• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.35 no.9
• /
• pp.826-835
• /
• 2007

Solar heat flux data is needed for thermal load prediction of launch vehicle. In order to predict the solar flux, several solar flux models have been compared and a new model is developed. Most of the models can predict well the direct solar flux, but show some errors in the scattered solar flux. The newly developed model considered isotropic and anisotropic scattered solar fluxes, and the predicted solar flux agreed well with the measured. Because the present model can be used at any longitude, latitude, day and altitude, the model would be an useful tool to predict the thermal load of the launch vehicle and the vehicles which have to consider the solar heat.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.21 no.3
• /
• pp.306-314
• /
• 2018

In maritime environment, it is necessary to understand the characteristics of sunglint since it may degrade the target detection performance of the infrared sensor mounted weapons. In this paper, sunglint in LWIR band is modeled using the slope distribution of the sea surface, and is verified by comparing the radiance of a simulated result with that of the real world. According to the simulation, sunglint is critical when the solar zenith angle is over $60^{\circ}$. The peak radiance of sunglint grows as the solar zenith angle increases until it reaches $83^{\circ}$ and has a large difference depending on the solar zenith angle when the wind speed is small. Finally, seasonal and temporal characteristics of sunglint effects are analyzed. In summer, sunglint is dominant in the horizon near the solar azimuth right after sunrise and before sunset. However, in winter, the influence of sunglint lasts even during the daytime since the elevation of the sun is much lower than in summer.

• 한국신재생에너지학회:학술대회논문집
• /
• 2011.05a
• /
• pp.75.1-75.1
• /
• 2011

화석연료의 고갈과 온실가스 배출의 증가로 지속 가능한 친환경 에너지 생산이 요구되는 가운데, 태양광 발전은 이러한 조건을 만족시키는 에너지 생산 방안으로 주목받고 있다. 태양광 발전은 태양 직사광을 이용한 발전 방법 때문에 실외에 설치되어야 하며 이에 따라 외부의 충격이나 오염물질로부터 태양전지 패널을 보호하기 위한 보호층이 필수적이다. 그러나 보호층에 의한 입사광의 반사 및 먼지나 황사에 의한 보호층의 오염 등은 태양전지의 발전 효율을 감소시키는 요인으로 작용하여 이에 대한 대응이 필요하다. 본 연구에서는 PET 필름에 나노 임프린트 리소그래피 및 핫 엠보싱 공정을 이용하여 moth-eye 반사방지 패턴을 형성함으로써 보호층에서의 입사광 반사를 억제하였다. 또한, 이러한 반사방지 패턴에 초소수성 자기조립단분자막을 코팅하여 표면 에너지를 낮춤으로써 먼지 및 황사에 의해 오염되었을 경우에도 빗물에 의해 오염 물질이 쉽게 씻겨 내릴 수 있는 자정기능을 부여하였다. 이러한 반사방지를 통한 입사광 투과량의 향상 및 초소수성 표면에 의한 자정작용에 의하여 태양전지의 발전 효율이 증가되었다.

• Journal of the Korean Solar Energy Society
• /
• v.24 no.2
• /
• pp.51-62
• /
• 2004

Architects may evaluate building models to see how a building will shadow itself and its neighbors at various times. A heliodon, a tilt-table which is a machine that imitates the rotation and orbit of the Earth, helps architects wanting to analyze patterns of shadow patch, passive solar heating options, site solar panels, or control solar heat gain. The heliodon swivels in three directions for setting latitude, season, and time of day. Using the device, an architect first clamps a model to the tabletop, then turns the table to the coordinates of interest. Usually, the winter and summer solstices receive strong attention, for they represent extreme cases, A more recent installation at a university adds to its heliodon a set of lamps to recreate the illumination level and more accurate patterns of shadow patch. The table holds the building model at various angles to a spotlight, which mounts in the pole. The set of scale model measurement describes the validity of various electric lamps as an artificial sun to approximate the sun's parallel rays, helping designers to distinguish between illuminated areas in and around a building and those regions falling in the shadows.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.45 no.10
• /
• pp.898-906
• /
• 2017

This paper discusses the efficient high fidelity calculation of external thermal loads of a spacecraft on its orbit. Thermal loads to a spacecraft consist of three major components, direct solar radiation, earth reflection of solar rays, and earth irradiation. With the assumption that both earth reflection and earth emission are diffuse, thermal loads from earth surface divided into pieces of segments to satellite surfaces are individually calculated and summed over. By using analytical integration of both reflected and emitted heat load by earth, high rate of numerical convergence is achieved and the results are even exactly calculated in special cases. Moreover, KD tree ray tracing is employed in the calculation of thermal load to determine whether the radiated ray is obstructed or not by satellite structure.

• KIEAE Journal
• /
• v.3 no.1
• /
• pp.21-29
• /
• 2003

Scale model measurements should be conducted under an actual sky or in a simulated sky where conditions can be held constant. A number of successful attempts have been made to develop artificial sky domes with man-made sun emulators. With reference to formerly-developed examples, sky simulator facility has recently been activated in oder to provide desirable sky conditions for teaching and studies. The structure is a 6m-diameter dome and promises to set various condition for energy related and lighting research activities. The sky dome is also equipped a heliodon, the tilt table, to facilitate additive direct sun impact under clear skies. Shading studies, using scale models with the heliodon, reveal how a building's design blocks or permits light's passage to the interior; solar access studies, and tests of the reflection and transmittance characteristics of new daylighting technologies. The design and construction specification and the initial operating experience with a building configuration are reported.

• The Bulletin of The Korean Astronomical Society
• /
• v.37 no.2
• /
• pp.163.1-163.1
• /
• 2012

이 연구는 우주물체에 대한 광학감시 및 추적을 수행하기 위한 선행연구로, 궤도전파 시뮬레이터를 개발하여 궤도상 위성의 광학관측가능성을 분석하고 광학관측 여부를 판단하는 것을 목표로 한다. 연구의 주 내용은 주어진 궤도정보를 바탕으로 하는 태양동기궤도(Sun-Synchronous Orbit; SSO) 위성, Dawn-dusk 위성, 저궤도(Low Earth Orbit; LEO) 위성, 정지궤도(Geostationary Orbit; GEO) 위성 등 궤도상 위성의 추정궤도 전파와 자국위성의 광학관측가능성 분석으로 구성된다. 각각의 궤도전파 정밀도 및 광학관측가능성 분석성능을 확인하기 위해 AGI(Analytical Graphics Incorporated)사의 STK(Satellite Tool Kit) 시뮬레이션 프로그램을 사용하여 개발된 궤도전파 시뮬레이터와 비교하였다. 시뮬레이션 과정에서 광학관측의 제한조건을, 지구반영(penumbra)과 태양직사광(direct sun)에서만 관측하며, 고도(elevation angle)의 최소값은 20도, 태양고도(Sun elevation angle)의 최대값은 -10도로 설정하였다. 광학관측이 이루어지는 가상의 관측소는 임의로 선정하였으며, 기본적인 관측시간은 1년으로 잡고, 계절의 변화에 따른 광학관측가능성 궤적의 변화를 보기위해 춘하추동에 대해서 각각 3일이내의 기간 동안 시뮬레이션을 수행하였다. 결과적으로, 우주물체 광학감시 및 추적을 수행하기 위한 광학관측가능성 분석성능은 궤도전파 시뮬레이터 및 초기궤도요소 정밀도, 좌표변환과정 오차 등의 영향을 받으며, 설정된 제한조건에 따라 광학관측 지속시간의 차이가 발생한다. 연구결과를 통해 궤도상 위성의 궤도를 추정하기 위한 위성의 궤도전파 시뮬레이터를 개발하고, 자국위성의 관측가능성 분석을 통해 광학감시 및 추적시스템의 운영이 원활히 이루어질 수 있도록 한다.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.19 no.2
• /
• pp.13-22
• /
• 2005

This research aimed to generate two points of daylighting application as follows: 1) providing daylight performance data with a variety of glazing materials for a large window and 2) designing and evaluating an experimental type of differentiated window. For this purpose, we compared the daylight and distribution performance of new defined type of window configuration to the conventional window counterpart with a variety of glazing materials. The comparison was made for a deep, south-facing perimeter zone with large window, without any interior obstruction. The conventional window is the base single homogeneous glass pane, where as the differentiated window uses of two different glazings; an upper daylight glazing with high visible transmission and lower view window with lower transmittal glass. The daylight performance data was translated into a ratio between outdoor illuminance and the interiors. The simulated analysis of the conventional window indicates that the interior light levels have been changed proportionally dependent on the transmittance of the applied glass. The comparison of daylight distribution analysis showed that the differentiated window has lots of photometric advantage by the optical function of upper daylight window. In particular, the contribution of higher daylight window into deep rear space must be stressed for daylighting application.

• Journal of the Korean Institute of Landscape Architecture
• /
• v.40 no.5
• /
• pp.100-108
• /
• 2012

The purpose of the study was to evaluate the influence of shading and ventilation on Mean Radiant Temperature(MRT) of the outdoor space at a summer outdoor. The Wind Speed(WS), Air Temperature(AT) and Globe Temperature(GT) were recorded every minute from $1^{st}$ of May to the $30^{th}$ of September 2011 at a height of 1.2m above in four experimental plots with different shading and ventilating conditions, with a measuring system consisting of a vane type anemometer(Barini Design's BDTH), Resistance Temperature Detector(RTD, Pt-100), standard black globe(${\O}$ 150mm) and data acquisition systems(National Instrument's Labview and Compfile Techs' Moacon). To implement four different ventilating and shading conditions, three hexahedral steel frames, and one natural plot were established in the open grass field. Two of the steel frames had a dimension of $3m(W){\times}3m(L){\times}1.5m(H)$ and every vertical side covered with transparent polyethylene film to prevent lateral ventilation(Ventilation Blocking Plot: VP), and an additional shading curtain was applied on the top side of a frame(Shading and Ventilation Blocking Plot: SVP). The third was $1.5m(W){\times}1.5m(L){\times}1.5m(H)$, only the top side of which was covered by the shading curtain without the lateral film(Shading Plot: SP). The last plot was natural condition without any kind of shading and wind blocking material(Natural Open Plot: NP). Based on the 13,262 records of 44 sunny days, the time serial difference of AT and GT for 24 hour were analyzed and compared, and statistical analysis was done based on the 7,172 records of daytime period from 7 A.M. to 8 P.M., while the relation between the MRT and solar radiation and wind speed was analyzed based on the records of the hottest period from 11 A.M. to 4 P.M.. The major findings were as follows: 1. The peak AT was $40.8^{\circ}C$ at VP and $35.6^{\circ}C$ at SP showing the difference about $5^{\circ}C$, but the difference of average AT was very small within${\pm}1^{\circ}C$. 2. The difference of the peak GT was $12^{\circ}C$ showing $52.5^{\circ}C$ at VP and $40.6^{\circ}C$ at SP, while the gap of average GT between the two plots was $6^{\circ}C$. Comparing all four plots including NP and SVP, it can be said that the shading decrease $6^{\circ}C$ GT while the wind blocking increase $3^{\circ}C$ GT. 3. According to the calculated MRT, the shading has a cooling effect in reducing a maximum of $13^{\circ}C$ and average $9^{\circ}C$ MRT, while the wind blocking has heating effect of increasing average $3^{\circ}C$ MRT. In other words, the MRT of the shaded area with natural ventilation could be cooler than the wind blocking the sunny site to about $16^{\circ}C$ MRT maximum. 4. The regression and correlation tests showed that the shading is more important than the ventilation in reducing the MRT, while both of them do an important role in improving the outdoor thermal comfort. In summary, the results of this study showed that the shade is the first and the ventilation is the second important factor in terms of improving outdoor thermal comfort in summer daylight hours. Therefore, it can be apparently said that the more shade by the forest, shading trees etc., the more effective in conditioning the microclimate of an outdoor space reducing the useless or even harmful heat energy for human activities. Furthermore, the delicately designed wind corridor or outdoor ventilation system can improve even the thermal environment of urban area.