• 한국항공우주학회지
• /
• 제49권5호
• /
• pp.407-415
• /
• 2021

인공위성의 부품은 발사 전 지상에서의 우주 궤도환경 하에서의 성능검증이 필수적이다. 본 논문은 열진공시험을 위한 위성 부품 및 소형 열진공챔버 간의 전도, 복사, 열손실 및 내부 발열의 열환경을 고려한 모델식을 설계하였다. 최근 한국항공우주연구원에서 수행된 열진공시험 20건의 시험데이터를 이용한 시스템 식별을 수행하였다. 시험품 기능시험의 발열이 일정하지 않는 경우를 제외하고 시스템 식별의 정확성을 확인함으로써 개발된 모델식이 유효함을 검증하였다.

• 한국기계가공학회지
• /
• 제14권2호
• /
• pp.67-74
• /
• 2015

In this study, analysis and experiments were carried out on temperature distributions and thermal deformations in a dry vacuum pump with vertical screws for safe operation. When a vacuum pump is working, it is necessary to get rid of the heat generated by the friction of bearings and the compression of air to prevent the vacuum pump from being damaged by interference between two screws and housing through thermal deformation. Additional cooling was proposed by using oil flow through the inner channel of the rotating axis for lower temperature control of the vacuum pump. Analysis and experimental results were compared in terms of temperature distribution and thermal deformation of the vacuum pump, and two sets of results matched reasonably well. These results for a dry vacuum pump with vertical screws can be used in similar model development and can minimize errors in design and manufacture by providing reasonably accurate prediction in advance.

• 한국태양에너지학회 논문집
• /
• 제35권1호
• /
• pp.61-68
• /
• 2015

The advanced counties effort to the supplement of the zero energy buildings for the global building energy saving. In the middle of the development of passive technology, the government has to effort to the energy saving of buildings by enhanced performance of the window thermal insulation. By the method of enhanced performance of window thermal insulation, the use of vacuum double glazing saves the energy consumption in building. This glazing has low U-value(heat transmission coefficient) than normal double glazing. The vacuum glazing enhanced thermal insulation performance by vacuum space of between the glass and glass. For this vacuum glazing, pillar maintain the space between glass and glass. But this structure cause the raising the heat transmission coefficient in pillar approaching glass. This study confirmed the U-value by the test method of thermal resistance for windows and doors. Also this study confirmed the variation of heat transmission coefficient by the structure of vacuum glazing. And this study measured the surface temperature of the vacuum glazing about pillar approaching glass and vacuum space in cool chamber and hot box. That result, this study confirmed U-value of $0.422W/m^2{\cdot}K$ of vacuum glazing. Also this study confirmed U-value of $0.300{\sim}0.422W/m^2{\cdot}K$ by various the structure of vacuum glazing. And this study confirmed the heat flow in pillar approaching glass.

• Current Photovoltaic Research
• /
• 제10권1호
• /
• pp.23-27
• /
• 2022

In this study, we investigate organic-inorganic halide perovskite solar cells with a vacuum thermal evaporated hole transporting layer (NPB/MoO_3-x). By replacing solution process based Spiro-MeOTAD with vacuum thermal evaporation based NPB/MoO_3-x, a thin hole transporting layer was implemented. In addition, parasitic absorption that may occur during the doping process was eliminated by excluding solution process doping. In a solar cell with a thin vacuum thermal evaporated hole transporting layer, the short-circuit current density (Jsc) increased to 23.93 mA/cm², resulting in the highest power converstion efficiency (PCE) at 18.76%. Considering these results, it is essential to control the thickness of hole transporting layer located at the top in solar cell configuration.

• 한국표면공학회지
• /
• 제50권6호
• /
• pp.460-464
• /
• 2017

As increasing thermal efficiency of the gas turbine, the performance improvement of thermal barrier coatings is also becoming important. Ytrria stabilized zirconia(YSZ) is the most popular materials for ceramic top coating because of its low thermal conductivity. In order to enhance the performance of thermal barrier coatings for hot sections in the gas turbine, suspension plasma spraying was developed in order to feed nano-sized powders. YSZ coatings formed by suspension plasma spraying showed better performance than YSZ coatings due to its exclusive microstructure. In this research, two YSZ coatings were deposited by suspension vacuum plasma spraying at 400 mbar and 250 mbar. Microstructures of YSZ coatings were analyzed by scanning electron image(SEM) on each spraying conditions, respectively. Crystalline structure transformation was not detected by X-ray diffraction. Thermal conductivity of suspension vacuum plasma sprayed YSZ coatings were measured by laser flash analysis. Thermal conductivity of suspension vacuum plasma sprayed YSZ coatings containing horizontally oriented nano-sized pores and vertical cracks showed $0.6-1.0W/m{\cdot}K$, similar to thermal conductivity of YSZ coatings formed by atmospheric plasma spraying.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2009년 춘계학술대회논문집
• /
• pp.142-147
• /
• 2009

COMS (Communication, Ocean and Meteorological Satellite) is a geostationary satellite and has been developing by KARI for communication, ocean and meteorological observations. It will be tested under vacuum condition and very low temperature in order to verify thermal design of COMS. The test will be performed by using KARI large thermal vacuum chamber, which was developed by KARI, and the COMS will be the first flight satellite tested in this chamber. The purposes of thermal balance test are to correlate analytical model used for design evaluation and predicting temperatures, and to verify and adjust thermal control concept. KARI has plan to use heating plates to simulate space hot condition especially for radiator panels such as north and south panels. They will be controlled from 90K to 273K by circulating GN2 and LN2 alternatively according to the test phases, while the shroud of the vacuum chamber will be under constant temperature, 90K, during all thermal balance test. This paper presents thermal modelling including test chamber, heating plates and the satellite without solar array wing and Ka-band reflectors and discusses temperature prediction during thermal balance test.

• 대한기계학회논문집B
• /
• 제30권8호
• /
• pp.772-779
• /
• 2006

Window is a critical component in the design of energy-efficient buildings. To minimize the heat loss, insulation performance of the glazing has to be improved. Manufacturing of vacuum glazing has been motivated by the possibility of making windows of very good thermal insulation properties for such applications. It is made by maintaining vacuum in the gap between two glass panes. Pillars are placed between them to withstand the atmospheric pressure. Edge covers are applied to reduce conduction through the edge. Accurate measurements have been made of the radiative heat transfer, the pillar conduction and the gas conduction using a guarded hot plate apparatus. Vacuum glazing is found to have low thermal conductance roughly below $1W/m^2K$. Among the heat transfer modes of residual gas conduction, conduction through support pillar and the radiative heat transfer between the glass panes, the last one is the most dominant to the overall thermal conductance. Vacuum glazing using very low emittance AI-coated glass has an overall thermal conductance of about $0.7W/m^2K$.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2009년도 춘계학술대회 논문집
• /
• pp.361-364
• /
• 2009

마이크로 인공위성에 적용가능한 마이크로 추력기를 개발하기 위해서는 우주환경을 모사할 수 있는 진공설비가 요구된다. 본 논문에서는 $10^{-5}\;torr$의 진공도를 목표로 정하고 진공설비를 구축하였고, $100{\sim}120\;km$의 고도를 모사한다. 장치 선정 및 실제 장치 구축 후 진공도 성능 실험을 수행하였고 저진공 펌프를 작동시켜 누센펌프의 멤브레인에 따른 특성연구를 진행하였다. 또한 향후 열진공챔버로의 전환을 위한 계획을 서술하였다.

• 항공우주기술
• /
• 제3권1호
• /
• pp.103-108
• /
• 2004

우주환경은 고진공 환경과 태양 복사열에 의한 고온 환경 및 극저온이 반복되는 가혹한 환경으로 특징지어 진다. 위성체는 지상에서 발사되어 우주궤도에 진입한 순간부터 가혹한 우주환경에 노출되어 위성체의 주요부품에 기능장애가 발생하여 결국 임무의 실패로 이어지기도 한다. 따라서 위성체는 지상에서 우주환경시험을 거쳐 기능 및 작동상태를 점검해야 한다. 한국항공우주연구원에서는 ∮3.6m×L3m 규모의 열진공챔버라 불리는 우주환경 모사장비를 보유ㆍ운용 중이나, 정지궤도 위성과 같은 대형 위성체의 시험을 위해 2005년 완공을 목표로 ∮8m×L10m급의 대형열진공챔버를 국산화 제작하고 있다. 통상 열진공챔버는 크게 진공계와 열제어계로 구분되어 질 수 있는데, 특히 열제어계에서 극저온 모사장치는 LN2를 쉬라우드 내부에 순환시킴으로서 -196℃의 극저온을 모사하는 시스템을 말한다. 본 논문에서는 국산화 대형열진공챔버의 열제어계에 적용할 극저온 모사장치의 개발 방안에 대하여 연구하였다.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2004년도 추계학술대회
• /
• pp.1236-1240
• /
• 2004

Thermal vacuum test for satellites should be performed before launch to verify the feasibility of satellites' operation in a harsh space environment which is represented as an extremely cold temperature and vacuum condition. A large space simulator(${\Phi}8m{\times}L10m$) has been demanded to accomplish the thermal vacuum test for the huge satellites designed in compliance with the national space program of Korea. In this paper, the design and calculation of thermal shroud which is the core part of large space simulator were discussed. The characteristics of the large space simulator being constructed at Korea Aerospace Research Institute(KARI) were depicted.