• Journal of international Conference on Electrical Machines and Systems
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• 제3권1호
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• pp.105-109
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• 2014

Converter valve cooling device as the heat exchanger, is known as the converter valve's blood circulation system, Inefficiency of the equipment will not only lead to the component overheating damage, but also serious DC system outage. Therefore, reliable HVDC valve cooling system is essential for the HVDC transmission system. In this article, analysis on the two-phase flow heat transfer characteristics and security of the evaporative cooling technology are provided, the technology's advantage and feasibility are discussed.

• 생물환경조절학회지
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• 제7권3호
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• pp.237-245
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• 1998

극심한 고온으로 인해 정상적인 작물의 재배가 어려운 여름철의 온실 내 기온을 억제시키기 위한 방법 중 가장 효율을 인정받고 있는 증발냉각법은 실내 습도의 증가로 인해 그 사용에 제한을 받게 된다. 본 연구에서는 온실에서 증발냉각법의 냉방효율을 높이기 위한 방법으로 냉수파이프를 설치하여, 그 열적 특성을 분석하고, 제습효과를 조사하였으며, 그 결과를 요약하면 다음과 같다. 동파이프와 아연도금스틸파이프의 총열전달량을 비교한 결과, 동파이프가 다소 크게 나타났으나, 유의성이 없었으며, 두 가지 파이프 모두 이론값 보다 실측값이 더 작게 나타났다. 냉수파이프 표면에 응축되어 제거된 수증기의 양은 동파이프와 아연도금스틸파이프 사이에서 큰 차이를 보이지 않았으나, 두 가지 파이프 모두에서 제습효과는 충분히 큰 것으로 나타났다. 냉수파이프를 설치함으로써 증발냉각시스템의 냉방효율을 평균 48%만큼 높일수 있으며, 평균 1.3$^{\circ}C$만큼의 실내기온을 추가로 냉각시킬 수 있는 것으로 예측되었다. 또한, 냉수파이프를 이용해 증발냉각시스템의 가동으로 인한 실내의 과습문제를 해결하기 위해서는 파이프표면의 응축된 수분을 효과적으로 제거할 수 있는 장치나 방법에 대한 추가적인 연구가 필요할 것으로 판단된다.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2006년도 하계학술발표대회 논문집
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• pp.156-161
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• 2006

The rivulet is a narrow stream of liquid flowing down a solid surface. Heat transfer of rivulet flow over on inclined heated surface has been investigated experimentally. This problem is of particular interest in the understanding of fundamental mechanism on rivulet heat transfer as well as in the design of a regenerative evaporative cooler. The rivulet is seem to be meandering flow, single wide flat flow. and film flow as rivulet flow rate is increased. Even though the wetted surface area is increased with an increase in the rivulet flow rate, the absorbed heat transfer of rivulet flow from a heated surface strongly depends on the flow pattern of rivulet.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2001년도 추계학술발표회요약집
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• pp.122.1-122
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• 2001

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2291-2296
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• 2007

Thermal transport from vertical heated surface to falling liquid film in a channel has been investigated experimentally. Air-flow is introduced into channel to make a counter flow against falling liquid film. This problem is of particular interest in the design of direct contact heat exchange system, such as cooling tower, evaporative cooling system, absorption cooling system, and distillation system. The effects of channel width and air flow rate on the heat transfer to falling liquid film are studied in detail. The results obtained indicate that heat transfer rate is gradually decreased with an increase in the channel width without air flow as well as with air flow in a channel. It is also found that heat transfer rate of air-flow is increased while heat transfer rate of falling liquid film is decreased with an increase in the air flow rate at a given channel width. However, total heat transfer rate form the heated surface is increased as the air flow rate is increased.

• 대한기계학회논문집B
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• 제32권5호
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• pp.335-341
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• 2008

Thermal transport from vertical heated surface to falling liquid film in a channel has been investigated experimentally. Air-flow is introduced into channel to make a counter flow against falling liquid film. This problem is of particular interest in the design of direct contact heat exchange system, such as cooling tower, evaporative cooling system, absorption cooling system, and distillation system. The effects of channel width and air flow rate on the heat transfer to falling liquid film are studied in detail. The results obtained indicate that heat transfer rate is gradually decreased with an increase in the channel width without air flow as well as with air flow in a channel. It is also found that heat transfer rate of air-flow is increased while heat transfer rate of falling liquid film is decreased with an increase in the air flow rate at a given channel width. However, total heat transfer rate from the heated surface is increased as the air flow rate is increased.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2005년도 창립60주년 기념 추계 학술대회
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• pp.10.2-10.2
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• 2005

• Nuclear Engineering and Technology
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• 제30권1호
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• pp.26-39
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• 1998

The containment pressure and temperature transient analysis computer code CONTEMPT4/MOD5 is modified to incorporate the passive containment cooling models. The correlations are selected from the existing experimental heat transfer correlations to model the natural and mixed convection in annular space between the containment shell and the shield building. The evaporative heat transfer of the water film on the outer shell of the containment is modeled using the correlations derived from the analogy between the heat and mass transfer. The modified code is applied to the Ap600 containment transient analysis for the model verification and the results are compared to the results of GOTHIC calculation done by Westinghouse. Also, d series of parametric sensitivity studies of heat transfer correlations, water film ratio and delay time of the wet cooling on the containment peak pressure and temperature following LOCA are performed for the containment of 1000MWe passive plant, KP1000.

• 대한기계학회논문집B
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• 제32권4호
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• pp.290-299
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• 2008

Evaporation heat transfer characteristics of $CO_2$/propane mixtures in horizontal smooth and micro-fin tubes have been investigated by experiment. The experiments were carried out for several test conditions of mass fluxes, heat fluxes, compositions of $CO_2$/propane refrigerant mixtures and tube geometries. Direct heating method was used for supplying heat to the refrigerant where the test tube was uniformly heated by electric current which was applied to the tube wall. Heat transfer coefficient data during evaporation process of $CO_2$/propane mixtures were measured for 5 m long smooth and micro-fin tubes with outer diameters of 5 mm, respectively. The tests were conducted at mass fluxes of 318 to 997 $kg/m^2s$, heat fluxes of 6 to 20 $kW/m^2$ and for several mixture compositions (100/0, 75/25, 50/50, 25/75, 100/0 by wt% of $CO_2$/propane). The differences of heat transfer characteristics between smooth and micro-fin tubes for various compositions of $CO_2$/propane refrigerant mixtures and the effect of mass flux, and heat flux on enhancement factor (EF) and penalty factor (PF) were presented.

• 한국의류학회지
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• 제20권6호
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• pp.1071-1083
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• 1996

This study was carried out to obtain some fundamental data for designing thermally comfortable Korean folk clothes (KFC) which were classified into 4 groups according to seasons and materials. It was conducted to find the relationship among structural, thermal, and moisture transfer properties, and then the properties of heat and mositure transfer while changing thickness of air layer of selected similar fabrics with various thickness were examined. The summarized results of this study were as follows ; 1. The relationship between the structrual and thermal properties showed high positive correlation with thickness SE thermal insulation value (TIV), porosity & TIV. 2. The relationship between the structural and mositure transfer properties showed high negative correlation with thickness & moisture vapor permeability (Mp), porosity & Mp respectively. 3. The relationship between the heat and moisture transfer properites showed high negative correlation with qmax, air permeability (Ap), Mp & TIV while showed high positive with Ap & Mp respectively. 4. Resistance to dry heat transfer according to thickness of air layer for KFC was increassed rapidly up to 2 mm and above this increasing rate was reduced. Resistance to evaporative heat transfer was remarkable changes in 6∼8 mm but slowly in 6∼8 man. 5. Mioisture permeability index (i) according to thickness of air layer for KFC showed the greatest value at 2 mm but had not difference between groups according to thickness.