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과냉유동비등 상황에서의 직사각형 채널의 비등시작점에 대한 실험적 연구
임지환(Ji Hwan Lim),이수원(Su Won Lee),오훈교(Hoongyo Oh),박민규(Minkyu Park),황돈관(Donkoan Hwang),김무환(Moo Hwan Kim),조항진(HangJin Jo) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11
The cooling system of a fusion power plant is safe to operate in single-phase to avoid flow instability due to vapour or reaching a potential critical heat flux. However, there are very few cases of experimental evaluation of onset of nucleate boiling (ONB) under one-side high heat load conditions inside the tokamak. Therefore, ONB of a rectangular channel was evaluated under one-side heating condition. As a result of analyzing the effect of system parameters on ONB heat flux, it was confirmed that ONB heat flux had a proportional relationship with flow and sub-cooling, and an inverse relationship with pressure. In addition, as a result of evaluating various types of ONB correlations, it was difficult to find correlations that predict ONB with high accuracy under one-side high heat load conditions. This proves that it is essential to develop a new ONB correlation for application to the tokamak cooling system.
높은 과냉각 유동비등 조건에서 Hypervapotron 히트싱크의 열전달 성능예측 연구
임지환(Ji Hwan Lim),이수원(Su Won Lee),오훈교(Hoongyo Oh),박민규(Minkyu Park),황돈관(Donkoan Hwang),김무환(Moo Hwan Kim),조항진(HangJin Jo) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11
Because the Hypervapotron (HV) heat sink is used to cool a large area of the tokamak, it is very important to predict the heat transfer performance of the HV heat sink in predicting the thermal efficiency of the fusion power generation system. Therefore, in this study, the heat transfer performance of the HV heatsink in three flow regimes was experimentally evaluated. The effect of system parameters on heat transfer performance under sub-cooled flow conditions was evaluated, and the analysis was focused on changes in heat transfer mechanism. In addition, the existing sub-cooled flow boiling heat transfer correlations were evaluated for each regime. However, most of the correlations were under-predicted because the secondary flow due to the fin structure of the HV heatsink improved the heat transfer performance. These evaluation results show that research on the development of heat transfer correlation of HV heat sinks is essential as future work.
Twisted tape이 삽입된 원형관 튜브의 과냉유동비등 조건 아래에서 비등 시작점 열속에 대한 탐구
임지환(Ji Hwan Lim),이수원(Su Won Lee),오훈교(Hoongyo Oh),박민규(Minkyu Park),이석용(SeockYong Lee),김무환(Moo Hwan Kim),조항진(HangJin Jo) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11
Since the diverter inside the fusion tokamak is loaded with an ultra-high heat flux of up to 20 MW/㎡, twisted tape is inserted into the cooling channel to increase the critical heat flux and heat transfer performance. However, studies on the onset of nucleate boiling (ONB) of the swirl tube in the sub-cooled flow boiling conditions are very scarce. Therefore, in this study, the ONB of the swirl tube was experimentally investigated under the conditions of a pressure of 1-10 bar, a mass flux of 1,000-3,000 kg/m2s, and a bulk inlet temperature of 40-140℃. In addition, the effect of system parameters (pressure, sub-cooling, mass flux) on ONB heat flux was analyzed, and whether the existing ONB correlations predict ONB of swirl tube well under one-side heating condition was evaluated. Unfortunately, they showed a high error rate because the effect of swirl flow caused by twisted tape was not reflected.
DEMO 단계의 토카막 디버터 적용을 위해 단면 고열속 부하조건에서 평가한 flat heak sink의 임계열유속
임지환(Ji Hwan Lim),이수원(Su Won Lee),오훈교(Hoongyo Oh),박민규(Minkyu Park),이용남(Yongnam Lee),김무환(Moo Hwan Kim),조항진(HangJin Jo) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11
In a cooling system operated in a sub-cooled flow condition, the critical heat flux(CHF) is a factor that can threaten system safety. This is because, when CHF is reached, the temperature of the flow path wall rises rapidly. In particular, the heating condition inside the tokamak, where an ultra-high heat flux is loaded as a one-side heating condition, requires CHF data evaluated under the special condition. However, if the circular channel is used under the one-side heating condition, the heat flux is concentrated at the top end of the flow path. Therefore, CHF of a flat heat sink is investigated under the conditions of 1-10bar pressure, 0.105-0.315kg/s flow rate, and 50-140℃ sub-cooling conditions. It was analyzed how the pressure, flow rate, and degree of subcooling affect CHF, and it was evaluated whether the CHF of one-side heated flat heat sink could be predicted through the existing CHF correlations.