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단면 열속부하된 Hypervapotron 냉각채널의 과냉비등상황 임계열유속 실험적 연구
임지환(Ji Hwan Lim),박민규(Min Gyu Park),오훈교(Hun Gyo Oh),황돈관(Don Koan Hwang),김무환(Moo Hwan Kim),조항진(Hang Jin Jo) 대한기계학회 2019 대한기계학회 춘추학술대회 Vol.2019 No.11
In Korea, KSTAR’s tokamak long-time operation technique has reached 70 seconds in 2016, and steady-state plasma control technique is estimated to reach world-class level. However, the lack of cooling capacity to maintain the thermal steady state of the tokamak is becoming a severe engineering problem in preparation for K-DEMO. To simulate the fusion thermal condition, a test loop was constructed to withstand high temperature (150℃) and high pressure (20 bar). Through this loop, CHF experiments were carried out for the Hypervapotron channel and the results were compared with Baxi Hypervapotron CHF correlation. But, a high error average of 173.46% was found, and the Ja number index was changed to 0.45 in consideration of the 10 bar pressure to enable a reasonable prediction of 6.85% lower error. If CHF modeling and verification test is performed later, it will be possible to predict CHF over a wider range.
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.
농업 토양으로부터 분리한 carbofuran 분해 세균 Bacillus amyloliquefaciens DYC2-1의 특성
임지환(Ji-hwan Lim),박해성(Haeseong Park),서선일(Sun il Seo),김주은(Ju-eun Kim),김정은(Jung-eun Kim),이철원(Chul-won Lee),김평일(Pyoung il Kim) 한국농약과학회 2021 농약과학회지 Vol.25 No.4
Carbofuran (2,3-dihydro-2,2-dimethyl-7-benzofuranyl N-methylcarbamate) is one of the most frequently used insecticides in agricultural fields worldwide. Although carbofuran has excellent pest control property, its excessive use causes soil and river pollution. To remove the pesticide from the environment, bioremediation is considered the most inexpensive and efficient method. In this study, carbofuran biodegradable strain was isolated from the agricultural land. Next, identification of the microorganism through 16S rRNA gene sequence analysis and optimization of culture condition were carried out. Finally, the carbofuran degradation capacity of the strain was investigated through individual cultivation. As the result of 16S rRNA gene sequence analysis, the strain was identified as Bacillus amyloliquefaciens with 99.86% homology and named B. amyloliquefaciens DYC2-1. Culture optimization of the DYC2-1 strain was operated using different types of medium and culture conditions. The DYC2-1 showed the highest cell growth when cultured in TSB medium at 30oC and 600 rpm. Based on these results, individual culture for carbofuran degradation was conducted. The DYC2-1 strain was found to degrade about 100 mg/L (97%) of carbofuran over 120 h. Considering B. amyloliquefaciens species commonly possess plant growth promoting ability, the DYC2-1 strain is expected to contribute both soil remediation and enhancement of crop growth in the agricultural field.
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.