• Journal of Advanced Marine Engineering and Technology
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• v.38 no.9
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• pp.1027-1031
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• 2014

Free cooling system is used to reduce energy consumption of cooling system. Free cooling system is consisted of cooling group and dry-cooler in which heat exchange of chilled water and out air is conducted. Although this system has an excellent energy saving effect in place having cooling load regularly, data or material of design for free cooling system is lacked. In this study, characteristics analysis of free cooling system is conducted through software HYSYS with changing some facts. The main result is following as : Dry-cooler capacity is influenced by out air temperature, required chilled water temperature and LMTD(Logarithmic Mean Temperature Difference) of heat exchanger. As out air temperature is more low, dry-cooler capacity become increased. in addition, as required chilled water temperature is more high and LMTD is more low, the out air temperature range is widened for using dry-cooler. If out air temperature is below $0^{\circ}C$, antifreeze need to be used because freeze and burst can be occurred. In case of South Korea, antifreeze of 34% of ethylene glycol concentration is proper. When compressor load of R22, R134a and R407C is compared, considering environmental regulation and energy consumption, R134a is best working fluid.

• Proceedings of KOSOMES biannual meeting
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• 2017.04a
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• pp.229-229
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• 2017

• 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 Society for Agricultural Machinery Conference
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• 2017.04a
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• pp.118-118
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• 2017

지구 온난화에 따른 환경변화로 인하여 최근 10년('02~'11)간 여름의 일수는 4일, 겨울 일수는 16일 각각 증가하였다. 현재 육계사 내의 고밀도 밀집사육으로 인하여 고온스트레스로 하절기 육계의 폐사율이 증가하고 있는 실정이다. 2016년 폭염으로 닭 406.1천수, 오리 15.7천수, 메추리 70천수, 돼지 8천수가 폐사하였다. 이에 혹서기 가축이 약430만수가 폐사하였으며 피해 보상금액 128억원 소요되었다. 본 연구에서는 하절기 고온스트레스 경감과 폐사율 저감을 위해 계사 냉난방 공조와 냉온 음용수 급수를 병행할 수 있는 고효율 환경 개선 시스템을 개발하여 고온스트레스 저감 및 생산성 향상에 목적이 있다. 계사 냉난방 공조 및 냉온음용수 급수 병행 시스템 설계요인을 분석하고 냉난방 공조부하, 냉온수 생산 부하를 고려한 시스템 용량 산정하고 히트펌프, 축열조, 냉난방 및 냉온수 분배장치 등 구성요소로서 공조 및 냉온음용수 급수시스템을 설치하였다. 시스템 용량은 공기-물 히트펌프(10kW,1대), 축열조(10톤), 음용수조(2톤), 열교환기(열교환량,5만kcal/h), 물순환펌프(250W,2대) 및 팬코일유닛(1만kcal/h,4대)으로 시스템 모니터링 및 제어 시스템 개발하여 계사 내 환경, 시스템 성능에 대한 실시간 모니터링을 통하여 저장하였다. 조사항목으로 위치별 온습도, 체중, 사료섭취량, 페사율 등을 조사 분석하였다. 연구결과 계사의 내부온도는 시험구에서는 평균 $25.3^{\circ}C$를 나타내었고 대조구에서는 평균 $28.1^{\circ}C$로서 $2.8^{\circ}C$ 높게 나타났으나 상대습도는 시험구 76.2%, 대조구 75.0%로 큰 차이가 없었다. 냉수급여에 따른 계사 높이별 내부온도는 상하의 온도차가 $4.5^{\circ}C$로 크게 차이가 났다. 육계의 음수량은 혹서기 냉수를 급여한 시험구에서 일일 23.2L, 대조구에서는 21.5L를 섭취하였다. 일일 사료섭취량은 냉수를 급여한 시험구에서 937g, 대조구에서는 725g을 섭취하였다. 사료섭취량은 냉수를 급여한 시험구가 212g 많이 섭취하였으며 사료요구율은 시험구는 1.86, 대조구는 1.91로서 시험구가 낮게 나타났다. 체중은 냉수를 급여한 시험구가 359g 많았으며 증체량은 냉수를 급여한 시험구에서 495g, 대조구에서는 392g으로 나타났다. 폐사율은 냉수를 급여한 시험구에서 84%가 폐사율을 줄일 수 있었다.

• Korean Journal of Remote Sensing
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• v.39 no.6_1
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• pp.1235-1243
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• 2023

This study proposes the detection algorithm for the cold water mass (CWM) along the eastern coast of the Korean Peninsula using sea surface temperature (SST) data provided by the Korea Institute of Ocean Science and Technology (KIOST). Considering the occurrence and distribution of the CWM, the eastern coast of the Korean Peninsula is classified into 3 regions("Goseong-Uljin", "Samcheok-Guryongpo", "Pohang-Gijang"), and the K-means clustering is first applied to SST field of each region. Three groups, K-means clusters are used to determine CWM through applying a double threshold filter predetermined using the standard deviation and the difference of average SST for the 3 groups. The estimated sea area is judged by the CWM if the standard deviation in the sea area is 0.6℃ or higher and the average water temperature difference is 2℃ or higher. As a result of the CWM detection in 2022, the number of CWM occurrences in "Pohang-Gijang" was the most frequent on 77 days and performance indicators of the confusion matrix were calculated for quantitative evaluation. The accuracy of the three regions was 0.83 or higher, and the F1 score recorded a maximum of 0.95 in "Pohang-Gijang". The detection algorithm proposed in this study has been applied to the KIOST SST system providing a CWM map by email.

• Journal of Energy Engineering
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• v.8 no.2
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• pp.333-340
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• 1999

A numerical study of turbulent condensing vapor jet submerged in subcooled liquids has been conducted. A physical model of the process is presented employing the locally homogeneous flow approximation of two phase flow in conjunction with a $\kappa$-$\varepsilon$-g model of turbulence properties. In this model the turbulence is represented by differential equations for its kinetic energy and dissipation. A differential equation for the concentration fluctuations is solved and a clipped normal probability distribution function is proposed for the mixture fraction. Effects of steam mass flux, pool temperature and nozzle internal diameter on the condensing vapor jet are also analyzed. The model is evaluated using existing data for turbulent condensing vapor jets. The agreement between the predictions and the available experimental data is good.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.6 no.1
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• pp.1-7
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• 2010

In this paper, an experimental study on the cooling operation characteristics for different entering water temperatures in geothermal heat pump system are carried out by using Lab VIEW system program Set-point temperature controls for cooling water and supply air temperatures is applied to analyze the energy consumption and control performances. As a result, the system responses show that different entering water temperatures(EWT) effect greatly on the energy consumption and system COP.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2004.05a
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• pp.253-258
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• 2004

21C 정보화시대를 맞이하여 반도체 산업이 급속하게 발전함에 따라 컴퓨터를 활용한 효율성이 높은 유틸리티 관리 시스템(New Utility Management System) 기술이 중요시되는 추세이다. 본 연구에서는 유틸리티 관리시스템의 한 부분인 냉수 시스템에 대해 정상상태 유동해석을 통하여 각 구성 요소에서의 유량 및 압력, 온도를 제공할 수 있는 컴퓨터해석시스템을 구현하였다. 효율성 증대를 위해 펌프 위치에 따른 시스템 변화를 파악하여 시스템에 영향을 크게 미칠 수 있는 펌프 즉, 가동하면 효율적인 펌프를 결정하였으며 최적의 리턴라인(Return Line) 위치를 설계하였다. 이 결과는 운전 및 관리의 효율성 증대와 에너지 절감을 위하여 매우 유익한 활용이 가능하다.

• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.2
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• pp.371-378
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• 2021

In this study, in order to analyze the spatial distribution of cold water occurred in the Southeast Sea of Korea, the K-means clustering method was used to analyze the ocean observatory buoy of Gori and Yangpo and GHTSST Level 4 from 2016 to 2018. The buoy data was used to identify the change in sea water temperature and the cold water occurrence at Gori and Yangpo in the Southeast Sea. As a result, the sea water temperature of Gori and Yangpo decreased equally at the cold water occurrence. Therefore, the reciprocal of the sea water temperature and the variance of SST were compared to see the changes of SST when the cold water occurs. When the reciprocal of the sea water temperature increases, the dispersion of SST also increases. Through this, it can be seen that there is a change in the water temperature distribution of SST in the sea when the cold water occurs. After that, K-means clustering was used to classify the cold water. After analyzing the optimal K value for clustering by using the Elbow method, it was possible to classify a region with cold water. Through this, it is estimated that the spatial distribution and diffusion range of the cold water, and it can be estimated and used in future studies to identify damage caused by the cold water and predict spatial spread.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.31 no.3
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• pp.359-371
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• 1998

The cold water event near Gampo-Ulgi coast in summers between 1987 and 1994 are studied using sea surface temperature records at the coastal stations, ocean winds measured by SSM/I and AVHRR SST images. The response time of the cold water events by upwelling is less than two days and surface cold water expands up to the Ulleung Island. An analysis of 61 upwelling favorable winds indicates that the surface water temperature drops more than $1^{\circ}C\;in\;80\%$ of the south-westerly wind events. The linear correlation coefficient between wind impulses and the maximum temperature drops is good (0.6). It is found that the major cause of the cold water events is the along-shore wind in summer. The bottom topography and off-shore direction of the East Korean Warm Current by the potential vorticity conservation near Gampo coast also contribute the formation of the cold water along the southeast coast of Korea.