• Title, Summary, Keyword: Small Bubble

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Holdup Characteristics of Small Bubbles in a Viscous Slurry Bubble Column (점성슬러리 기포탑에서 작은 기포의 체류량 특성)

  • Jin, Hae-Ryong;Song, Yang-Ho;Kang, Yong;Jung, Heon;Lee, Ho-Tae
    • Korean Chemical Engineering Research
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    • v.49 no.1
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    • pp.83-88
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    • 2011
  • Holdup characteristics of small bubbles were investigated in a viscous slurry bubble column. The phase holdup of small bubbles was obtained from the knowledge of total bubble(gas) holdup and large bubble holdup, which were measured by mean of static pressure drop method and dual resistivity probe method, respectively. Effects of gas velocity, viscosity of continuous liquid phase and solid fraction in the slurry phase on the small bubble holdup as well as holdups of total bubble(gas) and large bubble in a viscous slurry bubble column. The small bubble holdup increased with increasing gas velocity but decreased with increasing liquid viscosity or solid fraction in the slurry phase. In addition the fraction of small bubble in the total bubble(gas) holdup increased with increasing gas velocity but decreased with increasing liquid viscosity or solid fraction in the slurry phase. It was revealed that the rising velocity of large bubble did not related to the holdup of small bubble in a viscous slurry bubble column.

Size Verification of Small and Large Bubbles in a Bubble Column (기포탑에서 작은기포와 큰기포의 크기 구별)

  • Seo, Myung Jae;Jin, Hae-Ryong;Lim, Dae Ho;Lim, Ho;Kang, Yong;Jun, Ki-Won
    • Korean Chemical Engineering Research
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    • v.50 no.2
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    • pp.304-309
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    • 2012
  • Size verification of small and large bubbles in a bubble column was investigated by employing the dynamic gas disengagement (DGD) method and dual electrical resistivity probe (DRP) method, simultancously. The holdups of large and small bubbles in the bubble column in a given operating condition were obtained by means of the DGD method by measuring the pressure drop variation in the column with a variation of time after stopping the gas input into the column. The size and frequency of bubbles were measured by the DRP method in the same operating condition, from which the bubble holdup of each range of size was obtained. The verification of size in determining the large or small bubbles was decided by comparing the holdups of large or small bubbles measured by the DGD method with that measured by the DRP method. Filtered compressed air and tap water were used as a gas and a continuous liquid medium. The diameter and height of the bubble column were 0.102 m and 1.5 m, respectively. The demarcation size between the large and the small bubbles in the bubble column was 4.0~5.0 mm; the demarcation size was about 5.0 mm when the gas velocity was in the relatively low range, but about 4.0 mm when the gas velocity was in the relatively high range, within this experimental conditions.

Analysis of Gas Injection System based on Flow Visualization (가시화를 통한 Gas Injection System에 관한 연구)

  • Seo Dong-pyo;Oh Yool-kwon
    • 한국가시화정보학회:학술대회논문집
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    • pp.85-88
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    • 2002
  • In order to visually analyze the flow characteristics, gas was injected into the liquid bath through nozzle installed at the center of bottom of the bath. 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. Various bubbles, from small bubbles to Taylor bubbles, consisted of the bubble-liquid plumb. 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'.

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Study on Bubble Generation and Size by Dimensionally Stable Anode in Electroflotation Process (전기부상공정에서 촉매성 산화물 전극에 따른 기포 발생량과 크기에 관한 연구)

  • Kim, Dong-Seog;Park, Young-Seek
    • Journal of Environmental Science International
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    • v.16 no.10
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    • pp.1189-1195
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    • 2007
  • Small gas bubbles are used in many environmental and industrial processes for solid-liquid separations or to facilitate heat and mass transfer between phases. This study examines some of the factors that affect the bubble volume and size processed in the EF (electroflotation) process. The effect of electrode material, NaCl dosage, current and electrode distance were studied. The results showed that the generated bubble volume with electrode material lay in: Pt/Ti ${\fallingdotseq}$ Ru/Ti ${\fallingdotseq}$ Ir/Ti > Ti electrode. The more NaCl dosage was high, the smaller bubble was generated due to the low electric power. Bubble generation was increased with increase of current. With the increase of NaCl dosage, bubble generation was increased at same electric power (16.2 W). Generated bubble volume was not affected by electrode distance. However, no clear trends in bubble size as a function of these parameters were evident.

Bubble Behavior and Radiation for Laser-Induced Collapsing Bubble in Water (물 속에서 레이저에 의하여 생성된 기포의 거동 및 복사현상)

  • Karng, Sarng-Woo;Byun, Ki-Taek;Kwak, Ho-Young
    • Proceedings of the KSME Conference
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    • pp.1282-1287
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    • 2004
  • The bubble behavior and the radiation mechanism from a laser-induced collapsing bubble were investigated theoretically using the Keller-Miksis equation for the bubble wall motion and analytical solutions for the vapor inside bubble. The calculated time dependent bubble radius is in good agreement with observed ones. The half-width of the luminescence pulse at the collapse point, which was calculated under assumption that the light emission mechanism is black body radiation from the vapor bubble agreed well with observed value of several nanoseconds. The gas content inside the vapor bubble was too small to produce the light emission due to bremsstrahlung.

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Constitutive Equations for Dilute Bubble Suspensions and Rheological Behavior in Simple Shear and Uniaxial Elongational Flow Fields

  • Seo Dongjin;Youn Jae Ryoun
    • Fibers and Polymers
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    • v.6 no.2
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    • pp.131-138
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    • 2005
  • A theoretical model is proposed in order to investigate rheological behavior of bubble suspension with large deformation. Theoretical constitutive equations for dilute bubble suspensions are derived by applying a deformation theory of ellipsoidal droplet [1] to a phenomenological suspension theory [2]. The rate of deformation tensor within the bubble and the time evolution of interface tensor are predicted by applying the proposed constitutive equations, which have two free fitting parameters. The transient and steady rheological properties of dilute bubble suspensions are studied for several capillary numbers (Ca) under simple shear flow and uniaxial elongational flow fields. The retraction force of the bubble caused by the interfacial tension increases as bubbles undergo deformation. The transient and steady relative viscosity decreases as Ca increases. The normal stress difference (NSD) under the simple shear has the largest value when Ca is around 1 and the ratio Of the first NSD to the second NSD has the value of 3/4 for large Ca but 2 for small Ca. In the uniaxial elongational flow, the elongational viscosity is three times as large as the shear viscosity like the Newtonian fluid.

Analysis of Controlling the Size of Microbubble in DAF (DAF에서 기포의 크기제어 및 영향분석)

  • Dockko, Seok;Kwak, Dong-Heui;Kim, Young-Hwan
    • Journal of Korean Society of Water and Wastewater
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    • v.18 no.2
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    • pp.235-241
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    • 2004
  • The dissolved air flotation (DAF) process has been widely used for removing suspended solids with low density in water. It has been known as measuring the size of microbubbles precisely which move upward rapidly in contact zone is difficult. In this study particle counter monitoring (PCM) method is used to measure the rising microbubble after injection from a nozzle. Size and distribution curve of microbubbles are evaluated at different conditions such as pressure drop at intermediate valve, length of pipeline between saturation tank and nozzle and low pressure. And the efficiency is also checked when it collides with different size floc. The experimental results show the following fact. As the final pressure drop occurred closer to a nozzle, the bubble size became smaller. And small bubble collides with large floc as well as small one because of its physical characteristic. However large bubble collides well with large floc rather than small one since hydrodynamic flow in streamline interferes to collide between two. With performing computational process by mathematical model we have analyzed and verified the size effect between bubble and floc. Collision efficiency is the highest when P/B ratio shows in the range of 0.75 < P/B ratio ($R_{particle/Rbubble}$) < 2.0.

A COMPARATIVE STUDY OF LATTICE BOLTZMANN AND VOLUME OF FLUID METHOD FOR TWO-DIMENSIONAL MULTIPHASE FLOWS

  • Ryu, Seung-Yeob;Ko, Sung-Ho
    • Nuclear Engineering and Technology
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    • v.44 no.6
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    • pp.623-638
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    • 2012
  • The volume of fluid (VOF) model of FLUENT and the lattice Boltzmann method (LBM) are used to simulate two-phase flows. Both methods are validated for static and dynamic bubble test cases and then compared to experimental results. The VOF method does not reduce the spurious currents of the static droplet test and does not satisfy the Laplace law for small droplets at the acceptable level, as compared with the LBM. For single bubble flows, simulations are executed for various Eotvos numbers, Morton numbers and Reynolds numbers, and the results of both methods agree well with the experiments in the case of low Eotvos numbers. For high Eotvos numbers, the VOF results deviated from the experiments. For multiple bubbles, the bubble flow characteristics are related by the wake of the leading bubble. The coaxial and oblique coalescence of the bubbles are simulated successfully and the subsequent results are presented. In conclusion, the LBM performs better than the VOF method.

Flow Characteristics of a Gas-Liquid Slug Flow in Small Vertical Tubes (작은 수직관을 흐르는 기-액 슬러그 유동의 유동특성)

  • Kye, Seok-Hyun;Kim, Dong-Seon
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.25 no.5
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    • pp.246-254
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    • 2013
  • Some characteristics of nitrogen-water slug flow were optically measured, in vertical acrylic tubes of 2, 5 and 8 mm diameter. Bubble velocity, bubble and unit cell lengths were measured, by analyzing the light intensity signals from two sets of dot laser-infrared sensor modules mounted along the transparent tubes. Optical images of the bubbles were also taken and analyzed, to measure bubble shapes and liquid film thickness. It was found that the measured bubble velocities were in good agreement with the empirical models in the literature, except for those measured under high superficial velocity condition in the 2 mm tube. Bubble length was found to be the longest in the 2 mm tube, being 4 to 5 times those of the other tubes. Liquid film was found to have developed early in the 2 mm tube, which made the blunt shape of the bubble head. Liquid film thickness in the 8 mm tube was measured at almost twice those of the other tubes.

Effect of Bubble Size in DAF (DAF에서 기포크기의 영향)

  • Park, Yong-Hyo;Han, Moo-Young
    • Journal of Korean Society of Water and Wastewater
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    • v.17 no.4
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    • pp.528-533
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    • 2003
  • Bubble size is one of the most important parameters affecting DAF (Dissolved-Air-Flotation) process. It is generally known that small bubbles are preferred. However, the fact seems to be based on the particle removal efficiency at contact zone only, without considering separation zone. Besides, the effect of bubble size on the overall DAF process has not been fully investigated yet. Therefore, the effect of bubble size on collision efficiency, collision chances, and surface loading rate is calculated using theoretical models, and the results are discussed in this paper.