• 동력기계공학회지
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• 제21권3호
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• pp.85-92
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• 2017

Global air traffic is forecast to grow at an average annual rate of around 5% in the next 20 years. The continuous growth of air traffic and raised environmental awareness put increasing pressure on aero engine manufacturers to reduce fuel burn and emissions. NEWAC are a new integrated program of the European Union with focus on innovative core engine concepts to achieve this problem. In this paper, Within NEWAC, active core engine configurations will be investigated. the investigation is focused on the optimal design of the CAC heat exchanger for active core. For optimal design of he CAC heat exchanger, the HTFS of basic design of heat exchanger are analyzed so as to proceed an optimization routines based on Response Surface Method(RSM) and Design of Experiment(DOE). As a result, CAC heat exchanger optimized by 1.0314 lb/s mass flow rate and 3.9058 mm TP of tube layout and 206.8181 mm height of heat exchanger and 918 tube number for heat transfer and pressure drop. We confirm the design optimization using RSM and DOE is useful on complex structure of heat exchanger.

• 한국자기학회지
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• 제15권1호
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• pp.48-52
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• 2005

본 연구는 미래의 가정에 설치되 전자식 전력량계의 정밀 전류측정용 센서 개발에 관한 내용이다. 전류센서는 공심코어 원리를 사용하기 때문에 일반 변류기(current transformer)의 자기포화와 비선형 오차의 한계 영향이 적다. 개발된 센서는 저전류 범위에서 선형도의 개선과 함께 공심코어를 사용하므로 제작이 간단한 장점을 가지고 있다. FEM solver 를 사용하여 자기장 해석을 하였으며 실제 측정된 값과 계산에 의한 값을 비교하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 A
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• pp.181-183
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• 1996

A novel model of an inductive superconducting fault current limiter with an inductive superconducting fault current limiter with the air-gap core was fabricated and tested. If its impedance is not high enough to limit the fault current, then destructive damage occurs in the power system. We attained a magnetic saturation under higher current by an effective air gap introduced in the core. The fault current was successfully limited to two times as much as the nominal current at a 60 Hz source having an effective voltage of 70 V. The fault current flowing under such conditions can be limited to a desired value without any fault current peak within 1/4 cycles.

• Nuclear Engineering and Technology
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• 제55권5호
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• pp.1604-1615
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• 2023

In an open-pool type research reactor with a downward forced flow in the core, pipes can be under sub-atmospheric pressure because of the large pressure drop at the reactor core in the atmospheric pool. Sub-atmospheric pressure can result in air inflow into the pipe from the pressure difference between the atmosphere and the inside of the pipe, which in a postulated pipe break scenario can lead to the breakdown of the cooling pump. In this study, a plant-scale experiment was conducted to study air inflow in large piping systems by considering the actual operational conditions of an advanced research reactor. The air inflow rate was measured, and the entrained air was visualized to investigate the behavior of air inflow and flow regime depending on the pipe break size. In addition, the developed drift-flux model for a large vertical pipe with a diameter of 600 mm was compared with other correlations. The flow regime transition in a large vertical pipe under downward flow was also studied using the newly developed drift-flux model. Consequently, the characteristics of two-phase flow in a large vertical pipe were found to differ from those in small vertical pipes where liquid recirculation was not dominant.

• 한국정보과학회논문지:시스템및이론
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• 제32권6호
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• pp.314-323
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• 2005

본 논문은 전장지역에서 벌어지는 공중작전에 대한 상황의 자료를 통합하여 3차원으로 가시화 함으로써 공중작전의 최고결정권자가 올바른 상황인식 및 지휘결정을 할 수 있게 지원하는 시스템을 제안한다. 공중작전 상황판단을 위한 다양한 자료들, 레이더 항적정보, 비행계획 데이타베이스, 지도 및 위성사진 정보 둥을 하나의 자료로 통합하여 3차원으로 가시화 시킴으로써, 작전의 최고 결정권자가 한 순간에 종합적인 작전 결정을 할 수 있는 정보를 지원하는 시스템이다. 대량의 데이타를 종합적이고 체계적으로 가시화 하기 위하여 Out-of-Core 방법을 사용함으로써 휴대용 노트북에서도 운용이 가능함을 실험을 통하여 보여 주고 있으며, 공군의 공중작전 수행 시 상황인식을 지원하는 시스템으로 활용될 수 있는 가능성을 보이고 있다.

• 설비공학논문집
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• 제24권3호
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• pp.224-229
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• 2012

The importance of ventilation system is being emphasized by interest of indoor air quality. Especially, heat recovery ventilation system has attracted attention as most effective ventilation plan. Because it can reduce hazardous construction materials, indoor air pollutions, and also can reduce air conditioning energy cost. In heat recovery ventilator, the element core is the most important part. The element core is composed of liner and spacer. And liner and spacer are stacked alternately. On the Liner, heat and humidity transfer are made between supply and exhaust air. And spacer plays a role as a tunnel of exhaust and supply. In this study, we investigated and analyzed the efficiency of a heat recovery ventilator, when the spacer's properties are changed. As a result, difference spacer's properties affect an efficiency of heat recovery ventilator.

• 전력전자학회논문지
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• 제20권3호
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• pp.262-272
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• 2015

An integrated two-in-one transformer applicable to PSUs for a 120 W LED TV is proposed. This transformer comprises a PFC inductor and an LLC transformer placed and integrated on an E-I-E type magnetic core. Performance is evaluated by observing the coupling coefficients of the proposed two-in-one transformer under various air gap topologies. Among the topologies studied, an integrated transformer with centered air gap shows stable operational characteristics with a minimized mutual coupling (interference). Furthermore, applicability of the proposed integrated transformer to PSUs for a 120 W LED TV is studied from the viewpoint of integrating different magnetic components into one core, resulting to low weight, low cost, and high power density.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 추계학술대회논문집
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• pp.188-192
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• 2004

The purpose of this study is to develop an air spring mount that has high damping characteristic. The new type air spring mount has a polyurethane core in the center. By adding the core, the air spring mount shows excellent damping effect and good resistance to lateral force. This study includes both the analytical study and the experimental study of the new type air spring mount.

• Journal of Advanced Marine Engineering and Technology
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• 제27권7호
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• pp.879-888
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• 2003

Swirling air flow in a horizontal round tube was experimentally studied for its visualization. The present investigation deals with swirl angle, flow visualization studies and accompanying vortex core behavior by using oil smoke and a hot wire anemometer for Re = 40,000 and 50000 at X/D = 41, 59 and 71. In the swirl air flow, a vortex core was formed at high swirl intensity along the test tube. The swirl angle and the vortex core depended on the swirl intensity along the test tube. The results of swirl angles measured by flow visualization and hot wire reasonably agree with those of previous studies.

• 한국초전도ㆍ저온공학회논문지
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• 제14권4호
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• pp.36-40
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• 2012

This paper presents an experimental and numerical study on current limiting characteristics of a fault current controller (FCC). The FCC consists of an AC/DC power converter, a superconducting coil, and a control unit. Even though some previous researches proved that the FCC could adjust the fault current level, the current limiting characteristics by the superconducting coil should be investigated for design of the coil. In this paper, four kinds of model coils were tested; 1) air core, 2) iron core without any bias, 3) reversely magnetized core (RMC) using permanent magnets, and 4) RMC using an electromagnet. Based on a comparative study, it is confirmed that a RMC by an electromagnet (EM) could increase the effective inductance of the coil. In this paper, a numerical code to simulate the HTS coil with RMC was developed. This code can be applied to design the HTS coil with active reversely magnetized bias coil.