• KSTLE International Journal
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• 제9권1_2호
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• pp.1-6
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• 2008

In this study is performed a complex lubrication analysis of a herringbone groove air journal bearing, which shows a big potential as an oilless bearing for a color wheel used as an original color source for a large DLP projection television and rotating at a rated-speed of 10,800 rpm. The Galerkin FE and perturbation methods are used for a lubrication analysis of the bearing. The effects of groove number, angle and depth and bearing clearance on the dynamic stability of the bearing are investigated in terms of the critical mass, and its equilibrium positions, stiffness and damping coefficients are calculated at various rotating speeds. Results have shown that the designed herringbone groove air journal bearing is quite suitable as a support bearing for the considered high-speed color wheel in terms of the complex lubrication performances of the bearing itself.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 추계학술대회논문집
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• pp.459-464
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• 2003

The Roordynamic feasibility of Micro Power System supported by air foil bearings is investigated. The Micro Power System is new portable power source based on brayton cycle, which consists of compressor, turbine, generator, and combustion chamber. In this paper, the analysis of Rotordynamic characteristics of Micro Power System is performed based upon the bearing equilibrium position, Campbell diagram and stability. As a result, it is demonstrated that the air foil bearings could be adopted well to the Micro Power System. However, for more stable operation at target running speed, the damping characteristics of air foil bearing should be enhanced.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2005년도 총회 및 춘계학술발표회
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• pp.232-236
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• 2005

In-situ Air Sparging (IAS, AS) is a groundwater remediation technique, in which organic contaminants are volatilized into air as it rises from saturated to vadose soil zone. The purpose of this study was to investigate the effect of environmental conditions on the degradation of VOCs (Volatile Organic Compounds) and $CO_2$ in the unsaturated zone and TPH (Total Petroleum Hydrocarbons) in saturated zone of sandy loam. In the laboratory, diesel (10,000 mg TPH/kg)-contaminated saturated soil. After heating the soil for 36 days, the equilibrium temperature of soil reached to $34.9{\pm}2.7^{\circ}C$ and TPH concentration was reduced to 78.9% of the initial value, Volatilization loss of VOCs in TPH was about 2%, The reduction gradient of $CO_2$ concentration was 0.018/day in air space and 0.0007/day in unsaturated zone.

• 한국대기환경학회지
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• 제17권5호
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• pp.415-424
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• 2001

The concentrations of PCBs (polychlorinated biphenyls) in air and plants (MOrus allba, Allum turberosum) were measured every other week at Hankyong University located in Ansung, Kyoung-ki province, Korea from July to November in 1999. Total concentrations of PCBs in air ranged from 19.8 to 71.9 pg/ $m^3$. It was observed in air that the concentrations of tai-chlorinated biphenyls(CBs) were higher than those of other PCB homologs probably due to their higher vapor pressure. Total concentrations of PCBs in plants ranged from 24.5 to 1,287 pg/g dry weight for Morus allba and 26.5 to 337 pg/g dry weight for Allum turberosum. A positive linear correlation was observed between log plant-air partition coefficients ( $m^3$air/g plant dry weight-defined here as the scavenging coefficient[S.C]) and log octanol-air partition coefficients ( $K_{oa}$ ) for each plant. In this study, slope of log S.C and log $K_{oa}$ for Morus allba, Allum turberosum were 1.07 ($R^2$= 0.83, p<0.01), 0.84 ($R^2$=0.53, p<0.05), respectively. This means that these plants may approach to equilibrium for air-plant partitioning.

• 설비공학논문집
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• 제15권11호
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• pp.943-956
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• 2003

A numerical program has been developed for the simulation of automotive engine cooling system. The program determines the mass flow rate of engine coolant circulating the engine cooling system and radiator cooling air when the engine speed is adopted by appropriate empirical correlation. The program used the method of thermal balance at individual element through the model for radiator component in radiator analysis. This study has developed the program that predicts the coolant mass flow rate, inlet and outlet temperatures of each component in the engine cooling system (engine, transmission, radiator and oil cooler) in its state of thermal equilibrium. This study also combined the individual programs and united into the total performance analysis program of the engine cooling system operating at a constant vehicle speed. An air conditioner system is also included in this engine cooling system so that the condenser of the air conditioner faces the radiator. The effect of air conditioner to the cooling performance, e.g., radiator inlet temperature, of the radiator and engine system was examined. This study could make standards of design of radiator capacity using heat rejection with respect to the mass flow rate of cooling air. This study is intended to predict the performance of each component at design step or to simulate the system when specification of the component is modified, and to analyze the performance of the total vehicle engine cooling system.

• 한국연초학회지
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• 제14권1호
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• pp.48-56
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• 1992

This studies were carried out to investigate the effects of leaf loading quantity and circulating air volume during bulk curing on the variation of physical and chemical characteristics in flue-cured tobacco. The results are as follows : 1. The content of sugar in cured leaves was decreased with more circulating air volume and leaf loading quantity at bulk curing. 2. Total nitrogen and protein nitrogen were decreased with less circulating air volume and more leaf loading quantity, while amino nitrogen was increased. 3. The contents of linolenic acid and linoleic acid were increased with more leaf loading quantity and oxalic acid and citric acid had a tendency of being increased in case of high circulating air volume. 4. In general, major aromatic compounds were increased through flue-curing. Relatively high content of solanone in case of lower air volume and less leaf loading were observed, while megastig matrienone was increased when leaf loading was small. 5. The more circulation air volume with leaf loading quantity caused lowering equilibrium moisture content and higher shatter index, which resulted in poor quality of cured leaves based on quality index, nitrogen number, taste index phillips index, and sugar-nicotine ratio.

• 한국콘텐츠학회논문지
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• 제9권10호
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• pp.444-450
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• 2009

본 연구는 폐 활성슬러지를 이용하여 $Pb^2+$와 $Cr^2+$의 생체흡착속도 및 평형을 도출하였으며, 가압부상법이 이용하여 A/S 비에 따른 폐슬러지의 분리효율을 비교하였다. 흡착량 및 접촉시간은 흡착평형과 동역학 모델식을 이용하여 모사하였다. 폐 활성슬러지상에서 $Pb^2+$와 $Cr^2+$의 흡착평형은 Langmuir와 Redlich-Peterson식에 의해 잘 예측될 수 있었다. 흡착속도는 유사 1차 반응식보다는 유사 2차 반응식에 의해 더 잘 예측되었다. 가압부상법을 이용한 폐 활성슬러지의 분리효율은 90%이상 유지하는 것이 가능하였다.

• 대한기계학회논문집B
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• 제26권7호
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• pp.951-958
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• 2002

Rapid expansion of a moist air or a stream through a supersonic nozzle often leads to non-equilibrium condensation shock wave, causing a considerable energy loss in flow field. Depending on amount of latent heat released due to non-equilibrium condensation, the flow is highly unstable or a periodical oscillation accompanying the condensation shock wave in the nozzle. The unsteadiness of the condensation shock wave is always associated with several kinds of instabilities as well as noise and vibration of flow devices. In the current study, a passive control technique using a porous wall with a plenum cavity underneath is applied for the purpose of alleviation of the condensation shock oscillations in a transonic nozzle. A droplet growth equation is coupled with two-dimensional Navier-Stokes equation system. Computations are carried out using a third-order MUSCL type TVD finite-difference scheme with a second-order fractional time step. An experiment using an indraft wind tunnel is made to validate the present computational results. The results show that the oscillations of the condensation shock wave are completely suppressed by the current passive control method.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2005년도 동계학술발표대회 논문집
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• pp.380-385
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• 2005

An experimental apparatus was constructed to obtain vapor-liquid equilibrium data for $CO_2$/oil mixtures using mass analysis method with sample cylinder. Lubricants employed were POE(Polyol Ester) oil and PAG(Poly Alkylene Glycol) oil. The phase equilibria of $CO_2$/oil mixtures formed in high pressure equilibrium cell are observed through sight glasses at the opposite ends. Data were measured over the temperature range from -10 to $10^{\circ}C$ with $5^{\circ}C$ intervals under pressures up to 14 MPa. Mole fractions were calculated for $CO_2$/oil and $CO_2$/PAAG, respectively and were compared with each other.

• 드라이브 ㆍ 컨트롤
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• 제15권4호
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• pp.11-16
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• 2018

Pilot operated control valve for $CO_2$ refrigerant is a valve that can perform various functions according to the user's intention by replacing pilot units, widely used for flow rate, pressure, and temperature control of refrigeration and air conditioning systems. In addition, $CO_2$ refrigerant, that requires high pressure and low critical temperature, can be installed and used in all positions of the refrigeration system, regardless of high or low pressure. In this paper, response characteristics are modeled and analyzed based on behavior of the main piston of the pilot-operated control valve. Although various factors influence operation of the main piston, this paper analyzes the effect of equilibrium pressure depending on valve installation position and application, and inlet and outlet orifice size of the load pressure feedback chamber to determine feedback characteristics of the main piston. As a result, it was possible to quantitatively analyze the effect of change in equilibrium and load pressure feedback chamber flow path size on the change in main piston dynamic and static characteristics.