• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.28 no.8
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• pp.316-324
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• 2016

This study investigated a compact regenerative evaporative cooler (REC). To achieve practical applications of an REC, it is very important to consider the compactness as well as the cooling performance. Therefore, a prototype of the REC was designed and fabricated to improve the compactness by reducing the length through the insertion of fins in both the dry and wet channels. The REC prototype was tested in terms of performance evaluation under various operating conditions. An analytical model was also developed to analyze the effects of the axial conduction through the solid body of the REC, the wetness of the surface in the wet channel, and the thermal capacity of the evaporation water flow. The model was validated by comparing the results of a simulation with experimental data. The numerical simulation was based on the model to analyze the performance of the REC and to suggest methods to improve the cooling performance of the REC. Finally, the performance of the present REC was compared to that obtained in previous experimental studies. The results showed that the REC prototype in the present study is the most compact and achieves the highest cooling performance.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.5
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• pp.393-401
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• 2006

The regenerative evaporation water cooler is devised and analysed in this study. The regenerative evaporation water cooler is composed of a sensible heat exchanger to cool the incoming air, followed by a latent heat exchanger to cool the water evaporatively with the cooled air flowing out of the sensible heat exchanger. By linearizing psychrometric characteristics, the heat and mass transfer in the regenerative evaporation water cooler is analyzed theoretically. The results show that the water can be cooled down even lower than the wet-bulb temperature of the inlet air. When the inlet air is $32^{\circ}C$ and 20% in relative humidity, and the inlet temperature of the water is $20^{\circ}C$, the regenerative evaporation water cooler provides a larger cooling capacity than the conventional evaporation water cooler if the effectiveness of the latent heat exchanger is higher than 0.6 and that of the sensible heat exchanger is higher than 0.5.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.12
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• pp.4721-4726
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• 2010

The performance characteristics of water-chilling heat pump using CO2 for the control of inverter frequency was investigated experimentally. An experimental apparatus is consisted of a compressor, a gas cooler, an expansion valve, an evaporator and a liquid receiver. All heat exchangers used in the test rig are counter flow type heat exchangers with concentric dual tubes, which are made of copper. The gas cooler and the evaporator consist of 6 and 4 straight sections respectively arranged in parallel, each has 2.4m length. The experimental results summarize as the following: for constant inlet temperature of evaporator and gas cooler, as mass flow rate, compression ratio and discharge pressure increases with the inverter frequency. And heating capacity and compressor work increases, but coefficient of performance(COP) decreases with the inverter frequency of compressor. As inlet temperature of secondary fluid in the evaporator increases from $15^{\circ}C$ to $25^{\circ}C$, compression ratio and compressor work decreases, but mass flow rate, heating capacity and COP increases with the inverter frequency of compressor. The above tendency is similar with performance variation with respect to the variation of inverter frequency in the conventional vapor compression refrigeration cycle.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.2
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• pp.264-269
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• 2008

This paper presents the experimental results of evaporation heat transfer coefficients of HC(e.g. R290 and R600a), R-22 as a HCFCs refrigerant in horizontal double pipe heat exchangers, having four different inner diameters of 10.07 mm and 6.54 mm respectively. The experiments of the evaporation process were conducted at mass flux of $35.5{\sim}210.4\;kg/m^2s$ and cooling capacity of $0.95{\sim}10.1\;kW$. The main results were summarized as follows : The average evaporation heat transfer coefficient of R-290 and R-600a was higher value than that of R-22. In comparison with R-22, the evaporation heat transfer coefficient of R-290 and 600a is approximately $56.7{\sim}70.1$ and $46.6{\sim}59.7%$ higher, respectively. In comparison with experimental data and some correlations, the evaporation heat transfer coefficients are well matched with the Kandlikar's correlation regardless of a type of refrigerants and tube diameters.

• Journal of Bio-Environment Control
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• v.8 no.4
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• pp.281-287
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• 1999

In order to take a good look at effectiveness of cooling of Fog system and Pad-Fan system, we chose 49 farm households which were installed evaporative cooling system and 2 farm households which were installed Pad-Fan system and Fog system for a test. We execute the test on 29 households out of 49.6 households, which were installed Pad-Fan system, were able to use; however, 6 household out of 9 which were installed Fog system couldn't use it. The main reason was the clogged on nozzle. The cooling efficiency on Pad-Fan system was 77.4%, but it was very poor on Fog system. Since there are many problems on Fog system, we need more research on size of fog, the location of nozzle, control of Fog systems.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.9
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• pp.2189-2194
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• 2009

The automatic hot gas by-pass technique is applied to control the capacity of refrigeration and air-conditioning system when operating at part load. In the scheme, the hot gas from the compressor is extracted and injected into the outlet of an evaporator through a hot gas by-pass valve. Thus, In this paper, the hot gas by-pass scheme for CO2 is discussed and analyzed on the basis of mass and energy conservation law. A comparative study of the schemes is performed in terms of the coefficiency of performance (COP) and cooling capacity. The operating parameters considered in this study include compressor efficiency, superheating degree, outlet temperature of gas cooler and evaporating temperature in the R744 vapor compression cycle. The main results were summarized as follows : the superheating degree, outlet temperature and evaporating temperature of R744 vapor compression refrigeration system have an effect on the cooling capacity and COP of this system. With a thorough grasp of these effect, it is necessary to design the compression refrigeration cycle using R744.

• Journal of agriculture & life science
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• v.46 no.3
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• pp.119-127
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• 2012

For the promotion of the evaporative cooling efficiency of hot air in greenhouse in summer, a fog sprayer consisted of a high volume spraying two-fluid nozzle with turbo fan and a blowing fan was set up at 2.2 m height from bottom of small glass greenhouse and tested to estimate the possibility of the greenhouse cooling. The mean droplet size and the volume sprayed by one of fog sprayer were $29{\mu}m$ and $160m{\ell}/min$. All the droplets sprayed and blown by the fog sprayer were evaporated within 2 m radius. The result from the cooling test that two sprayers set up in glass greenhouse of plane area $228m^2$ was represented lower cooling effect that the temperature and relative humidity of inside air of greenhouse were $28.8^{\circ}C$ and 87.5% when those of outside air of greenhouse were $30.2^{\circ}C$ and 81.2%. Through investigation of literatures and results of the cooling test, it was estimated that the water spraying rate of evaporative cooling of single span greenhouse with 50% light curtain and with air change rate of 1 volume/min was $10m{\ell}/min/m^2$ so that the inside air temperature may cool down $2{\sim}3^{\circ}C$ on the basis of $35^{\circ}C$ atmospheric temperature in summer of south korean area.

• Nuclear Engineering and Technology
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• v.22 no.4
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• pp.326-336
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• 1990

Recent experiments show the existence of spacer grid improves the heat removal from the fuel rods during the reflood phase of LOCA. The local heat transfer within and downstream of the grid is increased due to the earlier quenching than rod surface, shattering of the entrained droplets into smaller ones which can be more easily evaporated and enhanced turbulent effect. Therefore, the consideration of these phenomena is necessary for the DFFB regime which prevails above the water level during the reflood. In this paper, droplet breakup model at spacer grid has been developed and incorporated into RELAP5/MOD2. Verification calculations are carried out for FEBA tests which examine the thermalhydraulic performance of grid spacer during reflood.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.37 no.1
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• pp.52-56
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• 2001

A fundamental study on the cooling apparatus inshore fishing boat and its operation characteristics in sea water cooling system were performed experimentally. The circumstance is giving the blow against fisherman with incoming-decreasing and the difficulty of crew's supply and demand and management. In addition, the depression of the external situation such as the plan of EEZ(Exclusive Economic Zone) proclaim is forcing them into improving their fishing condition. By this international and domestic surrounding, the development of a cooling apparatus inshore fishing boat is demanded sincerely. We investigated load characteristics as the pilot plant operation characteristics estimation which is based on the development of cooling system and optimum cooling apparatus inshore fishing boat. These results provide useful informations which are applicable to an actual design and show the possibility of application to other fields.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.11-11
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• 2010

고도의 진공 환경을 요구하는 반도체 생산 라인에 적용되는 고진공 펌프는 주로 복합 분자펌프와 크라이오 펌프가 사용되고 있다. 이 중 크라이오 펌프는 극저온으로 냉각되는 냉각판에 기체 분자를 응축 또는 흡착시켜 기체를 제거하는 방식으로 복합 분자 펌프로 무게가 가볍고 증발 온도가 낮은 네온, 수소, 헬륨 기체 제거에 장점이 있다. 본 연구에서는 현재 상용화된 크라이오 펌프에 적용되는 GM 극저온 냉동기를 대체하기 위한 2단 GM형 맥동관 냉동기를 개발하여 기초 성능 시험을 수행하였다. 1단과 2단 모두 U-자형 형상으로 제작되었으며, 압력과 질량 유동 사이의 위상 조절을 위하여 오리피스 밸브와 이중 유입 밸브를 사용하였다. 개발된 맥동관 냉동기의 냉각 성능 목표는 1단(80 K)과 2단(20 K)에서 각각 45 W와 5 W이다. 기초 시험에서는 위상 조절용 밸브들의 개도와 작동 조건에 대한 냉각 특성과 부하 특성 시험을 수행하였다. 특히, 본 연구에서는 로터리 밸브 및 위상 조절 기구의 배치로 인해 고온부 형상이 복잡한 맥동관 냉동기를 크라이오 펌프로의 적용 편의성을 위하여 고온부 외형 구조를 단순화하였으며, 개발된 맥동관 냉동기와 기존에 크라이오 펌프에 적용되는 GM 극저온 냉동기를 비교, 고찰하였다.