• 에너지공학
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• 제10권4호
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• pp.342-348
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• 2001

A new design concept for a decay heat removal system in a liquid metal reactor is proposed. The new design utilizes a thermosyphon to enhance the heat removal capacity and its heat transfer characteristics are analyzed against the current PSDRS (Passive Safety Decay heat Removal System) in the KAL IMER (Korea Advanced LIquid MEtal Reactor) design. The preliminary analysis results show that the new design with a thermosyphon yields substantial increase of 20∼40% in the decay heat removal capacity compared to the current design that do not have the thermosyphon. The new design reduces the temperature rise in the cooling air of the system and helps the surrounding structure in maintaining its mechanical integrity for long term operation at an accident. Also the analysis revealed the characteristics of the interactions among various heat transfer modes in the new design.

• Nuclear Engineering and Technology
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• 제31권5호
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• pp.486-497
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• 1999

The local heat transfer coefficient is experimentally investigated for the reflux condensation in a countercurrent flow between the steam-air mixture and the condensate, A single vertical tube has a geometry which is a length of 2.4m, inner diameter of 16.56mm and outer diameter of 19.05mm and is made of stainless steel. Air is used as a noncondensible gas. The secondary side has a shape of annulus around vertical tube and the lost heat by primary condensation is transferred to the coolant water. The local temperatures are measured at 11 locations in the vertical direction and each location has 3 measurement points in the radial direction, which are installed at the tube center, at the outer wall and at the coolant side. In three different pressures, the 27 sets of data are obtained in the range of inlet steam flow rate 1.348∼3.282kg/hr, of inlet air mass fraction 11.8∼55.0%. The investigation of the flooding is preceded to find the upper limit of the reflux condensation. Onset of flooding is lower than that of Wallis' correlation. The local heat transfer coefficient increases as the increase of inlet steam flow rate and decreases as the increase of inlet air mass fraction. As an increase of the system pressure, the active condensing region is contracted and the heat transfer capability in this region is magnified. The empirical correlation is developed by 165 data of the local heat transfer. As a result, the Jacob number and film Reynolds number are dominant parameters to govern the local heat transfer coefficient. The rms error is 17.7% between the results by the experiment and by the correlation.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2005년도 창립60주년 기념 추계 학술대회
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• pp.6.1-6.1
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• 2005

• Nuclear Engineering and Technology
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• 제34권5호
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• pp.455-467
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• 2002

RELAP5/MOD3.2 was modified to perform the thermal-hydraulic safety analysis for HANARO transients. Several aspects of RELAP5/MOD3.2 were modified or replaced by new features to properly simulate the unique HANARO characteristics such as the finned fuel element, the cooling mechanisms by both plate type heat exchanger and the natural circulation. Especially, the heat transfer packages were modified to be more appropriate for the safety analysis and the heat transfer models were developed for the plate type heat exchanger as well as natural circulation through the pool water. This modified version of RELAP5/MOD3.2 is renamed as RELAP5/HANARO. The thermal-hydraulic simulations of the single fuel pin test and plate type heat exchanger were peformed to assess the realistic predicting capabilities of RELAP5/HANARO and compared with experimental results and manufacturer＇s data in this paper. In addition, the natural circulation experiment using the scaled bundle was simulated to validate the capability of RELAP5/HANARO. The simulation results show almost similar trend with experimental data. Therefore, it is proved that RELAP5/HANARO has a confidence to use for the safety analyses of HANARO.

• 설비공학논문집
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• 제12권3호
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• pp.284-291
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• 2000

A basic pulse tube refrigerator has been constructed with extensive instrumentation to study the characteristics of the heat exchanger experimentally under the oscillating pressure and the oscillating flow. This paper describes the sequential experiments with the basic pulse tube refrigerator. The experiments were performed for various cycle frequencies under the square pressure wave forms. First, the heat flux was measured through the cycle at the both cold and warm end heat exchangers without the regenerator. In order to enhance the thermal communication capability of the heat exchanger with the gas at low operating frequencies, a unique design of the triangular shape radial fin concept was applied to the heat exchangers. For the fin heat exchanger, the measured heat flux and the calculated heat flux from the two well-known oscillating heat transfer correlations were compared and discussed. Second, the regenerator was added to the pulse tube to make a basic pulse tube refrigerator configuration. The experiment showed the great impact of the regenerator on the temperature and the heat flux profiles. At the warm-end, the cyclic averaged heat flux had its maximum value at the specific operating frequency. The paper presents the explanation of the surface heat pumping effect as well as the experimental data.

• 조명전기설비학회논문지
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• 제18권5호
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• pp.169-173
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• 2004

본 논문은 전력계통의 전압 안정도 제약 문제를 해결하는데 고온 초전도 케이블을 적용하기 위한 기법을 제시하였다. 대전력계통의 유효 송전용량은 종종 전압 안정도 제약에 의해 결정된다. 기존의 초전도 케이블 응용 연구는 주로 도심지역의 고밀도 전력 수송 문제를 해결하는 대안으로 연구의 초점을 두어왔지만, 고온 초전도 케이블의 선로정수 개선효과를 이용하면 전압 안정도로 제약된 계통의 송전용량을 증가시킬 수 있어 그 응용 범위가 확대될 수 있다. 전압 안정도에 의한 최대 수송전력을 결정하는 데는 IPLAN에 의한 P-V곡선을 이용하였고, 대체 대상선로는 부하 증가시 무효전력 손실감도가 가장 큰 선로로 하였다. 결과의 타당성을 검증하기 위해 IEEE 14모선 계통을 사용하였으며, 적용결과 Case II는 70[%], Case III에서는 160[%]의 추가 수송 능력 증가를 가져올 수 있었다.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1999년도 춘계학술발표회요약집
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• pp.104-104
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• 1999

The local heat transfer coefficient is experimentally investigated for the reflux condensation in a countercurrent flow between the steam-air mixture and the condensate. A single vertical tube has a geometry which is a length of 2.4m, inner diameter of 16.56mm and outer diameter of 19.05mm and is made of stainless steel. Air is used as a noncondensible gas. The secondary side is installed in the form of coolant block around vertical tube and the heat by primary condensation is transferred to the coolant water. The local temperatures are measured at 15 locations in the vertical direction and each location has 3 measurement points in the radial direction, which are installed at the tube center, at the outer wall and at the coolant side. In three different pressures, the 27 sets of data are obtained in the range of inlet steam flow rate 1.348 -3.282kg/hr, of inlet air mass fraction 11.8 -55.0%. The local heat transfer coefficient increases as the increase of inlet steam flow rate and decreases as the decrease of inlet air mass fraction. As an increase of the system pressure, the active condensing region is contracted and the heat transfer capability in this region is magnified. The empirical correlation is developed represented with the 165 sets of local heat transfer data. As a result, the Jacob number and film Reynolds number are dominant parameters to govern the local heat transfer coefficient. The rms error is 17. 7% between the results by the experiment and by the correlation.

• 에너지공학
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• 제24권1호
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• pp.42-50
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• 2015

신형 원전의 피동격납건물냉각계통(PCCS: Passive Containment Cooling System)을 구성하는 단일 전열관의 열제거 성능을 평가하기 위해, 비응축성 기체 존재 시 수직 튜브 외벽에서 발생하는 증기의 응축 열전달에 대한 실험을 수행하였다. 외경 40 mm, 길이 1.0 m의 전열관 외벽에서 증기-공기 혼합물의 평균 열전달계수를 측정하였으며, 압력 2-4 bar, 공기의 질량분율 0.1-0.7의 범위에서 실험데이터를 수집하였다. 이를 통해 압력과 비응축성기체의 농도가 응축 열전달계수에 미치는 영향을 평가하였다. 실험결과를 기존의 열전달모델인 Uchida와 Dehbi의 상관식과 비교하였으며, 이들 상관식은 실험결과에 비해 상대적으로 열전달계수를 낮게 예측함을 확인하였다.

• 한국지반환경공학회 논문집
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• 제18권7호
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• pp.5-12
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• 2017

강원권의 동절기에는 한랭기후로 인한 복합적으로 터널 라이닝 표면이 열화되는 형태와 외관상의 문제 및 균열이 발생하게 된다. 이에 따른 재해복구 관련 기술 개발을 통한 복구비용의 절감이 필요한 실정이지만, 국내에서는 기온에 따른 도로터널 라이닝의 피해 저감에 대한 연구는 미비한 상태이다. 따라서, 본 논문에서는 터널 라이닝의 단열성능을 개선하기 위하여 단열재료(에어로젤, 액상단열재)에 열전달량 실험을 실시하였다. 실험결과 단열재의 도포에 따라 열전달량이 상당히 감소하는 것으로 나타나, 동결지역에서의 터널라이닝 피해저감 효과를 확인할 수 있었다.

• 조명전기설비학회논문지
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• 제19권6호
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• pp.29-35
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• 2005

본 논문은 고온 초전도 케이블을 전력계통의 송전용량 증대를 위해 적용시켰을 경우, 고장발생시 초전도케이블에서 예상되는 ??????치의 영향에 대해 안전하게 제어할 수 있는 방법을 제시하였다. 접근 방법으로는 초전도케이블의 ??????치 특성을 열평형 방정식으로 모델링하고 그 결과 고장전류에 따른 케이블의 설계 최대 온도상승한계에 도달하는 시간을 산출하여 기존의 보호계전시스템의 차단시간과 비교함으로서 안전성 여부를 판정하였다. ??????치발생 고장시간을 모의하기 위해 초전도케이블용 EMTDC모형을 개발하였으며, 모의 결과 초전도 케이블 계통을 보호할 수 있는 안전성 제어방식이 설계 가능함을 보였다.