• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.213.1-213.1
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• 2012

우주방사선폭풍탐사선 (Space Radiation Storm probe: SRSP)에 탑재할 과학측정 장비들 중의 하나로 추진 중인 PD는 우주방사선 환경에서의 태양활동에 따른 고에너지 하전입자들 특히 proton의 에너지와 flux에 대한 정보를 획득하고 더불어 다른 고에너지 입자의 효과까지 포함하는 Linear Energy Transfer (LET)을 측정하기 위한 탑재체이다. 본 연구팀은 PD의 사양을 결정하기 위해서 GEANT4를 사용하여 전산모사를 수행하였으며, proton의 경우 우주 방사선 환경에서의 태양활동에 따른 고에너지 영역을 고려하여 0.1 ~ 1000 MeV 범위에서 전산 모사를 수행하였다. 본 연구팀은 특히 PD의 에너지 범위를 0 MeV ~ 5 MeV, 5 MeV ~ 10 MeV, 10 MeV ~ 20 MeV, 20 MeV ~ 35 MeV, 35 MeV ~ 52 MeV, 52 MeV ~ 72 MeV, 72 MeV 이상으로 총 7개의 channel를 결정하고 Al의 blocking material을 사용하여 검출하려는 에너지 범위를 조절한다. 또한 최적의 채널을 결정하여 silicon detector를 사용한 탑재체의 개념 설계를 실시하였다. 설계된 PD로부터 방사선대에서의 proton를 측정함으로써 태양기원 고에너지 입자에 대한 포획 및 쇠퇴에 대한 이해를 도울 것이다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.5
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• pp.460-465
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• 2007

This paper deals with the Fine Digital Sun Sensor (FDSS) for Science & Technology Satellite 2(STSAT-2). The FDSS was firstly developed by using CMOS-Image sensor(CIS) in South Korea. This paper will describe the configuration of the FDSS, the design of the optical part, the analysis result of the optical characteristics of the sunlight, and the calibration result measured by solar simulator.

• Journal of the Korean Solar Energy Society
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• v.27 no.3
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• pp.45-54
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• 2007

For a conventional natural-circulation type solar water heater, the pressure head is limited by the height between the storage tank and hot water tap. Therefore, it is difficult to provide sufficient hot water flow rate for general usage. This study deals with a design modification of the storage tank to utilize the tap-water pressure to increase hot-water supply Based on fluid dynamic and heat transfer theories, a series of modeling and simulation is conducted to achieve practical design requirements. An experimental setup is built and tested and the results are compared with theoretical simulation model. The storage tank capacity is 240 l and the outer diameter of piping was 15 mm. Number of tube turns tested are 5, 10, and 15. Starting with initial storage tank temperature of $80^{\circ}C$, the temperature variation of the supply hot water is investigated against time, while maintaining minimum flow rate of 10 1/min. Typical results show that the hot water supply of minimum $30^{\circ}C$ can be maintained for 34 min with tap-water supply pressure of 2.5 atm, The relative errors between modeling and experiments coincide well within 10% in most cases.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.1
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• pp.50.2-50.2
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• 2014

지상에서 관측한 태양계 천체의 분광자료에는 여러 가지 자료들이 포함되어 있다. 태양계 천체는 태양빛을 받아 반사되는 빛이 관측되기 때문에 태양 분광선도 포함되어 있고, 지구 대기를 통과하기 때문에 지구 대기 흡수선 및 방출선도 포함되어 있다. 특히 지구 대기에 의한 분광선은 관측지의 위치, 관측일의 날씨 등이 영향을 미칠 수 있다. 그 외에도 기기에서 발생하는 여러 잡음들이 합쳐진 관측 자료가 획득된다. 이렇게 얻어진 관측 결과로부터 태양 분광선, 지구 대기 흡수선, 기기로부터의 잡음 등을 제거해서 최종적으로 순수한 태양계 천체의 분광선을 획득하게 된다. 본 연구에서는 현재 개발중인 우주탐사선용 중적외선 분광기 지상모델의 현장 검증과정에서 생산될 수 있는 관측 자료에 대한 모사를 하고자 한다. 이 자료는 향후 관측 당시의 대기 상태 및 기기 상태에 따라 발생되는 관측 결과를 예상할 수 있기 때문에 관측 날짜 지정 및 기기 상태 점검에 유용하게 사용될 것이라고 기대한다.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.967-972
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• 2009

A dynamic model has been developed to investigate the operability of a single and double-effect solar energy assisted parallel type absorption chiller. In the study, main components and fluid transport mechanism were modeled. And solar radiation and the solar collector also were also modeled along with its control design. The model was run for the single mode with solar energy supply only and the solar/gas driving double effect mode. From the simulation results, it was found that the present configuration of the chiller is not capable of regulating solution flow rates according to variable solar energy input. And the issues of the excessive circulation flowrate and the mismatch between available solar power and cooling load discourages the use of the single mode, but the dual use of gas and solar power is recommendable in view of controllability and enhanced COP.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2000.11a
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• pp.197-199
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• 2000

오존은 배출원에서 직접 배출되는 1차 오염물질이 전구물질들이 강한 태양광선에 의해 광화학 반응을 일으켜 생성되는 2차 광화학 오염물질이다. 대표적인 전구물질로는 질소산화물(NOx)과 휘발성유기화합물(VOC)이다. 이러한 전구물질들은 화석연료의 연소와 자동차에서 직접 배출되어 대기 중에서 복잡한 물리ㆍ화학과정을 통하여 오존을 생성한다. 최근에 도심 지역 및 주변지역 그리고 몇몇 시골지역에서 발생하고 있는 오존의 고농도 현상은 중요한 대기오염 문제중의 하나로 부각되고 있다. (중략)

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.4
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• pp.318-325
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• 2015

Pico satellite has limited surface to install the solar cells due to its extremely limited size. Also, the sun incidence angle with respect to the solar panel continuously varies according to the attitude control strategy and its important parameter for the power generation. In this study, a concentrating photovoltaic system for pico satellite application has been proposed that can enhance the power generation efficiency in case of the unfavorable condition of the sun incidence angle with respect to the solar panel of the satellite using the fresnel lens. To prove the possibility of maximizing the power generation efficiency of the proposed concentrating power system, we have performed the power measurement test using a solar simulator and commercial fresnel lens. And on-orbit analysis of the power generation efficiency using the STK which is a commercial S/W has also been performed based on the test results.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.18 no.1
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• pp.45-49
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• 2008

The development of manufacturing process of silicon (Si) ingots is one of the important issues to the growth of the photovoltaic industry. Polycrystalline Si wafers shares more than 60% of the photovoltaic market due to its cost advantage compared to mono crystalline silicon wafers. Several solidification processes have been developed by industry including casting, heat exchange method (HEM) and electromagnetic casting. In this paper, the advanced directional solidification (ADS) method is used to growth of large sized polycrystalline Si ingot. This method has the advantages of the small heat loss, short cycle time and efficient directional solidification. The numerical simulation of the process is applied using a fluid dynamics model to simulate the temperature distribution. The results of simulations are confirmed efficient directional solidification to the growth of large sized polycrystalline Si ingot above 240 kg.

• Korean Chemical Engineering Research
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• v.60 no.4
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• pp.535-543
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• 2022

A CPFD (Computational particle fluid dynamics) model of solar fluidized bed receiver of silicon carbide (SiC: average d_p=123 ㎛) particles was established, and the model was verified by comparing the simulation and experimental results to analyze the effect of particle behavior on the performance of the receiver. The relationship between the heat-absorbing performance and the particles behavior in the receiver was analyzed by simulating their behavior near bed surface, which is difficult to access experimentally. The CPFD simulation results showed good agreement with the experimental values on the solids holdup and its standard deviation under experimental condition in bed and freeboard regions. The local solid holdups near the bed surface, where particles primarily absorb solar heat energy and transfer it to the inside of the bed, showed a non-uniform distribution with a relatively low value at the center related with the bubble behavior in the bed. The local solid holdup increased the axial and radial non-uniformity in the freeboard region with the gas velocity, which explains well that the increase in the RSD (Relative standard deviation) of pressure drop across the freeboard region is responsible for the loss of solar energy reflected by the entrained particles in the particle receiver. The simulation results of local gas and particle velocities with gas velocity confirmed that the local particle behavior in the fluidized bed are closely related to the bubble behavior characterized by the properties of the Geldart B particles. The temperature difference of the fluidizing gas passing through the receiver per irradiance (∆T/I_DNI) was highly correlated with the RSD of the pressure drop across the bed surface and the freeboard regions. The CPFD simulation results can be used to improve the performance of the particle receiver through local particle behavior analysis.

• Transactions of the Korean Society of Mechanical Engineers
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• v.9 no.5
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• pp.579-589
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• 1985

The storage tank of the natural-circulation-solar-hot-water system equipped with flat-plate solar collectors is located at higher elevation than the solar collectors. Therefore, the heat loss from the system due to a reversed flow during the night-time is an important factor as well as the day-time thermal performance of the system. The thermal performance of the natural-circulation-solar-hot-water system with flat-plate solar collectors during the day-time depends mainly on the heat collecting efficiency of the solar collectors, whereas its thermal performance during the night-time depends on the system configuration , such as the elevation of the water storage tank with respect to the solar collectors and the piping connections between the storage tank and the solar collectors, as well as thermo-physical properties of the circulating fluid. In the present work, a computer program has been developed to simulate a typical natural-circulation-solar-hot-water-system, and a series of simulation tests have been carried out with the computer program to examine the thermal performance of the system during the day-time as well as the hight-time. In addition , a series of experiment have been conducted under a real sun condition using a natural-circulation-solar-hot-water-system constructed and installed at the KAIST building to compare with the results obtained from computer simulations.