• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2011년도 춘계학술발표대회 논문집
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• pp.223-228
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• 2011

The volumetric solar receiver is a key element of solar power plants using air. The solar flux distribution inside the receiver should be a priori known for its heat transfer modeling. Previous works have not considered characteristics of the solar flux although they change with radiative properties of receiver materials and receiver geometries. A numerical method, which is based on the Monte Carlo ray-tracing method, was developed in the current work. The solar flux distributions inside multi-channeled volumetric solar receivers were calculated when light is concentrated at the KIER solar furnace. It turned out that 99 percentage of the concentrated solar energy is absorbed within 15 mm charmel length for the charmel radius smaller than 1.5 mm. If the concentrated light is assumed to be diffuse, the absorbed solar energy at the charmel entrance region is overpredicted while the light penetrates more deeply into the charmel. The developed method will help understand the solar flux when only a part of concentrated light is of interest. Furthermore, if the presented results are applied for heat transfer modeling of multi-channeled volumetric solar receivers, one could examine effects of receiver charmel properties and shape on air temperature profiles.

• 한국태양에너지학회 논문집
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• 제31권4호
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• pp.41-47
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• 2011

The volumetric solar receiver is a key element of solar power plants using air. The solar flux distribution inside the receiver should be a priori known for its heat transfer analysis. Previous works have not considered characteristics of the solar flux although they change with radiative properties of receiver materials and receiver geometries. A numerical method, which is based on the Monte Carlo ray-tracing method, was developed in the current work. The solar flux distributions inside multi-channeled volumetric solar receivers were calculated when light is concentrated at the KIER solar furnace. It turned out that 99 percentage of the concentrated solar energy is absorbed within 15mm channel length for the channel radius smaller than 1.5mm. If the concentrated light is assumed to be diffuse, the absorbed solar energy at the channel entrance region is over predicted while the light penetrates more deeply into the channel. Once the presented results are imported into the heat transfer analysis, one could examine effects of material property and geometry of the receiver on air temperature profiles.

• 대한기계학회논문집B
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• 제35권12호
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• pp.1383-1389
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• 2011

본 연구는 태양열 발전에 사용하는 공기식 다채널 체적식 흡수기의 일관성 있는 열전달 해석에 초점을 두고 있다. 이를 위해 흡수 소재 물성과 채널 형상 변화의 영향을 몬테카를로 광선추적법에 기반한 광학 모델과 전도, 대류, 복사를 고려한 1 차원 열전달 모델에 동시에 반영하였다. 광학 모델 결과는 채널 반경 대비 길이의 형상비가 매우 커서 대부분의 태양 에너지는 15 mm 이내의 짧은 길이에서 흡수됨을 증명하고 있다. 복사 열손실 분류를 통해 채널의 낮은 흡수율에서는 방사 손실은 줄지만 반사손실이 증가하여 흡수기 효율이 감소하는 것을 보였다. 큰 채널 반경이나 작은 질량 유량으로 인해 흡수기 평균 온도가 상승할 때, 방사 손실과 반사 손실 모두 증가하지만 방사 손실의 영향이 더 큰 것으로 나타났다.

• Journal of electromagnetic engineering and science
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• 제10권4호
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• pp.290-295
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• 2010

In this paper, an interference analysis method with a site-specific path loss model for a wireless personal area network (WPAN) is proposed. The site-specific path loss model is based on geometrical optics and geometric probability to consider both site-specific radio propagation characteristics and a closed-form expression to obtain the mean interference from which the uniformly distributed multiple interferers are derived. Therefore, the proposed interference analysis method can achieve more computational simplicity than the Monte-Carlo (MC) simulation, which uses the ray-tracing (RT) technique. In addition, better accuracy than the conventional interference analysis model that uses stochastic method can also be achieved. To evaluate the proposed method, a signal to the interference-noise ratio with a mean interference concept for uniformly distributed interferers is calculated and compared in two simulation scenarios. As a result, the proposed method produces not only better matched results with the MC simulation using the RT technique than the conventional interference analysis model, but also simpler and faster calculation, which is due to the site-specific path loss model and closed-form expression for interference calculation.

• Journal of Mechanical Science and Technology
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• 제17권8호
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• pp.1185-1195
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• 2003

Heat losses from the receivers of a dish-type solar energy collecting system at the Korea Institute of Energy Research (KIER) are numerically investigated. It is assumed that a number of flat square mirrors are arranged on the parabolic dish structure to serve as a reflector. Two different types of receivers, which have conical and dome shapes, are considered for the system, and several modes of heat losses from the receivers are thoroughly studied. Using the Stine and McDonald model convective heat loss from a receiver is estimated. The Net Radiation Method is used to calculate the radiation heat transfer rate by emission from the inside surface of the cavity receiver to the environment. The Monte-Carlo Method is used to predict the radiation heat transfer rate from the reflector to the receiver. Tracing the photons generated, the reflection loss from the receivers can be estimated. The radiative heat flux distribution produced by a multifaceted parabolic concentrator on the focal plane is estimated using the cone optics method. Also, the solar radiation spillage around the aperture is calculated. Based on the results of the analysis, the performances of two different receivers with multifaceted parabolic solar energy collectors are evaluated.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2006년도 춘계학술대회 논문집
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• pp.3-7
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• 2006

Development of light sources has been constantly grown for a high efficacy and long life. And, the design of luminaires has ben developed for the reflection and refraction of light mechanism. But it has been not enough to study for the refraction of light mechanism. Therefore, this study aims to study for the refraction of light mechanism to using Monte-Carlo method and Ray-tracing method. In addition, the purpose of this study is to shu calculation process for development of 3 dimensional planar prism design algorithm in orer to use the results of photometric data that is able to obtain various luminous intensity distribution.

• 대한기계학회논문집B
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• 제39권12호
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• pp.927-934
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• 2015

고일사 지역인 사우디아라비아에서 태양열로 구동하는 흡수식 냉동 시스템 개발을 염두에 두고, 본 논문에서는 태양을 추적하는 선형 프레넬 반사판 시스템의 집광 특성을 수치해석 하였다. 몬테카를로 광선추적법을 기반으로 하는 광학 프로그램을 통해 집광 열유속, 집광 효율, 집광 에너지를 일년을 대표하는 춘분, 하지, 추분, 동지 날짜에 계산하였다. 동지를 제외하면, 9 시에서 15 시까지는 집광 성능이 일정한 가운데, 집광 효율도 70% 이상으로 높게 나타났다. 이 시간대에서 흡수기 중심 20% 영역에 모이는 최대 열유속은 하지 때 약 $13.0{\sim}14.6kW/m^2$ 범위에서 변했다. 집광 시스템의 설계 인자 중에서 흡수기 설치 높이, 반사판의 폭, 반사판 사이의 거리가 집광 효율을 조사해 보면, 흡수기 설치 높이는 반사판의 폭에 관계없이 5 m 에서 최적의 성능을 나타냈다. 반사판의 폭이 작을수록 집광 효율이 좋지만, 반사판의 폭은 집광 되는 에너지에 직접적으로 비례하기 때문에 냉동 시스템의 용량에 맞추어 설계가 필요하다. 본 연구는 흡수기의 열전달 해석의 중요한 선행조건이므로 향후에 광학-열전달 연계된 해석을 통해 전체 시스템의 성능을 예측하고 설계하는데 활용할 수 있을 것이다.

• 설비공학논문집
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• 제15권6호
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• pp.533-542
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• 2003

This study aims to propose a simplified mathematical model for calculating vertical air temperature distribution in a four-sided atrium. In the first stage of the mathematical modeling, the computer model combined zonal model and solar radiation model using Monte Carlo method and Ray tracing technique went through a computer simulation with architectural variables applied to a four-sided atrium in summer. In the next stage, Curve Expert, a computer program that gets the most suitable solution ac-cording to the least squares method, is used to analyze the results of the computer simulation and to derive the mathematical model. The accuracy of the mathematical model was evaluated through a comparison of calculation results from a mathematical model and computer simulation. In this validation step using the least square method, the R2 value of the Zones 1, 2 and 3 showed higher than 0.945. Zone 4 has an R2 value of 0.911, lower than the previous three zones. However the relative error was below 0.5%, which is considered very small.

• 천문학회지
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• 제33권3호
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• pp.165-172
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• 2000

A baffle system for an airglow photometer, which will be on board the Korea Sounding Rocket-III(KSR-III), has been designed to suppress strong solar scattered lights from the atmosphere below the earth limb. Basic principles for designing a baffle system, such as determination of baffle dimensions, arrangement of vanes inside a baffle tube, and coating of surfaces, have been reviewed from the literature. By considering the constraints of the payload size of the KSR-III and the incident angle of solar light scattered from the earth limb, we first determined dimensions of a two-stage baffle tube for the airglow photometer. We then calculated positions and heights of vanes to prohibit diffusely reflected lights inside the baffle tube from entering into the photometer. In order to evaluate performance of the designed baffle system, we have developed a ray tracing program using a Monte Carlo method. The program computed attenuation factors of the baffle system on the order of $10^{-6}$ for angles larger than $10^{\circ}$, which satisfies the requirements of the KSR-III airglow experiment. We have also measured the attenuation factors for an engineering model of the baffle system with a simple collimating beam apparatus, and confirmed the attenuation factors up to about $10^{-4}$. Limitation of the apparatus does not allow to make more accurate measurements of the attenuation factors.

• 한국정보과학회논문지:시스템및이론
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• 제32권3호
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• pp.133-147
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• 2005

LCD BLU(Back-Light Unit)의 설계에는 광선추적 기법이 많이 사용되고 있으며, 이러한 기법을 통하여 도광판 전면으로 출사되는 빛의 휘도, 휘도의 균일도, 광효율 등을 수치적으로 예측할 수 있다. 휘도와 휘도의 균일도 등과 같은 항목은 BLU 설계에 있어서 매우 중요한 요소 중의 하나이며, 이러한 BLU의 광학적 특성은 도광판의 후면에 인쇄된 잉크패턴에 가장 많을 영향을 받고 있다 따라서 높은 휘도와 균일도를 발생시킬 수 있는 최적화된 잉크패턴을 설계하는 것은 BLU의 설계에 있어서 가장 중요한 부분 중의 하나이다. 본 논문에서는 최적의 잉크패턴을 설계하기 위하여 직접탐색(Direct Search) 기법 중에서 Holder Mead의 심플렉스탐색(Simplex Search) 알고리즘을 적용하였다. 직접탐색 기법은 최적의 잉크패턴을 계산하는 것과 같은 비선형적이고, 비연속적이며, 미분불가능한 함수의 최적점을 계산하는 분야에 많이 적용되고 있다. 본 논문에서는 여러 가지 실험을 통하여 심플렉스탐색 기법이 최적의 잉크패턴을 설계하는데 있어서 매우 효율적이며 안정적으로 사용될 수 있음을 보여주며, 이러한 최적화 기법으로 인하여 BLU 설계기능을 개선할 수 있음을 보여준다