• 대한전기학회논문지:전력기술부문A
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• 제53권2호
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• pp.97-103
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• 2004

CHP system supplies electricity and heating together with high efficiency. Current utility's CHP system uses electric power by itself and sells thermal energy to KDHC(Korea District Heating Corporation). CHP's operation cost except sales revenue of heating was covered by the sale revenue of electricity. Thus Electric generation cost in district Heating CHP system has close relationship with the level of heating price. However, after the restructuring of electricity industry, the operation cost could not be covered by sales revenue of heating and electricity. This loss was compensated by energy subsidy program in the electric power industry infrastructure fund. This paper suggests reasonable evaluation and improvement methods of the loss calculation of CHP system utilizing the infrastructure fund efficiency In terms of the direction of support by the fund, it provides the methods to prevent inefficient operation through setting up the upper limit of subsidy and to improve the loss calculation. Moreover, it suggest fixed rate support by heating supply level and reducing subsidy gradually for an efficient operation of CHP system.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.279-282
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• 2002

Recently, gas turbines for power generation adopt multistage DLN(Dry Low NOx) type combustion, where diffusion combustion is applied at low load and, with increase in load, the combustion mode is changed to lean premixed combustion to reduce NOx emissive concentration. However, during the mode changeover from diffusion to premixed flame, unfavorable phenomena, such as flashback, high amplitude combustion oscillations, or thermal damage of combustor parts could frequently occur. In the present study, to apply for the analysis of such unfavorable phenomena, three-dimensional CFD investigations are carried out to compare the detailed flow characteristics and temperature distribution inside the gas turbine combustor before and after combustion mode changeover. The fuel considered here is pure methane gas. A standard $k-{\varepsilon}$ turbulence model with wall function and a P-N type radiation heat transfer model, have been utilized. To analyze the complex geometric effects of combustor parts on combustion characteristics, fuel nozzles, a swirl vane f3r fuel-air mixing, and cooling air holes on the combustor liner wall, are included in this simulation.

• 설비공학논문집
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• 제28권10호
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• pp.381-386
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• 2016

An optimization algorithm is developed based on a simulation case of a single family house model equipped with PV arrays. To increase the nationwide use of PV power generation facilities, a market-competitive electricity price needs to be introduced, which is determined based on the time of use. In this study, quadratic programming optimization was applied to minimize the electricity bill while maintaining the indoor temperature within allowable error bounds. For optimization, it is assumed that the weather and electricity demand are predicted. An EnergyPlus-based house model was approximated by using an equivalent RC circuit model for application as a linear constraint to the optimization. Based on the RC model, model predictive control was applied to the management of the cooling load and electricity for the first week of August. The result shows that more than 25% of electricity consumed for cooling can be saved by allowing excursions of temperature error within an affordable range. In addition, profit can be made by reselling electricity to the main grid energy supplier during peak hours.

• 세라미스트
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• 제22권4호
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• pp.402-416
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• 2019

The development of next-generation secondary batteries, including lithium-ion batteries (LIB), requires performance enhancements such as high energy/high power density, low cost, long life, and excellent safety. The discovery of new materials with such requirements is a challenging and time-consuming process with great difficulty. To pursue this challenging endeavor, it is pivotal to understand the structure and interface of electrode materials in a multiscale level at the atomic, molecular, macro-scale during charging / discharging. In this regard, various advanced material characterization tools, including the first-principle calculation, high-resolution electron microscopy, and synchrotron-based X-ray techniques, have been actively employed to understand the charge storage- and degradation-mechanisms of various electrode materials. In this article, we introduce and review recent advances in in-situ synchrotron-based x-ray techniques to study electrode materials for LIBs during thermal degradation and charging/discharging. We show that the fundamental understanding of the structure and interface of the battery materials gained through these advanced in-situ investigations provides valuable insight into designing next-generation electrode materials with significantly improved performance in terms of high energy/high power density, low cost, long life, and excellent safety.

• 한국철도학회논문집
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• 제11권4호
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• pp.410-416
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• 2008

본 연구에서는 '2003년 산업연관표'를 사용하여 우리나라의 철도운송산업이 국내 운송산업 전체에서 차지하는 위상 및 철도운송산업과 여타산업의 관계적 특징에 대하여 살펴보았다. 그리고 산업연관분석 연구방법을 사용하여 국내 철도운송산업의 생산활동이 403개 여타 기본산업에 미치는 경제적 파급효과에 대해서 분석하였다.

• 동력기계공학회지
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• 제10권4호
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• pp.25-30
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• 2006

This paper represents the numerical analysis in unsteady state on the variation of diameter and environmental velocity of carbon heating source. In general heating system, the oil and sheath heater is widely used, but these systems have many problems. So, the heating source with carbon ingredient has been researched in many country about manufacture, thermal and electrical properties. In this research, the carbon heating source was studied through numerical analysis on several conditions of unsteady state, heat generation, diameter and environmental velocity. The temperature distributions at steady state are appeared as a non-proportional linear pattern with variations of environmental velocity due to the Nesselt number with convective heat flux is proportioned to 0.805 of Reynolds number. As the radius is increasing, the temperature distributions is appeared the minus tilt because of the environmental condition is cooling by constant temperature. So, the correlation equation between temperature at steady state and environmental velocity was obtained.

• 동력기계공학회지
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• 제21권3호
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• pp.30-36
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• 2017

Carbon fiber shows excellent heat generation value and thermal efficiency comparing with the metallic materials because of its far infrared-rays and radiant heat. So, high performance and economic steam boiler system for the industry can be manufactured by using the carbon fiber heater. The far infrared ray radiation rate was more than 90 % of carbon fiber. Steam boiler system with carbon fiber heater in this study is made up of heating section. In the proof test of steam boiler, the aimed temperature and dwelling time were at $500^{\circ}C$ for 8,000 hours, $600^{\circ}C$-3,000 hours, and $700^{\circ}C$-1,000 hours. The temperature rise rate of steam boiler with carbon fiber heater was about 40% faster than that of the conventional boiler.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2008년도 춘계학술발표대회 논문집
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• pp.209-214
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• 2008

Since the direct normal insolation is a main factor for designing any solar thermal power system, it is necessary to evaluate its characteristics all over the country. We have begun collecting direct normal insolation data since December 1992 at 16 different locations and considerable effort has been made for constructing a standard value from measured data at each station. KIER(Korea Institute of Energy Research)'s new data will be extensively used by solar thermal concentrating system users or designers as well as by research institutes. From the results, we can conclude that 1) Yearly mean 2.67 kWh/$m^2$/day of the direct normal insolation was evaluated for all days all over the 16 areas in Korea. 2) All day's direct normal insolation of spring and summer were 2.91 kWh/$m^2$/day and 2.23 kWh/$m^2$/day, and for fall and winter their values were 2.78 kWh/$m^2$/day and 2.77 kWh/$m^2$/day respectively. So, spring, fall and winter were higher, and summer was lower than the yearly mean value

• 한국세라믹학회지
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• 제55권1호
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• pp.44-49
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• 2018

The use of fossil fuels is steadily increasing. The thermal power generation industry uses a lot of energy and emits a large amount of greenhouse gases. On the other hand, a desulfurization facility can be installed to remove sulfur content during boiler combustion process of the power plant. Dry desulfurized gypsum generated from dry desulfurization facilities is suitable as a $CO_2$ absorbing material due to the presence of CaO. In this study, the carbonation properties of dry desulfurized gypsum were investigated by carbonizing dry desulfurized gypsum via mixing with water and stirring. As a result of microstructural, XRD and thermal analyses of the carbonized dry desulfurized gypsum, the carbonation age was found to be suitable for 16 h. Dry desulfurized gypsum absorbs about 16% of $CO_2$ per unit weight.

• 한국태양에너지학회 논문집
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• 제35권2호
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• pp.53-62
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• 2015

Boiling heat transfer characteristic is very important in the various industries such as solar thermal system, power generation, heat exchangers, cooling of high-power electronics components and cooling of nuclear reactors. Therefore, in this study, boiling heat transfer characteristics such as critical heat flux (CHF) and heat transfer coefficient under the pool boiling state were tested using graphene nanofluids. Graphene used in this study, which have the same thermal conductivity but with different sizes. The experimental results showed that the highest the CHF and boiling heat transfer coefficient increase ratio for graphene nanofluids was at the 0.01 vol.%. At the present juncture, the CHF and boiling heat transfer coefficient increase ratio of the small-sized graphene nanofluids was higher than the large-sized graphene nanofluids.