• 드라이브 ㆍ 컨트롤
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• 제16권1호
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• pp.1-6
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• 2019

The use of micro bubbles in industrial fields has been increasing in the recent years., particularly micro-bubble sterilization and water purification effects. Various methods have been developed for the generation of micro-bubbles. Depending on the method of generating bubbles, the micro-bubbles can be roughly classified into saturation molding, cavitation and rotation flow types. The objective of this study was to use ventilated tube type as a method of generating micro-bubbles in order to purify large amount of water quality such as lakes and reservoirs. This method shows a difference in efficiency in which micro-bubbles are generated depending on the contact ratio of gas to liquid. The study also investigated the optimal gas liquid contact ratio by applying various orifice methods and investigated the optimum condition of micro-bubble generation by gas Based on this, a technology to develop a micro-bubble generator with a venturi type nozzle shape that has a high water purification effect was developed.

• 대한기계학회논문집B
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• 제37권9호
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• pp.847-854
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• 2013

본 연구는 환형 노즐 이젝터를 이용하여 수평방향 폭기공정의 혼합유동 및 산소전달 특성에 대한 실험적 연구를 목표로 한다. 실험변수는 이젝터 피치와 가압수 유량이며, 측정된 유량과 압력을 이용하여 유량비, 수두비 및 효율을 계산하였다. 이적터에서 분출된 혼합유동의 가시화를 통해 정성적 거동을 고찰하였으며, 용존산소량을 측정하여 총괄 산소전달계수를 도출하였다. 이젝터에서 분출된 혼합유동은 가압수의 운동량과 유입된 공기기포의 미립화에 따라 부력분류 또는 수평분류의 거동을 나타내었다. 기포의 크기에 기인하는 부력과 가압수의 운동량에 지배되는 혼합유동의 도달거리는 가압수와 공기기포의 접촉 면적 및 시간에 크게 영향을 미치기 때문에 산소전달률의 중요한 변수임을 유추할 수 있다.

• 한국가시화정보학회지
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• 제19권1호
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• pp.36-42
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• 2021

This study measured the velocity of magnetic particles inside the power generation using external heat sources. Single Plane Illumination Microscopy (SPIM) was used to measure magnetic particles that are simultaneously affected by bubbly flow and magnetic field. It has the advantage of reducing errors due to particle superposition by illuminating the thin light sheet. The hydraulic diameter of the power generation is 3mm. Its surface is covered with a coil with a diameter of 0.3 mm. The average diameter of a magnetic particle is 200nm. The excitation and emission wavelengths are 530 and 650nm, respectively. In order to find out the flow characteristics, a total of four velocity fields were calculated in wide and narrow gap air bubbles, between the wall and the air bubble and just below the air bubble. Magnetic particles showed up to 8.59% velocity reduction in the wide gap between air bubbles due to external magnetic field.

• 한국유체기계학회 논문집
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• 제19권3호
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• pp.10-13
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• 2016

The wet-air oxidation in gravity pressure reactor is effective for organic waste treatment with energy saving under high pressure and high temperature. But its oxidation control is difficulty because its multi-phase flow characteristics is very complicated. The flow characteristics of an oxidizer feed section in the gravity pressure reactor were investigated using numerical method which are verified by comparison with experimental results. In this study, the results showed that the flow rate of oxidizer have an effect on the generation of bubble around feed section.

• 대한기계학회논문집B
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• 제37권9호
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• pp.837-845
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• 2013

공기부양 펌프는 액체 내 공기부양 효과에 의해 양수 조작이 어려운 액체 및 액체 내의 침전물을 손상 없이 토출할 수 있는 장점을 가지고 있다. 이러한 장점을 이용하여 DCFC(Direct Carbon Fuel Cell)에서 고온의 용융된 연료를 혼합 및 순환시키기 위해 공기부양 펌프를 적용할 수 있다. 이를 위한 연구의 일환으로 공기부양 특성을 파악하기 위한 기초 실험을 수행하였다. 본 실험에서는 공기부양 펌프 시스템을 구축하여 저수통 내에 모사 액체로 물을 채우고 관(tube)을 삽입한 후, 관 하단부에 가스유량을 공급하여 상단부의 토출유량을 측정하였다. 설계 인자로서 관직경과 잠수비를 변경하면서 이에 맞는 공기유량을 공급하였고, 정해진 각 조건에서 생성된 관 내부의 기포(bubble) 형상을 디지털 카메라로 촬영, 그 형상을 네 단계로 구분하였다. 펌프의 성능을 이론식을 모델링하여 실험 데이터와 비교하였고, 토출 유량을 측정하여 물이 토출되는 시작점인 가스유량과 전체 유량비와의 상관관계를 분석하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.300-305
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• 2001

The unsteady flow structure and the related noise generation, which are caused by the separation of a two-dimensional, incompressible, laminar boundary-layer on the flat plate under the influence of local adverse pressure gradient, are numerically examined. The characteristic lines of the wall pressure are examined to understand the unsteady behavior of vortex shedding near the reattachment point of the separation bubble. Also, the generation and propagation of the vortex-induced noise in the separated boundary-layer are calculated by the method of computational aero-acoustics (CAA), and the effects of Reynolds number, Mach number and the strength of the adverse pressure gradient on the unsteady flow and noise characteristics are examined.

• 한국유체기계학회 논문집
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• 제2권3호
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• pp.37-44
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• 1999

In a screw-type centrifugal pump, the pump head deteriorates from single-phase flow to the choke due to an increased air entrainment at a wide tip clearance compared to that of a narrow tip clearance. Moreover, at a narrow tip clearance, the pump head became partially higher in a two-phase flow than that of a single-phase flow near the best efficiency point in low void fraction region. Therefore, we observed the internal flow pattern by using a stroboscope and we measured the mean size of bubbles from the images obtained with a high speed camera. Then, we investigated the influences of the mean size of bubbles, tip clearances and flow patterns on pump performance.

• 한국가시화정보학회지
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• 제10권3호
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• pp.37-41
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• 2012

Plate-fin heat exchanger is a kind of compact heat exchangers with a good performance in heat transfer. It is widely used in various engineering fields such as aerospace, chemical and biomedical industries. Quantitative and qualitative flow visualization study were performed using the water model of commercial plate-fin heat exchanger with header angles of $30^{\circ}$. The Reynolds number was 100. Conventional digital particle image velocimetry was used to measure the instantaneous velocity fields of the header region and the flow visualization using dye injection and hydrogen bubble method were applied to capture the qualitative flow characteristics. The results showed the existence of separation flow region at the junction area and the bottom wall of the exit region.

• Journal of Advanced Marine Engineering and Technology
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• 제25권4호
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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.

• 대한환경공학회지
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• 제35권12호
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• pp.929-936
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• 2013

DAF (Dissolved air flotation) 공정에서 공기포화장치(Saturator)와 미세기포 발생노즐은 미세기포 형성에 중요한 영향을 미치는 장치이다. 미세기포 발생 효율을 증가시키기 위해서는 공기포화장치 용기 안에서 기-액 접촉 효율을 증가시키고, 미세기포 발생노즐까지 이송 배관 내 압력을 일정하게 유지해 주어야 한다. 본 연구에서는 공기포화장치 내 순환수 유입 분사노즐과 포화수 이송 배관, 미세기포 발생노즐에 의한 미세기포 발생에 미치는 영향을 공기체적법과 기포 크기, 기포의 잔류시간 측정을 통해 비교해 보았다. 순환수 유입 분사노즐을 설치하고, 포화수의 이송 배관 내 압력손실이 발생하지 않는 구조, 미세기포 발생노즐의 통과유속을 증가시킬 경우 미세기포 발생 성능이 증가하였다.