Computations of Particle-Laden Turbulent Jet Flows Based on Eulerian Model

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
Pandaba Patro ◽  
Sukanta K. Dash
Keyword(s):  
Gas Flow ◽  
Fine Particles ◽  
Solid Phase ◽  
Fluid Model ◽  
Particle Diameter ◽  
Velocity Profiles ◽  
Solid Particles ◽  
Jet Flows ◽  
Particle Sizes ◽  
Turbulent Characteristics

Numerical simulations using an Eulerian two-fluid model were performed for spatially developing, two-dimensional, axisymmetric jets issued from a 30-mm-diameter circular nozzle. The nozzle was simulated separately for various flow conditions to get fully developed velocity profiles at its exit. The effect of interparticle collisions in the nozzle gives rise to solids pressure and viscosity, which are modeled using kinetic theory of granular flows (KTGF). The particle sizes are in the range of 30 μm to 2 mm, and the particle loading is varied from 1 to 5. The fully developed velocity profiles are expressed by power law, U=Uc(1-(r/R))N. The exponent, N, is found to be 0.14 for gas phase, irrespective of particle sizes and particulate loadings. However, the solid-phase velocity varies significantly with the particle diameter. For particle sizes up to 200 μm, the exponent is 0.12. The center line velocity (Uc) of the solid phase decreases and, hence, the slip velocity increases as the particle size increases. For 1 mm and 2 mm size particles, the exponent is found to be 0.08 and 0.05, respectively. The developed velocity profiles of both the phases are used as the inlet velocities for the jet simulation. The modulations on the flow structures and turbulent characteristics of gas flow due to the solid particles with different particle sizes and loadings are investigated. The jet spreading and the decay of the centerline mean velocity are computed for all particle sizes and loadings considered under the present study. Additions of solid particles to the gas flow significantly modulate the gas turbulence in the nozzle as well as the jet flows. Fine particles suppress the turbulence, whereas coarse particles enhance it.

Numerical Study of Conduction and Convection Between Immersed Object and Gas Fluidized Bed

Volume 1 ◽  
2004 ◽  
Author(s):  
W. M. Gao ◽  
L. X. Kong ◽  
P. D. Hodgson ◽  
B. Wang
Keyword(s):  
Heat Transfer ◽  
Gas Flow ◽  
Solid Phase ◽  
Numerical Study ◽  
Particle Diameter ◽  
Conductive Heat ◽  
Gas Temperature ◽  
Transfer Coefficients ◽  
Immersed Surfaces ◽  
Particle Layer

To analyze the heat transfer mechanism between fluidised beds and surfaces of an immersed object, the heat transfer and gas flow was numerically simulated for different particle systems based on a double particle-layer and porous medium model. It is fund that the conductive heat transfer occurs in the stifling regions between particle and the immersed surface, which have different temperature. The diameter of the circular conduction region, dc, is a function of particle diameter, dp, and can be given by dc/dp = 0.245dp−0.3. In other areas, the heat transfer between the dense gas-solid phase and the immersed object surface is dominated by convection from the moving gas in the tunnel formed by the first-layer particles and the immersed surfaces. The average dimensionless gas velocity, εmfU/Umf, in the tunnel is a constant of about 4.6. The virtual gas temperature at the free stream conditions can be given by the surface temperature of the first-layer particles. The heat transfer coefficient on the conductive region is about 6∼10 times of that on the convection region. The Nusselt numbers for calculating the instantaneous conductive and convective heat-transfer coefficients were theoretically analysed respectively.

Three-dimensional computational fluid dynamics investigation of hydrodynamics behaviour of gas–solid flow in fluidized bed of Geldart D particles

2021 ◽  
pp. 095440892098769
Author(s):  
Fazia Aiche ◽  
Salah Belaadi ◽  
Adel Lalaoua ◽  
Abdallah Sofiane Berrouk ◽  
Abdelwahid Azzi
Keyword(s):  
Fluidized Bed ◽  
Gas Flow ◽  
Turbulence Modeling ◽  
Volume Fraction ◽  
Solid Phase ◽  
Fluid Model ◽  
Flow Behavior ◽  
Three Dimensional ◽  
Industrial Processes ◽  
Cyclic Process

Fluidized beds are widely used in many industrial processes as they ensure the desirable high-intensity heat and mass transfers between gas and particles and offer the possibility to perform operations in a continuous mode and powders recycling. Some of these industrial processes use Geldart D type of powders and operate in the slugging mode. This paper presents a 3 D numerical model of gas-solid flows in a fluidized bed based on the Two-Fluid Model (TFM). Turbulence modeling (k- ε) was used to predict flow behavior in fluidized bed of Geldart D particles. The solid phase consists of Geldart D powders and the gas flow is in a slug regime. The numerical results are validated against the experimental work of Azzi et al. Model predictions on flow patterns, bed expansion, volume fraction time series and pressure drop fluctuations are presented and discussed in details in order to demonstrate the cyclic process of slug formation (onset, growth, rising and bursting of slugs) and its effects on the overall performance of beds fluidizing Geldart D type of powders.

scholarly journals Modeling of multiphase flow at solid particles hydropelling

2019 ◽  
pp. 67-71
Author(s):  
A.Yu. Dreus ◽  
A.V. Haminich ◽  
N.V. Koval ◽  
S.V. Dziuba
Keyword(s):  
Multiphase Flow ◽  
Gas Flow ◽  
Solid Phase ◽  
Flow Simulation ◽  
Solid Particles ◽  
Hydraulic Lift ◽  
Algebraic Equations ◽  
Flow Parameters ◽  
Three Phase ◽  
Nonlinear Algebraic Equations

Purpose. Development of methods for calculating the parameters of the solid particles lifting from the bottom of reservoirs based on the three-phase (gas-liquid-solid particles) flow simulation in an air-lift pipe. Methodology. Mathematical modeling of multiphase flows based on hydraulic ratios. In doing so, heights of up to 10 m (short airlift) are considered with corresponding physical assumptions. Findings. A methodological support has been developed for calculating rational parameters of modes of transporting solid particles with a short airlift. The solution of the problem of the solid particles hydraulic lift by a short airlift is reduced to solving a system of nonlinear algebraic equations. Parametric calculations were carried out and the dependences of the gas flow rate required to ensure a given airlift performance were determined, and the influence of the geometric characteristics of the pipelines on the flow of the solid phase was estimated. Originality. The proposed method allows one to determine the parameters of the solid particles hydraulic lift in a short airlift by solving a system of nonlinear algebraic equations, without using the apparatus of mathematical physics methods. Practical value. It consists in the development of a method for calculating and determining rational parameters of pulp transportation processes in short airlifts. These methods make it possible to determine the dependence of the air flow on the solid particles flow and substantiate the corresponding geometric and flow parameters of the hydraulic lift system. Key words: short airlift, multiphase flow, solid particles hydraulic lift, technological calculatio.

scholarly journals DPM Simulations of A-Type FCC Particles’ Fast Fluidization by Use of Structure-Dependent Nonlinear Drag Force

Processes ◽  
2021 ◽  
Vol 9 (9) ◽  
pp. 1574
Author(s):  
Guorong Wu ◽  
Yanggui Li
Keyword(s):  
Drag Force ◽  
Fine Particles ◽  
Fluid Model ◽  
Particle Diameter ◽  
Flow Structures ◽  
Time Step ◽  
Obvious Effect ◽  
Space Resolution ◽  
Drag Model ◽  
Back Mixing

Nonlinear drag force has been a research frontier in complex gas-solid systems. The literature has reported that the commonly-used drag correlations often overestimate drag force and, thus, cause unrealistic homogeneous flow structures in gas-solid fluidized beds of fine particles. For solving this problem, the structure-dependent drag model, derived from energy-minimization multi-scale approach, is used in discrete simulations of fluid catalytic cracking particles in a small riser. The gas phase is dealt with by computational fluid dynamics. Particles are considered as a discrete phase and described by Newton’s second law of motion. Gas-particle phases are coupled according to Newton’s third law of motion. Simulations show that use of structure-dependent drag model results in drag reduction, the effect of which is not so apparent as that in simulations of the two fluid model. The particle clustering tendency, however, is more distinct and leads to more heterogeneous flow structures in riser flow with a much greater amplitude of outlet solid flux fluctuations. Moreover, the behaviors of particle and gas back-mixing can be captured in the present simulations, which was supported by past simulations and experimental data. The simulation time resolution is discussed. The spring constant can be artificially brought down for safe setting of larger time step when modelling the collision process between fine particles with a higher calculation load. To appropriately mimic the continuous decay of van der Waals force may, however, need a much smaller time step. There is also an obvious effect of space resolution on simulations. When using a grid size smaller than 3 times the particle diameter, the simulated clusters turn extraordinarily large, and the effect of gas-solid back-mixing turns insignificant.

scholarly journals Separation of Fine Particles from Gas in Paint-Spraying Booths

2021 ◽  
Vol 346 ◽  
pp. 03070
Author(s):  
Rustem Ya. Bikkulov ◽  
Andrey V. Dmitriev ◽  
Vadim E. Zinurov ◽  
Guzel R. Badretdinova
Keyword(s):  
Gas Flow ◽  
Fine Particles ◽  
Solid Particles ◽  
Dust Particles ◽  
Technological Parameters ◽  
Separation Device ◽  
Dispersed Particles ◽  
Quality Of Products ◽  
The Impact

Nowadays, at production facilities with paint-spraying booths that use paint and varnish materials to cover the surfaces of product, the problem of gas flow contamination with finely dispersed solid particles of dust and rubbish, which negatively affect the quality of products, is increasingly being raised. In order to minimize the content of solid particles in the gas flow, coarse and fine filters are installed in the paint-spraying booths, which prevent dust particles from entering the surface of products. However, the existing purification devices have a number of disadvantages that affect the efficiency of collecting finely dispersed particles from the gas flow with a size of 0.5-5 microns. The authors of article developed a square separator to increase the efficiency of collecting finely dispersed particles from gas flows in the paint-spraying booths. The installation of proposed separation device in the paint-spraying booths affects not only the quality of collecting solid particles, but also increases the service life of fine and coarse filters In the course of numerical studies, the results of impact of structural and technological parameters, namely, the impact of inlet rate and scale of separation device on the efficiency of collecting solid particles from the gas flow, were obtained.

Experimental Study of Bubble Behavior in a Two-Dimensional Particle Bed With High Solid Holdup

2010 ◽  
Author(s):  
Songbai Cheng ◽  
Daisuke Hirahara ◽  
Youhei Tanaka ◽  
Yoji Gondai ◽  
Tatsuya Matsumoto ◽  
...  
Keyword(s):  
Liquid Phase ◽  
Gas Flow ◽  
Solid Phase ◽  
Particle Diameter ◽  
Heat Removal ◽  
Bubble Behavior ◽  
Nitrogen Gas ◽  
Bubble Rise ◽  
Solid Holdup ◽  
Particle Bed

In a core disruptive accident of a fast breeder reactor, the post accident heat removal is crucial to achieve in-vessel core retention. Therefore, a series of experiments on bubble behavior in a particle bed was performed to clarify three-phase flow dynamics in debris bed, which is essential in heat-removal capability, under coolant boiling conditions. Although in the past several experiments have been carried out in the gas-liquid-solid system to investigate the bubble dynamics, most of them were under lower solid holdup (≤ 0.5), where the solid-phase influence may be not so important as much as the liquid phase. While for this study, the solid holdup is much higher (> 0.55) where the particle-bubble interaction may be dominated. The current experiment was conducted in a 2D tank with the dimensions of 300 mm height, 200 mm width and 10 mm gap thickness. Water was used as liquid phase, while bubbles were generated by injecting nitrogen gas from the bottom of the tank. Various experimental parameters were taken, including different particle bed height (from 30 mm to 200 mm), various particle diameter (from 0.4 mm to 6 mm), different particle type (acrylic, glass, alumina and zirconia beads), and different nitrogen gas flow rate (around 1.75 ml/min and 2.7 ml/min). By using digital image analysis method, three kinds of bubble rise behavior were observed under current experimental conditions and confirmed by the quantitative detailed analysis of bubble rise properties including bubble departure frequency and bubble departure size. This experiment is expected in the future to provide appropriate quantitative data for the analysis and verification of SIMMER-III, an advanced fast reactor safety analysis code.

The influence of the Stokes and Archimedes forces on the stability of a two-phase flow

2003 ◽  
Vol 3 ◽  
pp. 266-270
Author(s):  
B.H. Khudjuyerov ◽  
I.A. Chuliev
Keyword(s):  
Spectral Method ◽  
Stability Region ◽  
Gas Flow ◽  
Two Phase Flow ◽  
Solid Phase ◽  
Stability Characteristic ◽  
Phase Flow ◽  
Two Phase ◽  
The Stability

The problem of the stability of a two-phase flow is considered. The solution of the stability equations is performed by the spectral method using polynomials of Chebyshev. A decrease in the stability region gas flow with the addition of particles of the solid phase. The analysis influence on the stability characteristic of Stokes and Archimedes forces.

Modeling of pressure losses on friction in three-layer laminar flows

2003 ◽  
Vol 3 ◽  
pp. 208-219
Author(s):  
A.M. Ilyasov
Keyword(s):  
Pressure Loss ◽  
Gas Flow ◽  
Mutual Influence ◽  
Fluid Model ◽  
Immiscible Liquid ◽  
Laminar Flows ◽  
Pressure Losses ◽  
Flow Parameters ◽  
Interphase Boundaries ◽  
Closing Relations

In this paper we propose a model for determining the pressure loss due to friction in each phase in a three-layer laminar steady flow of immiscible liquid and gas flow in a flat channel. This model generalizes an analogous problem for a two-layer laminar flow, proposed earlier. The relations obtained in the final form for the pressure loss due to friction in liquids can be used as closing relations for the three-fluid model. These equations take into account the influence of interphase boundaries and are an alternative to the approach used in foreign literature. In this approach, the wall and interphase voltages are approximated by the formulas for a single-phase flow and do not take into account the mutual influence of liquids on the loss of pressure on friction in phases. The distribution of flow parameters in these two models is compared.

scholarly journals Experimental Analysis of the Mechanical Properties and Resistivity of Tectonic Coal Samples with Different Particle Sizes

Energies ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2303
Author(s):  
Congyu Zhong ◽  
Liwen Cao ◽  
Jishi Geng ◽  
Zhihao Jiang ◽  
Shuai Zhang
Keyword(s):  
Mechanical Properties ◽  
Particle Size ◽  
Compressive Strength ◽  
Elastic Modulus ◽  
Uniaxial Compressive Strength ◽  
Coalbed Methane ◽  
Coal Sample ◽  
Fine Particles ◽  
Particle Sizes ◽  
Tectonic Coal

Because of its weak cementation and abundant pores and cracks, it is difficult to obtain suitable samples of tectonic coal to test its mechanical properties. Therefore, the research and development of coalbed methane drilling and mining technology are restricted. In this study, tectonic coal samples are remodeled with different particle sizes to test the mechanical parameters and loading resistivity. The research results show that the particle size and gradation of tectonic coal significantly impact its uniaxial compressive strength and elastic modulus and affect changes in resistivity. As the converted particle size increases, the uniaxial compressive strength and elastic modulus decrease first and then tend to remain unchanged. The strength of the single-particle gradation coal sample decreases from 0.867 to 0.433 MPa and the elastic modulus decreases from 59.28 to 41.63 MPa with increasing particle size. The change in resistivity of the coal sample increases with increasing particle size, and the degree of resistivity variation decreases during the coal sample failure stage. In composite-particle gradation, the proportion of fine particles in the tectonic coal sample increases from 33% to 80%. Its strength and elastic modulus increase from 0.996 to 1.31 MPa and 83.96 to 125.4 MPa, respectively, and the resistivity change degree decreases. The proportion of medium particles or coarse particles increases, and the sample strength, elastic modulus, and resistivity changes all decrease.

Two-Phase Flows in Mini-/Micro-Gas Flow Channels of PEM Fuel Cells

2013 ◽  
Author(s):  
Sung Chan Cho ◽  
Yun Wang
Keyword(s):  
Pressure Drop ◽  
Gas Flow ◽  
Fluid Model ◽  
Pem Fuel Cells ◽  
Two Phase ◽  
Micro Gas Flow ◽  
Two Fluid Model ◽  
The Impact ◽  
Two Fluid ◽  
Phase Pressure

In this paper, two-phase flow dynamics in a micro channel with various wall conditions are both experimentally and theoretically investigated. Annulus, wavy and slug flow patterns are observed and location of liquid phase on different wall condition is visualized. The impact of flow structure on two-phase pressure drop is explained. Two-phase pressure drop is compared to a two-fluid model with relative permeability correlation. Optimization of correlation is conducted for each experimental case and theoretical solution for the flows in a circular channel is developed for annulus flow pattern showing a good match with experimental data in homogeneous channel case.

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