Glass Beads In Water Research Articles

Critical mechanical behavior in the fluid/solid transition of suspensions

Velocity and attenuation measurements of compressional waves at 3 and 5 MHz, as a function of solid volume concentration, are reported for different suspensions. The suspensions were made of 1 μm size particles of kaolinite or glass beads in water or light oil. At a volume concentration of 40%, a sharp peak in attenuation accompanied by a change in velocity is observed. The volume concentration at which this peak occurs is independent of frequency and particle geometry. The observed critical change in attenuation around 40% is consistent with an excess attenuation induced by the fluid-shearing processes between neighboring particles, and corresponds to the jamming point concentration predicted by particle packing simulations.

A thermodynamically consistent rate-dependent model for turbulent two-phase flows

The averaged equations of motion including the Clausius-Duhem inequality for multiphase mixtures are considered and the thermodynamics of the mean motion is studied. Based on the averaged entropy inequality, constitutive equations are formulated, and the thermodynamical constraints on material parameters are obtained. The resulting expressions for phasic stresses are anisotropic, rate-dependent and exhibit normal stress effects. It is shown that the present theory contains the recently developed turbulence models for dilute two-phase flows and kinetic models for dense granular flows as special cases. Using these limiting conditions, the material coefficients of the model for a two-phase mixture are evaluated. The special case of simple shear flows of dense two-phase mixtures are studied in details. It is shown that the model predictions are in good agreement with the experimental data for glass beads in water and air.

Critical Behavior in the Ultrasonic Properties of Suspensions

ABSTRACTVelocity and attenuation measurements of compressional waves at 3 and 5 MHz are presented for suspensions made of 1μm size particles of kaolinite or glass beads in water or light oil. At a critical concentration of 40%, the attenuation shows a sharp peak in attenuation as well as a sudden change in velocity. This behavior is observed in all suspensions and is independent of frequency or particle geometry. The observed behavior is consistent, with the excess attenuation induced by the fluid-shearing between particles. This behavior is the first experimental evidence for the existance of the freezing point, predicted by computer simulations.

The effect of iron on the survival of Vibrio cholerae O1 in dechlorinated tap water

Many factors, such as temperature, pH, organic nutrients, types of water storage containers, etc., determine the survival of Vibrio cholerae in water. Since the survival of V. cholerae O1 has been shown to be much longer in metal drums used as household water storage containers than in clay pots and plastic drums, the present study was designed to explore the possible role played by insoluble iron on the survival of V. cholerae O1 in water. The possibility of iron acting as paniculate matter for the organisms to adhere to was also examined by using inert glass beads in water. Survival of V. cholerae O1 in dechlorinated tap water, with and without inert glass beads, ranged from <24 h to 10 d. The number of surviving bacteria was, however, very low. In the presence of impure ferric oxide (Fe 2O 3), survival in tap water ranged from 4 to 12 d and the numbers of surviving bacteria were very high. Iron was thought to play an important role in the survival of V. cholerae O1 in water. Differences between the numbers of bacteria and the length of survival in surface water and in sediment were unremarkable. The El Tor and classical biotypes gave similar results.

Sound propagation in suspensions and acoustic imaging of their microstructure

Ultrasound, as a technique for interrogating two-phase mixtures, has the advantages of being non-intrusive, it has good temporal resolution, and can be made to penetrate typically opaque, highly concentrated mixtures without resorting to acoustic impedance matching. Sound propagation characteristics in a mixture depend on the size of the particles, their concentration, the material properties of the two phases, and are sensitive to the wavenumber, k = 2π ψ , of sound. A combined theoretical and experimental investigation was conducted to quantify attenuation and sound speed in mono-disperse mixtures to provide a quantitative framework to interpret acoustic data and extract information on the microstructure of flowing, very concentrated solid—liquid mixtures. This paper builds upon this work to identify the role of microstructure on acoustic propagation in suspensions, in the limit of long wavelengths, and the results are then used to choose suitable operating frequencies to image a liquefaction event in a bed of 50 μm glass beads in water.

Hydrodynamic behaviour of three-phase (gas—liquid—solid) airlift reactors

The hydrodynamic behaviour of three-phase (gas—liquid—solid) airlift (TPAL) reactors have been studied using internal-loop reactors and the air—water—glass beads system. A hydrodynamic model has been developed which considers the reactor to be comprised of riser and downcomer regions. The uneven distribution of the solid particles between these regions leads to the effective densities of the liquid—solid mixtures being different between these regions. This effect is used to explain reactor stalling at low superficial gas velocities, and also to predict the effect of increasing concentration of solid particles and increasing solid particle settling velocities on reactor performance. The model can be used to predict both critical gas velocity for solids suspension and recirculating liquid velocity in the reactor. This hydrodynamic model has been tested experimentally using TPAL reactors ranging in diameters from 0.11 to 0.155 m, and in height from 1.0 to 2.0 m. The effects of superficial gas velocity, solid particle loading, particle diameter, draft tube diameter and draft tube height on the liquid recirculation velocity in the riser section ( U LR ) and critical gas velocity at stalling ( U Gcrit ) were investigated experimentally. U LR was found to increase with draft tube height and to decrease with draft tube diameter. Increasing solids loading or settling velocity increased U Gcrit . The set of conditions under which the TPAL reactors stalled were found to be the same whether approached via a decreasing gas velocity and a fixed quantity of solids, or a increasing quantity of solids and a fixed gas velocity. The hydrodynamics model predicted U LR well (within 30%) and U Gerit well (within 10%) when simplifying assumptions regarding the head loss coefficients and downcomer gas holdup were made. At gas velocities above 0.03 ms −1, the assumption that the gas holdup in the downcomer region was negligible (made in the absence of suitable information on this parameter) became invalid, and the hydrodynamic model predicted too-high recirculation velocities.

Rate analysis of freeze drying in liquid foods. Part I. Rate analysis of freeze drying of a model system by a uniformly retreating ice front model.

Prior to investigating the freeze drying of liquid foods, the freeze drying of a water-glass bead system was analyzed by a conventional uniformly retreating ice front (URIF) model. The drying rate gradually changed as drying proceeded (phase I) until a certain critical time, and then sharply decreased (phase II), probably due to instability in the sublimation plane. The apparent thermal conductivity of the frozen layer estimated by using the drying data from phase I agreed well with the thermal conductivity calculated by the Kunii-Smith model. This result shows that the heat flow through the dry layer, to which both heat conduction and heat transfer accompanied by vapor flow would contribute, was small enough compared with that from a heater in the present drying system. The drying rate and the temperature of the frozen layer in phase I were described well by the conventional URIF model.

Transport de matériaux solides en conduites

This paper presents an experimental research about flows of water-glass beads mixtures in horizontal and vertical pipes. The influence of particles physical parameters (size, granulometry, shape) on pressure losses, velocity profiles, spacial distribution of the solids and flow regime appearance is studied. We developed non intrusive measuring techniques, like ultrasonic and laser velocimetry, light absorption to get to certain parameters (spacial concentration distribution, particle and fluid local velocities). The results are analysed with the idea of a modelisation of solid-liquid mixture flows.

Freezing of saturated and superheated liquid in porous media

Freezing of saturated and superheated liquid-porous media contained in a rectangular test cell has been studied experimentally. Water and different diameter glass beads constituted the liquid and porous media, respectively. The effects of different size glass beads, imposed temperature difference and liquid superheat were investigated. A one-dimensional conduction-based model was used to examine the importance of non-equilibrium effects. These effects were found to be unimportant for both water-aluminum balls and water-glass bead systems. For water initially at the freezing temperature, the model predictions agreed well with the experimental temperature and solidification front position data. When the superheat was sufficiently high to induce buoyancy driven convective flow, the local freezing rates varied with vertical location along the cooled wall. For low superheat, due to the density inversion of water, the rate of freezing at the top was higher than at the bottom ; however, for large superheat, the freezing rate near the bottom was higher as in freezing of ordinary liquids.

Solid hold‐up in bubble columns with suspended solid particles under continuous operation

AbstractSolid hold‐up in bubble columns with suspended solid particles was studied experimentally under continuous slurry feed for the system, air–water–glass beads, in two columns of 55 mm and 95 mm in diameter. Experimental results agree well with the prediction made on the basis of the one‐dimensional dispersion model.

Decorative nickel-chromium electroplated surfaces with patterned finishes

SummaryDecorative nickel-chromium plated surfaces with patterned finishes can be produced using a process which selectively applies the patterning, in the form of a satin texture, to the chromium plated surface by peening with a slurry of glass beads in water. The equipment and techniques needed to ensure successful results in production are described. The results of accelerated corrosion testing and outdoor exposure tests show that the process has no adverse effect on the corrosion resistance of the plated finish. Metallographic examination of the chromium plated surface, after peening, shows the deformation and change in topography, which gives a more diffuse scattering of reflected light, resulting in a lustrous, satin finish. The deformation also introduces a fine crack pattern into the chromium plated layer.

Interaction between particles in a nonwetting liquid

The energy analysis of formation and stability of a cavity in a liquid around the zone of contact between lyophobic particles has been carried out and the parameters of the cavity have been calculated. The receding of the liquid is thermodynamically advantageous for contacting particles as well as for those separated by a gap H not wider than a certain value H e . In the former case the formation of the cavity is a nonactivation process, while in the latter instance it involves the overcoming of a certain activation barrier whose height (∼ H 2) reaches 10 kT at H ≈ 0.3 nm (hydrophobized glass beads in water). As the particles are being separated, the cavity remains metastable in a certain range of gap widths ( H > H e ). The diameter of the cavity and H e are much greater than the molecular sizes; the formation of the cavity gives rise to a sharp increase in the free energy of interaction between the particles, provides for their attraction at considerably greater distances than the molecular forces, and enhances the force of adhesion as against that in air.

Heat transfer in three-phase fluidized beds

Heat transfer coefficients h have been measured in two-phase (water—air, water—glass beads) and three-phase (water—air—glass beads) fluidized beds. Experiments were performed over a wide range of liquid and gas flowrates in a 0.24 m diam. column fitted with an axially mounted cylindrical heater. Four solids were employed ranging in size from 0.5 to 5 mm. Typical maximum values of h in the three-phase, liquid—gas, liquid—solid and liquid beds were approximately 4800, 4300, 3800 and 1300 W/m 2K respectively. In the three-phase beds h generally increased with liquid and gas velocity and with particle size. Correlations are presented to calculate h in the different beds.

Effects of density inversion on free convective heat transfer in porous layer heated from below

A study was conducted to investigate the effects of density inversion on free convective heat transfer in a porous layer heated from below. Glass beads in water composed the porous medium. For upper boundary at 4 and 8°C, thus eliminating the effect of density inversion on the onset of convection, the critical Rayleigh number was found to be 4π 2. The effect of density inversion was evaluated by maintaining the upper boundary temperature at 0°C. The onset of convection was found to be dependent on two thermal parameters which are functions of the boundary temperatures and the coefficients representing the fluid density-temperature relation. The Nusselt number can be represented in terms of a modified Rayleigh number. The effect of density inversion on heat-transfer rate was found to be significant and to decrease as the temperature difference across the layer increases. For small AT, the effect of density inversion causes heat-transfer rate to be as much as 100 per cent less than under non-density inversion conditions.

Reflectance and Transmittance of Light by Leaves

Spectrophotometric transmittance and reflectance curves were recorded for wavelengths from 0.45 (in some cases 0.34) to 2.7 micrometers for faces and backs of leaves and for stacked leaves of several plant species. Measurements were made at different angles of illumination. Leaf spectrophotometric curves were compared with curves for leaf extracts, potato tuber tissue, glass beads in water, and frozen leaves to demonstrate the physical bases for the leaf curves. Leaves were infiltrated with liquids of different refractive indices for further comparison of spectrophotometric curves. Goniophotometric reflectance curves were recorded, giving visible reflectance and degree of polarization as functions of viewing angle for two different angles of illumination.No retroreflection was observed, and no phenomena were observed which could be attributed to interference because of similarity between leaf structural sizes and wavelengths used.

The Fission Gas Problem for Mobile Fuel Fast Reactors

The problems that might result from the release of fission gases in mobile fuel fast reactors are considered for two types of mobile fuel systems; namely, a molten alloy fuel system of the type to be used in the Los Alamos Molten Plutonium Reactor Experiment and a paste fuel system of the type being developad by the Atomic Power Development Associates, Inc. It is shown that the volume of fission gases generated in fast reactors operating at high-power density would supersaturate such fuel systems in minutes or less. An examination of the physical conditions in the reactor core and as evaluation of the phenomena responsible for bubble formation result in the conclusions that neither fuel system will sustain a significant degree of supersaturation and that bubble formation will most likely occur at a solid-liquid interface rather than in the bulk of the liquid. The effects of bubble formation in each system are considered, and these are seen to involve partial blanketing of the beat transfer surfaces, overheating of the fuel, particularly of the paste fuel, equilibrium dilution of the fuel with significant loss in reactivity, sudden displacement of the fuel with subsequent rapid changes in reactivity, and blocking of narrowmore » fuel ligaments and orifices. Preliminary experiments, using supersaturated solutions of carbon dioxiQ in water and in water-glass bead beds are reportad, which verify some of the analyses which are made regarding the location of bubble formation and the growth of bubbles. The flow characteristics of pastes in tubes and the behavior of gas bubbles in such flow systems are discuseed in the light of experiments which were conducted using a simulant system of air/glass beads/water. (auth)« less