• Journal of the Korean Institute of Intelligent Systems
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• v.22 no.6
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• pp.780-785
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• 2012

Wind energy is currently the fastest growing source of renewable energy used for electrical generation around the world. Generally, wind turbine systems are designed to be operated for twenty years long, Therefore, various faults in the wind turbine system inevitably occur during their long term period of operation. Especially, rotor shaft, gear-box and generator are installed inside of nacelle, furthermore, some cooling systems for normal operation of these devices are also required. If these cooing systems have failed in their operation, it is impossible for the entire system to be operated normally. In this work, IR(Infra Red) camera based fault detection system for the preventive detection of various cooling systems faults is proposed. To verify the applicability of the proposed system, physical implementation is embodied and various experiments are carried out.

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.2
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• pp.87-95
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• 2018

The pressure loss in a cooling channel was investigated by conducting a numerical analysis, which was performed with a different channel angle in the axial direction, velocity of flow, and diameter of channels. The pressure loss did not change much with respect to the different channel angle. However, the pressure loss tended to decrease if the diameter of the channel increased and the velocity of the flow decreased. The results were quantified by a nondimensional method and compared to an existing experimental equation to validate them. The data obtained by this study would be helpful in the design process of a cooling channel considering the pressure loss.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.29 no.1
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• pp.24-31
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• 2019

The current study demonstrates an efficient procedure to create ingots from $Al_2O_3$ powder using the skull melting method to use these ingots as a starting material in conventional methods for growing synthetic single-crystal sapphire. Dimension of the cold crucible was 24 cm in inner diameter and 30 cm in inner height, 15 kg of $Al_2O_3$ powder was completely melted within 1 h at an oscillation frequency of 2.75 MHz, maintained in the molten state for 3 h, and finally air-cooled. The areal density and components of the cooled ingot by parts were analyzed through scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS). The areal density and $Al_2O_3$ content of the ingot were related to the temperature distribution inside the cold crucible during high-frequency induction heating, and the area with high temperature was high tends to be high in areal density and purity.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.10
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• pp.885-891
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• 2010

Thermal management is important for enhancing the performance and durability of polymer electrolyte membrane fuel cells (PEMFCs) and is taken into account in the design of PEMFCs. In general, cooling pates with circulating liquid coolant (water) are inserted between several unit cells to exhaust the reaction heat from PEMFCs. In this study, computational fluid dynamics (CFD) simulations were performed to characterize the uniform cooling performance of parallel multipass serpentine flow fields (MPSFFs) that were used as coolant flow channels in PEMFCs. The cooling performances of conventional serpentine and parallel flow fields were also evaluated for the purpose of comparison. The CFD results showed that the use of parallel MPSFFs can help reduce the temperature nonuniformity, and thus, can favorably enhance the performance and durability of PEMFCs.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.4
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• pp.429-435
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• 2015

A bellows is an important temperature control component in a Joule-Thomson micro-cryocooler. It is designed using a very thin shell, and the inside of the bellows is filled with nitrogen gas. The bellows is made of a nickel-cobalt alloy that maintains its strength and elastic properties in a wide range of temperatures from cryogenic to $300^{\circ}C$. The pressure of the gas and the volume within the bellows vary according to the temperature of the gas. As a result, the bellows contracts or expands in the axial direction like a spring. To explore this phenomenon, the deformation of the bellows and its internal volume must be calculated iteratively under a modified pressure until the state equation of the gas is satisfied at a given temperature. In this paper, the modified Benedict-Webb-Rubin state equation is adopted to describe the temperature-volume-pressure relations of the gas. Experiments were performed to validate the proposed method. The results of a numerical analysis and the experiments showed good agreement.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.05a
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• pp.9-12
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• 2003

A cooling performance analysis has been made in the 8-channel calorimeter based on sub-scale KSR-III engine. Three-dimensional heat transfer analysis in cooling channels has been performed using the heat flux distribution through the chamber wall predicted from axi-symmetric compressible flow inside the combustion chamber. The heat flux distribution was verified against the published literature. Presented for the development and operation of the calorimeter are the coolant pressure drop, coolant temperature rise and the maximum chamber wall temperature.

• The Korean Journal of Rheology
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• v.6 no.1
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• pp.10-19
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• 1994

에폭시수지와 CFRP 복합체 구조물의 경화공정 중에 발생하는 잔류응력은 구조물의 기계적물성에 영향을 미친다. 따라서 잔류응력을 낮추기 위해 여러 가지 방법들이 발표되고 있다. 이연구에서는 잔류응력을 낮추는 방법으로 잔류응력의 발새mechanism을 이해하고 반 응속도식과 여러 가지 기초물성을 기초로 한 computer simulation pro-gram을 이용하여 에 촉시수지와 복합체 구조물의 잔류응력을 최소화하는 경화공정을 찾는 연구를 진행하였다. 경화과정에서는 대부분의 경화온도가 구조물의 유리전이온도보다 높기 때문에 잔류응력이 발생하지 않고 대부분의 잔류응력은 냉각과정에서 발생하였다. 잔류응력을 정량화하는 방법 으로 구조물의 표면이 유리전이온도에 도달하였을때 내부 비체적분초를 상대적인 잔류응력 이라 간주하였다. 컴퓨터모사에 의해 최종경화온도와 냉각속도를 바꾸면서 잔류응력을 모사 한 결과 최종경화온도가 낮을수록, 냉각속도가 작을수록 잔류응력이 작게 발생하였다.

• Journal of the Korean Magnetics Society
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• v.10 no.1
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• pp.7-10
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• 2000

The soft magnetic properties of Co-based amorphous alloy have been studied as a function of cooling condition after annealing. The F&W treatment (furnace cooling to 25$0^{\circ}C$ then water quenching) could increase 60~10$0^{\circ}C$ more the initial permeability than those of furnace cooled or water quenched alloys. These results are investigated in terms of thermal stress and ordering of magnetic ion pairs.

• Proceedings of the Korean Society for Bio-Environment Control Conference
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• 1999.11a
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• pp.164-168
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• 1999

온실은 동절기 난방을 주목적으로 설비되어 년중 작물재배 시는 하절기 온실내부 온도가 필요이상으로 상승하여 실내온도가 35-4$0^{\circ}C$ 정도로 올라가는데 이러한 상태에서의 온도는 많은 작물의 생육적온을 벗어난 온도로서 고온장해를 나타낸다. 이 같은 문제점을 해결하기 위해 몇 가지 냉방방법이 알려져 있는데 에어컨 등과 같은 냉방장치를 이용한 기계적 냉각방식과 수분증발을 통한 증발식 냉각방식으로 대별되며 이중 기계적인 냉방방식은 설비나 유지관리 면에서 비용이 많이 들어 비경제적이고, 증발냉각 방식중에서도 Fan and Pad 법이 가장 효과가 좋은 것으로 알려져 있으나 이역시 설치 및 유지비가 많이 들고, vep의 탈부착이 어려워 고정시켜놓을 경우 동계 광투과에 방해가 되는 등의 문제가 많다. (중략)

• Proceedings of the Korean Society for Bio-Environment Control Conference
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• 2001.11a
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• pp.59-62
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• 2001

여름철 온실내 고온 문제를 해결하기 위해 이용되는 자연환기형 포그냉방은 환기가 충분치 못할 경우 온실 내부의 습도가 증가하여 증발 효율이 떨어지는 문제가 발생한다. 제습장치를 이용하여 온실 내부의 상대습도를 낮추면 증발 냉각 효율을 높일 수 있을 것으로 생각된다. 본 연구에서는 제습장치를 이용한 포그냉방 온실에 대한 CFD 모델을 개발하여 온실의 열환경 및 수분 환경을 분석하고자 한다. (중략)