scholarly journals CFD Modeling and Simulation of the Hydrodynamics Characteristics of Coarse Coal Particles in a 3D Liquid-Solid Fluidized Bed

Minerals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 569
Author(s):  
Jian Peng ◽  
Wei Sun ◽  
Haisheng Han ◽  
Le Xie
Keyword(s):  
Experimental Data ◽  
Fluidized Bed ◽  
Fine Particles ◽  
Particle Density ◽  
Cfd Modeling ◽  
Hydrodynamic Characteristics ◽  
Model Parameters ◽  
Low Density ◽  
Coal Particles ◽  
Simulation Results

In this study, a Eulerian-Eulerian liquid-solid two-phase flow model combined with kinetic theory of granular flow was established to study the hydrodynamic characteristics and fluidization behaviors of coarse coal particles in a 3D liquid-solid fluidized bed. First, grid independence analysis was conducted to select the appropriate grid model parameters. Then, the developed computational fluid dynamics (CFD) model was validated by comparing the experimental data and simulation results in terms of the expansion degree of low-density fine particles and high-density coarse particles at different superficial liquid velocities. The simulation results agreed well with the experimental data, thus validating the proposed CFD mathematical model. The effects of particle size and particle density on the homogeneous or heterogeneous fluidization behaviors were investigated. The simulation results indicate that low-density fine particles are easily fluidized, exhibiting a certain range of homogeneous expansion behaviors. For the large and heavy particles, inhomogeneity may occur throughout the bed, including water voids and velocity fluctuations.

scholarly journals SIMULASI PENGARUH KECEPATAN GAS TERHADAP KARAKTERISTIK FLUIDISASI PADA FLUIDIZED BED MENGGUNAKAN METODE CFD

POROS ◽  
2018 ◽  
Vol 16 (1) ◽  
Author(s):  
Asyari Daryus Daryus
Keyword(s):  
Pressure Drop ◽  
Fluidized Bed ◽  
Particle Density ◽  
Gas Velocity ◽  
Experiment Data ◽  
Minimum Fluidization Velocity ◽  
Fluidization Velocity ◽  
Minimum Fluidization ◽  
Gas Fluidization ◽  
Simulation Results

The gas fluidization velocity or superficial gas velocity entering the fluidized bed will affect the fluidization in fluidized bed. If the superficial velocity is below the minimum fluidization velocity then there is no fluidization, and if it is more than it should be then the fluidization characteristic will be different. To obtain the effect of gas fluidization velocity to fluidization characteristics, it had been conducted the research on lab scale fluidized bed using CFD simulation method validated with the experiment data. The simulations used Gidaspow model for drag force and k-ε model for turbulent flow. From the experiments obtained that the minimum fluidization velocity was 0.4 m/s and the pressure drop was around 700 Pa. The simulation results for pressure drop across the bed were close to the experiment data for the gas fluidization velocity equal and bigger than the minimum fluidization velocity. For the velocity below the minimum fluidization velocity, there was the big differences between the simulation results and the experiment, so the simulation results cannot be used. For the fluidization velocity of 0.4 m/s and 0.45 m/s, fluidized bed showed the bubbling phenomena, and the higher velocity showed the bigger bubble. For the fluidization velocity of 0.50 m/s to 0.70 m/s, the fluidized bed showed the turbulent regime. In this regime, the bubble was breaking instead of growing and there was no clear bed surface observed. The simulation result for particle density showed that if the gas velocity was higher, the density of particles at the base of bed was decreasing since many of the particles was moving upwards. The particle density was lower in this regime than that of bubbling regime.

scholarly journals Application of Scaling-Law and CFD Modeling to Hydrodynamics of Circulating Biomass Fluidized Bed Gasifier

2021 ◽  
Author(s):  
Mazda Biglari ◽  
Hui Liu ◽  
Ali Elkamel ◽  
Ali Lohi
Keyword(s):  
Fluidized Bed ◽  
Particle System ◽  
Scaling Law ◽  
Computational Cost ◽  
Cfd Modeling ◽  
Hydrodynamic Characteristics ◽  
Small Scale ◽  
Small Column ◽  
Cfd Models ◽  
Fluidized Bed Gasifier

Two modeling approaches, the scaling-law and CFD (Computational Fluid Dynamics) approaches, are presented in this paper. To save on experimental cost of the pilot plant, the scaling-law approach as a low-computational-cost method was adopted and a small scale column operating under ambient temperature and pressure was built. A series of laboratory tests and computer simulations were carried out to evaluate the hydrodynamic characteristics of a pilot fluidized-bed biomass gasifier. In the small scale column solids were fluidized. The pressure and other hydrodynamic properties were monitored for the validation of the scaling-law application. In addition to the scaling-law modeling method, the CFD approach was presented to simulate the gas-particle system in the small column. 2D CFD models were developed to simulate the hydrodynamic regime. The simulation results were validated with the experimental data from the small column. It was proved that the CFD model was able to accurately predict the hydrodynamics of the small column. The outcomes of this research present both the scaling law with the lower computational cost and the CFD modeling as a more robust method to suit various needs for the design of fluidized-bed gasifiers.

scholarly journals Model-Based Design and Optimization of Blood Oxygenators

2020 ◽  
Vol 14 (4) ◽  
Author(s):  
Ge He ◽  
Tao Zhang ◽  
Jiafeng Zhang ◽  
Bartley P. Griffith ◽  
Zhongjun J. Wu
Keyword(s):  
Experimental Data ◽  
Carbon Dioxide ◽  
Fiber Bundle ◽  
Cfd Modeling ◽  
Design Parameters ◽  
Model Parameters ◽  
Transfer Rates ◽  
Design And Optimization ◽  
Model Based ◽  
Model Predictions

Abstract Blood oxygenators, also known as artificial lungs, are widely used in cardiopulmonary bypass surgery to maintain physiologic oxygen (O2) and carbon dioxide (CO2) levels in blood, and also serve as respiratory assist devices to support patients with lung failure. The time- and cost-consuming method of trial and error is initially used to optimize the oxygenator design, and this method is followed by the introduction of the computational fluid dynamics (CFD) that is employed to reduce the number of prototypes that must be built as the design is optimized. The CFD modeling method, while having progress in recent years, still requires complex three-dimensional (3D) modeling and experimental data to identify the model parameters and validate the model. In this study, we sought to develop an easily implemented mathematical models to predict and optimize the performance (oxygen partial pressure/saturation, oxygen/carbon dioxide transfer rates, and pressure loss) of hollow fiber membrane-based oxygenators and this model can be then used in conjunction with CFD to reduce the number of 3D CFD iteration for further oxygenator design and optimization. The model parameters are first identified by fitting the model predictions to the experimental data obtained from a mock flow loop experimental test on a mini fiber bundle. The models are then validated through comparing the theoretical results with the experimental data of seven full-size oxygenators. The comparative analysis show that the model predictions and experimental results are in good agreement. Based on the verified models, the design curves showing the effects of parameters on the performance of oxygenators and the guidelines detailing the optimization process are established to determine the optimal design parameters (fiber bundle dimensions and its porosity) under specific system design requirements (blood pressure drop, oxygen pressure/saturation, oxygen/carbon dioxide transfer rates, and priming volume). The results show that the model-based optimization method is promising to derive the optimal parameters in an efficient way and to serve as an intermediate modeling approach prior to complex CFD modeling.

Hydrodynamic characteristics of fine particles in the riser and standpipe of a circulating fluidized bed

1995 ◽  
Vol 12 (2) ◽  
pp. 141-145 ◽  
Author(s):  
Jong-Hyeun Choi ◽  
Jin-Ho Park ◽  
Won-Myung Choung ◽  
Yong Kang ◽  
Sang Done Kim
Keyword(s):  
Fluidized Bed ◽  
Fine Particles ◽  
Circulating Fluidized Bed ◽  
Hydrodynamic Characteristics

On the Research of Identification Methods for Supercapacitor Model Parameters

2015 ◽  
Vol 740 ◽  
pp. 499-502
Author(s):  
Qi Li ◽  
Wen Bin Zhang ◽  
Ping Li ◽  
Shi Su ◽  
Yu Ting Yan ◽  
...  
Keyword(s):  
Experimental Data ◽  
Parameter Estimation ◽  
Equivalent Circuit Model ◽  
Simulation System ◽  
New Method ◽  
Model Parameters ◽  
Identification Methods ◽  
Simulation Results ◽  
Charge Discharge ◽  
Constant Charge

The accuracy of model becomes increasingly demanding in the simulation system with the development of supercapacitor. The traditional methods of parameters identification in supercapacitor modeling are very complicated. This paper presents an easy and new method by the Simulink tool. The experimental data for the identification of the model parameters was obtained through the constant charge-discharge experiments. Then the variable capacitor of the supercapacitor equivalent circuit model was modeled in Simscape Language, so parameters directly got with Parameter estimation in Sumulink. Simulation results were presented and compared experimental data. And the result showed that the new method was not only speeded the identification of parameters, but also improved the modeling precision up to 98%.

scholarly journals Changes in some physical characteristics of the digesta in the reticulo-rumen of cows fed once daily

1973 ◽  
Vol 29 (3) ◽  
pp. 357-376 ◽  
Author(s):  
E. W. Evans ◽  
G. R. Pearce ◽  
J. Burnett ◽  
Susan L. Pillinger
Keyword(s):  
Dry Matter ◽  
Fine Particles ◽  
Particle Density ◽  
Matter Content ◽  
High Density ◽  
Dry Matter Content ◽  
Low Density ◽  
Coarse Particles ◽  
Minimum Concentration ◽  
Once Daily

1. Three cows were given 3, 5 or 7 kg hay once daily in a Latin-square design, and samples of digesta from four sites in the rumen and one site in the reticulum were taken at six times within the 24 h period after the feed. Dry-matter content and distribution of particle size and of particle density were measured for each sample. The changes in these measurements with time were studied. The incidence of rumination was also recorded.2. Dry-matter contents of samples ranged from 15 to 3%. Values for samples from the dorsal sacs of the rumen were considerably higher than those for samples from the ventral sites; they also changed more with time after feeding and with level of feeding.3. Particles were fractionated by sieving into six size groups with mean dimensions (mm) of 9·3 × 0·8, 4·4 × 0·6, 2·6 × 0·3, 1·6 × 0·25, 0·5 × 0·1 and smaller than 0·5 × 0·1. Coarse particles occurred at highest concentrations in the dorsal sacs of the rumen and responded to effects of time and level of feeding; smaller particles showed less response.4. Particle densities ranged from 800 g/l to 1500 g/l. The proportions of low-density particles were higher in samples from the dorsal sacs of the rumen than in samples from ventral sites; the latter samples had higher proportions of high-density particles than of low-density particles. The changes which occurred are discussed.5. The density of coarse particles tended to be low and that of fine particles tended to be high.6. Rumination started at the time of maximum concentration of particles of low density and minimum concentration of particles of high density. Conversely, rumination ended when the concentration of the low-density particles was a minimum and that of the dense particles a maximum.7. The results are discussed in relation to the possible movement of particles within the reticulo-rumen and the kinetics of particle breakdown.

scholarly journals CFD Modeling and Simulation of Hydrodynamics in a Fluidized Bed Dryer with Experimental Validation

2011 ◽  
Vol 2011 ◽  
pp. 1-9 ◽  
Author(s):  
Mahdi Hamzehei
Keyword(s):  
Fluidized Bed ◽  
Fluid Dynamic ◽  
Expansion Ratio ◽  
Industrial Applications ◽  
Solid Particles ◽  
Cfd Modeling ◽  
Momentum Exchange ◽  
Fluidized Bed Dryer ◽  
Wide Range ◽  
Simulation Results

Gas-solid fluidized bed dryers are used in a wide range of industrial applications. With applying computational fluid dynamic (CFD) techniques, hydrodynamics of a two-dimensional nonreactive gas-solid fluidized bed dryer was investigated. A multifluid Eulerian model incorporating the kinetic theory for solid particles was applied to simulate the unsteady state behavior of this dryer and momentum exchange coefficients were calculated by using the Syamlal-O'Brien drag functions. A suitable numerical method that employed finite volume method was used to discretize the equations. Simulation results also indicated that small bubbles were produced at the bottom of the bed. These bubbles collided with each other as they moved upwards forming larger bubbles. Also, solid particles diameter and superficial gas velocity effect on hydrodynamics were studied. Simulation results were compared with the experimental data in order to validate the CFD model. Pressure drops and bed expansion ratio as well as the qualitative gas-solid flow patterns predicted by the simulations were in good agreement with experimental measurements at superficial gas velocities higher than the minimum fluidization velocity. Furthermore, this comparison showed that the model can predict hydrodynamic behavior of gas solid fluidized bed reasonably well.

Modelling Three-Phase Fluidized Bed Bioreactor for Wastewater Treatment

2008 ◽  
Vol 6 (1) ◽  
Author(s):  
Leila Boumehdi Toumi ◽  
Maamar Fedailaine ◽  
Khedidja Allia
Keyword(s):  
Experimental Data ◽  
Fluidized Bed ◽  
Biological Treatment ◽  
Fluidized Bed Reactor ◽  
Granular Structure ◽  
Solid Mass ◽  
Biodegradation Rate ◽  
Fluidized Bed Bioreactor ◽  
Three Phase ◽  
Simulation Results

Economically and technically interesting, the bioreactor phenomena are studied on both micro (pore and particle size) and macro (bioreactor) levels, to describe synergetic between bio-dynamics and physicochemical dynamics. Still, the three-phase bioreactors modelling remains complex. It requires taking into account numerous factors: the pollutant biodegradation rate in the biofilm, the reactant interfacial gas-liquid and liquid-solid mass transfer, the biofilm composition and growth, the granular structure and all the transfer phenomena occurring between phases in presence. The aim of this paper is to present a model based on biofilm composition and growth, the fluidized bed structure and its hydrodynamics. The simulation results are compared with our experimental data obtained for a biological treatment, carried out in three-phase fluidized bed reactor for hydrocarbons removal from refinery wastewaters. The equipment used is laboratory scale and the obtained results show that we could degrade hydrocarbons efficiently.

scholarly journals Simulation on hydrodynamics of non-spherical particulate system using a drag coefficient correlation based on artificial neural network

2019 ◽  
Vol 17 (2) ◽  
pp. 537-555
Author(s):  
Sheng-Nan Yan ◽  
Tian-Yu Wang ◽  
Tian-Qi Tang ◽  
An-Xing Ren ◽  
Yu-Rong He
Keyword(s):  
Neural Network ◽  
Experimental Data ◽  
Artificial Neural Network ◽  
Drag Coefficient ◽  
Fluidized Bed ◽  
Spherical Particles ◽  
Coefficient Corrélation ◽  
Bubbling Fluidized Bed ◽  
Simulation Results ◽  
Artificial Neural

AbstractFluidization of non-spherical particles is very common in petroleum engineering. Understanding the complex phenomenon of non-spherical particle flow is of great significance. In this paper, coupled with two-fluid model, the drag coefficient correlation based on artificial neural network was applied in the simulations of a bubbling fluidized bed filled with non-spherical particles. The simulation results were compared with the experimental data from the literature. Good agreement between the experimental data and the simulation results reveals that the modified drag model can accurately capture the interaction between the gas phase and solid phase. Then, several cases of different particles, including tetrahedron, cube, and sphere, together with the nylon beads used in the model validation, were employed in the simulations to study the effect of particle shape on the flow behaviors in the bubbling fluidized bed. Particle shape affects the hydrodynamics of non-spherical particles mainly on microscale. This work can be a basis and reference for the utilization of artificial neural network in the investigation of drag coefficient correlation in the dense gas–solid two-phase flow. Moreover, the proposed drag coefficient correlation provides one more option when investigating the hydrodynamics of non-spherical particles in the gas–solid fluidized bed.

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