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Branching of two-phase flow from a vertical header to horizontal parallel channels
이준경 대한기계학회 2009 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.23 No.6
The objective of the present experimental work is to investigate the two-phase flow distribution from a vertical main to parallel horizontal branches. Both the main and the branches have rectangular cross-sections simulating the header and the channels of the compact heat exchangers for air-conditioning systems. The cross section of the main is 8 mm × 8 mm while that of the parallel branches is 8 mm × 1 mm. Here, the second (downstream) junction was taken as the reference. The effect of the distance between the branches was mainly examined by changing it from 9 mm to 49 mm for the given flow conditions at the inlet of the downstream junction. Air and water were used as the test fluids. The superficial velocity ranges of air and water at the test section inlet were 13.2 – 21.4 m/s and 0.08 – 0.28 m/s, respectively. When the branch spacing becomes smaller, the fraction of liquid separation through the downstream branch decreases. The trend remains the same over the entire range of the present experiment, i.e., for different values of quality and the mass flow rate at the inlet of the downstream junction. Based on the correlation for single T-junctions, a modified correlation was proposed to take into account the effect of the branch distance in predicting the fraction of liquid separation. The correlation represents the experimental results within the accuracy of ±15 %.
Optimum channel intrusion depth for uniform flow distribution at header-channel junctions
이준경 대한기계학회 2010 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.24 No.7
The ultimate goal of this work is to find the optimal condition for the even distribution of two-phase mixture at header-channel junctions simulating the corresponding parts of compact heat exchangers. The cross section of the header and the channels were 14 mm × 14mm and 12 mm × 1.6 mm, respectively. Two different distances between channels (10 and 21.6 mm) and four different intrusion depths (0, 1.75, 3.5 and 7 mm) beyond the inner wall of the header were tested for the mass flux and the mass quality ranges of 70 - 165 kg/m2s and 0.3 – 0.7, respectively. Air and water were used as the test fluids. The flow distribution pattern was relatively insensitive to the channel distance because the flow configuration inside the header remained almost unchanged. On the other hand, the distribution pattern was changed drastically with the intrusion depth of the channels. The optimum intrusion depth for even flow distribution was identified to be 1/8 of the hydraulic diameter of the header cross-section for the experimental conditions tested in the present work.
신경회로망을 이용한 UPFC가 연계된 송전선로의 거리계전기에 관한 연구
이준경,박정호,이승혁,김진오,Lee, Jun-Kyong,Park, Jeong-Ho,Lee, Seung-Hyuk,Kim, Jin-O 한국조명전기설비학회 2004 조명·전기설비학회논문지 Vol.18 No.6
전력계통분야의 복합 대형화에 유연한 대처와 전력조류의 최적화 도모를 위해 사용되는 FACTS(Flexible AC Transmission System)기기 중 가장 유용한 UPFC(Unified Power Flow Controller)는 선로의 전압을 임의의 크기와 위상을 갖도록 제어하여 선로로 전송되는 유ㆍ무효전력을 총체적으로 보상하는 기능을 갖는다. 이런 UPEC가 계통에 연계되어 운영된다면 송전선로 매개변수가 변하기 때문에 계통의 영향을 많이 받는 거리계전기는 불필요한 오동작이 발생하게 된다. 즉 거리계전기에서 바라본 임피던스 영역(Impedance Zone)이 송전선로에 UPFC 연계시 각각의 보상 값에 의해 상당한 변화를 보임으로, 기존의 방식으로 정정된 Relay Setting Zone과 Adaptive Setting Zone은 현저한 오차가 발생하게 된다. 그러므로 계통에 연계된 UPFC의 운전 조건을 고려한 거리계전기 보호구간의 재설정이 필요하게 된다. 따라서 본 논문의 목적은 학습이 가능한 신경회로망(ANN)을 이용하여 거리계전기 동작의 신속성(Speed)을 기본으로 전력계통의 다양한 환경에 대해 거리계전기 응동 특성을 향상시키는데 있다. 학습 방법으로는 정적 및 동적인 비선형 시스템의 인식과 다변수 시스템에 적용 가능한 역전파 알고리즘(Back-propagation Algorithm)을 사용했다. This paper represents a new approach for the protective relay of power transmission lines using a Artificial Neural Network(ANN). A different fault m transmission lines need to be detected classified and located accurately and cleared as fast as possible. However, The protection range of the distance relay is always designed on the basis of fixed settings, and unfortunately these approach do not have the ability to adapt dynamically to the system operating condition. ANN is suitable for the adaptive relaying and the detection of complex faults. The backpropagation algerian based multi-layer protection is utilized for the teaming process. It allows to make control to various protection functions. As expected, the simulation result demonstrate that this approach is useful and satisfactory.