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이기우,김유,Lee, Ki-Woo,Kim, Yoo 대한기계학회 1988 대한기계학회논문집 Vol.12 No.1
A series of experiments was performed in this study to investigate the boiling heat flux between an impinging water jet and a hot surface. Test variables were surface roughness, jet velocity, saturation temperature excess of surface, nozzle diameter and the gap distance between nozzle plate and the hot surface. In order to make the impinged cooling water a forced flow streaming a long the hot surface immediately after the initial impingement, the flat nozzle tip was extended to a circular flat plate having the same diameter as the hot surface. Utilizing the dimensionless parameter study on continuity, momentum and energy equations, 5 groups of variables involved in the nucleate boiling heat transfer were derived so that it is possible to estimate the increased heat flux by impinging water jet in a similar experimental work. For the case of saturated water being impinging onto a high temperature surface, an applicable correlation among dimensionless parameters describing the heat flux was found to be as follow. 본 연구에서는 표면상태가 다양한 고온면을 충돌온류에 의하여 냉각하는 방식이 광범위하게 응용되고 있는 점에 유의하여 표면조도, 노즐직경 및 분류속도를 변화시키고 노즐끝에 전열면의 직경과 동일한 원형판을 부착하여 비철액체를 막고 문극내에 온류액체를 강제유동시킴으로써 열전달에 미치는 모든 영향을 실험에 의해 고찰하고 고찰하고 포화수온류에 의한 열류속의 무차원관계식을 도출하는 것을 본 연구의 목적으로 하였다.
이기우(Ki-Woo Lee),전원표(Won-Pyo Chun),이욱현(Wook-Hyun Lee),박기호(Ki-Ho Park),이계중(Key-Jung Lee) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6
In this study, the performance prediction and experiment of loop heat pipe(LHP) were performed. A LHP has a wick only in its evaporator for the circulation of working fluid, and utilizes a porous wick structure of which pore size is very small to obtain a large capillary force. The diverse parameters on the operation of loop heat pipe (LHP), such as particle diameter of sintered porous wick, wick porosity, height between evaporator and condenser, and heating capacity affect the performance of LHP. For the LHP that the working fluid is water and the materials of sintered porous wick are stainless and ceramic particle, temperature-pressure distribution, the pressure drop in vapor line and liquid line, and saturation temperature in evaporator and condenser were analyzed by the theoretical design method of LHP and experiment was performed.
스크린메쉬윅 히트파이프에서 윅의 기공율변화에 따른 열수송한계의 이론적 고찰
이기우(Ki Woo Lee),박기호(Ki Ho Park),전원표(Won Pyo Chun),이욱현(Wook Hyun Lee),이계중(Kye Jung Lee) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.11
The purpose of the present study is to investigate the capillary hear transportation limitation in heat pipe according to the change of screen mash wick porosity. Diameter of pipe was 6mm, and mesh numbers are 100, 150, 200 and 250 and water was selected as a working fluid. According to the change of wick porosity and mesh number, the capillary pressure, pumping pressure, liquid friction coeffcient in wick, vapor friction coefficient, and capillary heat transportation limitation are analyzad by theoretical desigm method of a heat pipe. As some results, the capillary heat transportation limitation in screen mesh wick heat pipe is largely affected by wick porosity and mesh namber.
사이폰없는 실린더드럼에서 다중유로에 의한 응축수배출에 관한 실험적 연구
이기우(Ki Woo Lee),전원표(Won Pyo Chun),이계중(Kye Jung Lee),하재청(Jae Cheong Ha) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.5
Cylinder drum dryer tor paper drying is the method which drys the wetted paper flowing on surface of drum by steam. The condensate, which the steam transfers the heat to the surface of drum for paper drying and is condensed, must be removed for continuous drying. In this paper, the condensate removal and heat transfer characteristics were experimented according to steam pressure, revolution of drum and height of flow channel by multi-f1ow channel in cylinder drum without syphon. And these heat transfer characteristics were compared with the case of conventional type with syphon for condensate removal. As the experimental results, the minimum steam pressure existed for the removal of condensate by steam pressure without siphon, and heat transfer quantity in cylinder drum with multi-flow channel was approximately increased to 28% compared to conventional drum. Accordingly, application effect on this technology was expected to be great, but a lot of steam was exhausted with condensate, so this problem must be improved for the commercialization of cylinder dryer with multi-t1ow channels.
AMTEC의 소디움액체 순환윅에서 압력손실 및 열손실해석
이기우(Ki Woo Lee),이욱현(Wook Hyun Lee),이석호(Seok Ho Rhi),이계복(Kye Bock Lee) 대한기계학회 2012 大韓機械學會論文集B Vol.36 No.9
AMTEC기술은 열을 직접 전기로 변환시키는 기술로서 소디움을 작동유체로 사용하고 있으며, 작동유체의 순환은 모세관윅을 사용한다. 순환계통에는 증발부윅, 순환윅 및 응축부윅으로 구성되고, 각각의 윅은 소디움의 액체 또는 증기가 순환하면서 압력손실이 발생하므로 소디움의 순환을 위해서는 증발부윅의 모세관압력이 윅내의 총압력손실보다 커야만 한다. 본 연구에서는 100 watt급의 AMTEC시제품설계을 위해 소디움의 순환계통으로 구성되는 증발부윅, 순환윅 및 응축부윅에서의 압력손실과 증발부에서 응축부로의 열손실을 순환윅의 직경과 길이에 대해 분석하여 증발부윅의 소결입자 직경과 순환윅의 설계에 활용하코저 하였으며, 분석결과에서 순환계통의 총압력손실보다 큰 모세관압력을 위해서는 증발부윅의 소결입자크기는 10 μm이 적합한 결과를 얻었다. An AMTEC (alkali metal thermal electric converter) is a device that is used for the direct conversion of heat to electricity. Sodium is used as the working fluid, and its circulation is driven by a capillary wick. The wicks used for circulation include an evaporator wick, artery wick, and condenser wick, and each wick has a pressure drop because of the circulation of liquid and vapor. For the circulation of sodium, the capillary pressure of the evaporator wick must be greater than the total pressure drop in the wicks. In this study, the pressure drop in the evaporator wick, artery wick, and condenser wick and the heat loss from the evaporator to the condenser through the artery wick were analyzed for the design of a 100 WAMTEC prototype. It was found that a particle diameter of 10 μm is suitable for the evaporator wick to maintain a capillary pressure greater than total pressure drop in the circulation loop.
제지건조기용 실린더드럼에서 열전달특성에 관한 이론적 분석
이기우(Ki-Woo Lee),전원표(Won-Pyo Chun),이계중(Kye-Jung Lee),장석필(Seok-Pil Jang) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.11
The heat transfer process from steam to web through the cylinder drum consists of the thermal resistance by condensate thickness, thickness of shell, and the contact resistance between cylinder and web. The most thermal resistance in conventional cylinder drum dryer is generated by condensate, which is increased by the increase on revolution per minute(RPM). Therefore, the increase of RPM for the production enhancement results in the more thermal resistance, and eventually RPM is restricted. In this study, the theoretical analysis on the characteristics of heat transfer in cylinder drum for paper dryer was performed in the stationary state of steam in drum. The overall heat transfer coefficient, steam quantity and heat transfer quantity were predicted by diameter and length of drum, condensate thickness, revolution per minute and steam temperature for experimental apparatus design.