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거친외벽면을 가진 동심환형관내에서 완전히 발달된 유동의 난류구조
안수환,Ahn, S.W. 대한설비공학회 1999 설비공학 논문집 Vol.11 No.1
For roughened annular pipes with diameter ratios of 0.26, 0.39, and 0.56 and with Reynolds numbers ranging 13,000 to 67,000, friction factor, autocorrelation coefficients, power spectral density functions, and integral length scales for each flow condition using X-type hot wire anemometry system are experimentally investigated. Distributions of these quantities show that the times which the streamwise autocorrelation coefficients become zero first increase with decreasing the radius ratios of concentric annuli and Reynolds numbers, however the power spectra density functions increase with increasing the radius ratios and Reynolds number.
파형관 튜브가 있는 순환유동층 원통다관형 열교환기 내의 유체유동
안수환,이병창,배성택 대한설비공학회 2003 설비공학 논문집 Vol.15 No.5
An experimental study was carried on the characteristics of fluid flow and heat transfer in a fluidized bed shell-and-tube type heat exchanger with corrugated tubes. Seven different solid particles having same volume were circulated in the tubes. The effects of various parameters such as water flow rates, particle geometries and materials, and geometries of corrugated tubes on relative velocities and drag coefficients were investigated. The present work showed that the drag force coefficients of particles in the corrugated tubes were usually lower than those in the smooth tubes, meanwhile the relative velocities between particles and water in the corrugated tubes were little higher than those in the smooth tubes except the glass.
안수환,배성택,김명호,이병창,이윤표 대한설비공학회 2004 설비공학 논문집 Vol.16 No.12
An experimental study was performed to investigate the characteristics of heat transfer in a vertical type fluidized bed shell-and-tube type heat exchanger with corrugated tube. Seven different solid particles having the same volume were circulated in the heat exchanger. The effects of various parameters such as water flow rates, particle geometries, materials, and corrugated tube geometries were investigated. The present work showed that the higher thermal capacities of materials and the geometries closer to the spherical one have higher heat transfer performances. In addition, heat transfer coefficients in the corrugated tubes were a little higher than those in the smooth tubes.
Heat Transfer Augmentation in a Divergent Duct with Angled Ribs
안수환,이명성 대한설비공학회 2017 International Journal Of Air-Conditioning and Refr Vol.25 No.1
Heat transfer characteristics in the rectangular divergent duct with parallel angled ribs are experimentally compared with the straight smooth circular duct. The ribs with four different parallel angles ( ¼ 30, 45, 60, and 90) are glued on the duct's two opposite walls as well as on the duct's one sided wall only, respectively. The 0.72-inclined walls are installed at the two opposite walls of the rectangular divergent duct. The test section of 1000mm long has the cross section of 100 『 75mm2 at inlet and 100 『 100mm2 at exit. The ribbed walls are manufactured with a rib height ðeÞ ¼ 10mm and the ratio of rib spacing (p) to height(e) ¼ 10. The main ¯ndings are summarized that the increase in the dimensionless Nusselt number for the flow attack angles can be seen in the order of 90, 30, 60, and 45 at the two opposite ribbed divergent wall ducts, in addition, the average Nusselt number in the divergent rectangular duct with two opposite ribbed walls is somewhat greater than in the ribbed straight cross-sectional rectangular duct.
돌출형 거칠기벽이 있는 동심환형관의 유동에 대한 마찰계수
안수환,Ahn, Soo Whan 대한기계학회 1999 大韓機械學會論文集B Vol.23 No.5
The combined effects of radius ratio and roughness pitch ratio on the turbulent fluid flow characteristics of the fully developed flow in the annullar tubes with rib-roughened core walls were determined for Reynolds number ranging from 12,000 to 66,000. To understand the underlying physical phenomena responsible for friction factor enhancement, measurements of velocity profiles and zero shear stress and maximum velocity positions were combined to propose the friction factor correlation. Friction factors were found to be a function of the roughness pitch ratio and radius ratio.