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HVAC 상실사고시 울진원전 3/4호기의 보조급수펌프 격실 온도상승 평가
윤철(Churl Yoon),박진희(Jinhee Park),황미정(Meejeong Hwang),한상훈(Sang Hoon Han) 대한기계학회 2012 大韓機械學會論文集B Vol.36 No.5
난방, 환기 및 공기조절(HVAC) 기능이 상실된 사고의 경우, 보조급수를 위한 모터-구동 펌프 격실의 온도상승을 전산유체역학 분석을 통해 평가하였다. 닫힌 펌프격실의 과도 계산결과, 8 시간 동안 공간-평균된 공기온도는 60℃ 정도의 상승이 예상된다. 외기 온도 및 외부 온도는 이전 계산결과로부터 초기 35℃에서 시작하여 서서히 증가한다고 가정하였다. 격실 문이 사고발생 후 약 2, 4, 그리고 6 시간 경과 시점에서 열릴 경우, 체적-평균 격실 내기 온도는 약 4℃의 즉각적인 하강이 나타나며 이후 서서히 온도가 상승하는 장기 거동을 보인다. 전산유체역학을 적용한 현재의 상세 해석결과는 이전의 집중(lumped) 모델을 사용한 보수적인 계산결과에 비해 낮은 격실온도 상승률을 예측한다. Computational Fluid Dynamics (CFD) analysis has been performed to estimate the air temperature inside an Auxiliary Feed Water (AFW) Motor-Driven (MD) pump room for the case where there is loss of Heating, Ventilation, and Air-Conditioning (HVAC). A transient calculation for the closed pump room without cooling by any HVAC system shows that the volume-averaged air temperature reaches around 60℃ for a transient period of 8.0 h. From previous studies, the external air and surface boundary temperatures are assumed to increase slowly starting from an initial temperature of 35℃. For the cases where the door is opened at 2, 4, and 6 h after the initiation of HVAC failure, the average air temperature promptly drops by about 4℃ when the door is opened and then slowly increases. The current calculations based on the CFD technique predict the rate of increase of air temperature to be lower than that determined by previous conservative calculations on the basis of a lumped model.
대향식 스퍼터링법으로 증착된 ITO 양극 위에 제작된 OLED 성능
윤철(Chul Yoon),김상호(Sang-Ho Kim) 한국표면공학회 2008 한국표면공학회지 Vol.41 No.5
Indium tin oxide (ITO) has been commonly used as an anode for organic light emitting diode (OLED), because of its relatively high work function, high transmittance, and low resistance. The ITO was mostly deposited by capacitive type DC or RF sputtering. In this study we introduced a new facing target sputtering method. On applying this new sputtering method, the effect of fundamental deposition parameters such as substrate heating and post etching were investigated in relation to the resultant I-V-L characteristics of OLED. Three kinds of ITOs deposited at room temperature, at 400℃ and at 400℃ with after surface modification by O₂ plasma etching were compared. The OLED on ITO deposited with substrate heating and followed by etching showed better I-V-L characteristics, which starts to emit light at 4 volts and has luminescence of 65 cd/㎡ at 9 volts. The better I-V-L characteristics were ascribed to the relevant surface roughness with uniform micro-extrusions and to the equi-axed micromorphology of ITO surface.
원자력발전소 핵분열생성물 거동 해석을 위한 에어로졸 관성 침착 모델의 개발과 검증
윤철(Churl Yoon),하광순(Kwang Soon Ha),임홍식(Hong Sik Lim) 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.12
Prediction and estimation of the radioactive fission product release from a NPP (Nuclear Power Plant) to the environment is one of the major concerns in the field of severe accidents. Because a relatively small amount of radioactive fission products(FP) could be released into the environment during the postulated accident conditions, behavior analyses of the fission products circulating in the primary coolant loop and in the containment are major consideration factors for safety evaluation. The multi-component and multi-sectional analysis module of aerosol fission products has been developed based on the MAEROS model(F. Gelbard, 1988), and the aerosol transport model has been developed and verified. Due to the existence of carrier gas flows, aerosol fission products would deposited to the surrounding walls more when the flow goes through a bend. To evaluate this phenomena, an inertial deposition model has been developed based on the VICTORIA 2.0 code. The implemented inertial deposition model was successfully validated against the TRANSAT separated effect tests performed at the Cadarache laboratories in France.
초고온가스로 모사 실험회로 설계를 위한 전산유체역학 해석
윤철(Churl Yoon),홍성덕(Sung Deok Hong),노재만(Jae Man Noh),김용완(Yong Wan Kim),장종화(Jong Hwa Chang) 대한기계학회 2010 大韓機械學會論文集B Vol.34 No.5
한국원자력연구원에서는 초고온가스로를 모사할 수 있는 중형 헬륨 회로를 건설 중에 있다. 이 실험 헬륨 회로에서 두 개의 전기 가열기가 헬륨 유체를 1 ~ 9 ㎫ 의 압력 하에서 950℃ 까지 가열하게 된다. 이 실험 헬륨 회로의 설계 사양을 최적화하기 위하여, 본 연구에서는 두 개의 가열기 중 하류에 위치한 고온 헬륨가열기 안의 복합열전달 현상을 전산유체역학으로 해석하였다. 해석 결과에서 헬륨 가열기 내 최대 온도는 허용 한계를 넘지 않았고, 이로써 선정된 기하구조의 열적 특성은 설계요건을 만족함이 확인되었다. A medium-scale helium loop that can simulate a VHTR (very-high-temperature reactor) is now under construction at the Korea Atomic Energy Research Institute. The heaters of the test helium loop electrically heat helium fluid up to 950℃ at pressures of 1 to 9 ㎫. To optimize the design specifications of the experimental helium loop, the conjugate heat transfer in the high-temperature helium heater was analyzed by performing a CFD simulation. The analysis results indicate that the maximum temperature does not exceed the allowable limit. It is confirmed that the thermal characteristics of the loop with the given geometry satisfy the design requirements.