• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.451-454
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• 2003

The Oil Coolers is very important unit for the stable thermal performance in machine tools, semiconductor equipments and high precision measuring systems. To select a proper oil cooler for the temperature control of core unit in a machine, not only cooling ability but also static and dynamic sensitivity of temperature sensors are considered. In this paper, the relationship between cooling ability and inflow oil temperature is identified. The cooling ability is increased with the increase of inflow oil temperature. The oil temperature control errors of a cooler are influenced by mainly sensitivity of temperature sensors and heating velocity in a machine. The validity of error cause analysis for temperature control is proved by real cooling experiments with inflow and outflow temperature sensors.

• Transactions of the Korean hydrogen and new energy society
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• v.32 no.6
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• pp.642-648
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• 2021

In this paper, an experimental study was conducted on the performance of the cooling tower. In order to improve reliability in the cooling tower performance test, the measurement uncertainty of the instrument was estimated. Measurement uncertainty refers to the uncertainty of a measurement, estimates the range in which the expected value of the measurement can be within a certain confidence level, and suggests a range in which the measured representative value is incorrect. Therefore, the measurement result of the performance experiment is not an actual value, but a reasonable estimated value. The measurement uncertainty for the test was calculated and the measured results were presented.

• Journal of the Korean Society of Propulsion Engineers
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• v.13 no.1
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• pp.10-18
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• 2009

Numerical simulation has been performed in this study to investigate the capabilities of turbulence modeling schemes on estimating the film cooling at a referenced parallel wall jet-nozzle configuration. Also a additional simulation has been performed for film cooling under 2-dimensional axis symmetry conditions at a parallel wall jet-nozzle configuration. It was concluded that the best turbulence model is the standard $k-{\epsilon}$ model with enhanced wall functions. Also a additional simulation showed the film cooling characteristics that are resonable physically.

• Journal of Energy Engineering
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• v.14 no.4 s.44
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• pp.232-240
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• 2005

In this study, the IAEA Benchmark problems far HTR-10 and HTTR RCCS were assessed in order to assess the applicability of MARS code, a thermal-hydraulic safety analysis code developed for water reactors. The calculated results were compared with those or THERMIX, THANPACST2 code, and available experimental data. The calculated results showed generally good agreements with those obtained by the THERMIX code and THANPACST2 code. Deviations were analyzed to be originated from the simplification of complicated geometry and from the modeling capability of heat transfer characteristics in the HTGR components such as water cooler and air tooler. Especially, it was found that the radiation heat transfer in the reactor cavity played an important role in the after heat removal in the RCCS. Thus, it is concluded that MARS code can be successfully applied to the calculation of the RCCS cooling capability of the HTGR in this study.

• 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.

• Journal of the Korean Society of Propulsion Engineers
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• v.15 no.1
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• pp.69-75
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• 2011

Firing tests have been carried out for a technology demonstration model of 75-tonf-class combustor which is to be used on the liquid rocket engine of a Korean space launch vehicle. Firing tests were done at 50% of the nominal flow rate because of incapability of the test facility and limit of the test bed strength. Through the low pressure firing tests of 75-tonf-class channel cooling thrust chamber, operability and stability at the ignition and combustion phases were confirmed. Additionally it was foreseen that the 75-tonf-class thrust chamber would satisfy the performance requirements.

• Proceedings of the Korean Nuclear Society Conference
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• 1997.10a
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• pp.387-391
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• 1997

냉각재중의 방사능을 띤 성분 중에는 이온교환기에서 제거가 가능한 이온성분과 함께 필터에 의해서 주로 제거되는 입자성 물질로 존재한다. 운전중의 냉각재내 방사성 부식생성물의 물리적 조성 분포 측정 결과에 따르면 90%이상이 0.45$mu extrm{m}$필터에 의해 제거되는 입자성 물질로 구성되어 있다. 이로 인해 새수지 충전후 얼마 사용하지 않은 탈염기의 제염계수가 탈염기에서 완벽한 제거가 어려운 입자성 부식생성물로 인해 10이하를 나타낼 수 있다. 1차계통에 쓰이는 수지의 성능검사를 위해 사용하고 있는 현재의 제염계수 측정법은 다음과 같은 두가지 이유로 완벽하지 않음을 알 수 있다. 첫째, 냉각재중의 방사능을 띤 성분중에는 이온교환기에서 제거가 가능한 이온성분과 함께 필터에 의해 제거되는 입자성 물질도 함께 존재하므로 탈염기의 제염계수 측정 절차는 입자성 물질을 배제한 후 측정해야 하며, 특히 수치 교체를 결정하기 위한 제염계수 측정시에는 여과된 여액으로 방사능 농도를 측정하는 것이 바람직하다. 둘째 운전중인 냉각재의 시료중에는 핵분열 수율이 높고 핵연료봉 손상부위로 유출이 용이한 불활성 기체핵종들이 많이 존재하며, 탈염기 후단에서 채취한 시료중에도 많이 존재하고, 시료 이송과 방사능 측정동안의 짧은 시간동안에도 계속 붕괴반응함으로서 새로 생긴 핵종으로 인해 마치 탈염기의 제거능이 낮은 것으로 오판될 수 있다. 이러한 측정 오차인자를 고려하여야 1차계통 탈염기의 교환능력을 정확히 판정할 수 있다.

• 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 the Korean Vacuum Society Conference
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• 2015.08a
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• pp.93.1-93.1
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• 2015

근래 디스플레이 분야에서 OLED가 시장을 주도하면서 이 공정에 가장 적합한 진공펌프로 크라이오 펌프가 주목을 받고 있다. 화소 형성 공정에 사용되는 유기물이 수분에 취약하기 때문인데, 크라이오 펌프가운데서 특별히 수분만 집중적으로 배기할 수 있는 워터펌프(CWP or cold trap)가 각광받고 있다. 이에 HM GVT는 중소기업청 중소기업개발지원사업의 일환으로 진행된 2014년도 구매조건부 신제품 개발사업에 선정되어 '극저온 G-M냉동기를 이용한 대용량 Cold Trap개발' 과제를 수행하면서 32인치 급으로 수분에 대해서 30,000 [L/s] 이상의 배기속도를 가지는 대형 CWP를 개발하고 있다(수요처: (주)아바코). 통상적으로 흡기구가 30인치라면 수분 배기속도는 대략 65,000 L/s에 이르고 200 W 냉각능력이면 최대 수분 분압 0.008 mbar에서 작동시킬 수 있다. 따라서 1차년도의 목표는 큰 배기용량과 대형 사이즈의 CWP를 개발하기 위해 80 K에서 200 W 이상의 냉동능력을 보유한 단단 G-M 극저온냉동기를 선행 개발하는 것이다. 이에 현재 최대 냉동능력 80 K에 130 W의 냉동능력을 가지는 HPS055모델을 이용하여 다양한 예비시험들을 수행하여 최적의 설계인자들을 도출하였고 이를 근거로 80 K에서 200 W 이상의 냉동능력을 가지는 HPS80200모델을 설계 및 제작, 성능시험을 수행하였다. 이에 국내 최초로 80 K에서 200 W의 냉동능력을 가지는 단단 G-M냉동기를 개발하였고 설계 및 제작에 대한 원천기술을 확보할 수 있었다.

• Fire Science and Engineering
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• v.23 no.6
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• pp.57-65
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• 2009

Fire suppression tests are carried out for a train car using water mist systems. Three kinds of fire scenario applied to the real-scale train car are a surface fire representing car combustibles, a oil pool fire pretending an oil spill and a blocked fire for evaluation of space-cooling capacity. Five fixedpressure water mist systems and one self-contained water mist system with nitrogen gas are used for fire suppression experiments. Almost water mist systems can extinguish effectively train car fires, and fire-control capability of the system is seen due to the space cooling.