• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1997.10a
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• pp.114-121
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• 1997

회전 열파이프의 열전달 성능은 액막 두께 및 증발부로 귀환되는 응축 액막 유동율에 의해 결정된다. 그 동안 응축액 유동율을 촉진시키기 위하여 용기 내벽에 groove, 테이퍼 및 나선형 코일을 삽입하여 유동율을 높이는 방법들이 연구되었다. 본 연구도 회전 열파이프의 내부 관벽 구조에 관한 것으로써 삼각 단면을 갖는 회전 열파이프의 열전달 특성을 파악하고자 하였다. 삼각 단면을 갖는 회전 열파이프는 고속 회전 영역에서 모서리 부분으로 액막이 집중되어 관 내벽에 형성되는 액막 두께를 줄일 수 있으나 증발부에서 국부적인 과열이 발생되어 불안정한 작동 상태를 나타내었다. 따라서 본 연구에서는 개선방안으로 증발부에 부분적으로 원형관을 접합하였으며, 그 결과 dry-out의 억제와 함께 삼각 유동 단면에 의한 액막 두께 감소 효과를 볼 수 있었다. 회전체 발열부 냉각에 적용시키기 위해서는 앞으로 최적의 기하학적 형상에 따른 충전율 및 액막에서의 열전달에 대한 정량적인 해석 연구가 필요할 것으로 생각된다.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1998.10a
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• pp.193-208
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• 1998

본 논문에서는 써모싸이폰식 히트파이프의 열수송한계와 작동유체의 주입량이 파이프의 직경, 가열량 및 증발부와 응축부의 길이비 등에 따라 변화하므로 이러한 인자에 따른 적정 작동유체의 주입량과 가열량의 한계에 대해 고찰하였다. 특히 각종 전자부품의 냉각에 사용되는 히트파이프가 써모사이폰식이므로 사용작동유체에 대해 가열량에 따라 파이프의 직경예측이 가능토록 열수송한계특성에 대해 검토하고, 싸이리스터용은 증발부와 응축부의 길이비 변동이 심하므로 작동유체의 주입량이 중요한 성능인자로 작용하므로 길이비에 따른 작동유체의 주입량범위에 대해 기술하였다. 그리고 최적의 작동유체범위와 히트파이프의 증발열전달계수 및 응축열전달계수에 대한 실험으로부터 성능자료를 도출하여 이론해석과 비교검토하였다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.05a
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• pp.1169-1170
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• 2010

• Proceedings of the SAREK Conference
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• 2004.11a
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• pp.108-108
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• 2004

• Proceedings of the Korean Nuclear Society Conference
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• 1997.05a
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• pp.422-429
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• 1997

피동형 격납용기 냉각계통 해석을 위하여 격납용기 압력, 온도 과도현상 분석 코드인 CONTEMPT4/MOD5 전산코드에 피동형 격납용기 열전달 모델을 추가하였다. 외부공기의 순환에 의한 철제 격납용기와 차폐건물 사이의 환형 공간의 냉각모델은 자연대류 및 혼합 대류의 기존 실험적 상관식을 사용하였고 상부에서 분사된 물의 증발에 의한 열전달 현상은 analogy 개념을 적용한 질량전달 모델을 도입하였다. 개선된 전산코드로 1000Mwe급 원전의 피동형 격납용기에 대하여 각 실험적 상관식의 차이, 물막의 형성비율, 습식냉각 지연시간 등의 민감도 분석을 수행하였다.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.2
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• pp.167-174
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• 2004

A sorption cool pad brings cooling effect without any pre-cooling, nor any external energy supply. It uses evaporative cooling effect stimulated by the desiccative sorption. In this paper, heat and mass transfer in the sorption cool pad are investigated theoretically. The evaporative cooling process caused by the desiccant is modeled and analyzed considering the sorption characteristics of the desiccant. Two nondimensional parameters are found to dominate the cooling process： one is related to the psychrometric characteristics and the other is to the sorption capacity of the desiccant. The former decides the time to reach the lowest temperature and the later controls the time duration of the cooling effect being sustained.

• Food Science and Preservation
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• v.11 no.2
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• pp.263-268
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• 2004

Two field cooling tests were conducted to evaluate the cooling characteristic of paddy with a prototype grain cooler. The first test was carried out during summer season in a steel bin with 180.3ton of paddy at Sunchon. And the second test was carried out during harvesting season in a steel bin with 272.2ton of paddy at Ulsan. At the first test, initial paddy temperature of 23.6$^{\circ}C$ was dropped to 14$^{\circ}C$, and initial moisture content of 19.9% was dropped to 19.3% after 52.5 hours of cooling. At the second test, initial paddy temperature of 16.1$^{\circ}C$ dropped to 5.5$^{\circ}C$ after 78.0 hours of cooling. And, at the first test, the average air flow rates of chilled air leaving the grain cooler and penetrating the grain layer were 77.5 ㎥/min and 42.5 ㎥/min, respectively. To prevent leakage of chilled air from plenum chamber of steel bin, which was about 45% of the average air flow rates of chilled air leaving the grain cooler, a proper method was required. The average total power consumption at the first test during summer was 22.1 ㎾ with control of fan damper. At the second test, it was 17.4 ㎾ due to controlling the capacity of compressor with unloading solenoid valve and changing the flow rates of hot refrigerant gas flowing into evaporator and reheater from compressor, resulting in 27% reduction of energy consumption.

• Korean Chemical Engineering Research
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• v.44 no.3
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• pp.270-276
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• 2006

In this study, heat loss through free surface of water contained in bathtub due to conduction and evaporation has been analyzed. As a result of this study, a relational equation has been derived based on the basic theory of heat transfer to evaluate the performance of bath tubes. The derived equation was rational and quantitative. The major heat loss was found to be due to evaporation. Moreover, it has been found out that the speed of heat loss depends more on the humidity of the bathroom than the temperature of water contained in the bathtub. So, it is best to maintain the temperature of bathtub water to be between 41 to $45^{\circ}C$ and the humidity of bathroom to be 95％.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.3
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• pp.214-220
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• 2002

A small air conditioner using thermoelectric module has been designed and built. Three types of cooling methods, such as air cooling, closed-loop water cooling, and evaporative cooling, for hot side of thermoelectric module have been investigated. Among three types of cooling method, the evaporative cooling method is seen to be the most effective to achieve the steady state operation of a thermoelectric air conditioner The system performance with evaporative cooling method are also studied in detail for several oprating parameters, such as input power to the thermoelectric module, water or air flow rate at the hot side, and air flow rate at the cold side. The results obtained indicate that the cooling capacity of a system is increased with an increase in the input power to the thermoelectric module while the system COP is decreased. It is also found that the optimal air flow rate as well as water flow rate at the hot side is needed for the best system performance at a liven operating condition. Both the system COP and cooling capacity are increased as the air flow rate at cold side is increased.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.12
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• pp.1766-1775
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• 2001

A theoretical analysis on the heat and mass transfer in an evaporative cooler is presented in this work. The evaporative cooler is modeled as a channel filled with porous media the interstitial surface of which is covered by thin water film. Assuming that the Lewis number is unity and the water vapor saturation curve is linear, exact solutions to the energy and vapor concentration equations are obtained. Based on the exact solutions, the characteristics of the heat and mass transfer in the evaporative cooler are investigated. The comparison of the cooling performance between the evaporative cooler and the usual sensible heat exchanger is also carried out. Obviously, the evaporative heat exchanger shows better cooling performance than the sensible heat exchanger. This is due to the latent heat of water vaporization, which results in apparent increases both in the interstitial heat transfer coefficient and the specific heat of the air stream in the evaporative cooler.