• Title/Summary/Keyword: 기포생성

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Expansion of a Fire-Ball and Subsequent Shock-Wave Propagation due to Underwater TNT Explosion (해저에서 TNT 폭발에 의한 파이어볼의 팽창과 이에 따른 충격파 전파)

  • Kwak, Ho-Young;Kang, Ki-Moon;Ko, Il-Gon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.35 no.7
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    • pp.677-683
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    • 2011
  • Until now, several empirical models for assessing the damage due to TNT explosions have been proposed. A set of analytical solutions for the time-dependent radius of an expanding fire-ball after detonation of TNT was obtained by solving the continuity, Euler (momentum), and energy equations with a "polytrope" assumption at the fire-ball center. The shock waves developed from the rapid expansion of a fire-ball under water were obtained by using the KirkwoodBBethe hypothesis. The calculated period of bubble oscillation and the maximum radius of the bubble resulting from the fire-ball due to a violent underwater TNT explosion were in good agreement with the experimental data.

Enhancement of Wetting Characteristics for Anisotropic Conductive Adhesive with Low Melting Point Solder via Carboxylic Acid-based Novel Reductants (카르복실산계 환원제를 통한 저융점 솔더입자가 포함된 이방성 전도성 접착제의 젖음 특성 향상 연구)

  • Kim, Hyo-Mi;Kim, Joo-Heon
    • Polymer(Korea)
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    • v.34 no.1
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    • pp.52-57
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    • 2010
  • The low viscous epoxy resin(bisphenol F) with carboxylic acid as the reductants was introduced for high performance and reliability in the ACA with a low melting point alloy filler system. The curing characteristics of the epoxy resin and temperature dependant viscosity characteristic of epoxy resin at the melting temperature of LMPA were investigated by dynamic mode of differential scanning calorimetry (DSC) and rheometer, respectively. Based on these thermo-rheological characteristics of epoxy resin and LMPA, the optimum process system was designed. In order to remove the oxide layer on the surface of LMPA particle, three different types of carboxyl acid-based reductant were added to the epoxy resin. The wetting angles were about $18^{\circ}$ for carboxypropyldisilioxane, and $20.3^{\circ}$ for the carboxy-2-methylethylsiloxane, respectively.

Porous Glass Electroosmotic Pumps Reduced Bubble Generation Using Reversible Redox Solutions (가역적 산화환원반응 용액을 이용하여 기포 발생을 줄인 다공성 유리막 전기삼투 펌프)

  • Kwon, Kil-Sung;Kim, Dae-Joong
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.36 no.7
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    • pp.753-757
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    • 2012
  • This paper presents the performance of a porous glass electroosmotic pump using an iodide/triiodide aqueous solution. The porous glass electroosmotic pump is characterized in terms of the flow rate and voltage. The flow rate and voltage increases linearly with current. A point where the voltage significantly increases is observed owing to an excess in redox capacity. The transition time monotonously decreases with current. The normalized flow rate (flow rate per membrane surface area) is used to compare previous results with results obtained in this study. The normalized flow rate of porous glass frits is three times higher than that of Nafion 117.

A Study on Design and Performance of a Heat pipe for the Application to Solar Collector (태양열 집열기용 열파이프의 구조와 작동 특성에 관한 연구)

  • 임광빈;김철주
    • Journal of Energy Engineering
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    • v.2 no.2
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    • pp.179-186
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    • 1993
  • Heat pipes. applied to a flat plate solar collector, have a long and slender configuration with relatively low heat flux in the evaporator section. Such a heat pipe has a tendency to build-up a liquid pool at the lower part of the evaporator section. and at this pool occurs such complicated phenomena of evaporation and fluid dynamics as superheat, sudden generation of bubble, its likely explosive growth process and flooding, etc. In the present study. we tried to solve these problems by means of adjusting two principal design parameters, the liquid inventory and the installation region of the wick, using 4 heat pipes and 3 thermospheres. The corresponding results can be summarized as follows$\^$1)/. The effective thermal conductances of the heat pipe was greatly improved by eliminating the wick in the adiabatic and condenser sections$\^$2)/. The liquid inventory should be increased by about 40% larger than what is saturated the wick$\^$3)/. In the evaporator section the wick has a favorable effect to reduce both unstable operation by intermittent occurrence of nucleate boiling and response time at the initial start-up process.

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Experimental Study of Performance and Bubble Pattern of Air-Lift Pumps with Various Tube Diameters and Submergence Ratios (공기부양 펌프의 관직경과 잠수비 변화에 따른 기포 형상과 성능에 관한 실험적 연구)

  • Kim, Seung Hwan;Sohn, Chae Hoon;Hwang, Jun Young
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.37 no.9
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    • pp.837-845
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    • 2013
  • An airlift pump can be used to pump liquids and sediments within itself, which cannot easily be pumped up by a conventional method, by using the airlift effect. This characteristic of the airlift pump can be exploited in a DCFC (Direct Carbon Fuel Cell) so that molten fuel with high temperature may be carried or transported. The basic characteristics of airlift are investigated. A simple system is constructed, where the reservoir is filled with water, a tube is inserted, and air is supplied from the bottom of the tube. Then, water is lifted and its flow rate is measured. Bubble patterns in the tube are observed in a range of air flow rates with the parameters of the tube diameter and submergence ratio, leading to four distinct regimes. The pumping performance is predicted, and the correlation between the supplied gas flow rate and the induced flow rate of water is found.

Thends in Membrane Contactors (분리막 접촉기의 기술 동향)

  • Lee Kew-Ho;Kim Min-Joung;Sea Bongkuk;Park You-In;Lee Ki-Sub
    • Membrane Journal
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    • v.15 no.3
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    • pp.187-197
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    • 2005
  • A membrane contactor is a device that achieves liquid/liquid or gas/liquid mass transfer without dispersion of one phase within another. This is accomplished by passing the fluids on opposite sides of a microporous membrane. This approach offers a number of important advantages over conventional dispersed phase contactors, including absence of emulsions, no flooding at high flow rates, no unloading at low flow rates, and high interfacial area. This article provides a general review of membrane contactors, including operating principles and applications.

Experimental Analysis of Bubble Dynamics Induced by Pulsed-Laser Heating of Absorbing Liquid (흡광 액체의 펄스 레이저 가열에 의해 생성된 기포 거동의 실험적 해석)

  • Jang Deok-Suk;Hong Jong-Gan;Choa Sung-Hoon;Kim Dong-Sik
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.30 no.5 s.248
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    • pp.413-421
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    • 2006
  • The bubble dynamics induced by direct laser heating is experimentally analyzed as a first step to assess the technical feasibility of laser-based ink-jet technology. To understand the interaction between laser light and ink, the absorption spectrum is measured for various ink colors and concentrations. The hydrodynamics of laser-generated bubbles is examined by the laser-flash photography. When an Ar ion laser pulse (wavelength 488 nm) with an output power up to 600 mW is incident on the ink solution through a transparent window, a hemispherical bubble with a diameter up to ${\sim}100{\mu}m$ can be formed with a lifetime in a few tens of microsecond depending on the laser power and the focal-spot size. Parametric study has been performed to reveal the effect of laser pulse width, output power, ink concentration, and color on the bubble dynamics. The results show that the bubble generated by a laser pulse is largely similar to that produced by a thin-film heater. Consequently, the present work demonstrates the feasibility of developing a laser-actuated droplet generation mechanism for applications in ink-jet print heads. Furthermore, the results of this work indicate that the droplet generation frequency is likely to be further increased by optimizing the process parameters.

A Non-Invasive Ultrasonic Urinary Bladder Internal Pressure Monitoring Technique: Its Theoretical Foundation and Feasibility Test (비침습적 초음파 방광 내압 측정 기술: 이론적 기초 및 실현 가능성 평가)

  • Choi, Min Joo;Kang, Gwan Suk;Lee, Kang Il
    • Journal of the Korean Society for Nondestructive Testing
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    • v.32 no.5
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    • pp.526-539
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    • 2012
  • A new approach was proposed in this article, named, a non-invasive ultrasonic method to monitor the urinary bladder internal pressure which can resolve the shortcomings of the existing methods. The proposed method makes use of acoustic cavitation. It is based on a physical phenomenon that an extracorporeal high intensity focused ultrasonic pulse generates bubbles inside the urinary bladder and the dynamic properties of the bubbles are related to the urinary bladder internal pressure. The article presents the theoretical foundation for the proposed technique and verifies its feasibility with preliminary experimental data. The suggested ultrasonic urinary bladder internal pressure monitoring method is non-invasive and can be used any time regardless of sex and age, so that it will be of a great benefit to the diagnosis and therapy of urination related diseases.

Experimental Study on the Characteristics of Microbubbles Generated by an Effervescent Tablet in Water (수중 내 발포성 정제로부터 생성된 미세기포 특성에 관한 실험적 연구)

  • Myeong, Jaewon;Maeng, Juyoung;Kim, Young Jun;Cho, Kyungmin;Lee, Woonghee;Kim, Sungho;Park, Youngchul;Sohn, Youngku;Shin, Weon Gyu
    • Journal of the Korean Society of Visualization
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    • v.19 no.3
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    • pp.84-91
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    • 2021
  • Effervescent tablets generate gas bubbles when chemical reaction occurs between water and tablets. Most of previous studies have been focused on pharmaceutical characteristics of tablets. However, for their applications in disinfectants, cleaners, and pesticides, physical characteristics of bubbles released from the effervescent tablets when they are in water are important. In this study, we experimentally investigated the characteristics of microbubbles generated by an effervescent tablet made of sodium bicarbonate and tartaric acid using PDPA and high-speed camera. Microbubbles were generated using different weights of effervescent tablet as well as in different water temperature. The experimental study shows increase in reaction time, bubble concentration and rise velocity as the weight of effervescent tablet increases from 1 to 20 g. The decrease in average bubble diameter was observed when the temperature of water increased from 25 to 45 ℃. Further, reaction time varies inversely with increase in water temperature, while bubble rise velocity is directly proportional to increase in water temperature. Effervescent table continuously generates the bubble with approximately constant diameter (235 ㎛) in the water. However, bubble concentration and bubble rise velocity decreased over time.

Generation of Microcellular Foams in Viscoelastic Polymer Solutions (점탄성 폴리머 용액에서의 초미세 폼의 생성)

  • Kang, Sung- Lin;Kim, Ki-Young;Kwak, Ho-Young
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.28 no.6
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    • pp.726-733
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    • 2004
  • The growth of the critical size bubble by diffusion process in viscoelastic medium was treated by an integral method for the concentration boundary layer adjacent to the bubble wall. In this study, we obtained a set of the first order time dependent equations to obtain bubble radius and gas pressure inside the bubble simultaneously. The calculated final cell sizes depending on the initial saturation pressure are in close agreement with the observed ones. The governing equations developed in this study may be used in polymer processing of microcellular foams.