• Title/Summary/Keyword: maximum power transfer

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Study on the Characteristics of Heat Transfer with Array of Multiple Impinging Jet Nozzle (충돌제트 노즐의 다중 배열 형상에 따른 열전달 특성)

  • Kim, D.K.;Son, J.D.
    • Journal of Power System Engineering
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    • v.10 no.3
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    • pp.32-37
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    • 2006
  • In this paper, we present the flow and heat transfer characteristics with the array of impinging jet nozzles by using the numerical computation and experiment. Numerical solutions were obtained for dimensionless gap H=6, dimensionless outlet length L=10 and Reynolds number Re=1500 by using the commercial CFD code, CFX-5. Experimental and numerical results were agreed well with each other. It was found that the impinging jet with circular array nozzles generated the uniform heat transfer area and the maximum heat transfer is higher than rectangular array nozzles for certain parameter sets. It is one of the most important utilities providing steam to turbine in order to supply mechanical energy in thermal power plant. It is composed of thousands of tubes for high efficient heat transfer.

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Numerical Study for Heat Transfer Characteristics Varying Cross-Sectional Shape of a Tube (관 단면형상 변화에 따른 열전달 특성에 관한 수치해석적 연구)

  • Park, Hun-Chae;Choi, Hang-Seok;Kim, Seock-Joon
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.24 no.7
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    • pp.560-566
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    • 2012
  • Numerical study has been carried out to investigate heat transfer and pressure drop characteristics for streamlined shape tubes. The flow and thermal fields are investigated with varying diameter ratio of the tube ranging from 0.4 to 2.5 and Reynolds number ranging from 10,000 to 30,000. The results show that heat transfer per unit fan power is maximum at $D_2/D_1=0.8$. Furthermore, the heat transfer per unit fan power of streamlined shape tubes was compared with circular tube. The heat transfer per unit fan power of streamlined shape tube was larger than that of circular tube.

Maximum Power Point Tracking Control for a Grid-Tie Photovoltaic Inverter (계통 연계형 태양광 인버터에서 최대 출력 점 추적 제어)

  • Lee, Woo-Cheol
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.23 no.5
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    • pp.72-79
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    • 2009
  • Solar energy is desirable due to its renewable and pollution-free properties. In order to utilize the present utility grid infrastructure for power transmission and distribution, a do-dc boost converter and grid connected dc-to-ac inverters are needed for solar power generation. The dc-dc boost converter allows the PV system to operate at high do-link voltage. The single-phase inverter provides the necessary voltage and frequency for interconnection to the grid. In this paper, first, current loop transfer function of a single-phase grid-tie inverter has been systematically derived Second the MPPT of conductance increment method at converter side is proposed to supply the maximum power to the inverter side. Simulation results are shown to access the performance of PV system and its behaviour at the interconnection point.

PSTCP : A Tool to Evaluate Power System Transfer Capability (전력계토의 수송능력 평가 프로그램 개발에 관한 연구)

  • Yu, Su-Hyeon;Jeong, Jong-Hun;Jeong, Min-Hwa;Lee, Byeong-Jun;Song, Gil-Yeong;Sin, Yeong-Cheol;Kim, Yeong-Seon
    • The Transactions of the Korean Institute of Electrical Engineers A
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    • v.48 no.7
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    • pp.872-880
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    • 1999
  • This paper presents an algorithm that can calculate the evaluation index of power system from the transfer capability point of view. The algorithm adopts a successive linear programming skill to solve an optimal solution. Two indices which are transfer margin index and economic matching index have been developed. Prior to calculating these indices, Maximum Load supplying Capability(MLSC) and Economic Load Supplying Capability(ELSC) are utilized as basic data. For man-machine interface, graphical user interface has been implemented so that an unified software package PSTCP(Power System Transfer Capability Program) has been developed. KEPCO systems planned up to 2006 year have been tested to show effectiveness and usefulness of the PSTCP for power system planning stages.

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Bidirectional Power Conversion of Isolated Switched-Capacitor Topology for Photovoltaic Differential Power Processors

  • Kim, Hyun-Woo;Park, Joung-Hu;Jeon, Hee-Jong
    • Journal of Power Electronics
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    • v.16 no.5
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    • pp.1629-1638
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    • 2016
  • Differential power processing (DPP) systems are among the most effective architectures for photovoltaic (PV) power systems because they are highly efficient as a result of their distributed local maximum power point tracking ability, which allows the fractional processing of the total generated power. However, DPP systems require a high-efficiency, high step-up/down bidirectional converter with broad operating ranges and galvanic isolation. This study proposes a single, magnetic, high-efficiency, high step-up/down bidirectional DC-DC converter. The proposed converter is composed of a bidirectional flyback and a bidirectional isolated switched-capacitor cell, which are competitively cheap. The output terminals of the flyback converter and switched-capacitor cell are connected in series to obtain the voltage step-up. In the reverse power flow, the converter reciprocally operates with high efficiency across a broad operating range because it uses hard switching instead of soft switching. The proposed topology achieves a genuine on-off interleaved energy transfer at the transformer core and windings, thus providing an excellent utilization ratio. The dynamic characteristics of the converter are analyzed for the controller design. Finally, a 240 W hardware prototype is constructed to demonstrate the operation of the bidirectional converter under a current feedback control loop. To improve the efficiency of a PV system, the maximum power point tracking method is applied to the proposed converter.

Analysis of a Heat Engine with the Irreversibility by the Heat Transfer (열전달 에 의한 비가역성 을 고려한 열기관 성능 해석)

  • 김성진;정평석;노승탁
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.8 no.6
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    • pp.564-568
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    • 1984
  • An analysis has been performed for the internally reversible heat engine with the finite heat transfer rate. In the heat engine operating between two fluid streams, there exist the optimum temperatures at which the engine has maximum power. The optimum values can be expressed in terms of the temperatures of the heat source and sink. The condition for the maximum power can be explained as the minimum entropy generation by the finite heat transfer rate.

Heat Transfer Augmentation on Flat Plate with Two-Dimensional Rods in Impinging Air Jet System[2]:Effect of rod pitch (충돌판(衝突板) 근방(近傍)에 배열(配列)된 2차원(次元) Rod가 충돌분류(衝突噴流) 열전달(熱傳達)에 미치는 영향(影響)[2]:Rod 피치변화(變化)에 대한 효과(效果))

  • Lee, Yong-Hwa;Seo, Jeong-Yun
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.1 no.2
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    • pp.182-189
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    • 1989
  • The propose of this study is augmentation of heat transfer without additional external power in 2-dimensional impinging air jet. The passive heat transfer augmentation method tried in this experimental study is placement of rod bundles with the clearance, 2mm, in front of the heat transfer surface. The effects of pitch distance among rods and nozzle-to-target plate distance are investigated. The overall heat transfer rate of flat plate with rods reaches maximum at H/B=10 and P=40mm, and for H/B=2 and P=40mm the augmentation rate of heat transfer becomes maximum to a value which is about 1.57 times that of the flat plate without rods.

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A Method of Prediction and Analysis of Electromagnetic Interference (EMI) in Wireless Power Transfer System Operating at 13.56 MHz (13.56 MHz 무선 에너지 전송 시스템의 효율적인 전자파 장해(EMI) 예측 및 분석 방법)

  • Shim, Hyun-Jin;Park, Jong-Min;Nam, Sangwook
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.24 no.9
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    • pp.873-882
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    • 2013
  • The effective way of estimation and analysis of EMI(Electromagnetic Interference) in Wireless Power Transfer System operating at 13.56 MHz is proposed. In this paper methodology of driving magnetic field strength and electric loop current of two antennas which are in free space and on PEC plane using image theory and duality is proposed. Perfect electric conductor(PEC) is planar, infinite in extent, and perfectly conducting plane. And we will refer it as PEC plane. A equivalent circuit model is used to analyze. Using this theoretical analysis, we can derive maximum magnetic field strength of the far-field region numerically using measured data of near-field maximum magnetic field strength. The experimental results using commercial numerical simulation tool are in agreement with the theoretical results. Also, using the derivation of maximum magnetic field strength in the far-field region, we can easily estimate the maximum allowable power dissipation that meets EMI regulations.

A Study on the Effect of Resonant Coil Size and Load Resistance on the Transmission Efficiency of Magnetic Resonance Wireless Power Transfer System (공진 코일의 크기와 부하 저항이 자계 공명 무선 전력 전송 장치의 전달 효율에 주는 영향에 관한 연구)

  • Park, Jeong-Heum
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.26 no.7
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    • pp.45-51
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    • 2012
  • In this paper, the wireless power transfer system using the magnetic resonance was designed and the effect of resonant coil radius and load resistance to this system was analyzed by the circuit analysis method. As a result, the calculated transmitted-power is similar to measured one, and the coil size has a small effect to the coupling coefficients in the resonant frequency band. In addition, the fact that the calculated transmitted-power according to the source frequency is similar to measured one confirms that the circuit analysis methode in this paper is valid. The input side transmission efficiency ${\eta}_i$ including only the loss in the power transfer circuit is almost 90[%] with the large coil in the 10[cm] transfer distance, and 65[%] with the small coil in 1[cm]. The source side transmission efficiency ${\eta}_s$ is 30~40[%] at both coil when load resistance below 4.7[${\Omega}$] has been connected. Considering that the maximum ${\eta}_s$ is 50[%], this is valid in the practical applications.

Maximum Power Output Condition of the Binary Power Cycle Composed of Two Carnot Cycles (이중 동력 사이클의 최대 출력 조건)

  • 김창욱;김수연;정평석
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.15 no.1
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    • pp.349-354
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    • 1991
  • The power output behavior of the binary cycle composed of two Carnot cycles is analyzed with considering heat transfer processes, in which the finitely constant temperature differences between heat sources and working fluids exists. The power output has the maximum value as an extremum for cycle temperatures and capacities of heat exchangers. In the internally reversible cycle, the power output is independent of the cycle temperature in the intermediate heat exchanger. In this case when the total capacities of heat exchangers are given, three heat exchangers have the same capacities at the maximum power output condition. In addition, when the cycle is not extremum for cycle temperatures and capacities of heat exchangers. At the maximum power output condition, the capacity of heat exchanger at the cold side is slightly more than the hot side as the cycle effectiveness decreases.