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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.
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,김욱,김사량,차철현,Hur, Nahm-Keon,Kim, Wook,Kim, Sa-Ryang,Cha, Chul-Hyun 대한설비공학회 2001 설비공학 논문집 Vol.13 No.6
In the present study, the transient axi-symmetric numerical simulation of traffic ventilation induced by a train running through a 15.6km-long tunnel is performed by using over 100,000 computational cells. With train running, three cases of ventilation schemes are simulated, which are the case of ventilation fans turned on, the case of no fan but ventilation shafts open, and the case of no fan and no shaft. Results of the ventilation flow rate are pressure transients are compared for the cases considered.
Numerical flow analyses of a two-phase hydraulic coupling
허남건,곽민희,M. Moshfeghi,Choon-Soo Chang,N.-W. Kang 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.5
We investigated flow characteristics in a hydraulic coupling at different charged water conditions and speed ratios. Hence, simulations were performed for three-dimensional two-phase flow by using the VOF method. The realizable k-ε turbulence model was adopted. To resolve the interaction of passing blades of the primary and secondary wheels, simulations were conducted in the unsteady framework using a sliding grid technique. The results show that the water-air distribution inside the wheel is strongly dependent upon both amount of charged water and speed ratio. Generally, air is accumulated in the center of the wheel, forming a toroidal shape wrapped by the circulating water. The results also show that at high speed ratios, the solid-body-like rotation causes dry areas on the periphery of the wheels and, hence, considerably decreases the circulating flow rate and the transmitted torque. Furthermore, the momentum transfer was investigated through the concept of a mass flux triangle based on the local velocity multiplied by the local mixture density instead of the velocity triangle commonly used in a single-phase turbomachine analysis. Also, the mass fluxes along the radius of the coupling in the partially charged and fully charged cases were found to be completely different. It is shown that the flow rate at the interfacial plane and also the transmitted torque are closely related and are strongly dependent upon both the amount of charged water and speed ratio. Finally, a conceptual categorization together with two comprehensive maps was provided for the torque transmission and also circulating flow rates. These two maps in turn exhibit valuable engineering information and can serve as bases for an optimal design of a hydraulic coupling.