Abstract: In this paper, the flow of fly ash in fluidized dense phase pneumatic conveying through a section of pipeline having uniform pipe diameter has been modeled and analyzed using Computational Fluid Dy...

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Topics: Fly ash (53%)

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5 results found

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Abstract: Bulk materials like sand particle/alumina, which do not possess good air retention properties or high permeability are generally conveyed in the dilute phase, suspension flow in conventional pneumatic conveying systems. High inlet conveying air velocity is thus necessary to successfully convey such materials. As a result of high air velocity, the particles impact on the bend surface and cause erosion of bends and attrition of particles. The study of bend erosion has been a subject of research for a long time and the influence of various operating parameters has been widely investigated. The authors have carried out an extensive experimental plan to study the influence of recirculation of material on the erosion of bends and attrition of particles. It is expected that the severity of erosion may go down as the particles lose sharp edges due to the recirculation of material. Silica sand having a mean particle size of 435 μm was conveyed in the pneumatic conveying pilot plant. The pipeline test loop is 48 m long and 67 mm bore. The bends were placed in horizontal-horizontal orientation with R/d ratio of 4.0. The solid particle erosion behavior of three test bends (B1, B2 and B3) and particle attrition have been analyzed. A 300 kg batch of sand was recirculated 29 times through the test pipeline, thus conveying a total of 8.7 tonnes. The mass loss and bend wall thickness were regularly monitored. Material sample during each run was collected to assess the extent of particle attrition and changes in the particle morphology. This paper presents the experimental results of a comprehensive analysis of the erosion and particle degradation with a change in particle morphology. A correlation has been developed between the extent of material recirculated through the test pipeline and its influence on the erosion of bends and degradation of particles.

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Topics: Particle (56%), Particle size (54%)

2 Citations

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28 Jun 2021-

Abstract: In this paper, a mathematical model for the pneumatic transport of micron silica particles in the dust removal pipeline is established, and the gas-solid two-phase flow in the pipeline is numerically simulated. This paper is mainly based on the FLUENT fluid simulation module in ANSYS WORKBENCH to simulate the motion behavior of particles in the pipeline, and obtained the penetration rate (particle deposition rate in pneumatic conveying) of silica particles in the horizontal straight pipe under different gas flow rates. In the numerical simulation, the influence of particle diameter, shape, lift and other factors on silica particles was considered. Under a large number of simulation conditions, the movement laws of micron silica particles in horizontal pipe pneumatic transport were obtained, and the influence of the above factors on the movement laws of the particles were determined.

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Topics: Particle deposition (56%)

1 Citations

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Abstract: This paper studies the ability of the ANN to predict the pneumatic conveying performance of powders. At high air velocity, the flow is dilute. But at low air velocities it is fluidized dense. Fluidized dense flow involves several complex interactions among gas, particle and wall. But in dilute flow, the particle-particle interaction is less. Implementation of these interactions in a model is difficult. Experimental data available for pneumatic conveying were used to train the network and then predict the pressure drop. Three different training methods Levenberg Marquardt, Bayesian Regularization and Scaled Conjugate Gradient are used. The BR method takes more time for analysis, but it gives better results than others when sample size is small and noisy. For larger sample size the LM method gives better results than the other two methods. The model is also predicts the pressure drop within ±10% error margin under length scale-up conditions.

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Topics: Pressure drop (56%), Levenberg–Marquardt algorithm (52%), Conjugate gradient method (51%)

1 Citations

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Abstract: The purpose of this paper is to focus on predicting the pressure drop in fluidized dense phase pneumatic conveying of fine particles through pipelines by modelling the solids friction factor in terms of non-dimensional parameters using experimental data of definite pipeline configuration. Finally, the model is to be tested for a different pipeline configuration.,Solids friction factor has been expressed in terms of certain non-dimensional parameters such as density ratio, solids loading ratio and mean particle diameter to pipe diameter ratio, and a certain number of coefficients and exponents. Experimental data of five conveying materials (two types of fly ash, two types of alumina and one type of cement meal) for a pipeline configuration of diameter 53 mm and length 173 m and another conveying material EPS dust for two pipeline configurations (69-mm diameter, 168-m long; 105-mm diameter, 168-m long) have been used to calculate the unknown coefficients or exponents of the mathematical model for solids friction factor.,The developed model gives the best results in predicting the pressure drop for the pipelines that are less than 173-m long, but the model shows a large error for the pipelines more than 173-m long.,Current research will be helpful for the researchers to model the process of pneumatic conveying through long distances.,The method will be helpful in conveying powder materials through long distances in cement or brick industry, alumina industry.,Fly ash piles over at the nearby places of thermal power plants. Pneumatic conveying is the best method for transporting the fly ash from the location of power plants to the nearby brick industries or cement industries.,Solid friction factor has been presented in terms of four non-dimensional parameters and evaluated the accuracy in predicting the pressure drop for two different pipeline configurations.

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Topics: Pressure drop (53%), Pipeline transport (52%)

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30 results found

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01 Jan 1952-

Topics: Kozeny–Carman equation (64%), Fluid dynamics (58%), CFD-DEM (53%)

6,190 Citations

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Abstract: The flow of an idealized granular material consisting of uniform smooth, but nelastic, spherical particles is studied using statistical methods analogous to those used in the kinetic theory of gases. Two theories are developed: one for the Couette flow of particles having arbitrary coefficients of restitution (inelastic particles) and a second for the general flow of particles with coefficients of restitution near 1 (slightly inelastic particles). The study of inelastic particles in Couette flow follows the method of Savage & Jeffrey (1981) and uses an ad hoc distribution function to describe the collisions between particles. The results of this first analysis are compared with other theories of granular flow, with the Chapman-Enskog dense-gas theory, and with experiments. The theory agrees moderately well with experimental data and it is found that the asymptotic analysis of Jenkins & Savage (1983), which was developed for slightly inelastic particles, surprisingly gives results similar to the first theory even for highly inelastic particles. Therefore the ‘nearly elastic’ approximation is pursued as a second theory using an approach that is closer to the established methods of Chapman-Enskog gas theory. The new approach which determines the collisional distribution functions by a rational approximation scheme, is applicable to general flowfields, not just simple shear. It incorporates kinetic as well as collisional contributions to the constitutive equations for stress and energy flux and is thus appropriate for dilute as well as dense concentrations of solids. When the collisional contributions are dominant, it predicts stresses similar to the first analysis for the simple shear case.

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Topics: Couette flow (58%), Taylor–Couette flow (57%), Granular material (55%) ... show more

2,361 Citations

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Abstract: In this paper, equations governing the time dependent flow of granular material under gravity are derived and analyzed. Formally these equations bear a strong resemblance to the Navier-Stokes equations for the flow of an incompressible, viscous fluid. However, the main result of this paper is that, depending on geometric and material parameters, the equations governing granular flow may lead to a violent instability analogous to that for u, = u XI up ;

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Topics: Flow (mathematics) (57%), Granular material (53%)

934 Citations

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Abstract: The Percus-Yevick approximate equation for the radial distribution function of a fluid is generalized to an $m$-component mixture. This approximation which can be formulated by the method of functional Taylor expansion, consists in setting $\mathrm{exp}[\ensuremath{-}\ensuremath{\beta}{\ensuremath{\phi}}_{\mathrm{ij}}(r)]{C}_{\mathrm{ij}}(r)$ equal to ${g}_{\mathrm{ij}}(r)[{e}^{\ensuremath{-}\ensuremath{\beta}{\ensuremath{\phi}}_{\mathrm{ij}}(r)}\ensuremath{-}1]$, where ${C}_{\mathrm{ij}}$, ${g}_{\mathrm{ij}}$, and ${\ensuremath{\phi}}_{\mathrm{ij}}$ are the direct correlation function, the radial distribution function and the binary potential between a molecule of species $i$ and $a$ molecule of species $j$. The resulting equation for ${C}_{\mathrm{ij}}$ and ${g}_{\mathrm{ij}}$ is solved exactly for a mixture of hard spheres of diameters ${R}_{i}$. The equation of state obtained from ${C}_{\mathrm{ij}}(r)$ via a generalized Ornstein-Zernike compressibility relation has the form $\frac{p}{\mathrm{kT}}={[\ensuremath{\Sigma}{\ensuremath{\rho}}_{i}][1+\ensuremath{\xi}+{\ensuremath{\xi}}^{2}]\ensuremath{-}\frac{18}{\ensuremath{\pi}}\ensuremath{\Sigma}{ilj}^{}{\ensuremath{\eta}}_{i}{\ensuremath{\eta}}_{j}{({R}_{i}\ensuremath{-}{R}_{j})}^{2}\ifmmode\times\else\texttimes\fi{}[{R}_{i}+{R}_{j}+{R}_{i}{R}_{j}(\ensuremath{\Sigma}{\ensuremath{\eta}}_{l}R_{l}^{}{}_{}{}^{2})]}{(1\ensuremath{-}\ensuremath{\xi})}^{\ensuremath{-}3}$, where ${\ensuremath{\eta}}_{i}=\frac{\ensuremath{\pi}}{6}$ times the density of the $i\mathrm{th}$ component and $\ensuremath{\xi}=\ensuremath{\Sigma}{\ensuremath{\eta}}_{l}R_{l}^{}{}_{}{}^{3}$. This equation yields correctly the virial expansion of the pressure up to and including the third power in the densities and is in very good agreement with the available machine computations for a binary mixture. For a one-component system our solution for $C(r)$ and $g(r)$ reduces to that found previously by Wertheim and Thiele and the equation of state becomes identical with that found on the basis of different approximations by Reiss, Frisch, and Lebowitz.

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Topics: Equation of state (cosmology) (57%)

897 Citations