2002. Moreover, planktonic and benthic incubations were performed at monthly intervals from March 2001 to October 2002 in a seagrass vegetated area of the bay. From the annual study, results showed a contrast between the planktonic compartment, which was heterotrophic during most of the year, except for occasional bloom episodes, and the benthic compartment, which was slightly autotrophic. Whereas the seagrass community was autotrophic, the excess organic carbon production therein could only balance the excess respiration of the planktonic compartment in shallow waters (2 fields and fluxes across the bay observed during the two extensive cruises in 2002. Finally, dissolved inorganic carbon and oxygen budgets provided NEP estimates in fair agreement with those derived from direct metabolic estimates based on incubated samples over the Posidonia oceanica meadow.

  11. Estimation of particle velocity in moving beds based on a flow model for bulk solids. Ryudo model ni motozuita idoso no ryushi sokudo no suisan

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, H. (Muroran Inst. of Tech., Hokkaido (Japan)); Honda, Y. (Snow Brand Milk Products Co. Ltd., Sapporo (Japan))

    1992-11-10

    Based on a particle flow model (stress-shear strain velocity relational expression) which takes account of the bulk volume expansion effect during shearing deformation of particles, a new estimation method for particle velocity distribution and stress distribution is proposed. The method is applied to a crossflow moving bed and to a moving bed for comparison with the experimental values to examine its validity. The method is further extended to predict the velocity profile and stress profile of moving beds in a vertical tube (countercurrent and concurrent) accompanying gas flow. It is indicated that the bulk volume expansion effect differs according to dimensions. The velocity distribution and the stress distribution of flows in a vertical tube are greatly influenced by the nature of the flow, i.e. whether it is a counterflow or a concurrent flow, and the frictional force of solids on a wall surface increases markedly in a concurrent flow, which induces considerable lag of particle velocity. The parameter which is contained in the model and indicates the bulk volume expansion effect is a function of the particle velocity, and it is almost unaffected by the flow rate of gas moving. 7 refs., 10 figs.

  12. Crossed contributions to electron and heavy-particle transport fluxes for magnetized plasmas in the continuum regime

    Science.gov (United States)

    Scoggins, James B.; Knisely, Carleton P.; Magin, Thierry E.

    2016-11-01

    We propose a unified fluid model for multicomponent plasmas in thermal nonequilibrium accounting for the influence of the electromagnetic field. In a previous work, this model was derived from kinetic theory based on a generalized Chapman-Enskog perturbative solution of the Boltzmann equation, scaled using the ratio of electron to heavy-particle masses. Anisotropic transport properties were derived in terms of bracket integrals. In this work, explicit expressions for asymptotic solutions of the transport properties are derived using a spectral Galerkin projection supplied with Laguerre-Sonine polynomial basis functions, and we analyze the crossed contributions to electron and heavy particle mass and energy fluxes, known as the Kolesnikov effect.

  13. Framework to model neutral particle flux in convex high aspect ratio structures using one-dimensional radiosity

    Science.gov (United States)

    Manstetten, Paul; Filipovic, Lado; Hössinger, Andreas; Weinbub, Josef; Selberherr, Siegfried

    2017-02-01

    We present a computationally efficient framework to compute the neutral flux in high aspect ratio structures during three-dimensional plasma etching simulations. The framework is based on a one-dimensional radiosity approach and is applicable to simulations of convex rotationally symmetric holes and convex symmetric trenches with a constant cross-section. The framework is intended to replace the full three-dimensional simulation step required to calculate the neutral flux during plasma etching simulations. Especially for high aspect ratio structures, the computational effort, required to perform the full three-dimensional simulation of the neutral flux at the desired spatial resolution, conflicts with practical simulation time constraints. Our results are in agreement with those obtained by three-dimensional Monte Carlo based ray tracing simulations for various aspect ratios and convex geometries. With this framework we present a comprehensive analysis of the influence of the geometrical properties of high aspect ratio structures as well as of the particle sticking probability on the neutral particle flux.

  14. A Sedimentation-Dispersion Model for both Non-attached and Attached Particles in Three-Phase Batchwise Fluidized Beds

    Institute of Scientific and Technical Information of China (English)

    张济宇; 林诚; 林春深

    2002-01-01

    The axial concentration distribution of both particles with better wetting (forming non-attached system)and poorer wetting (forming attached system) was investigated in a vertical gas-liquid-solid fluidized bed of 4.2 cm indiameter and 130 cm in height with the solids holdup less than 0.05. The one-dimensional sedimentation-dispersionmodel could be used satisfactorily to describe the axial distribution of solids holdup by modifying only a modelparameter, i.e. by means of the terminal settling velocity minus a certain value, which is a function of gas velocityand considers the effect of an additional drag force resulted from attached rising bubbles. The axial profiles of solidconcentration predicted are in good agreement with experimental results. This model also explains reasonably thedifferent axial distributions of solid concentration, i.e. the solids holdup decreases as the axial height increases innon-attached system, but increases with the axial height in attached system at a given gas velocity.

  15. Particle flux during the southwest monsoon on the western margin of India

    Digital Repository Service at National Institute of Oceanography (India)

    Ramaswamy, V.

    of the collected particulate matter is reported here The result suggests that present-day sedimentation on the outer shelf is dominated by larger particle or particle aggregates, composed mainly of biogenic carbonates Clay minerals in the samples collected...

  16. Atomic force microscopy surface analysis of layered perovskite La2Ti2O7 particles grown by molten flux method

    Science.gov (United States)

    Orum, Aslihan; Takatori, Kazumasa; Hori, Shigeo; Ikeda, Tomiko; Yoshimura, Masamichi; Tani, Toshihiko

    2016-08-01

    Rectangular platelike particles of La2Ti2O7, a layered perovskite, were synthesized in KCl, NaCl, and LiCl by the molten flux method. The formation mechanism of the equilibrium shape in these alkali chloride fluxes was discussed in terms of the surface and interfacial energies of crystallographic planes. The atomic force microscopy (AFM) observations revealed that the developed plane of the platelike particles is along the interlayers in the {110}-type layered crystal structure, and is considered to represent the lowest surface energy plane in which strong, periodic Ti-O bond chains terminate. Herein, for the first time, a growth mechanism for La2Ti2O7 particles is proposed and discussed. Triangular prism structures along the c-axis were observed on the developed planes of KCl-grown particles whereas no such structures were found on those of LiCl-grown ones. AFM measurements suggest that the prism facets are {210}-La2Ti2O7, which results in lower interfacial energy within KCl.

  17. Application of fluidised particles as turbulence promoters in ultrafiltration Improvement of flux and rejection

    NARCIS (Netherlands)

    Noordman, TR; de Jonge, A; Wesselingh, JA; Bel, W; Dekker, M; Ter Voorde, E; Grijpma, SD

    2002-01-01

    To prevent fouling of ultrafiltration membranes during processing of protein solutions, a high degree of turbulence should be introduced in the feed solution, keeping the energy consumption as low as possible. For this purpose, the application of fluidised beds at the upstream side of the membrane c

  18. Determination of threshold shear stress to drag particles in cuttings bed; Determinacao da tensao de cisalhamento minima para arraste de particulas em um leito fluidizado

    Energy Technology Data Exchange (ETDEWEB)

    Loureiro, Bruno Venturini; Siqueira, Renato do Nascimento [Faculdade do Centro Leste (UCL), Serra, ES (Brazil). Lab. de Fenomenos de Transporte], e-mail: brunovl@ucl.br, e-mail: renatons@ucl.br

    2006-07-01

    Drilling of horizontal wells for oil and gas production needs an efficient cleaning process due to settling of particles removed during the drilling process, which settles on the inferior part of the annular space between the drilling column and the walls of the well. The erosion of the bed is an important physical phenomenon to petroleum and gas industry since it can improve the opening of the wells. This work aims to estimate the threshold shear stress necessary to start the erosion process in a sediment bed. An experimental apparatus was built from simplifications of the problem in order to measure the flow rate and identify the beginning of the process. The experiment consists of a rectangular duct with aspect ratio ({lambda} = h/b) of 1/3 and non dimensional length (L{sup *} = L/h) of 75. The sediment bed to be eroded was placed at 60< x{sup *}<66. Using the flow rate and the boundary conditions, a discretization of the problem was carried out to permit a computational solution using the finite volume method and hence, determine the shear stress. This work used particles with up to 3.0 mm and modeled the flow considering a bed with equivalent roughness. (author)

  19. Validity of intra-particle models of mass transfer kinetics in the analysis of a fin-tube type adsorption bed

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Sang Woo; Ahn, Sang Hyeok; Chung, Jae Dong [Sejong University, Seoul (Korea, Republic of); Kwon, Oh Kyung [Korea Institute of Industrial Technology, Chonan (Korea, Republic of)

    2014-05-15

    This study presents a numerical investigation of the heat and mass transfer kinetics of a fin-tube type adsorption bed using a two dimensional numerical model with silica-gel/water as the adsorbent and refrigerant pair. The performance is strongly affected by the heat and mass transfer in the adsorption bed, but the details of the mass transfer kinetics remain unclear. The validity of intra-particle models used to simulate mass transfer kinetics such as the equilibrium, LDF, and solid-diffusion models are examined, and the valid ranges of the diffusion ratio for each model are proposed. An intra-particle diffusion model should be carefully implemented; otherwise, seriously distorted results may be produced, i.e., over-estimation for the equilibrium model and under estimation for the LDF model.

  20. Atmospheric deposition of particles at a sensitive alpine lake: Size-segregated daily and annual fluxes from passive sampling techniques.

    Science.gov (United States)

    Tai, Anna Y-C; Chen, L-W Antony; Wang, Xiaoliang; Chow, Judith C; Watson, John G

    2017-02-01

    Lake Tahoe, a North American alpine lake long appreciated for its clear water and geographic setting, has experienced a trend of declining water clarity due to increasing nutrient and particle inputs. Contributions from atmospheric deposition of particulate matter (PM) could be important, yet they are inadequately quantified. This study established a yearlong deposition monitoring network in the northern Lake Tahoe Basin. Dry deposition was quantified on surrogate surfaces while wet deposition was based on particles suspended in precipitation at 24-hour resolution. The particle size ranges by these passive techniques were 1-64μm and 0.5-20μm in diameter for dry and wet deposition, respectively. Dry deposition of submicrometer (0.5-1μm) particles was also estimated by extrapolation of a lognormal size distribution. Higher daily number deposition fluxes (NDFdry and NDFwet) were found at a near-shore site, confirming substantial impacts of commercial and tourist activities. The two more isolated sites indicated a uniform regional background. On average, daily NDFdry is about one order of magnitude lower than daily NDFwet. Dry deposition velocities increased rapidly with particle size, as evidenced by collocated measurements of NDFdry and ambient particle number concentrations, though it seems less so for wet deposition due to different scavenging mechanisms. Despite fewer "wet" days than "dry" days during the monitoring period, wet processes dominated seasonal particle deposition, particularly in winter and spring when most precipitation occurred. Adopting sediment (insoluble, inorganic) particle fraction estimates from the literature, this study reports an annual particle flux of 2.9-5.2×10(10)#m(-2)yr(-1) for sediment particles with 1-20μm diameter and 6.1-11×10(10)#m(-2)yr(-1) for those with 0.5-20μm diameter. Implications of these findings to the current knowledge of atmospheric deposition in the Lake Tahoe Total Maximum Daily Load (TMDL) are discussed

  1. Size-resolved fluxes of sub-100-nm particles over forests

    DEFF Research Database (Denmark)

    Pryor, Sara; Barthelmie, Rebecca Jane; Spaulding, A.M.;

    2009-01-01

    Dry deposition of atmospheric particles is critically dependent on particle size and plays a key role in dictating the mass and number distributions of atmospheric particles. However, modeling dry deposition is constrained by a lack of understanding of controlling dependencies and accurate size...... leaf-on and are statistically robust. Particle deposition velocities normalized by friction velocity (v d +) are approximately four times smaller than comparable values for coniferous forests reported elsewhere. Comparison of the data with output from a new one-dimensional mechanistic particle...... deposition model designed for broadleaf forest exhibits greater accord with the measurements than two previous analytical models, but modeled v d + underestimate observed values by at least a factor of two for all Dp between 6 and 100 nm. When size-resolved particle deposition velocities for Dp

  2. Monitoring solar energetic particles with an armada of European spacecraft and the new automated SEPF (Solar Energetic Proton Fluxes) Tool

    Science.gov (United States)

    Sandberg, I.; Daglis, I. A.; Anastasiadis, A.; Balasis, G.; Georgoulis, M.; Nieminen, P.; Evans, H.; Daly, E.

    2012-01-01

    Solar energetic particles (SEPs) observed in interplanetary medium consist of electrons, protons, alpha particles and heavier ions (up to Fe), with energies from dozens of keVs to a few GeVs. SEP events, or SEPEs, are particle flux enhancements from background level ( 30 MeV. The main part of SEPEs results from the acceleration of particles either by solar flares and/or by interplanetary shocks driven by Coronal Mass Ejections (CMEs); these accelerated particles propagate through the heliosphere, traveling along the interplanetary magnetic field (IMF). SEPEs show significant variability from one event to another and are an important part of space weather, because they pose a serious health risk to humans in space and a serious radiation hazard for the spacecraft hardware which may lead to severe damages. As a consequence, engineering models, observations and theoretical investigations related to the high energy particle environment is a priority issue for both robotic and manned space missions. The European Space Agency operates the Standard Radiation Environment Monitor (SREM) on-board six spacecraft: Proba-1, INTEGRAL, Rosetta, Giove-B, Herschel and Planck, which measures high-energy protons and electrons with a fair angular and spectral resolution. The fact that several SREM units operate in different orbits provides a unique chance for comparative studies of the radiation environment based on multiple data gathered by identical detectors. Furthermore, the radiation environment monitoring by the SREM unit onboard Rosetta may reveal unknown characteristics of SEPEs properties given the fact that the majority of the available radiation data and models only refer to 1AU solar distances. The Institute for Space Applications and Remote Sensing of the National Observatory of Athens (ISARS/NOA) has developed and validated a novel method to obtain flux spectra from SREM count rates. Using this method and by conducting detailed scientific studies we have showed in

  3. Settling particle fluxes across the continental margin of the Gulf of Lion: the role of dense shelf water cascading

    Directory of Open Access Journals (Sweden)

    C. Pasqual

    2009-07-01

    Full Text Available Settling particles were collected using sediment traps deployed along three transects in the Lacaze-Duthiers and Cap de Creus canyons and the adjacent southern open slope from October 2005 to October 2006. The settling material was analysed to obtain total mass fluxes and main constituent contents (organic matter, opal, calcium carbonate, and siliciclastics. Cascades of dense shelf water from the continental shelf edge to the lower continental slope occurred from January to March 2006. They were traced through strong negative near-bottom temperature anomalies and increased current speeds, and generated two intense pulses of mass fluxes in January and March 2006. This oceanographic phenomenon appeared as the major physical forcing of settling particles at almost all stations, and caused both high seasonal variability in mass fluxes and important qualitative changes in settling material. Fluxes during the dense shelf water cascading (DSWC event ranged from 90.1 g m−2 d−1 at the 1000 m depth station in the Cap de Creus canyon to 3.2 g m−2 d−1 at the canyon mouth at 1900 m. Fractions of organic matter, opal and calcium carbonate components increased seaward, thus diminishing the siliciclastic fraction. Temporal variability of the major components was larger in the canyon mouth and open slope sites, due to the mixed impact of dense shelf water cascading processes and the pelagic biological production. Results indicate that the cascading event remobilized and homogenized large amounts of material down canyon and southwardly along the continental slope contributing to a better understanding of the internal dynamics of DSWC events. While the late winter/early spring bloom signature was diluted when DSWC occurred, the primary production dynamics were observable at all stations during the rest of the year and highlighted the biological community succession in surface waters.

  4. Control of particles flux in a tokamak with an events structure; Controle des flux de particules dans un Tokamak au moyen d`une structure a events

    Energy Technology Data Exchange (ETDEWEB)

    Tsitrone, E.

    1995-12-01

    Two key problems in the development of a controlled fusion reactor are: -the control of the ashes resulting from the fusion reaction (helium) and of the impurities coming from the wall erosion, which affect the central plasma performances by diluting the fuel and dissipating a part of the produced energy by radiation. - the removal of the heat carried to the walls by charged particles, which is highly concentrated (peak values of several tens of MW per m{sup 2}). Two types of systems are generally used for the plasma-wall interface: throat limiter and axisymmetric divertor. Neither is an ideal candidate to control simultaneously the heat and particle fluxes. This thesis investigates an alternative configuration, the vented limiter, tested for the first time on the Tore Supra tokamak. The vented limiter principle lies on the recycling neutrals collection by slots, in such a way that local thermal overload is avoided. It is shown experimentally that the surface temperature of the prototype installed in Tore Supra remains uniform. As far as the particle collection is concerned, even though the pressure in the vented limiter is lower than the pressure in the throat limiter by a factor 3 for deuterium and 4 helium, it is sufficient to control the plasma density. Moreover, as with a throat limiter, the pressure exhibits a quadratic evolution with the plasma density. To interpret these results, a model describing the plasma recycling on the limiter and the pumping by the slots has been developed. The model has been validated by a comparison with the experimental data. It was then used to propose an optimized version of the prototype with reshaped slots. This should improve the pumping efficiency by a factor 2, in deuterium as well as in helium, but without removing the discrepancy between both pumping efficiencies. (Abstract Truncated)

  5. Erosion of heat exchanger tubes in fluidized beds

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, E.K.; Flemmer, R.L.C.

    1991-01-01

    This final report describes the activities of the 3-year project entitled Erosion of Heat Exchanger Tubes In Fluidized Beds.'' which was completed at the end of 1990. Project accomplishments include the collection of a substantial body of wear data In a 24in. [times] 24in. fluidized bed, comparative wear results In a 6in. [times] 6in. fluidized bed, the development of a dragometer and the collection of a comprehensive set of drag force data in the 24in. [times] 24in. bed, Fast Fourier Transform (FFT) analysis of bubble probe data to establish dominant bubble frequencies in the 24in. [times] 24in. bed, the use of a heat flux gauge for measurement of heat transfer coefficients in the 24in. [times] 24in. bed and the modeling of the tube wear in the 24in. [times] 24in. bed. Analysis of the wear data from the 24in. square bed indicates that tube wear increases with increase in superficial velocity, and with increase in tube height. The latter effect is a result of the tubes higher up in the bed seeing greater movement of dense phase than tubes lower down In the bed. In addition, tube wear was found to decrease with increase in particle size, for constant superficial velocity. Three models of tube wear were formulated and provided acceptable prediction of wear when compared with the experimental data.

  6. Spatial and temporal variability of particle flux at the NW European continental margin

    NARCIS (Netherlands)

    Antia, A.N.; Maaßen, J.; Herman, P.M.J.; Voss, M.; Scholten, J.C.M.; Groom, S.; Miller, P.

    2001-01-01

    A synopsis of results from two sediment trap moorings deployed at the mid- and outer slope (water depths 1450 and 3660 m, respectively) of the Goban Spur (N.E. Atlantic Margin) is presented. Fluxes increase with trap deployment depth; below 1000 m resuspended and advected material contributes increa

  7. Sedgeunkedunk stream bed sediment particle diameter from 2007-08-15 to 2016-03-30 (NCEI Accession 0152487)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — We are collecting stream channel geometry and bed sediment grain size distribution data at Sedgeunkedunk stream to evaluate physical habitat changes associated with...

  8. Larkin Mill Dam bed sediment particle diameter from 2008-06-09 to 2016-03-30 (NCEI Accession 0152462)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — We are collecting stream channel geometry and bed sediment grain size distribution data at the Parker River to evaluate physical habitat changes associated with the...

  9. The MUSCLES Treasury Survey. IV. Scaling Relations for Ultraviolet, Ca ii K, and Energetic Particle Fluxes from M Dwarfs

    Science.gov (United States)

    Youngblood, Allison; France, Kevin; Parke Loyd, R. O.; Brown, Alexander; Mason, James P.; Schneider, P. Christian; Tilley, Matt A.; Berta-Thompson, Zachory K.; Buccino, Andrea; Froning, Cynthia S.; Hawley, Suzanne L.; Linsky, Jeffrey; Mauas, Pablo J. D.; Redfield, Seth; Kowalski, Adam; Miguel, Yamila; Newton, Elisabeth R.; Rugheimer, Sarah; Segura, Antígona; Roberge, Aki; Vieytes, Mariela

    2017-07-01

    Characterizing the UV spectral energy distribution (SED) of an exoplanet host star is critically important for assessing its planet’s potential habitability, particularly for M dwarfs, as they are prime targets for current and near-term exoplanet characterization efforts and atmospheric models predict that their UV radiation can produce photochemistry on habitable zone planets different from that on Earth. To derive ground-based proxies for UV emission for use when Hubble Space Telescope (HST) observations are unavailable, we have assembled a sample of 15 early to mid-M dwarfs observed by HST and compared their nonsimultaneous UV and optical spectra. We find that the equivalent width of the chromospheric Ca ii K line at 3933 Å, when corrected for spectral type, can be used to estimate the stellar surface flux in ultraviolet emission lines, including H i Lyα. In addition, we address another potential driver of habitability: energetic particle fluxes associated with flares. We present a new technique for estimating soft X-ray and >10 MeV proton flux during far-UV emission line flares (Si iv and He ii) by assuming solar-like energy partitions. We analyze several flares from the M4 dwarf GJ 876 observed with HST and Chandra as part of the MUSCLES Treasury Survey and find that habitable zone planets orbiting GJ 876 are impacted by large Carrington-like flares with peak soft X-ray fluxes ≥10-3 W m-2 and possible proton fluxes ˜102-103 pfu, approximately four orders of magnitude more frequently than modern-day Earth.

  10. The origin ofhigh hydraulic resistance for filter cakes ofdef ormable particles: cell-bed deformation or surface-layer effect?

    OpenAIRE

    Meireles, Martine; Molle, C.; Clifton, Michaël; Aimar, Pierre

    2004-01-01

    This study reports a numerical approach for modeling the hydraulic resistance ofa filter cake ofdef ormable cells. First, a mechanical and osmotic model that describes the volume fraction ofsolids in a bed ofyeast cells as a function ofthe compressive pressure it experiences is presented. The effects ofpressure on the compressibility ofyeast cells beds were further investigated both by filtration experiments and by centrifugal experiments based on the multiple speed equilibrium sediment he...

  11. Geomagnetically trapped, albedo and solar energetic particles: trajectory analysis and flux reconstruction with PAMELA

    CERN Document Server

    Bruno, A; Barbarino, G C; Bazilevskaya, G A; Bellotti, R; Boezio, M; Bogomolov, E A; Bongi, M; Bonvicini, V; Bottai, S; Cafagna, F; Campana, D; Carlson, P; Casolino, M; Castellini, G; Christian, E C; De Donato, C; de Nolfo, G A; De Santis, C; De Simone, N; Di Felice, V; Galper, A M; Karelin, A V; Koldashov, S V; Koldobskiy, S; Krutkov, S Y; Kvashnin, A N; Leonov, A; Malakhov, V; Marcelli, L; Martucci, M; Mayorov, A G; Menn, W; Mergé, M; Mikhailov, V V; Mocchiutti, E; Monaco, A; Mori, N; Munini, R; Osteria, G; Palma, F; Panico, B; Papini, P; Pearce, M; Picozza, P; Ricci, M; Ricciarini, S B; Ryan, J M; Sarkar, R; Scotti, V; Simon, M; Sparvoli, R; Spillantini, P; Stochaj, S; Stozhkov, Y I; Vacchi, A; Vannuccini, E; Vasilyev, G I; Voronov, S A; Yurkin, Y T; Zampa, G; Zampa, N

    2016-01-01

    The PAMELA satellite experiment is providing comprehensive observations of the interplanetary and magnetospheric radiation in the near-Earth environment. Thanks to its identification capabilities and the semi-polar orbit, PAMELA is able to precisely measure the energetic spectra and the angular distributions of the different cosmic-ray populations over a wide latitude region, including geomagnetically trapped and albedo particles. Its observations comprise the solar energetic particle events between solar cycles 23 and 24, and the geomagnetic cutoff variations during magnetospheric storms. PAMELA's measurements are supported by an accurate analysis of particle trajectories in the Earth's magnetosphere based on a realistic geomagnetic field modeling, which allows the classification of particle populations of different origin and the investigation of the asymptotic directions of arrival.

  12. Hysteretic sediment fluxes in rainfall-driven soil erosion: Particle size effects

    Science.gov (United States)

    Cheraghi, Mohsen; Jomaa, Seifeddine; Sander, Graham C.; Barry, D. A.

    2016-11-01

    A detailed laboratory study was conducted to examine the effects of particle size on hysteretic sediment transport under time-varying rainfall. A rainfall pattern composed of seven sequential stepwise varying rainfall intensities (30, 37.5, 45, 60, 45, 37.5, and 30 mm h-1), each of 20 min duration, was applied to a 5 m × 2 m soil erosion flume. The soil in the flume was initially dried, ploughed to a depth of 20 cm and had a mechanically smoothed surface. Flow rates and sediment concentration data for seven particle size classes (1000 µm) were measured in the flume effluent. Clockwise hysteresis loops in the sediment concentration versus discharge curves were measured for the total eroded soil and the finer particle sizes (erosion model agreed well with the experimental data for the total eroded soil and for the finer particle size classes (up to 50 µm). For the larger particle size classes, the model provided reasonable qualitative agreement with the measurements although the fit was poor for the largest size class (>1000 µm). Overall, it is found that hysteresis varies amongst particle sizes and that the predictions of the HR model are consistent with hysteretic behavior of different sediment size classes.

  13. Experimental investigation of pebble flow dynamics using radioactive particle tracking technique in a scaled-down Pebble Bed Modular Reactor (PBMR)

    Energy Technology Data Exchange (ETDEWEB)

    Khane, Vaibhav; Said, I.A.; Al-Dahhan, Muthanna H., E-mail: aldahhanm@mst.edu

    2016-06-15

    Highlights: • Pebble Flow fields at Pebble Bed Modular Reactor was investigated. • Radioactive Particle Tracking (RPT) technique has been used. • Plug flow type velocity profile is suggested at upper cylindrical region. - Abstract: The Pebble Bed Modular Reactor (PBMR) is a type of very-high-temperature reactor (VHTR) that is conceptually very similar to moving bed reactors used in the chemical and petrochemical industries. In a PBMR core, nuclear fuel is in the form of pebbles and moves slowly under the influence of gravity. In this work, an integrated experimental and computational study of granular flow in a scaled-down cold flow PBMR was performed. A continuous pebble re-circulation experimental set-up, mimicking the flow of pebbles in a PBMR was designed and developed. An experimental investigation of pebble flow dynamics in a scaled down test reactor was carried out using a non-invasive radioactive particle tracking (RPT) technique that used a cobalt-60 based tracer to mimic pebbles in terms of shape, size and density. A cross-correlation based position reconstruction algorithm and RPT calibration data were used to obtain results about Lagrangian trajectories, the velocity field, and residence time distributions. The RPT technique results a serve as a benchmark data for assessing contact force models used in the discrete element method (DEM) simulations.

  14. Measurement of limiter particle fluxes and carbon erosion in the helical scrape-off layer of startup plasmas at W7-X

    Science.gov (United States)

    Winters, V.; Biedermann, C.; Brezinsek, S.; Effenberg, F.; Frerichs, H.; Harris, J.; Schmitz, O.; Stephey, L.; Unterberg, E.; Wurden, G.; W7-X Team

    2016-10-01

    Measurement of the 2D recycling flux and calculations of the carbon erosion from the limiter in startup plasmas of W7-X provides a first insight into neutral particle release and impurity inflow into the helical scrape-off layer. H-alpha, C-II (514.5nm) and C-III (465.1nm) line emissions were collected with filter-scopes and a visible camera aimed at limiter 3 of W7-X. Local plasma parameters are considered to estimate physical and chemical sputtering contributions. The analytical model for chemical sputtering by Roth is used to convert the measured particle flux into a chemically eroded C flux. The particle flux as well as the extracted C erosion pattern deviates from the measured heat flux distribution and also from the predicted particle flux distribution from EMC3-EIRENE. Candidates to resolve this discrepancy are measurement uncertainties and physics related (e.g. asymmetry in the last closed flux surface position). Post-mortem analysis of the limiter will be taken into account and compared to these in-situ measurements to gather first detailed insight on the net C erosion distribution and the impurity sourcing into the helical scrape-off layer. This work was funded by DE-SC0014210, DE-AC5206NA25396, DE-AC05-00OR22725 and by EUROfusion under Grant No 633053.

  15. Reduction of calcium flux from the extracellular region and endoplasmic reticulum by amorphous nano-silica particles owing to carboxy group addition on their surface

    Directory of Open Access Journals (Sweden)

    Akira Onodera

    2017-03-01

    Full Text Available Several studies have reported that amorphous nano-silica particles (nano-SPs modulate calcium flux, although the mechanism remains incompletely understood. We thus analyzed the relationship between calcium flux and particle surface properties and determined the calcium flux route. Treatment of Balb/c 3T3 fibroblasts with nano-SPs with a diameter of 70 nm (nSP70 increased cytosolic calcium concentration, but that with SPs with a diameter of 300 or 1000 nm did not. Surface modification of nSP70 with a carboxy group also did not modulate calcium flux. Pretreatment with a general calcium entry blocker almost completely suppressed calcium flux by nSP70. Preconditioning by emptying the endoplasmic reticulum (ER calcium stores slightly suppressed calcium flux by nSP70. These results indicate that nSP70 mainly modulates calcium flux across plasma membrane calcium channels, with subsequent activation of the ER calcium pump, and that the potential of calcium flux by nano-SPs is determined by the particle surface charge.

  16. Neutrino fluxes from constrained minimal supersymmetric standard model lightest supersymmetric particle annihilations in the Sun

    CERN Document Server

    Ellis, John; Savage, Christopher; Spanos, Vassilis C

    2010-01-01

    We evaluate the neutrino fluxes to be expected from neutralino LSP annihilations inside the Sun, within the minimal supersymmetric extension of the Standard Model with supersymmetry-breaking scalar and gaugino masses constrained to be universal at the GUT scale (the CMSSM). We find that there are large regions of typical CMSSM $(m_{1/2}, m_0)$ planes where the LSP density inside the Sun is not in equilibrium, so that the annihilation rate may be far below the capture rate. We show that neutrino fluxes are dependent on the solar model at the 20% level, and adopt the AGSS09 model of Serenelli et al. for our detailed studies. We find that there are large regions of the CMSSM $(m_{1/2}, m_0)$ planes where the capture rate is not dominated by spin-dependent LSP-proton scattering, e.g., at large $m_{1/2}$ along the CMSSM coannihilation strip. We calculate neutrino fluxes above various threshold energies for points along the coannihilation/rapid-annihilation and focus-point strips where the CMSSM yields the correct ...

  17. Microscopic Deformation of Tungsten Surfaces by High Energy and High Flux Helium/Hydrogen Particle Bombardment with Short Pulses

    Science.gov (United States)

    Tokitani, Masayuki; Yoshida, Naoaki; Tokunaga, Kazutoshi; Sakakita, Hajime; Kiyama, Satoru; Koguchi, Haruhisa; Hirano, Yoichi; Masuzaki, Suguru

    The neutral beam injection facility in the National Institute of Advanced Industrial Science and Technology was used to irradiate a polycrystalline tungsten specimen with high energy and high flux helium and hydrogen particles. The incidence energy and flux of the beam shot were 25 keV and 8.8 × 1022 particles/m2 s, respectively. The duration of each shot was approximately 30 ms, with 6 min intervals between each shot. Surface temperatures over 1800 K were attained. In the two cases of helium irradiation, total fluence of either 1.5 × 1022 He/m2 or 4.0 × 1022 He/m2 was selected. In the former case, large sized blisters with diameter of 500 nm were densely observed. While, the latter case, the blisters were disappeared and fine nanobranch structures appeared instead. Cross-sectional observations using a transmission electron microscope (TEM) with the focused ion beam (FIB) technique were performed. According to the TEM image, after irradiation with a beam shot of total fluence 4.0 × 1022 He/m2 , there were very dense fine helium bubbles in the tungsten of sizes 1-50 nm. As the helium bubbles grew the density of the tungsten matrix drastically decreased as a result of void swelling. These effects were not seen in hydrogen irradiation case.

  18. Analytical Solution of Fick's Law of the TRISO-Coated Fuel Particles and Fuel Elements in Pebble-Bed High Temperature Gas-Cooled Reactors

    Institute of Scientific and Technical Information of China (English)

    CAO Jian-Zhu; FANG Chao; SUN Li-Feng

    2011-01-01

    T wo kinds of approaches are built to solve the fission products diffusion models (Fick's equation) based on sphere fuel particles and sphere fuel elements exactly. Two models for homogenous TRISO-coated fuel particles and fuel elements used in pebble-bed high temperature gas-cooled reactors are presented, respectively. The analytica,solution of Fick's equation for fission products diffusion in fuel particles is derived by variables separation.In the fuel element system, a modification of the diffusion coefficient from D to D/r is made to characterize the difference of diffusion rates in distinct areas and it is shown that the Laplace and Hankel transformations are effective as the diffusion coefficient in Fick's equation is dependant on the radius of the fuel element. Both the solutions are useful for the prediction of the fission product behaviors and could be programmed in the corresponding engineering calculations.%@@ Two kinds of approaches are built to solve the fission products diffusion models(Fick's equation) based on sphere fuel particles and sphere fuel elements exactly.Two models for homogenous TRISO-coated fuel particles and fuel elements used in pebble-bed high temperature gas-cooled reactors are presented,respectively.The analytical solution of Fick's equation for fission products diffusion in fuel particles is derived by variables separation.In the fuel element system,a modification of the diffusion coefficient from D to D/r is made to characterize the difference of diffusion rates in distinct areas and it is shown that the Laplace and Hankel transformations are effective as the diffusion coefficient in Fick's equation is dependant on the radius of the fuel element.Both the solutions are useful for the prediction of the fission product behaviors and could be programmed in the corresponding engineering calculations.

  19. Study of instability driving inward particle flux during the formation of transport barriers at the edge of the HL-2A tokamak

    Science.gov (United States)

    Kong, D. F.; Lan, T.; Liu, A. D.; Yu, C. X.; Zhao, H. L.; Shen, H. G.; Yan, L. W.; Dong, J. Q.; Xu, M.; Zhao, K. J.; Cheng, J.; Duan, X. R.; Liu, Y.; Chen, R.; Sun, X.; Xie, J. L.; Li, H.; Liu, W. D.; The HL-2A Team

    2017-01-01

    An electrostatic coherent mode with a frequency of 20∼ 100 kHz can be observed during the formation of transport barriers in high-confinement-mode plasma in the HL-2A tokamak, using reciprocating Langmuir probes. The mode drives a strong inward particle flux measured directly with four-tip probes with values comparable to the particle flux at the striking point in the divertor, which has also been validated by the measurement of other diagnostics. Several characteristics simultaneously indicate that the mode is an ion mode excited at the edge, which plays an important role in the formation of transport barriers besides particle diffusion.

  20. A Kinetic Transport Theory for Particle Acceleration and Transport in Regions of Multiple Contracting and Reconnecting Inertial-scale Flux Ropes

    Science.gov (United States)

    le Roux, J. A.; Zank, G. P.; Webb, G. M.; Khabarova, O.

    2015-03-01

    Simulations of particle acceleration in turbulent plasma regions with multiple contracting and merging (reconnecting) magnetic islands emphasize the key role of temporary particle trapping in island structures for the efficient acceleration of particles to form hard power-law spectra. Statistical kinetic transport theories have been developed that capture the essential physics of particle acceleration in multi-island regions. The transport theory of Zank et al. is further developed by considering the acceleration effects of both the mean and the variance of the electric fields induced by the dynamics of multiple inertial-scale flux ropes. A focused transport equation is derived that includes new Fokker-Planck terms for particle scattering and stochastic acceleration due to the variance in multiple flux-rope magnetic fields, plasma flows, and reconnection electric fields. A Parker transport equation is also derived in which a new expression for momentum diffusion appears, combining stochastic acceleration by particle scattering in the mean multi-flux-rope electric fields with acceleration by the variance in these electric fields. Test particle acceleration is modeled analytically considering drift acceleration by the variance in the induced electric fields of flux ropes in the slow supersonic, radially expanding solar wind. Hard power-law spectra occur for sufficiently strong inertial-scale flux ropes with an index modified by adiabatic cooling, solar wind advection, and diffusive escape from flux ropes. Flux ropes might be sufficiently strong behind interplanetary shocks where the index of suprathermal ion power-law spectra observed in the supersonic solar wind can be reproduced.

  1. A KINETIC TRANSPORT THEORY FOR PARTICLE ACCELERATION AND TRANSPORT IN REGIONS OF MULTIPLE CONTRACTING AND RECONNECTING INERTIAL-SCALE FLUX ROPES

    Energy Technology Data Exchange (ETDEWEB)

    Le Roux, J. A.; Zank, G. P. [Department of Space Science, University of Alabama in Huntsville, Huntsville, AL 35805 (United States); Webb, G. M. [Center for Space Plasma and Aeronomic Research (CSPAR), University of Alabama in Huntsville, Huntsville, AL 35805 (United States); Khabarova, O., E-mail: jar0013@uah.edu [Heliophysical Laboratory, Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radiowave Propagation RAS (IZMIRAN), Troitsk, Moscow 142190 (Russian Federation)

    2015-03-10

    Simulations of particle acceleration in turbulent plasma regions with multiple contracting and merging (reconnecting) magnetic islands emphasize the key role of temporary particle trapping in island structures for the efficient acceleration of particles to form hard power-law spectra. Statistical kinetic transport theories have been developed that capture the essential physics of particle acceleration in multi-island regions. The transport theory of Zank et al. is further developed by considering the acceleration effects of both the mean and the variance of the electric fields induced by the dynamics of multiple inertial-scale flux ropes. A focused transport equation is derived that includes new Fokker-Planck terms for particle scattering and stochastic acceleration due to the variance in multiple flux-rope magnetic fields, plasma flows, and reconnection electric fields. A Parker transport equation is also derived in which a new expression for momentum diffusion appears, combining stochastic acceleration by particle scattering in the mean multi-flux-rope electric fields with acceleration by the variance in these electric fields. Test particle acceleration is modeled analytically considering drift acceleration by the variance in the induced electric fields of flux ropes in the slow supersonic, radially expanding solar wind. Hard power-law spectra occur for sufficiently strong inertial-scale flux ropes with an index modified by adiabatic cooling, solar wind advection, and diffusive escape from flux ropes. Flux ropes might be sufficiently strong behind interplanetary shocks where the index of suprathermal ion power-law spectra observed in the supersonic solar wind can be reproduced.

  2. Verification of sub-grid filtered drag models for gas-particle fluidized beds with immersed cylinder arrays

    Energy Technology Data Exchange (ETDEWEB)

    Sarkar, Avik [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Sun, Xin [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Sundaresan, Sankaran [Princeton Univ., NJ (United States)

    2014-04-23

    The accuracy of coarse-grid multiphase CFD simulations of fluidized beds may be improved via the inclusion of filtered constitutive models. In our previous study (Sarkar et al., Chem. Eng. Sci., 104, 399-412), we developed such a set of filtered drag relationships for beds with immersed arrays of cooling tubes. Verification of these filtered drag models is addressed in this work. Predictions from coarse-grid simulations with the sub-grid filtered corrections are compared against accurate, highly-resolved simulations of full-scale turbulent and bubbling fluidized beds. The filtered drag models offer a computationally efficient yet accurate alternative for obtaining macroscopic predictions, but the spatial resolution of meso-scale clustering heterogeneities is sacrificed.

  3. Far scrape-off layer particle and heat fluxes in high density

    DEFF Research Database (Denmark)

    Müller, H. W.; Bernert, M.; Carralero, D.

    2014-01-01

    of turbulent SOL transport. At high N0,div and Psep the H-mode discharges enter a regime of high cross-field particle and power transport in the SOL which is accompanied by a significant change of the turbulence characteristic analogous to the transition from conductive to convective transport in L...

  4. Tailoring the charged particle fluxes across the target surface of Magnum-PSI

    NARCIS (Netherlands)

    Costin, C.; Anita, V.; Popa, G.; Scholten, J.; De Temmerman, G.

    2016-01-01

    Linear plasma generators are plasma devices designed to study fusion-relevant plasma-surface interactions. The first requirement for such devices is to operate with adjustable and well characterized plasma parameters. In the linear plasma device Magnum-PSI, the distribution of the charged particle f

  5. Particles in non-Abelian gauge potentials: Landau problem and insertion of non-Abelian flux

    NARCIS (Netherlands)

    Estienne, B.; Haaker, S.M.; Schoutens, K.

    2011-01-01

    In this paper, we study charged spin-1/2 particles in two dimensions, subjected to a perpendicular non-Abelian magnetic field. Specializing to a choice of vector potential that is spatially constant but non-Abelian, we investigate the Landau level spectrum in planar and spherical geometry, paying pa

  6. Radionuclide fluxes in the Arabian Sea: The role of particle composition

    Digital Repository Service at National Institute of Oceanography (India)

    Scholten, J.C.; Fietzke, J.; Mangini, A.; Stoffers, P.; Rixen, T.; Gaye-Haake, B.; Blanz, T.; Ramaswamy, V.; Sirocko, F; Schulz, H.; Ittekkot, V.

    hamper the interpretation of these correlation coefficients as a measure of relative scavenging affinities of the nuclides to the particle types investigated. The mean fractionation factor (F(Pa/Th)=K sub(d)(Pa)/K sub(d)(Th)) from the Equatorial Pacific...

  7. COLLISIONLESS SHOCKS IN A PARTIALLY IONIZED MEDIUM. I. NEUTRAL RETURN FLUX AND ITS EFFECTS ON ACCELERATION OF TEST PARTICLES

    Energy Technology Data Exchange (ETDEWEB)

    Blasi, P.; Morlino, G.; Bandiera, R.; Amato, E. [INAF-Osservatorio Astrofisico di Arcetri, Largo E. Fermi, 5, I-50125 Firenze (Italy); Caprioli, D. [Department of Astrophysical Sciences, Peyton Hall, Princeton University, Princeton, NJ 08540 (United States)

    2012-08-20

    A collisionless shock may be strongly modified by the presence of neutral atoms through the processes of charge exchange between ions and neutrals and ionization of the latter. These two processes lead to exchange of energy and momentum between charged and neutral particles both upstream and downstream of the shock. In particular, neutrals that suffer a charge exchange downstream with shock-heated ions generate high-velocity neutrals that have a finite probability of returning upstream. These neutrals might then deposit heat in the upstream plasma through ionization and charge exchange, thereby reducing the fluid Mach number. A consequence of this phenomenon, which we refer to as the neutral return flux, is a reduction of the shock compression factor and the formation of a shock precursor upstream. The scale length of the precursor is determined by the ionization and charge-exchange interaction lengths of fast neutrals moving toward upstream infinity. In the case of a shock propagating in the interstellar medium, the effects of ion-neutral interactions are especially important for shock velocities <3000 km s{sup -1}. Such propagation velocities are common among shocks associated with supernova remnants, the primary candidate sources for the acceleration of Galactic cosmic rays. We then investigate the effects of the return flux of neutrals on the spectrum of test particles accelerated at the shock. We find that, for shocks slower than {approx}3000 km s{sup -1}, the particle energy spectrum steepens appreciably with respect to the naive expectation for a strong shock, namely, {proportional_to}E{sup -2}.

  8. Escoabilidade de leitos de partículas inertes com polpa de frutas tropicais: efeitos na secagem em leito de jorro Flowability of inert particle beds with fruit pulp: effects on the drying in spouted bed

    Directory of Open Access Journals (Sweden)

    Maria de F. D. de Medeiros

    2001-12-01

    Full Text Available Neste trabalho, foram caracterizados seis tipos de material inerte, utilizados na secagem de polpa de frutas em leito de jorro. Determinou-se o ângulo de repouso das partículas, com e sem adição de água e de polpa de diversas frutas tropicais. Correlacionou-se a escoabilidade com as propriedades das partículas e com a composição química das polpas. Analisou-se a influência do ângulo de repouso sobre o desempenho do secador, no que se refere à produção. Os resultados mostraram que, em geral, as polpas com elevadas concentrações de gordura e sólidos insolúveis e baixos teores de açúcares redutores, facilitam a escoabilidade. Uma análise dos resultados obtidos na secagem de polpa de frutas tropicais, utilizando-se partículas de poliestireno de baixa densidade, como material inerte, mostrou que, embora a escoabilidade permita a obtenção de menores vazões de jorro mínimo, em relação ao desempenho do secador, pode não favorecer uma produção maior de pó.In this work six types of inert particles were characterized and analyzed for drying tropical fruit pulps. The repose angle was determined with and without the addition of water and pulp of various tropical fruits. The bed flowability was related to the particle properties and chemical composition of pulps. The influence of the repose angle on the drying performance was analyzed. It was also verified that the composition of pulps influenced the bed flowability. The global analysis showed that the pulps with high lipids and insoluble solids content and low reducing sugar content improved the bed flowability. The results obtained with the drying of the fruit pulps using low-density polystyrene granules as inert particles showed that high flowabilities lead to lower minimum spout flow rates, but do not necessarily lead to the highest powder production.

  9. Experimental Study of Packing and Flow Resistance of Sinter Particle Packed Bed%大颗粒填充床堆积和阻力特性研究

    Institute of Scientific and Technical Information of China (English)

    刘柏谦; 谭培来; 王立刚

    2012-01-01

    Characteristics of morphology,packing and flow resistance of large size sinter particle and its packed bed have been studied experimentally.It has been proved that particle morphology has real effect on packing feature in flow and pressure drop or resistant coefficient.The results show: firstly,the smaller the particle size,the higher particle sphericity;secondly,it has different porosity distribution for the same group of particle according to imagine analysis result;and the thirdly,porosity distribution has some difference in space which leads to odd resistance coefficient or pressure drop.In the maximum gas velocity of the experiment study,a linear relationship between pressure drop and bed height was seen,but it did not exist when operation gas velocity decreases.%试验研究了市售烧结矿颗粒的形貌特征及其构成的密堆积填充床特征.研究显示颗粒形貌对填充床堆积特性、流体穿过填充床的流动特性的影响确实存在.研究发现:烧结矿颗粒相对规则,颗粒越小球形度越高;相同烧结矿颗粒不同密堆积的空间空隙分布不同;操作阻力或压降测量显示了奇怪的数据,即阻力系数先升后降;试验范围内,最高操作速度下压降与床高成线性关系,速度降低后这种线性关系不复存在.

  10. Charge-exchange limits on low-energy alpha-particle fluxes in solar flares

    CERN Document Server

    Hudson, Hugh; MacKinnon, Alec; Woods, Tom

    2014-01-01

    This paper reports on a search for flare emission via charge-exchange radiation in the wings of the Lyman-alpha line of He ii at 304 A, as originally suggested for hydrogen by Orrall and Zirker. Via this mechanism a primary alpha particle that penetrates into the neutral chromosphere can pick up an atomic electron and emit in the He ii bound-bound spectrum before it stops. The Extreme-ultraviolet Variability Experiment (EVE) on board the Solar Dynamics Observatory (SDO) gives us our first chance to search for this effect systematically. The Orrall-Zirker mechanism has great importance for flare physics because of the essential roles that particle acceleration plays; this mechanism is one of the few proposed that would allow remote sensing of primary accelerated particles below a few MeV/nucleon. We study ten events in total, including the gamma-ray events SOL2010-06-12 (M2.0) and SOL2011-02-24 (M3.5) (the latter a limb flare), seven X-class flares, and one prominent M-class event that produced solar energetic...

  11. Influence of neutron flux, frequency and temperature to electrical impedance of nano silica particles

    Energy Technology Data Exchange (ETDEWEB)

    Huseynov, Elchin, E-mail: hus.elchin@yahoo.com, E-mail: hus.elchin@gmail.com; Garibov, Adil; Mehdiyeva, Ravan [Institute of Radiation Problems of Azerbaijan National Academy of Sciences, AZ 1143, B.Vahabzadeh 9, Baku (Azerbaijan); Andreja, Eršte, E-mail: andreja.erste@ijs.si [Condensed Matter Physics Department, Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana Slovenia (Slovenia); Rustamov, Anar, E-mail: a.rustamov@cern.ch [Goethe-Universität Frankfurt, Max-von-Laue-Str. 1, 60438 Frankfurt am Main (Germany)

    2014-11-15

    We studied electric impedance of SiO{sub 2} nanomaterial at its initial state and after being exposed to continuous neutron irradiation for up to 20 hours. In doing so we employed a flux of neutrons of 2x10{sup 13} n⋅cm{sup −2}s{sup −1} while the frequency and temperature ranges amounted to 0,09 – 2.3 MHz and 100 – 400 K correspondingly. Analysis in terms of the Cole-Cole expression revealed that with increasing irradiation period the polarization and relaxation times decrease as a result of combination of nanoparticles. Moreover, it is demonstrated that the electric conductivity of samples, on the other hand, increases with the increasing irradiation period. At low temperatures formations of clusters at three distinct states with different energies were resolved.

  12. Concentration and vertical flux of Fukushima-derived radiocesium in sinking particles from two sites in the Northwestern Pacific Ocean

    Directory of Open Access Journals (Sweden)

    M. C. Honda

    2013-06-01

    Full Text Available At two stations in the western North Pacific, K2 in the subarctic gyre and S1 in the subtropical gyre, time-series sediment traps were collecting sinking particles when the Fukushima Daiichi Nuclear Power Plant (FNPP1 accident occurred on 11 March 2011. Radiocesium (134Cs and 137Cs derived from the FNPP1 accident was detected in sinking particles collected at 500 m in late March 2011 and at 4810 m in early April 2011 at both stations. The sinking velocity of 134Cs and 137Cs was estimated to be 22 to 71 m day−1 between the surface and 500 m and >180 m day−1 between 500 m and 4810 m. 137Cs concentrations varied from 0.14 to 0.25 Bq g−1 dry weight. These values are higher than those of surface seawater, suspended particles, and zooplankton collected in April 2011. Although the radiocesium may have been adsorbed onto or incorporated into clay minerals, correlations between 134Cs and lithogenic material were not always significant; therefore, the form of the cesium associated with the sinking particles is still an open question. The total 137Cs inventory by late June at K2 and by late July at S1 was 0.5 to 1.7 Bq m−2 at both depths. Compared with 137Cs input from both stations by April 2011, estimated from the surface 137Cs concentration and mixed-layer depth and by assuming that the observed 137Cs flux was constant throughout the year, the estimated removal rate of 137Cs from the upper layer (residence time in the upper layer was 0.3 to 1.5% yr−1 (68 to 312 yr. The estimated removal rates and residence times are comparable to previously reported values after the Chernobyl accident (removal rate: 0.2–1%, residence time: 130–390 yr.

  13. Self-similarity of fluctuation particle fluxes in the plasma edge of the stellarator L-2M

    Energy Technology Data Exchange (ETDEWEB)

    Saenko, V.V. [Ulyanovsk State University, Leo Tolstoy str., 42, Ulyanovsk (Russian Federation)

    2010-05-15

    Results are presented of statistical studies of probability density of fluctuations of plasma density, floating potential, and turbulent particle fluxes measured by a Langmuir probe in the edge plasma of the L-2M stellarator. Empirical probability densities differ from Gaussian distributions. The empirical probability density distributions have heavy tails decreasing as x{sup -{alpha}}{sup -1} and are leptokurtic. Fractional stable distributions were successfully applied to describing such distributions. It is shown that fractional stable distributions give good fit to the distri-butions of increments of fluctuation amplitudes of physical variables under study. The distribution parameters are statistically estimated from measured time sequences (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  14. Global observations of electromagnetic and particle energy flux for an event during northern winter with southward interplanetary magnetic field

    Directory of Open Access Journals (Sweden)

    H. Korth

    2008-06-01

    Full Text Available The response of the polar ionosphere–thermosphere (I-T system to electromagnetic (EM energy input is fundamentally different to that from particle precipitation. To understand the I-T response to polar energy input one must know the intensities and spatial distributions of both EM and precipitation energy deposition. Moreover, since individual events typically display behavior different from statistical models, it is important to observe the global system state for specific events. We present an analysis of an event in Northern Hemisphere winter for sustained southward interplanetary magnetic field (IMF, 10 January 2002, 10:00–12:00 UT, for which excellent observations are available from the constellation of Iridium satellites, the SuperDARN radar network, and the Far-Ultraviolet (FUV instrument on the IMAGE satellite. Using data from these assets we determine the EM and particle precipitation energy fluxes to the Northern Hemisphere poleward of 60° MLAT and examine their spatial distributions and intensities. The accuracy of the global estimates are assessed quantitatively using comparisons with in-situ observations by DMSP along two orbit planes. While the location of EM power input evaluated from Iridium and SuperDARN data is in good agreement with DMSP, the magnitude estimated from DMSP observations is approximately four times larger. Corrected for this underestimate, the total EM power input to the Northern Hemisphere is 188 GW. Comparison of IMAGE FUV-derived distributions of the particle energy flux with DMSP plasma data indicates that the IMAGE FUV results similarly locate the precipitation accurately while underestimating the precipitation input somewhat. The total particle input is estimated to be 20 GW, nearly a factor of ten lower than the EM input. We therefore expect the thermosphere response to be determined primarily by the EM input even under winter conditions, and accurate assessment of the EM energy input is therefore key

  15. Communication: Evaporation: Influence of heat transport in the liquid on the interface temperature and the particle flux.

    Science.gov (United States)

    Heinen, Matthias; Vrabec, Jadran; Fischer, Johann

    2016-08-28

    Molecular dynamics simulations are reported for the evaporation of a liquid into vacuum, where a Lennard-Jones type fluid with truncated and shifted potential at 2.5σ is considered. Vacuum is enforced locally by particle deletion and the liquid is thermostated in its bulk so that heat flows to the planar interface driving stationary evaporation. The length of the non-thermostated transition region between the bulk liquid and the interface Ln is under study. First, it is found for the reduced bulk liquid temperature Tl/Tc = 0.74 (Tc is the critical temperature) that by increasing Ln from 5.2σ to 208σ the interface temperature Ti drops by 17% and the evaporation flux decreases by a factor of 4.4. From a series of simulations for increasing values of Ln, an asymptotic value Ti (∞) of the interface temperature for Ln → ∞ can be estimated which is 21% lower than the bulk liquid temperature Tl. Second, it is found that the evaporation flux is solely determined by the interface temperature Ti, independent on Tl or Ln. Combining these two findings, the evaporation coefficient α of a liquid thermostated on a macroscopic scale is estimated to be α ≈ 0.14 for Tl/Tc = 0.74.

  16. In-situ laser spectroscopy of CO, Ch4, and H2O in a particle laden laboratory-scale fluidized bed combustor

    Directory of Open Access Journals (Sweden)

    Lackner Maximilian

    2002-01-01

    Full Text Available The pyrolysis, devolatilization and char combustion of bituminous coal and biomass (beechwood, firwood were investigated in a laboratory-scale fluidized bed combustor by tunable diode laser spectroscopy. Individual fuel particles were suspended in the freeboard of the unit. The bed temperature was 800 °C, the oxygen partial pressure 0 to 20 kPa (0-10 vol.%. Two Fabry Perot type tunable near infrared diode lasers were deployed for quantitative in-situ species concentration measurements. CH4 and CO were measured simultaneously during devolatilization and char combustion in-situ 10 mm above the surface of the fuel particles as well as H2O using laser spectroscopy. Sand particles were passing the probing laser beam path. Besides the resonant absorption of the laser light by CO, CH4 and H2O severe and strongly transient non-resonant attenuation by partial blocking of the beam and beam steering effects occurred. By wavelength tuning the two laser sources, species concentrations could be determined. The measured absorbances had to be corrected for the real temperature measured at the position of the probing laser beam. In addition, CO, CO2 and O2 were determined ex-situ by con ventional methods. A spatial profile inside the FBC of major species (CH4, CO, CO2, O, H, OH was calculated using a chemical kinetics program for a single fuel particle in a plug flow reactor geometry. The results were compared to the experimental findings. Good agreement was found. Tunable diode laser spectroscopy was found to be an apt method of determining quantitative species concentrations of multiple gases in a high temperature multi phase environment.

  17. Variability in sinking fluxes and composition of particle-bound phosphorus in the Xisha area of the northern South China Sea

    Science.gov (United States)

    Dong, Yuan; Li, Qian P.; Wu, Zhengchao; Zhang, Jia-Zhong

    2016-12-01

    Export fluxes of phosphorus (P) by sinking particles are important in studying ocean biogeochemical dynamics, whereas their composition and temporal variability are still inadequately understood in the global oceans, including the northern South China Sea (NSCS). A time-series study of particle fluxes was conducted at a mooring station adjacent to the Xisha Trough in the NSCS from September 2012 to September 2014, with sinking particles collected every two weeks by two sediment traps deployed at 500 m and 1500 m depths. Five operationally defined particulate P classes of sinking particles including loosely-bound P, Fe-bound P, CaCO3-bound P, detrital apatite P, and refractory organic P were quantified by a sequential extraction method (SEDEX). Our results revealed substantial variability in sinking particulate P composition at the Xisha over two years of samplings. Particulate inorganic P was largely contributed from Fe-bound P in the upper trap, but detrital P in the lower trap. Particulate organic P, including exchangeable organic P, CaCO3-bound organic P, and refractory organic P, contributed up to 50-55% of total sinking particulate P. Increase of CaCO3-bound P in the upper trap during 2014 could be related to a strong El Niño event with enhanced CaCO3 deposition. We also found sediment resuspension responsible for the unusual high particles fluxes at the lower trap based on analyses of a two-component mixing model. There was on average a total mass flux of 78±50 mg m-2 d-1 at the upper trap during the study period. A significant correlation between integrated primary productivity in the region and particle fluxes at 500 m of the station suggested the important role of biological production in controlling the concentration, composition, and export fluxes of sinking particulate P in the NSCS.

  18. Statistical analysis of particle flux flowing into the end-target in between attached and detached states in the linear divertor plasma simulator NAGDIS-II

    Energy Technology Data Exchange (ETDEWEB)

    Tanaka, H. [National Institute for Fusion Science, Toki (Japan); Department of Fusion Science, SOKENDAI, Toki (Japan); Ohno, N.; Onda, T.; Takeyama, K.; Tsuji, Y. [Graduate School of Engineering, Nagoya University, Nagoya (Japan); Kajita, S.; Kuwabara, T. [Institute of Materials and Systems for Sustainability, Nagoya University (Japan)

    2016-08-15

    We have investigated the particle flux flowing into the axisymmetric end-target in the transient state from attached to detached divertor conditions in the linear plasma device NAGDIS-II. In the transient state, a dramatic decrease of the mean particle flux and a large-amplitude fluctuation with negative and positive spikes were observed. We have analyzed the fluctuation with a newly suggested analysis technique: pre-multiplied cubic spectrum with the wavelet transform. Analysis result indicates that these spikes consist of a few kilohertz components. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  19. Hydrodynamic characterization of fluid bed cokers

    Energy Technology Data Exchange (ETDEWEB)

    Knapper, B. [Saskatchewan Univ., Saskatoon, SK (Canada); Berruti, F. [Western Ontario Univ., London, ON (Canada); Grace, J.R.; Bi, H.T.; Lim, C.J. [British Columbia Univ., Vancouver, BC (Canada)

    2002-07-01

    Syncrude Canada Ltd. uses fluid bed cokers for thermal conversion of bitumen from Northern Alberta tar sands into distillates. This paper presents the results of a study that examined the hydrodynamic characteristics of a geometrically and dynamically scaled-down cold flow model of an industrial fluid bed coker. The cold flow model was constructed with Plexiglass with a semi-circular geometry to enable flow visualization of the solid particles. Several operating conditions were examined and measured for key characteristic parameters. Local void fractions were measured with an optical fibre probe, and a suction probe was used to determine the local solids mass fluxes at varying radial and axial locations of the fluidized bed. It was determined that there are large axial and radial variations in both the local voidage and solids mass flux in terms of gas-solids flow. The core-annulus model for dilute riser flow gives unsatisfactory predictions because the model is not able to forecast radial variations in the annular region. A modified core-annulus flow model was developed to address this problem. The modified model has continuous profiles for the gas velocity and solids flux to significantly improve predictions.16 refs., 1 tab., 3 figs.

  20. Cost-effective nanoporous Agar-Agar polymer/Nickel powder composite particle for effective bio-products adsorption by expanded bed chromatography.

    Science.gov (United States)

    Asgari, Setareh; Jahanshahi, Mohsen; Rahimpour, Ahmad

    2014-09-26

    In the present work a novel kind of dense nanoporous composite matrix for expanded bed application has been successfully first prepared with Nickel powder as a densifier and was covered with Agar-Agar layer as a skeleton, through the method of water-in-oil emulsification. Agar-Agar is a porous and inexpensive polymer. In order to fabricate cost-effective adsorbent with favorable qualities Agar-Agar polymer was used. Thereafter, the customized composite particle was modified by pseudo-affinity dye-ligand, Reactive Blue 4 (RB4), aimed at preparing a pseudo-affinity adsorbent (RB4-Agar-Ni) for bioprodut adsorption from aqueous solution. Bovine Serum Albumin (BSA) was selected as a model protein to investigate the adsorption behavior in batchwise and expanded bed chromatography, and the obtained results were evaluated with that of Streamline™ (Amersham-Pharmacia Biotech, Sweden). Spherical appearance and porous structure of composite particles were observed by the optical microscope (OM) and scanning electronic microscope (SEM). The results suggested that the matrices followed the logarithmic normal size distribution with the range of 65-300 μm and average diameter of 126.81-151.47 μm, proper wet density of 1.64-2.78 g/ml, water content of 62.74-34%, porosity of 98-90% and pore size of about 38-130 nm. For better comprehension of the impact of solid phase properties on the performance of the expanded bed, the expansion and hydrodynamic properties of a composite matrix with a series of densities was evaluated and estimated by the retention time distribution method (RTD) in an expanded bed and was compared with that of other matrices. According to obtained results the expansion factors under the same fluid velocity decreased by increasing the matrix density. Moreover, the axial dispersion coefficient (Dax) is the most appropriate parameter for evaluating the stability of expanded bed, on various operating conditions, such as different flow velocity, bed expansion

  1. Bed Bugs

    Science.gov (United States)

    Prevent, identify, and treat bed bug infestations using EPA’s step-by-step guides, based on IPM principles. Find pesticides approved for bed bug control, check out the information clearinghouse, and dispel bed bug myths.

  2. Bimodal Electron Fluxes of Nearly Relativistic Electrons during the Onset of Solar Particle Events: 1. Observations

    CERN Document Server

    Sun, Lingpeng; Klecker, Berndt; Krucker, Saem; Droege, Wolfgang

    2010-01-01

    We report for several solar energetic particle events intensity and anisotropy measurements of energetic electrons in the energy range ~ 27 to ~ 500 keV as observed with the Wind and ACE spacecraft in June 2000. The observations onboard Wind show bimodal pitch angle distributions (PAD), whereas ACE shows PADs with one peak, as usually observed for impulsive injection of electrons at the Sun. During the time of observation Wind was located upstream of the Earth's bow shock, in the dawn - noon sector, at distances of ~ 40 to ~ 70 Earth radii away from the Earth, and magnetically well connected to the quasi-parallel bow shock, whereas ACE, located at the libration point L1, was not connected to the bow shock. The electron intensity-time profiles and energy spectra show that the backstreaming electrons observed at Wind are not of magnetospheric origin. The observations rather suggest that the bi-modal electron PADs are due to reflection or scattering at an obstacle located at a distance of less than ~ 150 Earth r...

  3. Flux and stable C and N isotope composition of sinking particles in the Ulleung Basin of the East/Japan Sea

    Science.gov (United States)

    Hyun Kwak, Jung; Han, Eunah; Hwang, Jeomshik; Kim, Young, II; Lee, Chung Il; Kang, Chang-Keun

    2017-09-01

    Seasonal variability of sinking fluxes of total mass (TMF), particulate organic carbon and nitrogen (POC and PON) was examined using sinking particles collected from sediment traps during July 2011 to December 2011, and December 2012 to June 2013 at an offshore channel site; and from November 2013 to August 2014 at a nearshore slope site of the Ulleung Basin in the East/Japan Sea. δ13C and δ15N values of sinking particles were measured to elucidate the major export processes of POC and PON. Annual TMF (112-638 g m-2 yr-1) and fluxes of POC and PON (9.6-32.1 g C m-2 yr-1 and 1.2-4.5 g N m-2 yr-1, respectively) in the Ulleung Basin corresponded to the upper limit of values reported for other open seas and oceans in the world. No great seasonal variability in both quantitative (TMF, and fluxes and contents of POC and PON) and qualitative (C/N ratios, and δ13C and δ15N values) estimates of vertical fluxes was observed, reflecting a steady standing stock of chlorophyll a in the upper part of water column. Furthermore, high contents of POC and PON and nearly constant δ13C and δ15N values in sinking particles collected in the sediment traps, indicate that primary production in the euphotic zone may be a good predictor of TMF and export flux of organic matter. In this regard, our pilot study points out the importance of high annual primary production and low water temperature (<1 °C) beneath the 200-m water depth, which would enable more sinking particles to be preserved during export process by limiting microbial decomposition activity in the water column, in determining the high annual flux of sinking particles in the Ulleung Basin (UB). A simple stable isotope mixing model of sinking particles indicates that despite a slight seasonal variation, the contribution of intact phytoplankton to sinking organic flux is significant to the POC and PON flux in the UB. Further continuous time series sediment trap experiments are proposed to estimate the contribution of

  4. Energetic particle fluxes in the exterior cusp and the high-latitude dayside magnetosphere: statistical results from the Cluster/RAPID instrument

    Directory of Open Access Journals (Sweden)

    T. Asikainen

    2005-09-01

    Full Text Available In this paper we study the fluxes of energetic protons (30–4000 keV and electrons (20–400 keV in the exterior cusp and in the adjacent high-latitude dayside plasma sheet (HLPS with the Cluster/RAPID instrument. Using two sample orbits we demonstrate that the Cluster observations at high latitudes can be dramatically different because the satellite orbit traverses different plasma regions for different external conditions. We make a statistical study of energetic particles in the exterior cusp and HLPS by analysing all outbound Cluster dayside passes in February and March, 2002 and 2003. The average particle fluxes in HLPS are roughly three (protons or ten (electrons times larger than in the exterior cusp. This is also true on those Cluster orbits where both regions are visited within a short time interval. Moreover, the total electron fluxes, as well as proton fluxes above some 100 keV, in these two regions correlate with each other. This is true even for fluxes in every energy channel when considered separately. The spectral indices of electron and proton fluxes are the same in the two regions. We also examine the possible dependence of particle fluxes at different energies on the external (solar wind and IMF and internal (geomagnetic conditions. The energetic proton fluxes (but not electron fluxes in the cusp behave differently at low and high energies. At low energies (<70 keV, the fluxes increase strongly with the magnitude of IMF By. Instead, at higher energies the proton fluxes in the cusp depend on substorm/geomagnetic activity. In HLPS proton fluxes, irrespective of energy, depend strongly on the Kp and AE indices. The electron fluxes in HLPS depend both on the <Kp index and the solar wind speed. In the cusp the electron fluxes mainly depend on the solar wind speed, and are higher for northward than southward IMF. These results give strong evidence in favour of the idea that the

  5. Fluidized-bed gasification of biomass: Conversion of fine carabon particles in the freeboard; Biomassevergasung in der Wirbelschicht: Umsatz von feinen Kohlenstoffpartikeln im Freeboard

    Energy Technology Data Exchange (ETDEWEB)

    Miccio, F. [Ist. Ricerche sulla Combustione-CNR, Napoli (Italy); Moersch, O.; Spliethoff, H.; Hein, K.R.G. [Stuttgart Univ. (Germany). Inst. fuer Verfahrenstechnik und Dampfkesselwesen

    1998-09-01

    The conversion of carbon particles in gasification processes was investigated in a fluidized-bed reactor of the Institute of Chemical Engineering and Steam Boiler Technology of Stuttgart University. This reactor is heated electrically to process temperature, and freeboard coal particles can be sampled using an isokinetic probe. The fuel used in the experiments consisted of beech wood chips. The temperature and air rating, i.e. the main parameters of the process, were varied in order to investigate their influence on product gas quality and carbon conversion. The conversion rate is influenced to a significant extent by grain disintegration and discharge of carbon particles. In gasification conditions, a further conversion process takes place in the freeboard. (orig.) [Deutsch] In dieser Arbeit wird die Umsetzung von Kohlenstoffpartikeln unter Vergasungsbedingungen untersucht. Die Versuche wurden an einem Wirbelschichtreaktor des Instituts fuer Verfahrenstechnik und Dampfkesselwesen der Universitaet Stuttgart durchgefuehrt. Dieser Reaktor wird elektrisch auf Prozesstemperatur beheizt. Mit Hilfe einer isokinetischen Sonde koennen Proben von Kohlenstoffpartikeln im Freeboard genommen werden. Als Brennstoff wurden zerkleinerte Buchenholz-Hackschnitzel eingesetzt. Variiert wurden als Hauptparameter des Prozesses Temperatur und Luftzahl. Untersucht wurde der Einfluss dieser Parameter auf die Qualitaet des Produktgases und die Umsetzung des Kohlenstoffes. Kornzersetzungs- und Austragsvorgaenge von Kohlenstoffpartikeln spielen eine wichtige Rolle fuer den Kohlenstoffumsatz. Unter Vergasungsbedingungen findet im Freeboard eine weitere Umsetzung der Partikel statt. (orig.)

  6. Dust Impact Monitor (SESAME-DIM) on board Rosetta/Philae: Millimetric particle flux at comet 67P/Churyumov-Gerasimenko

    Science.gov (United States)

    Hirn, Attila; Albin, Thomas; Apáthy, István; Della Corte, Vincenzo; Fischer, Hans-Herbert; Flandes, Alberto; Loose, Alexander; Péter, Attila; Seidensticker, Klaus J.; Krüger, Harald

    2016-06-01

    Context. The Philae lander of the Rosetta mission, aimed at the in situ investigation of comet 67P/Churyumov-Gerasimenko, was deployed to the surface of the comet nucleus on 12 November 2014 at 2.99 AU heliocentric distance. The Dust Impact Monitor (DIM) as part of the Surface Electric Sounding and Acoustic Monitoring Experiment (SESAME) on the lander employed piezoelectric detectors to detect the submillimetre- and millimetre-sized dust and ice particles emitted from the nucleus. Aims: We determine the upper limit of the ambient flux of particles in the measurement range of DIM based on the measurements performed with the instrument during Philae's descent to its nominal landing site Agilkia at distances of about 22 km, 18 km, and 5 km from the nucleus barycentre and at the final landing site Abydos. Methods: The geometric factor of the DIM sensor was calculated assuming an isotropic ambient flux of the submillimetre- and millimetre-sized particles. For the measurement intervals when no particles were detected the maximum true impact rate was calculated by assuming Poisson distribution of the impacts, and it was given as the detection limit at a 95% confidence level. The shading by the comet environment at Abydos was estimated by simulating the pattern of illumination on Philae and consequently the topography around the lander. Results: Based on measurements performed with DIM, the upper limit of the flux of particles in the measurement range of the instrument was of the order of 10-8-10-7 m-2 s-1 sr-1 during descent. The upper limit of the ambient flux of the submillimetre- and millimetre-sized dust and ice particles at Abydos was estimated to be 1.6 × 10-9 m-2 s-1 sr-1 on 13 and 14 November 2014. A correction factor of roughly 1/3 for the field of view of the sensors was calculated based on an analysis of the pattern of illumination on Philae. Conclusions: Considering particle speeds below escape velocity, the upper limit for the volume density of particles in

  7. Quantifying the dynamics of flow within a permeable bed using time-resolved endoscopic particle imaging velocimetry (EPIV)

    Energy Technology Data Exchange (ETDEWEB)

    Blois, G. [University of Birmingham, School of Geography, Earth and Environmental Sciences, Birmingham (United Kingdom); University of Illinois, Department of Mechanical Science and Engineering, Urbana, IL (United States); Sambrook Smith, G.H.; Lead, J.R. [University of Birmingham, School of Geography, Earth and Environmental Sciences, Birmingham (United Kingdom); Best, J.L. [University of Illinois, Departments of Geology, Geography, Mechanical Science and Engineering, and Ven Te Chow Hydrosystems Laboratory, Urbana, IL (United States); Hardy, R.J. [Durham University, Department of Geography, Science Laboratories, Durham (United Kingdom)

    2012-07-15

    This paper presents results of an experimental study investigating the mean and temporal evolution of flow within the pore space of a packed bed overlain by a free-surface flow. Data were collected by an endoscopic PIV (EPIV) technique. EPIV allows the instantaneous velocity field within the pore space to be quantified at a high spatio-temporal resolution, thus permitting investigation of the structure of turbulent subsurface flow produced by a high Reynolds number freestream flow (Re{sub s} in the range 9.8 x 10{sup 3}-9.7 x 10{sup 4}). Evolution of coherent flow structures within the pore space is shown to be driven by jet flow, with the interaction of this jet with the pore flow generating distinct coherent flow structures. The effects of freestream water depth, Reynolds and Froude numbers are investigated. (orig.)

  8. Design of a high particle flux hydrogen helicon plasma source for used in plasma materials interaction studies

    Energy Technology Data Exchange (ETDEWEB)

    Goulding, Richard Howell [ORNL; Chen, Guangye [ORNL; Meitner, Steven J [ORNL; Baity Jr, F Wallace [ORNL; Caughman, John B [ORNL; Owen, Larry W [ORNL

    2009-01-01

    Existing linear plasma materials interaction (PMI) facilities all use plasma sources with internal electrodes. An rf-based helicon source is of interest because high plasma densities can be generated with no internal electrodes, allowing true steady state operation with minimal impurity generation. Work has begun at Oak Ridge National Laboratory (ORNL) to develop a large (15 cm) diameter helicon source producing hydrogen plasmas with parameters suitable for use in a linear PMI device: n(e) >= 10(19)m(-3), T(e) = 4-10 eV, particle flux Gamma(p) > 10(23) m(-3) s(-1), and magnetic field strength |B| up to I T in the source region. The device, whose design is based on a previous hydrogen helicon source operated at ORNL[1], will operate at rf frequencies in the range 10 - 26 MHz, and power levels up to similar to 100 kW. Limitations in cooling will prevent operation for pulses longer than several seconds, but a major goal will be the measurement of power deposition on device structures so that a later steady state version can be designed. The device design, the diagnostics to be used, and results of rf modeling of the device will be discussed. These include calculations of plasma loading, resulting currents and voltages in antenna structures and the matching network, power deposition profiles, and the effect of high |B| operation on power absorption.

  9. Multiobjective Design of Turbo Injection Mode for Axial Flux Motor in Plastic Injection Molding Machine by Particle Swarm Optimization

    Directory of Open Access Journals (Sweden)

    Jian-Long Kuo

    2015-01-01

    Full Text Available This paper proposes a turbo injection mode (TIM for an axial flux motor to apply onto injection molding machine. Since the injection molding machine requires different speed and force parameters setting when finishing a complete injection process. The interleaved winding structure in the motor provides two different injection levels to provide enough injection forces. Two wye-wye windings are designed to switch two control modes conveniently. Wye-wye configuration is used to switch two force levels for the motor. When only one set of wye-winding is energized, field weakening function is achieved. Both of the torque and speed increase under field weakening operation. To achieve two control objectives for torque and speed of the motor, fuzzy based multiple performance characteristics index (MPCI with particle swarm optimization (PSO is used to find out the multiobjective optimal design solution. Both of the torque and speed are expected to be maximal at the same time. Three control factors are selected as studied factors: winding diameter, winding type, and air-gap. Experimental results show that both of the torque and speed increase under the optimal condition. This will provide enough large torque and speed to perform the turbo injection mode in injection process for the injection molding machine.

  10. Using ground and intact coal Samples to evaluate hydrocarbon fate during supercritical CO2 injection into coal beds: effects of particle size and coal moisture

    Science.gov (United States)

    Kolak, Jon; Hackley, Paul C.; Ruppert, Leslie F.; Warwick, Peter D.; Burruss, Robert

    2015-01-01

    To investigate the potential for mobilizing organic compounds from coal beds during geologic carbon dioxide (CO2) storage (sequestration), a series of solvent extractions using dichloromethane (DCM) and using supercritical CO2 (40 °C and 10 MPa) were conducted on a set of coal samples collected from Louisiana and Ohio. The coal samples studied range in rank from lignite A to high volatile A bituminous, and were characterized using proximate, ultimate, organic petrography, and sorption isotherm analyses. Sorption isotherm analyses of gaseous CO2 and methane show a general increase in gas storage capacity with coal rank, consistent with findings from previous studies. In the solvent extractions, both dry, ground coal samples and moist, intact core plug samples were used to evaluate effects of variations in particle size and moisture content. Samples were spiked with perdeuterated surrogate compounds prior to extraction, and extracts were analyzed via gas chromatography–mass spectrometry. The DCM extracts generally contained the highest concentrations of organic compounds, indicating the existence of additional hydrocarbons within the coal matrix that were not mobilized during supercritical CO2 extractions. Concentrations of aliphatic and aromatic compounds measured in supercritical CO2 extracts of core plug samples generally are lower than concentrations in corresponding extracts of dry, ground coal samples, due to differences in particle size and moisture content. Changes in the amount of extracted compounds and in surrogate recovery measured during consecutive supercritical CO2extractions of core plug samples appear to reflect the transition from a water-wet to a CO2-wet system. Changes in coal core plug mass during supercritical CO2 extraction range from 3.4% to 14%, indicating that a substantial portion of coal moisture is retained in the low-rank coal samples. Moisture retention within core plug samples, especially in low-rank coals, appears to inhibit

  11. Influence of hydrogen concentration on Fe2O3 particle reduction in fluidized beds under constant drag force

    Institute of Scientific and Technical Information of China (English)

    Lei Guo; Han Gao; Jin-tao Yu; Zong-liang Zhang; Zhan-cheng Guo

    2015-01-01

    The fixed-gas drag force from a model calculation method that stabilizes the agitation capabilities of different gas ratios was used to explore the influence of temperature and hydrogen concentration on fluidizing duration, metallization ratio, utilization rate of reduction gas, and sticking behavior. Different hydrogen concentrations from 5vol%to 100vol%at 1073 and 1273 K were used while the drag force with the flow of N2 and H2 (N2:2 L·min−1;H2:2 L·min−1) at 1073 K was chosen as the standard drag force. The metallization ratio, mean reduc-tion rate, and utilization rate of reduction gas were observed to generally increase with increasing hydrogen concentration. Faster reduction rates and higher metallization ratios were obtained when the reduction temperature decreased from 1273 to 1073 K. A numerical relation among particle diameter, particle drag force, and fluidization state was plotted in a diagram by this model.

  12. Mariner 4 - A study of the cumulative flux of dust particles over a heliocentric range of 1-1.56 AU 1964-1967

    Science.gov (United States)

    Alexander, W. M.; Bohn, J. L.

    1974-01-01

    Between December 1964 and December 1967, the Mariner 4 dust particle experiment obtained data concerning the distribution of minute zodiacal dust cloud particles over a heliocentric range of 1-1.56 AU. The first measurement was over the complete heliocentric range, while the two additional measurements were made between 1.1 and 1.25 AU in 1966, and between 1.2 and 1.5 AU in 1967. The initial results of these measurements presented the mean cumulative flux for the respective data periods. The results of a detailed study and comparison of the three measurements are presented, with particular emphasis on the variation of the flux as a function of heliocentric range. A small, but statistically significant, increase in the flux is observed between 1.15 and 1.4 AU. The initial reports showed a lower cumulative flux for the latter two measurements. However, a detailed analysis containing corrections for spacecraft attitude indicate that all three measurements yield similar results, and that the particles detected were in low inclination orbits.

  13. Erosion of heat exchanger tubes in fluidized beds. Annual report, 1990

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, E.K.; Flemmer, R.L.C.

    1991-01-01

    This final report describes the activities of the 3-year project entitled ``Erosion of Heat Exchanger Tubes In Fluidized Beds.`` which was completed at the end of 1990. Project accomplishments include the collection of a substantial body of wear data In a 24in. {times} 24in. fluidized bed, comparative wear results In a 6in. {times} 6in. fluidized bed, the development of a dragometer and the collection of a comprehensive set of drag force data in the 24in. {times} 24in. bed, Fast Fourier Transform (FFT) analysis of bubble probe data to establish dominant bubble frequencies in the 24in. {times} 24in. bed, the use of a heat flux gauge for measurement of heat transfer coefficients in the 24in. {times} 24in. bed and the modeling of the tube wear in the 24in. {times} 24in. bed. Analysis of the wear data from the 24in. square bed indicates that tube wear increases with increase in superficial velocity, and with increase in tube height. The latter effect is a result of the tubes higher up in the bed seeing greater movement of dense phase than tubes lower down In the bed. In addition, tube wear was found to decrease with increase in particle size, for constant superficial velocity. Three models of tube wear were formulated and provided acceptable prediction of wear when compared with the experimental data.

  14. Characteristics of fluidized-packed beds

    Science.gov (United States)

    Gabor, J. D.; Mecham, W. J.

    1968-01-01

    Study of fluidized-packed bed includes investigation of heat transfer, solids-gas mixing, and elutriation characteristics. A fluidized-packed bed is a system involving the fluidization of small particles in the voids of a packed bed of larger nonfluidized particles.

  15. Discrete particle simulation of mixed sand transport

    Institute of Scientific and Technical Information of China (English)

    Fengjun Xiao; Liejin Guo; Debiao Li; Yueshe Wang

    2012-01-01

    An Eulerian/Lagrangian numerical simulation is performed on mixed sand transport.Volume averaged Navier-Stokes equations are solved to calculate gas motion,and particle motion is calculated using Newton's equation,involving a hard sphere model to describe particle-to-particle and particle-to-wall collisions.The influence of wall characteristics,size distribution of sand particles and boundary layer depth on vertical distribution of sand mass flux and particle mean horizontal velocity is analyzed,suggesting that all these three factors affect sand transport at different levels.In all cases,for small size groups,sand mass flux first increases with height and then decreases while for large size groups,it decreases exponentially with height and for middle size groups the behavior is in-between.The mean horizontal velocity for all size groups well fits experimental data,that is,increasing logarithmically with height in the middle height region.Wall characteristics greatly affects particle to wall collision and makes the flat bed similar to a Gobi surface and the rough bed similar to a sandy surface.Particle size distribution largely affects the sand mass flux and the highest heights they can reach especially for larger particles.

  16. Agglomeration-Free Distributor for Fluidized Beds

    Science.gov (United States)

    Ouyang, F.; Sinica, A.; Levenspiel, O.

    1986-01-01

    New gas distributor for fluidized beds prevents hot particles from reacting on it and forming hard crust. In reduction of iron ore in fluidized bed, ore particles do not sinter on distributor and perhaps clog it or otherwise interfere with gas flow. Distributor also relatively cool. In fluidized-bed production of silicon, inflowing silane does not decompose until within bed of hot silicon particles and deposits on them. Plates of spiral distributor arranged to direct incoming gas into spiral flow. Turbulence in flow reduces frequency of contact between fluidized-bed particles and distributor.

  17. Particle flux at the outlet of an Ecr plasma source; Flujos de particulas a la salida de una fuente de plasma ECR

    Energy Technology Data Exchange (ETDEWEB)

    Gutierrez T, C.; Gonzalez D, J. [ININ, Departamento de Fisica, A.P. 18-1027, 11801 Mexico D.F. (Mexico)

    2000-07-01

    The necessity of processing big material areas this has resulted in the development of plasma sources with the important property to be uniform in these areas. Also the continuous diminution in the size of substrates to be processed have stimulated the study of models which allow to predict the control of energy and the density of the ions and neutral particles toward the substrate. On the other hand, there are other applications of the plasma sources where it is very necessary to understand the effects generated by the energetic fluxes of ions and neutrals. These fluxes as well as another beneficial effects can improve the activation energy for the formation and improvement of the diffusion processes in the different materials. In this work, using the drift kinetic approximation is described a model to calculate the azimuthal and radial fluxes in the zone of materials processing of an Ecr plasma source type. The results obtained are compared with experimental results. (Author)

  18. Observations of particle extinction, PM2.5 mass concentration profile and flux in north China based on mobile lidar technique

    Science.gov (United States)

    Lv, Lihui; Liu, Wenqing; Zhang, Tianshu; Chen, Zhenyi; Dong, Yunsheng; Fan, Guangqiang; Xiang, Yan; Yao, Yawei; Yang, Nan; Chu, Baolin; Teng, Man; Shu, Xiaowen

    2017-09-01

    Fine particle with diameter limited by the lack of monitoring data obtained with multiple fixed site sampling strategies. Mobile monitoring has provided a means for broad measurement of fine particles. In this research, the potential use of mobile lidar to map the distribution and transport of fine particles was discussed. The spatial and temporal distributions of particle extinction, PM2.5 mass concentration and regional transport flux of fine particle in the planetary boundary layer were investigated with the use of vehicle-based mobile lidar and wind field data from north China. Case studies under different pollution levels in Beijing were presented to evaluate the contribution of regional transport. A vehicle-based mobile lidar system was used to obtain the spatial and temporal distributions of particle extinction in the measurement route. Fixed point lidar and a particulate matter sampler were operated next to each other at the University of Chinese Academy of Science (UCAS) in Beijing to determine the relationship between the particle extinction coefficient and PM2.5 mass concentration. The correlation coefficient (R2) between the particle extinction coefficient and PM2.5 mass concentration was found to be over 0.8 when relative humidity (RH) was less than 90%. A mesoscale meteorological model, the Weather Research and Forecasting (WRF) model, was used to obtain profiles of the horizontal wind speed, wind direction and relative humidity. A vehicle-based mobile lidar technique was applied to estimate transport flux based on the PM2.5 profile and vertical profile of wind data. This method was applicable when hygroscopic growth can be neglected (relatively humidity<90%). Southwest was found to be the main pathway of Beijing during the experiments.

  19. Compact and high-particle-flux thermal-lithium-beam probe system for measurement of two-dimensional electron density profile.

    Science.gov (United States)

    Shibata, Y; Manabe, T; Kajita, S; Ohno, N; Takagi, M; Tsuchiya, H; Morisaki, T

    2014-09-01

    A compact and high-particle-flux thermal-lithium-beam source for two-dimensional measurement of electron density profiles has been developed. The thermal-lithium-beam oven is heated by a carbon heater. In this system, the maximum particle flux of the thermal lithium beam was ~4 × 10(19) m(-2) s(-1) when the temperature of the thermal-lithium-beam oven was 900 K. The electron density profile was evaluated in the small tokamak device HYBTOK-II. The electron density profile was reconstructed using the thermal-lithium-beam probe data and this profile was consistent with the electron density profile measured with a Langmuir electrostatic probe. We confirm that the developed thermal-lithium-beam probe can be used to measure the two-dimensional electron density profile with high time and spatial resolutions.

  20. in Spouted Bed

    Directory of Open Access Journals (Sweden)

    Bronislaw Buczek

    2013-01-01

    Full Text Available Samples of active coke, fresh and spent after cleaning flue gases from communal waste incinerators, were investigated. The outer layers of both coke particles were separately removed by comminution in a spouted bed. The samples of both active cokes were analysed by means of densities, mercury porosimetry, and adsorption technique. Remaining cores were examined to determine the degree of consumption of coke by the sorption of hazardous emissions (SO2, HCl, and heavy metals through its bed. Differences in contamination levels within the porous structure of the particles were estimated. The study demonstrated the effectiveness of commercial active coke in the cleaning of flue gases.

  1. Ecosystem function and particle flux dynamics across the Mackenzie Shelf (Beaufort Sea, Arctic Ocean: an integrative analysis of spatial variability and biophysical forcings

    Directory of Open Access Journals (Sweden)

    A. Forest

    2013-05-01

    Full Text Available A better understanding of how environmental changes affect organic matter fluxes in Arctic marine ecosystems is sorely needed. Here we combine mooring times series, ship-based measurements and remote sensing to assess the variability and forcing factors of vertical fluxes of particulate organic carbon (POC across the Mackenzie Shelf in 2009. We developed a geospatial model of these fluxes to proceed to an integrative analysis of their determinants in summer. Flux data were obtained with sediment traps moored around 125 m and via a regional empirical algorithm applied to particle size distributions (17 classes from 0.08–4.2 mm measured by an Underwater Vision Profiler 5. The low fractal dimension (i.e., porous, fluffy particles derived from the algorithm (1.26 ± 0.34 and the dominance (~ 77% of rapidly sinking small aggregates (p r2 cum. = 0.37. Bacteria were correlated with small aggregates, while northeasterly wind was associated with large size classes (> 1 mm ESD, but these two factors were weakly related with each other. Copepod biomass was overall negatively correlated (p < 0.05 with vertical POC fluxes, implying that metazoans acted as regulators of export fluxes, even if their role was minor given that our study spanned the onset of diapause. Our results demonstrate that on interior Arctic shelves where productivity is low in mid-summer, localized upwelling zones (nutrient enrichment may result in the formation of large filamentous phytoaggregates that are not substantially retained by copepod and bacterial communities.

  2. Nonlinear fluid simulation of particle and heat fluxes during burst of ELMs on DIII-D with BOUT++  code

    Science.gov (United States)

    Xia, T. Y.; Xu, X. Q.

    2015-09-01

    In order to study the distribution and evolution of the transient particle and heat fluxes during edge-localized mode (ELM) bursts, a BOUT++  six-field two-fluid model based on the Braginskii equations with non-ideal physics effects is used to simulate pedestal collapse in divertor geometry. The profiles from the DIII-D H-mode discharge #144382 with fast target heat flux measurements are used as the initial conditions for the simulations. A flux-limited parallel thermal conduction is used with three values of the flux-limiting coefficient {αj} , free streaming model with {αj}=1 , sheath-limit with {αj}=0.05 , and one value in between. The studies show that a 20 times increase in {αj} leads to  ∼6 times increase in the heat flux amplitude to both the inner and outer targets, and the widths of the fluxes are also expanded. The sheath-limit model of flux-limiting coefficient is found to be the most appropriate one, which shows ELM sizes close to the measurements. The evolution of the density profile during the burst of ELMs of DIII-D discharge #144382 is simulated, and the collapse in width and depth of {{n}\\text{e}} are reproduced at different time steps. The growing process of the profiles for the heat flux at divertor targets during the burst of ELMs measured by IRTV (infrared television) is also reproduced by this model. The widths of heat fluxes towards targets are a little narrower, and the peak amplitudes are twice the measurements possibly due to the lack of a model of divertor radiation which can effectively reduce the heat fluxes. The magnetic flutter combined with parallel thermal conduction is found to be able to increase the total heat loss by around 33% since the magnetic flutter terms provide the additional conductive heat transport in the radial direction. The heat flux profile at both the inner and outer targets is obviously broadened by magnetic flutter. The lobe structures near the X-point at LFS are both broadened and elongated due

  3. Turbulent heat flux measurement in a non-reacting round jet, using BAM:Eu2+ phosphor thermography and particle image velocimetry

    Science.gov (United States)

    Lee, Hyunchang; Böhm, Benjamin; Sadiki, Amsini; Dreizler, Andreas

    2016-07-01

    Turbulent mixing is highly important in flows that involve heat and mass transfer. Information on turbulent heat flux is needed to validate the mixing models implemented in numerical simulations. The calculation of turbulent heat fluxes requires instantaneous information on temperature and velocity. Even using minimally intrusive laser optical methods, simultaneous measurement of temperature and velocity is still a challenge. In this study, thermographic phosphor particles are used for simultaneous thermometry and velocimetry: conventional particle image velocimetry is combined with temperature-dependent spectral shifts of BAM:Eu2+ phosphor particles upon UV excitation. The novelty of this approach is the analysis of systematic errors and verification using the well-known properties of a heated turbulent jet issuing into a low velocity, cold coflow. The analysis showed that systematic errors caused by laser fluence, multiple scattering, or preferential signal absorption can be reduced such that reliable measurement of scalar fluxes becomes feasible, which is a prerequisite for applying the method to more complex heat transfer problems.

  4. Dust particle flux and size distribution in the coma of 67P/Churyumov-Gerasimenko measured in situ by the COSIMA instrument on board Rosetta

    Science.gov (United States)

    Merouane, Sihane; Zaprudin, Boris; Stenzel, Oliver; Langevin, Yves; Altobelli, Nicolas; Della Corte, Vincenzo; Fischer, Henning; Fulle, Marco; Hornung, Klaus; Silén, Johan; Ligier, Nicolas; Rotundi, Alessandra; Ryno, Jouni; Schulz, Rita; Hilchenbach, Martin; Kissel, Jochen; Cosima Team

    2016-12-01

    Context. The COmetary Secondary Ion Mass Analyzer (COSIMA) on board Rosetta is dedicated to the collection and compositional analysis of the dust particles in the coma of 67P/Churyumov-Gerasimenko (67P). Aims: Investigation of the physical properties of the dust particles collected along the comet trajectory around the Sun starting at a heliocentric distance of 3.5 AU. Methods: The flux, size distribution, and morphology of the dust particles collected in the vicinity of the nucleus of comet 67P were measured with a daily to weekly time resolution. Results: The particles collected by COSIMA can be classified according to their morphology into two main types: compact particles and porous aggregates. In low-resolution images, the porous material appears similar to the chondritic-porous interplanetary dust particles collected in Earth's stratosphere in terms of texture. We show that this porous material represents 75% in volume and 50% in number of the large dust particles collected by COSIMA. Compact particles have typical sizes from a few tens of microns to a few hundreds of microns, while porous aggregates can be as large as a millimeter. The particles are not collected as a continuous flow but appear in bursts. This could be due to limited time resolution and/or fragmentation either in the collection funnel or few meters away from the spacecraft. The average collection rate of dust particles as a function of nucleo-centric distance shows that, at high phase angle, the dust flux follows a 1/d2comet law, excluding fragmentation of the dust particles along their journey to the spacecraft. At low phase angle, the dust flux is much more dispersed compared to the 1/d2comet law but cannot be explained by fragmentation of the particles along their trajectory since their velocity, indirectly deduced from the COSIMA data, does not support such a phenomenon. The cumulative size distribution of particles larger than 150 μm follows a power law close to r- 0.8 ± 0

  5. Dissolved and particulate Barium in the Ganga (Hooghly) River estuary, India: Solute-particle interactions and the enhanced dissolved flux to the oceans

    Science.gov (United States)

    Samanta, Saumik; Dalai, Tarun K.

    2016-12-01

    less significant and account for up to 5% of the annual Ba flux from the Hooghly estuary. The estimates of Ba flux show that annually (1.5-1.9) × 107 moles of Ba is transported by the Hooghly River. About (3.6-4.3) × 107 moles of Ba is generated annually in the estuary through desorption. Added together, the desorbed and riverine Ba fluxes generate a total Ba flux of (5.1-6.2) × 107 moles per year. Thus, the solute-particle interactions enhance the riverine Ba flux by >300%. A compilation of the available data shows that the enhancement of the riverine Ba flux and the fractions of desorbed Ba flux scale with (particulate matter flux/water flux) ratio in several estuaries of the world, suggesting that the process of solute-particle interactions is a major driver for the estuarine production of Ba on a global scale. Among the rivers considered in this study, the estuaries of the Hooghly River and the Ganges-Brahmaputra rivers, characterized by very high (sediment flux/water flux) ratio, depict the highest increase in the riverine Ba flux. This unique feature of the Ganga River system is inferred to be resulting from the collective impact of the tectonic activity and the monsoonal rainfall in the catchment areas.

  6. Dust Impact Monitor (SESAME-DIM) on board Rosetta/Philae: Millimetric particle flux at comet 67P/Churyumov-Gerasimenko

    CERN Document Server

    Hirn, Attila; Apáthy, István; Della Corte, Vincenzo; Fischer, Hans-Herbert; Flandes, Alberto; Loose, Alexander; Péter, Attila; Seidensticker, Klaus J; Krüger, Harald

    2016-01-01

    The Philae lander of the Rosetta mission, aimed at the in situ investigation of comet 67P/C-G, was deployed to the surface of the comet nucleus on 12 Nov 2014 at 2.99 AU heliocentric distance. The Dust Impact Monitor (DIM) as part of the Surface Electric Sounding and Acoustic Monitoring Experiment (SESAME) on the lander employed piezoelectric detectors to detect the submillimetre- and millimetre-sized dust and ice particles emitted from the nucleus. We determine the upper limit of the ambient flux of particles in the measurement range of DIM based on the measurements performed with the instrument during Philae's descent to its nominal landing site Agilkia at distances of about 22 km, 18 km, and 5 km from the nucleus barycentre and at the final landing site Abydos. The geometric factor of the DIM sensor is calculated assuming an isotropic ambient flux of the submillimetre- and millimetre-sized particles. For the measurement intervals when no particles were detected the maximum true impact rate was calculated b...

  7. Bimodal porous silica microspheres decorated with polydopamine nano-particles for the adsorption of methylene blue in fixed-bed columns.

    Science.gov (United States)

    Ataei-Germi, Taher; Nematollahzadeh, Ali

    2016-05-15

    Bimodal meso/macro-porous silica microspheres (MSM) were synthesized by a modified sol-emulsion-gel method and then the surface was coated with polydopamine (PDA) nano-particles of 39nm in size. Focusing on the encouraging properties of the synthesized adsorbent, such as high specific surface area (612.3m(2)g(-1), because of mesopores), fast mass transfer (0.9-2.67×10(-3)mLmin(-1)mg, because of macropores), and abundant "adhesive" functional groups of PDA, it was used for the removal of methylene blue (MB) from aqueous solution in a fixed-bed column. The effect of different parameters such as pH, initial concentration, and flow rate was studied. The results revealed that an appropriate sorption condition is an alkaline solution of MB (e.g., pH 10) at low flow rate (less than 5mLmin(-1)). Furthermore, the compatibility of the experimental data with mathematical models such as Thomas and Adams-Bohart was investigated. Both of the models showed a good agreement with the experimental data (R(2)=0.9954-0.9994), and could be applied for the prediction of the column properties and breakthrough curves. Regeneration of the column was performed by using HCl solution with a concentration of 0.1M as an eluent. Copyright © 2016 Elsevier Inc. All rights reserved.

  8. RESEARCH ON REUSE OF PAPERMAKING LIGNIN-CONVERSION OF LIGNIN TO BTX BY CATALYTIC PYROLYSIS IN A POWDER PARTICLE FLUIDIZED BED

    Institute of Scientific and Technical Information of China (English)

    Chang Wang; Chongwo Li; Qingzhu Jia

    2004-01-01

    Experiments on the catalytic pyrolysis of the papermaking lignin were conduced by using a new type of powder-particle fluidized bed to improve the yield of the light aromatic hydrocarbon, i.e. benzene,toluene, xylene and naphthalene (BTXN), in which the primary decomposition and secondary catalytic reaction occur simultaneously at ambient pressure.The effect of catalyst species, fluidizing gases and pyrolysis temperature on the yield of the BTXN were investigated. The content of sulfur is high in the papermaking lignin, and the volatile matter is effected by the temperature. In the case of the inert media silica sand, the yield and the distribution of the pyrolysis products were almost unchanged under the different kind of atmosphere. In the case of the catalyst CoMo-B with hydrogen atmosphere, the intermediate BTXN yield reached 2.52wt%, dry, 3.3 times as much as that in the case of silica sand.Therefore, in order to obtain valuable BTXN as an intermediate in the pyrolysis as much as possible, it is extremely important to select high sulfur resistance and hydrogenization activity catalyst.

  9. RESEARCH ON REUSE OF PAPERMAKING LIGNIN-CONVERSION OF LIGNIN TO BTX BY CATALYTIC PYROLYSIS IN A POWDER PARTICLE FLUIDIZED BED

    Institute of Scientific and Technical Information of China (English)

    ChangWang; ChongwoLi; QingzhuJia

    2004-01-01

    Experiments on the catalytic pyrolysis of the papermaking lignin were conduced by using a new type of powder-particle fluidized bed to improve the yield of the light aromatic hydrocarbon, i.e. benzene, toluene, xylene and naphthalene (BTXN), in which the primary decomposition and secondary catalytic reaction occur simultaneously at ambient pressure. The effect of catalyst species, fluidizing gases and pyrolysis temperature on the yield of the BTXN were investigated. The content of sulfur is high in the papermaking lignin, and the volatile matter is effected by the temperature. In the case of the inert media silica sand, the yield and the distribution of the pyrolysis products were almost unchanged under the different kind of atmosphere. In the case of the catalyst CoMo-B with hydrogen atmosphere, the intermediate BTXN yield reached 2.52wt%, dry, 3.3 times as much as that in the case of silica sand. Therefore, in order to obtain valuable BTXN as an intermediate in the pyrolysis as much as possible, it is extremely important to select high sulfur resistance and hydrogenization activity catalyst.

  10. The implications for dust emission modeling of spatial and vertical variations in horizontal dust flux and particle size in the Bodélé Depression, Northern Chad

    Science.gov (United States)

    Chappell, Adrian; Warren, Andrew; O'Donoghue, Alice; Robinson, Andrea; Thomas, Andrew; Bristow, Charlie

    2008-02-01

    The Bodélé Depression has been confirmed as the single largest source of atmospheric mineral dust on Earth. It is a distinctive source because of its large exposure of diatomite and the presence of mega-barchan dunes. Direct measurements of horizontal dust flux and particle size were made to investigate dust emission processes and for comparison with mechanisms of emission assumed in current dust models. More than 50 masts, with traps mounted on each, were located across and downwind of three barchans in 56 km2 study area of the eastern Bodélé. The size-distribution of surface material is bi-modal; there are many fine dust modes and a mixed mineralogy with a particle density three times smaller than quartz. Horizontal fluxes (up to 70 m above the playa) of particles, up to 1000 μm in diameter, are produced frequently from the accelerated flow over and around the barchans, even in below-threshold shear conditions on the diatomite playa. Our data on dust sizes do not conform to retrievals of dust size distributions from radiance measurements made in the same area. Dust emission models for the region may need to be revised to account for: saltators in the Bodélé, which are a mixture of quartz sand and diatomite flakes; the great spatial and vertical variation in the abundance, mass and density of dust and abraders; and the patterns of surface erodibility. All of these have important local effects on the vertical dust flux and its particle sizes.

  11. Pore Structure Analysis of Seaweed Particles After Fluidized Bed Combustion%海藻颗粒流化床燃烧后灰孔隙结构分析

    Institute of Scientific and Technical Information of China (English)

    徐姗楠; 王爽; 王谦; 姜秀民; 吉恒松

    2015-01-01

    In this work , the combustion of two kinds of seaweed(Enteromorpha clathrata and Sargassum natans)particles was studied on a bench scale fluidized bed. Enteromorpha clathrata particles burred continuously and stably at 770,℃ and no slagging was found. But a serious slagging phenomenon was found during the combustion of Sargassum natans,which showed that Sargassum natans particles were not suited for the fluidized bed combustion. Enteromorpha clathrata and its bottom ash were collected for pore structure analysis. The pore structure of seaweed and its ash samples was analyzed by applying mercury intrusion method and N2 adsorption-desorption method. The experimental result of applying mercury intrusion showed that the pore size distribution of original sample mostly ranged from 2.56,μm to 3.61,μm,and that of ash mainly ranged from 11.89,μm to 12.8,μm. The number of porosity,pore volume and specific surface area increased after combustion. The porosity increased from 21.01%to 49.74%. The nitrogen adsorption experiment was conducted to analyze both the original sample and the ash so as to understand the change of nano-scale pore structure in the combustion process. The specific surface area of sample was abtained by applying the BET(Brunauer-Emmett-Teller)equation using the linear part(0.05

  12. What controls sediment flux in dryland channels?

    Science.gov (United States)

    Michaelides, K.; Singer, M. B.

    2010-12-01

    Theories for the development of longitudinal and grain size profiles in perennial fluvial systems are well developed, allowing for generalization of sediment flux and sorting in these fluvial systems over decadal to millennial time scales under different forcings (e.g., sediment supply, climate changes, etc). However, such theoretical frameworks are inadequate for understanding sediment flux in dryland channels subject to spatially and temporally discontinuous streamflow, where transport capacity is usually much lower than sediment supply. In such fluvial systems, channel beds are poorly sorted with weak vertical layering, poorly defined bar forms, minimal downstream fining, and straight longitudinal profiles. Previous work in dryland channels has documented sediment flux at higher rates than their humid counterparts once significant channel flow develops, pulsations in bed material transport under constant discharge, and oscillations in dryland channel width that govern longitudinal patterns in erosion and deposition. These factors point to less well appreciated controls on sediment flux in dryland valley floors that invite further study. This paper investigates the relative roles of hydrology, bed material grain size, and channel width on sediment flux rates in the Rambla de Nogalte in southeastern Spain. Topographic valley cross sections and hillslope and channel particle sizes were collected from an ephemeral-river reach. Longitudinal grain-size variation on the hillslopes and on the channel bed were analysed in order to determine the relationship between hillslope supply characteristics and channel grain-size distribution and longitudinal changes. Local fractional estimates of bed-material transport in the channel were calculated using a range of channel discharge scenarios in order to examine the effect of channel hydrology on sediment transport. Numerical modelling was conducted to investigate runoff connectivity from hillslopes to channel and to examine the

  13. Particle fluxes and their drivers in the Avilés submarine canyon and adjacent slope, central Cantabrian margin, Bay of Biscay

    Science.gov (United States)

    Rumín-Caparrós, A.; Sanchez-Vidal, A.; González-Pola, C.; Lastras, G.; Calafat, A.; Canals, M.

    2016-05-01

    The Avilés Canyon in the central Cantabrian margin is one of the largest submarine canyons in Europe, extending from the shelf edge at 130 m depth to 4765 m depth in the Biscay abyssal plain. In this paper we present the results of a year-round (March 2012 to April 2013) study of particle fluxes in this canyon and the adjacent continental slope. Three mooring lines equipped with automated sequential sediment traps, high-accuracy conductivity-temperature recorders and current meters allowed measuring total mass fluxes and their major components (lithogenics, calcium carbonate, opal and organic matter) in the settling material jointly with a set of environmental parameters. The integrated analysis of the data obtained from the moorings together with remote sensing images and meteorological and hydrographical data has shed light on the sources of particles and the across- and along margin mechanisms involved in their transfer to the deep. Our results allow interpreting the dynamics of the sedimentary particles in the study area. Two factors play a critical role: (i) direct delivery of river-sourced material to the narrow continental shelf, and (ii) major resuspension events caused by large waves and near bottom currents developing at the occasion of the rather frequent severe storms that are typical of the Cantabrian Sea. Wind direction and subsequent wind-driven currents largely determine the way sedimentary particles reach the canyon. While westerly winds favour the injection of sediments into the Avilés Canyon mainly by building an offshore transport in the bottom Ekman layer, easterly winds ease the offshore advection of particulate matter towards the Avilés Canyon and its adjacent western slope principally through the surface Ekman layer. Furthermore, repeated cycles of semidiurnal tides add an extra amount of energy to the prevailing bottom currents and actively contribute to keep a permanent background of suspended particles in near-bottom waters. High

  14. A charged spinless particle in scalar–vector harmonic oscillators with uniform magnetic and Aharonov–Bohm flux fields

    Directory of Open Access Journals (Sweden)

    Sameer M. Ikhdair

    2014-10-01

    Full Text Available The two-dimensional solution of the spinless Klein–Gordon (KG equation for scalar–vector harmonic oscillator potentials with and without the presence of constant perpendicular magnetic and Aharonov–Bohm (AB flux fields is studied within the asymptotic function analysis and Nikiforov–Uvarov (NU method. The exact energy eigenvalues and normalized wave functions are analytically obtained in terms of potential parameters, magnetic field strength, AB flux field and magnetic quantum number. The results obtained by using different Larmor frequencies are compared with the results in the absence of both magnetic field (ωL = 0 and AB flux field (ξ = 0 case. Effects of external fields on the non-relativistic energy eigenvalues and wave functions solutions are also precisely presented.

  15. ELM simulation experiments on Pilot-PSI using simultaneous high flux plasma and transient heat/particle source

    NARCIS (Netherlands)

    De Temmerman, G.; Zielinski, J. J.; van Diepen, S.; Marot, L.; Price, M.

    2011-01-01

    A new experimental setup has been developed for edge localized mode (ELM) simulation experiments with relevant steady-state plasma conditions and transient heat/particle source. The setup is based on the Pilot-PSI linear plasma device and allows the superimposition of a transient heat/particle pulse

  16. Observed particle sizes and fluxes of Aeolian sediment in the near surface layer during sand-dust storms in the Taklamakan Desert

    Science.gov (United States)

    Huo, Wen; He, Qing; Yang, Fan; Yang, Xinghua; Yang, Qing; Zhang, Fuyin; Mamtimin, Ali; Liu, Xinchun; Wang, Mingzhong; Zhao, Yong; Zhi, Xiefei

    2016-08-01

    Monitoring, modeling and predicting the formation and movement of dust storms across the global deserts has drawn great attention in recent decades. Nevertheless, the scarcity of real-time observations of the wind-driven emission, transport and deposition of dusts has severely impeded progress in this area. In this study, we report an observational analysis of sand-dust storm samples collected at seven vertical levels from an 80-m-high flux tower located in the hinterland of the great Taklamakan Desert for ten sand-dust storm events that occurred during 2008-2010. We analyzed the vertical distribution of sandstorm particle grain sizes and horizontal sand-dust sediment fluxes from the near surface up to 80 m high in this extremely harsh but highly representative environment. The results showed that the average sandstorm grain size was in the range of 70 to 85 μm. With the natural presence of sand dunes and valleys, the horizontal dust flux appeared to increase with height within the lower surface layer, but was almost invariant above 32 m. The average flux values varied within the range of 8 to 14 kg m-2 and the vertical distribution was dominated by the wind speed in the boundary layer. The dominant dust particle size was PM100 and below, which on average accounted for 60-80 % of the samples collected, with 0.9-2.5 % for PM0-2.5, 3.5-7.0 % for PM0-10, 5.0-14.0 % for PM0-20 and 20.0-40.0 % for PM0-50. The observations suggested that on average the sand-dust vertical flux potential is about 0.29 kg m-2 from the top of the 80 m tower to the upper planetary boundary layer and free atmosphere through the transport of particles smaller than PM20. Some of our results differed from previous measurements from other desert surfaces and laboratory wind-dust experiments, and therefore provide valuable observations to support further improvement of modeling of sandstorms across different natural environmental conditions.

  17. Measurement of a neutral particle flux by a thermal method using the junction temperature effect; Mesure d'un flux de particules neutres par une methode thermique mettant a contribution l'effet de temperature des jonctions

    Energy Technology Data Exchange (ETDEWEB)

    Caron, Anthime [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires. Services Scientifiques

    1966-07-01

    Among all the methods suitable for measuring neutral particle fluxes obtained by proton charge exchange in an organic gas, the thermal method has been chosen. The energy imparted by the neutral particles to the target in the form of heat leads to the latter temperature increasing; this temperature is usually followed with a thermocouple. In order to increase the sensitivity and the elegance of the apparatus the thermocouple has been replaced by a junction whose characteristics are known to vary with temperature. A calibration is carried out using a beam of charged particles. The response obtained is linear. Measurements have been made with a power of up to 1 mW; the accuracy increases with the energy provided; for 4 joules an accuracy of 10 per cent is obtained. The apparatus may be improved in particular by extending the measurement range towards low power values, and by increasing the accuracy. (author) [French] Parmi toutes les methodes utilisees pour la mesure d'un flux de particules neutres, obtenues par echange de charge de protons dans un gaz organique, nous avons choisi la methode thermique. L'energie cedee par les particules neutres a la cible sous forme de chaleur provoque une elevation de temperature de celle-ci; cette temperature est habituellement reperee par thermocouple. Pour accroitre la sensibilite et la finesse de l'appareillage, nous avons substitue au thermocouple une jonction dont on sait que les caracteristiques varient avec la temperature. Un etalonnage est realise par un faisceau de particules chargees. La reponse obtenue est lineaire. Des puissances de l'ordre du mW ont ete mesurees; la precision croit avec l'energie apportee; elle est de 10 pour cent quand celle-ci est de 4 joules. L'appareillage peut etre notablement perfectionne, pour reculer la gamme des mesures vers les basses puissances et accroitre la precision. (auteur)

  18. Rapid ignition of fluidized bed boiler

    Science.gov (United States)

    Osborn, Liman D.

    1976-12-14

    A fluidized bed boiler is started up by directing into the static bed of inert and carbonaceous granules a downwardly angled burner so that the hot gases cause spouting. Air is introduced into the bed at a rate insufficient to fluidize the entire bed. Three regions are now formed in the bed, a region of lowest gas resistance, a fluidized region and a static region with a mobile region at the interface of the fluidized and static regions. Particles are transferred by the spouting action to form a conical heap with the carbonaceous granules concentrated at the top. The hot burner gases ignite the carbonaceous matter on the top of the bed which becomes distributed in the bed by the spouting action and bed movement. Thereafter the rate of air introduction is increased to fluidize the entire bed, the spouter/burner is shut off, and the entire fluidized bed is ignited.

  19. Ecosystem function and particle flux dynamics across the Mackenzie Shelf (Beaufort Sea, Arctic Ocean: an integrative analysis of spatial variability and biophysical forcings

    Directory of Open Access Journals (Sweden)

    A. Forest

    2012-08-01

    Full Text Available A better understanding of how environmental changes affect organic matter fluxes in Arctic marine ecosystems is sorely needed. Here, we combine mooring times-series, ship-based measurements and remote-sensing to assess the variability and forcing factors of vertical fluxes of particulate organic carbon (POC across the Mackenzie Shelf in 2009. We developed a geospatial model of these fluxes to proceed to an integrative analysis of their biophysical determinants in summer. Flux data were obtained with sediment traps and via a regional empirical algorithm applied to particle size-distributions (17 classes from 0.08–4.2 mm measured by an Underwater Vision Profiler 5. Redundancy analyses and forward selection of abiotic/biotic parameters, linear trends, and spatial structures (i.e. principal coordinates of neighbor matrices, PCNM, were conducted to partition the variation of POC flux size-classes. Flux variability was explained at 69.5 % by the addition of a linear temporal trend, 7 significant PCNM and 9 biophysical variables. The interaction of all these factors explained 27.8 % of the variability. The first PCNM canonical axis (44.4 % of spatial variance reflected a shelf-basin gradient controlled by bottom depth and ice concentration (p < 0.01, but a complex assemblage of fine-to-broad scale patterns was also identified. Among biophysical parameters, bacterial production and northeasterly wind (upwelling-favorable were the two strongest explanatory variables (r2 cum. = 0.37, suggesting that bacteria were associated with sinking material, which was itself partly linked to upwelling-induced productivity. The second most important spatial structure corresponded actually to the two areas where shelf break upwelling is known to occur under easterlies. Copepod biomass was negatively correlated (p < 0.05 with vertical POC fluxes, implying that metazoans played a significant role in the regulation of export fluxes. The

  20. Influence of gas-particle partitioning on ammonia and nitric acid fluxes above a deciduous forest in the Midwestern USA

    Science.gov (United States)

    Hansen, K.; Sørensen, L. L.; Hornsby, K. E.; Boegh, E.; Pryor, S. C.

    2013-12-01

    Quantifying the atmosphere-biosphere exchange of reactive nitrogen gasses (including ammonia (NH3) and nitric acid (HNO3)) is crucial to assessing the impact of anthropogenic activities on natural and semi-natural ecosystems. However, measuring the deposition of reactive nitrogen is challenging due to bi-directionality of the flux, and the dynamics of the chemical gas/aerosol equilibrium of NH3 and HNO3 (or other atmospheric acids) with aerosol-phase ammonium (NH4+) and nitrate (NO3-). NH3 and HNO3 are both very reactive and typically exhibit higher deposition velocities than aerosol NH4+. Therefore, the phase partitioning between gas and aerosol phases can have a significant effect on local budgets and atmospheric transport distances (Nemitz et al., Atmos. Chem. Phys., 2004). In this study, fluxes of NH3, HNO3 and carbon dioxide (CO2) along with size-resolved N-aerosol concentrations are measured above the deciduous forest, Morgan Monroe State Forest (MMSF) in south-central Indiana (39°53'N, 86°25'W) during a field campaign. Two relaxed eddy accumulation (REA) systems are used to measure fluxes and concentrations of NH3 and HNO3 at 44 m. The NH3 REA system operates based on wet effluent diffusion denuders with detection by florescence and half-hourly flux measurements are calculated. HNO3 REA system is based on gas capture on sodium chloride (NaCl) coated denuders with subsequent analysis by ion-chromatography, and the resulting fluxes have a resolution of 3-4 hours. CO2 fluxes are measured by eddy covariance using a closed-path Licor LI-7500, while two MSP MOUDI-110 impactors are used to measure the 24-hourly average inorganic and 48 hourly averaged organic ion concentrations in 11 size bins, respectively, just above the canopy level (28 m). The results of this field campaign are used to quantify the fluxes of NH3, HNO3, CO2 to/from the forest during the transition towards senescence, and to investigate process-level controls (e.g. the role of phase

  1. [Radiation transformation mechanism in a photocatalytic reactor of three-phase internal circulating fluidized bed].

    Science.gov (United States)

    You, Hong; Luo, Wei-nan; Yao, Jie; Chen, Ping; Cai, Wei-min

    2005-01-01

    A novel three-phase internal circulating fluidized bed photocatalytic reactor was established and the radiation transformation in which was investigated. The experimental results indicate that with the interaction of gas and solid (gas flux > 0.3m3/h), the radiation transformation in the reactor along radial direction conforms to a definite exponential function, which agrees to formula Rose about the rules of light intensity distribution through evenly suspended particles. The value of radiation energy is affected by the initial light intensity, the concentration of photocatalyst and the thickness of liquid layer. The aerated gas amount only influence the state of the fluidized bed and has little effect on the distribution of light intensity along radical direction. Photocatalytic degradation of Rhodamine B indicate that the efficiency of three-phase internal circulating fluidized bed is much higher than slurry bed. The optimal catalyst concentration of this system is 10 - 12g/L.

  2. Thermal-hydraulic analysis techniques for axisymmetric pebble bed nuclear reactor cores. [PEBBLE code

    Energy Technology Data Exchange (ETDEWEB)

    Stroh, K.R.

    1979-03-01

    The pebble bed reactor's cylindrical core volume contains a random bed of small, spherical fuel-moderator elements. These graphite spheres, containing a central region of dispersed coated-particle fissile and fertile material, are cooled by high pressure helium flowing through the connected interstitial voids. A mathematical model and numerical solution technique have been developed which allow calculation of macroscopic values of thermal-hydraulic variables in an axisymmetric pebble bed nuclear reactor core. The computer program PEBBLE is based on a mathematical model which treats the bed macroscopically as a generating, conducting porous medium. The steady-state model uses a nonlinear Forchheimer-type relation between the coolant pressure gradient and mass flux, with newly derived coefficients for the linear and quadratic resistance terms. The remaining equations in the model make use of mass continuity, and thermal energy balances for the solid and fluid phases.

  3. Constraints on the energy spectra of charged particles predicted in some model interactions of hadrons with help of the atmospheric muon flux

    CERN Document Server

    Dedenko, L G; Roganova, T M

    2015-01-01

    It has been shown that muon flux intensities calculated in terms of the EPOS LHC and EPOS 1.99 models at the energy of 10^4 GeV exceed the data of the classical experiments L3+Cosmic, MACRO and LVD on the spectra of atmospheric muons by a factor of 1.9 and below these data at the same energy by a factor of 1.8 in case of the QGSJET II-03 model. It has been concluded that these tested models overestimate (underestimate in case of QGSJET II-03 model) the production of secondary particles with the highest energies in interactions of hadrons by a factor of ~1.5. The LHCf and TOTEM accelerator experiments show also this type of disagreements with these model predictions at highest energies of secondary particles.

  4. Characterization of a detector chain using a FPGA-based time-to-digital converter to reconstruct the three-dimensional coordinates of single particles at high flux.

    Science.gov (United States)

    Nogrette, F; Heurteau, D; Chang, R; Bouton, Q; Westbrook, C I; Sellem, R; Clément, D

    2015-11-01

    We report on the development of a novel FPGA-based time-to-digital converter and its implementation in a detection chain that records the coordinates of single particles along three dimensions. The detector is composed of micro-channel plates mounted on top of a cross delay line and connected to fast electronics. We demonstrate continuous recording of the timing signals from the cross delay line at rates up to 4.1 × 10(6) s(-1) and three-dimensional reconstruction of the coordinates up to 3.2 × 10(6) particles per second. From the imaging of a calibrated structure we measure the in-plane resolution of the detector to be 140(20) μm at a flux of 3 × 10(5) particles per second. In addition, we analyze a method to estimate the resolution without placing any structure under vacuum, a significant practical improvement. While we use UV photons here, the results of this work apply to the detection of other kinds of particles.

  5. Characterization of a detector chain using a FPGA-based time-to-digital converter to reconstruct the three-dimensional coordinates of single particles at high flux

    Energy Technology Data Exchange (ETDEWEB)

    Nogrette, F.; Chang, R.; Bouton, Q.; Westbrook, C. I.; Clément, D. [Laboratoire Charles Fabry, Institut d’Optique Graduate School, CNRS, Univ. Paris-Saclay, 91127 Palaiseau cedex (France); Heurteau, D.; Sellem, R. [Fédération de Recherche LUMAT (DTPI), CNRS, Univ. Paris-Sud, Institut d’Optique Graduate School, Univ. Paris-Saclay, F-91405 Orsay (France)

    2015-11-15

    We report on the development of a novel FPGA-based time-to-digital converter and its implementation in a detection chain that records the coordinates of single particles along three dimensions. The detector is composed of micro-channel plates mounted on top of a cross delay line and connected to fast electronics. We demonstrate continuous recording of the timing signals from the cross delay line at rates up to 4.1 × 10{sup 6} s{sup −1} and three-dimensional reconstruction of the coordinates up to 3.2 × 10{sup 6} particles per second. From the imaging of a calibrated structure we measure the in-plane resolution of the detector to be 140(20) μm at a flux of 3 × 10{sup 5} particles per second. In addition, we analyze a method to estimate the resolution without placing any structure under vacuum, a significant practical improvement. While we use UV photons here, the results of this work apply to the detection of other kinds of particles.

  6. Flux and spectral variability of the blazar PKS 2155 -304 with XMM-Newton: Evidence of particle acceleration and synchrotron cooling

    Science.gov (United States)

    Bhagwan, Jai; Gupta, A. C.; Papadakis, I. E.; Wiita, Paul J.

    2016-04-01

    We have analyzed XMM-Newton observations of the high energy peaked blazar, PKS 2155 -304, made on 24 May 2002 in the 0.3-10 keV X-ray band. These observations display a mini-flare, a nearly constant flux period and a strong flux increase. We performed a time-resolved spectral study of the data, by dividing the data into eight segments. We fitted the data with a power-law and a broken power-law model, and in some of the segments we found a noticeable spectral flattening of the source's spectrum below 10 keV. We also performed "time-resolved" cross-correlation analyses and detected significant hard and soft lags (for the first time in a single observation of this source) during the first and last parts of the observation, respectively. Our analysis of the spectra, the variations of photon-index with flux as well as the correlation and lags between the harder and softer X-ray bands indicate that both the particle acceleration and synchrotron cooling processes make an important contribution to the emission from this blazar. The hard lags indicate a variable acceleration process. We also estimated the magnetic field value using the soft lags. The value of the magnetic field is consistent with the values derived from the broad-band SED modeling of this source.

  7. Flux and spectral variability of the blazar PKS 2155-304 with XMM-Newton: Evidence of Particle Acceleration and Synchrotron Cooling

    CERN Document Server

    Bhagwana, Jai; Papadakis, I E; Wiita, Paul J

    2016-01-01

    We have analyzed XMM-Newton observations of the high energy peaked blazar, PKS 2155-304, made on 24 May 2002 in the 0.3 - 10 keV X-ray band. These observations display a mini-flare, a nearly constant flux period and a strong flux increase. We performed a time-resolved spectral study of the data, by dividing the data into eight segments. We fitted the data with a power-law and a broken power-law model, and in some of the segments we found a noticeable spectral flattening of the source's spectrum below 10 keV. We also performed time-resolved cross-correlation analyses and detected significant hard and soft lags (for the first time in a single observation of this source) during the first and last parts of the observation, respectively. Our analysis of the spectra, the variations of photon-index with flux as well as the correlation and lags between the harder and softer X-ray bands indicate that both the particle acceleration and synchrotron cooling processes make an important contribution to the emission from th...

  8. Probability of rebound and eject of sand particles in wind-blown sand movement

    Institute of Scientific and Technical Information of China (English)

    Li Xie; Xiaojing Zheng

    2007-01-01

    When incident particles impact into a sand bed in wind-blown sand movement, rebound of the incident particles and eject of the sand particles by the incident particles affect directly the development of wind sand flux. In order to obtain rebound and eject lift-off probability of the sand particles, we apply the particle-bed stochastic collision model presented in our pervious works to derive analytic solutions of velocities of the incident and impacted particles in the postcollision bed. In order to describe randomness inherent in the real particle-bed collision, we take the incident angle, theimpact position and the direction of resultant action of sand particles in sand bed on the impacted sand particle as random variables, and calculate the rebound and eject velocities,angles and coefficients (ratio of rebound and eject velocity to incident velocity). Numerical results are found in accordance with current experimental results. The rebound and eject lift-off probabilities versus the incident and creeping velocities are predicted.

  9. The origin of high hydraulic resistance for filter cakes of deformable particles: cell-bed deformation or surface-layer effect?

    OpenAIRE

    Meireles, Martine; Molle, Catherine; Clifton, Michael J.; Aimar, Pierre

    2004-01-01

    International audience; This study reports a numerical approach for modeling the hydraulic resistance of a filter cake of deformable cells. First, a mechanical and osmotic model that describes the volume fraction of solids in a bed of yeast cells as a function of the compressive pressure it experiences is presented. The effects of pressure on the compressibility of yeast cells beds were further investigated both by filtration experiments and by centrifugal experiments based on the multiple sp...

  10. Decadal changes in carbon fluxes at the East Siberian continental margin: interactions of ice cover, ocean productivity, particle sedimentation and benthic life

    Science.gov (United States)

    Boetius, A.; Bienhold, C.; Felden, J.; Fernandez Mendez, M.; Gusky, M.; Rossel, P. E.; Vedenin, A.; Wenzhoefer, F.

    2015-12-01

    The observed and predicted Climate-Carbon-Cryosphere interactions in the Arctic Ocean are likely to alter productivity and carbon fluxes of the Siberian continental margin and adjacent basins. Here, we compare field observations and samples obtained in the nineties, and recently in 2012 during the sea ice minimum, to assess decadal changes in the productivity, export and recycling of organic matter at the outer East Siberian margin. In the 90s, the Laptev Sea margin was still largely ice-covered throughout the year, and the samples and measurements obtained represent an ecological baseline against which current and future ecosystem shifts can be assessed. The POLARSTERN expedition IceArc (ARK-XXVII/3) returned in September 2012 to resample the same transects between 60 and 3400 m water depth as well as stations in the adjacent deep basins. Our results suggest that environmental changes in the past two decades, foremost sea ice thinning and retreat, have led to a substantial increase in phytodetritus sedimentation to the seafloor, especially at the lower margin and adjacent basins. This is reflected in increased benthic microbial activities, leading to higher carbon remineralization rates, especially deeper than 3000 m. Besides a relative increase in typical particle degrading bacterial types in surface sediments, bacterial community composition showed little variation between the two years, suggesting that local microbial communities can cope with changing food input. First assessments of faunal abundances suggest an increase in polychaetes,holothurians and bivalves at depth, which fits the prediction of higher productivity and particle deposition rates upon sea ice retreat. The presentation also discusses the controversial issue whether there is evidence for an Arctic-wide increase in carbon flux, or whether we are looking at a spatial shift of the productive marginal ice zone as the main factor to enhance carbon flux to the deep Siberian margin.

  11. COOLOCE debris bed experiments and simulations investigating the coolability of cylindrical beds with different materials and flow modes

    Energy Technology Data Exchange (ETDEWEB)

    Takasuo, E.; Kinnunen, T.; Holmstroem, S.; Lehtikuusi, T. [VTT Technical Research Centre of Finland (Finland)

    2013-07-15

    The COOLOCE experiments aim at investigating the coolability of debris beds of different geometries, flow modes and materials. A debris bed may be formed of solidified corium as a result of a severe accident in a nuclear power reactor. The COOLOCE-8 test series consisted of experiments with a top-flooded test bed with irregular gravel as the simulant material. The objective was to produce comparison data useful in estimating the effects of different particle materials and the possible effect of the test arrangement on the results. It was found that the dryout heat flux (DHF) measured for the gravel was lower compared to previous experiments with spherical beads, and somewhat lower compared to the early STYX experiments. The difference between the beads and gravel is at least partially explained by the smaller average size of the gravel particles. The COOLOCE-9 test series included scoping experiments examining the effect of subcooling of the water pool in which the debris bed is immersed. The experiments with initially subcooled pool suggest that the subcooling may increase DHF and increase coolability. The aim of the COOLOCE-10 experiments was to investigate the effect of lateral flooding on the DHF a cylindrical test bed. The top of the test cylinder and its sidewall were open to water infiltration. It was found that the DHF is increased compared to a top-flooded cylinder by more than 50%. This suggests that coolability is notably improved. 2D simulations of the top-flooded test beds have been run with the MEWA code. Prior to the simulations, the effective particle diameter for the spherical beads and the irregular gravel was estimated by single-phase pressure loss measurements performed at KTH in Sweden. Parameter variations were done for particle size and porosity used as input in the models. It was found that with the measured effective particle diameter and porosity, the simulation models predict DHF with a relatively good accuracy in the case of spherical

  12. Gas-particle interactions above a Dutch heathland: I. Surface exchange fluxes of NH3, SO2, HNO3 and HCl

    Directory of Open Access Journals (Sweden)

    E. Nemitz

    2004-01-01

    Full Text Available A field measurement campaign was carried out over a Dutch heathland to investigate the effect of gas-to-particle conversion and ammonium aerosol evaporation on surface/atmosphere fluxes of ammonia and related species. Continuous micrometeorological measurements of the surface exchange of NH3, SO2, HNO3 and HCl were made and are analyzed here with regard to average fluxes, deposition velocities (Vd, canopy resistances (Rc and canopy compensation point for NH3. Gradients of SO2, HNO3 and HCl were measured with a novel wet-denuder system with online anion chromatography. Measurements of HNO3 and HCl indicate an Rc of 100 to 200 s m-1 during warm daytime periods, probably at least partly due to non-zero acid partial pressures above NH4NO3 and NH4Cl on the leaf surfaces. Although it is likely that this observation is exacerbated by the effect of the evaporation of airborne NH4+ on the gradient measurements, the findings nevertheless add to the growing evidence that HNO3 and HCl are not always deposited at the maximum rate. Ammonia (NH3 fluxes show mainly deposition, with some periods of significant daytime emission. The net exchange could be reproduced both with an Rc model (deposition fluxes only using resistance parameterizations from former measurements, as well as with the canopy compensation point model, using parameterizations derived from the measurements. The apoplastic ratio of ammonium and hydrogen concentration (Γs=[NH4+]/[H+] of 1200 estimated from the measurements is large for semi-natural vegetation, but smaller than indicated by previous measurements at this site.

  13. Probing the cosmic ray mass composition in the knee region through TeV secondary particle fluxes from solar surroundings

    Science.gov (United States)

    Banik, Prabir; Bijay, Biplab; Sarkar, Samir K.; Bhadra, Arunava

    2017-03-01

    The possibility of estimating the mass composition of primary cosmic rays above the knee of their energy spectrum through the study of high-energy gamma rays, muons, and neutrinos produced in the interactions of cosmic rays with solar ambient matter and radiation is explored. It is found that the theoretical fluxes of TeV gamma rays, muons, and neutrinos from a region around 15° of the Sun are sensitive to a mass composition of cosmic rays in the PeV energy range. The experimental prospects for the detection of such TeV gamma rays/neutrinos by future experiments are discussed.

  14. Influence of gas-particle partitioning on ammonia and nitric acid fluxes above a deciduous forest in the Midwestern USA

    DEFF Research Database (Denmark)

    Hansen, Kristina; Sørensen, Lise Lotte; Hornsby, Karen E.

    Quantifying the atmosphere-biosphere exchange of reactive nitrogen gasses (including ammonia (NH3) and nitric acid (HNO3)) is crucial to assessing the impact of anthropogenic activities on natural and semi-natural ecosystems. However, measuring the deposition of reactive nitrogen is challenging due...... are measured above the deciduous forest, Morgan Monroe State Forest (MMSF) in south-central Indiana (39°53’N, 86°25’W) during a field campaign. Two relaxed eddy accumulation (REA) systems are used to measure fluxes and concentrations of NH3 and HNO3 at 44 m. The NH3 REA system operates based on wet effluent...

  15. A "test of concept" comparison of aerodynamic and mechanical resuspension mechanisms for particles deposited on field rye grass ( Secale cercele).—Part 2. Threshold mechanical energies for resuspension particle fluxes

    Science.gov (United States)

    Gillette, Dale A.; Lawson, Robert E.; Thompson, Roger S.

    Kinetic energy from the oscillatory impacts of the grass stalk against a stationary object was measured with a kinetic energy measuring device. These energy inputs were measured as part of a resuspension experiment of uniform latex microspheres deposited on a single rye grass seed pod in a wind tunnel. The experiment was designed to measure resuspension from aerodynamic (viscous and turbulent) mechanisms compared to that from mechanisms from mechanical resuspension resulting from the oscillatory impact of the grass hitting a stationary object. The experiment was run for deposited spherical latex particles with diameters from 2 to 8.1 μm. Wind tunnel tests were run for wind speeds from 2 to 18.5 m s -1 and a turbulence intensity (root-mean-square fluctuation wind speed/mean wind speed) of 0.1. Our experiments showed the following: Threshold mechanical energy input rates increased from 0.04 to 0.2 μJ s -1 for resuspension of spherical polystyrene latex particles from 2 to 8.1 μm diameter. Kinetic energy flux generated by mechanical impact of the wind-driven oscillating grass was found to be highly sensitive to slightly different placements and grass morphology. The kinetic energy input by impaction of the grass against a stationary cylinder is roughly proportional to the kinetic energy flux of the wind.

  16. Waste tyre pyrolysis: modelling of a moving bed reactor.

    Science.gov (United States)

    Aylón, E; Fernández-Colino, A; Murillo, R; Grasa, G; Navarro, M V; García, T; Mastral, A M

    2010-12-01

    This paper describes the development of a new model for waste tyre pyrolysis in a moving bed reactor. This model comprises three different sub-models: a kinetic sub-model that predicts solid conversion in terms of reaction time and temperature, a heat transfer sub-model that calculates the temperature profile inside the particle and the energy flux from the surroundings to the tyre particles and, finally, a hydrodynamic model that predicts the solid flow pattern inside the reactor. These three sub-models have been integrated in order to develop a comprehensive reactor model. Experimental results were obtained in a continuous moving bed reactor and used to validate model predictions, with good approximation achieved between the experimental and simulated results. In addition, a parametric study of the model was carried out, which showed that tyre particle heating is clearly faster than average particle residence time inside the reactor. Therefore, this fast particle heating together with fast reaction kinetics enables total solid conversion to be achieved in this system in accordance with the predictive model.

  17. Impact of open-ocean convection on particle fluxes and sediment dynamics in the deep margin of the Gulf of Lions

    Directory of Open Access Journals (Sweden)

    M. Stabholz

    2013-02-01

    Full Text Available The deep outer margin of the Gulf of Lions and the adjacent basin, in the western Mediterranean Sea, are regularly impacted by open-ocean convection, a major hydrodynamic event responsible for the ventilation of the deep water in the western Mediterranean Basin. However, the impact of open-ocean convection on the flux and transport of particulate matter remains poorly understood. The variability of water mass properties (i.e., temperature and salinity, currents, and particle fluxes were monitored between September 2007 and April 2009 at five instrumented mooring lines deployed between 2050 and 2350-m depth in the deepest continental margin and adjacent basin. Four of the lines followed a NW–SE transect, while the fifth one was located on a sediment wave field to the west. The results of the main, central line SC2350 ("LION" located at 42°02.5′ N, 4°41′ E, at 2350-m depth, show that open-ocean convection reached mid-water depth (≈ 1000-m depth during winter 2007–2008, and reached the seabed (≈ 2350-m depth during winter 2008–2009. Horizontal currents were unusually strong with speeds up to 39 cm s−1 during winter 2008–2009. The measurements at all 5 different locations indicate that mid-depth and near-bottom currents and particle fluxes gave relatively consistent values of similar magnitude across the study area except during winter 2008–2009, when near-bottom fluxes abruptly increased by one to two orders of magnitude. Particulate organic carbon contents, which generally vary between 3 and 5%, were abnormally low (≤ 1% during winter 2008–2009 and approached those observed in surface sediments (≈ 0.6%. Turbidity profiles made in the region demonstrated the existence of a bottom nepheloid layer, several hundred meters thick, and related to the resuspension of bottom sediments. These observations support the view that open-ocean deep convection events in the Gulf of Lions can cause significant remobilization

  18. Impact of open-ocean convection on particle fluxes and sediment dynamics in the deep margin of the Gulf of Lions

    Science.gov (United States)

    Stabholz, M.; Durrieu de Madron, X.; Canals, M.; Khripounoff, A.; Taupier-Letage, I.; Testor, P.; Heussner, S.; Kerhervé, P.; Delsaut, N.; Houpert, L.; Lastras, G.; Dennielou, B.

    2013-02-01

    The deep outer margin of the Gulf of Lions and the adjacent basin, in the western Mediterranean Sea, are regularly impacted by open-ocean convection, a major hydrodynamic event responsible for the ventilation of the deep water in the western Mediterranean Basin. However, the impact of open-ocean convection on the flux and transport of particulate matter remains poorly understood. The variability of water mass properties (i.e., temperature and salinity), currents, and particle fluxes were monitored between September 2007 and April 2009 at five instrumented mooring lines deployed between 2050 and 2350-m depth in the deepest continental margin and adjacent basin. Four of the lines followed a NW-SE transect, while the fifth one was located on a sediment wave field to the west. The results of the main, central line SC2350 ("LION") located at 42°02.5' N, 4°41' E, at 2350-m depth, show that open-ocean convection reached mid-water depth (≍ 1000-m depth) during winter 2007-2008, and reached the seabed (≍ 2350-m depth) during winter 2008-2009. Horizontal currents were unusually strong with speeds up to 39 cm s-1 during winter 2008-2009. The measurements at all 5 different locations indicate that mid-depth and near-bottom currents and particle fluxes gave relatively consistent values of similar magnitude across the study area except during winter 2008-2009, when near-bottom fluxes abruptly increased by one to two orders of magnitude. Particulate organic carbon contents, which generally vary between 3 and 5%, were abnormally low (≤ 1%) during winter 2008-2009 and approached those observed in surface sediments (≍ 0.6%). Turbidity profiles made in the region demonstrated the existence of a bottom nepheloid layer, several hundred meters thick, and related to the resuspension of bottom sediments. These observations support the view that open-ocean deep convection events in the Gulf of Lions can cause significant remobilization of sediments in the deep outer margin and

  19. Heat transfer characteristics of the fluidized bed through the annulus

    Science.gov (United States)

    Shedid, Mohamed H.; Hassan, M. A. M.

    2016-09-01

    The annular fluidized bed can be regarded as a promising technique for waste heat recovery applications. This study investigates on the determination of steady state values of the average heat transfer on the surface of the inner tube under different operating conditions that include: (1) input heat flux ranging from 557 to 1671 W/m2, (2) superficial air velocity ranging between 0.12 and 0.36 m/s, (3) initial bed height ranging from 25 to 55 cm, (4) ratio of the inner to the outer diameters ranging from 1/6 to 1/2 and Kaolin particle diameters ranging between 282 and 550 µm. The average values of the heat transfer coefficient along the inner tube (consisting of the fluidized and free board sections) are also deduced. An empirical correlation for calculating the Nusselt number is obtained for the given parameters and ranges.

  20. Free running droplets on packed powder beds

    Science.gov (United States)

    Whitby, Catherine P.; Bian, Xun; Sedev, Rossen

    2013-06-01

    We observed that water drops placed on horizontal beds of fine molybdenite particles move freely over the bed surface for about 1 second. The drops collect an irregular coating of unevenly distributed particles as they bounce and roll. We manipulated the distance that the drops travel, and hence the area of the droplet surface coated with particles, by varying the water surface tension and the kinetic energy of the initial droplet impact on the bed surface. Our results highlight the role of contact angle hysteresis in particle encapsulation of liquid drops.

  1. A New Method for Measurement of Local Solid Flux in Gas-Solid Two-phase Flow

    Institute of Scientific and Technical Information of China (English)

    鄂承林; 卢春善; 徐春明; 高金森; 时铭显

    2003-01-01

    Previous works have shown that the suction probe cannot be used to accurately measure the upward and downward particle fluxes independently. A new method using a single optical probe to measure the local solid flux is presented. The measurement of upward, downward and net solid fluxes was carried out in a cold model circulating fluidized bed (CFB) unit. The result shows that the profile of the net solid flux is in good agreement with the previous experimental data measured with a suction probe. The comparison between the average solid flux determined with the optical measuring system and the external solid flux was made, and the maximum deviationturned out to be 22%, with the average error being about 6.9%. These confirm that the optical fiber system can be successfully used to measure the upward, downward and net solid fluxes simultaneously by correctly processing the sampling signals obtained from the optical measuring system.

  2. Particle size distribution of ashes and the behaviour of metals when firing Salix in a circulating fluidized bed boiler (CFB); Askans partikelfraktionsfoerdelning och metallernas beteende vid eldning av Salix i en CFB-panna

    Energy Technology Data Exchange (ETDEWEB)

    Sfiris, G.; Johansson, A. [Vattenfall Utveckling AB, Stockholm (Sweden); Valmari, T.; Kauppinen, E.; Pyykoenen, J.; Lyyraenen, J. [VTT Technical Research Centre of Finland, Espoo (Finland)

    1999-07-01

    This project is part of the Ash Recovery Programme aimed at establishing the environmental, technical and financial preconditions for returning wood ash to the forest. The programme is funded jointly by NUTEK, Sydkraft and Vattenfall. This report summarises the results of the experimental and modelling work to study the behaviour of the metals (especially Cd and K), after burning Salix in a 3-12 MW Circulating Fluidized Bed (CFB) boiler. The purpose of the study was to determine, using the experimental data, where cadmium and potassium condense, on what size particles they condense, and the decisive parameters governing these processes. Measurements of the fly ash particle size distribution carried out with a Berner Low Pressure Impactor (BLPI), coupled to a pre-cyclone. Samples were collected from three points: in the convection path at 650 deg C, after the convection path but before the secondary cyclone (160 deg C), and after the bag house (150 deg C). Wet chemical sampling was made for Cd, K, Zn and Pb, with three types of sampling equipment: collection of both particles and gas, collection of particles only, and analysis of the gas phase only. Analysis was made of samples from two places in the convection path (650 deg C and 250 deg C). Samples of bed material, bottom ash and fly ash have been subjected to scanning electron microscopy (SEM), and in addition a few fly ash particles, sampled after the convection path, were subjected to energy dispersive X-ray analysis (EDX). Based on experimental results, modelling work was carried out with an equilibrium model and with a general aerosol computer model ABC (Aerosol Behaviour in Combustion)

  3. Hydrodynamics of gas-solids downflow fluidized bed (downer) reactor

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, H.

    1999-07-01

    This study presents a semi-empirical model for the hydrodynamic flow structure in a circulating fluidized bed downer reactor. Circulating fluidized bed, or riser reactors are used in the petroleum industry for many applications including catalytic cracking, polyethylene production, calcination operations and combustion of a variety of fuels. The work in this thesis involved the development of a circulating fluidized bed riser and downer system that enables hydrodynamic studies to be carried out. The system was designed to incorporate both a riser and a downer in the same circulating operation, making it possible to conduct experimental studies on the riser and the downer separately or simultaneously. The hydrodynamics of the gas-solids downflow fluidized bed reactor were studied in a 9.3 m tall and 0.1 m i.d. circulating fluidized bed downer reactor using fluidized cracking catalyst (FCC) particles. In order to characterize the gas-solids flow structures, the following three parameters were measured: the radial distributions of the local solids holdups, the local particle velocities, and the pressure gradients along the downer column. The hydrodynamics in the co-current downflow reactor was also studied under a wide range of operating conditions. The gas-solids flow structure under zero superficial gas velocity conditions was characterized by measuring the radial distribution of the local solids holdups and particle velocities along the downer column with the superficial gas velocity set to zero. The results indicate that two basic flow regimes exist in the FCC downer system depending on the superficial gas velocity. The downer reactor was shown to have a more uniform radial flow structure compared to the riser. It also has a more uniform radial distribution of solids holdup and particle velocity as well as solids flux in both the development and fully developed zones. The highly uniform radial flow structure provides a nearly ideal plug flow condition in the

  4. The Real-Time Data Analysis and Decision System for Particle Flux Detection in the LHC Accelerator at CERN.

    CERN Document Server

    Zamantzas, C; Dehning, B

    2006-01-01

    The superconducting Large Hadron Collider (LHC) under construction at the European Organisation for Nuclear Research (CERN) is an accelerator unprecedented in terms of beam energy, particle production rate and also in the potential of self-destruction. Its operation requires a large variety of instrumentation, not only for the control of the beams, but also for the protection of the complex hardware systems. The Beam Loss Monitoring (BLM) system has to prevent the superconducting magnets from becoming normal conducting and protect the machine components against damages making it one of the most critical elements for the protection of the LHC. For its operation, the system requires 3600 detectors to be placed at various locations around the 27 km ring. The measurement system is sub-divided to the tunnel electronics, which are responsible for acquiring, digitising and transmitting the data, and the surface electronics, which receive the data via 2 km optical data links, process, analyze, store and issue warning...

  5. Packed fluidized bed blanket for fusion reactor

    Science.gov (United States)

    Chi, John W. H.

    1984-01-01

    A packed fluidized bed blanket for a fusion reactor providing for efficient radiation absorption for energy recovery, efficient neutron absorption for nuclear transformations, ease of blanket removal, processing and replacement, and on-line fueling/refueling. The blanket of the reactor contains a bed of stationary particles during reactor operation, cooled by a radial flow of coolant. During fueling/refueling, an axial flow is introduced into the bed in stages at various axial locations to fluidize the bed. When desired, the fluidization flow can be used to remove particles from the blanket.

  6. Unsteady void measurements within debris beds using high speed X-ray tomography

    Energy Technology Data Exchange (ETDEWEB)

    Laurien, E., E-mail: Laurien@ike.uni-stuttgart.de; Stürzel, T., E-mail: thilo.stuerzel@stihl.de; Zhou, M., E-mail: mi.zhou@ike.uni-stuttgart.de

    2017-02-15

    Highlights: • A high speed X-ray tomography facility has been built for the investigation on two-phase flow. • The two-phase flow through beds of packed plastic spheres has been investigated in the facility. • 3D-reconstructions from the measurements show the fluxes in the two-phase flow. • The gas fraction has been calculated from the reconstruction and used for validation of the modeling. • A new bed with closest regular spheres arrangement has been manufactured by 3D-plotter and used in the measurement. - Abstract: Two-phase flow and boiling within debris beds representing a destroyed reactor core after a severe accident with core fragmentation can be simulated by using the porous media approach. In this approach, a local pressure drop and the heat transfer between the solid debris particles and the two-phase flow is modelled with the help flow-pattern maps, in which the boundaries between bubbly, slug, and annular flow are assumed. In order to support further understanding of these flows we have developed a very fast X-ray measurement device to visualize the 3D-void distribution within particle beds or porous media, which are otherwise un-accessible internally. The experimental setup uses a scanned electron beam directed in circles on a tungsten target to generate the X-rays. The particle bed, which has a diameter of 70 mm, is located between this target and a field of 256 X-ray detectors, which are arranged on a circle concentric to the target. The void distribution is reconstructed numerically from the attenuation of signals, which penetrates the particle bed and the two-phase flow inside. A 3D frame rate of up to 1000 Hz can be reached. The spatial resolution is such that bubbles with a diameter > 1.7 mm can be detected. We have investigated two-phase flows air/water through beds of packed plastic spheres (diameter between 3 and 15 mm) as well as through plastic beds, which were manufactured using a ‘3D-plotter’. Flow patterns can be

  7. Magnetized retarding field energy analyzer measuring the particle flux and ion energy distribution of both positive and negative ions.

    Science.gov (United States)

    Rafalskyi, Dmytro; Dudin, Stanislav; Aanesland, Ane

    2015-05-01

    This paper presents the development of a magnetized retarding field energy analyzer (MRFEA) used for positive and negative ion analysis. The two-stage analyzer combines a magnetic electron barrier and an electrostatic ion energy barrier allowing both positive and negative ions to be analyzed without the influence of electrons (co-extracted or created downstream). An optimal design of the MRFEA for ion-ion beams has been achieved by a comparative study of three different MRFEA configurations, and from this, scaling laws of an optimal magnetic field strength and topology have been deduced. The optimal design consists of a uniform magnetic field barrier created in a rectangular channel and an electrostatic barrier consisting of a single grid and a collector placed behind the magnetic field. The magnetic barrier alone provides an electron suppression ratio inside the analyzer of up to 6000, while keeping the ion energy resolution below 5 eV. The effective ion transparency combining the magnetic and electrostatic sections of the MRFEA is measured as a function of the ion energy. It is found that the ion transparency of the magnetic barrier increases almost linearly with increasing ion energy in the low-energy range (below 200 eV) and saturates at high ion energies. The ion transparency of the electrostatic section is almost constant and close to the optical transparency of the entrance grid. We show here that the MRFEA can provide both accurate ion flux and ion energy distribution measurements in various experimental setups with ion beams or plasmas run at low pressure and with ion energies above 10 eV.

  8. Effects of particle size and dry matter content of a total mixed ration on intraruminal equilibration and net portal flux of volatile fatty acids in lactating dairy cows

    DEFF Research Database (Denmark)

    Storm, Adam Christian; Kristensen, Niels Bastian

    2010-01-01

    Effects of physical changes in consistency of ruminal contents on intraruminal equilibration and net portal fluxes of volatile fatty acids (VFA) in dairy cows were studied. Four Danish Holstein cows (121 ± 17 d in milk, 591 ± 24 kg of body weight, mean ± SD) surgically fitted with a ruminal cannula......H or milk fat percentage. Cows maintained average ventral ruminal pH of 6.65 ± 0.02, medial ruminal pH of 5.95 ± 0.04, and milk fat of 4.42 ± 0.12% with chewing time of 28.0 ± 2.1 min/kg of DM when fed short particles. The medial ruminal pool of wet particulate matter was decreased by 10.53 ± 2.29 kg...... particles. The estimated ruminal fluid flow and therefore intraruminal VFA transport between medial and ventral phase was not affected by the FPS. In conclusion, the ruminal mat pool of VFA was proportional to the size of the mat and the only detected effects of decreasing FPS were decreasing the mat size...

  9. Modelling the bed characteristics in fluidised-beds for top-spray coating processes

    Institute of Scientific and Technical Information of China (English)

    Mike Vanderroost; Frederik Ronsse; Koen Dewettinck; Jan G.Pieters

    2012-01-01

    A particle sub-model describing the bed characteristics of a bubbling fluidised bed is presented.Atomisation air,applied at high pressures via a nozzle positioned above the bed for s pray formation,is incorporated in the model since its presence has a profound influence on the bed characteristics,though the spray itself is not yet considered.A particle sub-model is developed using well-known empirical relations for particle drag force,bubble growth and velocity and particle distribution above the fluidised-bed surface.Simple but effective assumptions and abstractions were made concerning bubble distribution,particle ejection at the bed surface and the behaviour of atomisation air flow upon impacting the surface of a bubbling fluidised bed.The model was shown to be capable of predicting the fluidised bed characteristics in terms of bed heights,voidage distributions and solids volume fractions with good accuracy in less than 5 min of calculation time on a regular desktop PC.It is therefore suitable for incorporation into general process control models aimed at dynamic control for process efficiency and product quality in top-spray fluidised bed coating processes.

  10. Experimental investigation on the changes in bed properties of a ...

    African Journals Online (AJOL)

    user

    pressure measurements, physical observation, sampling of bed particles, bed ... air and producer gas flow rates, etc. were observed and analyzed during the ... The experimental system consists of centrifugal blower, downdraft gasifier, flare ...

  11. In situ measurement of mesopelagic particle sinking rates and the control of carbon transfer to the ocean interior during the Vertical Flux in the Global Ocean (VERTIGO) voyages in the North Pacific

    Science.gov (United States)

    Trull, T. W.; Bray, S. G.; Buesseler, K. O.; Lamborg, C. H.; Manganini, S.; Moy, C.; Valdes, J.

    2008-07-01

    Among the parameters affecting carbon transfer to the ocean interior, particle sinking rates vary three orders of magnitude and thus more than primary production, f-ratios, or particle carbon contents [e.g., Boyd, P.W., Trull, T.W., 2006. Understanding the export of marine biogenic particles: is there consensus? Progress in Oceanography 4, 276-312, doi:10.1016/j.pocean.2006.10.007]. Very few data have been obtained from the mesopelagic zone where the majority of carbon remineralization occurs and the attenuation of the sinking flux is determined. Here, we report sinking rates from ˜300 m depth for the subtropical (station ALOHA, June 2004) and subarctic (station K2, July 2005) North Pacific Ocean, obtained from short (6.5 day) deployments of an indented rotating sphere (IRS) sediment trap operating as an in situ settling column [Peterson, M.L., Wakeham, S.G., Lee, C., Askea, M.A., Miquel, J.C., 2005. Novel techniques for collection of sinking particles in the ocean and determining their settling rates. Limnology and Oceanography Methods 3, 520-532] to separate the flux into 11 sinking-rate fractions ranging from >820 to >2 m d -1 that are collected by a carousel for further analysis. Functioning of the IRS trap was tested using a novel programming sequence to check that all particles have cleared the settling column prior to the next delivery of particles by the 6-hourly rotation cycle of the IRS. There was some evidence (from the flux distribution among the cups and photomicroscopy of the collected particles) that very slow-sinking particles may have been under-collected because they were unable to penetrate the brine-filled collection cups, but good evidence for appropriate collection of fast-settling fractions. Approximately 50% of the particulate organic carbon (POC) flux was sinking at greater than 100 m d -1 at both stations. At ALOHA, more than 15% of the POC flux sank at >820 m d -1, but low fluxes make this uncertain, and precluded resolution of particles

  12. Effective Thermal Conductivity of Adsorbent Packed Beds

    Science.gov (United States)

    Mori, Hideo; Hamamoto, Yoshinori; Yoshida, Suguru

    The effective thermal conductivity of adsorbent packed beds of granular zeolite 13X and granular silica gel A in the presence of stagnant steam or air was measured under different conditions of the adsorbent bed temperature, particle size and filler-gas pressure. The measured effective thermal conductivity showed to become smaller with decreasing particle size or decreasing pressure, but it was nearly independent of the bed temperature. When steam was the filler-gas, the rise in the thermal conductivity of the adsorbent particles due to steam adsorption led to the increase in the effective thermal conductivity of the bed, and this effect was not negligible at high steam pressure for the bed of large particle size. It was found that both the predictions of the effective thermal conductivity by the Hayashi et al.'s model and the Bauer-Schlünder model generally agreed well with the measurements, by considering the particle thermal conductivity rise due to steam adsorption. The thermal conductivity of a consolidated bed of granular zeolite 13X was also measured, and it was found to be much larger than that of the packed bed especially at lower pressure. The above prediction models underestimated the effective thermal conductivity of the consolidated bed.

  13. Experimental and numerical analysis of turbulence/mobile-bed interactions

    Science.gov (United States)

    Revil-Baudard, Thibaud; Chauchat, Julien; Hurther, David; Hsu, Tian-Jian; Cheng, Zhen

    2017-04-01

    Highly resoluted and co-located velocity and concentration measurements have been obtained by using an Acoustic Concentration and Velocity Profiler (ACVP) in an intense sediment transport laboratory experiment. This dataset is used to investigate the complex coupling between the turbulent fluid motion and the sediment bed. It has been shown that the bed interface position is highly intermittent because of the impact of the large-scale coherent structures. The important contribution of the streamwise turbulent fluxes observed close to the sediment bed might be related to the bed-intermittency. In return, the mobile bed affects the turbulent fluid flow. It is shown that the turbulent kinetic energy is enhanced by the bed-mobility compared with a similar clear-water flow. However the streamwise and wall-normal velocity fluctuations are observed to be less correlated in the suspension region, resulting in a reduced efficiency of turbulence for momentum mixing. In the suspension region, the turbulent particle diffusivity is shown to be twice greater than the momentum diffusivity. Two possible mechanisms might provide an explanation for this feature. First, the increased contribution of the so-called interaction turbulent events tend to increase the velocity gradients, consistently with a drop of momentum mixing. These interactions events are also efficient to increase particle dispersion and hence to increase concentration mixing. Second, the turbulent particle diffusivity is directly proportional to the particle settling velocity which is classically taken as the one measured or computed in still-water conditions. However, different mechanisms highlighted in the literatures imply a turbulence-induced modification of the settling velocity. This modification could partly explain why the turbulent concentration mixing appears to be more efficient than the momentum one in sediment-laden flows. These experimental results are utilized to improve the sub-grid dissipation and

  14. Debris-bed friction of hard-bedded glaciers

    Science.gov (United States)

    Cohen, D.; Iverson, N.R.; Hooyer, T.S.; Fischer, U.H.; Jackson, M.; Moore, P.L.

    2005-01-01

    [1] Field measurements of debris-bed friction on a smooth rock tablet at the bed of Engabreen, a hard-bedded, temperate glacier in northern Norway, indicated that basal ice containing 10% debris by volume exerted local shear traction of up to 500 kPa. The corresponding bulk friction coefficient between the dirty basal ice and the tablet was between 0.05 and 0.08. A model of friction in which nonrotating spherical rock particles are held in frictional contact with the bed by bed-normal ice flow can account for these measurements if the power law exponent for ice flowing past large clasts is 1. A small exponent (n glacier sliding at 20 m a-1 with a geothermally induced melt rate of 0.006 m a-1 and an effective pressure of 300 kPa can exceed 100 kPa. Debris-bed friction can therefore be a major component of sliding resistance, contradicting the common assumption that debris-bed friction is negligible. Copyright 2005 by the American Geophysical Union.

  15. Experiments on the dryout behavior of stratified debris beds

    Energy Technology Data Exchange (ETDEWEB)

    Leininger, Simon; Kulenovic, Rudi; Laurien, Eckart [Stuttgart Univ. (Germany). Inst. of Nuclear Technology and Energy Systems (IKE)

    2015-10-15

    In case of a severe accident with loss of coolant and core meltdown a particle bed (debris) can be formed. The removal of decay heat from the debris bed is of prime importance for the bed's long-term coolability to guarantee the integrity of the RPV. In contrast to previous experiments, the focus is on stratified beds. The experiments have pointed out that the bed's coolability is significantly affected.

  16. First Results from Colorado Student Space Weather Experiment (CSSWE): Differential Flux Measurements of Energetic Particles in a Highly Inclined Low Earth Orbit

    Science.gov (United States)

    Li, X.; Palo, S. E.; Kohnert, R.; Gerhardt, D.; Blum, L. W.; Schiller, Q.; Turner, D. L.; Tu, W.

    2012-12-01

    The Colorado Student Space Weather Experiment (CSSWE) is a 3-unit (10cm x 10cm x 30cm) CubeSat mission funded by the National Science Foundation, scheduled for launch into a low-Earth, polar orbit after August 14th, 2012 as a secondary payload under NASA's Educational Launch of Nanosatellites (ELaNa) program. The science objectives of CSSWE are to investigate the relationship of the location, magnitude, and frequency of solar flares to the timing, duration, and energy spectrum of solar energetic particles (SEP) reaching Earth, and to determine the precipitation loss and the evolution of the energy spectrum of radiation belt electrons. CSSWE contains a single science payload, the Relativistic Electron and Proton Telescope integrated little experiment (REPTile), which is a miniaturization of the Relativistic Electron and Proton Telescope (REPT) built at the Laboratory for Atmospheric and Space Physics (LASP). The REPT instrument will fly onboard the NASA/Radiation Belt Storm Probes (RBSP) mission, which consists of two identical spacecraft scheduled to launch after August 23rd, 2012 that will go through the heart of the radiation belts in a low inclination orbit. CSSWE's REPTile is designed to measure the directional differential flux of protons ranging from 10 to 40 MeV and electrons from 0.5 to >3 MeV. Such differential flux measurements have significant science value, and a number of engineering challenges were overcome to enable these clean measurements to be made under the mass and power limits of a CubeSat. The CSSWE is an ideal class project, providing training for the next generation of engineers and scientists over the full life-cycle of a satellite project. We will report the first results from this exciting mission.

  17. Propagation of a spherical shock wave in mixture of non-ideal gas and small solid particles under gravitational field with conductive and radiative heat fluxes

    Science.gov (United States)

    Nath, Gorakh

    Self-similar solutions are obtained for one-dimensional unsteady adiabatic flow behind a spherical shock wave propagating in a dusty gas with conductive and radiative heat fluxes under a gravitational field. The shock is assumed to be driven out by a moving piston and the dusty gas to be a mixture of non-ideal (or perfect) gas and small solid particles, in which solid particles are continuously distributed. It is assumed that the equilibrium flow-conditions are maintained and variable energy input is continuously supplied by the piston. The heat conduction is express in terms of Fourier’s law and the radiation is considered to be of the diffusion type for an optically thick grey gas model. The thermal conductivity and the absorption coefficient are assumed to vary with temperature and density. The medium is assumed to be under a gravitational field due to heavy nucleus at the origin (Roche Model). The unsteady model of Roche consists of a dusty gas distributed with spherical symmetry around a nucleus having large mass It is assumed that the gravitational effect of the mixture itself can be neglected compared with the attraction of the heavy nucleus. The density of the ambient medium is taken to be constant. Our analysis reveals that after inclusion of gravitational field effect surprisingly the shock strength increases and remarkable difference can be found in the distribution of flow variables. The effects of the variation of the heat transfer parameters, the gravitational parameter and non-idealness of the gas in the mixture are investigated. Also, the effects of an increase in (i) the mass concentration of solid particles in the mixture and (ii) the ratio of the density of solid particles to the initial density of the gas on the flow variables are investigated. It is found that the shock strength is increased with an increase in the value of gravitational parameter. Further, it is investigated that the presence of gravitational field increases the

  18. Experiments on effects of coal particle ash content on ash formation during fluidized bed combustion%流化床燃烧中煤含灰量对灰渣形成特性的影响

    Institute of Scientific and Technical Information of China (English)

    王勤辉; 徐志; 刘彦鹏; 骆仲泱; 倪明江

    2012-01-01

    为了研究煤颗粒灰质量分数对煤在流化床燃烧过程中灰渣形成特性的影响,在一台小型流化床反应炉上进行煤的灰质量分数对灰渣形成特性的实验.按煤颗粒的灰质量分数,把义马烟煤分为6个颗粒组,并选用各颗粒组的3个粒径范围的煤颗粒进行燃烧实验,研究煤颗粒的灰质量分数对底渣质量分数、底渣与飞灰中的碳量质量分数和粒径分布的影响.结果表明,随着煤颗粒灰质量分数的增加,燃烧形成的底渣质量分数增加,而煤颗粒的燃尽率和飞灰中的碳质量分数都降低.在粒径和燃烧时间相同的条件下,随着颗粒灰质量分数的增加,底渣中留在本粒径档的颗粒质量分数明显增加,而细颗粒的质量分数明显减少.而颗粒灰质量分数对飞灰的粒径分布没有明显的影响.%To investigate the influences of coal particle ash content on the ash formation behaviors during fluidized bed combustion, experiments were conducted on a bench-scale fluidized bed combustor. Yima bituminous coal samples were divided into 6 ranks with different ash content. For every rank of coal sample, 3 size ranges were used in the experiments. The results show that the mass fraction of the bottom residue increases with the ash content of the coal particles, while the burnout of coal particles and the carbon content of the fly ash decrease with the ash content of coal particles. The mass fraction of the bottom residues which have the same size range as the initial size range of the coal particles increases with the ash content. While the ash content of coal particles has no obvious influence on the size distribution of the fly ash.

  19. Incipient motion of gravel and coal beds

    Indian Academy of Sciences (India)

    Subhasish Dey; Uddaraju V Raju

    2002-10-01

    An experimental study on incipient motion of gravel and coal beds under unidirectional steady-uniform flow is presented. Experiments were carried out in a flume with various sizes of gravel and coal samples. The critical bed shear stresses for the