Influence of Bubble‐Surface Contamination on Instantaneous Mass Transfer

Huang, Jie; Saito, Takayuki

doi:10.1002/ceat.201500056

Cited by 20 publications

(11 citation statements)

References 18 publications

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“…One focus is on the changing mass transfer when surfactants are added [10,17]. In recent years, the effect of surfactants has also been studied numerically [18,19].…”

Section: Introductionmentioning

confidence: 99%

The Bubble Shape in Contaminated Bubbly Flows: Results for Different NaCl Concentrations in Purified Water

et al. 2018

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Abstract:The bubble shape influences the transfer of momentum and heat/mass between the bubble and the surrounding fluid as well as the flow field around the bubble. The shape is determined by the interaction of the fluid field in the bubble, the physics on the surface, and the surrounding flow field. It is well known that contaminations can disturb the surface physics so that the bubble shape can be influenced. Indeed, an influence of sodium chloride (NaCl) on the hydrodynamics of bubbly flows was shown for air/water systems in previous studies. The aim of the present work is to investigate if, and to what extent, the NaCl concentration affects the bubble shape in bubble columns. For this purpose, several experiments at the Helmholtz-Zentrum Dresden-Rossendorf and at the pilot-scale bubble column at the Politecnico di Milano are evaluated. The experiments were executed independently from each other and were evaluated with different methods. All experiments show that the bubble shape is not distinctly affected in the examined concentration range from 0 to 1 M NaCl, which is in contrast to a previous study on single bubbles. Therefore, the effect of NaCl on the hydrodynamics of bubbly flows is not induced by the bubble shape.

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“…One focus is on the changing mass transfer when surfactants are added [10,17]. In recent years, the effect of surfactants has also been studied numerically [18,19].…”

Section: Introductionmentioning

confidence: 99%

The Bubble Shape in Contaminated Bubbly Flows: Results for Different NaCl Concentrations in Purified Water

et al. 2018

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“…By the way, the influence of surfactants is highly significant during the bubble generation process. However, surfactants exert very complicated effects on the oxygen transfer coefficient 11 and the microbubbles (∼ 50 μm) used in this work are too stable to coalesce. Consequently, a surfactant is not used in this work.…”

Section: Introductionmentioning

confidence: 99%

Gas‐Liquid Mass Transfer Characteristics with Microbubble Aeration – I. Standard Stirred Tank

Zu³

et al. 2016

Chem Eng & Technol

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More knowledge has to be acquired on the gas-liquid mass transfer characteristics with microbubble aeration before an efficient bioreactor is designed. Experiments about this subject have been conducted in a stirred reactor. Some valuable conclusions were obtained: the shaft power consumption is little affected by the superficial gas velocity (v s ) and the power consumption of the microbubble generator is rather high; the dispersion of microbubbles is more uniform compared to sparger aeration; surface aeration leads to a reduced microbubble number and the diameter of the microbubble increases with higher superficial gas velocity; when surface aeration happens, the k L a-v s curves turn quite abnormally different from that in the case of sparger aeration, and correlation-based calculations fit well with the measurements.

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“…Long-term fluctuations of the void fraction (L PFVF ) were successfully extracted through the above optical fiber probing. The L PFVF faded away in accord with height of the flow (Higuchi and Saito, 2010) as shown in Figure 9; i.e. the large-scale structure of the bubbly flow in the vessel appeared to become weaker toward the vessel's upper surface.…”

Section: Practical Use Of the S-top And Other Types Of Optical Fiber mentioning

confidence: 91%

“…here, f(x, y, t) represents the point-wise and spatial void fraction at a position (x, y) and time t; A a the area which has characteristics similar to those of a void fraction; f a the point-wise and temporal void fraction at a position (x, y) and time t; t 1 and t 2 the time interval which we are considering. On the basis of this relationship, we investigated longterm fluctuations (which reflect the large-scale structure of the bubbly flow) in the bubble column, using an S-TOP and a four-tip optical fiber probe (F-TOP; Figure 8) (Higuchi and Saito, 2010). The row data obtained through the S-TOP and F-TOP were processed by our new algorithm (Sakamoto and Saito, 2012b).…”

Section: Practical Use Of the S-top And Other Types Of Optical Fiber mentioning

confidence: 99%

Improvement of Optical Fiber Probing in Multiphase Systems, and the Possibility of Practical Application in Chemical Engineering Processes

Saito

Sato

Nihei

et al. 2018

J. Chem. Eng. Japan / JCEJ

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Optical ber probing (OFP) is a very useful and practical technique for investigating and monitoring multiphase systems, and it is particularly suitable for simultaneously measuring a bubble's/droplet's chord length, velocity and number density in an industrial-scale apparatus, as well as a laboratory-scale setup. Here, we outline the principles of OFP and propose several types of optical ber probes that meet the requirements for particular purposes of the multiphase systems in chemical engineering processes. We describe measurement methods that use an optical ber probe suitably tuned for liquid lm and foam, as well as for bubble measurement. The basic measurement principle of OFP is very simple: the probe tip's detection of changes in the refraction indices from a gas phase to a liquid phase or vice versa. For example, to precisely measure a bubble's properties such as the chord length and velocity, it is necessary to determine the precise relationship between the process of the optical ber probe's penetration into the bubble and the optical signal. Since the probing signal provides a variety of information due to the complicated interaction of the laser beams, optical ber and gas-liquid interfaces, it is necessary to use both experimental and computational approaches in order to extract the physical meanings of the probe's signals. Using our own fully-3D ray-tracing simulator and well-arranged high-speed visualization setups, we discuss how to improve the measurement accuracy of OFP. We rst computationally analyze the OFP signals under several penetration conditions, and we explain our recommendations regarding how to improve the accuracy of a single-tip optical ber probe used for measurement in multiphase systems. On the basis of our present ndings and the improvement in measurement accuracy, we then propose several applications of OFP to chemical engineering processes.

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Influence of Bubble‐Surface Contamination on Instantaneous Mass Transfer

Cited by 20 publications

References 18 publications

The Bubble Shape in Contaminated Bubbly Flows: Results for Different NaCl Concentrations in Purified Water

The Bubble Shape in Contaminated Bubbly Flows: Results for Different NaCl Concentrations in Purified Water

Gas‐Liquid Mass Transfer Characteristics with Microbubble Aeration – I. Standard Stirred Tank

Improvement of Optical Fiber Probing in Multiphase Systems, and the Possibility of Practical Application in Chemical Engineering Processes

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