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허남건,원찬식,Hur, Nahm-Keon,Won, Chan-Shik 한국유체기계학회 1999 한국유체기계학회 논문집 Vol.2 No.1
Transient flow inside a hollow shaft of a Gas Turbine engine during sudden engine stop may result in non uniform heat transfer coefficients in the shaft due to flow instability similar to steady Taylor vortex, which may decrease the lifetime of the shaft. In the present study, transient Taylor vortex phenomena inside a suddenly stopped hollow shaft are studied analytically. Flow visualization is also performed to study the shape and onset time of Taylor Vortices for various initial rotational speed.
허남건,이명성,양성진 대한설비공학회 2011 International Journal Of Air-Conditioning and Refr Vol.19 No.4
Haeinsa temple is famous for over 80 000 wooden printing blocks of Buddhist scriptures called Tripitaka Koreana and its storage halls, both of which have been registered as the world cultural heritages by UNESCO. The objective of the present paper is to investigate the ventilation flow in the storage halls of Tripitaka Koreana in the case of building rearrangement in Haeinsa temple. Three-dimensional flow simulations were performed with the detailed geometry of all buildings in the temple. The slatted windows on walls of the storage halls and Tripitaka Koreana stored in the shelves inside the storage halls were modeled in detail to predict reliable ventilation performance. A tree canopy model was also adopted to take into account of the effect of the forest surrounding the temple. Wind velocities as inlet boundary condition were imposed from meteorological statistical data. The numerical results were obtained for the effects of the wind direction, wind speed and tree canopy model on the ventilation performance of the storage halls. It was shown from the numerical results that the ventilation flow distribution at the storage halls in the case of building rearrangement would not be significantly altered compared to that before rearrangement.
원자로 냉각재 펌프의 과도 상태의 유동 및 열전달 해석 연구
허남건,김성원,유기풍,김승태,Hur, N.,Kim, S.,Yoo, K.-P.,Kim, S. T. 한국유체기계학회 2000 한국유체기계학회 논문집 Vol.3 No.2
The structural analysis of a reactor coolant pump(RCP) of a nuclear power plant is very important for the safety assessment of the plant. Accurate boundary conditions for the heat transfer coefficient are required for reliable thermal stress analysis of the pump casing, especially in transient operations of the pump since the coolant properties are largely dependent on operational conditions. In the present study, a 3D mixed flow type coolant pump was modeled from the RCP drawings and analyzed in the steady state and number of transient flow conditions by using a commercial code STAR-CD. From the result of the computation, it is seen that the average heat transfer coefficients for the cases considered are found to be the suggested values of the manufacturer, Westinghouse Energy System. The unevenness in local heat transfer coefficients, however, is found to be considerable so that the use of average heat transfer coefficients in all boundaries might not give reliable thermal stress predictions.
허남건,조원국,윤성영,윤성영,김광호 대한기계학회 1993 대한기계학회논문집 Vol.17 No.6
A numerical simulation is carried out on flows in a rotating serpentine flow passage, which models a cooling passage in a gas turbine blade, by using a 3-D FVM based TURBO-D program. When it is rotating, the flow field exhibits quite different aspects due to the effect of the Coriolis force. Especially the secondary flow field appearing in the cross-sectional area is very complex because of the combined effect of the Coriolis force and the centrifugal force in the curved area. Local Nusselt numbers are also obtained based on the Reynolds analogy and compared with the published experimental data showing a good agreement. The results of the present study can be applied to the design of cooling passages of a gas turbine blade. 본 연구에서는 모델 냉각통로 내에 대한 유동장 및 열전달 계수분포를 구하기 위하여 수치적 방법에 의한 접근을 시도하였고 이를 위하여 본 연구실에서 개발한 유한체적법 유동해석 프로그램인 TURBO-3D를 사용하였다. 계산 영역은 터빈날개 내의 냉각유로를 단순화한 ㄹ자 형태의 유로를 설정하였으며 등온상태의 유동에 대하여 해를 구하였다.실제 고온의 터빈날개내에서는 큰 온도구배에 의한 강한 부력효과가 예상되어 이를 무시할 수는 없으나 등온 가정하의 유동장으로부터 Reynolds analogy 에 의한 열전달특성의 유추가 가능하다. 그러므로, 본 연구에서는 특히 회전수의 변화에 따른 Coriolis효과의 변화 및 2차 유동의 구조를 파악하였고 또한 이들에 의한 주 유동장과 압력분포 및 국부 열전달 특성을 파악하였다.
일반 비직교좌표계를 사용하는 3차원 범용 유동해석 프로그램의 개발
허남건,조원국,김광호 대한기계학회 1994 대한기계학회논문집 Vol.18 No.12
A general purpose program, TURBO-3D, for the analysis of 3-D fluid flow in complex geometry has been developed, which employs a standard $k-\varepsilon$ turbulence model and a general nonorthogonal grid system. For the purpose of verification of the program and testing the applicability, turbulent flows in an S-shaped diffuser and turbulent flows over an backward facing step are solved and compared with the earlier results. Comparison with the results by the STAR-CD program has been also made for the same flow configuration and grid structure. The agreements are excellent and hence the program has been verified. Since the present program is applicable only on limited flow phenomena and lacks the pre-and post processor, further improvements toward these directions are being made.
직교류 홴의 유동 해석: 깃 형상 변화가 성능에 미치는 영향
허남건,김욱,강신형,Hur, Nahm-Keon,Kim, Wook,Kang, Shin-Hyoung 한국유체기계학회 1999 한국유체기계학회 논문집 Vol.2 No.1
Cross flow fans are used in various applications, especially in industrial ventilation applications and in room air conditioners, due to their superior performance characteristics. Unlike radial and/or axial fans, the design of cross flow fans have been mostly based on earlier experiences and experiments. In the present study, numerical computations of flow fields through a cross flow fan used in room air conditioner are performed to investigate the detailed flow fields and to study the effect of the blade shape on performance curves to aid better design of the fan. Despite some discrepancies between the two results, it is seen from the present study that the computational results agree quite well with the qualitative experimental results. It is also shown from the present study that by having a different shape of blade, it is possible to achieve about $15\%$ increase in flow rates. The stimulating results of the present study can be used in the design of high performance cross flow fans with the use of optimal design algorithm and experimental verifications.