• Nuclear Engineering and Technology
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• 제52권1호
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• pp.27-36
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• 2020

Natural convection and thermal stratification phenomena are found in large water pools that are being used as heat sinks for decay heat removal from the reactor core using passive heat removal systems. In this study, the two-phase (water and air) natural convection and thermal stratification phenomena with conjugate heat transfer in the rectangular enclosure were investigated numerically using ANSYS Fluent 17.2 code. The transient numerical simulations of these phenomena in the full-scale computational domain of the experimental facility were performed. Generation of water vapour bubbles around the heater rod and evaporation phenomena were included in this numerical investigation. The results of numerical simulations are in good agreement with experimental measurements. This shows that the natural convection is formed in region above the heater rod and the water is thermally stratified in the region below the heater rod. The heat from higher region and from the heater rod is transferred to the lower region via conduction. The thermal stratification disappears and the water becomes well mixed, only after the water temperature reaches the saturation temperature and boiling starts. The developed modelling approach and obtained results provide guidelines for numerical investigations of thermal-hydraulic processes in the water pools for passive residual heat removal systems or spent nuclear fuel pools considering the concreate walls of the pool and main room above the pool.

• 한국유체기계학회 논문집
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• 제5권1호
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• pp.49-54
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• 2002

HANARO, 30 MW of research reactor, was installed at the depth of 13m in an open pool. The $90\%$ of primary coolant was designed to pass through the core and to remove the reaction heat of the cote. The rest, $10\%$, of the primary coolant was designed to bypass the core. And the reactor coolant through and bypass the core was inhaled at the top of chimney by the coolant pump to prevent the radiated gas from being lifted to the top of reactor pool. But, the part of core bypass coolant was not inhaled by the reactor coolant pump and reached at the top of reactor pool by natural convection, and increased the radiation lovel on the top of reactor pool. To reduce the radiation level by protecting the natural convection of the core bypass flow, the hot water layer (HWL, hereinafter) was installed with the depth of 1.2 m from the top of reactor pool. As the HWL was normally operated, the radiation level was reduced to five percent ($5\%$) in comparing with that before the installation of the HWL. When HANARO was operated at a higher temperature than the normal temperature of the HWL by operating the standby heater, it was found that the radiation level was more reduced than that before operation. To verify the reason, the heat loss of the HWL was calculated by Visual Basic Program. It was confirmed through the results that the larger the temperature difference between the HWL and reactor hall was, the more the evaporation loss increased. And it was verified that the radiation level above was reduced mote safely by increasing the capacity of heater.

• 한국산업융합학회 논문집
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• 제10권1호
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• pp.21-26
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• 2007

As DDI or GDI engine discharges very low heat due to its high thermal efficiency, the heat source is not enough for heating the passenger compartment in cold climate condition. To remedy the heating problem, the conventional HFC-134a automotive air-conditioning system has been attempted to run as a heat pump mode. Futhermore, an auxiliary electric heater of new type was equipped to the heat pump air-conditioning loop as a new approach. Hence, a proto-type heat pump air conditioner has been made and tested to investigate the feasibility of the HFC-134a automobile air-conditioning system that could be worked as a heat pump. The experiment results showed that the sufficient heating capacity could be obtained by adding a heat pump with an new electric type auxiliary heater into the conventional heat core in low temperature condition.

• 태양에너지
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• 제9권3호
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• pp.64-72
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• 1989

In this study, the computer simulation for the heat transfer in pulse combustion water heater is performed. The attention is focused to the effects of the installation of corebuster in the flue tube on heat transfer. The energy equations are established for both wall and gas side in the combustion chamber, flue way, exhaust chamber and muffler, and the numerical calculation is executed. Zone method takes longer computer calculation time compared with semi-zone method. Semi-zone method is chosen for numerical calculation. As a result of this study, it is found that the installation of the core buster in flue tube increases total heat transfer. It is also found that the total heat transfer is increased with the increasing of the ratio of the cross section area of corebuster to that of the flue tube. However, the heat transfer effect is negligible for the area ratio above 0.5.

• Journal of Mechanical Science and Technology
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• 제18권5호
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• pp.847-856
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• 2004

Heaters for the spacecraft propulsion system are sized to prevent propellant from catastrophic freezing. For this purpose, thermal mathematical model (TMM) of the propulsion system is developed. Calculation output is compared with the results obtained from thermal vacuum test in order to check the validity of TMM. Despite a little discrepancy between the two types of results, both of them are qualitatively compatible. It is concluded that the propulsion system heaters are correctly sized and TMM can be used as a thermal design tool for the spacecraft propulsion system.

• 전기전자학회논문지
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• 제18권3호
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• pp.420-426
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• 2014

본 연구에서는 저온유동성 성능검사 시스템 구현을 통해 디젤 차량용 통합형 연료필터의 성능을 평가한다. 저온유동성시험 장치의 시험조건은 경유(또는 등유)를 사용하고, 상온, -20 및 $-30^{\circ}C$ 에서 경유공급압력 $3.4kgf/cm^2$, 연료공급량 60 l/H, 설정전류 30 A 및 전압은 $13V_{dc}$를 사용한다. 시료시험으로 통합필터를 지그에 장착하고, 경유(또는 등유)를 일정압력과 유량으로 설정하여 챔버 탱크와 필터에 채운 후, 설정시간 동안 설정온도로 냉각한 후, 필터 전후에 따라 유압과 시동시간, 히터의 소모전류 및 전력을 측정한다.

• 한국산학기술학회논문지
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• 제20권3호
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• pp.476-482
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• 2019

본 기후변화협약, 온실가스배출규제와 같은 규제적 규약들은 고효율 에너지 기자재 개발과 에너지의 효율적 이용을 촉진하는 촉매로 작용하고 있다. 에너지소비가 큰 분야 중 전열기기가 효율이 좋지 못한 편이다. 전기보일러는 히터에 물을 접촉시켜 순환시키는 방식을 주로 사용하고 있다. 기존 전기보일러를 활용할 경우 물의 미네랄이 고온의 히터와 접촉하여 탄화되어 흡착되는 과정에서 히터의 부식을 촉진시키고 히터의 효율을 저하시킨다. 이러한 이유로 에너지 효율이 높고, 전도나 대류가열보다 피가열물을 균일하게 가열시킬 수 있는 유도가열방식을 보일러에 적용시킨 전기유도보일러가 각광을 받고 있는데, 이 방식은 물이 담겨 있는 보일러 관로를 유도가열방식으로 가열하여 직접가열시 발생하는 문제를 해결시킬 수 있는 대안으로 인정받고 있다. 비교적 오랜 기간 유도가열에 대한 연구가 이루어졌음에도 불구하고 유도가열을 이용한 전열기술에 대한 연구결과는 그리 많지 않은 실정이다. 따라서 본 논문에서는 전기유도보일러의 발열효율을 개선하기 위하여 매개변수연구방법을 통하여 권선의 단면적, 권선의 수 및 권선의 겹수에 의한 영향을 유한요소법을 이용하여 해석하고 발열의 요소가 되고 있는 동손과 철손을 분석하여 발열을 극대화시킬 수 있는 권선설계방법으로 총손실이 최대가 되는 설계점을 찾는 방법을 제시하였다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.345-348
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• 2008

The computer-aided performance simulation can reduce periods for development of products and cut down on the cost comparing with former trial-and-error procedures. This study has developed a simulation program for a vehicle thermal management system integrating an engine cooling system and an air conditioning system considering interactions and arrangement of air side heat exchangers such as power steering oil cooler, air-cooled transmission oil cooler, condenser, and radiator. The program may be also used for the system performance analysis according to the configuration of the engine coolant side heat exchangers such as water-cooled transmission oil cooler, EGR cooler, and heater core. Experiments utilizing an environmental wind tunnel has been conducted to assess the performance of the system according to the arrangement of air side heat exchangers. Some modification of the coolant loop layout can enhance the heat core performance up to 7% according to the results of the simulations.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1997년도 춘계학술대회논문집
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• pp.249-252
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• 1997

Mini-mill process which is one of the new steel making process to be able to produce the hot rolled strip by thin slab caster, was completed in the kwangyang steel work. The new process was constructed liquid core deduction, tandem reduction unit, induction heater, coil box and finishing mill to be varied width. Therefore, in oder to make sure of target strip width, analysis of actual plant data was done to fine out amount of width deviation. Finally, the predication system of width in the mini-mill process was developed to included temperature caculation model.

• 한국산학기술학회논문지
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• 제4권4호
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• pp.361-365
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• 2003

Oxide etcher장비에서 실리콘 웨이퍼를 잡고 공정을 수행할 수 있는 단극 (unipolar) 형태의 E-chuck을 제작하였다. 단극 형태의 E-chuck을 개발하기 위하여 핵심기술인 폴리이미드 박막의 코팅기술과 알미늄 표면의 양극처리기술을 개발하였다. E-chutk은 폴리이미드 재료를 표면 물질로 사용하여 플라스마에 의한 표면 손상을 최소화하였다. Oxide etcher 장비에 사용되는 핵심 부품인 E-chuck의 제조 과정을 살펴보고 히터 내장형 E-chuck을 위한 박막형 전열체 기술을 개발하였다.