http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
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.
최훈기(Hoon-Ki Choi),임윤승(Yun-Seung Lim) 한국기계가공학회 2021 한국기계가공학회지 Vol.20 No.6
We compared the heat transfer characteristics of the parallel and the counterflow flow in the concentric double tube of the Al₂O₃/water nanofluids using numerical methods. The high- and low-temperature fluids flow through the inner circular tube and the annular tube, respectively. The heat transfer characteristics according to the flow direction were compared by changing the volume flow rate and the volume concentration of the nanoparticles. The results showed that the heat transfer rate and overall heat transfer coefficient improved compared to those of basic fluid with increasing the volume and flow rate of nanoparticles. When the inflow rate was small, the heat transfer performance of the counterflow was about 22% better than the parallel flow. As the inflow rate was increased, the parallel flow and the counterflow had similar heat transfer rates. In addition, the effectiveness of the counterflow increased from 10% to 22% rather than the parallel flow. However, we verified that the increment in the friction factor of the counterflow is not large compared to the increment in the heat transfer rate.
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.
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(Hoon Ki Choi),유근종(Geun Jong Yoo) 한국전산유체공학회 2014 한국전산유체공학회지 Vol.19 No.3
In this paper, hydraulic & thermal developing and fully developed laminar forced convection flow of a water-Al₂O₃ nanofluid in a circular horizontal tube with uniform heat flux at the wall, are investigated numerically. A single phase model employed with temperature independent properties. The thermal entrance length is presented in this paper. The variations of the convective heat transfer coefficient and shear stress are shown in the entrance region and fully developed region along different nanoparticles concentration and Reynolds numbers. Convective heat transfer coefficient for nanofluids is larger than that of the base fluid. It is shown that heat transfer is enhanced and shear stress is increased as the particle volume concentration increases. The heat transfer improves, as Reynolds number increases.
루프 환기구에 따른 보일러빌딩 내부 환기성능에 관한 수치적 연구
최훈기 ( Hoon Ki Choi ),유근종 ( Geun Jong Yoo ),이상헌 ( Sang Heon Lee ) 한국산업보건학회 (구 한국산업위생학회) 2016 한국산업보건학회지 Vol.26 No.3
Objectives: The objective of this paper is to find flow and heat transfer characteristics numerically in boiler buildings for three different ventilation window configurations. Methods: Turbulent natural convection flow in boiler buildings with a constant heating wall temperature was analyzed numerically . Governing equations were solved with standard finite-volume method using the SIMPLE algorithm. Conclusions: Flow and heat transfer characteristics are found for three different ventilation types. In the lower area under furnace, velocity and temperature distributions show similar patterns among the three different ventilation types. In the upper area over furnace, however, air flow is well mixed with lower peak temperatures for types B and C, which have roof ventilation windows, compared to type A which has side wall louvers only. Also, type B, with a single large roof window, shows better ventilation effect than does type C with its distribution roof windows.
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.
바디포오스가 큰 유동에서 운동량보간법의 사용에 관한 연구
최석기(Seok-Ki Choi),김성오(Seong-O Kim),최훈기(Hoon-Ki Choi) 한국전산유체공학회 2002 한국전산유체공학회지 Vol.7 No.2
A numerical study on the use of the momentum interpolation method for flows with a large body force is presented. The inherent problems of the momentum interpolation method are discussed first. The origins of problems of the momentum interpolation methods are the validity of linear assumptions employed for the evaluation of the cell-face velocities, the enforcement of mass conservation for the cell-centered velocities and the specification of pressure and pressure correction at the boundary. Numerical experiments are performed for a typical flow involving a large body force. The numerical results are compared with those by the staggered grid method. The fact that the momentum interpolation method may result in physically unrealistic solutions is demonstrated. Numerical experiments changing the numerical grid have shown that a simple way of removing the physically unrealistic solution is a proper grid refinement where there is a large pressure gradient. An effective way of specifying the pressure and pressure correction at the boundary by a local mass conservation near the boundary is proposed, and it is shown that this method can effectively remove the inherent problem of the specification of pressure and pressure correction at the boundary when one uses the momentum interpolation method.