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RISS 인기검색어
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- 저자 : 백원계(Won Kye Baek) (검색결과 5 건)
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배플 구조에 따른 원통다관형 열교환기의 열전달 특성에 관한 수치해석적 연구
백원계(Won Kye Baek),이성원(Seong Won Lee),함진기(Jin Ki Ham),고준호(Joon Ho Ko) 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.12
Numerical analyses have been performed on a LNG(Liquefied Natural Gas) heat exchanger of the FGSS(Fuel Gas Supply System) of Hyundai Heavy Industries. A type of LNG heat exchanger currently used in FGSS is shell and tube heat exchanger which has been widely used in industrial applications. Material properties variation of the natural gas inside the heat exchanger depending on the temperature has been considered on the numerical analyses. Performance of the heat exchanger is improved by controlling baffle spacing and height, and reduction of pressure drop is verified when the baffle is rotationally periodic structure. It is because the shell-side flow is not zigzag flow but spiral flow. Although the reduction of the pressure drop results in lowering the heat transfer efficiency, it appears that if the rotational angle of baffle becomes smaller, the pressure drop decreases. Accordingly, the rotational baffle leads to higher heat transfer efficiency at the same pressure drop of a general heat exchanger with existing horizontal baffle.
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빠른 속도의 우주먼지 모사를 위한 레이저기반의 입자가속에 관한 실험적 연구
백원계(Won-Kye Baek),여재익(Jai- ick Yoh) 한국항공우주학회 2013 韓國航空宇宙學會誌 Vol.41 No.2
현재 자연적 또는 인공적으로 늘어난 지구 주위의 수많은 미세 입자들은 인공위성에 위협이 되고 있으며 인공위성과 우주 먼지간의 충돌 속도는 수 ㎞/s에 이른다. 본 연구에서 는 이러한 우주 먼지를 모사하기 위하여 작은 금속판을 레이저를 이용하여 가속하였다. 기존 연구에서는 다중코팅을 이용하여 속도 효율을 향상시켰으나 코팅하는데 시간과 비용이 많이 드는 단점이 있었다. 본 연구에서는 그러한 다중코팅 대신 단순한 검은색 페인트를 이용하여 코팅을 하지 않았을 때보다 1.5~2배 정도의 속도향상을 보였으며 Nd:YAG 레이저를 이용하여 1.4J이하에서 최대 1.42㎞/s의 속도를 얻었다. 이 속도는 정지궤도에서의 인공위성과 우주먼지 충돌을 모사하는데 적합하다. Increasing numbers of space debris around the earth now pose a major threat to satellites as their impact velocity may reach up to several ㎞/s. We use a pulse laser to accelerate a miniflyer for mimicking the space debris. The multi-layer coat on the confined medium is known to promote a higher acceleration. However, it requires some special techniques which take somewhat long time and cost to coat. Instead, we devised a simple concept to coat by the black lacquer paint on a flyer. It shows improvement in the flyer velocity by 1.5-2 times the uncoated, and the resulting velocity reached 1.42km/s with Nd:YAG laser energy under 1.4 joules. The resulting velocity is suitable for satellite vulnerability test for debris impact in the geostationary orbit.
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백원계(Won Kye Baek),이경철(Kyeong Chul Lee),김용현(Yong Hyun Kim),여재익(Jai-ick Yoh),신완순(Wan-Soon Sin),고광웅(Kwang-Uoong Koh),김현태(Hyun-Tae Kim) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
Physical phenomena occurred when high energy laser is irradiated on materials are very diverse according to power of irradiated energy, wave length, surface state of materials and so on. Especially in this experiments, metallic materials are the main materials on which high energy laser is irradiated. Experiments are divided into two. First, we irradiated continuous fiber laser(wave length is 1.07㎛) on metallic specimen of which size and thickness change according to power intensity. Second, we investigated the effect of water or other coating on specimens without change of size and thickness using CO₂ laser(wave length is 10.6㎛);power is fixed as 250W. In the first experiment, result showed typical heat transfer because irradiance(W/㎠) is lower than 10?W/㎠. The second experiment showed that damage is much more serious when material is coated.
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선박 폐열회수용 핀-튜브 열교환기의 열전달 및 마찰 인자에 관한 수치해석적 연구
백원계(Won Kye Baek),하정훈(Jung Hoon Ha),함진기(Jin Ki Ham) 대한기계학회 2014 대한기계학회 춘추학술대회 Vol.2014 No.11
Numerical analyses were performed to calculate the heat transfer and friction factor of a finned-tube heat exchanger used for exhaust gas boiler in ships. The heat exchanger has two main design constraints. The first constraint is velocity lower limit to prevent soot of exhaust gas from being deposited. And the second constraint is permissible pressure loss in order to forbid increase of back-pressure which may lead to a high thermal loading of engine components. Based on those reasons, tubes of the boiler have to be arranged in-line so as to decrease amounts of soot deposition. And the tube-diameter of the boiler has to be larger than that of prevalent finned-tube heat exchanger. In this study, the heat transfer and flow friction factor of the presented finned-tube heat exchanger were correlated using computational fluid dynamics since the existing heat transfer and friction correlations are not valid for such a large tube-diameter with in-line arrangement. Number of tube rows was firstly considered because the exhaust gas boiler has formulaic specification as mentioned earlier. The correlation formulas which were obtained from the computational analyses can be used for further studies such as performance prediction or geometrical optimization.
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김용현,백원계,신완순,여재익,Kim, Yong-Hyeon,Baek, Won-Kye,Sin, Wan-Soon,Yoh, Jai-Ick 한국군사과학기술학회 2011 한국군사과학기술학회지 Vol.14 No.6
The beam-matter interaction with various coating effects has received continued attention in the high power laser community. Previous works suggest that coatings promote target damage when compared to beaming on uncoated surface. Three types of paint coatings(Acrylic urethane, Silicone alkyd and Stealth blend) and a water coat on metals(Al, Ti and STS) are irradiated with a $CO_2$ laser. Both strain and temperature measurements are provided for assessing the instantaneous response characteristics of each coating on different metals. A selective combination of surface coats with metals has proven effective in either preventing or enhancing damage, both thermal and mechanical, associated with focused beaming on a target.
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