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과냉각수조 내의 제트에 의한 용융우드메탈 미립화에 관한 실험적 연구
허효 ( Hyo Heo ),정동욱 ( Dong Wook Jerng ),방인철 ( In Cheol Bang ) 한국분무공학회 2014 한국액체미립화학회지 Vol.19 No.4
The liquid jet breakup has been studied in the areas such as aerosols, spray and combustion. The breakup depends on several physical parameters such as the jet velocity, the nozzle inner diameter, and the density ratio of the water to the jet. This paper deals with characteristics of the jet breakup according to the jet velocity and the nozzle diameter. In order to consider only hydrodynamic factors, all the experiments were conducted in non-boiling conditions. The jet behavior in the water pool was observed by high-speed camera and PIV technique. For the condition of the inner diameter of 6.95 mm and the jet velocity of 2.8 m/s, the debris size of 22 mm gave the largest mass fraction, 39%. For higher jet velocity of 3.1 m/s, the debris size of 14 mm gave the largest mass fraction, 36%. For the nozzle with inner diameter of 9.30 mm, the debris size distribution was different. For jet velocity of 2.8 m/s and 3.1 m/s, the debris size with the largest mass fraction was found to be 14 mm. It was identified that the debris size decreased as the diameter or the jet velocity increased.
확률론적 평가를 이용한 원자력발전소 소내전력공급계통 신뢰도 감시 방법
박진엽(Jin Yeub Park),정동욱(Dong Wook Jerng) 대한전기학회 2009 전기학회논문지 Vol.58 No.3
This paper introduces a method to establish performance criteria of the in-house power supply system in nuclear power plants. The performance criteria of the system is presented in terms of the number of function failures and amount of the out-of-service time that can be allowed commensurate with the probabilistic safety assessment results of the nuclear power plants. To obtain the performance criteria such as reliability and availability, the functions of the system were analyzed and probabilistic assessment results were utilized. This method provides quantitative guidelines in selecting and monitoring system functions to determine an adequate level of maintenance quality in order to ensure the probabilistic goals for the safety of the nuclear power plants.
과냉각수조 내의 제트에 의한 용융우드메탈 미립화에 관한 실적 연구
허효 ( Hyo Heo ),정동욱 ( Dong Wook Jerng ),방인철 ( In Cheol Bang ) 한국액체미립화학회 2014 한국액체미립화학회 학술강연회 논문집 Vol.2014 No.-
The liquid jet breakup has been studied in the areas of aerosols, spray and combustion. The jet breakup depends on several parameters, such as the jet velocity, the inner diameter of the nozzle and the density ratio of the water to the jet. This paper deals with characteristics of the jet breakup according to the jet velocity and the nozzle diameter. In order to consider only hydrodynamic factors, all jet breakup experiments were conducted in non-boiling conditions. In the present study, the wood`s metal was used as the jet material. The jet behavior in the water pool was observed by high-speed camera and PIV technique. All the experiments showed that the jet breakup occurred instantly as the jet contacted with the subcooled water and the fragmented debris moved in radial direction. However, there were some differences between experimental conditions. At the small nozzle diameter, there was no significant difference according to changes in the jet velocity. Generally, the breakup rate strongly depends on the jet velocity but the density ratio affects the breakup behavior most significantly at low jet velocity(< 4.5 m/s). For the larger nozzle diameter, extensive breakup occurred as the jet entered the water pool. It was observed that the more molten wood`s metal is ejected, the debris moved strongly in radial direction. After each experiment, the debris of the jet was collected, dried and sieved to analyze characteristics of the jet breakup. Then, the debris was distributed according to the debris size. For the condition of inner diameter of 6.95 mm and the jet velocity of 2.8 m/s, the debris size of 22 mm gave the largest mass fraction, 39%. For higher jet velocity of 3.1 m/s, the debris size of 14 mm gave the largest mass fraction, 36%. For the nozzle with inner diameter of 9.30 mm, the debris size distribution was different. For jet velocity of 2.8 m/s and 3.1 m/s, the debris size with the largest mass fraction was found to be 14 mm. It means that the debris size decreases as either the diameter or the jet velocity increases.
비응축성 기체 존재 시 수직관 외벽에서의 응축 열전달계수 상관식 개발
장영준(Yeong-Jun Jang),최동재(Dong-Jae Choi),김신(Sin Kim),정동욱(Dong Wook Jerng),이연건(Yeon-Gun Lee) 대한기계학회 2018 大韓機械學會論文集B Vol.42 No.3
본 연구에서는 비응축성 기체(공기)가 존재할 때, 10 mm의 직경을 갖는 수직 튜브 외벽에서의 응축 열전달계수를 측정하였다. 압력 2~5 bar, 공기 질량분율 10~75 %의 범위에서 실험을 수행하였다. 응축튜브 직경의 차이가 열전달계수에 미치는 영향을 평가하기 위해 측정 결과를 외경 40 mm의 응축튜브로부터 얻은 Lee의 실험 결과와 비교하였다. 본 연구의 측정결과와 Lee, 그리고 Dehbi의 실험결과를 이용하여 전열관의 직경에 의한 영향을 고려할 수 있는 실험적 상관식을 제안하였다. 제안된 상관식의 검증을 위해 Kawakubo의 실험결과와 예측값을 비교하였고, 평균 표준편차는 약 27 %로 나타났다. In this study, condensation heat transfer coefficients are measured in the presence of noncondensable gas (i.e., air) on a vertical tube with a 10-mm outer diameter. Experiments are conducted at pressures ranging from 2 to 5 bar and an air-mass fraction from 10 to 75 %. The experimental results are compared to the heat transfer coefficients obtained on a 40-mm O.D. tube, researched by Lee et al. Using the consolidated data from this study and Lee"s and Dehbi"s tests, a new empirical correlation for the condensation heat transfer coefficient of an air-steam mixture is developed. The proposed correlation is assessed against Kawakubo"s experimental results, and the mean standard deviation is ~27 %.
김경문(Koung Moon Kim),황지환(Ji Hwan Hwang),이창훈(Chang Hun Lee),심규현(Gyu Hyeon Shim),정동욱(Dong-Wook Jerng),안호선(Ho Seon Ahn) 대한기계학회 2018 대한기계학회 춘추학술대회 Vol.2018 No.12
One of the key safety features of a Prototype Gen-IV Sodium-cooled Fast Reactor (PGSFR) is the adopting of reactor vault cooling system (RVCS). Development of the PGSFR has been ongoing in KAERI (Korea Atomic Energy Research Institute). The assessment of the RVCS must be conducted to ensure decay heat removal capability under severe accident conditions. A down scale model is developed by the Ishii’s method of scaling law, which is based on the three similitude laws, i.e. dynamic, kinematic, and geometric. First, we have considered the basic energy balance between the total heat generation from the decay heat and heat removal from heat transfer, e.g. the natural circulation and the radiation heat transfer. For the reliable design of the experimental facility of RVCS, it would be considered the non-dimensional Richardson number from the momentum equation as the key parameter, which would determine the driven buoyancy flow regrading to the temperature difference of air flow. To finalize the scale analysis, we have compared CFD simulation.