Numerical Simulation of Effect of Internals on Slugging Fluidization and Analysis of Nonuniformity Index

2012 ◽  
Vol 10 (1) ◽  
Author(s):  
Xiaoling Wang ◽  
Liang Yu ◽  
Jun Wang
Keyword(s):  
Experimental Data ◽  
Granular Flow ◽  
Fluidized Beds ◽  
Fluid Model ◽  
Two Fluid Model ◽  
Reasonable Prediction ◽  
Two Fluid ◽  
Radial Nonuniformity ◽  
Flow Nonuniformity

Abstract The Two-Fluid Model (TFM) using the Kinetic Theory of Granular Flow (KTGF) was applied to simulate 3-D dense fluidized beds with different complex internals. The slugging fluidization was found in the simulated results. When the internals were placed into the reactors, the simulated results showed that the slugs were broken up and bubbling fluidization was formed instead of slugging fluidization. The formation, growth, size, and shape of bubbles were validated to ensure a reasonable prediction. Furthermore, the simulated pressure drop was compared with the corresponding experimental data from the dense fluidized beds with different complex internals, and good agreements were observed. Finally, the flow nonuniformity in the dense fluidized beds was evaluated by a developed method. This method extended Radial Nonuniformity Index (RNI) to Face Nonuniformity Index (FNI) and Volume Nonuniformity Index (VNI). From the calculated FNI and VNI, the fluidization quality of the fluidized beds was quantitatively judged as follows: No.3 > No.1> No.2 > No.4 > Without Internal.

Initiation and Statistical Evolution of Horizontal Slug Flow With a Two-Fluid Model

2013 ◽  
Vol 135 (12) ◽  
Author(s):  
A. O. Nieckele ◽  
J. N. E. Carneiro ◽  
R. C. Chucuya ◽  
J. H. P. Azevedo
Keyword(s):  
Experimental Data ◽  
Slug Flow ◽  
Fluid Model ◽  
Subsequent Development ◽  
Complex Flow ◽  
Horizontal Pipes ◽  
Dimensional Version ◽  
Two Fluid Model ◽  
Log Normal ◽  
Two Fluid

In the present work, the onset and subsequent development of slug flow in horizontal pipes is investigated by solving the transient one-dimensional version of the two-fluid model in a high resolution mesh using a finite volume technique. The methodology (named slug-capturing) was proposed before in the literature and the present work represents a confirmation of its applicability in predicting this very complex flow regime. Further, different configurations are analyzed here and comparisons are performed against different sets of experimental data. Predictions for mean slug variables were in good agreement with experimental data. Additionally, focus is given to the statistical properties of slug flows such as shapes of probability density functions of slug lengths (which were represented by gamma and log-normal distributions) as well as the evolution of the first statistical moments, which were shown to be well reproduced by the methodology.

scholarly journals Hybrid Two-Fluid DEM Simulation of Gas-Solid Fluidized Beds

2006 ◽  
Author(s):  
Jin Sun ◽  
Francine Battaglia ◽  
S. Subramaniam
Keyword(s):  
Momentum Transfer ◽  
Fluidized Beds ◽  
Structural Information ◽  
Fluid Model ◽  
Fluid Phase ◽  
Transfer Model ◽  
Dem Simulation ◽  
Dem Simulations ◽  
Two Fluid Model ◽  
Two Fluid

Simulations of gas-solid fluidized beds have been carried out using a hybrid simulation method, which couples the discrete element method (DEM) for particle dynamics with the ensemble-averaged two-fluid (TF) equations for the fluid phase. The coupling between the two phases is modeled using an interphase momentum transfer term. The results of the hybrid TF-DEM simulations are compared to experimental data and two-fluid model simulations. It is found that the TF-DEM simulation is capable of predicting general fluidized bed dynamics, i.e., pressure drop across the bed and bed expansion, which are in agreement with experimental measurements and two-fluid model predictions. In addition, the TF-DEM model demonstrates the capability to capture more heterogeneous structural information of the fluidized beds than the two-fluid model alone. The microstructures in fluidized beds are analyzed and the implications to kinetic theory for granular flows are discussed. However, the TF-DEM simulations depend on the form of the interphase momentum transfer model, which can be computed in terms of averaged or instantaneous particle quantities. Various forms of the interphase momentum transfer model are examined, and their suitability to the hybrid TF-DEM simulation approach is evaluated.

Flow Characteristics in an Airlift Membrane Bioreactor

2009 ◽  
Vol 4 (5) ◽  
Author(s):  
Amirhossein Khalili ◽  
MR Mehrnia ◽  
Navid Mostoufi ◽  
Mohammad Sarrafzadeh
Keyword(s):  
Shear Stress ◽  
Membrane Bioreactor ◽  
Fluid Model ◽  
Membrane Surface ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Liquid Level ◽  
Two Fluid Model ◽  
Two Fluid

Effect of changing the liquid level in an airlift membrane bioreactor of 0.7 m height, 0.24 m width and 0.18 m depth was studied both experimentally and by simulation. Three-dimensional simulations of the airlift membrane bioreactor were carried out at two different liquid levels above the membrane. The simulations were based on the two-fluid model with the standard k–? model for the turbulence. The results showed that by lowering the liquid level, the quality of mixing and uniformity of the velocity distribution of liquid phase in the riser would be improved while the shear stress on the membrane surface would be reduced. Higher shear stress on the membrane surface at high levels of liquid minimizes the extent to which particles settle on the membrane, thus, fouling will be reduced and flux of liquid through membrane will be enhanced. Moreover, it was shown that by lowering the liquid level, the fraction of air in the downcomers becomes lower.

scholarly journals Use of α -shapes for the measurement of 3D bubbles in fluidized beds from two-fluid model simulations

2016 ◽  
Vol 288 ◽  
pp. 409-421 ◽  
Author(s):  
Ignacio Julián ◽  
David González ◽  
Javier Herguido ◽  
Miguel Menéndez
Keyword(s):  
Fluidized Beds ◽  
Fluid Model ◽  
Model Simulations ◽  
Two Fluid Model ◽  
Two Fluid

Two-Fluid-Model-Based Full Physics Simulations of Mixing in Noncohesive Wet Fluidized Beds

2019 ◽  
Vol 58 (27) ◽  
pp. 12323-12346 ◽  
Author(s):  
Maryam Askarishahi ◽  
Mohammad-Sadegh Salehi ◽  
Stefan Radl
Keyword(s):  
Fluidized Beds ◽  
Fluid Model ◽  
Model Based ◽  
Two Fluid Model ◽  
Two Fluid

scholarly journals Pattern formation in fluidized beds as a tool for model validation: A two-fluid model based study

2016 ◽  
Vol 295 ◽  
pp. 35-42 ◽  
Author(s):  
Kaiqiao Wu ◽  
Lilian de Martín ◽  
Luca Mazzei ◽  
Marc-Olivier Coppens
Keyword(s):  
Pattern Formation ◽  
Model Validation ◽  
Fluidized Beds ◽  
Fluid Model ◽  
Model Based ◽  
Two Fluid Model ◽  
Two Fluid
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