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비정상 자연대류에 의한 온도성층화의 동특성에 관한 연구
강보선,이준식,이택식,노승탁,Kang, B.S.,Lee, J.S.,Lee, T.S.,Ro, S.T. 대한설비공학회 1988 설비저널 Vol.17 No.4
Dynamic characteristics of thermally-forced stratification process in a square enclosure with a linear temperature profile at the side walls have been investigated through flow visualization experiment and numerical analysis. The experiment was performed on air with the Rayleigh numbers of order $10^5$. A particle tracer method is used for the flow visualization and to obtain a sudden linear temperature profile at the side walls copper blocks which already have a linear temperature profile are come into contact with the thin copper plates of the test section. Immediately a meridional circulation is developed and heat transfer takes place from the wall to the interior region by circulation of fluid and finally a thermal stratification is achieved. In the numerical study, QUICK scheme for convective terms, SIMPLE algorithm for pressure correction, and the implicit method for the time marching are adopted for the integration of conservation equations. Comparison of flow visualization and numerical results shows that the developing flow patterns are very similar in dynamic nature even though there is a time lag due to the inevitable time delay in setting up a linear temperature profile. For high Rayleigh numbers, the oscillatory motion is likely to take place and stratified region is extended. However, initial temperature adjustment process is much slower than that for low Rayleigh numbers.
강보선 ( B. S. Kang ),이신표 ( S. P. Lee ) 한국분무공학회 2014 한국액체미립화학회지 Vol.19 No.2
Nanofluids is that metallic or nonmetallic nanometer-sized particles are dispersed in liquid and they can be used in various fields to increase the heat transfer rate. This study conducted experiments to evaluate whether the cooling efficiency of nanofluids is better than that of water in spray cooling. A heated surface was designed and fabricated to make the temperature distribution be linear, which was confirmed by three thermocouple measurements under the heated surface. Spray cooling experiments were conducted using water, 0.2% wt. (weight), and 0.5% wt. Al2O3 nanofluids at the pressure of 0.2 MPa and 0.3 MPa. Based on the results, it is shown that the cooling efficiency of nanofluids is higher than that of water especially in the region of single phase heat transfer. As a result, we can expect that nanofluids can be used as efficient coolants in the cooling of electronic packages where the temperature of the heated surface is not high enough for boiling incipience.
강보선 ( B. S. Kang ),이신표 ( S. P. Lee ) 한국분무공학회 2014 한국액체미립화학회지 Vol.19 No.2
Nanofluids are that metallic or nonmetallic nanometer-sized particles are dispersed in liquid. They can be used in various fields to increase the heat transfer rate because the thermal conductivity of nanofluids can be increased significantly. Nanofluids may be used as a good alternative of coolants in spray cooling. This study conducted experiments to compare the characteristics of sprays between water and nanofluid sprays. The radial distributions of droplet velocities and diameters of water, 0.2% wt.(weight), and 0.5% wt. Al2O3 nanofluids at the pressure of 0.2 and 0.3 MPa were measured by laser doppler instruments. The radial distributions of droplet diameters and velocities at two axial positions with water and 0.2% wt. nanofluid sprays didn’t show much difference. A big difference, however, was observed between 0.5% wt. nanofluid and water sprays. With the increase of the mass of nano-particles, the average droplet diameters were increased and the average droplet velocities were decreased.
강경조 ( K J Kang ),윤인상 ( I S Yoon ),이방래 ( B R Lee ),강보선 ( B S Kang ) 한국액체미립화학회 2013 한국액체미립화학회 학술강연회 논문집 Vol.2013 No.-
Nanofluids are that metallic or nonmetallic nanometer-sized particles are dispersed in liquid. They can be used in various fields to increase the heat transfer rate because the thermal conductivity of nanofluids can be increased significantly. Nanofluids may be used as a good alternative of coolants in spray cooling. This study conducted experiments to compare the characteristics of sprays between water and nanofluid sprays. The radial distributions of droplet velocities and diameters of water, 0.2% wt.(weight), and 0.5% wt. Al2O3 nanofluids at the pressure of 0.2 and 0.3 MPa were measured by laser doppler instruments. The radial distributions of droplet diameters and velocities at two axial positions with water and 0.2% wt. nanofluid sprays didn’t show much difference. A big difference, however, was observed between 0.5% wt. nanofluid and water sprays. With the increase of the mass of nano-particles, the average droplet diameters were increased and the average droplet velocities were decreased.
김영인,강보선,김용찬,Kim Y. I.,Kang B.S.,Kim Y. C. 대한설비공학회 1989 설비저널 Vol.18 No.2
과학산업의 육성책으로서 정부에서는 1988년도부터 특정출연연구 개발과제로 극한기술 개발을 시작하였다. 본 연구개발 과제는 극한기술의 5개 분과중 하나인 극저온 기술 분야에서의 연구개발목표인 SQUID(Superconductive Quantum Interference Devices)의 냉각장치로 사용되는 극저온용 냉동기 개발이다. 1988년부터 3년간, 연구개발비 약 3억원을 투자하여 작동온도 4.2K에서 약 100mW의 냉각능력을 갖는 냉동기에 대한 시제품을 개발함이 목적이다. 본 기술논문에서는 지난 6개월간의 연구수행 내용을 개략적으로 기술하여 연구진행상황을 파악할 수 있도록 하였다.
노현석 ( H S Roh ),강보선 ( B S Kang ) 한국분무공학회 2013 한국액체미립화학회지 Vol.18 No.3
Digital holographic particle velocity measurement system can be a promising optical tool for the measurements of three dimensional particle velocities. In this research, validation experiments for the digital holographic particle velocity measurement system were conducted with measuring the velocities of glass beads on a rotating disk. Uncertainty analysis was performed to identify the sources of all relevant errors and to evaluate their magnitudes. The measurement results of particle velocities obtained with digital holographic method are compared reasonably well with the known values within acceptable range of errors. Moreover, digital holographic method showed better performance compared with that of optical holographic system.
단일 액적의 고체 표면 액막과의 충돌 현상에 관한 연구
고천석 ( C S Ko ),유준호 ( J H Yu ),최낙완 ( N W Choe ),강보선 ( B S Kang ) 한국분무공학회 2013 한국액체미립화학회지 Vol.18 No.1
In this paper an experimental study is presented to investigate the dynamic behavior of impacting droplet onto a liquid film. The main parameters are the droplet velocity and the thickness of the liquid film photographic images are presented to show the formation of crown, height, central jet height and the size of disintegrating droplet from the central jct. The diameter and height of crown height of crown are higher for faster droplet and thinner liquid film. On the other hand, the height of cen-tral jet are higher for faster droplet and thicker liquid film. The size of disintegrating droplet from the central jet heavily depends on the droplet velocity; Larger droplet is produced with faster falling droplets.
포스터 전시회 : 단일 액적의 고체 표면 액막과의 충돌 현상에 관한 연구
고천석 ( C S Ko ),유준호 ( J H Yu ),최낙완 ( N W Choe ),강보선 ( B S Kang ) 한국액체미립화학회 2012 한국액체미립화학회 학술강연회 논문집 Vol.2012 No.-
In this paper an experimental study is presented to investigate the dynamic behavior of impacting droplet onto a liquid film. The main parameters are the droplet velocity and the thickness of the liquid film. Photographic images are presented to show the formation of crown, central jet and disintegrating droplet from the central jet. The emphasis is on presenting the time evolution of crown diameter, crown height, central jet height and the size of disintegrating droplet from the central jet. The diameter and height of crown are higher for faster droplet and thinner liquid film. On the other hand, the height of central jet are higher for faster droplet and thicker liquid film. The size of disintegrating droplet from the central jet heavily depends on the droplet velocity; Larger droplet is produced with faster falling droplets.