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산업용 전기집진기 내 유동 균일성에 대한입구 디퓨저 확장각의 영향
권현구,박석환,조형희,박기서 대한설비공학회 2006 설비공학 논문집 Vol.18 No.4
Industrial electrostatic precipitators require a highly uniform velocity distribution in the collecting chamber. Increasing divergence angle of a diffuser makes a non-uniformity flow distribution characteristics on the diffuser exit. This paper provides CFD results of optimum positions and opening rates of perforated plates which were installed in the electrostatic precipitator. The considered divergence angels were 60 degree and 90 degree. In 90 degree diffuser, a blanking method was used.
큰 회전각을 가지는 터빈 블레이드 표면에서 나프탈렌승화법을 이용한 열(물질)전달계수 측정
권현구,이상우,박병규,Gwon, Hyeon-Gu,Lee, Sang-U,Park, Byeong-Gyu 대한기계학회 2002 大韓機械學會論文集B Vol.26 No.8
The heat (mass) transfer characteristics on the blade surface of a high-turning first-stage turbine rotor for power generation has been investigated by employing the naphthalene sublimation technique. A four-axis profile measurement system is developed successfully for the measurements of local sublimation depth on the curved surface In the leading edge region, there is a good agreement between the present heat (mass) transfer data and the previous result on a turbine blade with a moderate turning angle, but some discrepancies are found in the mid-chord heat (mass) transfer between the two results. The local heat (mass) transfer on the present suction surface is greatly enhanced due to an earlier boundary transition, compared with that on a turbine blade with a moderate turning angle, meanwhile there is only a slight change in the pressure-side heat (mass) transfer between the two different turbine rotors. In general, the heat (mass) transfer augmentation by the endwall vortices is found much higher on the suction surface than on the pressure surface.
끝틈새가 선회각이 큰 터빈 동익 익렬 후류영역에서의 3차원유동 및 압력손실에 미치는 영향
권현구,박진재,이상우 한국유체기계학회 2004 한국유체기계학회 논문집 Vol.7 No.5
The effect of tip clearance height on the three-dimensional flow and aerodynamic loss in the wake region of a high-turning turbine rotor cascade has been investigated with a miniature cone-type five-hole probe. Distributions of velocity magnitude, secondary velocity vectors, and total-pressure loss coefficient are presented for three tip gap-to-span ratios of h/s = 0.0, 0.5 and 1.0 percent. The result shows that with the increment of h/s, tip leakage vortex tends to be intensified and aerodynamic loss due to the leakage vortex is increased as well. In the case of h/s = 1.0 percent, aerodynamic loss in the tip-leakage flow region is found dominant in comparison with that in the passage vortex region. With increasing h/s, mass-averaged secondary loss coefficient has a greater portion in the mass-averaged total-pressure loss coefficient.
2차 유동 영역에서 꺽임각 변화에 따른 주름진 사각 덕트에서의 열/물질전달 및 유동 특성
권현구(Hyun Goo Kwon),황상동(Sang Dong Hwang),조형희(Hyung Hee Cho) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5
The present study investigates the two dimensional flow and heat/mass transfer characteristics of wavy duct with various corrugation angles. For the heat/mass transfer coefficients, a naphthalene sublimation technique is used. Numerical analysis and wall pressure measurement show detailed two dimensional flow features. The corrugation angles change from 145° to 100°. The operating Reynolds numbers based on the duct hydraulic diameter vary from 700 to 3,000. The duct aspect ratio maintains 7.3. On the pressure wall, strong flow mixing enhances heat/mass transfer coefficients at the front position. In addition, the rear side of pressure wall, the near of peak, is affected by the acceleration and the shedding of main flow. On the suction wall, however, flow separation and reattachment lead to the valley and the peak of heat/mass transfer coefficient. Also, highly increasing boundary layer at the suction wall affects the decrease of heat/masst transfer. As decreasing corrugation angles, the spanwise average Sherwood number increases and the peak or the valley positions of the local Sherwood number are varied.
주름진 덕트에서 딤플/돌출 형상이 열전달계수에 미치는 영향
권현구(Hyun Goo Kwon),황상동(Sang Dong Hwang),조형희(Hyung Hee Cho) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.11
Heat transfer and performance characteristics have been investigated for a rectangular wavy duct with dimple or protrusion arrays. The test duct was 15㎜ in height and 105㎜ wide. The print diameter of the dimple/protrusion wall was 12.99㎜ and the depth/height of the dimple/protrusion was 3.75㎜. Local heat transfer coefficients on the dimple/protrusion wall were measured using a transient TLC technique. The Reynolds number was varied from 3,000 to 10,000. For the wavy duct tested in this study, adverse static pressure characteristics occurred at turning region of the wavy duct due to secondary flows. For the wavy duct with protrusion array, higher heat transfer enhancement level of 7.4 times than smooth straight case in maximum was obtained at low Reynolds number due to the high heat transfer enhancement by vortex flows. Also, the protrusion array increased the performance level of 3.0 at low Reynolds number of 3,000.