3D Numerical Simulation and PEPT Experimental Investigation of Pressurized Gas-Solid Fluidized Bed Hydrodynamic

2009 ◽  
Author(s):  
P. Fede ◽  
G. Moula ◽  
A. Ingram ◽  
T. Dumas ◽  
O. Simonin
Keyword(s):  
Numerical Model ◽  
Fluidized Bed ◽  
Particle Velocity ◽  
Particle Trajectory ◽  
Wall Region ◽  
3 Dimensional ◽  
The Core ◽  
Numerical Predictions ◽  
Model Predictions ◽  
Good Agreement

The present paper is dedicated to numerical and experimental study of the hydrodynamic of a non-reactive isothermal pressurized fluidized bed. Experimental data have been obtained using PEPT technique allowing to track a particle trajectory inside a dense fluidized bed. A specific post-processing approach has been developed to compute the Eulerian time-averaged particle velocity field. The comparison with 3-dimensional numerical model predictions shows a good agreement in the core of the fluidized bed. In contrast, in the near wall region the numerical model overestimate the downward particle velocity. The modification of particle phase wall boundary condition improves the numerical predictions.

Comparison of Four Friction Models: Feature Prediction

2015 ◽  
Vol 11 (3) ◽  
Author(s):  
Yun-Hsiang Sun ◽  
Tao Chen ◽  
Christine Qiong Wu ◽  
Cyrus Shafai
Keyword(s):  
Numerical Model ◽  
Viscous Friction ◽  
Friction Model ◽  
Dynamic Features ◽  
Numerical Predictions ◽  
Wide Range ◽  
Model Predictions ◽  
Friction Models ◽  
Parameter Identifications ◽  
Model Structures

In this paper, we provide not only key knowledge for friction model selection among candidate models but also experimental friction features compared with numerical predictions reproduced by the candidate models. A motor-driven one-dimensional sliding block has been designed and fabricated in our lab to carry out a wide range of control tasks for the friction feature demonstrations and the parameter identifications of the candidate models. Besides the well-known static features such as break-away force and viscous friction, our setup experimentally demonstrates subtle dynamic features that characterize the physical behavior. The candidate models coupled with correct parameters experimentally obtained from our setup are taken to simulate the features of interest. The first part of this work briefly introduces the candidate friction models, the friction features of interest, and our experimental approach. The second part of this work is dedicated to the comparisons between the experimental features and the numerical model predictions. The discrepancies between the experimental features and the numerical model predictions help researchers to judge the accuracy of the models. The relation between the candidate model structures and their numerical friction feature predictions is investigated and discussed. A table that summarizes how to select the most optimal friction model among a variety of engineering applications is presented at the end of this paper. Such comprehensive comparisons have not been reported in previous literature.

Different Exit Effects between a Combined Riser with Variable Exit Constraints and a Conventional Riser with Weak Exit Constraints

2012 ◽  
Vol 550-553 ◽  
pp. 529-533
Author(s):  
De Wu Wang ◽  
Meng Da Jia ◽  
Shao Feng Zhang ◽  
Chun Xi Lu
Keyword(s):  
Fluidized Bed ◽  
Particle Velocity ◽  
Large Scale ◽  
Operating Conditions ◽  
Wall Region ◽  
Cold Model ◽  
Linear Distribution ◽  
Cross Sectional ◽  
Bed Height ◽  
Solids Holdup

A large-scale cold model experimental setup of combined riser with variable constraint exit (CRVCE) was established. The axial and radial distributions of solids holdup and particle velocity, under different operating conditions, were investigated experimentally, and the results were compared with conventional riser (CR). Experimental results showed that, the exit restrictive effect of combined riser with variable constraint exit was weak when particle circulation flux and static bed height in upper fluidized bed were lower, while it turned to be strong when superficial gas velocity and static bed height in upper fluidized bed were higher. Under the same conditions, averaged cross-sectional solids holdup of CRVCE was characterized by C type distribution when article circulation flux was higher, while that of CR with weak constraint exit was characterized by linear distribution. In axial direction, averaged cross-sectional particle velocity of CRVCE changed in order: acceleration-constant-decrease velocity, while that of CR changed in another: acceleration-constant velocity. The maximum of local solids holdup value of CRVCE appeared at the dimensionless radius position r/R=0.7, while that of CR appeared in the wall region. Their local particle velocities were similar in the core region, while local particle velocity of CRVCE was lower than that of CR in the annular region.

Detection and Modeling of the Core-Annulus Transition in Industrial and Pilot Plant Risers

2003 ◽  
Vol 1 (1) ◽  
Author(s):  
Lauren Briens ◽  
Cedric Briens ◽  
David Nevicato ◽  
Jean René Bernard
Keyword(s):  
Pilot Plant ◽  
Signal Analysis ◽  
Optical Probe ◽  
Transition Analysis ◽  
The Core ◽  
Model Predictions ◽  
Vertical Pneumatic Transport ◽  
Probe Measurements ◽  
Good Agreement

The core-annulus structure is essential to the modeling and optimization of riser reactors such as used in Fluid Catalytic Cracking. This paper presents results of measurements taken with various probes in a pilot plant and in an industrial riser. The instantaneous probe signals were analyzed with sophisticated signal analysis methods based on the detection of cycles and the determination of the correlation dimension.In a pilot plant riser, a core-annulus structure was identified with optical and momentum probe measurements. Cycle analysis of the optical probe measurements showed that the annulus was unstable: its thickness fluctuated with an average cycle time of 0.3 s. There were waves at the core-annulus boundary. In an industrial riser, a similar core-annulus structure could be identified with temperature and momentum probe measurements. Local temperature measurements are much easier to perform in an industrial riser than momentum probe measurements but can provide, with cycle analysis, the location of the core-annulus transition. Analysis of the momentum probe and temperature signals showed that the thickness of the wavy transition layer between core and annulus was about the same in the pilot plant and the industrial riser, meaning that the relative range of fluctuations in annulus thickness was much smaller in the larger industrial riser.A model was developed to predict the time-averaged transition between core and annulus. This model, which had been successfully used to predict the annulus thickness in dilute-phase vertical pneumatic transport lines, assumes that the annulus thickness is such that the riser pressure drop is minimized. Measurements and model predictions were in good agreement.

Numerical Investigation of Delft-Jet-in-Hot-Coflow (DJHC) Burner Using Probability Density Function (PDF) Transport Modeling

2013 ◽  
Author(s):  
Ashoke De ◽  
Akshay Dongre ◽  
Rakesh Yadav
Keyword(s):  
Reynolds Number ◽  
Molecular Diffusion ◽  
Minimum Spanning Tree ◽  
Transport Modeling ◽  
Low Oxygen ◽  
Energy Profiles ◽  
Numerical Predictions ◽  
Model Predictions ◽  
Solution Methods ◽  
Good Agreement

In the present paper, the flames from DJHC burner, imitating MILD (Moderate and Intense Low Oxygen Dilution) combustion, are simulated using PDF transport modeling. Two different solution approaches have been used to resolve the joint composition PDF. First, a Lagrangian approach is used to solve the joint composition PDF, while in the second approach, the approximate solution is achieved by using presumed shape PDF and DQMOM-IEM modeling known as Multi-Environment Eulerian PDF (MEPDF). A quantitative comparison of the predictions from these two solution methods has been performed for two different jet Reynolds number, i.e. Re = 4100 & 8800. Moreover, the effect of molecular diffusion is also explored by comparing the predictions using different micro-mixing models such as Coalescence Dispersion (CD), Euclidean Minimum Spanning Tree (EMST), and Interaction-by-Exchange-with-Mean (IEM) model. The obtained numerical predictions from both approaches are compared with the experimental data to highlight the accuracy as well as the predictive capability of these models. In the case of low Reynolds number (Re = 4100), it is observed that the mean axial velocity and turbulent kinetic energy profiles are in good agreement with the measurements while the temperature profiles are slightly over-predicted in the downstream region. Although MEPDF results are in good agreement with the LPDF results, both the model predictions tend to exhibit discrepancies at higher Reynolds number.

Heat and mass transfer in wood composite panels during hot pressing: Part 4. Experimental investigation and model validation

Holzforschung ◽  
2007 ◽  
Vol 61 (1) ◽  
pp. 83-88 ◽  
Author(s):  
Chunping Dai ◽  
Changming Yu ◽  
Changyan Xu ◽  
Guangbo He
Keyword(s):  
Mass Transfer ◽  
Experimental Investigation ◽  
Heat And Mass Transfer ◽  
Core Temperature ◽  
Hot Pressing ◽  
Gas Pressure ◽  
Wood Composite ◽  
The Core ◽  
Model Predictions ◽  
Good Agreement

Abstract The effects of panel density and strand size on the temperature and gas pressure inside strand mats during hot pressing has been experimentally investigated. The results show good agreement with model predictions. Strand dimensions have a strong effect on the core temperature and gas pressure when the mat/panel density is relatively high. At lower density, the temperature and gas pressure are controlled only by the panel density. Comparison between the model predictions and experimental results also reveals the need for further characterisation of the basic mat properties, especially conductivity and permeability.

Effect of microgravity and hypergravity on deposition of 0.5- to 3-μm-diameter aerosol in the human lung

1997 ◽  
Vol 83 (6) ◽  
pp. 2029-2036 ◽  
Author(s):  
Chantal Darquenne ◽  
Manuel Paiva ◽  
John B. West ◽  
G. Kim Prisk
Keyword(s):  
Particle Size ◽  
Tidal Volume ◽  
Flow Rate ◽  
Human Lung ◽  
Constant Flow ◽  
Parabolic Flights ◽  
Constant Flow Rate ◽  
Numerical Predictions ◽  
Model Predictions ◽  
Good Agreement

Darquenne, Chantal, Manuel Paiva, John B. West, and G. Kim Prisk. Effect of microgravity and hypergravity on deposition of 0.5- to 3-μm-diameter aerosol in the human lung. J. Appl. Physiol. 83(6): 2029–2036, 1997.—We measured intrapulmonary deposition of 0.5-, 1-, 2-, and 3-μm-diameter particles in four subjects on the ground (1 G) and during parabolic flights both in microgravity (μG) and at ∼1.6 G. Subjects breathed aerosols at a constant flow rate (0.4 l/s) and tidal volume (0.75 liter). At 1 G and ∼1.6 G, deposition increased with increasing particle size. In μG, differences in deposition as a function of particle size were almost abolished. Deposition was a nearly linear function of the G level for 2- and 3-μm-diameter particles, whereas for 0.5- and 1.0-μm-diameter particles, deposition increased less between μG and 1 G than between 1 G and ∼1.6 G. Comparison with numerical predictions showed good agreement for 1-, 2-, and 3-μm-diameter particles at 1 and ∼1.6 G, whereas the model consistently underestimated deposition in μG. The higher deposition observed in μG compared with model predictions might be explained by a larger deposition by diffusion because of a higher alveolar concentration of aerosol in μG and to the nonreversibility of the flow, causing additional mixing of the aerosols.

NUMERICAL MODEL TO SIMULATE THE EROSION ON THE SLOPE DUE TO OVERTOPPING

2010 ◽  
Vol 13 (3) ◽  
pp. 78-87
Author(s):  
Hoai Cong Huynh
Keyword(s):  
Numerical Model ◽  
Flow Model ◽  
Bed Load ◽  
Experiment Data ◽  
Step Method ◽  
Morphological Model ◽  
Load Transport ◽  
Bed Load Transport ◽  
The Finite Difference Method ◽  
Good Agreement

The numerical model is developed consisting of a 1D flow model and the morphological model to simulate the erosion due to the water overtopping. The step method is applied to solve the water surface on the slope and the finite difference method of the modified Lax Scheme is applied for bed change equation. The Meyer-Peter and Muller formulae is used to determine the bed load transport rate. The model is calibrated and verified based on the data in experiment. It is found that the computed results and experiment data are good agreement.

3D Numerical Simulation of Polydisperse Pressurized Gas-Solid Fluidized Bed

2011 ◽  
Author(s):  
P. Fede ◽  
O. Simonin ◽  
I. Ghouila
Keyword(s):  
Numerical Simulation ◽  
Fluidized Bed ◽  
Ethylene Polymerization ◽  
Solid Phase ◽  
Three Dimensional ◽  
Gas Velocity ◽  
Particle Segregation ◽  
3D Numerical Simulation ◽  
Model Predictions ◽  
The Mean

Three dimensional unsteady numerical simulations of dense pressurized polydisperse fluidized bed have been carried out. The geometry is a medium-scale industrial pilot for ethylene polymerization. The numerical simulation have been performed with a polydisperse collision model. The consistency of the polydisperse model predictions with the monodisperse ones is shown. The results show that the pressure distribution and the mean vertical gas velocity are not modified by polydispersion of the solid phase. In contrast, the solid particle species are not identically distributed in the fluidized bed indicating the presence of particle segregation.

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