전해질용액 기포탑에서 기포특성

유동준 ( D. J. Yoo ),임대호 ( D. H. Lim ),전종설 ( J. S. Jeon ),양시우 ( S. W. Yang ),강용 ( Y. Kang ) 한국화학공학회 2016 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.54 No.4

Bubble properties such as size (chord length) and rising velocity were investigated in a bubble column with electrolyte solutions, of which diameter was 0.152m and 2.5m in height, respectively. The size and rising velocity of bubbles were measured by using the dual electrical resistivity probe method. Effects of gas and liquid velocities and ionic strength of liquid phase on the size and rising velocity of bubbles were determined. The bubble size increased with increasing gas velocity but decreased with increasing liquid velocity or ionic strength of liquid phase. The rising velocity of bubbles increased with increasing gas velocity and decreased with increasing ionic strength of liquid phase, however, it showed a slight maximum value with varying liquid velocity. The size and rising velocity of bubbles were well correlated with operating variables.

Generation of sub-micron (nano) bubbles and characterization of their fundamental properties

Sangbeom Kim,Hyoungjun Kim,Mooyoung Han,Tschungil Kim 대한환경공학회 2019 Environmental Engineering Research Vol.24 No.3

Although nanobubbles attract significant attention, their characteristics and applications have not been thoroughly defined. There are diverse opinions about the definition of nanobubbles and controversy regarding methods that verify their characteristics. This study defines nanobubbles as having a size less than 1 μm. The generation of these sub-micron (nano) bubbles may be verified by induced coalescence or light scattering. The size of a sub-micron (nano) bubbles may be measured by optical, and confocal laser scanning microscopy. Also, the size may be estimated by the relationship of bubble size with the dissolved oxygen concentration. However, further research is required to accurately define the average bubble size. The zeta potential of sub-micron (nano) bubbles decreases as pH increases, and this trend is consistent for micron bubbles. When the bubble size is reduced to about 700-900 nm, they become stationary in water and lose buoyancy. This characteristic means that measuring the concentration of sub-micron (nano) bubbles by volume may be possible by irradiating them with ultrasonic waves, causing them to merge into micron bubbles. As mass transfer is a function of surface area and rising velocity, this strongly indicates that the application of sub-micron (nano) bubbles may significantly increase mass transfer rates in advanced oxidation and aeration processes.

Hydrodynamics of Geldart group A particles in gas-solid fluidized beds

Lii-Ping Leu,Fu-Chien Tsai 한국화학공학회 2009 Korean Journal of Chemical Engineering Vol.26 No.2

Geldart group A particles were fluidized in a 10 cm i.d.×1.8 m high Plexiglas-made bed with ambient air to determine the hydrodynamic properties in a gas-solid fluidized bed. The effects of static bed heights, position of pressure measuring points, differential and absolute pressure fluctuations on the hydrodynamic behavior of a Geldart group A particles in a gas-solid fluidized bed were investigated. The particles used in this study were 80 micrometer FCC powders and 60 micrometer glass beads. The variance of pressure fluctuations was used to find the minimum bubbling velocity. The obtained minimum bubbling velocity was compared with the other methods available in the literature. This method was found to be much easier and had better data reproducibility than the classical visual method or sedimentation method. The variance of pressure fluctuations increased due to the increase of superficial gas velocity and static bed height. The obtained minimum bubbling velocity and pressure fluctuations were found to depend on the measuring position along the axial direction. The effect of measuring position was discussed. Cross-correlation of two pressure signals was used to find the delay time, then the bubble rising velocity.

기체 주입 Ladle내에서 유동특성에 관한 연구

오율권,서동표 조선대학교 에너지.자원신기술연구소 2003 에너지·자원신기술연구소 논문지 Vol.25 No.1

In the air-water model, the characteristics of flow parameters were experimentally investigated. When gas was injected into the liquid bath, several flow patterns were observed bubble-liquid plumb, the spout flow that occurred at the free surface, liquid circulation flow by bubble's behavior, etc. In the pure liquid region, the large and small several vortices were formed and irregularly circulated. These irregular repetition and circulation play a important role of mixing in the bath. The vortices were developed in the upper and the side wall regions and the movement of flow in the low region was very small. It is known as "dead zone". The bubble rise velocity in the bottom region was relatively lower than in the upper region because the energy generated by bubbles' behavior in the near nozzle region was almost converted into kinetic energy. But bubble rise velocity increases with the increasing the axial distance since kinetic energy of bubbles is added to buoyancy force.

DAF공정에서 개체군 수지를 이용한 기포-플록 응집체의 부상효율과 수리학적 부하율의 운전특성 평가

곽동희 대한상하수도학회 2008 상하수도학회지 Vol.22 No.5

A Simple Parameterization for the Rising Velocity of Bubbles in a Liquid Pool

박성훈,Changhwan Park,JinYong Lee,Byungchul Lee 한국원자력학회 2017 Nuclear Engineering and Technology Vol.49 No.4

The determination of the shape and rising velocity of gas bubbles in a liquid pool is of great importance in analyzing the radioactive aerosol emissions from nuclear power plant accidents in terms of the fission product release rate and the pool scrubbing efficiency of radioactive aerosols. This article suggests a simple parameterization for the gas bubble rising velocity as a function of the volume-equivalent bubble diameter; this parameterization does not require prior knowledge of bubble shape. This is more convenient than previously suggested parameterizations because it is given as a single explicit formula. It is also shown that a bubble shape diagram, which is very similar to the Grace's diagram, can be easily generated using the parameterization suggested in this article. Furthermore, the boundaries among the three bubble shape regimes in the Eo-Re plane and the condition for the bypass of the spheroidal regime can be delineated directly from the parameterization formula. Therefore, the parameterization suggested in this article appears to be useful not only in easily determining the bubble rising velocity (e.g., in postulated severe accident analysis codes) but also in understanding the trend of bubble shape change due to bubble growth.

총설: 액체 중에서 상승하는 기포의 크기, 형상 및 속도

박성훈,Park, Sung Hoon 한국입자에어로졸학회 2017 Particle and Aerosol Research Vol.13 No.1

본 총설에서는 액체층을 통과하는 기포의 크기, 형상, 상승속도를 결정하기 위한 이론들을 살펴보았다. 액체의 물리적 특성과 기포의 유량으로부터 기포의 크기, 형상, 상승속도를 체계적으로 계산하는 여러 가지 이론식 및 모수식들을 살펴보고, 각각의 장단점을 정리하였다. 이 분야에서 발표된 초기 저작들에서는 주로 반복계산을 통해 기포의 형상과 상승속도를 결정하는 기법들이 사용되었으나, 최근에 발표된 논문들에서는 간단한 모수식을 통해 기포의 형상과 상승속도를 반복계산 없이 쉽게 구하는 기법들이 제시되고 있다. 이러한 기법들은 매우 다양한 물리적 특성을 가지는 실험결과들과의 비교에서도 우수성을 보여주고 있어, 관련 분야의 연구에 매우 유용한 도구로 사용할 수 있을 것으로 보인다. Accurate prediction of size, shape and velocity of a bubble rising through a liquid pool is very important for predicting the particulate removal efficiency in pool scrubbing, for designing engineering safety features to prepare for severe accidents in nuclear power plants, and for predicting the emission of fission products from MCCI (molten core-concrete interaction) process during severe accidents. In this review article, previous studies on the determination of the size, shape and rising velocity of a bubble in liquid are reviewed. Various theoretical and parameterization formulas calculating the bubble size, shape and velocity from physical properties of liquid and gas flowrate are compared. Recent studies tend to suggest simple parameterizations that can easily determine the bubble shape and rising velocity without iteration, whereas iteration has to be performed to determine the bubble shape and velocity in old theories. The recent parameterizations show good agreement with measured data obtained from experiments conducted using different liquid materials with very diverse physical properties, proving themselves to be very useful tools for researchers in related fields.

Evaluation of pressure and viscous drags of a rising bubble at small Reynolds numbers

Long Cu Ngo,Hyoung Gwon Choi 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.3

Pressure and viscous drags acting on a bubble rising in a viscous fluid are numerically estimated to obtain the corresponding drag coefficients that are rarely reported in the existing papers. The numerical method has been successfully validated by solving the existing benchmark problems of a bubble rising in a quiescent liquid at various flow regimes. For spherical cap bubbles, the formula of total drag coefficient is proposed in a similar form to that by viscous potential flow theory expressed by the Reynolds number, and the corresponding formulas for pressure and viscous drag coefficients are derived. Furthermore, the effect of the density ratio of a bubble and the surrounding liquid on terminal velocity is also investigated for fixed Morton and Eotvos numbers: the lighter bubble has a higher terminal velocity having an asymptotic value as the density ratio increases although the Reynolds numbers based on the terminal velocity are nearly constant.

이젝터를 이용한 효율적인 공기방울 장벽 형성에 관한 연구

서현덕(Hyeon Deok Seo),Aliyu M. Aliyu,김경천(Kyung Chun Kim) 대한기계학회 2016 대한기계학회 춘추학술대회 Vol.2016 No.12

Bubble velocity and diameter in the water tank were experimentally studied with using a high-speed camera. Experiment was implemented with 3 cases, no ejector, two different configurations of ejector with 0 and 1.5 D (mixing section diameter) gaps between the nozzle exit and the ejector neck. Images were handled with MATLAB Image Processing tools and statistical methods. Bubble properties were analyzed with respect to the range of Reynolds number. At low Reynolds number case, the ejector acts as an obstacle. In the case of high Reynolds number larger than 21,100, the zero gap ejector shows the potential to produce smaller bubbles than the ‘no ejector’ case.

유동층에서 기포의 유동특성에 관한 연구

김용섭(Yong Sup Kim) 한국해양공학회 1996 韓國海洋工學會誌 Vol.10 No.3

A fluidized bed combustion chamber is widely used to incinerate waste material. The most important factor designing the incinerator is the flow characteristics in a fluidized bed, because combustion efficiency is influenced by the flow characteristics. This paper has invesitigated the flow characteristics of bubbles in fluidized bed by means of meassuring a pressure fluctuation in the fluidized bed. A pressure probe system has used to measure the pressure.<br/> The data concerned with bubble rising velocity, bubble size, distribution of bubbles and frequency of bubble generation or decay are obtained to find the flow characteristics of bubbles in the fluidized bed. The result obtained from this experimental study can be used to design the fuel feeding system of fluidized bed combustion type incinerator. And it is possible to predict the mixing of waste material and fluidizing material.