• 조명전기설비학회논문지
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• 제21권5호
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• pp.120-125
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• 2007

1997년 지구온난화 문제를 해결하기 위해 교토 기후협약이 체결되었고, 우리나라도 2013년부터 기후협약 규제가 거의 확실시 되고 있다. 우리나라 온실가스 배출량은 연간 약6억 톤이며, 그 중 CO2가 5억 톤이다. 특히 화석연료의 연소로 대부분의 전력을 생산하는 발전 산업은 우리나라 CO2 배출량의 20[%] 이상을 차지하고 있다. 따라서 발전소의 전력생산에 따른 화석연료의 소모량과 이에 따른 CO2 배출량을 monitoring하는 것이 매우 중요해졌다. 본 논문은 발전소의 성능시험 결과 얻어지는 입출력 특성계수와 IPCC(Intergovernmental Panel on Climate Change)의 온실가스 추계 방법론을 이용하여 순시 발전출력에 따른 CO2 대기배출량을 계산하는 방법을 제시하였다. 4모선 모형계통의 시뮬레이션을 통하여 전력계통의 조류계산과 발전소별 CO2 배출량을 연립 연산하는 예를 도시하였다.

• 대한기계학회논문집B
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• 제40권8호
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• pp.503-510
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• 2016

일반적으로 연소로는 연료의 연소과정에서 NOx, CO등의 공해물질을 배출한다. 본 연구는 소각연소로를 대상으로 2차 공기를 연소가스 흐름의 역방향으로 주입시키는 방법의 NOx 및 CO 배출특성에 대한 연구를 수행하였다. 연구의 주요변수는 1, 2차 공기의 유량비와 2차 공기의 투입 방향으로 설정하였다. 변수에 따른 NOx 및 CO 배출특성을 묘사하기 위해서 축소모형실험 연구를 수행하였다. 실험결과 1차 공기유량이 감소하고 2차 공기유량이 증가할수록 NOx가 감소되다가 일정 유량비 이상에서 다시 NOx가 다소 증가하는 형태가 나타났다. 역방향으로 빠른 유속의 2차 공기가 투입될 때 연소로 내부에 유동 재순환이 발생하여 혼합이 증가하고 이로 인해서 온도 영역이 고르게 분포되는 것으로 나타났으며 그 결과로서 thermal NOx의 저감 효과를 확인할 수 있었다. CO는 2차 공기가 역방향에서 높은 비율로 투입되는 조건이외에서는 측정되지 않았다. 측정된 경우도 CO의 농도는 2 ppm 이내로 안정적인 연소 조건으로 나타났다.

• 한국분말재료학회지
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• 제10권4호
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• pp.228-234
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• 2003

In the present study, the focus is on the synthesis of titanium carbide/cobalt composite powder by the spray thermal conversion process using metallic salt solution as the raw materials. Two types of oxide powders of Ti-Co-O system were prepared by the spray drying of two types of metallic salt solutions : titanium chloride-cobalt nitrate and $TiO_2$ powder-cobalt nitrate solutions. These oxide powders were mixed with carbon black, and then these mixtures were carbothermal reduced under a flowing argon atmosphere. The changes in the phase structure and thermal gravity of the mixtures during carbothermal reduction were analysed using XRD and TG-DTA. In the case of using the titanium chloride-cobalt nitrate solution, it could not be obtained TiC/Co composite powder due to contamination of the impurities during the spray drying of the solution. However, in tile case of using the $TiO_2$ powder-cobalt nitrate scullion, TiC-15 wt. %Co composite powder could be synthesized by the spray thermal conversion process. The synthesized TiC-15 wt. %Co composite powder at 120$0^{\circ}C$ for 2 hours has average particle size of 150 nm.

• Tribology and Lubricants
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• 제34권2호
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• pp.43-48
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• 2018

This paper presents the thermohydrodynamic analysis of tilting journal pad bearings supporting a power turbine rotor applied to a 250 kW super-critical $CO_2$ cycle. In the analysis, the generalized Reynolds equation and 3D energy equation are solved to predict oil film temperature and the 3D heat conduction equation is solved for pad temperature. The power turbine rotor is supported by two tilting pad bearings consisting of five pads with an oil supply block between the pads. Copper backing pads with higher thermal conductivity compared to steel backing pads are adopted to improve thermal management. The predicted maximum pad temperature is around $55^{\circ}C$ which is approximately $15^{\circ}C$ higher than oil supply temperature. In addition, the predicted minimum film thickness is 50 mm at a rotating speed of 5,000 rpm. These results indicate that there is no issue in the thermal behavior of the bearing. An operation test is performed with a power turbine module consisting of a power turbine, a reduction gear and a generator. Thermocouples are installed at the 75% position from the leading edge of the pad to monitor pad temperature. The power turbine uses compressed air at a temperature of $250^{\circ}C$ in its operation. The steady state pad temperatures measured in the test show good agreement with the predicted temperatures.

• 한국재료학회지
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• 제9권1호
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• pp.73-80
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• 1999

The effect of alloy compositions of the bond coating on the plasma sprayed-thermal barrier coatings was investigated. The performance of the coating composed of Rene80/NiCrAl/ZrO$_2$-CeO$_2$-Y$_2$O$_3$ and Rene80/CoNiCrAlY/ZrO$_2$-CeO$_2$-Y$_2$O$_3$was evaluated by isothermal and thermal cyclic test in an ambient atmosphere at 115$0^{\circ}C$. The failure of Rene80/NiCrAl/ZrO$_2$-CeO$_2$-Y$_2$O$_3$ coatings was occurred at the bond coating/ceramic coating interface while Rene80/CoNiCrAlY/ZrO$_2$-CeO$_2$-Y$_2$O$_3$ coating was failed at the substrate/bond coating interface after thermal cyclic test. The lifetime of Rene80/NiCrAl/ZrO$_2$-CeO$_2$-Y$_2$O$_3$coatings was longer than Rene80/CoNiCrAlY/ZrO$_2$-CeO$_2$-Y$_2$O$_3$coating. The oxidation rate of the NiCrAl bond coating examined by TGA was lower than CoNiCrAlY bond coatings. In summary, these results suggest that Rene80/CoNiCrAlY/ZrO$_2$-CeO$_2$-Y$_2$O$_3$system as thermal barrier coating be not suitable considering the durability of the coating layer for high temperature oxidation and thermal stress.

• 한국재료학회:학술대회논문집
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• 한국재료학회 1997년도 한국재료학회 춘계학술발표회
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• pp.11-11
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• 1997

• 한국자동차공학회논문집
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• 제16권1호
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• pp.37-44
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• 2008

The global warming potential (GWP) of $CO_2$ refrigerant is 1/1300 times lower than that of R134a. Furthermore, the size and weight of the automotive heat pump system can decrease because $CO_2$ operates at high pressure with significantly higher discharge temperature and larger temperature change. The presented $CO_2$ heat pump system was designed for both cooling and heating in fuel cell vehicles. In this study, the performance characteristics of the heat pump system were analyzed for heating, and results for performance were provided for operating conditions when using recovered heat from the stack coolant. The performance of the heat pump system with heater core was compared with that of the conventional heating system with heater core and that of the heat pump system without heater core, and thus the heat pump system with heater core showed the best performance among the selected heating systems. On the other hand, the heating performance of two different types of coolant/air heat pump systems with heater core was compared each other at various coolant inlet temperatures. Furthermore, to use exhausted thermal energy through the radiator, experiments were carried out by changing the arrangement of a radiator and an outdoor evaporator, and quantified the heating effectiveness.

• 설비공학논문집
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• 제29권4호
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• pp.195-201
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• 2017

In this study, the viscosity of a $CO_2-gas$ mixture was investigated for the transportation of the captured $CO_2-gas$ in pipelines and for the designing of a thermal system, both of which involve the utilization of the $CO_2-gas$ mixture. The viscosities of the $CO_2-gas$ mixture, $CO_2+CH_4$, $CO_2+H_2S$, and $CO_2+N_2$ were predicted using three different models as follows : Chung, TRAPP, and REFPROP. The predictability values of the models were validated by comparing the estimated results with the experiment data for the $CO_2+CH_4$ and $CO_2+N_2$ under high-density conditions. The Chung model showed 2.41%, which is the lowest mean deviation of the prediction among the model. Based on the Chung model, the mixture mole fractions were changed from 0.9, 0.95, and 0.97, the mixture pressure was ranged from 80 bar to 120 bar by 10 bar, and the mixture temperature was varied from 310 K to 400 K by 10 K to observe the effects of the parameters on the mixture viscosity. Considering the high mole fraction of the $CO_2$ in the mixture, a significant variation of the mixture viscosity was observed close to the pseudo-critical temperature, and the viscosity for the $CO_2+H_2S$ mixture shows the highest values compared with those of the $CO_2+CH_4$ and $CO_2+N_2$.

• 한국대기환경학회지
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• 제31권4호
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• pp.385-395
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• 2015

This study evaluated indoor environmental characteristics in an office room equipped both with ventilation window system and central cooling system. Fresh air is supplied only by the central cooling system whereas indoor air is discharged outside through both ceiling diffuser and a ventilation window system. Numerical study is conducted by changing the volumetric flow rates of exhaust ports of each system. For estimating the performance of this coupled system, $CO_2$ concentration and Predicted Mean Vote (PMV) were calculated using Computational Fluid Dynamics (CFD) simulation. The more the ceiling diffuser exhausts indoor air, the more the $CO_2$ concentration decreases. However, when the ventilation window system exhausts more indoor air, thermal comfort level gets improved in the office room with cooling system. Therefore, when the ventilation window system is operated, the coupled operation with central cooling system should be considered for enhancing indoor air quality and thermal comfort, together.

• KIEAE Journal
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• 제15권4호
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• pp.5-11
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• 2015

Purpose: Recently, renewable energy system has been widely used to reduce the energy consumption and CO2 emission of building. A photovoltaic/thermal(PVT) system is a kind of efficient energy uses, which is combined with photovoltaic module and solar thermal collector. PVT system removes heat from PV module by through thermal fluid to raise the performance efficiency of the PV system. However, though PVT system has the merit of the improved efficiency in theoretical approach, there have been few performance analysis for PVT system using the dynamic energy simulation. In this study, in order to establish the optimum design method of this system, simulation was conducted by using individual system modules. Method: For the dynamic simulation, TRNSYS17 was used and local weather data was utilized. Furthermore, the system performance in various installation condition was calculated by case studies. Result: As a result, the amount of electric generation and heat production in each case was found by the simulation. The gap of system performance was also evident according to the installation condition.