• International Journal of Air-Conditioning and Refrigeration
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• v.6
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• pp.1-13
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• 1998

The basic heat transfer process that occurs in a building can best be illustrated by an electrical circuit network. Present paper reports the dynamic simulation of annual energy consumption in an office building by the thermal resistance capacitance network method. Unsteady thermal behaviors and annual energy consumption in an office building were examined in detail by solving the simultaneous circuit equations of thermal network. The results are used to evaluate the accuracy of the modified BIN method for the energy consumption analysis of a large building. Present thermal resistance-capacitance method predicts annual energy consumption of an office building with the same accuracy as that of response factor method. However, the modified BIN method gives 15% lower annual heating load and 25% lower cooling load than those from the present method. Equipment annual energy consumptions for fan, boiler and chiller in the HVAC system are also calculated for various control systems as CAV, VAV, FCU+VAV and FCU+CAV. FCU+CAV system appears to consume minimum annual energy among them.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.3 no.2
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• pp.9-15
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• 2007

Thermal conductivity of rocks is one of the most important parameters in designing a geothermal heat pump system, because heat exchange rate depends primarily on thermal conductivity of rocks. In this paper, the measurement methods of thermal conductivity, thermal conductivity of rocks, and heat exchange rate are discussed.

• Proceedings of the Korean Nuclear Society Conference
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• 2004.10a
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• pp.379-380
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• 2004

• Korean Journal of Food Science and Technology
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• v.29 no.1
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• pp.65-71
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• 1997

The energy supplied by motor of extruder, being known mostly to be dissipated as heat, was classified into two kinds of energy: a thermal energy by heat dissipation and a purely mechanical energy. The thermal energy was defined as a energy in terms of temperature rise and the mechanical energy as the motor energy minus the heat dissipated energy. A method to derive the thermal energy and the relative mechanical energy (the mechanical energy calculated regarding the mechanical energy at the lowest screw speed as zero) under the condition of constant barrel temperature was developed by which an extrusion case was analyzed. When extruding com grits with moisture $(27{\sim}37%)$ at low barrel temperature $({\leq}80^{\circ}C)$, the thermal energy slightly increased with increase in the moisture content, whereas the relative mechanical energy increased to a great extent. When increasing the screw speed, the thermal energy was nearly kept constant, whereas the relative mechanical energy largely varied. It is concluded that as the moisture content increases, the role of the mechanical energy becomes more effective than the heat energy dissipated from the motor energy.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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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.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.8 no.4
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• pp.8-16
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• 2012

The use of energy pile foundation has been increased for economic utilization of geothermal energy. This paper describes an experimental and numerical study on thermal response tests (TRTs) using W and 3U-shaped ground heat exchangers (GHEs) in precast-high strength concrete (PHC) energy piles. Ground thermal conductivity and borehole thermal resistance were measured and compared with those numerical analysis. W-shpaed GHE showed higher heat transfer behavior than 3U-shaped one because of different conditions such as pile size and volume of grout. That is, ground thermal conductivity using W-shaped GHE was higher than that of 3U shaped GHE, and borehole thermal resistance vice versa. The relative error of borehole resistance values between numerical and analytical solution was less than 5%.

• 한국태양에너지학회:학술대회논문집
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• 2008.11a
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• pp.25-29
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• 2008

Economic assessment of solar thermal power generation systems was carried out by calculating the levelized electricity cost. Four different commercial (or near commercial) solar thermal power systems (parabolic trough system, power tower system with saturated steam, power tower system with molten salts, and dish-stilting system) were considered for assessment. The assessment also included sensitivity analysis covering the effects of system capacity, direct normal insolation, and the system efficiency.

• Journal of Ceramic Processing Research
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• v.20 no.1
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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.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.6
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• pp.524-532
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• 2003

In this paper, a personal air-conditioning system considering the human thermal adaptability is analyzed. Although the conventional personal air-conditioner was proofed to be satisfactory in providing for the thermal comfort, it is being questioned on the term of its energy efficiency. Therefore, it is important and urgent to develop new types of personal air-conditioning system with sustainable control strategy that can ensure energy saving and thermal comfort simultaneously. In this study, we first examined the problems of the conventional personal air-conditioning system with field interview and laboratory experiment in terms of usage, management and thermal comfort, and proposed the energy-saving personal air-conditioning system considering the human thermal adaptation. Then a laboratory experiment was performed to analyze the characteristics of the human thermal comfort under severe indoor thermal conditions, which were controlled using a new personal air-conditioning unit designed according to the proposal. The results help to illustrate the alleviation effect of the new personal air-conditioning system, and indicate that the thermal alleviation time is useful to maintain the thermal comfort with efficient usage of energy.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.26 no.8
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• pp.388-393
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• 2014

Energy consumption unit in a building is classified according to uses of electricity, gas, and oil, and it has been studied steadily as a material for establishing policy standards for energy saving in buildings. Meanwhile, consumption unit in apartment house can be calculated differently according to its survey method and area standard. Therefore, with the necessity of reestablishing energy consumption unit, this study has researched thermal energy consumption, Supply dwelling area Exclusive dwelling area, completion year and housing type of 23,791 households of 31 complex in Daejeon. As a result, (1) there was about 20% difference between supply and exclusive dwelling areas. (2) On the basis of exclusive dwelling area, thermal energy consumption unit was calculated as $104.9kWh/m^2{\cdot}a$ in 2010, $104.6kWh/m^2{\cdot}a$ in 2011, and $107.7kWh/m^2{\cdot}a$ in 2012.