Experimental Investigation and Correlation of the Effect of Carbon Nanotubes on Bubble Column Fluid Dynamics: Gas Holdup, Flow Regime Transition, Bubble Size and Bubble Rise Velocity

2021 ◽  
Vol 139 ◽  
pp. 103647
Author(s):  
Ali Barati-Harooni ◽  
Mohammad Jamialahmadi
Keyword(s):  
Fluid Dynamics ◽  
Carbon Nanotubes ◽  
Experimental Investigation ◽  
Flow Regime ◽  
Bubble Size ◽  
Bubble Column ◽  
Gas Holdup ◽  
Rise Velocity ◽  
Flow Regime Transition ◽  
Bubble Rise Velocity

Influence of Operating Pressure on Gas Holdup and Flow Regime Transition in a Bubble Column

2010 ◽  
Vol 43 (10) ◽  
pp. 829-832 ◽  
Author(s):  
Hiroaki Matsubara ◽  
Kiyoshi Naito ◽  
Hideharu Kuwamoto ◽  
Toshiyuki Sakaguchi
Keyword(s):  
Flow Regime ◽  
Bubble Column ◽  
Gas Holdup ◽  
Operating Pressure ◽  
Regime Transition ◽  
Flow Regime Transition

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.

A Review on Flow Regime Transition in Bubble Columns

2007 ◽  
Vol 5 (1) ◽  
Author(s):  
Ashfaq Shaikh ◽  
Muthanna H. Al-Dahhan
Keyword(s):  
Flow Regime ◽  
Bubble Column ◽  
Flow Behavior ◽  
Scale Up ◽  
Experimental Studies ◽  
Flow Regimes ◽  
Bubble Columns ◽  
Linear Stability Theory ◽  
Regime Transition ◽  
Flow Regime Transition

Due to varied flow behavior, the demarcation of hydrodynamic flow regimes is an important task in the design and scale-up of bubble column reactors. This article reviews most hydrodynamic studies performed for flow regime identification in bubble columns. It begins with a brief introduction to various flow regimes. The second section examines experimental methods for measurement of flow regime transition. A few experimental studies are presented in detail, followed by the effect of operating and design conditions on flow regime transition. A table summarizes the reported experimental studies, along with their operating and design conditions and significant conclusions. The next section deals with the current state of transition prediction, and includes purely empirical correlations, semi-empirical models, linear stability theory, and Computational Fluid Dynamics (CFD) based studies.

Gas Holdup in a Cocurrent Air-Water-Fiber Bubble Column

Volume 3 ◽  
2004 ◽  
Author(s):  
Chengzhi Tang ◽  
Theodore J. Heindel
Keyword(s):  
Flow Regime ◽  
Mass Fraction ◽  
Liquid Velocity ◽  
Bubble Column ◽  
Complex Function ◽  
Cellulose Fiber ◽  
Gas Holdup ◽  
Fiber Network ◽  
Drift Flux Model ◽  
Superficial Gas Velocity

Effects of superficial liquid velocity (Ul), superficial gas velocity (Ug), and fiber mass fraction (C) on gas holdup (ε) and flow regime transition are studied experimentally in well-mixed water-cellulose fiber suspensions in a cocurrent bubble column. Experimental results show that the gas holdup decreases with increasing Ul when C and Ug are constant. The gas holdup is not significantly affected by C in the range of C < 0.4%, but decreases with increasing C in the range of 0.4% ≤ C ≤ 1.5%. When C > 1.5%, a significant amount of gas is trapped in the fiber network and recirculates with the water-fiber slurry in the system; as a result, the measured gas holdup is higher than that at C = 1.5%. The axial gas holdup distribution is shown to be a complex function of superficial gas and liquid velocities and fiber mass fraction. The drift-flux model is used to analyze the flow regime transitions at different conditions. Three distinct flow regimes are observed when C ≤ 0.4%, but only two are identified when 0.6% ≤ C ≤ 1.5%. The superficial gas velocities at which flow transition occurs from one regime to another are not significantly affected by Ul and slightly decrease with increasing C.

Effect of Vibrating Sparger on Mass Transfer, Gas Holdup, and Bubble Size in a Bubble Column Reactor

2013 ◽  
Vol 11 (1) ◽  
pp. 47-56 ◽  
Author(s):  
Laleh Hadavand ◽  
Ali Fadavi
Keyword(s):  
Mass Transfer ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Vibration Frequency ◽  
Bubble Size ◽  
Bubble Column ◽  
Gas Holdup ◽  
Bubble Column Reactor ◽  
Gas Velocity ◽  
Superficial Gas Velocity

Abstract Bubble size has a key role in gas holdup and mass transfer in bubble column reactors. In order to have small and uniform bubbles, a new structure was designed; the reactor operates in two modes, with vibrating sparger and conventional bubble column in which sparger is fixed. In vibrating mode, the sparger vibrates gently during gas entering. The vibrating sparger performs like a paddle, resulting in a forced recirculation of gas–liquid inside the reactor; moreover, the bubble detachment is accelerated. The superficial gas velocity was between 0.003 and 0.013 ms− 1, and the vibration frequency was changed between 0 and 10.3 Hz. The bubble size was measured at three various positions of the reactor height by photographic method and using MATLAB 7.0.1 software. The mass transfer coefficient was determined by means of the dynamic gassing-out method. The results show that the bubbles were bigger in vibrating mode than those working without vibration. The bubble size decreases with increase in height from sparger. Gas holdup increased with increase in superficial gas velocity and vibration frequency. The effect of vibration increased the gas holdup with an average of 70% for all superficial gas velocities. Volumetric mass transfer coefficient was almost stable as vibration frequency increased.

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