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윤현기(Hyun Gi Yoon),David E. Stock,유기수(Ki Soo Yoo),정명균(Myung Kyoon Chung) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.10
Diurnal variation of the flow over a forest canopy on a mountain slope is simulated numerically. In the daytime, the earth surface is heated by the solar radiation and the flow goes up the mountain due to the buoyancy force, and during the night, the air is drained downward along the slope owing to the cooling of the surface by radiation. In this flow process the forest canopy that consists of leaf region and the trunk region plays a dominant role as a momentum sink to the flow, thus the modeling of the leaf area region and trunk region is critical to the successful flow simulation. In the present study, a field measurement in an experimental forest in the State of Oregon in the United States is numerically analyzed. The resistance to the flow in the leaf region is directly related to the leaf area density (LAD), and the trunk is modeled as a cylinder.
윤현기(Hyun-Gi Yoon),최원철(Won-Chul Choi),유일수(Il-Soo Yoo) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.10
Blade parts of the Submersible cargo pump consist of inducer, impeller and diffuser. Suction performance of the inducer is important to ensure the safety operation at low NPSHA. A set of 2-bladed inducers are designed in considerations of the cavitation, head raise and outlet flow angle. At here, total head raise through the inducer is determined based on the NPSHR of the impeller. Diffuser of the submersible cargo pump has a geometrical limit due to its operation conditions. In this study, diffuser is designed based on the performance and geometric characteristics of the existed impeller and outline conditions of the cargo pump. And then, on Suction and hydraulic performance of the one set of the cargo pump are simulated numerically to check its design requirement.
평면 충돌제트의 좌굴 현상에 의한 유동장 및 열전달 특징에 대한 수치해석 연구
윤현기(Yoon Hyun Gi),정명균(Chung Myung kyoon) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11
Impinging slot jet is widely used in a variety of industrial fields such as the cooling and coating system. In these systems, flow stability is the most important factor to obtain good products. But, in some cases it was found that there are alternating plane-wise vortices near the impinging stagnation region, and that such alternating vortices move almost periodically to the right and left sides along the stagnation line due to the jet flow instability and the pressure force balance. This instability is closely related to buckling phenomenon of the jet. And, this instability of the flow field causes the non-uniform heat transfer characteristic in the impinging region. In order to verify these flow characteristic, Impinging slot jet system has been investigated numerically by using a commercial 3-D flow analysis code, FLUENT. LES turbulent model is used to obtain instantaneous flow field.
윤현기(Hyun Gi Yoon),서경우(Kyoung Woo Seo) 대한기계학회 2017 대한기계학회 춘추학술대회 Vol.2017 No.11
Open pool type research reactor is widely designed and operated in consideration of the reactor utilization and accessibility. Reactor structure assembly is placed at the pool bottom. Fuel assembly is installed on the grid plate inside a reactor structure assembly. Grid plate is the component of the reactor structure assembly. Primary coolant is dumped into the reactor pool and goes to the fuel assembly through the flow guide structure in the downward flow type research reactor. Heat generated from the fuel assembly is removed by the primary coolant. Grid plate also generates the heat while the reactor is in normal operation. This heat shall be removed to avoid the hot temperature region in the grid plate. Generally, cooling line is designed to remove the heat from the grid plate. In this research, flow path of the primary coolant in the reactor pool is designed to remove the heat from the grid plate. Cooling of the grid plate is numerically simulated by the dumped primary coolant.
페놀류인 4-isopropylphenol의 선택적 분리를 위한 키토산 기반 바이오 소재 제조와 흡력 성능 평가
윤현기 ( Hyun-gi Youn ),김은식 ( Eun-sik Kim ),윤순도 ( Soon-do Yoon ) 한국키틴키토산학회 2018 한국키틴키토산학회지 Vol.23 No.2
The main objectives of this work are to prepare the chitosan(CH)/PVA biomaterials for the selective separation of 4- isopropylphenol (4IPP) as a phenolic. In order to improve the selective separation, CH/PVA biomaterials was also synthesized using benzoic acid (BA) or p-toluic acid (pTA) which have a similar structure with 4IPP as the target material. The CH/PVA biomaterials were prepared by casting method and UV irradiation process. Physical properties such as tensile strength (TS), elongation at break (%E), swelling behavior (SB), and solubility (S) for prepared biomaterials were investigated. The adsorption properties were evaluated by the adsorption kinetics, binding isotherm, Scatchard plot analysis, adsorption of materials with structures similar to target molecules, and selectivity factor (α). The results of the evaluation indicate that the prepared CH/PVA biomaterials have high separation abilities and selectivity.
박용철(Young Chul Park),윤현기(Hyun-Gi Yoon),서경우(Keyoung-Woo Seo),지대영(Dae-Young Chi),윤주현(Ju-Hyeon Yoon) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.10
In nuclear power plant, a reactor cooling system has maintained high-Reynolds-number above 10E+7 to cool a heat generated by the reactor. To simulate flow characteristics of systems or components which are installed in the system, it is necessary a high-Reynolds-number flow simulation system. This paper describes the composition of the high-Reynolds-number flow simulation system and the results of flow network analysis for the system. It was confirmed through the analysis results that the system minimizes flow velocity variation to reduce pressure drop and that the test section maintains a high-Reynolds-number above 10E+07.
Numerical Study of Thermal Stratification in Research Reactor Pool
Yong-Seok Choi(최용석),Hyun-Gi Yoon(윤현기),Kyoung-Woo Seo(서경우) 대한기계학회 2019 대한기계학회 춘추학술대회 Vol.2019 No.11
Formation of thermal stratification in an initially quiescent pool of research reactor is numerically analyzed using a commercial code, ANSYS FLUENT. The thermal stratification is developed in the upper part of the pool by an operation of the Hot Water Layer System in the research reactor. For the numerical schemes, two-equation realizable k-ε model and the simple gradient diffusion hypothesis (SGDH) are used for the treatments of Reynolds stresses and turbulent heat fluxes since the present study is focused on an industrial scale evaluation. The validity of assumptions and numerical methods are discussed with the data measured during the commissioning of the constructed system. As boundary conditions, heat losses on the pool surface and changes of pool water discharge temperature due to heater operation are considered. As results, the development of the hot water layer and the thermal stratification are in good agreements with the measured temperature and flow distribution data in the pool. Although there exists a small deviation between the measurement and the calculation, the present numerical methods seem to predict the measured results acceptably.