• Aerospace Engineering and Technology
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• v.3 no.1
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• pp.103-108
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• 2004

The space environment is characterized such a severe condition as high vacuum and very low temperature. Since a satellite will be exposed such a space environment as soon as it goes into the its orbit, thermal vacuum test should be carried out to verify the performance of the satellite on the ground under the space environmental conditions. KARI has a thermal vacuum chamber with useful dimensions of ∮3.6m×L3m, in which KOMPSAT-1 and KOMPSAT-2 satellites were tested. But very large thermal vacuum chamber with useful dimensions of ∮8m×L10m has been needed to meet the future demand of large satellites. Generally, the thermal vacuum chamber can be divided into a vacuum system and a thermal system. Especially, a cryogenic system in the thermal system simulates very low temperature of -196℃ under the high vacuum condition. In this paper, we propose the new cryogenic system can be applied to the future large thermal vacuum chamber.

• Korean Chemical Engineering Research
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• v.44 no.6
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• pp.614-622
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• 2006

A Study on the characteristics of $Ta/Ta_2O_5/MnO_2$ capacitor applied $MnO_2$ by means of pyrolysis of manganese nitrate solution was carried out. Single phase of $MnO_2$ was obtained in the pyrolysis temperature range of 230 to $250^{\circ}C$ by TG/DSC analysis on manganese nitrate solution. Temperature of pyrolysis, concentration of manganese nitrate solution and the number of pyrolysis were selected for the basic parameters of embodying $MnO_2$ solid electrolyte and then the effects of these parameters on the characteristics of capacitor were estimated. The characteristics of capacitor pyrolyzed radiationally was superior to that of capacitor pyrolyzed convectionally on the basis of these optimized parameter conditions. It was verified that radiational pyrolysis formed smaller spherical $MnO_2$ particles than those of convectional one relatively and these facts resulted in forming uniform and dense solid electrolyte layer into the microporous sintered body of capacitor.

• Journal of the Korean Institute of Landscape Architecture
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• v.40 no.1
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• pp.1-11
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• 2012

Human thermal sensation based on a human energy balance model was analyzed in the study areas, the Changwon and Nanaimo sites, on clear days during thesummer of 2009. The climatic input data were air temperature, relative humidity, wind speed and solar and terrestrial radiation. The most effective factors for human thermal sensation were direct beam solar radiation, building view factor and wind speed. Shaded locations had much lower thermal sensation, slightly warm, than sunny locations, very hot. Also, narrow streets in the Nanaimo site had higher thermal sensation than open spaces because of greater reflected solar radiation and terrestrial radiation from their surrounding buildings. Calm wind speed also produced much higher thermal sensation, which reduced sensible and latent heat loss from the human body. By adopting climatic factors into landscape architecture, the human thermal sensation analysis method promises to help create thermally comfortable outdoor areas. The method can also be used for urban heat island modification and climate change studies.

• Journal of the Korean Institute of Gas
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• v.20 no.5
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• pp.17-26
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• 2016

Chemical plants and oil gas refinery facilities are intrinsically vulnerable to industrial hazards, such as explosion or fire. Especially, the fire is extremely dangerous to facility structures and plant personnel because of direct flame, radiant heat and smoke. In addition, it has the ripple effect of destroying infra-structures and polluting the environment. In an effort to tackle these potential industrial risks, the procedure of FRA techniques in chemical plants were investigated. The main focus was put on the time variation of physical properties of the main building, i.e. control rooms, warehouses and electrical substations, from a direct flame contact and radiant heat. The deformation of a building due to fire was monitored and modeled with respect to time variable. A variety of case studies, domestic and abroad, was tested in the model to verify the FRA procedure. The developed model was proven to be highly effective to reduce the possible risks at chemical plants. An accurate accident frequency prediction and damage quantification was made by the developed model.

• Fire Science and Engineering
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• v.18 no.4
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• pp.64-71
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• 2004

This paper describes the result of the pump room fire analysis of the nuclear power plant using CFAST fire modeling code developed by NIST. The sensitivity studies are performed over the input parameters of CFAST: the constrained or unconstrained fire, Lower Oxygen Limit (LOL), Radiative Fraction (RF), and the opening ratio of the fire doors. According to the results, a pump room fire is the ventilation-controlled fire, so it is adequate that the value of LOL is 10% which is also the default value. It is anlayzed that the Radiative Fraction does not affect the temperature of the upper gas layer. It is appeared that the integrity of the cable located at the upper layer is maintained except for the safety pump at the fire area and the Conditional Core Damage Probability (CCDP) is 9.25E-07. It seems that CCDP result is more realistic and less uncertain than that of Fire Hazard Analysis (FHA).

• Journal of the Korean Institute of Gas
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• v.18 no.3
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• pp.67-74
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• 2014

Buried natural gas pipelines in densely populated urban areas have serious hazards of property damages and casualties generated by release, dispersion, fire and explosion of gas caused by outside or inside failures. So as to prevent any accident in advance, managers implement danger management based on quantitative risk analysis. In order to evaluate quantitative risk about buried natural gas pipelines, we need calculation for radiant heat and pressure wave caused by calculation for release rate of chemical material, dispersion analysis, fire or explosion modeling through consequence analysis in priority, in this paper, we carry out calculation for release rate of pressured natural gas, radiant heat of fireball based in accident scenario of actual "San Bruno" buried high pressured pipelines through models which CCPS, TNO provide and compare with an actual damage result.

• Journal of Energy Engineering
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• v.14 no.1
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• pp.24-29
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• 2005

In order to evaluate the performance of fire-protection foams used to protect structures from heat and fire damages, the thermal characteristics of them are experimentally investigated. This research focuses on the destruction of a fire-fighting foam subjected to heat radiation. A simple repeatable test apparatus for fire-protection foams subjected to fire radiation is developed. It involves a foam generation equipment, a fire source for heat generation, repeatable test procedures, and data acquisition techniques. Results of the experimental procedure indicated that each thermocouple within the foam responded in a similar manner and gradually to a temperature of 115℃～20℃. At this point, each trace generally rises to a temperature of approximately 90℃. The temperature gradient in the foam as time passes increases with increasing the foam expansion ratio. In addition, it is found that the temperature gradient along the foam for depth decreases with increasing the foam expansion ratio.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.5
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• pp.952-964
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• 1992

The interaction of natural convection and radiation heat transfer in a two dimensional square enclosure containing absorbing, emitting and linear anisotropically scattering gray medium is numerically analyzed. P-1 and P-3 approximation is introduced to calculate radiation heat transfer. The effects of scattering albedo, wall emissivity, scattering anisotropy, and optical thickness on the characteristics of the flow and temperature field and heat transfer are investigated. Temperature and velocity profiles depend a great deal on the scattering albedo, and the importance of this effect increases with decrease in albelo. Planck number is another important parameter in radiation heat transfer. The increase in scattering albedo increases convection heat transfer and decreases radiation heat transfer at hot wall. However, the increase in scattering albedo decreases both convection and radiation heat transfer at cold wall. The increase in optical thickness decreases radiation heat transfer. The scattering anisotropy has important effects on the radiation heat transfer only. The highly forward scattering leads to an increase of radiation heat transfer whereas the highly backward scattering leads to an decrease of radiation heat transfer. The effect of scattering anisotropy decreases when reducing the wall emissivity.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1997.11a
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• pp.10-11
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• 1997

고체 추진제를 사용하는 추진 시스템을 개발하는데 가장 커다란 문제로 인식되고 있는 것은 추진제의 연소 특성을 이해하는 일이다. 그 중에서도 연소실의 압력 진동과 추진제 벽면으로 흡수되는 복사 열전달에 의한 연소율(burning rate)의 변화로 인하여 발생하는 연소 불안정에 대한 이해는 아직도 완전히 규명되지 않고 있다. 고체 추진제의 연소 불안정에 대한 이론적 해석은 준-정상 1차원 해석(Quasi-Steady Homogeneous One-Dimension) 방법에 의하여 단순화된 지배방정식을 해석하는 것이 일반적으로 잘 알려져 있는 방법이다. 이 가정은 고체 추진제가 연수되는 영역을 두께가 매우 얇은 영역의 표면반응영역(surface reaction layer)과 화학반응이 없는 응축상태영역(condensed phase zone) 그리고 기체상태의 연료와 화염이 존재하는 기체상태영역(gas phase zone) 등의 3영역으로 구분하며, 기체상태영역에서 발생하는 교란에 대한 응축상태영역의 반응시간 크기(response time scale)가 매우 크기 때문에 응축상태영역의 반응은 준 정상적으로 일어난다고 가정하는 것이다.그러나, 연소실의 온도가 $3000^{\circ}K$ 정도의 높은 온도이어서 복사 열전달에 의한 고체 추진제의 가열이 중요한 열전달 방법으로 작용하게 되므로 이를 무시한 이론적 해석은 물리적인 중요성이 약하여질 수밖에 없다. 본 연구에서는 기체영역으로부터 전달되는 복사 열전달은 투명(transparent)한 표면반응영역을 통과하여 응축상태영역에서 모두 흡수되며 추진제 표면에서의 복사열방출(emission)을 고려하였다. 또한 연소불안정 현상을 해석하기 위하여 표면반응영역에서의 경계조건은 선형교란량으로 대치하는 Zn(Zeldovich-Novozhilov) 방법을 사용하였다. 이 방법은 기체상태영역에 대한 구체적인 해석없이도 연소불안정 현상을 해석할 수 있는 장점이 잇다. 즉 응축상태영역에서의 연소율과 표면온도는 각각 기체영역으로부터 전달되는 온도구배와 연소압력, 그리고 복사 열전달의 함수관계이므로 선형교란에 의한 추진제표면에서의 교란경계조건을 얻을 수 잇으며, 응축영역의 교란지배방정식과 함께 사용하여 압력교란과 복사 열전달의 교란에 대한 연소율의 교란 증감 여부를 판단하여 연소 불안정 현상을 해석할 수 있다.

• Journal of Astronomy and Space Sciences
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• v.21 no.4
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• pp.467-480
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• 2004

It is very important to eliminate thermal background radiation for the near infrared camera system such as KAONICS (KAO Near Infrared Camera System). Thermal background radiations which come from window and cryostat wall influence IR detector and decrease IR system performance. Therefore the cold box which contains optics and detector housing must be cooled down to eliminate thermal background radiation. We carried out quantitative analysis to determine internal cooling temperature to reduce thermal noise in the J, H, Ks, and L bandpass. Additionally, we estimated the incoming heat load and then chose the cryocooler adequate to KAONICS's requirements. The cooling time and the final cooling temperature of the cold box were calculated. These results were also implemented to the system design.