• 한국자동차공학회논문집
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• 제16권2호
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• pp.150-157
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• 2008

The main objective of this paper is to investigate the performance characteristics of a $CO_2$ air conditioning system for fuel cell electric vehicles (FCEV). The present air conditioning system for FCEV uses the electrically driven compressor and electrically controlled expansion valve for $CO_2$ as a working fluid. The experimental work has been done with various operating conditions, which are quite matching the actual vehicle's driving conditions such as different compressor speed and high pressure to identify the characteristics of the system. Experimental results show that the cooling capacity and coefficient of performance (COP) were up to 6.3kW and 2.5, respectively. This paper also deals with the development of optimum high pressure control algorithm for the transcritical $CO_2$ cycle to achieve the maximum COP.

• 한국태양에너지학회 논문집
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• 제32권1호
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• pp.32-39
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• 2012

New and renewable energy systems(solar thermal system, photovoltaic system, geothermal system, wind power system) are environmentally friendly technologies and these in South Korea are very important measures to reduce greenhouse-gas(GHG) and to push ahead with Green Growth. The purpose of this paper is to analyze GHG mitigation potential by distribution of solar thermal system in housing sector with bottom-up model called 'Long-range Energy Alternative Planning system'. Business as usual(BAU) was based on energy consumption characteristic with the trend of social-economic prospects and the volume of housing. The total amount of GHG emission of BAU was expected to continuous increase from 66.0 million-ton $CO_{2e}$ in 2007 to 73.1 million-ton $CO_{2e}$ in 2030 because of the increase of energy consumption in housing. The alternative scenario, distribution of solar thermal system in housing sector had GHG mitigation potential 1.54 million-ton $CO_{2e}$ in 2030. The results of this study showed that new and renewable energy systems made a contribution of reducing the use of fossil fuel and the emission of greenhouse-gas in building.

• 한국자동차공학회논문집
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• 제17권1호
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• pp.146-153
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• 2009

The performance characteristics of heat exchangers which consist of a gas cooler, an evaporator and an internal heat exchanger have been investigated at various operating conditions of $CO_2$ air conditioning system by experiments. The heat exchangers were designed for use in the vehicle $CO_2$ air conditioning system, when considering the characteristics of heat transfer and high pressure as $CO_2$ refrigerant. This paper studied the performance of heat exchangers at various compressor speeds and expansion valve openings, and quantified the heat transfer rates and pressure drops. Heat transfer rates at the gas cooler and the evaporator were 6.9 kW and 5.2 kW, respectively, when the compressor speed was 4000 rpm and refrigerant vapor quality at the evaporator outlet was 0.98. Therefore, this paper carried out that the heat exchangers were analyzed to achieve superior performance for the vehicle transcritical $CO_2$ cycle.

• 한국자동차공학회논문집
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• 제14권4호
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• pp.1-11
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• 2006

The aim in this study is to develop the combined EGR system with a non-thermal plasma reactor for reducing exhaust emissions and improving fuel economy in turbo intercooler ECU common-rail diesel engines. In this study, the characteristics of soot, CO and $CO_2$ emissions under four kinds of engine loads are experimentally investigated by using a four-cycle, four-cylinder, direct injection type, water-cooled turbo intercooler ECU common-rail diesel engine with a combined plasma exhaust gas recirculation(EGR) system operating at three kinds of engine speeds. The EGR and non-thermal plasma reactor system are used to reduce $NO_x$ emissions, and the non-thermal plasma reactor and turbo intercooler system are used to reduce soot and THC emissions. The plasma system is a flat-to-flat type reactor operated by a plasma power supply. The fuel is sprayed by pilot and main injections at the variable injection timing between BTDC $15^{\circ}$ and ATDC $1^{\circ}$ according to experimental conditions. It is found that soot emissions with increasing EGR rate are increased, but are decreased as the applied electrical voltage of the non-thermal plasma reactor is elevated at the same engine speed and load. Results also show that CO and $CO_2$ emissions are increased as EGR rate is elevated, and CO emissions are increased, but $CO_2$ emissions are decreased as the applied electrical voltage of the non-thermal plasma reactor is elevated at the same engine speed and load.

• 조명전기설비학회논문지
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• 제22권4호
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• pp.13-18
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• 2008

1997년 교토 기후협약이 체결되었고, 세계는 지금 지구온난화 문제로 $CO_2$ 전쟁을 치르고 있다. 우리나라도 2013년부터 기후협약 규제가 거의 확실시 되고 있다. 화석연료의 연소로 대부분의 전력을 생산하는 발전산업은 우리나라 $CO_2$ 대기배출량의 20[%] 이상을 차지하고 있다. 발전소의 화석연료의 소모와 이에 따른 $CO_2$ 대기배출 규제는 갈수록 엄격해 질 전망이며 전력생산단가에 크게 영향을 끼칠 것이다. 본 논문은 화력발전소의 입출력 특성계수를 이용하여 발전출력에 대한 $CO_2$ 대기배출비용 함수를 유도하는 방법과 이를 전력계통의 운용에 반영하는 방안을 제시한다. 모형계통의 시뮬레이션을 통하여 $CO_2$ 배출량과 $CO_2$ 대기배출비용을 감안한 전력 계통 최적운전 연산 사례를 도시하였다.

• 한국재료학회지
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• 제15권6호
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• pp.375-381
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• 2005

High temperature oxidation behavior of thermal barrier coating (TBC) system (IN738 substrate + NiCoCrAlY or NiAl bond coat with or without Pt + yttria stabilized zirconia) prepared by air plasma spray (APS) process has been studied in order to understand the effect of Pt addition to bond coat on the stability of TBC system. Specimens were oxidized in thermal cycling and isothermal oxidation test at $1100^{\circ}C$. The Pt addition in TBC system with NiCoCrAlY bond coat showed a longer life time compared to that without addition of Pt. Pt addition to TBC system is believed to help the formation of more stable thermally grown oxide, $Al_2O_3$, at the TBC/bond coat interface, leading to a longer lifetime of TBC system.

• 한국분말재료학회지
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• 제26권2호
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• pp.112-118
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• 2019

Infiltration is a popular technique used to produce valve seat rings and guides to create dense parts. In order to develop valve seat material with a good thermal conductivity and thermal expansion coefficient, Cu-infiltrated properties of sintered Fe-Co-M(M=Mo,Cr) alloy systems are studied. It is shown that the copper network that forms inside the steel alloy skeleton during infiltration enhances the thermal conductivity and thermal expansion coefficient of the steel alloy composite. The hard phase of the CoMoCr and the network precipitated FeCrC phase are distributed homogeneously as the infiltrated Cu phase increases. The increase in hardness of the alloy composite due to the increase of the Co, Ni, Cr, and Cu contents in Fe matrix by the infiltrated Cu amount increases. Using infiltration, the thermal conductivity and thermal expansion coefficient were increased to 29.5 W/mK and $15.9um/m^{\circ}C$, respectively, for tempered alloy composite.

• 설비공학논문집
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• 제14권7호
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• pp.531-542
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• 2002

Transcritical$CO_2$ systems are under consideration for use as residential/mobile air conditioners. In these systems, an internal heat exchanger is usually adopted to improve both capacity and/or COP of the $CO_2$ system in lower operating pressure range of gas cooler. A program has been developed to analyse the performance of internal heat exchangers using the section-by-section method. The internal heat exchanger of coaxial configuration is first analyzed and fairly good agreements with the data are obtained, And then the internal heat exchanger of multiple circular coil configuration has been investigated. The results obtained from the parametric study provide the guidelines for the initial design and manufacturing concepts of the internal heat exchanger in transcritical $CO_2$ system. Further studies are necessary to develop the heat transfer correlations of carbon dioxide in the tubes to obtain more accurate results.

• 한국자동차공학회논문집
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• 제16권3호
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• pp.87-93
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• 2008

The $CO_2$ air conditioning system installed in fuel cell vehicles could be used either for stack cooling or for cabin cooling, and thus was used for the stack cooling when additional stack heat release was required over a fixed radiator capacity for high power generation. This study investigated the performance of the stack cooling system using $CO_2$ air conditioner at various operating conditions. Also, the heat releasing effectiveness and mutual interference were analyzed for the stack cooling system using an air conditioner and compared with the conventional radiator cooling system with/without cabin cooling. The heat release of the stack cooling system with the aid of $CO_2$ air conditioner increased up to 36% more than that of the conventional radiator cooling system with cabin cooling. Furthermore, the heat release of the stack cooling system using $CO_2$ air conditioner increased more by 7% than that of the conventional radiator cooling system without cabin cooling.

• 대한환경공학회지
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• 제27권7호
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• pp.704-711
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• 2005

본 연구에서는 국내 전력공급을 양분하는 원자력발전시스템과 화력발전시스템사이에 대하여 LCA를 수행하여 환경영향을 비교 평가하였다. 연구범위로서 두 발전시스템의 건설, 운영, 해체 및 폐기처분단계를 포함하였으며, 환경영향은 Life Cycle Impact Assessment(LCIA) 방법론을 이용하여 단일 환경영향으로 $CO_2$ 배출량을 평가하고, 영향 범주를 확대하여 8대 지구 환경영향 및 방사능 영향을 포함한 환경영향에 대하여 평가를 수행하였다. 평가 결과, 원자력발전시스템이 화력발전시스템보다 $CO_2$ 배출량 평가에서는 10,000배, 8대 환경영향범주에 대한 평가에서는 90배, 방사능을 고려한 환경영향 평가결과에서는 40배의 환경적 우위를 나타내어 환경영향범주 확대와 방사능 포함여부에 따라 원자력발전의 친환경성이 크게 달라짐을 알 수 있었다.