Influence Of Particle Concentration Research Articles

A computational investigation of transient heat transfer in pneumatic transport of granular particles

The Distinct Element Method (DEM) has been employed to model a range of gas–solids flow systems such as solids flow in hoppers, gas–solids pipe flow and particulate fluidized bed. But little has been reported on the application of this technique to heat transfer in gas–solids flows. This paper describes a numerical model for gas–solids two-phase flow with heat transfer in pneumatic transport pipes. The gas phase is modelled as a continuum and the solids phase is modelled by DEM. Convective heat transfer between gas and particles and between gas and pipe wall, and conductive heat transfer between particles and between particles and pipe wall are modelled. The influence of particle concentration on the predicted performance of the system has been compared with experimental data. This comparison has shown a good agreement between the DEM simulation and experiment for both pressure drop and pipe wall temperature profile at developed flow region.

Properties of polyelectrolyte-modified clays: Influence of the particle concentration on the degree of modification

Adsorption of polycation as well as the modification with oppositely charged polyelectrolytes is a useful tool for surface modification. As shown previously, a strong enhancement of the attainable specific cationic surface charge was observed, e.g., with poly(diallyl-dimethylammonium chloride) (PDADMAC) as the polycation and poly(maleic acid-co-α-methylstyrene) (P(MS-α-MeSty) as the polyanion, at a ratio of anionic to cationic charges of n−/n+ = 0.6 … 0.7. However, because the surface charge seemed to be strongly affected by the conditions of modification, the influence of particle concentration was investigated in detail. One gram of clay was suspended in different volumes of water so that the particle concentration was varied from 1 to 100 g/L. These suspensions were treated under the same conditions. For characterizing the surface charge of clay polyelectrolyte titration, dye adsorption, or microelectrophoresis was used. The comparison between the results of polyelectrolyte titration and the carbon content in the residual solution allowed prediction of the existence of a polyelectrolyte complex and calculation of the stoichiometry. It was found for a constant concentration of PDADMAC per 1 g of clay that the surface charge of modified clays changed from negative (1 g/L) to strong positive, depending on the particle concentration. The cause was assumed to be the differences in the probability of interaction of particles, combined with the changes in the stoichiometry of the polyelectrolyte complex built in the solution, whereas the effect of other factors (conductivity, time of adsorption) was rather low. A strong cationic surface modification was obtained for medium and high particle concentrations only. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 16–25, 2000

The influence of particle concentration in ferrofluids on broadening of the magnetic resonance line

The increase of the magnetic resonance linewidth (ΔH) with concentration of the magnetic particles for two ferrofluids, one with Fe3O4 and the other with Mn0.6Fe0.4Fe2O4 particles is discussed. We found that this dependence is in good agreement with the formula established by Morais (Philos. Mag. Lett. 55 (1987) 181), even at low particle concentrations, if a correction is made. It is also shown that the linewidth, ΔH is the same for the ferrofluids having particles of different nature, at the same concentration, if the ferrofluids have the same mean magnetic moment of a particle.

Rheological Aspects of Thixotropy in Synthetic Alumino-Silicate Hydrosol during Electrolytic Interaction

Though thixotropy is a case of partial coagulation, it is a specific phenomenon and not observed in all kinds of colloidal sols. Alumino-silicate hydrosols, because of their high sensitivity towards addition of electrolytes and high molecular weight, exhibit this property. The relative influence of particle concentration and electrolytes on the rate of thisxotropic growth can be rheologically characterized by the hysteresis loop in the double consistency curves.

Influence of particle concentration on rheological properties of aqueous α-Al 2O 3 suspensions

The influence of particle concentration on the rheological properties of aqueous alumina suspensions is investigated under steady and oscillatory shear conditions. At solid volume fractions between 0·45 and 0·6, a high degree of particle stabilization is achieved when 0·2 wt% of polyacrylic acid is added as a dispersant. With increasing particle concentration the flow behavior changes from pseudoplastic to plastic. The apparent yield stress (from the generalized Casson model) is found to be a significant quantity for characterizing changes in structural conditions of the disperse phase with increasing solids loading even though more detailed information is provided by viscoelastic properties. The analysis of viscoelastic data based on the Friedrich–Braun fractional derivative model and the generalized Maxwell model showed that transitions of particle arrangements due to electrostatic repulsion take place at Φ=0·5 and 0·55. For these critical concentrations the influence of latex binder addition on the rheological properties is examined.

A unified approach from elasticity to viscoelasticity to viscoplasticity of particle-reinforced solids

Abstract This paper presents a novel approach to determine the overall elastic-viscoplastic behavior of a particle-reinforced metal-matrix composite. It is built upon the linkage from elasticity to viscoelasticity through the correspondence principle, and then from viscoelasticity to viscoplasticity by means of the concept of secant viscosity and an energy approach. Albeit approximate, this theory is analytically tractable, and capable of delivering the stress-strain relations of the composite sittem under various applied strain rates. The theory embodies the nonlinear, rate-dependent, and work-hardening nature of the constitutive equations of the ductile matrix, as well as the elasticity of both matrix and inclusions. The influence of particle concentration, elastic stiffness, and applied strain rate on the overall dilatational and deviatoric stress-strain behaviors are examined in detail. The theory is finally applied to predict the response of a silicon-carbide/aluminum system and the result is found to be in accord with experimental observations.

Electric light scattering by suspensions of anisotropic, slightly anisodiametric latex particles

Abstract The electric light scattering effect has been measured in aqueous suspensions of almost monodisperse, slightly elongated polytetrafluorethylene particles, and the influence of particle concentration and ionic strength investigated. The absence of dependence of the electric light scattering on particle concentration in the range 0.022–1.1% (w/w) at constant ionic strength is considered as evidence that there are no collective effects in these suspensions. The decrease of the kilohertz (KHz) effect with increase of ionic strength (from 5 × 10 −5 to 5 × 10 −3 M NaCl) and displacement of its relaxation frequency towards higher frequencies confirmed the concept for the interfacial origin of the electro-optic effect in dilute suspensions.

Acoustic agglomeration of a glycol fog aerosol: Influence of particle concentration and intensity of the sound field at two frequencies

Measurements of the initial acoustic agglomeration rate averaged over the volume of the measurement chamber, K c 0 , as a function of the applied acoustic power, P, and of the initial aerosol particle concentration, N T 0, have been made using sound sources operating at 10 and 21 kHz. The results show that at both frequencies the acoustic agglomeration rate is directly proportional to the square of the wave velocity amplitude, i.e. K c 0 ≡ U w 2 . A model that takes account of sound attenuation in progressive or standing wave situations has been devised. The results of this model are consistent with the experimental observations when the efficiency dependency of K c 0 on U w 2 is incorporated. It is also shown that an enhanced agglomeration can be achieved under standing wave conditions. The model also yields a number of non-dimensional parameters which permit comparison of measurements made in chambers with different geometry.

Mathematical Model of Dust Retention in the Human Respiratory System

A mathematical model of retention of insoluble aerosol particles penetrating the lungs during inhalation has been described. Based on data of the streams of deposited particles and their residence times in the subsequent generations of the respiratory system - due to different mechanisms of clearance - the retention dynamics of particles has been determined. The influence of particle concentration and particle toxicity on retention is considered.

Oceanic trace metal scavenging: the importance of particle concentration

Adsorption (surface complexation) has long been considered to be the dominant process involved in the oceanic scavenging of many trace metals. Much of what we know about metal removal in the ocean (i.e. rate and extent) is based on measurements of U and Th decay series isotopes. However, the scavenging equations developed from radioactive parent-daughter relationships presume no specific metal removal process and cannot be directly used to verify a particular one.In this paper we examine and compare the phenomenological model of adsorption and oceanic scavenging observations. The formalisms of surface coordination and colloid chemistry are linked to the mechanism-free observations of oceanic trace metal scavenging by the strong similarities in the description of the reaction rates and the influence of particle concentration on those rates and the equilibrium distributions. The correspondence between laboratory sorption data and field scavenging observations as well as the consistency of the hypothesis over a wide range of environmental systems successfully link oceanic trace metal scavenging with surface coordination and colloid aggregation reactions. The merging of descriptions of surface and colloid chemistry and field observations of scavenging provide a framework for interpreting field data and understanding how master variables (e.g. reaction rate, particle concentration, or particle flux) influence metal removal from the oceans.

Influence of particle concentration on the angular structure of scattered radiation

Influence of particle concentration on the angular structure of scattered radiation

On the effective viscosity of pseudoplastic suspensions

An expression is developed that predicts the concentration dependence of the apparent viscosity of a concentrated pseudoplastic suspension. The result, which is an extension of the Frankel and Acrivos Newtonian suspension analysis, shows that the influence of particles concentration on the effective viscosity of pseudoplastic suspensions increases as the power law index of the suspension increases. Experimental data shows good agreement with the theoretical predictions.