• 대한기계학회논문집B
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• 제28권2호
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• pp.238-246
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• 2004

This paper reports an experimental study around a module about forced air flow by blower (35${\times}$35${\times}$6㎣) in a portable personal computer model(200${\times}$235${\times}$10㎣). Experimental report is to know three data to investigate thermal resistance, adiabatic wall temperature and visualized fluid flow around the module by combination of the moving number and the arrangement method of blower. The channel inlet flow velocity has been varied between 0.26, 0.52 and 0.78㎧, and input power ( $Q_{p}$) to the module is 4W. To investigate thermal resistance. the heated module is mounted on two boards(110${\times}$110${\times}$1.2㎣, k=20.73, 0.494W/ $m^{\circ}C$) in parallel-plate channel to forced air flow. The temperature distribution were visualized by heated module on acrylic board(k=0.262W/ $m^{\circ}C$) using liquid crystal film. Fluid flow around the module were visualized using particle image velocimetry system.

• International Journal of Aeronautical and Space Sciences
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• 제9권1호
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• pp.111-120
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• 2008

A particle image velocimetry (PIV) technique was employed to investigate the effects of blowing jet on the flow characteristics over stationary and pitch-oscillating airfoils. The Reynolds number was $7.84{\times}10^5$ based on the chord length. It was found that for stationary airfoil cases, continuous and pulsating blowing jets successfully reduced separated wake region at high angles of attack. A comparison study of two different types of jet blowing indicated that pulsating jet is more effective than continuous jet for flow separation control. Pulsating leading-edge blowing postpones flow separation and increased stall angle of attack by $2^{\circ}{\sim}3^{\circ}$. For pitch-oscillating airfoil cases, the PIV results showed that blowing jet efficiently delays the separation onset point during pitch-up stroke, whereas it does not prevent flow separation during pitch-down stroke, even at angles of attack smaller than static ones.

• 한국환경생태학회지
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• 제33권3호
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• pp.366-374
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• 2019

본 연구는 폭염 및 미세먼지 저감을 위한 계획요소인 바람길의 활용 가능성을 논의해보고자, 전주시를 대상으로 바람길의 특성을 분석하고, 바람길 활용을 위한 방안을 제안하는 것을 목적으로 한다. 이를 위해, 호남정맥에 위치하는 전주지역 일대의 찬공기 흐름 및 찬공기 층 높이 등 찬공기 특성을 분석하였고, 전주시의 주요한 바람길을 특정하였다. 또한, 이를 바탕으로 전주시 일대의 산림관리 및 도시계획 활용방안을 제안하였다. 찬공기 특성 분석을 위해 독일에서 개발된 모형인 KALM(Kaltluftabflussmodell)을 이용하여 야간 6시간 동안 생성되는 찬공기 흐름 및 찬공기층 높이를 파악하였다. 분석 결과, 시간이 경과함에 따라 전주시 외곽 북동쪽 및 동쪽에 위치한 산림에서 생성된 찬공기의 흐름이 뚜렷해지고, 계곡지역과 농경지 일대에서 찬공기층의 높이가 증가하였다. 특히, 전주시의 찬공기 흐름은 북동쪽과 동쪽에서 생성된 찬공기가 전주시 중심 시가지로 유입되어 남쪽으로 흘러나가는 형태를 가지고 있어, 이상적인 바람길의 구조를 보여주는 사례였다. 찬공기 분석 결과를 바탕으로, 찬공기 생성이 활발한 산림지역 일대를 '찬공기 보전지역'으로 지정하고, 원활한 찬공기 흐름을 위해 관리가 필요한 지역을 '찬공기 관리지역'으로 지정하여, 찬공기 흐름을 유지 및 확대할 수 있는 방안을 제안하였다. 본 연구의 결과는 전주시의 기후변화 적응 정책, 바람길숲 조성 사업 등 폭염과 미세먼지 해결을 위한 정책 수립과 연구의 기초자료로 활용될 수 있을 것으로 기대한다.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 동계학술발표대회 논문집
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• pp.541-545
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• 2008

Particulate matter (PM) is one of the major indoor air pollutants especially in the subway station in Korea. In order to remove PM in the subway station, several kinds of PM removal system such as roll-filter, auto-washable air filter, demister, and electrostatic precipitator re used in the air handling unit (AHU) of subway station. However, those systems are faced to operation and maintenance problems since the filter-regeneration unit consisting of electrical or water jet parts is malfunctioned due to the high load of particulates and the filter material needs periodic replacement. In this study, we surveyed the particle removal systems in order to develop the new system of particle removing can be adopted in the current AHU of subway station.

• 대한기계학회논문집
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• 제9권6호
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• pp.714-724
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• 1985

본 논문에서는 입자가 부상된 2상유동의 해석에서 여러유동조건의 유동을 공 통적으로 해석할 수 있고 또 유동의 난류구조를 규명할 수 있도록 하기 위해서 2-방정 식 난류모델을 적용하였고 또 지배방정식들 속에 나타나는 1유체와 2유체의 2차 상관 관계들을 모형화 할 때 Taweel and Landau의 스펙트럼 이론을 확장발전시켜 적용하였 다.

• 한국입자에어로졸학회지
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• 제11권2호
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• pp.47-55
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• 2015

This study compares the results of collection efficiency of difference gas temperature in cyclone dust collector. The previous researcher's experiment results were used to confirm the reliability of CFD(Computational Fluid Dynamics) model. Based on this verified CFD model, we extended the analysis on the cyclone dust collectors. In CFD study, we used RNG k-epsilon model for analysis of turbulence flow, fluid is air, the velocity at inlet is 10 m/s, the temperature of air is $20^{\circ}C$, $100^{\circ}C$, $200^{\circ}C$, $300^{\circ}C$, $600^{\circ}C$ and $1000^{\circ}C$. As the temperature decreases, the average velocity of outer vortex and collection efficiency is increased, showed the highest collection efficiency at $20^{\circ}C$. It can be inferred smooth flow in cyclone dust collector is difficult because air viscosity increases as temperature increases. The power required at $1000^{\circ}C$ is almost 18 times greater than that of $20^{\circ}C$ to get the similar collection efficiency.

• Journal of Advanced Marine Engineering and Technology
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• 제28권5호
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• pp.818-826
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• 2004

The spray-induced mixing characteristics and thermal decomposition of aqueous urea solution into ammonia have been studied to design optimum sizes and geometries of the mixing chamber in SCR(Selective Catalytic Reduction) system. The cold flow tests about the urea-injection nozzle were performed to clarify the parameters of spray mixing characteristics such as mean diameter and velocity of drops and spray width determined from the interactions between incoming air and injected drops. Discrete particle model in Fluent code was adopted to simulate spray-induced mixing process and the experimental results on the spray characteristics were used as input data of numerical calculations. The simulation results on the spray-induced mixing were verified by comparing the spray width extracted from the digital images with the simulated Particle tracks of injected drops. The single kinetic model was adopted to predict thermal decomposition of urea solution into ammonia and solved simultaneously along with the verified spray model. The hot air generator was designed to match the flow rate and temperature of the exhaust gas of the real engines The measured ammonia productions in the hot air generator were compared with the numerical predictions and the comparison results showed good agreements. Finally, we concluded that the design capabilities for sizing optimum mixing chamber were established.

• Journal of Mechanical Science and Technology
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• 제15권3호
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• pp.281-290
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• 2001

Particle contamination has been an ongoing problem affecting the reliability of the magnetic hard disk drives. Especially the recent use of MR head requires much tighter control of particle contamination due to thermal asperity (TA) phenomenon. In this study, the effects of slider air bearing surface design of TA reduction capability were investigated by manufacturing two types of sliders. Numerical methods were used to simulate the motion of particles in the head/media interface. Experiments were conducted to verify the results predicted by the numerical simulation. Drives were built and exposed to particle contamination using a particle injection chamber, which turned out to be a very simple and reliable particle generation method over conventional aerosol technique. Then the number of TA generated in the drives was recorded and compared. Also the contacts between slider and particles were investigated by acoustic emission study. It was found that a new ABS design, which has aerodynamic U-shaped rail and central flow passage, was beneficial in reducing the particle contamination on the slider.

• 대한기계학회논문집B
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• 제23권1호
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• pp.92-103
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• 1999

The fuel spray behavior in the intake port of an electronic control port irijection gasoline engine has a strong influence on engine performance, exhaust emission and fuel consumption. Thus, in this study, fuel spray behavior and flow characteristics of the air assist gasoline spray injected into a suction flow in a simulated rectangular intake port have boon investigated. Macro-behavior of spray characteristics was investigated by means of visualization and the measurements of SMD and velocity were made by PDPA. For analysis the flow field with droplets size, droplets are classified five droplets size groups. As a result, the normal distance of suction flow increasing, the relatively large droplets distribution and SMD increase because small droplets easily follow suction flow. Near impinging wail, after impinging against the wall, secondary atomized small droplets of D < $30{\mu}m$ bound from the wall. And the increasement of suction flow progress to the large droplets of D > $100{\mu}m$ distribution. Therefore, SMD are apparently increased near impinging wall, Z/d = 9.0.

• 한국분무공학회지
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• 제10권3호
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• pp.38-44
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• 2005

The direct injection into the cylinders has been regarded as a way of the reduction in fuel consumption and pollutant emissions. The spray produced from the injector of DIS(Direct Injection Spark Ignition) engine is of paramount importance in DISI engines. Fan-spray injector as well as swirl-spray injector was developed and utilized to the DISI engines. The interaction between air flow and fuel spray was investigated in a steady flow system embodied in a wind tunnel to simulate the variety of flow inside the cylinder of the DISI engineer. The direct Mie scattered images presented the macroscopic view of the liquid spray fields interacted with crossflow. Particle sizes of fuel droplets were measured with phase Doppler anemometer(PDA) system. A faster cross-flow field made SMD larger and $D_{10}$ smaller. The experiments show the interaction of air flow field and the fuel spray field of fan-spray. The results can be utilized to construct the data-base for the spray and fuel-air mixing mechanism as a function of the flow characteristics.