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RISS 인기검색어
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- 저자 : 원정호(Chung-Ho Won) (검색결과 7 건)
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$180^{\circ}$ 곡관부를 가지는 회전 덕트에서의 열/물질전달 특성
원정호,이세영,조형희,Won, Chung-Ho,Lee, Sei-Young,Cho, Hyung-Hee 대한기계학회 2001 大韓機械學會論文集B Vol.25 No.3
The present study investigates convective heat/mass transfer and flow characteristics inside a rotating two-pass rectangular duct. A naphthalene sublimation technique is employed to determine the detailed local heat transfer coefficients using the heat and mass transfer analogy. The objective of this study is to determine the effects of turning geometry with rotation for 0.0$\leq$Ro$\leq$0.24. The results reveal that the sharp-turn corner has the larger pressure drop and lower heat transfer in the post-turn region than those of the round-turn corner. The strong secondary flow enhances heat transfer for the round-turn corner. Coriolis force induced by the rotation pushes the high momentum core flow toward the trailing wall in the first passage with radially outward flow and toward the leading wall in the second passage with radially inward flow. Consequently, the high heat transfer rates are generated on the trailing surface and the leading surface in the first and second passage, respectively. However, the strong secondary flow due to the turning dominates the flow pattern in the second passage, thus the heat transfer differences between the leading and trailing surfaces are small with the rotation.
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구속된 단일 회전원판과 동시 회전원판 내부의 유동 특성
원정호,류규영,조형희,Won, Chung Ho,Ryu, Goo Young,Cho, Hyung Hee 대한기계학회 1999 大韓機械學會論文集B Vol.23 No.9
The present study investigates flow characteristics in a cavity with one rotating disk and co-rotating disks for application to HDD. The experiments are conducted for rotating Reynolds numbers of $5.5{\times}104$ to $1.10{\times}105$ and for gap ratios of 0.059 to 0.175 in a single rotating and 0.047 to 0.094 in co-rotating disk. Time-resolved velocity components and turbulence intensity on the rotating disks are obtained by using LDA measurements. Detailed Knowledge of the flow characteristics is essential to analyze flow vibration and heat transfer and to design head-arm assembly and hub height in HDD. The results indicate that the velocity field in HDD is changed largely by the rotating Reynolds numbers and hub height of the disk.
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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.
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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.
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회전하는 덕트내 설치된 $70^{\circ}$ 경사요철의 열전달 특성
최청,이세영,원정호,조형희,박병규,Choi, Chung,Lee, Sei Young,Won, Jung Ho,Cho, Hyung Hee,Park, Byung kyu 한국유체기계학회 2001 한국유체기계학회 논문집 Vol.4 No.3
The present study investigates convective heat/mass transfer and flow characteristics inside a cooling passage of rotating gas-turbine blades. The rotating duct has staggered ribs with $70^{\circ}$ attack angle, which are attached on leading and trailing surfaces. Naphthalene sublimation technique is employed to determine detailed local heat transfer coefficients using the heat and mass transfer analogy. Additional numerical calculations are conducted to analyze the flow patterns in the cooling passage. The present experiments employ two-surface heating conditions in the rotating duct because the exposed surfaces to hot gas stream are pressure and suction side surfaces in the middle passages of an actual gas-turbine blade. Secondary flows are generated by Coriolis and centrifugal forces in the spanwise and streamwise directions. The ribs attached on the walls disturb the mainflow resulting in recirculation and secondary flows near the ribbed wall. The local heat transfer and flow patterns in the passage are changed significantly according to rib configurations and duct rotation speeds. Therefore, the geometry and arrangement of the ribs are important for the advantageous cooling performance. The experimental results show that the ribs enhance the heat transfer more than $70\%$ from that of the smooth duct. The duct rotation generates the heat transfer discrepancy between the leading and trailing walls due to the secondary flows induced by the Coriolis force. The overal heat transfer pattern on the leading and trailing walls for the first and second passes are depended on the rotating speed, but the local heat transfer trend is affected mainly by the rib arrangements.
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LNG선 후드룸의 환기성능 검토 및 효과적 환기를 위한 설계제안
김만응(Mann-Eung Kim),원정호(Chung-Ho Won) 한국마린엔지니어링학회 2004 한국마린엔지니어링학회 학술대회 논문집 Vol.2004 No.-
Hoodroom in LNG(Liquified Natural Gas) Carrier plays an important role for prompt detection and interception of leaked BOG (Boil Off Gas) from double wall fuel piping system for main boiler. Therefore, IGC Code underline the several requirements such as specific air change rate, arrangement and gas detection system. But, any regulated design arrangements for effective ventilation are not clearly presented. The paper would be pleased to prospect the actual ventilation now and propose the design concepts for the improved ventilation effectiveness through the now field and the concentration field analysis by CFD.
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