• 한국태양에너지학회 논문집
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• 제35권1호
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• pp.21-28
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• 2015

A small washer powered directly and solely by thermal radiation was constructed and tested to explore the feasibility of using solar energy or other types of thermal radiation for washing and cleaning. In principle, TA (ThermoAcoustic) washers have the benefits of simpler design and operation and fewer energy conversion processes, thus should be more energy efficient and cost less than electric washing/cleaning systems. The prototype TA converter we constructed could sustain itself with consistent fluid oscillations for more than 20 minutes when powered by either concentrated solar radiation or an IR (infrared) heater. The frequencies of water oscillations in the wash chamber ranged from 2.6 to 3.6 Hz. The overall conversion efficiency was lower than the typical efficiencies of TA engines. Change in water temperature had little effect on the oscillatory flow in the TA washer due to its low efficiency. On the other hand higher water temperatures enhanced grease removal considerably in our tests. Methods for measuring the overall conversion efficiency, frictional loss, and grease removal of the TA washing system we designed were developed and discussed.

• 마이크로전자및패키징학회지
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• 제26권4호
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• pp.75-82
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• 2019

유연 태양 전지는 최근 휴대용 배터리, 웨어러블 소자, 로봇, 드론 및 비행기와 같은 광범위한 응용 분야로 인해 큰 주목을 받고 있다. 특히, 고효율 및 높은 신뢰성을 갖는 유연 실리콘 및 화합물 반도체 태양 전지의 요구가 계속 증가하고 있다. 본 연구에서는 유연 InGaP/GaAs 2중 접합 태양전지 모듈을 개발하였다. 특히 제작된 유연 태양전지 모듈의 신뢰성을 확보하기 위하여, 풍속 및 주위 온도가 태양 전지 작동 온도에 미치는 영향을 수치해석으로 분석하였다. 3종류의 풍속(0 m/s, 2.5 m/s 및 5 m/s) 및 2종류의 주변 온도 조건(25℃ 및 33℃)에 대하여 태양 전지 모듈의 온도 분포를 해석하였다. 유연 태양전지 모듈의 유연성은 굽힘 시험 및 굽힘 수치해석을 통하여 평가하였다. 25℃ 온도조건에서 풍속이 0 m/s 일 때, 태양 전지 셀의 최대 온도는 149.7℃이다. 풍속이 2.5 m/s로 증가되었을 경우, 태양 전지의 온도는 66.2℃로 크게 감소되었다. 또한 풍속이 5 m/s 인 경우, 태양 전지의 온도는 48.3℃로 급격히 감소함을 알 수 있었다. 주변 온도 또한 태양 전지의 작동 온도에 영향을 미친다. 2.5 m/s의 풍속에서 주변 온도가 33℃로 증가할 경우, 태양 전지의 온도는 74.2℃로 약간 증가하였다. 따라서 태양 전지 셀의 온도에 영향을 미치는 가장 중요한 인자는 풍속으로 인한 열 방출 효과임을 알 수 있었다. 또한 태양 전지의 최대 온도는 사용된 소재들의 유리 전이 온도보다 낮기 때문에, 열 변형 및 모듈의 열화 가능성은 매우 낮을 것으로 예측된다. 제작된 태양전지 모듈은 굽힘 반경 7 mm까지 굽힐 수 있어 비교적 우수한 유연성을 갖고 있었다. 또한 향후 neutral plane 해석을 통하여 태양전지 셀을 neutral plane에 위치시키면 유연성이 크게 증가할 것으로 예측된다.

• 태양에너지
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• 제18권1호
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• pp.99-109
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• 1998

공기조화 설비에 있어서 시스템의 성능을 향상시키고 에너지의 유효이용 및 경제성을 높일 수 있는 빙축열 시스템에 대한 연구이다. Ice Ball을 내장한 빙축열조를 횡형 사각형과 입형 원통형 축열조에 대하여 조내로 유입하는 브라인의 유량(2, 4, 6LPM)과 온도(-3, -5, $-7^{\circ}C$)를 변화시키고, 또한 유입 브라인의 유동을 상 하향유동으로 하면서 빙축열조내의 온도분포를 파악하여 열유동 특성 및 빙충전율에 대하여 고찰하였다. 연구결과 빙축열조내 열성층을 향상시키기 위해서는 조내 유입 브라인의 유동이 상향 압출흐름이어야 한다는 것을 알았다.

• Advances in nano research
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• 제13권5호
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• pp.475-485
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• 2022

Crystalline silicon photovoltaic cells have advantages of zero pollution, large scale and high reliability. A major challenge is that sunlight wavelength with photon energy lower than semiconductor band gap is converted into heat and increase its temperature and reduce its conversion efficiency. Traditional cooling PV method is using water flowing below the modules to cool down PV temperature. In this paper, the idea is proposed to reduce the temperature of the module and improve the energy conversion efficiency of the module through the modulation of the solar spectrum. A spectrally selective nanofilm reflector located directly on the surface of PV is designed, which can reflect sunlight wavelength with low photon energy, and even enhance absorption of sunlight wavelength with high photon energy. The results indicate that nanofilm reflector can reduce spectral reflectivity integral from 9.0% to 6.93% in 400~1100 nm wavelength range, and improve spectral reflectivity integral from 23.1% to 78.34% in long wavelength range. The nanofilm reflector can reduce temperature of PV by 4.51℃ and relatively improved energy conversion efficiency of PV by 1.25% when solar irradiance is 1000 W/m². Furthermore, the nanofilm reflector is insensitive in sunlight's angle and polarization state, and be suitable for high irradiance environment.

• 태양에너지
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• 제8권1호
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• pp.13-21
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• 1988

Heat transfer phenomena in a high-temperature heat storage unit were investigated using molten salts. Carbonate salt, an equimolar mixture of $Li_2CO_3$ and $K_2CO_3$, which melts at $505^{\circ}C$ with a latent heat of 82 cal/g, was selected as the most promising latent heat storage material based on its low cost and excellent thermophysical properties at moderately high temperatures. It was also found that nitrate salts were good candidates of sensible heat storage materials. For the carbonate salt to be utilized commercially, however, several means of enhancing thermal recovery must be explored by promoting heat conduction through the solid salt formed during the heat discharge period. These would be achieved by the additions of aluminum screens and wool, and stainless fins. Finally, experimental results of moving boundary of phase change were well compared with predictied values obtained from the approximate solution.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2011년도 추계학술발표대회 논문집
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• pp.202-207
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• 2011

This study has measured indoor temperature and relative humidity and evaluated it for one year by selecting Chungnam's rural areas for improving indoor environment of rural housing in the circumstance that the environment of housing is poor due to deterioration of rural housing. As a result of its evaluation, the indoor temperature difference by household appeared to be more than $13^{\circ}C$, and it was measured that the indoor temperature was mostly low. A difference of more than 40% in case of relative humidity occurred, so the difference of the indoor environment by household was clear. In case of the thermal comfort zone, the number of households that are distributed to more than 50% of a thermal comfort criterion in the winter was only 3 households, rather than the summer.

• 한국태양에너지학회 논문집
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• 제28권3호
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• pp.35-44
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• 2008

In this study, the experiment of the measuring of four different types of flooring materials' thermal characteristics was conducted and examined during the summer. The experimental materials were arranged on the existing slab of the roof, and then its thermal characteristics were examined from the point of view of thermal radiation analysis. The aim of this study is ultimately to draw the fundamental data for improvements in a building's thermal function and reduce the urban heat island phenomena through optimizing the thermal characteristics of the surface covering materials of a building. The results from this study are as follows; 1) Each experimental material's albedo was calculated as 0.83 on the aluminum panel, 0.40 on the rock block, 0.37 on the wood deck and 0.21 on the concrete. It shows that the concrete material, which has the lowest short wave reflective rate, absorbed the most radiation energy and the aluminium panel has absorbed the lowest radiation energy. 2) From the each experimental object's value of the long wave radiation, the concrete material measured the highest, at $628W/m^2$, and the aluminium panel measured the lowest at $412W/m^2$. Therefore, it verifies that the experimental objects' own radiation rate determines the amount of the long wave radiation. 3) The degree of energy absorbency of a building's surface covering materials is greatly influenced by its own albedo and radiation rate, Therefore, it needs to be considered for the improvements in a building's thermal function and reducing the urban heat island phenomena. 4) According to the evaluation result of the each experimental object's overall heat transmission screening function on the roof of a building, the wooden deck is proven to be an excellent material for excluding the outside temperature differences effectively with its characteristic of low heat capacity and conduction. Also its surface temperature on the roof slab and the temperature difference during the day were both measured at low.

• 태양에너지
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• 제17권3호
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• pp.23-33
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• 1997

본 연구에서는 잠열온도 조절에 관한 이론과 상변화 잠열재의 결정핵형성이론 그리고 PCM 결정화 모델을 정립하고, 농산물 저온 저장에 이용할 수 있는 냉축열 잠열재로 $H_2O$를 선정하여 NaCl을 온도 조절제로 잠열온도를 조절하였으며, 상변화 사이클에 의한 열특성 변화 추이와 물성의 안정성을 실험적으로 분석하였다.

• 태양에너지
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• 제19권2호
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• pp.57-65
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• 1999

[ $H_2O$ ]-NaCl혼합물을 냉축열재로 선택하였으며, 이 혼합물의 상변화온도를 몰농도 변화에 의하여 조절하였다. 그리고 고농도와 저농도의 NaCl과 $H_2O$가 ion-dipole interaction으로 결합하는 구조를 그림으로 가시화하고 가열, 냉각과정에서 $H_2O$-NaCl이 동결, 융해하는 현상을 도시하므로서 융해와 동결과정에서 상변화온도가 2단계로 나타나는 구조적 원인을 구명하였으며, NaCl의 농도변화에 따른 상변화온도를 이론적으로 분석하므로서 실험 및 이론분석 결과의 타당성을 증명할 수 있도록 하였다.

• 한국전산유체공학회지
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• 제13권2호
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• pp.48-54
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• 2008

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 launched by ARIANE 5. Ka-band components are installed on South panel, where single solar array wing is mounted. Radiators, embedded heat pipes, external heat pipe, insulation blankets and heaters are utilized for the thermal control of the satellite. The Ka-band payload section is divided several areas based on unit operating temperature in order to optimize radiator area and maximize heat rejection capability. Other equipment for sensors and bus are installed on North panel. The ocean and meteorological sensors are installed on optical benches on the top floor to decouple thermally from the satellite. During the transfer orbit operation, satellite will be under severe thermal environments due to low dissipation of components, satellite attitudes and LAE(Liquid Apogee Engine) firing. This paper presents temperature and heater power prediction and validation of thermal control design during transfer orbit operation.