The Effects of Isobutanul Addition on Bubble Size, Gas Holdup, Interfacial Area, Bubble Coalescence, and Transition Concentration in Dispersion Column

Bubble sizes in bubble column affect transfer processes. Therefore, it’s important to calculate bubble size and interfacial area. Bubble size distribution (BSD) in a bubble column of rectangular cross section with dimensions 0.2m x 0.02m was measured using photographic method (400 fps) for air-water system. Gas holdup, Sauter-mean bubble diameter, aspect ratio and specific interfacial area were estimated from BSD. Effect of superficial gas velocity and static bed height on these parameters was investigated. The bubble size distribution exhibited mono-modal distribution showing the presence of non-uniform homogeneous bubbling regime. The frames of video were analysed using image processing steps to obtain major and minor axis of elliptical bubbles. Values of d32, , and ai were estimated from the data. The value of d32 increased with increasing Ug but is independent of Hs. The values of d32 were somewhat higher than the values reported by other investigators. The value of ai increases with increasing Ug and with decreasing Hs. Present values of compared well with the data reported in literature.

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Numerical Simulation of Bubble Coalescence and Break-Up in Multinozzle Jet Ejector

Journal of Applied Mathematics ◽

10.1155/2016/5238737 ◽

2016 ◽

Vol 2016 ◽

pp. 1-19

Author(s):

Dhanesh Patel ◽

Ashvinkumar Chaudhari ◽

Arto Laari ◽

Matti Heiliö ◽

Jari Hämäläinen ◽

...

Keyword(s):

Bubble Size ◽

Turbulence Modeling ◽

Three Dimensional ◽

Interfacial Area ◽

Industrial Applications ◽

Bubble Coalescence ◽

Ansys Fluent ◽

Numerical Predictions ◽

Size Groups ◽

Rans Models

Designing the jet ejector optimally is a challenging task and has a great impact on industrial applications. Three different sets of nozzles (namely, 1, 3, and 5) inside the jet ejector are compared in this study by using numerical simulations. More precisely, dynamics of bubble coalescence and breakup in the multinozzle jet ejectors are studied by means of Computational Fluid Dynamics (CFD). The population balance approach is used for the gas phase such that different bubble size groups are included in CFD and the number densities of each of them are predicted in CFD simulations. Here, commercial CFD softwareANSYS Fluent 14.0is used. The realizablek-εturbulence model is used in CFD code in three-dimensional computational domains. It is clear that Reynolds-Averaged Navier-Stokes (RANS) models have their limitations, but on the other hand, turbulence modeling is not the key issue in this study and we can assume that the RANS models can predict turbulence of the carrying phase accurately enough. In order to validate our numerical predictions, results of one, three, and five nozzles are compared to laboratory experiments data for Cl2-NaOH system. Predicted gas volume fractions, bubble size distributions, and resulting number densities of the different bubble size groups as well as the interfacial area concentrations are in good agreement with experimental results.

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Closure Laws for the Transport Equation of Interfacial Area in Dispersed Flow

Volume 1: Fora, Parts A and B ◽

10.1115/fedsm2002-31386 ◽

2002 ◽

Author(s):

X. Rioua ◽

J. Fabrea ◽

C. Colin

Keyword(s):

Transport Equation ◽

Size Distribution ◽

Bubble Size ◽

Interfacial Area ◽

Bubble Size Distribution ◽

Bubble Coalescence ◽

Size Distributions ◽

Mean Diameter ◽

The Mean ◽

Two Fluid

Derivation of a transport equation for the interfacial area concentration. In two-phase flows, the interfacial area is a key parameter since it mainly controls the momentum heat and mass transfers between the phases. An equation of transport of interfacial area may be very useful, especially for the two-fluid models. Such an equation should be able to predict the transition between the flow regimes. With this aim in view, we shall focus our attention on pipe flow. Besides in a first step, our study will be limited to dispersed flows. Different models are used to predict the evolution of bubble sizes. Some models use a population balance that provides a detailed description of the bubble size distributions, but they require as many equations as diameter ranges (Coulaloglou & Tavlarides1). Some others use only one equation for the transport of the mean interfacial area (Hibiki & Ishii2). In that case the bubble size distribution is treated as it would be monodispersed, its mean diameter being equal to the Sauter diameter. An intermediate approach was proposed by Kamp et al.3, in which polydispersed size distributions can be taken into account. It is the starting point of the present study in which: • The choice of an interfacial velocity is discussed. • The sink and source terms due to bubble coalescence, break-up or phase change are established. The model of Kamp et al. consists of transport equations of the various moments of the density probability function P(d) of the bubble diameter. In many experimental situations, P(d) is well predicted by a log-normal law (with two characteristic parameters d00 the central diameter of the distribution and a width parameter): The different moments of order ? of P(d) may be calculated: Sγ=n∫P(d)dγd(d)(1) where n is the bubble number density, S1/n, the mean diameter and S2/?, the interfacial area. A transport equation can be written for each moment: ∂Sγ∂t+∇·(uGSγ)=φγ(2) The lhs of (2) is an advection term by the gas velocity uG and the rhs is a source or sink term due to bubble coalescence, break-up or mass transfer. Since the bubble size distribution is characterised by the two parameters d00 and σˆ, only two transport equations (for S1 and S2) have to be solved to calculate the space-time evolution of the bubble size distribution. These two equations are still too cumbersome for a two-fluid model. Under some hypotheses (σˆ ∼ constant), they are lead to a single equation for the interfacial area. In its dimensionless form the interfacial area ai+ (ai+ = π S2 D, where D is the pipe diameter) reads: d/dt+(ai+)=f(RG,Re,We,ai+)(3) where RG is the gas fraction, Re is the Reynolds number of the mixture, We the Weber number of the mixture and t+ a dimensionless time.

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Numerical investigation on the performance of coalescence and break-up kernels in subcooled boiling flows in vertical channels

The Journal of Computational Multiphase Flows ◽

10.1177/1757482x16679417 ◽

2016 ◽

Vol 9 (2) ◽

pp. 71-85 ◽

Cited By ~ 1

Author(s):

Sara Vahaji ◽

Sherman CP Cheung ◽

Lilunnahar Deju ◽

Guan Yeoh ◽

Jiyuan Tu

Keyword(s):

Size Distribution ◽

Bubble Size ◽

Bubble Dynamics ◽

Interfacial Area ◽

Bubble Size Distribution ◽

Heated Wall ◽

Bubble Coalescence ◽

Two Phase ◽

Interfacial Area Concentration ◽

Break Up

In order to accurately predict the thermal hydraulic of two-phase gas–liquid flows with heat and mass transfer, special numerical considerations are required to capture the underlying physics: characteristics of the heat transfer and bubble dynamics taking place near the heated wall and the evolution of the bubble size distribution caused by the coalescence, break-up, and condensation processes in the bulk subcooled liquid. The evolution of the bubble size distribution is largely driven by the bubble coalescence and break-up mechanisms. In this paper, a numerical assessment on the performance of six different bubble coalescence and break-up kernels is carried out to investigate the bubble size distribution and its impact on local hydrodynamics. The resultant bubble size distributions are compared to achieve a better insight of the prediction mechanisms. Also, the void fraction, bubble Sauter mean diameter, and interfacial area concentration profiles are compared against the experimental data to ensure the validity of the models applied.

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Gas holdup and its relation to interfacial area in bubble-type reactors

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19740528 ◽

1974 ◽

Vol 39 (2) ◽

pp. 528-538 ◽

Cited By ~ 4

Author(s):

F. Kaštánek ◽

V. Nývlt ◽

M. Rylek

Keyword(s):

Interfacial Area ◽

Gas Holdup

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CFD Simulation of Gas Dispersion in a Stirred Tank of Dual Rushton Turbines

International Journal of Chemical Reactor Engineering ◽

10.1515/ijcre-2016-0221 ◽

2017 ◽

Vol 15 (4) ◽

Cited By ~ 2

Author(s):

Xinju Li ◽

Xiaoping Guan ◽

Rongtao Zhou ◽

Ning Yang ◽

Mingyan Liu

Keyword(s):

Flow Field ◽

Size Distribution ◽

Liquid Flow ◽

Bubble Size ◽

Great Influence ◽

Gas Holdup ◽

Bubble Size Distribution ◽

Stirred Tank ◽

Treatment Methods ◽

Gas Dispersion

Abstract3D Eulerian-Eulerian model was applied to simulate the gas-liquid two-phase flow in a stirred tank of dual Rushton turbines using computational fluid dynamics (CFD). The effects of two different bubble treatment methods (constant bubble sizevs. population balance model, PBM) and two different coalescence models (Luo modelvs. Zaichik model) on the prediction of liquid flow field, local gas holdup or bubble size distribution were studied. The results indicate that there is less difference between the predictions of liquid flow field and gas holdup using the above models, and the use of PBM did not show any advantage over the constant bubble size model under lower gas holdup. However, bubble treatment methods have great influence on the local gas holdup under larger gas flow rate. All the models could reasonably predict the gas holdup distribution in the tank operated at a low aeration rate except the region far from the shaft. Different coalescence models have great influence on the prediction of bubble size distribution (BSD). Both the Luo model and Zaichik model could qualitatively estimate the BSD, showing the turning points near the impellers along the height, but the quantitative agreement with experiments is not achieved. The former over-predicts the BSD and the latter under-predicts, showing that the existing PBM models need to be further developed to incorporate more physics.

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Acoustic Measurement in a Rectangular Bubble Column to Determine Bubble Size and Interfacial Area for Aqueous Solutions of Ethylene Glycol

International Journal of Recent Technology and Engineering - 2 ◽

10.35940/ijrte.b1794.078219 ◽

2019 ◽

Vol 8 (2) ◽

pp. 994-998

Keyword(s):

Ethylene Glycol ◽

Bubble Size ◽

Bubble Column ◽

Bubble Diameter ◽

Water System ◽

Interfacial Area ◽

Bed Height ◽

Specific Interfacial Area ◽

Bubble Sizes ◽

Distributor Plate

Bubble sizes in bubble column affect the bubble induced mixing of phases, interfacial area and transfer processes. Acoustic technique is used to measure bubble size distribution in a rectangular bubble column of cross section 0.2m x 0.02m for air sparged into water and aqueous solutions of ethylene glycol. Five condenser mikes at intermediate distance of 0.05 m measured above the distributor plate were used to find out the variation of bubble size as the bubbles move up. Sauter-mean bubble diameter and specific interfacial area were estimated from bubble size distribution at several superficial air velocity, static bed height, distance above the distributor plate and ethylene glycol concentration. The BSD exhibited mono-modal distribution and indicated non-uniform homogeneous bubbling regime. Sauter-mean bubble diameter is independent of superficial gas velocity, static bed height and concentration of EG, although, the values were higher than that for air-water system. Sauter-mean bubble diameter decreases as the bubbles move up indicating bubble breakup to take place once the bubbles leave the sparger. The value of interfacial area increases as the static bed height decreases and distance above the distributor plate increases. For air-ethylene glycol solution the values of specific interfacial area are about 200% higher than that observed in case of air-water system. The acoustic technique may be used to measure local values of bubble sizes and specific interfacial area.

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