• 한국태양에너지학회 논문집
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• 제25권2호
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• pp.1-8
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• 2005

On-off differential controller is one of the very important components which affect the system performance of the active solar thermal system. In this study, analyses were made regarding the influence of "on-off" setting temperature on the system efficiency and on the electrical consumption by circulation pump. This study was performed by experiment as well as the computer simulation using TRNSYS program. The simulation system was developed in this study was verified the its reliability by the experimental results. As a results, the turn off temperature(${\Delta}T_{off}$) is much more influence than the turn on temperature(${\Delta}T_{on}$) on the system efficiency. It is more clear and sensitivity in winter season. Finally the optimum on-off setting value and the system on-off pattern according to the several different kind of system was also represented.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2011년도 추계학술발표대회 논문집
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• pp.60-67
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• 2011

A photovoltaic/thermal(PVT)solar system is the solar technology that allows for simultaneous conversion of solar energy into both electricity and heat. This paper compared the performance of PVT system with a conventional PV module and solar collector and analyzed electrical and thermal efficiency of PVT system in terms of solar irradiance and inlet temperature of the working fluid. Based on the experimental data, thermal and electrical efficiencies of the glazed PVT system were 57.9% and 14.27% under zero reduced temperature condition which were lower by 13.6% than the solar thermal absorber plate and by 0.08% than the PV module respectively. For the unglazed PVT system, it had lower thermal efficiency than the solar thermal absorber plate but higher electrical performance than the PV module due to the cooling effect by the working fluid. However, total efficiency of the glazed PVT system was 72.2% which was higher than combined efficiencies of the solar collector and PV module. Besides, total efficiency of the PVT system would be much higher if calculated based on unit area.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2006년도 하계학술발표대회 논문집
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• pp.1069-1074
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• 2006

Heat loss by window in building occupies about 1/4 of energy amount used building. Therefore, high thermal insulation of windows system can speak as very important part in save energy of building. in this research, After select most suitable frame design and Glazing system for high thermal insulation of windows, execute simulation of mixing frame and Glazing System. Also, manufacture windows with the result and execute verification experiment, with verified simulation, this research evaluated thermal insulation performance of window by Glazing System's change.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 추계 학술발표회
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• pp.325-335
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• 2010

A new geothermal energy source obtained from a tunnel structure has been studied in this paper. The geothermal energy is extracted through a textile-type ground heat exchanger named "Energy Textile" that is installed between a shotcrete layer and a guided drainage geotexitle. A test bed was constructed in an abandoned railway tunnel to verify the geothermal heat exchanger system performed by the energy textile. To evaluate the applicability of the energy textile, we measured the thermal conductivity of shotcrete and lining samples which were prepared in accordance with a common mixture design. An overall performance of the energy textile installed in the test bed was evaluated by carrying out a series of in-situ thermal response test. In addition, a 3-D finite volume analysis (FLUENT) was adopted to simulate the operation of the ground heat exchanger being encased in the energy textile with the consideration of the effect of the shotcrete and lining thermal conductivity.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2009년도 하계학술발표대회 논문집
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• pp.58-63
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• 2009

A ground-loop heat exchanger for the ground source heat pump system is the core equipment determining the thermal performance and initial cost of the system. The size and performance of the heat exchanger is highly dependent on the ground thermal properties - the ground effective thermal conductivity, the borehole thermal resistance and the undisturbed ground temperature. Nowadays, precast concrete piles using steel reinforced precast concrete piles - energy piles - are used to reduce the installing cost of the ground-loop heat exchanger. We were carried out some tests to investigate the effects of some parameters such as borehole length, grouting materials and U-tube configuration of the energy piles. 4 concrete piles, each measuring $250mm{\sim}400mm$ in diameter and approx. 10m in length, and rigged with single spiral and 3 U-tube loop of $16mm{\times}2.3mm$ PB piping. The thermal response tests were conducted using a testing device for 4-different ground-loop heat exchangers. During the heating period, the energy piles absorb the heat of 0.89kW to 1.37kW.

• 한국태양에너지학회 논문집
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• 제31권3호
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• pp.80-88
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• 2011

Heliostat in the tower type solar thermal power plant is a sun tracking mirror system to reflect the solar energy to the receiver and the optical performance of it affects to the efficiency of whole power plant most significantly. Thus a solid understanding of heliostat's energy concentration characteristics is the most important step in designing of the heliostat field and the whole power plant. The work presented here is the analysis of energy concentration characteristics of heliostat used in 200kW solar thermal power plant, where the receiver located at 43m high in tower has $2{\times}2$m rectangular shape. The heliostat reflective surface is formed by 4 of $1{\times}1$m flat plate mirror facet and the mirror facet is mounted on the spherical frame. The direct normal incident radiation models in vernal equinox, summer solstice, autumnal equinox and winter solstice are first derived from the actually measured data. Then the intercept ratio, heat flux distribution and total energy collected at the receiver for the heliostats located in the various places of the heliostat field are investigated. Finally the effect of mirror facet installation error on the optical performance of the heliostat is analyzed.

• 태양에너지
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• 제9권2호
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• pp.14-21
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• 1989

The heat transfer analysis is performed on unloaded solar utilization dryer, and thermal performance for a prototype model while drying red-pepper is also investigated. Results of theoretically derived thermal equations are in good agreement with experimental data. This constructed feature of the prototype demonstrates the excellent technical drying performance. Finally, this paper recommends the further work to develop advanced and economic solar utilization multi-purpose dryer.

• KIEAE Journal
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• 제12권3호
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• pp.41-46
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• 2012

The building envelope is important specially for saving energy consumption of residential buildings. but Apartment houses in Korea commonly have inside insulation system which have constantly arisen thermal bridges, the risk of heat loss, as a necessity. This study aims to evaluate integrated insulation performance according to the different shapes of external walls, adjacent to windows. The thermal performance analysis was carried out by Equivalent U-value and using the three-dimensional heat transfer computer simulation (TRISCO-RADCON), under nine different cases of comparing among three each of different bases(current standard model, 30percent energy saving model and 60percent energy saving model). The heating and the cooling load were also compared between two cases (standard U-value and Equivalent U-value) of three each of different bases, using the Building energy simulation which is based on DOE-2.1 analysis. As results, it turns out that if the Equivalent U-value is considered on the envelope analysis, the heat flow loss will be increasing more than the standard U-value, and if heat insulation property of the residential building reinforced rather than current, the rate of influences on the thermal bridges would be extremely expanded. In addition, it is shown that annual heating loads of the apartment house with applied Equivalent U-value substantially increased by more than 15 percent compared to those with the existing U-value, but annual cooling loads were negligibly affected.

• Journal of Ceramic Processing Research
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• 제20권1호
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• pp.48-53
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• 2019

Carbon fiber reinforced SiC composites (C/SiC) have high-temperature stability and excellent thermal shock resistance, and are currently being applied in extreme environments, for example, as aerospace propulsion parts or in high-performance brake systems. However, their low thermal conductivity, compared to metallic materials, are an obstacle to energy efficiency improvements via utilization of regenerative cooling systems. In order to solve this problem, the present study investigated the bonding strength between carbon fiber and matrix material within ceramic matrix composite (CMC) materials, demonstrating the relation between the microstructure and bonding, and showing that the mechanical properties and thermal conductivity may be improved by treatment of the carbon fibers. When fiber surface was treated with a nitric acid solution, the observed segment crack areas within the subsequently generated CMC increased from 6 to 10%; moreover, it was possible to enhance the thermal conductivity from 10.5 to 14 W/m·K, via the same approach. However, fiber surface treatment tends to cause mechanical damage of the final composite material by fiber etching.

• 설비공학논문집
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• 제23권6호
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• pp.430-440
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• 2011

The purpose of this study was to investigate the interactions between the thermal factors in existing thermal control methods and to find out the control logic that can create more comfortable thermal conditions. For it, four thermal control logics were developed：conventional temperature-based control; temperature-based and humidity-based control; PMV-based control; and TS-based control. Their performance was comparatively tested in the U.S. typical 5-story office building in two climate zones (Detroit, Michigan and Miami, Florida) for two seasons (winter and summer) incorporating IBPT (International Building Physics Toolbox) and Matlab/Simulink. Analysis on the thermal conditions and energy efficiency revealed that each control logic created comfortable conditions for their respective target, i.e., temperature, humidity, PMV or TS, but uncomfortable for others (e.g., temperature-based control logic maintained PMV or TS uncomfortably or vise versa). In addition, energy efficiency was significantly different by logics. In conclusion, it can be said that the overall thermal comfort can be improved by the adoption of the PMV and TS as a target variable and their economical benefits are expected in the hotter climate zones with the reduced cooling and dehumidifying energy consumptions.