• Journal of computational fluids engineering
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• v.11 no.4 s.35
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• pp.20-25
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• 2006

In the present study, flow characteristics inside a road tunnel are simulated for the ventilation flows due to jet fan system and flows induces by the traffic. Traffic ventilation is numerically simulated by multiple reference frame. From the results of steady state simulation of tunnel ventilation, it is found that the proper ventilation is achieved by the designed jet fan system along with ventilating flow induced by the traffic. A transient simulation is also performed for the case of vehicle fire in the tunnel reversing the direction of rotation of some fans. The results suggest that the heat and smoke can be controlled by the proper changing of fan operation mode. The present results can be used to design proper ventilation system and effective smoke control system as well.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.9
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• pp.751-761
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• 2003

We performed the numerical analysis on the airflow characteristics in the two type of cleanroom systems, which are the axial fan type (AFT) and the fan filter unit (FFU). A computational fluid dynamic model was applied to investigate and compare the nonuniformity, the deflection angle and the air ventilation effectiveness of the two designs of cleanrooms when dampers are adjusted and not adjusted. And the flow-resistance models of the various components were used in this simulation. We know that the airflow characteristics of the cleanrooms are largely affected by damper adjusting And we also find out that the FFU system is superior to the AFT system through the comparison of the cleanroom performance indices.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.1
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• pp.114-123
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• 2000

The flow structure around a rotating axial-fan was experimentally investigated using a phase averaging velocity field measurement technique. The fan blades were divided into 4 different phases, for which 500 velocity fields were acquired for each phase angle with a 2-frame PTV system. Velocity field measurements were also carried out at two planes parallel to the axis of rotation, with offsets toward the radial direction of the fan. For accurate synchronization of the PTV system with the phase of the axial fan, two synchronization circuits were employed with a photo-detector attached to the rotating shaft. The phase averaged velocity fields show periodic variations with respect to the blade phase. The periodic formation of vortices at the blade tip is also observed in vorticity contour plots. Locations of local maximum turbulence intensities in the axial and radial directions are found to be located in an alternating pattern. These experimental results can be used to validate numerical calculations and to understand the flow characteristics of an axial fan.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.7
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• pp.780-788
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• 2004

This paper reports the fluid flow and heat transfer around a module cooled by forced air flow generated by a piezoelectric(PZT) cooling fan. The fluids are locally accelerated by a flexible PZT fan which deflects inside a fluid transport system of comparatively simple structure mounted on a PCB in a parallel-plate channel(450${\times}$80${\times}$700㎣). Input voltages of 20-100V and a resonance frequency of 23㎐ were used to vibrate the cooling fan. Input power to the module was 4W. The fluid flow around the module was visualized by using PIV system. The temperature distributions around a heated module were visualized by using liquid crystal film(LCF). The cooling effect using a PZT fan was independent of the vent area ratios at the channel inlet and was similar to the forced convection cooling. We found that the flow type was Y-shape and the cooling effect was increased by the wake generated by a piezoelectric cooling fan.

• Journal of Power System Engineering
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• v.9 no.3
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• pp.33-38
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• 2005

The aerodynamic performance of a cross-flow fan is strongly influenced by the various design factors of a rear-guider and a stabilizer. The purpose of this paper is to investigate the effects of a rear-guider and a stabilizer on the aerodynamic performance of a cross-flow fan. The design factors considered in this paper are a rear-guider clearance, a stabilizer clearance, and a stabilizer setup angle, respectively. This experiment was carried out with a constant revolution number of 700 rpm in a cross-flow fan installed in the fan tester. The static pressure, flowrate, torque, and revolution number were measured in this paper. Also, the pressure coefficient and the efficiency were analysed according to the various assembly conditions using a stabilizer setup angle, a stabilizer clearance, and a rear-guider clearance in the indoor room air-conditioner.

• Journal of Power System Engineering
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• v.9 no.3
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• pp.50-57
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• 2005

A cross-flow fan is strongly influenced by the various design factors of a rear-guider and a stabilizer. The purpose of this paper is to investigate the effects of a rear-guider and a stabilizer on the surface pressure of a rear-guider in an indoor room air-conditioner using a cross-flow fan. The design factors considered in this paper are a rear-guider clearance, a stabilizer clearance, and a stabilizer setup angle, respectively. The operating condition of a cross-flow fan was controlled by changing the static pressure and flowrate using a fan tester. All surface pressures of a rear-guider are differently distributed according to the stabilizer setup angle, and show a zero value in the flow coefficient, ${\Phi}{\fallingdotseq}0.5$ only of a stabilizer setup angle, $45^{\circ}$. Especially, they show a big negative value in the expansion angle larger than $34^{\circ}$ regardless of a rear-guider clearance, a stabilizer clearance, and a stabilizer setup angle. On the other hand, surface pressures for various stabilizer cutoff clearances are better than those for various rear-guider clearances.

• Journal of Power System Engineering
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• v.13 no.4
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• pp.31-37
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• 2009

The purpose of this numerical study was to investigate performance characteristics for cooling tower axial fans with sweep. Performance data for the fans with various sweep angles were obtained in terms of the setting angle at a constant flow rate. Viscous flow calculations were carried out to obtain Performance data of the total pressure rise and hydraulic efficiency. A solution of the Ffowcs Williams-Hawkings equations was used to calculate the sound pressure level at three times fan diameter away from the fan. The calculated performance data well represented performance characteristics of the cooling tower axial fan. The total pressure rise and hydraulic efficiency at the same setting angle decreased with sweep angle. Sound pressure level slightly decreased for the fan with a sweep angle of 10 degree. No significant effect of the sweep geometry was found on the sound pressure level.

• Journal of ILASS-Korea
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• v.8 no.1
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• pp.1-8
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• 2003

The flow analysis of the axial fan of rotary burner was performed by SIMPLE(Semi Implicit Method for Pressure Linked Equations) algorithm and finite volume mothod performed in the case of 3-D, incompressible, turbulent flow. In this study, the coordinate transformation was adapted for the complex geometry of axial fan, and the standard $k-{\varepsilon}$ model and wall function method were used for analysis of turbulent flow. Multi-block grid system was used for flow field and divided into four domains such as the inlet, outlet, flow field of rotating vane, and tip clearance. Fan rotation was simulated by rotational motion using MRF(Multiple Rotating Reference Frame) in steady, incompressible state flow.

• 한국가시화정보학회:학술대회논문집
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• 2004.12a
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• pp.41-45
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• 2004

The dynamic particle image velocimetry (PIV) is consisted of a high frequency pulse laser, high speed cameras and a timing controller. The three velocity components of flow downstream of an axial flow fan for PC cooling system are measured using the dynamic PIV system. An Axial flow fan has seven blades of 72 mm in diameter. The rotating speed is 1800 rpm. The downstream flow is visualized by smoke particles of about $0.3-1\;{\mu}m$ in diameter. The three-dimensional instantaneous velocity fields are measured at three downstream planes. The swirl velocity component was diffused downstream and the change in time-mean vorticity distribution downstream was also discussed. The spatio-temporal change in axial velocity component with the blades passing is recognized by the instantaneous vector maps. And the dynamic behavior of vorticity moving with the rotating blades is discussed using the unsteady vorticity maps.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.861-864
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• 2006

냉장고에 적용된 BLDC Fan Motor에 있어서 공진소음의 원인에 대하여 연구하였다. 연구에 있어서 종래의 가진 방법을 적용하기 곤란한 구조를 가진 소형 Fan & Rotor System의 동 특성 실험에서 전자 가진법 및 Microphone을 이용한 고유진동수 계측방법을 사용하고 그 타당성을 보였으며 연구결과, Pan과 Rotor System의 비틀림 고유진동수와 Fan의 굽힘 고유진동수가 BLDC Motor의 Commutating Torque Ripple에 의한 가진 주파수와 일치하여 공진이 발생하는 것으로 분석 되었으며 이와 관련된 주요 인자를 분석하고 대안을 제시하였다.