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류구영,원정호,조형희,Ryu, Goo-Young,Won, Chung-Ho,Cho, Hyung-Hee 대한기계학회 2000 大韓機械學會論文集B Vol.24 No.4
Local heat transfer characteristics inside a hard disk driver(HDD) are investigated in this study. The investigation is considered between disks co-rotating in a cylindrical enclosure. The gap spacing, rotating speed and head-arm positions are mainly considered to understand the flow and heat transfer in the co-rotating disks. The naphthalene sublimation technique is used to determine local heat/mass transfer coefficients on the rotating disk. Flow patterns inside the co-rotating disks are investigated using a Laser Doppler Anemometer (LDA) and also analyzed numerically. The results show that the heat transfer coefficients on the disk changed little with the gap spacing between disks. Heat transfer rates in the outer region increases with increasing rotating Renolds number, but the values normalized by that on a free rotating disk give a similar pattern for the tested cases. The head-arm inserted between the rotating disks destroys the inner region resulting in enhancement of heat transfer in that region.
슈라우드로 차폐되어진 단일회전디스크 표면의 열전달 특성
류구영,원정호,조형희,Ryu, Goo-Young,Won, Chung-Ho,Cho, Hyung-Hee 대한기계학회 2000 大韓機械學會論文集B Vol.24 No.8
The present study investigates the local heat/mass transfer characteristics on a rotating disk which is the top disk covered with a shroud in HDD. The naphthalene sublimation technique is employed to determine the local heat/mass transfer coefficients on the rotating disk. Flow field measurements using Laser Doppler Anemometry (LDA) and numerical calculations are performed to analyze the flow patterns induced by the disk rotation. HDD has been developed for compactness and speedy data access, thus the rotating velocity of the disk is increased and the height of a hub is decreased. The experiments are conducted for the various hub heights of 5, 10 and 15 mm, for the rotating Reynolds numbers of $5.5{\times}10^4$ to $1.1{\times}10^5$ and for the effects of the presence of a read/write head arm. The results show that the heat transfer on the rotating disk is enhanced considerably for the decrease of the hub height and for the increase of the rotating Reynolds number. The head arm inserted in the cavity decreases the heat transfer despite the enhancement of tangential RMS velocity because of the deficit of the momentum in the flow field.
하헌우,류구영,남임우,정봉철 대한기계설비건설협회 2000 기계설비 Vol.124 No.-
The enhancement of living standard is accompanied with rising both demand of air-conditioner and construction of large building. Consequently the additional request of electric power tends to be increased abruptly. But construction of power plant to suppl
노즐분공내 유체충돌이 있는 디젤노즐의 유동 및 분무특성 연구
하성업,김흥열,구자예,류구영,Ha, Seong-Eop,Kim, Heung-Yeol,Gu, Ja-Ye,Ryu, Gu-Yeong 대한기계학회 1997 大韓機械學會論文集B Vol.21 No.12
The nozzle length to diameter ratio of real diesel nozzles is about 2-8 which is not long enough for a fully developed and stabilized flow. The characteristics of the flow such as turbulence at the nozzle exit which affect the development of the spray can be enhanced by impinging the flow inside nozzle. The flow details inside the impinging nozzles have been investigated both experimentally and numerically. The mean velocities, the fluctuating velocities, and discharge coefficients in the impinging inlet nozzles, round inlet nozzle, and sharp inlet nozzle were obtained at various Reynolds number. The developing feature of the external spray were photographed by still camera and the droplet sizes and velocities were also measured by laser Doppler technique. The spray angle was greater and the droplet sizes near the spray axis were smaller with the impinging flow inside nozzle.