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개방형 수조 형태의 연구용 원자로 수조고온층계통에서의 T-형태 유동 분출 배관 설계
윤현기(H.G. Yoon),서경우(K.W. Seo),김성훈(S.H. Kim),지대영(D.Y. Chi) 한국전산유체공학회 2013 한국전산유체공학회 학술대회논문집 Vol.2013 No.5
The Hot Water Layer System(HWLS) maintains the hot water layer, higher than the average temperature of the pool water, at the upper part of the reactor pool so as to minimize the radioactive primary coolant rising up to the pool surface by natural convection in the open pool type research reactor. The ends of the suction and discharge lines of the HWLS are submerged below the pool surface and located at the same level in the reactor pool. The end shape of the discharge pipe is designed as a T-shape diffuser to distribute the flow uniformly for stable hot water layer formation at the upper section of the reactor and service pools. On the other hand, the commercial pipe is used as the end suction line. This pipe line is just extruded into the pool with a short length. In this research, flow fields of the reactor and service pools are numerically simulated with different sizes of the pipes. Heat loss, temperature stratification and velocity boundary layer are taken into consideration to determine the formation of the stable hot water layer through the numerical simulation. Commercial code FLUENT is used to calculate the unsteady pool water flow with different T-shape diffusers and locations of the suction pipe. Inlet and outlet pipe sizes of the HWLS are decided based on the simulation results.
연구용 원자로 수조고온층계통에서의 입구 및 출구 배관 설계
윤현기(H.G. Yoon),서경우(K.W. Seo),박용철(Y.C. Park),지대영(D.Y. Chi) 한국전산유체공학회 2012 한국전산유체공학회 학술대회논문집 Vol.2012 No.5
The Hot Water Layer System(HWLS) maintains the hot water layer, higher than the average temperature of the pool water, at the upper part of the reactor and service pools so as to minimize the radioactive primary coolant rising up to the pool surface by natural convection in the open pool type research reactor. The ends of the suction and discharge lines ore submerged below the pool surface and located at the same level in the reactor pool. The end shape of the discharge pipe is designed as a T-shape diffuser to distribute the flow uniformly for stable hot water layer formation at the upper section of the reactor and service pools. Heat loss, temperature stratification and velocity boundary layer are taken into consideration to determine the formation of the stable hot water layer through the numerical simulation. Commercial code FLUENT is used to calculate the unsteady pool water flow with different T-shape diffusers and locations of the suction pipe. Also, two kinds of turbulent model, RNG k-e and SST k-w turbulent model, are used for the conservative system design.
출혈성 위 정맥류 환자에서 Transjugular Intrahepatic Portosystemic Shunt ( TIPS)의 효과
송희곤 ( H. G. Song ),이한주 ( H. C. Lee ),정세라 ( S. R. Jung ),정영화 ( Y. H. Chung ),이영상 ( Y. S. Lee ),윤현기 ( H. K. Yoon ),성규보 ( K. B. Sung ),서동진 ( D. J. Suh ) 대한소화기학회 2002 대한소화기학회 춘계학술대회 Vol.2002 No.-
<목적> 위 정맥류 출혈은 식도 정맥류 출혈에 비해 심한 출혈로 인해 높은 사망률을 보이고 있고 현재까지 위 정맥류의 이상적인 치료에 대한 공통적인 의견 접근이 없는 실정이다. 이에 출혈성 위정맥류의 초기 치료로서 TIPS의 효과를 살펴보기로 하였다. <방법> 서울중앙병원에서 1998년 1월부터 2001년 3월까지 위 내시경으로 확인된 출혈성 위 정맥류에 대한 치료로 TIPS가 시행된 30예가 포함되었고 이 중 21예(70%)가 응급으로 시행되었다. 모
Zero-Voltage Switching Two-Transformer Full-Bridge PWM Converter With Lossless Diode-Clamp Rectifier
윤현기(H.K. Yoon),한상규(S.K. Han),박진식(J.S. Park),문건우(G.W. Moon),윤명중(M.J. Youn) 전력전자학회 2004 전력전자학술대회 논문집 Vol.- No.-
The two-transformer full bridge (TTFB) PWM converter has two transformers which act as the output inductor as well as the main transformer, i.e. as the forward and the flyback transformer. Although the doubled leakage inductor of the TTFB makes it easier to achieve the zerovoltage switching (ZVS) of the lagging leg switch along the wide load range, it instigates a serious voltage ringing in the secondary rectifier diodes, which would require the dissipative snubber circuit, cause the serious power dissipation, and increase the voltage stress across those diodes. To overcome these problems, a new lossless diode-clamp rectifier (LDCR) is employed as the output rectifier, which helps the voltage across rectifier diodes to be clamped on a half the output voltage (Vo/2) or the output voltage (Vo). Therefore, no dissipative snubber for rectifier diodes is needed and a high efficiency as well as low noise output voltage can be realized. The operations, analysis and design consideration of proposed converter are presented in this paper. To verify the validity of the proposed converter, experimental results from a 425W, 385-170Vdc prototype for the plasma display panel (PDP) sustaining power module (PSPM) are presented.
연구로의 PCS discharge header 설계를 위한 CFD 해석
서경우(K.W. Seo),윤현기(H.G. Yoon),지대영(D.Y. Chi),윤주현(J.H. Yoon) 한국전산유체공학회 2012 한국전산유체공학회 학술대회논문집 Vol.2012 No.5
The heat generated from the core of a research reactor is removed by a primary cooling system (PCS). Most reactors of relatively low power are designed using an open type reactor and pool. Thus, the primary coolant can be discharged to the reactor pool. However, the discharged coolant toward the top of the open type pool should be minimized for operator safety because it contains many kinds of radio-nuclides. This means that it is important for a PCS discharge header to be designed for minimizing bulk flow in the pool. ANSYS-CFD was employed to design a PCS discharge header and to analyze the flow characteristics in the pool. Several discharge headers were simulated with a similar scaled geometry and the boundary conditions of an actual research reactor. To minimize the bulk flow toward the top of the pool, it was analyzed that the magnitude and direction of velocity at the hole of the discharge header should be reduced. The results showed that the CFD analysis can be used as a tool for designing and modifying the PCS discharge according to various types of reactor pools.
서경우(K.W. Seo),윤현기(H.G. Yoon),김성훈(S.H. Kim),지대영(D.Y. Chi),윤주현(J.H. Yoon) 한국전산유체공학회 2013 한국전산유체공학회 학술대회논문집 Vol.2013 No.5
In a research reactor, the large pool water is at the heart of safety because a thermal design flow during a normal operation or a flow path for a natural circulation during an abnormal reactor trip shall be supplied for core cooling. Most research reactors include a reactor in the enormous pool, and are designed using an open type reactor and pool. Thus, the primary coolant containing many kinds of radio-nuclides can be mixed to the reactor pool. Because operators can operate near the pool top during a normal operation, the bulk flow toward the top of the open type pool should be designed to be minimized.
고압용 다이아프램 압축기 및 체크 밸브의 2-way FSI 수치해석
최범석(B.S. Choi),윤현기(H.G. Yoon),유일수(I.S. Yoo),박무룡(M.R. Park) 한국전산유체공학회 2010 한국전산유체공학회 학술대회논문집 Vol.2010 No.5
A metal diaphragm compressor has been widely used for supplying a high pressure gas. This compressor mainly consists of gas, oil space and metal diaphragm. Gas sucked in the gas space is compressed by an oscillating metal diaphragm existed between the gas and oil space. A non-return discharge and suction check-valve are components of the compressor that draw off the compressed oil and gas. Those components are self-actuated by differential pressures. Therefore, the rapid response and stable operating conditions are required. In the present study, to find out the dynamic behavior of the suction, discharge valve and diaphragm compressor, the unsteady flow field has been investigated numerically by using the unsteady two-way FSI (Fluid Structure Interaction) simulation method, k-ω turbulent model and mesh deformation.