http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
동심환형 곡관의 혼합대류 열전달 현상에 관한 수치적 연구
최훈기,유근종 한국에너지학회 2002 에너지공학 Vol.11 No.4
동심환형 곡관의 내벽면에서 일정한 열전달이 있는 경우에 대하여 혼합대류의 유동장 및 열전달계수를 수치적으로 구하였다. 유동장은 주흐름방향으로의 압력과 온도구배가 일정한 완전발달흐름으로 가정하였다. 유동장의 특성을 나타내는 물리적 변수인 반경비는 0.2, 0.5, Grashof수는 8000, 80000 그리고 Dean수는 0-900범위에서 계산을 실시하였다. 반경비, Grashof수, Dean수를 변화시키며 2차유동, 열유속, 마찰비, 열전달계수에 대한 수치해를 구하였다. 마찰비와 Nusselt수는 Dear수의 제곱근에 비례하게 증가됨을 볼 수 있다. Numerical calculations have been carried out for the mixed convection flow in a concentric curved annulus with constant heat flux boundary condition at inner wall. The flow is assumed to be fully developed so as to maintain a constant streamwise pressure and temperature gradient. Computations have been performed for flows of radius ratio 0.2 and 0.5 with the Dean number lying in the range 0<k<900, and Grashof numbers of 8000 and 80000. The second flow patterns and heat flux profiles are presented. The friction ratio and heat transfer properties for curved annular duct flows are explained in comparison with those for straight annular duct flows. It is found that the friction ratio and the Nusselt number ratio are proportional to $K^{1/2}$ for the wide range of the Dean number considered here.
최훈기,유근종,임윤승 한국기계가공학회 2018 한국기계가공학회지 Vol.17 No.2
A vortex tube is a simple energy separating device that splits a compressed air stream into a cold andhot stream without any external energy supply or chemical reactions. The efforts of many researchers anddesigners have been focused on improvement of vortex tube efficiency by changing the parameters affectingvortex tube operation. The effective parameters are nozzle specifications and inflow pressure conditions. Effects of different nozzle cross-sectional area and number of nozzles are evaluated by computational fluiddynamics (CFD) analysis. In this study, CFD analysis of 3-D steady state and turbulent flow through avortex tube was performed . We investigated the cold air mass flow rate, the cold air temperature, and thecold air heat transfer rate behavior of a vortex tube by utilizing seven straight nozzles and four inflowpressure conditions.
열교환기의 슬릿-웨이브 핀 성능에 대한 수치해석적 연구
최훈기,조성원,박용갑 대한기계학회 2022 大韓機械學會論文集B Vol.46 No.7
In this study, a numerical simulation was performed on the heat transfer and flow characteristics of a slit-wavy fin-and-tube heat exchanger. ANSYS FLUENT 2020 R1 was used to analyze. This study was conducted on different Reynolds numbers (66, 133, 332, 532, 665) and slit-wavy fin angles (0°, 5°, 10°, 15°, 20°). The results were visually represented using the dimensionless temperature contour and streamline. Finally, the heat transfer and flow characteristics according to the variation Reynolds number and slit-wavy fin angles was investigated using the j and f factors. When the Reynolds number was 66, the j and f factors of slit-wavy fins with an angle of 20° increased by 41% and 85%, respectively, compared to the plain fin. When the Reynolds number was 665, the j and f factors of slit-wavy fins with an angle of 20° increased by 83% and 145%, respectively, compared to the plain fin. 본 연구에서는 슬릿-웨이브 핀 튜브 열교환기의 열전달 및 유동 특성에 대한 수치해석을 수행하였다. 해석에는 ANSYS FLUENT 2020 R1을 이용하였다. Reynolds 수(66, 133, 332, 532, 665)와 슬릿-웨이브 핀의 각도(0°, 5°, 10°, 15°, 20°)의 변화에 대하여 해석을 수행하였다. 무차원 온도장과 유선을 사용하여 결과를 시각적으로 나타내었다. 최종적으로 Reynolds 수와 슬릿-웨이브 핀의 각도 변화에 따른 열전달 및 유동 특성을 무차원수 j factor와 f factor로 나타내었다. 평판 핀과 비교하여 슬릿-웨이브 핀의 각도가 20°인 경우, Reynolds 수가 66에서 j factor와 f factor는 각각 41%와 85% 증가하였고 Reynolds 수가 665에서는 각각 83%와 145% 증가하였다.
최훈기,유근종,박태봉,은재정,장남영 국립7개대학공동논문집간행위원회 2003 공업기술연구 Vol.3 No.-
Numerical analysis is performed for magnetic and MHD flow fields in Electro-Magnetic(EM) pump. A finite volume method is applied to solve magnetic field governing equations and the Navier-Stokes equations. Vector and scalar potential methods are adopted to obtain the electric and magnetic fields and the resulting Lorentz force in solving Maxwell equations. The magnetic field and velocity distributions are found to be influenced by the magnitude of the Reynolds number and the phase of applied electric current. Computational results indicate that the magnetic flux distribution with changing phase of electric current is characterized by a pair of counter-rotating closed loops. The velocity distribution of the flow field is influenced on the intensity of Lorentz force.