• 동력기계공학회지
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• 제9권4호
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• pp.11-17
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• 2005

This paper reports an experimental study on the performance evaluation of air-to-air heat exchanger with rotary type newly developed in this study. Air flow rate is varied from 10 to 120 m3/h. The range of RPM of the porous rotating discs mounted inside the heat exchanger unit is 0 to 50. The temperature of the return air side is set by adjusting heat supply at heater. The material of the porous rotating discs is cooper and its thickness is 1.0 mm. The heat transfer rate increased with the increase in air flow rate. It was found that the heat transfer rate, as the temperature of the return air side was increased, was improved due to higher temperature difference. The heat exchange performance increased with the increase in the temperature of the return air side at the conditions of the same RPM. The sensible heat exchange efficiency was maximum 68 to 76 percent, and enthalpy exchange efficiency 64 to 74 percent.

• 한국태양에너지학회 논문집
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• 제32권5호
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• pp.52-58
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• 2012

Experimental study was performed to understand the real operation conditions of a showcase working usually in a convenient store and discount store. The purpose of this study was to show the possibility for practical use of cold-heat storage systems being operated for the showcase. To do that, evaporator and condenser temperatures were measured and the compressor electric power consumption were measured simultaneously. To use the ice storage system, the ice making process was typically operated during midnight being not needed the cooling of the showcase through the continuous running of the condenser unit. And then, the refrigerant was subcooled using the stored cold-heat after being discharged from the condenser during daytime. So, the cooling performance was increased with the sub-cooling of refrigerant during daytime,hence the actual running time of the compressor could be effectively decreased. Through the experiments, this study showed that the compressor electric power consumption during daytime could be transferred to nighttime for applying the refrigerant sub-cooling. So, for the convenient store, the maximum load transfer rates for each working cooler and showcase were estimated about 31.1% and 19.9% respectively. And for the discount store, the maximum load transfer rates for each refrigeration and freezing showcase were estimated about 34.1% and 49.0% respectively.

• 전자공학회논문지
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• 제52권6호
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• pp.43-49
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• 2015

본 논문에서는 모바일 기기의 배터리 무선 충전을 위해 효율이 향상된 자기공진방식 무선전력전송 시스템을 제시한다. 전송 효율의 향상과 소형화를 위해 HFSS를 이용한 전자기 시뮬레이션을 통해 공진기 구조를 설계 및 제작하였다. 입력 임피던스와 출력 임피던스 차이에 의한 반사를 줄이기 위해 임피던스 매칭 네트워크를 적용하였다. 모바일 기기의 배터리 충전을 위해 $0.35{\mu}m$ BCD 공정을 이용하여 정류회로와 레귤레이터를 포함하는 전력수신 칩을 설계하였다. 무선전력전송 시스템 효율은 최대 75.1%를 보였으며 시스템 검증을 위한 실험에서 최대 70cm거리에서 상용화된 휴대폰 배터리(3.7V, 6.11Wh, 1680mAh)를 부하로 사용하여 충전을 확인하였다.

• 한국유체기계학회 논문집
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• 제10권3호
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• pp.17-24
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• 2007

This paper presents the design procedure of a vertical wind turbine named jet-wheel-turbo turbine and the numerical and experimental verifications. The design parameters such as the rotor inlet angle, the diameter-to-hub ratio, the inlet guide outlet angle and the solidity were optimized to maximize the energy transfer, and to further increase the turbine efficiency by applying the side guide vane and the side opening to the rotor. The maximum power coefficient of 0.59, which is much higher than the ever-designed three-bladed horizontal turbines, was experimentally obtained when the optimal inlet- and side-guide vanes were installed and both sides of the rotor were 80% opened. The maximum power coefficients occur at the tip speed ratio ranging between 0.6 and 0.7. This vertical-axis turbine model can be applied to the large-scale power generation system with the speed and torque control algorithm for the specified wind characteristics.

• Journal of Power Electronics
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• 제17권6호
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• pp.1694-1706
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• 2017

Models and experiments for magnetic resonance coupling wireless power transmission (MRC-WPT) topologies such as the chain topology and branch topology are studied in this paper. Coupling mode theory based energy resonance models are built for the two topologies. Complete energy resonance models including input items, loss coefficients, and coupling coefficients are built for the two topologies. The storage and the oscillation model of the resonant energy are built in the time domain. The effect of the excitation item, loss item, and coupling coefficients on MRC systems are provided in detail. By solving the energy oscillation time domain model, distance enhancing models are established for the chain topology, and energy relocating models are established for the branch topology. Under the assumption that there are no couplings between every other coil or between loads, the maximum transmission capacity conditions are found for the chain topology, and energy distribution models are established for the branch topology. A MRC-WPT experiment was carried out for the verification of the above model. The maximum transmission distance enhancement condition for the chain topology, and the energy allocation model for the branch topology were verified by experiments.

• 한국음향학회지
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• 제29권8호
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• pp.491-496
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• 2010

Rijke관에 놓인 나선형 가열기에 의하여 생성되는 열음향 파워를 수치해로 구하였다. 음장의 각진동수와 공기의 열확산계수에 의하여 무차원화한 가열선의 지름 d, 간격 P-d 및 유속 $U_0$가 음향 파워 생성에 미치는 영향을 구하고 고찰하였다. 가열선 간격이 충분히 클 때 무차원 유속이 $U_0{\approx}0.8$, 무차원 지름이 d.4일 때 가장 큰 열음향파워가 생성된다. 그러나 가열선 사이의 간격이 가까워지면 음향 파워 생성이 크게 증가하며 $d{\approx}2$, $P-d{\approx}3$에서 최대로 되며, 간격이 충분히 먼 경우의 최대값의 5배 이상이 될 수 있다. 최대 음향파워를 생성하는 유속은 가열선 간격에 관계없이 $U_0{\approx}0.8$일 때이다.

• 한국음향학회지
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• 제27권6호
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• pp.271-278
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• 2008

압전판의 길이나 폭에 따라 두께가 변화하는 압전 세라믹을 사용하여 광대역 특성을 구현하는 초음파 트랜스듀서에 대하여 압전진동자의 측면에서 본 형태에 따른 전기-음향적 특성해석을 이론적으로 수행하였다. 압전진동자의 길이방향에 따른 두께 변화를 지수함수의 조합으로 표현하고 이 함수를 이용하여 압전진동자의 전기단자에서 본 자유 어드미턴스 및 파워전달함수에 대한 식을 도출하였다. 대표적인 PZT압전 세라믹을 예로 들어 압전 진동자의 측면 형태변화에 따른 비 대역폭을 고찰해본 결과 넓은 대역폭를 얻기 위한 최적의 형태가 존재함을 알 수 있었으며, 압전진동자의 최대두께에 대한 최소두께 비가 자아짐에 따라 대역폭은 100%이상까지도 넓어질 수 있으나 파워전달함수는 반대로 감소하는 경향을 확인할 수 있었다. 또 압전진동자의 길이가 길어질수록 전달함수의 크기는 증가하나 광대역 특성을 갖는 압전진동자의 형태는 매우 한정적이 됨을 확인할 수 있었으며 이는 고효율의 광대역 초음파 트렌스듀서 제작에 있어서는 정밀한 가공이 요구됨을 확인할 수 있었다.

• 한국인터넷방송통신학회논문지
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• 제19권5호
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• pp.175-180
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• 2019

새로운 고유치 문제에 기초한 모드 전송선로 이론 (Modal Transmission-Line Theory: MTLT))을 이용하여 blazed 격자 구조형 방향성 결합기 (B-GADC)의 광학 특성과 채널사이의 전력전달을 자세하게 분석하였다. 설계한 B-GADC의 결함효율을 분석하기 위하여 격자주기와 파장에 따라 변하는 quasi-TE 모드와 quasi-TM 모드의 분산곡선을 수치 해석하였으며, blazing 특성이 GADC의 결합효율에 미치는 영향을 분석하기 위하여 대칭형, 톱니형 그리고 비대칭형 blazed 격자구조를 설계하고 평가하였다. 수치해석 결과, blazed 격자구조가 대칭형에서 비대칭형으로 변함에 따라 최대 전력전송을 위한 최소 간격 조건을 만족하는 격자주기는 줄어들었으며 결합길이는 반대로 늘어나는 것을 확인하였다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2016년도 전력전자학술대회 논문집
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• pp.349-350
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• 2016

In the magnetically coupled wireless power transmit (WPT), the study of the multi-dimensional transmission coil to solve the low power transmission efficiency from the location of transmit coil and receiving coil is being developed. This paper, an important step in this study, presents the magnetically coupled model of the WPT system consist of the two-dimensional transmit coil and verifies by the simulation and experiment. The induced model in this paper can be used to design the WPT circuit and controller for the maximum transmission efficiency.

• 대한전기학회논문지:전력기술부문A
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• 제49권6호
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• pp.298-304
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• 2000

In this paper, we propose that the SCOPF be solved in a decentralized framework, consisting of regions, using a price-based mechanism. We first solve the distributed OPF problem to determine the maximum secure simultaneous transfer capability of each tie-line between adjacent regions by taking only the security constraints imposed on the tie-lines into account. And then, the regional SCOPF is performed using the conventional LP approach. A description on the inclusion of security constraints with distributed OPF algorithm will be given, folowed by a case study for Korea power system.