• Proceedings of the KAIS Fall Conference
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• 2005.05a
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• pp.75-78
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• 2005

본 논문은 CPU의 수냉식 쿨러 자켓에 대하여 CFD(computational fluid dynamics) 해석을 수행하여 내부면적이 큰 쿨러 자켓의 효율이 어느 정도 좋은 지를 내부면적이 작은 쿨러 자켓과 비교 분석한다. 쿨러 자켓이 냉각수와 열 교류를 원활히 할 수 있도록 쿨러 자켓의 온도분포를 통하여 적절한 형상을 설계하여 CPU 수냉식 쿨러 자켓의 제작시 설계 자료로 이용하고자 한다.

• Proceedings of the Korean Society for Bio-Environment Control Conference
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• 2003.10a
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• pp.217-221
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• 2003

• Nuclear Engineering and Technology
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• v.40 no.3
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• pp.239-250
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• 2008

If there is a water flow with a range of temperature inside a pipe, the wanner water tends to float on top of the cooler water because it is lighter, resulting in the upper portion of the pipe being hotter than the lower portion. Under these conditions, such thermal stratification can play an important role in the aging of nuclear power plant piping because of the stress caused by the temperature difference and the cyclic temperature changes. This stress can limit the lifetime of the piping, even leading to penetrating cracks. Investigated in this study is the effect of thermal stratification on the structural integrity of the pressurizer surge line, which is reported to be one of the pipes most severely affected. Finite element models of the surge line are developed using several element types available in a general purpose structural analysis program and stress analyses are performed to determine the response characteristics for the various types of top-to-bottom temperature differentials due to thermal stratification. Fatigue analyses are also performed and an allowable environmental correction factor is suggested.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.25 no.4
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• pp.173-179
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• 2013

Middle-sized $CO_2$ water heater having compressor power of 7.45 kW was designed, and its performances were experimentally tested. Besides, optimum design of the $CO_2$ water heater was conducted by cycle simulation. When ambient temperature of $7^{\circ}C$ and hot water outlet temperature of $80^{\circ}C$ the $CO_2$ water heater showed the COP of 3.2. As hot water temperature increased the COP is getting decreased due to significant increase of compressor power consumption compared to increasing rate of heating capacity. When ambient temperature increased from $-3^{\circ}C$ to $12^{\circ}C$ the COP increased by 30%. The optimum components design of a gas cooler, an internal heat exchanger, and an evaporator were conducted, and the experimental correlation between amount of EEV opening and ambient temperature, and hot water temperature was suggested.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.1
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• pp.46-51
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• 2009

In this work, the experimental investigation was carried out to evaluate the heat transfer performance on the shell side of shell-and-plate finned tube heat exchanger with three different tube numbers(9, 13 and 19). Oil flowing on the shell side was cooled by cold water flowing inside the tubes. A shell-and-tube heat exchanger of an oil cooler consisted of one shell pass and two tube passes with the inner tube diameter of 8.82 mm and the tube length of 575 mm. Mass flow rate was varied from 1.2 to $6.0\;m^3/h$ for oil and from 0.6 to $3.0\;m^3/h$ for cold water, respectively. From the experiment of shell-and-plate finned tube heat exchanger, the overall heat transfer coefficient of heat exchanger with 9 tubes was compared with that of 13 and 19 tubes. It was found that the heat transfer coefficients in shell side of heat exchanger with 9 plate finned tubes showed averagely 1.8 times and 2.3 times higher than those of 13 and 19 tubes, respectively.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.9
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• pp.1021-1026
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• 2014

In this paper, among various systems applying hot-gas bypass control, outdoor temperature, outlet temperature of water cooler, superheating and subcooling degree, which are the factors affecting the performance of the system bypassing hot-gas to evaporator inlet were analyzed. The main results were summarized as following. Frist of all, performance of refrigeration system bypassing hot-gas to evaporator inlet was affected by outdoor temperature, outlet temperature of water cooler, superheating and sub cooling degree. Thus, providing basic planning date of refrigeration system obtained through optimization of variables is expectable. Thus, providing the basic design data of refrigeration system can be offered by performing the optimization of these variables. Also, the feasibility of this refrigeration system proposed in this paper was obtained by analyzing operating characteristics of the system bypassing hot-gas to evaporator inlet.

• Proceedings of KOSOMES biannual meeting
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• 2003.11a
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• pp.175-180
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• 2003

Water temperature data of National. Fisheries Research and Development Institute (NFRDI) during periods of 19m to 2002 were analyzed to investigate the effect of the water temperature on catches of anchovy and laver in the eastern part of the Southern Waters of Korea The annual catches of anchovy and laver increased gradually although they showed fluctuations each year. Our findings indicated tint the catches cf anchovy and laver were controlled by various oceanographic conditions, mainly water temperature. The appearance of cooler sea surface water, warmer water at 0 to 20 m depth, and bottom water of about $15^{\circ}C$ caused relatively lower catches.

• 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 Advanced Marine Engineering and Technology
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• v.34 no.1
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• pp.195-201
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• 2010

In this paper, a cooling system of high-power propulsion motor with Energy Saving System(ESS) is described. Normally, the cooling system for ship consists of fresh water pump, sea water pump, 3-way valve and cooler. In the cooling system, F.W(Fresh Water) and S.W(Sea Water) pump is operated on rated rpm, and the 3-way valve is controlled for preventing over-cooling. So, the consumption power of pump's motor is changed according to a sea water temperature. In the proposed cooling system, F.W. pump and S.W pump is controlled by inverter, and it is can be reduced the consumption power. Also, it is proved with simulation.

• 한국석유지질학회:학술대회논문집
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• spring
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• pp.22-28
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• 1998

Twenty species of calcareous nannofossils belonging to 11 genera are identified from the Seoguipo Formation in Cheju island, Korea. On the basis of the marker species, the Seoguipo Formation is biostratigraphically assigned to the Pseudoemiliania lacunosa Zone (NNl9), which corresponds to the combined zones of Emiliania annula - Emiliania ovata (CN13a-CN14a) of latest Pliocene and Early Pleistocene. Generally, cold-water species is dominant in the lower part, whereas warm-water one in the upper part. This is interpreted the palaeoceanographic condition has changed from cooling to warm phase. The change in floral composition and abundance of specific species allows the recognition of 4 ecostaratigraphic units in the Seoguipo Formation and the migration of oceanographic frontal boundary. According to nannofossil distribution in the study area, the position of an oceanographic boundary between warmer water and cooler water appeared to have oscillated north-south over the Korea Strait and Cheju island in response to glacial and interglacial cycles. The geologic time of the interpreted paleoceanographical changes determined by nannofossil biochronology is well agreed with the results obtained from the Japan Sea (East Sea) and Japan-Sea side of Japan.