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PASCAR-DEMO의 피동 잔열 제거 장치의 타당성 연구
제준호(Junho Je),김무환(Moo Hwan Kim) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5
The PASCAR-DEMO is a pool-type Lead-Bismuth cooled fast reactor, which has a core power of 100㎿, and a reactor vessel auxiliary cooling system(RVACS) is provided to cope with an accident condition like a protected loss of heat sink. The RVACS is a simple, passive decay heat removal system(PDRS) of LFR. In the present study, the performance of the RVACS at a steady state condition are analyzed with the simple 1-demensional model and 3-dimensional computation fluid dynamics(CFD), which is developed for the system analysis of a Lead-Bismuth cooled fast reactor. The simple model results predictions for the heat transfer rate and air mass flow rate were in good agreement with the CFD results.
다공성 매질 개념을 이용한 응축기의 응축 열전달에 관한 수치해석
제준호(Junho Je),최치웅(Chiwoong Choi),김무환(Moohwan Kim) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5
In this study, the numerical analysis to estimate condensation heat and mass transfer of the condenser was carried out using the PMA (porous medium approach). In the PMA, the details of tube bundle in the condenser are replaced by the porous medium, and the flow resistance term is added in the momentum equation. In this regard, the PMA is quite helpful for the study of tube bundle in the large condenser. The pressure loss through tube bundle can be compensated by viscous and inertial momentum sink terms, which was validated numerically. Value of the pressure drop was compared to that of Butterworth correlation. Three dimensional analysis of condensation for McAllister condenser with the PMA was conducted using Fluent 6.2 and UDFs (use-defined functions). The result of condensation rate was analogous to previous results (experimental and numerical data).
응축기의 비응축 가스 배출 타입에 따른 질량 확산율의 영향에 대한 수치적 연구
제준호(Junho Je),최치웅(Chi-woong Choi),김수재(Soo Jea Kim),김무환(Moo Hwan Kim) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11
The numerical study to estimate performance for mass diffusivity effect for non-condensable gases ventilation systems in condensers was carried out using the porous medium approach (PMA). In the PMA, the details of tube bundle in the condenser are considered as the porous medium, and the flow resistance term is added in the momentum equation. In this regard, the PMA is quite helpful for the study of tube bundle in the huge condenser. Three dimensional analysis of condensation for condenser with the PMA was conducted using Fluent and user-defined functions (UDFs). The mass diffusivity effect on condensation was small in internal vent system. However, the mass diffusivity effect was dominant in condensation for external venting system. As the ratio of turbulent viscosity to fluid viscosity was increased, mass fraction of non-condensable gas was decreased. Therefore, total condensation rate was increased for external venting system.
응축기의 비응축 가스 배출 타입에 따른 틈 간격의 영향에 대한 수치적 연구
제준호(Junho Je),최치웅(Chi-woong Choi),김수재(Soo Jea Kim),김무환(Moo Hwan Kim) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5
The numerical study to estimate performance for gap size effect for non-condensable gases ventilation type in condensers was carried out using the porous medium approach (PMA). In the PMA, the details of tube bundle in the condenser are considered as the porous medium, and the flow resistance term is added in the momentum equation. In this regard, the PMA is quite helpful for the study of tube bundle in the huge condenser. Three dimensional analysis of condensation for condenser with the PMA was conducted using Fluent and user-defined functions (UDFs). Gap size effect on condensation was negligible in pure steam condition. However, gap size effect was dominant in condensation with non-condensable gas and external venting. As gap size was decreased, condensation rate was increased for non-condensable gas and external venting system.
X-선 단층 촬영을 이용한 동결과 융해가 기체확산층에 미치는 영향에 대한 실험적 연구
제준호(Junho Je),김종록(Jongrok Kim),도승우(Sungwoo Doh),김무환(Moo Hwan Kim) 대한기계학회 2011 大韓機械學會論文集B Vol.35 No.5
본 논문은 동결과 융해가 고분자 전해질 연료전지 내의 기체확산층에 미치는 영향에 대해 X-선 단층 촬영법을 이용하여 수행한 실험적 연구이다. 고분자 전해질 연료전지는 외부 온도가 0 도 이하가 되면 내부의 물이 동결되며, 외부 온도가 0 도 이상으로 상승하면 다시 녹는 과정을 겪게 된다. 이 과정은 연료전지의 내부 구조에 변형을 야기하고 이로 인해 연료전지의 전력과 수명의 감소를 야기하게 된다. 기체확산층은 연료전지 내부에서 가장 두꺼운 다공성층이며, 이로 인해 가장 많은 변형이 발생된다. 본 연구에서는 포항 방사광 가속기의 X-선 단층 촬영법을 이용하여 물의 동결과 융해 과정이 기체확산층의 내부 구조에 미치는 변화를 관찰하였다. 이 기체확산층의 구조 변화가 고분자 전해질 연료전지의 전력 생산과 수명에 미치는 영향에 관해 논의하였다. We used X-ray tomography to carry out an experimental study to visualize the effect of freeze and thaw cycles on the gas diffusion layer (GDL) in a polymer electrolyte membrane fuel cell (PEMFC). A PEMFC has freeze and thaw cycles if the fuel cell is operating at a below-freezing ambient temperature. The cycle permanently deforms the fuel-cell capillary structures and reduces the ability of the cell to generate electric power and also reduces its service life. The GDL is the thickest capillary layer in the fuel cell, so it experiences the most deformation. The X-ray tomography facility at the Pohang Accelerator Laboratory was used to observe the structural changes in GDLs induced by a freeze and thaw cycle. We discuss the effects of these structural changes on the power production and service life of PEMFCs.
중성자 라디오그래피 방법을 이용한 직접 메탄올 연료전지 공기극의 내부 물 분포 가시화
제준호(Junho Je),도승우(Sungwoo Doh),김태주(TaeJoo Kim),김종록(Jongrok Kim),Xie Xiaofeng,김무환(Moo Hwan Kim) 대한기계학회 2012 大韓機械學會論文集B Vol.36 No.10
본 연구에서는 한국원자력연구원 중성자 영상장치와 중성자 영상법을 이용하여 운전 조건에 따른 DMFC 공기극 내부의 물 및 탄소 분포 변화를 가시화하였다. 운전 중에 연료극에서 발생하는 탄산 가스 때문에 정량적인 물량 계측은 힘들지만, 개회로 결과와 비교했을 때, 상대적으로 탄산가스와 물 분포 변화를 가시화할 수 있었다. 이는 중성자 영상법은 직접 메탄올 연료전지의 공기극 채널 형상 최적화 및 적절한 물 관리에 유용한 정보를 제공할 수 있으며, 이를 바탕으로 성능 향상에 크게 기여할 것으로 예상된다. In this study, the water distribution in the cathode side of a direct methanol fuel cell (DMFC) is visualized using a neutron imaging technique at the Neutron Radiography Facility (NRF), KAERI. It is difficult to quantify the water content in the cathode side because of CO2 gas. A compared open circuit voltage (OCV) image, relative CO2, and water distribution can be visualized by the neutron imaging technique. This means that the neutron imaging technique is useful for the optimization of the flow field design and the establishment of water management, and, in turn, for the improvement of the cell performance.
고든형 열유속 센서의 민감도 관련 인자에 대한 수치 해석적 연구
제준호(Junho Je),김형대(Hyungdae Kim),최치웅(Chiwoong Choi),김무환(Moohwan Kim),강요섭(Yoseob Kang) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.11
The sensitivity of Gardon gage type HFS(heat flux sensor) is affected by some factors that are changeable by fabrication. We investigated effects of parameters on HFS using the numerical analysis. Fluent 6.2 was used for the numerical simulation. The sensitivity and thermal characteristics of the sensor corresponding to four parameters such as constantan foil thickness, copper wire diameter, copper wire position, and coolant velocity were analyzed. The results showed that the change of constantan foil thickness caused a dominant effect on sensitivity of the Gardon gage type HFS, however the others made relatively nominal effects.
X-선 단층 촬영을 이용한 동결과 융해가 공기확산층에 미치는 영향에 대한 실험적 연구
제준호(Junho Je),김종록(Jongrok Kim),도승우(Sungwoo Doh),김무환(Moohwan Kim) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
The experimental study to visualize effect of freeze and thaw cycles on gas diffusion layer(GDL) in a polymer electrolyte membrane fuel cell(PEMFC) was carried out using X-ray tomography. A PEMFC may have freeze and thaw cycles if the fuel cell is operating in ambient temperature below freezing. The cycle permanently deforms the fuel cell capillary structures and reduces both the ability of the cell to generate electric power and its service life. The GDL is the thickest capillary layer in the fuel cell, so the layer experiences the most deformation. In this paper, the X-ray tomography facility at the Pohang Accelerator Laboratory was used to observe structure changes in GDLs induced by this water freeze and thaw cycle. This paper discusses the effects of these structure changes on the power production and service life of PEMFCs.
응축기의 비응축 가스 배출 타입에 따른 틈 간격 비율의 영향에 대한 수치적 연구
제준호(Junho Je),김수재(Soo Jea Kim),최치웅(Chi-woong Choi),김무환(Moo Hwan Kim) 대한기계학회 2012 大韓機械學會論文集B Vol.36 No.1
본 논문은 응축기의 비 응축 가스 배출 타입에 따른 틈 간격의 비율이 응축기의 성능에 미치는 영향에 관하여 다공성 매질 개념을 적용한 수치적 연구에 관한 것이다. 다공성 매질의 개념을 이용한 응축기의 성능 해석에서는 응축기기 내부의 다관군을 다공성 매질로 간주하며, 다관군에 의한 압력강하는 상관식으로 반영한다. 상용수치해석 프로그램인 Fluent 와 user-defined functions 를 이용하여 McAllister 응축기에 다공성 매질 개념을 적용하여 3 차원 응축량을 해석하였다. 순수증기의 해석에서는 틈 간격이 응축량에 미치는 영향이 거의 없었다. 그러나 비 응축가스가 포함되어 있으며, 외부 배출의 경우 틈 간격은 응축량에 매우 큰 영향을 미쳤는데, 틈 간격이 줄어듦에 따라 응축량이 매우 증가하는 결과를 얻었다. A numerical analysis was carried out to estimate the effect of the gap size ratio on the performance of condensers under noncondensable gas ventilation using the porous medium approach (PMA). In the PMA, the details of the tube bundle in the condenser are considered to be those of a porous medium, and the flow resistance term is added in the momentum equation. Three-dimensional analysis of the condensation for a McAllister condenser was conducted with the PMA using Fluent and user-defined functions (UDFs). The gap size effect on the condensation was negligible under pure steam conditions. However, the gap size effect was dominant in condensation with noncondensable gas and external venting. As the gap size decreased, the condensation rate increased for noncondensable gas in an external venting system.