• 에너지공학
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• 제25권4호
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• pp.152-158
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• 2016

연소기기에서 연소반응과정이 일어날 때 연소로 내 고온의 온도 분위기에서 공기 중의 산소와 질소가 반응하여 질소산화물이 발생하게 된다. 발생한 질소산화물을 저감하기 위하여 화력발전소나 폐기물 소각로는 촉매를 이용한 탈질설비를 설치하고 있는데 이에 따른 설치와 유지비용이 많이 소요된다. 연소기기에서 질소산화물을 저감하기 위한 여러 가지 방법 중에 배기가스 재순환 방법이 널리 쓰이고 있다. 본 연구에서는 배기가스 재순환 배관에 코안다 노즐을 사용하여 배기가스를 재순환하는 재순환 버너에 대하여 전산유체해석을 통해 연구를 수행하였으며 냉간 유동에서 배기가스 재순환 유동 특성을 살펴보았고 코안다 노즐의 공기 측 간격 변화와 공기 유량 변화에 따른 배기가스 재순환 유량 특성을 살펴보았다. 본 연구의 버너 형상은 배기가스 재순환 흡입구와 출구는 원통 버너의 중심을 향하지 않고 접선 방향으로 설치되어 있어서 버너 내부에서 선회 유동이 형성 되었으며 이에 따라 원통 내부의 중심부분에 역류가 일어나는 특성을 관찰하였다. 또한, 코안다 노즐의 공기 측 간격은 0.5mm일 때는 배기가스 재순환 유량이 공기량 보다 약 2.5배 이었고 1.0mm일 때는 약 1.5배로 나타났으며 같은 공기 측 간격에서 공기량을 증가하면 배기가스 재순환 유량은 약간 증가하는 것을 알 수 있었다.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2000년도 제20회 KOSCO SYMPOSIUM 논문집
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• pp.162-168
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• 2000

This paper conducted experimental study of turbulent diffusion flame, equipped with a unique double swirler combustor for gas fuel. The burner has two vane swirlers which are fitted to primary, secondary air channel. Temperature, and NOx emission concentrations are measured in combustion flame region and velocity in cold flow for various primary/secondary air ratio conditions. The results showed the characteristics of swirl flame and decreasing NOx concentrations with increasing primary/secondary air ratio.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2004년도 제28회 KOSCO SYMPOSIUM 논문집
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• pp.235-241
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• 2004

Computations were performed to investigate the effects of air staging on combustion in three stage heavy-oil fired combustion burner. The burner was designed for 3 MW. Different amounts of air are introduced into each 3 three stages by means of each dampers. The goal of the study is to understand combustion phenomena according to each air stage mass ratios through CFD. Air flow rates at three inlets are adjusted by dampers inside a burner. Here, injection conditions of liquid fuel are kept constant throughout all simulations. This assumption is made in order to limit the complexity of oil combustion though it may cause some disagreement. In case of cold flows, only longitudinal velocities arc considered, On the other hand, flow, temperature and NOx generations are taken into account for reactive flows. Simple parametric study was conducted by setting 1'st air stage mass ratio as a parameter. And an optimal operation condition was found. The computational study is based on k-e model, P-1 radiation model(WSGGM) and PDF, and is implemented on a commercial code, FLUENT.

• Journal of Biosystems Engineering
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• 제27권3호
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• pp.235-240
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• 2002

Performance of the heat pump with attaching an air heat exchanger was investigated in the heating condition when the air heat exchanger was worked in the ambient air temperature of -5 to 11$\^{C}$ and air flow rate of 542 to 747 ㎡/h. Performance tests for heating condition were conducted in an experimental room equipped with heat pump. The performance tests were performed in a ambient temperature of -4 ∼ 11$\^{C}$, and room temperature of 4∼22$\^{C}$ respectively. Measured data(temperature, capacity of heat transfer and consumption of electronic power) were analyzed to the efficiency of HEEVA(Heat Exchanger fur the Evaporator), overall heat transfer coefficient and COP of heat pump. The results of inlet temperature for evaporator increased that the temperature was 2 ∼6$\^{C}$, and inlet temperature for condenser decreased that the temperature was 3 ∼ 8$\^{C}$. The results of comparing efficiency of HEEVA for the ratio of heat exchange between hot air and cold air showed that efficiency were considered to 91% because of the ratio of 83∼98%. The results of comparing of COP for the heat pump increased that improvement COP was approximately 0.3∼7.5 than HEEVA had not been operated.

• Journal of Biosystems Engineering
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• 제8권2호
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• pp.49-61
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• 1983

U shape multitube heat exchanger was equipped in the flue to recover the exhaust heat from the boiler system. The fluids of the exhaust heat recovery equipment were the flue gas as the hot fluid, and the water as the cold fluid. The flow geometry of the fluids was cross flow - two pass, the hot fluid being mixed and the cold fluid unmixed. The results of the theoretical and the experimental analysis and the economic evaluation are summarized as follows. 1) The heat exchanger effectiveness and the temperature efficiency of the hot fluid were about 35% when the fuel consumption rate was 140 - 150 L/15min. The temperature efficiency for the cold fluid ranged from 3.0% to 4.5%. The insulation efficiency ranged from 85% to 98%, which was better than the KS air preheater insulation efficiency of 90%. 2) The relationship between the fuel consumption rate, F, and the outlet temperature, $T_{h2}$, of the flue gas from the heat exchanger was $T_{h2}$ = 0.927F + 110. In order to prevent the low temperature corrosion from the coagulation of $SO_3$, it is necessary to maintain the fuel consumption rate above 82 L/15min. 3) The ratio of the exhaust heat from the boiler system to the total energy consumption was about 14.5%. With the installation of the exhaust heat recovery equipment, the energy recovery ratio to the exhaust heat was about 25%. Accordingly, about 3.6% of the total fuel consumption was estimated to be saved. 4) Economic analysis indicated that the installation of the exhaust heat recovery equipment was feasible to save the energy, because the capital reocvery period was only 10 months when the fuel consumption rate was 80 L/15min. 4 months when it was 160 L/15min. 5) Based on the theoretical and the experimental analysis, it was estimated to save the energy of about 18 million Won per year, if four heat exchangers are installed in a factory. 6) A further study is recommended to identify the relationship among the flow rate of the exhaust gas, the size of the heat exchanger and the capacity of the air preheater. For a maximum heat recovery from the exhaust gas an automatic control system is required to control the flow rate of the cold fluid depending on the boiler load.

• 한국자동차공학회논문집
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• 제10권5호
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• pp.235-241
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• 2002

The process of energy separation in a low pressure vortex tube with air as a working medium is studied In detail. Experimental data of the temperature of the cold and hot air leaving the vortex tube are presented. The variation of the maximum wall temperature along the inner surface of the vortex tube and the temperature distribution in the vortex tube provides useful information about the location of the stagnation point of the flow field at the axis of the vortex tube. In this study Outer tube is used for the application of Diesel engine exhaust. The hot gas flow is fumed 180° and passes the outside of the vortex tube a second time heating it. From this geometric setup of a vortex tube the effects of energy separation and the prediction of the ignition of Diesel Soot is presented by experimental data.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2004년도 제28회 KOSCO SYMPOSIUM 논문집
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• pp.173-179
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• 2004

Combustion of refuse derived fuel(RDF) and refuse plastic fuel (RPF) was carried out in a lab-scale circulating fluidized bed. Experiment was investigated cold flow visualization. RDF was made by C & tech and RPF was made by KRS. The results include distribution of temperature in the combustion chamber, and concentrations of flue gas such as $O_2$, $CO_2$, CO, $NO_x$ and HCs Micro G.C(gas chromatograph) was employed to find out concentration of He Temperature distribution was different when RDF and RPF were burnt respectably. As air ratio became increased, $CO_2$, CO, and total of HCs emissions were decreased. According to the number of carbon atom of HCs, HC were classified as five kinds of HC.

• 설비공학논문집
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• 제8권3호
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• pp.338-350
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• 1996

A numerical analysis is carried out to study the two-dimensional steady state natural convection from vertical wires immersed in cold pure water. The surface of the wire is $0^{\circ}C$ unifrom temperature. Results of the analysis are presented for free stream temperature from $0^{\circ}C$ to $25^{\circ}C$ and the aspect ratio N from $5.26{\times}10^{-3}$ to $1.0{\times}10^{-3}$. The effects of the density extremum and aspect ratio on the flow pattern and the heat transfer characteristics are discussed As the aspect ratio N becomes larger, in the range of $1.0^{\circ}C{\leq}T_{\infty}{\leq}4.4^{\circ}C$ and $6{^{\circ}C}{\leq}T_{\infty}{\leq}17^{\circ}C$, the effect of Pr number on the heat transfer is shown to be more significant than the aspect ratio. Investigating into the effect of the density extremum on the heat transfer from wires, the new heat transfer correlations are suggested with the relation of average Nu mumber vs. modified Ra number. Here, the coefficient values C of correlations are presented as the function of density extremum parameter $R^*$. The effects of the density extremum parameter are also discussed.

• Journal of Advanced Marine Engineering and Technology
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• 제18권1호
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• pp.81-91
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• 1994

Combustion noise involved with chemical heat release and turbulent process in turbopropulsion systems, gasturbine, industrial furnaces and internal engines is indeed noisy. The experimental study reported in this paper is made to identify a dominant combustion noise in jet flames. Gaseous propane and kerosene fuel have been used with air as the oxidizer in a different jet combustion systems. Combustion and aerodynamic noise are studied through far field sound pressure measurements in an anechoic chamber. And also mean temperature and velocities and turbulent intensities of both isothermal and reacting flow fields were measured. It is shown that axial mean velocity of reacting flow fields is higher about 1 to 3m/sec than that of cold flow in a gaseous combustor. As the gaseous fuel flow rate increases, the acoustic power increases. But the sound pressure level for the spray flame decreases with increasing equivalence ratio. The influence of temperature in the combustion fields due to chemical heat release has been observed to be a dominant noise source in the spray flame. The spectra of combustion noise in gaseous propane and kerosene jet flame show a predominantly low frequency and a broadband nature as compared with the noise characteristics in an isothermal air jet.

• 한국초전도ㆍ저온공학회논문지
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• 제1권1호
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• pp.48-55
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• 1999

thermodynamic cycle analysis has been performed for the power generation systems to utilize the cold energy of liquefied natural gas (LNG). The power cycle used the air or water at room temperature as a heat source and the LNG at cryogenic temperature as a heat sink. Among manypossible configurations of the cycle. the open Rankine cycle. and the closed Brayton cycle, and the closed Rankine cycle are selected for the basic analysis because of their practical importance. The power output per unit mass of LNG has been analytically calculated for various design parameters such as the pressure ratio. the mass flow rate. the adiabatic efficiency. the heat exchanger effectiveness. or the working fluid. The optimal conditions for the parameters are presented to maximize the power output and the design considerations are discussed. It is concluded that the open Rankine cycle is the most recormmendable both in thermodynamic efficency and in practice.