• Carbon letters
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• 제10권3호
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• pp.181-189
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• 2009

Activated carbon spheres (ACS) were prepared at different heating rates by carbonization of the resole-type phenolic beads (PB) at $950^{\circ}C$ in $N_2$ atmosphere followed by activation of the resultant char at different temperatures for 5 h in $CO_2$ atmosphere. Influence of heating rate on porosity and temperature on carbon structure and porosity of ACS were investigated. Effect of heating rate and temperature on porosity of ACS was also studied from adsorption isotherms of nitrogen at 77 K using BET method. The results revealed that ACS have exhibited a BET surface area and pore volume greater than $2260\;m^2/g$ and $1.63\;cm^3/g$ respectively. The structural characteristics variation of ACS with different temperature was studied using Raman spectroscopy. The results exhibited that amount of disorganized carbon affects both the pore structure and adsorption properties of ACS. ACS were also evaluated for structural information using Fourier Transform Infrared (FTIR) Spectroscopy. ACS were evaluated for chemical composition using CHNS analysis. The ACS prepared different temperatures became more carbonaceous material compared to carbonized material. ACS have possessed well-developed pores structure which were verified by Scanning Electron Microscopy (SEM). SEM micrographs also exhibited that ACS have possessed well-developed micro- and meso-pores structure and the pore size of ACS increased with increasing activation temperature.

• 한국산학기술학회논문지
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• 제13권8호
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• pp.3307-3314
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• 2012

농어촌 주택 표준모델에 대한 연간 건물에너지요구량을 DesignBuilder를 사용하여 계산하였다. 실내설정온도, 외벽의 열관류율, 창호타입, 환기량을 변화시키며 건물의 설계/운영 변수들이 에너지요구량에 미치는 영향을 분석하였다. 건물의 크기와 상관없이 난방에너지요구량이 냉방에너지요구량보다 더 큰 것으로 나타났다. 단열재 두께를 증가시켜 외벽의 열관류율을 감소시키면 단열효과의 증가로 난방에너지요구량은 감소하지만 냉방에너지요구량이 증가한다. 하지만 외벽의 열관류율 조절을 통한 난방에너지요구량의 절감에는 한계가 있으므로 외부에 직접 노출된 외벽의 면적을 최소화하는 것이 더 효과적인 것으로 판단된다. 계산에 사용된 4가지 창호 중 일반 이중창호가 난방에너지요구량 측면에서 가장 유리한 것으로 나타났다. 침기량은 일정하게 유지하고 단위시간당 환기량을 증가시킨 경우 냉방에너지요구량은 큰 변화가 없었으나 난방에너지요구량이 증가하였다. 실내의 공기질이 만족되는 범위 내에서 환기량을 최소화하는 것이 연간 건물에너지요구량을 줄이는데 유리한 것으로 판단된다.

• 한국농공학회논문집
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• 제47권2호
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• pp.45-52
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• 2005

Biomass is one of the most competitive renewable energy resource and can be used for heating for rural applications. A economic assessment was made of biomass heating, using the tool BIOH2000 from $RETScreen^{\circledR}$ International Clean Energy Decision Support Centre. For a 260kW heating system for 50 farm houses, the assessment showed a very promising results. Internal rate of return was $19.7\%$ and year-to-positive cash flow was 5.1 years. Relative price of biomass over fossil fuel significantly affected the economic feasibility of the project. Heating demand was directly related to annual demand of biomass and economic feasibility. Relative cost of distribution pipe over the total initial costs also affected the economic feasibility of the project. The economic feasibility was expected to be improved by the probable greenhouse emission reduction credit and reduction of initial costs through utilizing existing heating system for peak or back up heating system.

• 설비공학논문집
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• 제23권11호
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• pp.762-768
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• 2011

We use floor radiant heating system in the house of commons in winter Floor radiant heating system, which transfer heat by radiation, is one of the energy efficient and comfortable systems that. Floor radiant heating system is configured to be controlled by the room for energy-saving. Proper flow rate to a comfortable heating in the room is important. However, Using a constant speed circulation pump in separate rooms, heating system may cause an imbalance because of the difference of length of coil when operating in the rooms. In this study, our Research team examined heating imbalance due to the variation length through the coil length changes and flow control of the circulation pump.

• 대한설비공학회지:설비저널
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• 제16권2호
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• pp.140-153
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• 1987

Main objective of this study is to provide heating cost allocation method according to the amount of heating energy consumption in apartments. Heating energy consumptions are calculated by DOE-2.1A program. As a result, heat loss ratio in Ondol heating system, heating cost coefficients of apartments and its using method is presented. Maximum heating cost coefficient rate is 2.63.

• 생물환경조절학회지
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• 제5권1호
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• pp.57-64
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• 1996

To use effectively the solar energy in greenhouse heating, a high performance solar collector should be developed. And then the size of the solar collector and thermal storage tank should be determined through the calculation of heating load. The solar collector must be set in the optimum tilt angle and direction to take daily solar radiation maximally, and the flow rate of heat transfer fluid through the solar collector should be kept in the optimum range. In this research, the performance tests of a capillary tube solar collector were performed to determine the optimum water flow rate and the results summarized as follows. 1. The regressive equations for efficiency estimations of the capillary tube solar collector in the open loop were modeled in the water flow rate of 700-l,000 $\ell$/hr. 2. The optimum water flow rate of the solar collector was estimated by the second order polynomial regression and the maximum efficiency was 80% at the water flow rate of 850 $\ell$/hr. 3. The solar thermal storage system consisted of a capillary tube solar collector and a water storage tank was tested at the water flow rate of 850 $\ell$/hr in the closed loop, and obtained the solar thermal storage efficiency of 55.2%. 4. As the capillary tube solar collector engaged in this experiment was made of non-corrosive polyolefin tubes, its weight was as light as 1/30 of the flat plate solar collector made of copper tubes. Therefore it was considered to be suitable for the greenhouse heating system.

• 대한기계학회논문집B
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• 제29권2호
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• pp.169-179
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• 2005

Nucleate boiling experiments on heating surface of constant wall temperature were performed using R113 for almost saturated pool boiling conditions. A microscale heater array and Wheatstone bridge circuits were used to maintain a constant wall temperature condition of heating surface and to measure the heat flow rate with high temporal and spatial resolutions. Bubble images during the bubble growth were taken as 5000 frames per second using a high-speed CCD camera synchronized with the heat flow rate measurements. The bubble growth behavior was analyzed using the new dimensionless parameters for each growth regions to permit comparisons with previous experimental results at the same scale. We found that the new dimensionless parameters can describe the whole growth region as initial and later (thermal) respectively. The comparisons showed good agreement in the initial and thermal growth regions. In the initial growth region including surface tension controlled, transition and inertia controlled regions as divided by Robinson and Judd, the bubble growth rate showed that the bubble radius was proportional to $t^{2/3}$ regardless of working fluids and heating conditions. And in the thermal growth region as also called asymptotic region, the bubble showed a growth rate that was proportional to $t^{1/5}$, also. Those growth rates were slower than the growth rates proposed in previous analytical analyses. The required heat flow rate for the volume change of the observed bubble was estimated to be larger than the heat flow rate measured at the wall. Heat, which is different from the instantaneous heat supplied through the heating wall, can be estimated as being transferred through the interface between bubble and liquid even with saturated pool condition. This phenomenon under a saturated pool condition needs to be analyzed and the data from this study can supply the good experimental data with the precise boundary condition (constant wall temperature).

• 한국항공우주학회지
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• 제32권8호
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• pp.101-108
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• 2004

본 연구에서는 비행체 구조재료인 A12024-T3에 대하여 공력가열환경을 모사할 수 있는 복사가열기를 제작하였으며 $1^{\circ}C/sec{\sim}30^{\circ}C/sec$ 가열률 범위에서 열기계적 인장특성을 평가하였다. 가열환경에 따른 재료강도 평가를 위하여 급속가열 인장시험 결과와 일정 온도로 30분 노출후의 인장시험결과를 항복응력 측면에서 비교 고찰하였다. 급속가열 인장시험 결과로부터 시간-온도계수를 응용한 가열률-항복온도 계수를 도출하였으며, 항복응력을 가열률과 항복온도로 표현되는 실험적 master 수식을 제안하였다. 본 연구 결과를 통하여 획득 된 급속가열 안장시험결과들은 초음속 비행체 설계시 선정재료의 안전여유를 판단하는 기초자료로 활용될 수 있다.

• 생물환경조절학회지
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• 제13권4호
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• pp.245-250
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• 2004

본 연구는 조조가온기간이 시설오이의 생육과 수량 및 난방부하에 미치는 영향을 구명하고자, 일출전에 난방온도를 올려서 $12^{\circ}C$에서 $16^{\circ}C$로 올려서 가온하는 기간을 2시간, 1시간 및 0시간을 비교하였다. 보온커텐을 열기 직전$(08:50\~09:00)$의 엽온은 조조가온을 하지 않는 것에 비해 1시간 가온이 $3.3^{\circ}C$, 2시간 가온이 $4.1^{\circ}C$각각 높았다. 오이 잎의 광합성, 기공전도도 및 증산량은 2시간 조조가온이 가장 좋았으나 1시간 가온과의 차이가 근소하였고 조조가온을 하지 않은 것은 현저히 감소하였다. 오이 잎의 무기성분함량은 유의적 차이는 없었으나 2시간, 1시간, 0시간 순으로 높은 경향이었다. 정식 이후의 초기생육은 1시간과 2시간 가온이 비슷하게 빨랐으나 조조가온을 하지 않는 것은 현저히 저조하였다. 과실 수량은 조조가온을 하지 않는 것에 비해 1시간 가온이 $11\%$, 2시간 가온이 $15\%$ 각각 증가되었다. 연료소모량은 조조가온하지 않는 것에 비해 1시간 가온이 $12\%$, 2시간 가온이 $22\%$ 각각 많았다. 생산물의 증수량과 연료소모량을 감안할 때 조조 가온하지 않는 것에 비해 가온한 것이 경영상 유리하였다.

• 설비공학논문집
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• 제19권8호
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• pp.577-584
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• 2007

A variable-flow-rate balancing valve has been developed and optimized to apply to a distributor in a hot-water heating system. Fluid dynamic performance of the system was evaluated by comparing the results with the previous pressure difference control valve (PDCV) system. In view of the variations of pressure drop and flow rate according to the sequential closing of the control valves, the present system which is named "smart system distributor", is very stable without a certain flow rate concentration. The level of pressure drop variation is also low as compared with the previous system with a PDCV. In view of the occurrence of cavitation, the present system is quite superior to the previous system because the instantaneous pressures at all sections are much higher than the vapor pressure. On the other hand, the previous system has a possibility of cavitation when one or more control valves are closed.