• 한국산학기술학회논문지
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• 제16권2호
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• pp.1571-1578
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• 2015

전산유체역학(CFD)을 이용하여 산업체에 널리 적용되고 있는 충격기류형 탈진시스템의 탈진 특성을 규명하고, 그 성능을 향상시키기 위해 탈진부 유니트(unit) 형상을 개조한 경우의 탈진 성능을 비교하였다. 탈진부 각 형상에 대해 검토한 결과, 블로우 튜브에 노즐을 설치한 경우(Case 3)와 벤츄리에 이중 유입관을 설치한 경우(Case4, 5)가 현재 현장에서 널리 적용되고 있는 구조(Case 1)에 비해 우수한 것으로 예측되었다. 또한 최적 형상의 벤츄리를 설계하고, 이 벤츄리를 pilot plant에서 실험하여 현장 적용성을 분석하였다. 블로우 튜브와 본 연구에서 제안한 벤츄리를 조합한 시스템의 경우, 기존 시스템(블로 튜브만 사용한 경우와 블로 튜브와 벤츄리를 조합한 경우)에 비해 탈진 기류를 집중시키는데 매우 효과적인 것으로 나타났다. 또한 본 연구에서 제안한 벤츄리를 장착하여 테스트한 결과, 산업 현장에서 사용 중인 상용 벤츄리를 사용한 경우 보다 탈진횟수 및 탈진시간이 많이 향상되는 결과를 보였다.

• 소성∙가공
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• 제32권6호
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• pp.311-320
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• 2023

Recently, lightweight of automotive parts has been required to solve environmental problems caused by global warming. Accordingly, research and development are proceeded on manufacturing of parts using aluminum that can replace steel for lightweight of the automotive parts. In addition, high strength aluminum can be applied to body parts in order to meet both requirements of lightening and improving crash safety of vehicle. In this study, hot blow forming of roof side rail is employed to manufacturing of the automotive parts with high strength aluminum tube. In hot blow forming, longer forming times and excessive thinning can be occurred as compared with conventional manufacturing processes. So optimization of process conditions is required to prevent excessive thinning and to uniformize thickness distribution with fast forming time. Mechanical properties of high strength aluminum are obtained from tensile test at high temperature. These properties are used for finite element(FE) analysis to investigate the effect of strain rate on thinning and thickness distribution. Variation of thickness was firstly investigated from the result of FE analysis according to tube diameter, where the shapes at cross section of roof side rail are compared with allowable dimensional tolerance. Effective tube diameter is determined when fracture and wrinkle are not occurred during hot blow forming. Also FE analysis with various pressure-time profiles is performed to investigate the their effects on thinning and thickness distribution which is quantitatively verified with thinning factor. As a results, optimal process conditions can be determined for the manufacturing of roof side rail using high strength aluminum.

• International Journal of Automotive Technology
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• 제8권2호
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• pp.219-224
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• 2007

Recently, atmospheric contaminations has become worse due to the increased number of automobile. The PCV (Positive Crankcase Ventilation) valve acts as a flow control to allow re-combustion of blow-by gas by having it flow from a crankcase to an inlet manifold suction tube. Also, during the fabrication of the PCV valve, micro cracks may occur in the valve body and be extended under operation. The excessive stress distribution and crack initiation on the PCV valve body would bring an unstable blow-by gas flow rate control and would cause valve failure. The purpose of this study is to examine the crack affects on the stress and strain variations on the PCV valve according to the inlet and outlet manifold under differential pressures. From the results, we can explain the behavior of the crack extension for a safe condition of PCV valve.

• 사물인터넷융복합논문지
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• 제5권1호
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• pp.29-34
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• 2019

백필터 집진기는 여러개 또는 수십개의 여과포를 구성하여 미세먼지를 정화시켜 깨끗한 공기를 대기에 방출시키는 일종의 공기청정기이다. 백필터 길이가 5m 이하인 경우 다이아프램 밸브에서 발생되는 압축공기를 벤추리를 통과시키는 것만으로도 백필터에 부착된 분진 및 흄을 효율적으로 탈진 할 수 있었다. 7m 이상의 롱백 탈진에 만족스러운 결과를 얻기 위해서는 더욱 효율이 높고 경제성 있는 인젝터 개발이 시급한 실정이다. 기존 국내외 인젝터의 경우 유지 보수시 다수의 블루튜브 해체작업과 인젝터와 블루튜브가 결합되어 중량증가로 인한 작업의 불편성 등 많은 문제를 내포하고 있는 실정이다. 본 연구에서는 코안다 효과를 이용한 최적의 인젝터 개발을 위한 유동해석과 4차 산업의 지능형 자동화 탈진 기술이 접목되어, 기존 설비 대비 에너지 비용저감 및 필터 수명향상 등을 획기적으로 개선시키고자 하는 상용화 연구를 수행하였다.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2006년 추계학술발표대회 개요집
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• pp.38-40
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• 2006

Nuclear power plants are urged to reduce operating and maintaining costs to remain competitive as well as to increase the safety preventing the radioactive material to the atmosphere. To reduce the cost and to increase the safety, the inspection of balance-of-plant heat exchanger becomes important. However, there are some problems for plugging the heat exchanger tubes since the criterion and its basis are not clearly described. The codes and standards related to show the tube plugging criteria may not exist currently. In this paper, a method to establish the tube plugging criteria of BOP heat exchangers is introduced and the tube plugging criteria for the non-regenerative heat exchanger in the steam generator blow-down system of nuclear power plant. This method relies on the similar method used to establish the plugging criteria for the steam generator tubes.

• Archives of Plastic Surgery
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• 제40권4호
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• pp.445-449
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• 2013

Retrobulbar hemorrhage, especially when associated with visual loss, is a rare but significant complication after facial bone reconstruction. In this article, two cases of retrobulbar hematoma after surgical repair of blow-out fracture are reported. In one patient, permanent loss of vision was involved, but with the other patient, we were able to prevent this by performing immediate decompression after definite diagnosis. We present our clinical experience with regard to the treatment process and method for prevention of retrobulbar hematoma using a scalp vein set tube and a negative pressure drainage system.

• 설비공학논문집
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• 제18권2호
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• pp.151-157
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• 2006

The present paper reports the method for evaluation of heat-transfer performance of finned tube heat exchangers in a low Reynolds number regime (Re = $160\~800$) and also reports the data of heat transfer and pressure loss taken from a finned tube heat exchanger with/without vortex generators (VGs) installed as a heat-transfer enhancement device. The evaluation is based on the modified single blow method conducted in a specially designed low Reynolds number duct. Three different test core geometries, i.e., fin only, fin-tube without VGs and that with VGs, are studied here. The data of heat transfer and pressure loss taken from the fin only geometry agree well with the empirical correlations, thus validating the present method as used for low Reynolds number regime. The data taken from the finned tube geometries with and without VGs are presented and compared to examine the effect of VGs in the low Reynolds number regime.

• 한국안전학회지
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• 제20권1호
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• pp.36-41
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• 2005

PCV(Positive Crankcase Ventilation) valve acts as a flow control valve to get a re-combustion of blow-by gas by having it flow from a crankcase to an inlet manifold suction tube. The blow-by gas of the crankcase should be eliminated or taken properly because it cause corrosion to critical parts, and contributes to increase crankcase pressure that can cause a drop in efficiency. The excessive stress and strain on the PCV valve that remove these harmful gas would be bring the difficult on the flow rate control and failure of the valve. Those condition inevitably induce the accident. Therefore, this study purpose is FEM evaluation of the stresses and deformation in the X3 PCV model according to the change of the differential pressure between inlet and outlet. From results, the maximum equivalent stresses increased linearly according to the increase of the differential pressure at the about 50mm from the inlet position and were under the yield strength of the valve. And the deformations were relatively small regardless of the in-outlet differential pressure variation.

• 한국가스학회지
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• 제23권5호
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• pp.24-34
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• 2019

본 연구에서는 수관식 보일러의 열교환기를 모사하기 위하여 수관의 존재 유무에 따른 화염의 안정화와 연소 특성을 당량비와 유속에 따라 비교하였다. 버너는 화염이 존재하는 SiC foam과 역화 방지를 위한 세라믹 보드, 균일한 유동장을 형성하는 알루미나 볼로 구성되며, 반경 반향의 열 손실을 최소화하기 위하여 단열재로 밀폐되어 있다. 결과적으로 수관이 존재하는 경우 낮은 당량비 구간에서 역화 및 날림 현상의 경계가 넓어지는 것을 안정화 영역에서 확인할 수 있었다. 또한, 수관이 존재하는 경우 NOx 배출량이 수관이 없는 경우보다 증가하는 것을 확인하였다. 이는 수관이 존재함으로써 열 손실을 억제하여 화염의 온도가 증가하는 것으로 판단하였으며, O₂ 배출량과 화염의 온도를 예측하여 입증하였다.

• 한국에너지공학회:학술대회논문집
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• 한국에너지공학회 1995년도 춘계학술발표회 초록집
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• pp.185-198
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• 1995

This is an experimental study conducted to visualize the nucleate boiling phenomena and flow regimes occurring inside the liquid pool in a closed two-phase thermosyphon. To meet this purpose, an annular-type thermosyphon was designed and manufactured using a glass tube and a stainless steel tube, being assembled axisymmetrically. The heat to be supplied to the working fluid is generated within a very thin layer of stainless steel tube wall by applying a high frequency electromagnetic field through the induction coil, axisymmetrically set around the evaporator zone. Some important results were as follows ; 1) Considering the structural complexity of the tested thermosyphon, it showed good performance for the range of heat flux 2＜ q" ＜25kW/$m^2$ and saturation vapor pressure, 0.1＜Pv＜1.1bar 2) different type of nucleating boiling regimes were observed as described below, -Pulse boiling regime : Flow pattern changed cyclically with time during 1 cycle of pulse boiling process. The onset of Nucleation was followed by expulsive growing of vapor bubble, resulting in the so called blow-up phenomenon, massive expulsion of large amount of liquid around the bubble. -Transient : Some spherical vapor bobbles were observed growing out from 2~3 nucleating sites, that was dispersed at the lower part of the heated tube wall in the liquid pool. But the rest upper region above the nucleating sites were filled with churns or bubbles of vapor. -Continuous nucleate boiling regime : The whole zone of evaporator was filled with lots of spherical vapor bubbles, and the bubbles showed tendency to decrease in diameter as the heat flux increased.ased.