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유동 방향으로 기울어진 사각 핀-휜 열교환기의 유동 및 열전달 특성에 대한 수치적 연구
서준호(J.H. Seo),김민성(M. Kim),하만영(M.Y. Ha),민준기(J.K. Min) 한국전산유체공학회 2016 한국전산유체공학회지 Vol.21 No.3
The flow and heat transfer characteristics of a heat exchanger having rectangular pin-fin in the flow direction have been investigated numerically. On the bottom plate, the convective boundary conditions for the hot side was given, and the fins were arranged in a channel-type geometric model using the periodic boundary condition in the span-wise direction. Three-dimensional numerical calculations for the flow and conjugate heat transfer problem were conducted using SIMPLE algorithm and k-ε turbulence model. For the slanted pin-fin models, it was found that the downward cooling flow is generated due to the downward pressure gradient component, which can enhance the heat transfer performance near the bottom surface and the fin stem region. Four different inclined angles were considered in the Reynolds number range of 13,500-55,000. The aero-thermal performance of the slanted pin-fin heat exchangers, such as the volume and area goodness factors, were summarized and compared with the baseline plate-fin type heat exchanger quantitatively.
전원전압의 불평형 및 왜곡에 강인한 3상 4선식 전력용 능동 필터의 설계
민준기(J.K. Min),최재호(J.H. Choi),김효성(H.S. Kim),김경환(K.H. Kim) 전력전자학회 2003 전력전자학술대회 논문집 Vol.2003 No.7(2)
Tins paper proposed a novel current control strategy on active power filters using p-q-r instantaneous power theory which can compensate the line current harmonics and the neutral line current in unbalanced and/or distorted source conditions m three-phase four-wire systems. The proposed current control method is based on a sinusoidal PWM for fully-digital implementation which was compared with a hysteresis PWM. Simulation results showed good performance of the proposed current control strategy on shunt type APFs<br/>
민준기(J.K. Min),최도형(D.H. Choi) 한국전산유체공학회 2000 한국전산유체공학회지 Vol.5 No.1
The LiBr-H₂O absorption process on a horizontal tube has been analyzed numerically. The flow field, which was calculated in the authors' previous study by solving the fully elliptic Navier-Stokes equations with accurate free-surface-tracking method, is used to solve the temperature and concentration distributions in the absorption film. With the assumption that the absorbent is linear, calculations have been made for various inlet temperature and flow-rate conditions. For low inlet temperature, the absorption rate is large in the upstream region but the mean temperature also increases and as a result the absorption decreases as the film flows to downstream while high-inlet-temperature case does the opposite. The difference in the absorption rate due to the inlet temperature change becomes smaller in the downstream than that in the upstream. For large flow rate, the heat transfer to the wall becomes poor due to the thick film and so does the absorption rate. The analyses have also been carried out for multiple tube arrangement and the results show that the absorption rate converges after a few tube rows.
민완기(Min W.K.),김남오(Kim N. O.),김병철(Kim B. C.),전형석(Chun H. S.),신석두(Shin S. D.),김형곤(Kim H. G.),민준기(Min J. K.),최재호(Choi J. H.) 대한전기학회 2008 대한전기학회 학술대회 논문집 Vol.2008 No.11
Neutral line current is analyzed by the neutral line CF in nonlinear load balanced and unbalanced conditions. The worst nonlinear load condition is nonlinear balanced load condition. and It is below CFNL=1.194 that a neutral line current could not excess the rated value