• 한국전산유체공학회지
• /
• 제9권2호
• /
• pp.11-17
• /
• 2004

CFD analysis was performed to figure out flow behavior in the inlet plenum of new research reactor where coolant is injected to the flow tubes with the fuel assembly. The computation results showed that large-scale vortices are generated in the inlet plenum by flow stream injected from inlet pipe. These vortices are divided into small vortices and reversed their revolution. They may lead to flow-induced vibration of fuel assembly, moreover, which has been regarded as a cause of fretting wear of fuel assembly. Also there is an another important thing that average velocity of each flow-tube is uneven showing difference in maximum 18%. So it has been suggested that perforated baffle will be installed to prevent the formation of vortex in the inlet plenum. Two perforated baffles, one is flow skirt and the other is muffler type flow straightener, were proposed and their effect was evaluated using commercial CFD code, Fluent. According to CFD analysis for two perforated baffles, it was confirmed that both of them can prevent or reduce vortex formation in the inlet plenum and make average velocity of each flow tube more even.

• 한국산학기술학회논문지
• /
• 제17권6호
• /
• pp.721-728
• /
• 2016

지구상에 존재하는 물의 97%는 해수로 존재한다. 따라서 해양자원을 어떻게 활용하는 가는 최근 가장 중요한 이슈 중 하나이다. 해수의 이용은 해수담수화, 원자력 발전소의 냉각수, 해양심층수 활용 등 다양한 분야로 확대되고 있다. 깨끗한 해수를 취수하기 위해 여과사를 이용한 해수취수시스템이 활발하게 사용되고 있으며 이러한 시스템에 적용되는 취수관의 경우 각 취수구 별로 균등하게 취수될 때 취수효율뿐만 아니라 여과의 효율도 높일 수 있다. 본 연구에서는 해수취수시설에 적용된 2중관 구조의 취수효율 향상 효과를 3차원 수치모의를 통해 확인하였으며 상부유공의 간격변화에 따른 구간별 취수량을 분석하였다. 그 결과 관 말단부로 갈수록 상부유공의 간격이 감소되는 경우가 전체적인 취수량은 큰 차이가 없었으나 상부유공을 통한 취수량의 구간별 표준편차가 최소로 나타났다. 또한 이 경우에 관내 흐름이 안정적이어서 취수의 효율도 향상되는 것으로 나타났다. 추후 본 연구의 결과를 바탕으로 다양한 조건 및 영향인자에 대한 민감도 분석이 수행된다면 개별 환경에 적합한 최적설계안을 도출하는데 활용될 수 있을 것이라고 생각한다.

• 한국안전학회지
• /
• 제12권4호
• /
• pp.191-200
• /
• 1997

This paper discusses prediction of the sound pressure level produced by simple engine exhaust systems(plain pipe, plain expansion chamber pipe, plain expansion chamber with internally extended inlet and outlet pipe, perforated pipe enclosed in a plain expansion chamber) and a computer program has been developed which predicts the sound pressure level and the frequency spectrum. The program utilizes unsteady flow gas dynamic theory and acoustic theory to predict the pressure-time history in the exhaust system and the mass flow rate-time history at the open end of the system and the sound pressure levels(1/3 Octave band levels) and the frequency spectrum in semi-anechoic room. The predictions are compared with measured levels and show a high degree of correlation.

• 대한설비공학회:학술대회논문집
• /
• 대한설비공학회 2003년도 하계학술대회 논문집
• /
• pp.201-201
• /
• 2003

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2008년도 추계 학술발표회 제20권2호
• /
• pp.77-80
• /
• 2008

본 연구에서는 현행 설계기준상의 강관말뚝머리 연결부의 결합방법이 갖고 있는 철근 배근 및 정착길이 확보, 전단키 용접 등의 문제점을 개선하기 위해 퍼포본드 전단연결재(Perforated Rib Shear Connector)를 활용한 강관말뚝머리 보강방법을 고안하고 이에 대한 압발저항성능을 실험적으로 검증하였다. 그 결과 퍼포본드를 활용한 보강방법은 연직하중에 대해 기존 방법을 대체할만한 동등 수준이상의 구조 안전성은 물론 시공성 및 경제성 측면에서도 우수한 성능을 갖는 구조 시스템인 것으로 나타남에 따라 상부구조의 작용하중을 강관말뚝으로 전달하기 위한 효율적인 강관말뚝머리 연결부 보강방법의 하나로 자리매김할 것으로 사료된다.

• 한국자동차공학회논문집
• /
• 제21권5호
• /
• pp.59-66
• /
• 2013

Lack of the space in many diesel vehicles make it difficult to design and install the catalytic muffler to reduce emissions. For this reason, inlet part of the catalytic muffler is made of L-type which has lower flow uniformity than conventional I-type, and catalytic muffler has complex internal structure by various insertions, which affect the flow uniformity and pressure drop of the systems. In this work, the flow characteristics such as flow uniformity and pressure drop have been numerically investigated by changing such various geometries as inlet shape, porosity, and outlet shape inside the muffler with the three-dimensional turbulent incompressible flow solver. Total 4 different cases are considered in order to find optimal configurations of the catalytic muffler in view of high flow uniformity and low pressure drop. The results show that Case 2 which has no induction cone and outlet perforated pipe has higher uniformity index and lower pressure drop than others considered in this work.

• Journal of Korean Society for Atmospheric Environment
• /
• 제15권E호
• /
• pp.17-28
• /
• 1999

Gas-liquid contact tests above a perforated-plate were conducted with air and water at flooding gas-flow conditions in order to study two-phase flow characteristics in a limestone-gypsum SO2 absorber. Gas layers were in the form of air pockets and confined to the limited areas around each duct pipe, while the remaining tary area were in the wet condition. The liquid above the tray was always in the flooded and even fluidized conditions at gas flows over the range studied, although vigorous bubbly or churn-turbulent two-phase regime was only observed in the immediate vicinity of the gas hole exit at low gas loads. The froth zone was extremely active to provide intimate contact between gas and liquid so that the necessary mass transfer operation can take place, which is the primary purpose of high-performance SO2 absorbers. Howefer, the absorber $\Delta$P was 250mmH2O for the initial water level at 150mm, which is an important issue to be resolved for economical operation of the SO2 absorber. It was seen in the liquid level-and gas flow-transient tests that changes in the absorber liquid inventory were much more pronounced for intimate gas-liquid contact than changes in the gas flow. Based on the 4- and 8-duct pipe test results, grouping the duct pipes near the center of the test tray seemed to promote better recirulation of liquid from gas-liquid contact zone back to the reaction tank so that the absorbed SO2 can be neutralized.

• 한국농공학회지
• /
• 제37권5호
• /
• pp.53-61
• /
• 1995

Analyses of subsurface drainage effects of farmland with respect to pipe and envelop material are made by the laboratory experiments using soil box to give basic information for the subsurface drainage system planning and design. Three different diameter PVC perforated pipes and a mesh pipe are used with envelop materials such as sand, rice bran, and crushed stone. Steady state subsurface drainage flow rate increased as envelop material changed from sand to rice bran and crushed stone. This indicates that as the hydraulic conductivity of the envelop material increases, the drainage flow rate increases. On the other hand, for a given envelop material, the mesh pipe which has the largest openning area shows the largest flow rate while small diameter PVC pipes show small flow rates. This tells that as the openning area and pipe diameter increase, the flow rate increases, too. Therefore, selection of pipe and envelop material should be made in accordance with the design drainage flow rate. Unsteady state subsurface drainage flow rate with respect to time differs for different envelop material. In case the sand was used as an envelop material, the small diameter PVC pipes show larger flow rates than the large diameter PVC pipe and mesh pipe. When the rice bran was used, the mesh pipe shows the largest flow rate, while small diameter pipes show smaller flow rates. In case the crushed stone was used as an envelop material, the large diameter PVC pipe and mesh pipe show larger flow rates, while small diameter pipes show a little bit smaller flow rates. However, the variation of flow rates among different pipes is the smallest when the crushed stone is used. The flow rate curve with respect to the pipe changes little for the crushed stone envelop which has a large hydraulic conductivity, while that changes much for the sand and rice bran envelops. However, it is difficult to draw a consistent relationship between the drainage flow rate and pipe for all the envelop materials. Since the subsurface drainage experiments are made only under the restricted laboratory condition in this study, further study including field experiment is required.

• Journal of Advanced Marine Engineering and Technology
• /
• 제24권5호
• /
• pp.42-51
• /
• 2000

The performances of the simple expansion, perforated tube, and conical-connector type as an exhaust muffler are shown in this study. Applying a model in which the method of four-pole parameter is used makes theoretical estimation of the insertion loss. Experiment is performed for the measurement of the insertion loss under four cases according to the variation of the tail pipe length. By comparing the theoretical prediction with the experimental results, the validity of the modeling using the method of four-pole parameter is verified. The personal computer simulation programs for the above mentioned theory on the muffler design have been developed and exhaust sound level measurements have been carried out for simple expansion muffler, conical-connector muffler, perforated tube mufflers and the combined type of conical-connector and simple expansion muffler. The measured results for attenuation characteristics of noise for each muffler are compared with the computed theoretical results to verity the confidence and applicable limits of the theoretical equation derived.

• 대한토목학회논문집
• /
• 제29권6A호
• /
• pp.661-669
• /
• 2009

강 콘크리트 합성구조에서 강재와 콘크리트 사이의 경계면에 효과적인 응력전달과 합성거동을 유도하기 위하여 스터드, 채널, 유공강판 등이 사용된다. 많은 연구자들이 여러 종류의 전단연결재의 특성을 개선시키기 위해 많은 노력을 기울이고 있다. 본 연구에서는 확대기초와 말뚝과의 합성을 위해 개방형 퍼포본드로 보강된 강관 말뚝머리의 인발 및 압발거동을 분석하였다. 다양한 변수해석에서 요구되는 자료를 제공하고자 비선형 유한요소해석 프로그램인 ABAQUS를 사용하여 매개변수 해석을 수행하였다.