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LED 조명 방열 환경에서 진동형 히트파이프의 작동 특성
방광현,김형탁,박해균,Bang, Kwang-Hyun,Kim, Hyoung-Tak,Park, Hae-Kyun 한국전기전자재료학회 2012 전기전자재료학회논문지 Vol.25 No.10
An efficient cooling system is essential for the electronic packaging such as a high-luminance LED lighting. A special heat transport technology, Pulsating Heat Pipe (PHP), can be applied to the cooling of LED lighting. In this paper, the operational characteristics of the PHP in the imposed thermal boundary conditions of LED lighting were experimentally investigated. The experimental PHP was made of copper tubes of internal diameter of 2.1 mm. The working fluids of ethanol, FC-72, water, acetone and R-123 were chosen for comparison. The results showed that an optimum range of charging ratio exists for high cooling performance; 50% for most of the fluids. Among the five working fluids, water showed the highest heat transfer rate of 260 W. Two distinguished characteristics of pulsating direction were identified. It is also identified that high vapor pressure gradient is one of key parameters for better heat transfer performance.
방광현(Kwang-Hyun Bang),김경규(Kyung-Kyu Kim),김상진(Sang-Jin Kim) 한국마린엔지니어링학회 2009 한국마린엔지니어링학회 학술대회 논문집 Vol.2009 No.-
An high-efficiency intercooler for high-power Diesel engine power pack has two separate cooling circuits of high-temperature and low-temperature, thus three fluid paths of high and low temperature coolants and the charge air are involved in this type of heat exchanger. A cell-by-cell thermal rating method is employed to design and calculate the thermal rating of the intercooler. A model intercooler has been designed and fabricated and the measurement of thermal performance of the model intercooler shows good agreement with the design calculations.
초고온원자로 중간열교환기 미니챈널에서의 Molten Salt 열수력 특성 연구
방광현(Kwang-Hyun Bang),정희성(Hui-Seong Jeong) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.5
To make the design of the Very High Temperature Reactor (VHTR) complete and plausible, the designs of the Intermediate Heat Transport Loop (IHTL) as well as the Intermediate Heat Exchanger (IHX) are known to be one of the difficult engineering tasks due to its high temperature operating condition (up to 950℃). In this study, Flinak molten salt, a eutectic mixture of LiF, NaF and KF (46.5: 11.5:42.0 mole %) is considered as the potential heat transporting fluid in the IHTL. To evaluate the flow and heat transfer performance of the Flinak molten salt in small channels of millimeter-range hydraulic diameters, a double-pipe type heat exchanger was constructed using small-diameter tubes for the heat exchange between the Flinak and gas flow. The experimental data showed that, for laminar flow of Flinak, the measured friction factors were close to the MIRe curve and the Nusselt numbers were generally in the range between 3.66 and 4.36.
방광현(Kwang-Hyun Bang),윤태영(Tae-Young Yoon),홍군의(Kun Eui Hong) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5
Flow boiling heat transfer in a microchannel has been experimentally studied. The experimental apparatus consisted mainly of peristaltic pump, pre-heater, test section and vacuum chamber for control of operating pressure. Deionized water was used as the working fluid and a single round microchannel of 310 ㎛ inside diameter, made of 304 stainless steel, is used for the test tube. The experiment has been performed for the condition of heat flux from 35 to 86 kW/㎡, mass flux from 203 to 305 kg/㎡s (Re=168~254) and exit pressure from 11 ㎪ to 20 ㎪. The experimental results showed that the flow boiling heat transfer coefficients in microchannel were affected by heat flux and operating pressure, while slightly dependent on mass flux.
표면 처리에 따른 Inconel 617 합금의 고온 특성
조현,방광현,이병우,Cho, Hyun,Bang, Kwang-Hyun,Lee, Byeong-Woo The Korea Association of Crystal Growth 2009 韓國結晶成長學會誌 Vol.19 No.6
고온 열수송시스템용 구조재료인 Inconel 617의 표면 처리에 따른 고온물성 개선에 대한 연구를 수행하였다. 표면처리 방법으로는 Inconel 617 기판 상에 급속가열(RTP) 및 수열처리를 통한 균질산화물 형성과 물리적 기상증착법(Arc discharge)법에 의한 TiAlN(두께 약 $2{\mu}m$ 박막 코팅을 적용하였다. 불균질 산화물($Cr_2O_3$) 형성 억제에 미치는 표면처리의 효과 및 표면 미세구조가 물성에 미치는 영향에 대해 알아보기 위해 표면처리된 Inconel 617 시편들을 $1000^{\circ}C$, 대기중에서 열처리 하였으며, 열처리된 시편들에 대해 고온 상형성 및 미세구조를 비교 분석하였다. RTP와 수열처리를 통한 표면산화물 형성보다는 TiAlN 박막 증착을 통한 보호피막의 형성이 Inconel 617 표면에서 생성되는 불균일 $Cr_2O_3$ 막의 성장을 효과적으로 억제할 수 있어서 더 균질한 미세구조와 가장 우수한 내마모 특성을 나타내었다. The effect of the surface treatments on the high temperature properties of the Inconel 617, one of the promising candidate alloys for high temperature heat-transport system, has been studied. Various surface modification methods including a rapid thermal process(RTP), a hydrothermal treatment, and a physical vapor deposition($2{\mu}m$ thick TiAlN film by an arc discharge) were applied to the Inconel 617. The morphological and the structural properties of the surface-modified Inconel 617 samples after heat treatment at $1000^{\circ}C$ in the air were compared to find out whether inhomogeneous formation of $Cr_2O_3$ crust at the surface region was suppressed or not. TiAlN-coated Inconel 617 showed homogeneous microstructure and the lowest wear loss compared to bare, RTP- and hydrothermally-treated Inconel 617 by suppressing the $Cr_2O_3$ crust formation.
표면처리된 Ni-Cr계 합금의 FLiNaK 용융염 하에서의 고온 안정성
조현,방광현,이태석,이병우,Kwang, Hyun Cho,Bang, Hyun,Lee, Tae Suk,Lee, Byeong Woo 한국결정성장학회 2012 韓國結晶成長學會誌 Vol.22 No.5
차세대 원자력발전용 고온 열교환기 소재로 이용될 가능성이 높은 Ni-Cr계 고온합금인 Inconel 617과 Hastelloy X의 표면처리에 따른 FLiNaK(LiF-NaF-KF) 용융염 하에서의 고온물성에 대한 연구를 수행하였다. Inconel 617과 Hastelloy X기판 상에 각각 PVD인 arc discharge 및 sputtering법에 의해 TiAlN 및 $Al_2O_3$ 박막을 코팅 하였다. 이러한 표면처리가 이들 합금의 FLiNaK 용융염 하 고온 안정성에 미치는 영향에 대해 연구하였다. 용융염 하 Ni-Cr계 고온합금의 부식 원리를 이해하기 위해, 용융염 수송 loop에 사용 중 파단된 Inconel 파이프에 대한 미세구조 분석을 수행하였다. 표면처리 된 합금들을 $600^{\circ}C$ 용융염 내에서 열처리 하였으며, 열처리 전후 시편들에 대해 상형성, 미세구조 등 고온 물성 변화를 측정하였다. 연구결과 코팅되지 않은 경우 보다 TiAlN 및 $Al_2O_3$ 박막이 코팅된 소재에서 보다 우수한 고온 안정성을 보여주었다. Inconel 617 and Hastelloy X are the most promising candidate materials for the heat exchanger of next generation nuclear reactor. Surface coating and its effects on high temperature properties for the Inconel 617 and Hastelloy X under molten FLiNaK (LiF-NaF-KF) salt environment have been investigated. For TiAlN and $Al_2O_3$ overlay coatings, the two different PVD (physical vapor deposition) methods of an arc discharge and a sputtering were applied, respectively. A study for the thermal stability of the surface modified Ni-Cr alloy substrates has been conducted. To evaluate the corrosion mechanism of Ni-Cr alloys in the molten salt, a ruptured Inconel pipe used for the molten salt transportation has been analyzed. The thermal properties of morphological and structural properties each sample were characterized before and after heat-treatment at $600^{\circ}C$ in molten FLiNaK salt. The results showed that the TiAlN and $Al_2O_3$ overlay coated specimens had the enhanced high temperature stability.
도덕희,김동혁,방광현,문지섭,홍성대,장태현,황태규,Doh Deog Hee,Kim Dong Hyuk,Bang Kwang Hyun,Moon Ji Seob,Hong Seong Dae,Chang Tae Hyun,Hwang Tae Gyu 한국마린엔지니어링학회 2005 한국마린엔지니어링학회지 Vol.29 No.2
Thermo-chromic Liquid Crystal(TLC) particles were used as temperature sensor for thermal fluid flow. 1K $\times$ 1K CCD color camera and Xenon Lamp(500w) were used for the visualization of a Hele-Shaw cell The characteristic between the reflected colors from the TLC and their corresponding temperature shows strong non-linearity A neural network known as having strong mapping capability for non-linearity is adopted to quantify the temperature field using the image of the flow. Improvements of color-to-temperature mapping was attained by using the local color luminance (Y) and hue (H) information as the inputs for the constructed neural network.