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사각채널에 설치된 배플이 열전달과 마찰계수에 미치는 효과
안수환,강호근,배성택,송민호,Ahn, Soo-Whan,Kang, Ho-Keun,Bae, Sung-Taek,Song, Min-Ho 한국마린엔지니어링학회 2006 한국마린엔지니어링학회지 Vol.30 No.6
The present work investigates the local heat transfer characteristics and the associated frictional loss in a rectangular channel with inclined solid and perforated baffles to obtain the basic design data for gas turbine. Five different geometries of baffles such as 1) solid (without hole), 2) three holes, 3) six holes, 4) nine holes, 5) twelve holes were covered. A combination of two baffles of same overall size is used. The flow Reynolds number is ranged from 28,900 to 70,100. The placement of baffles augments the overall heat transfer greatly by combining both jet impingement and the boundary layer separation. The present results show that the average Nusselt number distribution is strongly dependent on number of holes in the baffle plates, i.e., the average Nusselt number increases with increasing number of holes. The friction factor decreases also with increasing the number of holes. however. its value increases with increasing the Reynolds number.
수평Y자형 분지관에서 증기-물 이상류의 상분리에 관한 실험적 연구
안수환,Ahn, Soo-Whan 대한기계학회 2000 大韓機械學會論文集B Vol.24 No.6
The Characteristics of dividing the dispersed bubble, plug, and slug steam-water flow in the horizontal junctions with horizontal branches have been experimentally investigated. The experimental investigation of the separation phenomena in a $45^{\circ}$ horizontal wye with equal pipe inner diameter of 25 mm is presented to provide a data base for the development and verification of the analytical models. The phase separation and pressure distribution in the three legs of each test section are obtained through the set of measurements made in the present work. And the dependence of phase separation on different parameters, such as inlet quality and mass flux, is discussed.
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.
안수환(Soo Whan Ahn),배성택(Sung Taek Bae),김명호(Myoung Ho Kim),이병창(Byung-Chang Lee) 한국동력기계공학회 2004 한국동력기계공학회 학술대회 논문집 Vol.- No.-
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 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
45° 경사진 거칠기가 있는 채널에서 열전달과 마찰계수에 대한 실험과 수치 해석
안수환(Soo Whan Ahn),강호근(Ho Keun Kang),김명호(Myoung Ho Kim) 한국동력기계공학회 2005 한국동력기계공학회 학술대회 논문집 Vol.- No.-
Three dimensional numerical simulations of incompressible turbulent flow and heat transfer through square channels with varying number of ribbed walls were performed too determined pressure drop and heat transfer. The CFX (version 5) software package was used for the computation. The rough wall have a 45˚ inclined square rib. Uniform heat flux is maintained on whole inner heat transfer channel area. The numerical results agreed well with experimental data that obtained for 7,600 < He < 24,900, the pitch-to-rib height ratio (p/e) of 8.0, and the rib height-to-channel hydraulic diameter ratio (e/Dh) of 0.0667. All four walls in the channel are heated. The results show that values of local heat transfer coefficient and friction factor increase with an increasing number of ribbed walls.
2벽면 확대 사각채널에서 리브 피치가 열전달과 마찰계수에 미치는 효과
안수환(Soo Whan Ahn),이명성(Myung Sung Lee),정성수(Seong Soo Jeong),배성택(Sung Taek Bae) 대한설비공학회 2014 설비공학 논문집 Vol.26 No.4
Experimental investigations of the heat transfer and friction factors in the ribbed divergent rectangular channel with the channel exit hydraulic diameter to inlet hydraulic diameter ratio of 1.16 were performed. The surface heaters were mounted onto the two opposite walls. The main experimental parameter is the ratio of rib pitch (p) to height (e), at which the ratios (p/e) of 6, 10, and 14 are considered in the channel with ribs on one wall only. The straight ribbed square channel is also considered as a comparison. The major findings are that the ratio of p/e = 6 shows the highest values in the heat transfer and the ratio of p/e = 10 indicates the greatest friction factor in the ribbed divergent channel.
한면에 리브가 설치된 4벽면 수축/확대 채널의 난류 열전달과 유체마찰
안수환(Ahn Soo Whan),이명성(Lee Myung Sung) 대한기계학회 2015 大韓機械學會論文集B Vol.39 No.10
가스터빈 냉각 장치인 블레이드 등과 같은 산업 설계를 개선하기 위해 사각 수축 및 확대채널에서 축방향의 거리에 따라 국부 난류 열전달과 압력강하에 대해 실험적으로 조사하였다. 수축 및 확대채널의 한 면에만 리브(10 mm x 100 mm x 5 mm(t))를 연속적으로 배치하였고 충돌 각은 90°로 피치(p)/높이(e)의 비는 10이 되도록 하였다. 수축채널의 수력직경비(Dho/Dhi )는 0.75, 확대채널의 수력직경비는 1.33 그리고 직선채널은 1.00이다. 열성능 비교를 위해 3가지 보편적인 제약 조건을 채택 하였다. 즉 동일 유량, 동일 펌프 동력 그리고 동일한 압력 강하이다. 3가지 조건모두 확대 채널에서 우수한 열 성능을 보였다. The local heat transfer and pressure drop of developed turbulent flows in convergent/divergent channels with square axial cross-sectional areas were experimentally investigated to improve the channel design, such as a gas turbine cooling system. Square convergent/divergent channels with one ribbed wall were manufactured with a fixed rib height e of 10 mm and a ratio of rib spacing p to height e of 10. The measurement was conducted for Reynolds numbers from 15,000 to 89,000. Convergent, divergent, and straight channels with ratios Dho/Dhi of 0.75, 1.33, and 1.0, respectively, are considered. Of the three channel types, the ribbed divergent channel was found to produce the best thermal performance under identical flow rate, pumping power, and pressure loss conditions.
바닥에만 거칠기가 설치된 사각채널에서 채널의 왕복운동이 열전달에 미치는 효과
안수환(Soo Whan Ahn),김명호(Myoung Ho Kim),김형록(Hyoung Rok Kim),안경헌(Kyung Hun An) 한국동력기계공학회 2005 한국동력기계공학회 학술대회 논문집 Vol.- No.-
The improvements of the propulsive engine efficiencies could reduce the fuel consumption. Therefore, for a marine main diesel engine, the substantial increase of stroke bore ratio, so that the engine speed can be significantly reduced in order to increase the propulsive efficiency. As a typical example, a Sulzer RTA 60C engine has a cylinder diameter of 600 ㎜ and each cylinder is capable of delivering 2,369 ㎾ in the speed range 91-114 rpm. In order to provide basic data for thermal system of marine engine, this work performs an experimental study of heat transfer in a square channel with one rib-roughened wall under single mode of reciprocating oscillation. A selection of heat transfer measurements illustrates the manner by which the reciprocating channel with two opposite heating walls has the higher heat transfer performance than with four heating wall.
양측면 수축/확대 사각채널에서 한면에 설치된 리브의 각도가 열성능에 미치는 효과
안수환(Soo Whan Ahn),이명성(Myung Sung Lee),배성택(Sung Taek Bae) 대한설비공학회 2015 설비공학 논문집 Vol.27 No.4
The thermal performance in the channels with two-wall rectangular convergent/divergent cross-sectional areas along the axial distance was investigated experimentally. The ribbed rectangular convergent/divergent channels were manufactured with a fixed rib height (e) = 10 mm and the ratio of rib spacing (p) to height (e) = 10. Three different parallel angled ribs (a = 30°, 45°, and 60°) were each placed on the channel’s one sided wall only. The convergent channel of Dho/Dhi = 0.67 and the divergent channel of Dho/Dhi = 1.49 were considered. The ribbed divergent channel produced better thermal performance than the ribbed convergent channel in three different restrictions; identical flow rate, identical pumping power, and identical pressure loss.