• 대한기계학회논문집B
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• 제25권10호
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• pp.1451-1458
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• 2001

The effects of a specularly reflecting surface on the wall heat flux and medium temperature distribution are studied. The system is an infinite square duct enclosing an absorbing and emitting medium. The walls are opaque, and black or gray. The walls emit diffusely but reflect diffusely or speculary. Heat is transferred by the combined effect of conduction and radiation. The radiative heat transfer is analyzed using direct discrete-ordinates method. The parameters under study are conduction, to radiation parameter, optical depth, wall emissivity, and reflection characteristics. The specular reflection and diffuse reflection show sizeable differences when the conduction to radiation parameter is less than around 0.01. The differences appear only either on the side wall heat flux or on the medium temperature profiles for the range of this study. The differences on the side wall heat flux are observed for optical thickness less than around 0.1 However the differences on the medium temperate profiles are found for optical thickness greater than around 1. The difference increase with increasing reflectance. The specular reflection increases the well heat flux gradient along the side wall.

• 대한기계학회논문집B
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• 제30권10호
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• pp.950-956
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• 2006

A mathematical heat transfer model for the prediction of heat flux on the slab surface and temperature distribution in the slab has been developed by considering the thermal radiation in the furnace and transient conduction governing equations in the slab, respectively. The furnace is modeled as radiating medium with spatially varying temperature and constant absorption coefficient. The slab is moved with constant speed through non-firing, charging, preheating, heating, and soaking zones in the furnace. Radiative heat flux which is calculated from the radiative heat exchange within the furnace modeled using the FVM by considering the effect of furnace wall, slab, and combustion gases is applied as the boundary condition of the transient conduction equation of the slab. Heat transfer characteristics and temperature behavior of the slab is investigated by changing such parameters as absorption coefficient and emissivity of the slab. Comparison with the experimental work shows that the present heat transfer model works well for the prediction of thermal behavior of the slab in the reheating furnace.

• 한국군사과학기술학회지
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• 제22권5호
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• pp.644-653
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• 2019

With the development of themal observatory device(TOD), thermal camouflage system has been applied not only to the weapon system but also to the combat suit for soldiers. In this paper, the characteristic of thermal radiation of human body depending on the clothing material properties was analyzed through numerical simulations. The bioheat equation with thermoregulatory model was solved to obtain the realistic surface temperature of human body and these results are combined with the emissivity of human skin and clothing in order to calculate the thermal signature from the human body. According to each thermal resistance of clothing, the optimal background radiance which makes contrast radiance intensity(CRI) be lowest is different. Also, the average CRI variation per thermal resistance change is about twice as much as the case of evaporative resistance change.

• 설비공학논문집
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• 제16권10호
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• pp.942-951
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• 2004

This paper presents the results of a theoretical study of the effect of radiation during free convective laminar film boiling for methanol/water binary mixtures on an isothermal vertical wall at atmospheric pressure. With the well-known boundary layer theory as a basis, a theoretical model has been formulated into consideration for mass diffusion at liquid phase. The equations are numerically solved by a similarity method to investigate the effects of radiation emissivity on the surface with various parameters such as wall superheat and composition of more volatile component at liquid phase far from the wall. From the results, the distributions of the physical quantifies are investigated in both phases. New correlations are proposed to predict the heat transfer coefficient of binary mixtures. It is shown that the proposed correlations are in good agreement with numerical results and with Bromley's correlation within maximum $11\%$ errors. It is also found that as the wall superheat is increased, radiation effect becomes more important.

• 감성과학
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• 제18권1호
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• pp.49-58
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• 2015

본 연구는 감성의류용 탄화지르코늄 함유 축열 니트의 원적외선 특성을 연구하였다. 탄화지르코늄 함유 축열 PET 원사가 이성분 방사법에 의해 방사되었다. 이 원사의 core부에는 고점도 PET와 탄화지르코늄을 혼합한 용액을, sheath부에는 저점도 PET 용액을 사용하여 콘쥬게이트 방사를 실시하였다. 이들 방사된 원사의 원소분석과 원적외선 특성 분석이 EDS와 FT-IR 계측기기에 의해 분석되었으며 두 가지 조직의 니트 소재를 편직하여 이들의 열적특성을 분석하였다. EDS 분석에서 Zr 피크를 확인하였으며 원사내에 Zr 원소가 19.29% 함유되어 있음을 확인하였다. 또한 원적외선 분석에서 $5{\sim}20{\mu}m$ 파장 영역에서 원적외선 방사에너지가 $3.65{\times}10^2W/m^2$, 방사율이 0.906 임을 확인하였다. KES-F7 측정기 분석에서 ZrC 함유 편성물의 Qmax 값이 일반 PET 편성물의 값보다 낮은 값을 보였고 보온율 값은 ZrC 함유 편성물이 일반 PET보다 더 높은 값을 보이므로서 ZrC의 축열성을 확인하였다. 열전도도는 Zr의 높은 열전도도 때문에 일반 PET 편물보다 더 높은 값을 보였다. ZrC의 함유가 편물의 촉감에 미치는 영향을 없었으며 편성 조직이 더 큰 영향을 주는 것을 확인하였다.

• 대한공간정보학회지
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• 제24권4호
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• pp.105-113
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• 2016

산불방사열에너지(fire radiative power)는 산불로부터 방출되는 에너지로서 산불의 연소과정에서 발생하는 온실가스를 추정하기 위한 기초자료로 이용된다. 유럽, 아프리카, 아메리카 지역의 정지궤도 위성센서들은 준실시간의 산불방사열에너지를 산출 및 제공하고 있지만 아시아권에는 아직까지 정지궤도 위성기반의 공식적인 산불방사열에너지 산출물이 제공되지 않고 있다. 본 연구에서는 중적외 복사휘도법(mid-infrared radiance method)을 이용하여 히마와리(Himawari-8) 위성 기반의 산불방사열에너지를 최초로 산출하였으며, 산출정확도를 검증하기 위해 인도네시아 수마트라 지역에 대해 Aqua/Terra 위성의 MODIS(moderate resolution imaging spectroradiometer) 산불방사열에너지 산출물과의 비교검증을 실시하였다. 이 과정에서 NDVI(normalized difference vegetation index)와 FVC(fraction of vegetation coverage)를 이용하여 중적외 복사휘도법의 중요인자인 지표면 방출률을 지면피복 종류에 따라 계산하였으며, 최적화 실험을 통하여 히마와리 AHI(advanced Himawari imager)의 센서계수 a = 3.11을 도출하였다. 본 연구를 통해 산출된 히마와리 산불방사열에너지는 MODIS를 기준으로 약 20%의 평균절대백분비오차를 나타내었으며 이는 미국과 유럽연합의 정지궤도위성의 산불방사열에너지 검증결과와 유사한 수준의 정확도로 평가된다. 히마와리 산불방사열에너지의 산출정확도는 산불의 크기와 위성관측각에 따라 일부 차이를 보였으나 태양천정각과 토지피복에 따른 영향은 거의 없는 것을 알 수 있었다. 이 연구는 아시아권의 정지궤도위성 산불방사열에너지 산출을 위한 참고자료로서 활용가치가 있으며 산불방출 온실가스 추정에 기초자료로 활용될 수 있을 것으로 기대한다.

• 대기
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• 제23권4호
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• pp.453-470
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• 2013

As a part of the KIAPS Observation Processing System (KOPS), we have developed the modules of satellite radiance data pre-processing and quality control, which include observation operators to interpolate model state variables into radiances in observation space. AMSU-A (Advanced Microwave Sounding Unit-A) level-1d radiance data have been extracted using the BUFR (Binary Universal Form for the Representation of meteorological data) decoder and a first guess has been calculated with RTTOV (Radiative Transfer for TIROS Operational Vertical Sounder) version 10.2. For initial quality checks, the pixels contaminated by large amounts of cloud liquid water, heavy precipitation, and sea ice have been removed. Channels for assimilation, rejection, or monitoring have been respectively selected for different surface types since the errors from the skin temperature are caused by inaccurate surface emissivity. Correcting the bias caused by errors in the instruments and radiative transfer model is crucial in radiance data pre-processing. We have developed bias correction modules in two steps based on 30-day innovation statistics (observed radiance minus background; O-B). The scan bias correction has been calculated individually for each channel, satellite, and scan position. Then a multiple linear regression of the scan-bias-corrected innovations with several predictors has been employed to correct the airmass bias.

• 한국초전도ㆍ저온공학회논문지
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• 제15권4호
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• pp.53-58
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• 2013

KSTAR in-vessel cryo-pump has been installed in the vacuum vessel top and bottom side with up-down symmetry for the better plasma density control in the D-shape H-mode. The cryogenic helium lines of the in-vessel cryo-pump are located at the vertical positions from the vacuum vessel torus center 2,000 mm. The inductive electrical potential has been optimized to reduce risk of electrical breakdown during plasma disruption. In-vessel cryo-pump consists of three parts of coaxial circular shape components; cryo-panel, thermal shield and particle shield. The cryo-panel is cooled down to below 4.5 K. The cryo-panel and thermal shields were made by Inconel 625 tube for higher mechanical strength. The thermal shields and their cooling tubes were annealed in air environment to improve the thermal radiation emissivity on the surface. Surface of cryo-panel was electro-polished to minimize the thermal radiation heat load. The in-vessel cryo-pump was pre-assembled on a test bed in 180 degree segment base. The leak test was carried out after the thermal shock between room temperature to $LN_2$ one before installing them into vacuum vessel. Two segments were welded together in the vacuum vessel and final leak test was performed after the thermal shock. Commissioning of the in-vessel cryo-pump was carried out using a temporary liquid helium supply system.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2007년도 Proceedings of ISRS 2007
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• pp.556-559
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• 2007

The Urban Environmental Quality (UEQ) indicates a complex and various parameters resulting from both human and natural factors in an urban area. Vegetation, climate, air quality, and the urban infrastructure may interact to produce effects in an urban area. There are relationships among air pollution, vegetation, and degrading environmental the urban heat island (UHI) effect. This study investigates the application of multi-spectral remote sensing data from the Landsat ETM and TM sensors for the mapping of air quality and UHI intensity in Seoul from 2000 to 2006 in fine resolution (30m) using the emissivity-fusion method. The Haze Optimized Transform (HOT) correction approach has been adopted for atmospheric correction on all bands except thermal band. The general UHI values (${\Delta}(T_{urban}-T_{rural})$) are 8.45 (2000), 9.14 (2001), 8.61 (2002), and $8.41^{\circ}C$ (2006), respectively. Although the UHI values are similar during these years, the spatial coverage of "hot" surface temperature (>$24^{\circ}C$) significantly increased from 2000 to 2006 due to the rapid urban development. Furthermore, high correlations between vegetation index and land surface temperature were achieved with a correlation coefficients of 0.85 (2000), 0.81 (2001), 0.84(2002), and 0.89 (2006), respectively. Air quality is shown to be an important factor in the spatial variation of UEQ. Based on the quantifiable fine resolution satellite image parameters, UEQ can promote the understanding of the complex and dynamic factors controlling urban environment.

• 대한원격탐사학회지
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• 제27권3호
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• pp.339-351
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• 2011

This study investigates the potentials of satellite, ground measurement data, and geo-spatial information within an urban area for the mapping of the Urban Environmental Quality (UEQ) parameters. The UEQ indicates a complex and various parameters resulting from both human and natural factors, which are greenness, climate, air pollution, the urban infrastructure, and etc. Multi-spectral remote sensing data from the Landsat ETM and TM sensors for the mapping of air pollution by the Haze Optimized Transform (HOT) technique, Urban Heat Island (UHO using the emissivity-fusion method in Seoul from 2000 to 2006 in fine resolution (30m) were analyzed for the estimation of UEQ index. Although the UHI values are similar ($8.4^{\circ}C{\sim}9.1^{\circ}C$) during these years, the spatial coverage of "hot" surface temperature (> $24^{\circ}C$) significantly increased from 2000 to 2006 due to the rapid urban development. Furthermore, high correlations between vegetation index and land surface temperature were achieved with a correlation coefficients of 0.85 (2000), 0.81 (2001), 0.84 (2002), and 0.89 (2006), respectively. It was found that the proposed method was successfully analyzed spatial structure of the UEQ and the scenarios of the best and worst areas within the city were also identified. Based on the quantifiable fine resolution satellite image parameters, UEQ can promote the understanding of the complex and dynamic factors controlling urban environment.