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.

Numerical Analysis of Heat Transfer Test of Supercritical Water in a Tube Using the Three-Dimensional Two-Fluid Model Code

2008 ◽  
Author(s):  
Takeharu Misawa ◽  
Hiroyuki Yoshida ◽  
Hidesada Tamai ◽  
Kazuyuki Takase
Keyword(s):  
Heat Transfer ◽  
Fluid Model ◽  
Three Dimensional ◽  
Design Procedure ◽  
Supercritical Pressure ◽  
Thermal Design ◽  
Energy Agency ◽  
Pressure Region ◽  
Two Fluid Model ◽  
Two Fluid

The three-dimensional two-fluid model analysis code ACE-3D is developed in Japan Atomic Energy Agency for the thermal design procedure on two-phase flow thermal-hydraulics of light water-cooled reactors. In order to perform thermal hydraulic analysis of SCWR, ACE-3D is enhanced to supercritical pressure region. As a result, it is confirmed that transient change in subcritical and supercritical pressure region can be simulated smoothly using ACE-3D, that ACE-3D can predict the results of the past heat transfer experiment in the supercritical pressure condition, and that introduction of thermal conductivity effect of the wall restrains fluctuation of wall.

scholarly journals Simulation of Free Surface Compressible Flows via a Two Fluid Model

2008 ◽  
Author(s):  
Fre´de´ric Dias ◽  
Denys Dutykh ◽  
Jean-Michel Ghidaglia
Keyword(s):  
Free Surface ◽  
Wave Breaking ◽  
Compressible Flows ◽  
Fluid Model ◽  
Three Dimensional ◽  
Two Fluids ◽  
Equation Of States ◽  
Two Fluid Model ◽  
Velocity Pressure ◽  
Two Fluid

The purpose of this communication is to discuss the simulation of a free surface compressible flow between two fluids, typically air and water. We use a two fluid model with the same velocity, pressure and temperature for both phases. In such a numerical model, the free surface becomes a thin three dimensional zone. The present method has at least three advantages: (i) the free-surface treatment is completely implicit; (ii) it can naturally handle wave breaking and other topological changes in the flow; (iii) one can easily vary the Equation of States (EOS) of each fluid (in principle, one can even consider tabulated EOS). Moreover, our model is unconditionally hyperbolic for reasonable EOS.

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.

Development of a Transient Mechanistic Two-Phase Flow Model for Wellbores

SPE Journal ◽  
2012 ◽  
Vol 17 (03) ◽  
pp. 942-955 ◽  
Author(s):  
Mahdy Shirdel ◽  
Kamy Sepehrnoori
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Two Phase Flow ◽  
Fluid Model ◽  
Flow Regimes ◽  
Phase Flow ◽  
Two Phase ◽  
Wall Shear ◽  
Two Fluid Model ◽  
Two Fluid

Summary A great deal of research has been focused on transient two-phase flow in wellbores. However, there is lack of a comprehensive two-fluid model in the literature. In this paper, we present an implementation of a pseudo-compositional, thermal, fully implicit, transient two-fluid model for two-phase flow in wellbores. In this model, we solve gas/liquid mass balance, gas/liquid momentum balance, and two-phase energy balance equations to obtain five primary variables: liquid velocity, gas velocity, pressure, holdup, and temperature. This simulator can be used as a stand-alone code or can be used in conjunction with a reservoir simulator to mimic wellbore/reservoir dynamic interactions. In our model, we consider stratified, bubbly, intermittent, and annular flow regimes using appropriate closure relations for interphase and wall-shear stress terms in the momentum equations. In our simulation, we found that the interphase and wall-shear stress terms for different flow regimes can significantly affect the model's results. In addition, the interphase momentum transfer terms mainly influence the holdup value. The outcome of this research leads to a more accurate simulation of multiphase flow in the wellbore and pipes, which can be applied to the surface facility design, well-performance optimization, and wellbore damage estimation.

scholarly journals A Two-Fluid Model for High Viscosity Upward Annular Flow in Vertical Pipes

2021 ◽  
Author(s):  
Joseph X. F. Ribeiro ◽  
Ruiquan Liao ◽  
Aliyu M. Aliyu ◽  
Salem K. B. Ahmed ◽  
Yahaya D. Baba ◽  
...  
Keyword(s):  
Fluid Model ◽  
Accurate Determination ◽  
Flow Characteristics ◽  
High Viscosity ◽  
Two Phase ◽  
Friction Factors ◽  
Two Fluid Model ◽  
Two Fluid ◽  
Selection Of

Selection of appropriate friction factors is paramount for accurate prediction of key flow characteristics in gas–liquid two-phase flows. In this work, experimental investigation of vertical air and oil (with viscosities up to 200 mPa s) flow in a 0.060-m ID pipe is reported. Superficial air and oil velocity ranges utilized are from 22.37 to 59.06 m/s and 0.05 to 0.16 m/s respectively. The influence of estimation of interfacial friction factor on accurate determination of film thickness, void fraction and pressure gradient was investigated using a two-fluid model. The results indicated that the two-fluid model is capable of accurately predicting flow characteristics. Further, it reveals that the best performing correlations are the Belt et al. and Ambrosini et al. correlations.

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