Prediction of Gas-Holdup in Filtered Containment Venting System

2014 ◽  
Author(s):  
Tobias Strömgren ◽  
Sven Perzon ◽  
Martin Karlsson ◽  
Eric Lillberg
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Water Level ◽  
Bubble Column ◽  
Flow Region ◽  
Gas Holdup ◽  
Severe Accident ◽  
Radioactive Pollution ◽  
Two Phase ◽  
Advantages And Disadvantages

A filter system to be used in order to reduce the radioactive pollution when reducing the pressure in the containment in case of a severe accident is developed. The radioactive pollution will be captured in the vessel that acts as a bubble column. To be able to maximize the water content in order to ensure that the radioactive pollution is captured it is of importance to predict the swelled water level in the vessel. In this study is three different methods to predict the gas holdup is presented and compared to experimental results; empirical correlations, thermal-hydraulic codes and Computational Fluid Dynamics (CFD). The advantages and disadvantages with the different methods are discussed. Both Computational Fluid Dynamics and the thermal hydraulic code (Gothic) show good predictions of the water level. Using empirical models it is crucial to have knowledge of the two-phase flow region in the bubble column.

Annular Gap Bubble Column: Experimental Investigation and Computational Fluid Dynamics Modeling

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
Giorgio Besagni ◽  
Gaël Raymond Guédon ◽  
Fabio Inzoli
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Flow Regime ◽  
Bubble Column ◽  
Gas Holdup ◽  
Operating Conditions ◽  
Optical Probes ◽  
Annular Gap ◽  
Fiber Optical ◽  
Flow Visualizations

This paper investigates the countercurrent gas–liquid flow in an annular gap bubble column with a 0.24 m inner diameter by using experimental and numerical investigations. The two-phase flow is studied experimentally using flow visualizations, gas holdup measurements, and double fiber optical probes in the following range of operating conditions: superficial air velocities up to 0.23 m/s and superficial water velocities up to −0.11 m/s, corresponding to gas holdups up to 29%. The flow visualizations were used to observe the flow patterns and to obtain the bubble size distribution (BSD). The gas holdup measurements were used for investigating the flow regime transitions, and the double fiber optical probes were used to study the local flow phenomena. A computational fluid dynamics (CFD) Eulerian two-fluid modeling of the column operating in the bubbly flow regime is proposed using the commercial software ansys fluent. The three-dimensional (3D) transient simulations have been performed considering a set of nondrag forces and polydispersity. It is shown that the errors in the global holdup and in the local properties are below 7% and 16%, respectively, in the range considered.

Hydrodynamics and Mass Transfer Simulation in Airlift Bioreactor with Settler using Computational Fluid Dynamics

2017 ◽  
Vol 15 (4) ◽  
Author(s):  
Oscar M. Hernández-Calderón ◽  
Marcos D. González-Llanes ◽  
Erika Y. Rios-Iribe ◽  
Sergio A. Jiménez-Lam ◽  
Ma.del Carmen Chavez-Parga ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Experimental Data ◽  
Mass Transfer ◽  
Computational Fluid Dynamics ◽  
Liquid Velocity ◽  
Fluid Dynamic ◽  
Gas Holdup ◽  
Airlift Bioreactor ◽  
Cfd Modeling ◽  
Two Phase

Abstract In this work, the effect of inlet-gas superficial velocity over the circulation liquid velocity, gas holdup and mass transfer, from an airlift bioreactor with settler were studied by Computational Fluid Dynamics (CFD) modeling and contrasted with experimental results. Multiphase mixture model and κ-ε turbulence model were used to describe the two phases gas-liquid flow pattern in airlift bioreactor. The hydrodynamic parameters such as liquid circulation velocity and gas holdup were computed by solving the governing equations of continuity, moment and turbulence transport using the finite volume method. Global mass transfer coefficient was evaluated through the Higbie’s penetration theory and the two-phase fluid dynamic theory. Comparison between our numerical data and experimental data previously reported in the literature was done. Numerical and experimental data were very close, and the differences found were discussed in terms of the limitations of this study.

Validation of a Computationally Efficient Computational Fluid Dynamics (CFD) Model for Industrial Bubble Column Bioreactors

2014 ◽  
Vol 53 (37) ◽  
pp. 14526-14543 ◽  
Author(s):  
Dale D. McClure ◽  
Hannah Norris ◽  
John M. Kavanagh ◽  
David F. Fletcher ◽  
Geoffrey W. Barton
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Bubble Column ◽  
Cfd Model ◽  
Computationally Efficient ◽  
Computational Fluid Dynamics Cfd

scholarly journals Numerical Simulation and Analysis on Spray Drift Movement of Multirotor Plant Protection Unmanned Aerial Vehicle

Energies ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 2399 ◽  
Author(s):  
Fengbo Yang ◽  
Xinyu Xue ◽  
Chen Cai ◽  
Zhu Sun ◽  
Qingqing Zhou
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Droplet Size ◽  
Wind Field ◽  
Flow Model ◽  
Two Phase Flow ◽  
Plant Protection ◽  
Three Dimensional ◽  
Phase Flow ◽  
Two Phase

In recent years, multirotor unmanned aerial vehicles (UAVs) have become more and more important in the field of plant protection in China. Multirotor unmanned plant protection UAVs have been widely used in vast plains, hills, mountains, and other regions, and become an integral part of China’s agricultural mechanization and modernization. The easy takeoff and landing performances of UAVs are urgently required for timely and effective spraying, especially in dispersed plots and hilly mountains. However, the unclearness of wind field distribution leads to more serious droplet drift problems. The drift and distribution of droplets, which depend on airflow distribution characteristics of UAVs and the droplet size of the nozzle, are directly related to the control effect of pesticide and crop growth in different growth periods. This paper proposes an approach to research the influence of the downwash and windward airflow on the motion distribution of droplet group for the SLK-5 six-rotor plant protection UAV. At first, based on the Navier-Stokes (N-S) equation and SST k–ε turbulence model, the three-dimensional wind field numerical model is established for a six-rotor plant protection UAV under 3 kg load condition. Droplet discrete phase is added to N-S equation, the momentum and energy equations are also corrected for continuous phase to establish a two-phase flow model, and a three-dimensional two-phase flow model is finally established for the six-rotor plant protection UAV. By comparing with the experiment, this paper verifies the feasibility and accuracy of a computational fluid dynamics (CFD) method in the calculation of wind field and spraying two-phase flow field. Analyses are carried out through the combination of computational fluid dynamics and radial basis neural network, and this paper, finally, discusses the influence of windward airflow and droplet size on the movement of droplet groups.

Comparison of four types of membrane bioreactor systems in terms of shear stress over the membrane surface using computational fluid dynamics

2013 ◽  
Vol 68 (12) ◽  
pp. 2534-2544 ◽  
Author(s):  
N. Ratkovich ◽  
T. R. Bentzen
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Membrane Fouling ◽  
Two Phase Flow ◽  
Membrane Surface ◽  
Cross Flow ◽  
Membrane Bioreactors ◽  
Phase Flow ◽  
Two Phase ◽  
Computational Fluid Dynamics Cfd

Membrane bioreactors (MBRs) have been used successfully in biological wastewater treatment to solve the perennial problem of effective solids–liquid separation. A common problem with MBR systems is clogging of the modules and fouling of the membrane, resulting in frequent cleaning and replacement, which makes the system less appealing for full-scale applications. It has been widely demonstrated that the filtration performances in MBRs can be greatly improved with a two-phase flow (sludge–air) or higher liquid cross-flow velocities. However, the optimization process of these systems is complex and requires knowledge of the membrane fouling, hydrodynamics and biokinetics. Modern tools such as computational fluid dynamics (CFD) can be used to diagnose and understand the two-phase flow in an MBR. Four cases of different MBR configurations are presented in this work, using CFD as a tool to develop and optimize these systems.

Features of Automotive Gas Tank Filler Pipe Two-Phase Flow: Experiments and Computational Fluid Dynamics Simulations

2002 ◽  
Vol 124 (2) ◽  
pp. 412-420 ◽  
Author(s):  
R. Banerjee ◽  
K. M. Isaac ◽  
L. Oliver ◽  
W. Breig
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Air Entrainment ◽  
Imaging Features ◽  
Two Phase ◽  
Progressive Development ◽  
Laminar To Turbulent Transition ◽  
Turbulent Transition ◽  
Extensive Flow ◽  
Dynamics Simulations

Extensive flow visualization in an automotive fuel filler pipe made visible by introducing dyes and smoke in water and air, respectively, were conducted for nominal flow rates of 4–18 liters per minute. Video and still cameras were used for imaging. Features of the flow such as laminar-to-turbulent transition, progressive development of strong swirl along filler pipe axis, air entrainment, and mixing with the liquid were observed in the experiments. The experimental observations were supported by computational fluid dynamics (CFD) simulations of the flow which also showed features such as swirl and air entrainment.

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