• Journal of environmental and Sanitary engineering
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• v.13 no.1
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• pp.1-8
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• 1998

Musty-odorous compound (Geosmin, 2-Methylisobrneol) 수용액 중에 초음파 (200kHz, $6.0W/cm^{2}$)를 조사시켜 조사시간에 따른 농도 및 취기의 변화를 고찰했다. 초음파 조사에 의해 이 물질들은 빠르게 분해되었고 분해 형태는 농도에 대한 유사1차 반응을 나타내었다. 공기 포화 분위기에서 이들의 초기 분해속도는 각각 2.5 $10^{-3}{\;}Msec^{-1}$(2-MIB), 3.2 $10^{-3}{\;}Msec^{-1}$ (Geosmin)로 나타났다. 초음파 조사 시 포화가스 (Envelope gas)의 영향은 아르곤(Ar) 산소($O_{2}$) 공기(Air) 질소($N_{2}$) 순서로 순수한 아르곤(Ar) 분위기에서 musty-odorous compound 류의 분해가 가장 빠르게 진행되었고 그 분해생성물로 CO, $CO_{2}$ 그리고 HCOOH, $CH_{3}COOH$ 등의 저급 유기산류가 검출되었다. 또한 이들의 분해반응은 물의 초음파분해에 따라 생성된 hydroxylradical에 의한 radical반응, cavitation bubble내에서의 고온고압에 의한 열분해 및 직접연소반응으로 진행됨을 알 수 있었다.

• Journal of the Society of Naval Architects of Korea
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• v.42 no.3
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• pp.183-189
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• 2005

A modeling of a hydraulic-gun-aerator is proposed to set up a design procedure for such devices. The aerators are used to destroy any thermal stratification that are responsible for the degradation of water qualify of lakes. The aerator produces ascending flow by using air bubbies released instantly near the bottom of the lake into a cylindrical pipe installed vertically. Differently form the diffuser-aerators, they can pull up the cold, oxygen depleted water directly to the region of the free surface, and they are believed to work effectively especially for relatively deeper lakes. Their design procedure has not been established yet though, and we propose a model focusing on the exit flow velocity at the top of the aerator through the examination of presently operating devices.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2001.05a
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• pp.249-257
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• 2001

This study was experimentally performed to investigate sea water freezing behavior along parallel cooled plate with bubbly flow. The experiments were carried out for a variety of parameter, such as sea water velocity, air-bubble flow rate, and cooled-plate temperature. The shape of freezing layer, freezing rate and salinity of frozen layer were observed and measured. It was found that the experimental parameters gave a great influence on the freezing rate and the salinity of the frozen layer.

• Journal of Institute of Control, Robotics and Systems
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• v.6 no.1
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• pp.112-119
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• 2000

A die-casting junction method is usually used to manufacture the tub of an IH(induction heating) jar. If there is a very small air bubble in the junction area, the thermal conductivity is deteriorated and local overheat occurs. Such problem brings serious inferiority of the IH jar. In this paper, we propose a new method to detect such defect with simply measured thermal data. Thermal distribution of preheated tubs is obtained by scanning with infrared thermal sensors and analyzed with the statistic pattern recognition method. By defining the characteristic feature as the temperature difference between sensors and using ellipsoid function as decision boundary, a supervised learning method of genetic algorithm is proposed to obtain the required parpameters. After applying the proposed method to experiment, we have proved that the rate of recognition is high even for a small number of data set.

• Journal of the Korean Society of Marine Environment & Safety
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• v.4 no.1
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• pp.49-56
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• 1998

The Microfiltration and Ultrafiltration were used to treat effluent of secondary municipal wastewater treatment system(Sequencing Batch Reactor). The cross-flow hollow fiber, UF 500,000(NMWC) and MF 0.65$\mu$ membrane were selected as suitable membrane. Short term and long term fouling effect were measured as a factor of flux decrease and the fouling removal effect of mixing air bubble in the penetrant was studied. The removal of anionic sulfactants before and after formation of micelle with several kinds of oil were checked. The test results show that removal of TOC was 70~80%, TN 28% and TP 16%. The decrease of flux due to fouling were 85%(UF) and 90%(MF) after running of 100hrs. The removal of anionic sulfactants were 60~70% notwithstanding micelle or not.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.06a
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• pp.201-211
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• 2001

The influence of aerated oil on high-speed journal bearing is examined by classical thermohydrodynamic lubrication theory coupled with analytical models for viscosity and density of aerated oil in fluid-film bearing. Convection to the walls, mixing with supply oil and re-circulating oil, and some degree of journal misalignment are considered. The considered Parameters for the study of bubbly lubrication are oil aeration level, air bubble size, shaft misalignment and shaft speed. The results show that deliberate oil aeration can more clearly bring on the increasing load capacity under high-speed operation of plain journal hearing than previous normal speed operation. And the load capacity may be increased more by oil aeration under the conditions of shaft misalignment and the increasing speed.

• Journal of Advanced Marine Engineering and Technology
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• v.29 no.4
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• pp.377-383
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• 2005

This paper deals with the flow characteristics of air-water two-phase flow in a vertical tube of 10mm I.D. and 600mm in length at an adiabatic condition. The obtained experimental data were covered with the liquid superficial velocity ranging from 0.095m/s to 2.56m/s. and the gas superficial velocity ranging from 0.032m/s to 21.08m/s. The effects of the gas and liquid superficial velocity on the flow pattern transitions, frictional pressure drop, and film thickness and gas-liquid interface roughness were also examined. It was found that the film thickness increased and the liquid film wave length was more longer with the liquid superficial velocity $j_L$ increasing at $j_G$ constant. It was also showed that the frictional pressure drops were experienced in three regions. namely increasing region(bubbly flow), decreasing region (Taylor bubble and slug flows) and re-increasing region (annular flow).

• Journal of Advanced Marine Engineering and Technology
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• v.25 no.4
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• pp.825-832
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• 2001

This study was experimentally performed to investigate freezing behavior of sea water along horizontal cooled a circular tube with bubbly flow. The experiments were carried out for a variety of parameter, such as sea water velocity, air-bubble flow rate, and cooled-tube temperature. The shape of freezing layer, freezing rate and salinity of frozen layer were observed and measured. And the flow patterns around cooled tube were visualized using the PIV to analyze the relationship between the flow structure and the freezing characteristics. It was found that the experimental parameters gave a great influence on the freezing rate and the salinity of the frozen layer.

• Journal of Korean Society of Water and Wastewater
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• v.19 no.3
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• pp.295-300
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• 2005

The performances of electroflotation (EF) on the thickening of activated sludge were investigated using laboratory scale batch flotation reactors. Four activated sludges including bulking sludges were tested. After 30minutes of EF operation, 57-84 % of sludge volume reduction could be achieved by EF, while only about 1.5-14% could be obtained by gravity thickening for the same period. After thickening the effluent water quality in terms of TCOD, SS, and turbidity was improved by EF operation for all sludge samples. It is induced that the air bubbles entrapped in the thickened sludge play a key role in the observed improvement of sludge thickening and effluent quality.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.9
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• pp.948-954
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• 2008

Membrane bioreactor(MBR) processes have been widely applied to wastewater treatment for last decades due to its excellent capability of solid-liquid separation. However, membrane fouling was considered as a limiting factor in wide application of the MBR process. Excess aeration into membrane surface is a common way to control membrane fouling in most MBR. However, the excessively supplied air is easily dissipated in the reactor, which results in consuming energy and thus, it should be modified for effective control of membrane fouling. In this study, cylindrical tube was introduced to MBR in order to use the supplied air effectively. Membrane fibers were immersed into the cylindrical tube. This makes the supplied air non-dissipated in the reactor so that membrane fouling could be controlled economically. Two different air supplying method was employed and compared each other; nozzle and porous diffuser which were located just beneath the membrane module. Transmembrane pressure(TMP) was monitored as a function of airflow rate, flux, and ratio of the tube area and cross-sectioned area of membrane fibers(A$_m$/A$_t$). Flow rate of air and liquid was regulated to obtain slug flow in the cylindrical tube. With the same flow of air supply, nozzle was more effective for controlling membrane fouling than porous diffuser. Accumulation of sludge was observed in the tube with the nozzle, if the air was not suppled sufficiently. Reduction of membrane fouling was dependent upon the ratio, A$_m$/A$_t$. For diffuser, membrane fouling was minimized when A$_m$/A$_t$ was 0.27, but 0.55 for nozzle.