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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.
ENHANCEMENT OF DRYOUT HEAT FLUX IN A DEBRIS BED BY FORCED COOLANT FLOW FROM BELOW
방광현,김종명 한국원자력학회 2010 Nuclear Engineering and Technology Vol.42 No.3
In the design of advanced light water reactors (ALWRs) and in the safety assessment of currently operating nuclear power plants, it is necessary to evaluate the possibility of experiencing a degraded core accident and to develop innovative safety technologies in order to assure long-term debris cooling. The objective of this experimental study is to investigate the enhancement factors of dryout heat flux in debris beds by coolant injection from below. The experimental facility consists mainly of an induction heater, a double-wall quartz-tube test section containing a steel-particle bed and coolant injection and recovery condensing loop. A fairly uniform heating of the particle bed was achieved in the radial direction and the axial variation was within 20%. This paper reports the experimental data for 3.2 mm and 4.8 mm particle beds with a 300 mm bed height. The dryout heat density data were obtained for both the top-flooding and the forced coolant injection from below with an injection mass flux of up to 1.5 kg/m2s. The dryout heat density increased as the rate of coolant injection increased. At a coolant injection mass flux of 1.0 kg/m2s, the dryout heat density was ~6.5 MW/m3 for the 4.8 mm particle bed and ~5.6MW/m3 for the 3.2 mm particle bed. The enhancement factors of the dryout heat density were 1.6-1.8.
방광현(Kwanghyun Bang),김경규(Kyungkyu Kim),송영아(Younga Song),김평수(Pyungsu Kim) 한국마린엔지니어링학회 2008 한국마린엔지니어링학회 학술대회 논문집 Vol.2008 No.-
Flow field of oil and particles in a centrifugal oil filter has been numerically calculated using Fluent code in order to estimate the filtering efficiency. Uncoupling the oil flow and the discrete phase of particles and the use of particle tracking trajectory enabled the estimation of filtering efficiency for various particle sizes, particle density and the filter RPM.