• 설비공학논문집
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• 제20권11호
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• pp.733-738
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• 2008

Due to environmental concerns $CO_2$ has been reintroduced as a potential candidate to replace HFCs in refrigeration systems. Oils are always required in a vapor-compression cycle, and thus it is necessary to precisely estimate the thermodynamic mixture properties of $CO_2$-lubricant oil. In the present study, the density and the viscosity of the mixture was calculated by the Redlich and Kwong type EoS and the modified Peng and Robinson type viscosity EoS, respectively. The viscosity model was based on the similarity between P-v-T and T-$\mu$-P relationships. The predicted results were compared with the experimental data of Pens ado et al. whose test conditions were 100$\sim$650 bar of pressure and 303 K$\sim$353 K of temperature with the $CO_2$-POEs mixtures under 92.2 wt.% and 83.3 wt.% of $CO_2$ concentration. The mean deviations of the mixture density were 7.93% and 8.32% for 92.2 wt.% and 83.3 wt.% of $CO_2$ concentration, respectively. Concerning the viscosity, the mean deviations were 4% and 10% for 92.2 wt.% and 83.3 wt.% of $CO_2$ concentration under the Pensado et al.'s test conditions.

• 한국환경농학회지
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• 제2권1호
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• pp.35-44
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• 1983

울산공업단지내(蔚山工業團地內)에 위치(位置)한 돗질산식생(植生)을 오염원(汚染源)에서부터의 거리에 따른 조사구별(調査區別) 환경요인(環境要因)과 식생상태(植生狀態)를 분석(分析)한 결과(結果)를 요약(要約)하면 다음과 같다. 1) 토양(土壤)의 전질소함양(全窒素含量), 유기물함량(有機物含量), $P_2O_5$의 함량(含量), CEC는 오염원(汚染源)에서 거리가 멀어질 수록 증가(增加)를 하며, Al함량(含量)은 감소(減少)를 한다. 2) 식생조사결과(植生調査結果) 방동사니, 실새풀, 도깨비바늘, 댕댕이덩굴, 바랭이, 여뀌, 곰솔, 돼지풀, 철쭉, 아카시나무등(等)이 내오염성(耐汚染性)이 강(强)한 식생(植生)이었다. 3) 대기오염(大氣汚染)의 피해(被害)가 심(甚)하지 않은 곳에서는 13종(種)의 식물(植物)이 출현(出現)하나, 오염(汚染)이 극심(極甚)한 조사국(調査局)에서는 7종(種)의 식물(植物)만이 존재(存在)한다. 4) 대기오염(大氣汚染)의 증가(增加)에 따라 개체수(個體數), 종다양도(種多樣度), 균재도(均在度), 류사도지수(類似度指數)가 감소(減少)한다. 5) 대기오염원(大氣汚染源)에서의 거리가 멀어질 수록 물질생산량(物質生産量)이 증가(增加)된다. 또한 돗질산지역(地域) 아카시나무림분(林分)은 현존량(現存量)은 4.41t/㏊, 년간물질생산량(年間物質生産量)은 $0.67ton/ha{\cdot}yr$이고, 오염(汚染)의 피해(被害)가 없는 대조구(對照區)에서의 현존량(現存量)은 39.47ton/㏊이고, 년간물질생산량(年間物質生産量)은 $7.73ton/ha{\cdot}yr$이다.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
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• pp.515-516
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• 2006

Internal and inlet flows of a cross-flow fan have been visualized using a particle image velocimetry(PIV) to analyze a relationship with a performance of a room air conditioner(RAC). A test model which has a geometric similarity with the real RAC has been manufactured for the experiment and the flow characteristics have been analyzed with various flow rates and inlet grill angles for the cross-flow fan. The experimental results using the PIV technique have been compared with the existing numerical results. Also, a location and movement of an eccentric vortex which can affect the performance and noise of the RAC has been investigated by the PIV with various flow rates and inlet grill angles.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.1897-1902
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• 2003

An 1/21.6 scaled experimental facility was prepared utilizing the results of a scaling analysis to simulate the APRI400 reactor and insulation system. The behaviors of the boiling-induced two-phase natural circulation flow in the insulation gap were observed, and the liquid mass flow rates driven by natural circulation loop were measured by varying the wall heat flux, upper exit slot area and configuration. And non-heating experiments have also been performed and discussed to certify the hydraulic similarity of the heating experiments by injecting air equivalent to the steam generated in the heating experimental condition.

• 한국유체기계학회 논문집
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• 제8권6호
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• pp.26-32
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• 2005

1.6 MW class supersonic partial admission impulse turbine has been designed and tested in Korea Aerospace Research Institute for the liquid rocket engine application. The test has been performed using a high pressure air source facility in KARI. For the turbine power absorption, a hydraulic dynamometer has been used. Appropriate similarity relations are used for the determination of test condition. Various settings of turbine pressure ratio and rotational speed are tested to investigate global turbine characteristics. From measured data, parameters related to the turbine design are derived and validated.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.627-632
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• 2002

The paper considers acoustic analysis of the shock absorbing muffler within a rotary compressor. The internal space of the compressor is modelled as a combination of cavities and pipes. A simple one-dimensional impedance approach is used fur the acoustic analysis in the low frequency range, with ignoring the effects of gas flow and temperature gradients that are closely related to power efficiency of the compressor. Using the similarity between the vibration isolator and the shock absorbing muffler, the source strength transmissibility is newly proposed as a performance measure of the muffler and its validity is supported by power analysis. Some Important muffler design rules obtained are; (1) a muffler cavity and its opening throat should be used as a pair, (2) a long thin throat is desirable for high frequency noise isolation, (3) a large muffler cavity should be used with care since it shortens the working frequency range of the muffler. The rules were applied to redesign a compressor muffler currently in use, and a significant improvement was achieved by simply attaching a throat to the outlet holes of the muffler.

• 한국농림기상학회:학술대회논문집
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• 한국농림기상학회 2001년도 춘계 학술발표논문집
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• pp.39-42
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• 2001

There is general agreement that the mean land-surface air temperature of the Earth has increased by about 0.6 over the past century (Vinnikov et al., 1990; Jones, 1994). However, IPCC concluded in 1996 that the observed warming was "broadly consistent with predictions of climate models, but it was also the same magnitude as natural climate variability".(omitted).(omitted)

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2004년도 유체기계 연구개발 발표회 논문집
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• pp.125-131
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• 2004

1.6 MW class supersonic partial admission impulse turbine has been designed and tested in Korea Aerospace Research Institute for the liquid rocket engine application. The test has been performed using a high pressure air source facility in KARI. For the turbine power absorption, a hydraulic dynamometer is used. Appropriate similarity relations are used for the determination of test condition. Various settings of turbine pressure ratio and rotational speed are tested to investigate global turbine characteristics. From measured data, Parameters related to the turbine design are derived and validated.

• 한국분무공학회지
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• 제5권3호
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• pp.37-44
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• 2000

High velocity, gas-assisted liquid drop trajectories were investigated under well-controlled experimental conditions at elevated gas densities and room temperature. A monodisperse stream of drops which are generated by a vibrating-orifice drop generator were injected into a transverse high velocity gas stream. The gas density and air jet velocity were adjusted independently to keep the Weber numbers constant. The Weber numbers studied were 72, 148, 270, 532. The range of experimental conditions included studied the three drop breakup regimes previously referred as bag, stretching/thinning and catastrophic breakup regimes. High-magnification photography and conventional spray field photographs were taken to study the microscopic breakup mechanisms and the drop trajectories in high velocity gas flow fields, respectively. The parent drop trajectories were affected by the gas density and the gas jet velocities and do not show similarity with respect to the either Weber or the Reynolds number, as expected.

• 대한기계학회논문집B
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• 제20권1호
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• pp.377-383
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• 1996

Interaction of flames in a lean-rich concentration field is studied numerically adopting a counterflow as a model problem. Detailed kinetic mechanism is adopted in analyzing the structure of various type of flames which can be found in lean-rich interaction. Flow field is simplified to quasi one-dimensional by using boundary layer approximation and similarity formulation. Triple flames are identified and its structure shows that a diffusion flame is located in the middle of two premixed flames. Such a diffusion flame is formed by $H_2$ and CO generated from the rich premixed flame and $O_2$ leaked from the lean premixed flame. The flame position can be identified either from the hydrogen production rate or the heat release rate. Transition from single diffusion flame to triple flame is observed as degree of premixing is increased.