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엔진실 차폐 시스템의 냉각성능 개선을 위한 수치적 연구
배이석(Y.S. Bae),유근종(G.J. Yoo),최훈기(H.K. Choi) 한국전산유체공학회 2009 한국전산유체공학회지 Vol.14 No.2
In engine room, proper enclosure system is preferable for reducing noise level but the enclosure system in the engine room causes bad influence on cooling performance due to poor ventilation. Cooling efficiency of the enclosure system can be improved by varying fan speed and proper .flow path for ventilation. In this study, numerical analysis is pelf armed to assess cooling effect of the enclosure system using finite volume method. The RNG k-ε model is adopted for turbulence model along with heat exchanger model and porous media model for heal exchanger analysis, and moving reference frame model for rotational Ian. Verification result shows reasonable agreement with experimental data. Analysis results show direct effect of velocity and temperature distribution on cooling ability in the enclosure system. Enclosure system of case B shows high heat transfer coefficient and has the smallest area ratio of opened flow passages which is good for noise level reduction.
동심이중관내 나노유체의 자연대류열전달에 관한 수치적 연구
최훈기(H.K. Choi),박재훈(J.H. Park),유근종(G.J. Yoo) 한국전산유체공학회 2016 한국전산유체공학회지 Vol.21 No.3
In the present study, the homogeneous model is used to simulate the natural convection heat transfer of the CuO-water nanofluid in a concentric annular enclosure. Simulations have been carried while the Rayleigh number ranges from 10² to 10<SUP>6</SUP>, solid volume fraction ranges from 0.01 to 0.04 and the radius ratio varies between 0.1 and 0.7. Results are presented in the form of streamlines, isotherm patterns and averaged Nusselt numbers for different values of solid volume fraction, radius ratio of the annulus and Rayleigh numbers. The results show that by decreasing the radius ratio and/or increasing the Rayleigh number, the averaged Nusselt number increases. Also the heat transfer rate increases as increased solid volume fractions.
최훈기(H.K. Choi),유근종(G.J. Yoo),신병주(B.J. Shin),김철환(C.H. Kim) 한국전산유체공학회 2010 한국전산유체공학회지 Vol.15 No.1
Performance improvements of the heat recovery steam generator(HRSG) can be achieved by improving the flow distribution of exhaust gases for a various type of different equipments. A number of design parameters are systematically investigated and their effects on an index of velocity deviation established. The parameters include the three shape of the transition duct and the wide range of the guide vane angles. The numerical results clearly reveal feature of the flow pattern in the transition duct, velocity deviation and pressure drop at tube bank part.
최훈기(H.K. Choi),유근종(G.J. Yoo),김인호(I.H. Kim) 한국전산유체공학회 2007 한국전산유체공학회지 Vol.12 No.4
Numerical analysis is carried out for combined heat transfer in an indirected NIR(Near Infrared Ray) heating chamber. Reynolds number and shapes of absorbed cylinder are known as important parameters on the combined heat transfer effects. Reynolds number based on the outer diameter of the cylinder is varied from 10³ to 3×10?. Four difference heat transfer regimes are observed: forced convection and radiative heat transfer on the outer surface of the cylinder, pure conduction in the cylinder body, pure natural convection and radiation between lamp surface and inner surface of the cylinder, and radiation from the lamp. Flow and temperature characteristics are presented with iso-contour lines for the absorbed circular and elliptic cylinders to compare their differences. The convective and radiative heat transfer fluxes are also compared with different Reynolds numbers. As usual, Reynolds number is an important factor to estimate increasing convective heat transfer as it increases. The shape of absorbed cylinder results overall heat transfer rates remain unchanged.
보텍스튜브 유동의 에너지분리 및 열역학특성에 관한 수치적 연구
최훈기(H.K. Choi),유근종(G.J. Yoo),임윤승(Y.S. Lim) 한국전산유체공학회 2018 한국전산유체공학회지 Vol.23 No.2
A vortex tube is a simple energy separating device which splits a compressed air stream into a cold and hot stream without any external energy supply or chemical reactions. In this article computational fluid dynamics analysis of a 3-D steady state and turbulent flow has been carried out through a vortex tube. The present research has focused on the energy separation and thermodynamic behavior of a vortex tube have been investigated. The temperature separation occurs because of the heat transfer from the central flow to the peripheral flow. Through the interpretation of the second law of thermodynamics, the generation of entropy shows that irreversible processes occur in the vortex tube.