• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.1920-1925
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• 2007

A transformer is a device that changes the current and voltage by electricity induced between coil and core steel, and it is composed of metals and insulating materials. In the core of the transformer, the thermal load is generated by electric loss and the high temperature can make the break of insulating. So we must cool down the temperature of transformer by external radiators. According to cooling fan's usage, there are two cooling types, OA(Oil Natural Air Natural) and FA(Oil Natural Air Forced). For this study, we used Fluent 6.2 and analyzed the cooling characteristic of radiator. we calculated 1-fin of detail modeling that is similar to honeycomb structure and multi-fin(18-fin) calculation for OA and FA types. For the sensitivity study, we have different positions(side, under) of cooling fans for forced convection of FA type. The calculation results were compared with the measurement data which obtained from 135.45/69kV ultra transformer flowrate and temperature test. The aim of the study is to assess the Fluent code prediction on the radiator calculation and to use the data for optimizing transformer radiator design.

• 한국항해항만학회지
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• 제35권9호
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• pp.749-753
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• 2011

A leisure ship has a stand-alone type power system, and a generator is in use on this condition. But the generator cannot be operated in condition of leisure activity, ocean measurement and etc, because of environment and noise. Recently, renewable energy system is connected with power system of the leisure-ship for saving energy. The renewable energy system can not supply the stable power to leisure-ship because power generation changes according to weather condition. And most of the leisure ship is operated without methodical power management system. This study's purpose is to develop SPMS(Smart Power Management System) algorithm using the renewable energy (photovoltaic, wind power and etc.). The proposed algorithm is able to supply stable the power according to operation mode. Furthermore, the SPMS manages electric load (sailing and communication equipment, TV, fan, etc.) and reduces operating times of the generator. In this paper, the proposed algorithm is realized and executed by using LabVIEW. As a result, the hour for operating the generator is minimized.

• 설비공학논문집
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• 제15권12호
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• pp.1049-1059
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• 2003

R410A is considered as an alternative refrigerant to R22 for air conditioners. An experimental investigation was made to study the characteristics of the heat transfer and pressure drop for R410A flowing in a fin-and-tube heat exchanger used for commercial air-conditioning units. Experiments were carried out under the conditions of inlet refrigerant temperature of 6$0^{\circ}C$ and refrigerant mass flux varying from 150 to 250 kg/$m^2$s for refrigerant side. The inlet air has dry bulb temperature of 35$^{\circ}C$, relative humidity of 40% and air velocity varying from 0.68 to 1.6 m/s. Experiments show that air velocity decreased by 16% is needed for R410A than that of R22 for subcooling temperature of 5$^{\circ}C$, which resulted in air-side pressure drop decrease of 15% for R410A as compared to R22. As a consequence, in order to provide the same design condition of a condenser, the fan requires lower electric-power consumption with R410A than that with R22.

• 한국유체기계학회 논문집
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• 제19권6호
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• pp.5-13
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• 2016

Three-dimensional unsteady numerical analysis has been performed to observe aerodynamic characteristics of a H-rotor. Generally, the structure of the H-rotor is simple but the aerodynamic characteristics are exceptionably complicated since the angle of attacks and incident velocities to a blade are considerably varied according to the azimuth angles and solidities. The blade in the upwind revolution between 0 to 180 degree obtains aerodynamic energy from the free stream but the blade in the downwind revolution between 180 to 360 degree does not. When the rotating speed increases, the blade in the downwind revolution accelerates the air around the blade like a fan and it consumes the energy and shows negative torque in the area. On the other hand, the direction of the free stream is bent because of the interaction between blade the free stream. Therefore, the operation point (highest power coefficient) appears at a lower tip-speed-ratio what it is expected.

• 조명전기설비학회논문지
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• 제21권5호
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• pp.99-105
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• 2007

본 논문에서는 초 중 고등학교 전기시설물을 대상으로 전기안전에 대한 현장조사를 하였다. 현장조사는 수전설비, 교실, 과학실 및 음악실 등을 대상으로 연구원, 경력 15년 이상의 전기기술자 및 기타 관련 전문가에 의해 전국적으로 수행하였다. 41개 학교를 대상으로 현장조사를 실시한 결과, 수전설비의 접지방식은 공통접지방식이 지배적이었다. 위험요소로는 선풍기 조절기함의 부재, 실험대 전원의 인체보호용 누전차단기의 미설치, 비접지 콘센트의 사용 등으로 나타났다.

• 한국자동차공학회논문집
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• 제16권2호
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• pp.136-142
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• 2008

Thermal management of a junction box of a passenger car has recently become more challenging due to its smaller size and larger current capacity. Thus, it is essential to perform the thermal optimization of a junction box in its design on an early stage of vehicle design. In this study, 3 dimensional CFD simulation with experimental measurement has been done to study for better thermal management of the junction box. First, the study of thermal characteristics of electric relays in the junction box has revealed that each surface of the relay has very different thermal resistance. In addition, an idea to install a cooling fan on the junction box has been studied and it was found that the forced cooling method was not effective on the system to keep the thermal resistance to the reasonable level of the junction box. Finally, the effect of external flows around the junction box on the temperatures of the relays, fuses, etc. has been studied and the result shows that the installation of the junction box at the proper place in an engine room can avoid any unnecessary overdesign in thermal management.

• 한국작물학회지
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• 제26권3호
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• pp.219-225
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• 1981

Strong wind of 6.5m/s from electric fan was applied to rice at heading stage to find out the nature of wind damage to panicle. Damaged panicles caused by typhoon were sampled out of field to measure the yield and milling components. Wind-treated glumes were developed into two forms, fertile and sterile, and each of them showed all degree of glume discoloration. The number of fertile grains were higher than sterile grains in a damaged panicle. Averagesdegree of glume discoloration was higher in not flowered glume than in flowered glume. The more recently flowered glumes resulted the higher degree of discoloration among flowered glume. The percent of sterile grain to total number of grains was the highest at stage of just flowering. The glume discoloration representing wind damage at heading state advanced in degree in ten days after treatment compared to that just after treatment. Grain length and grain width were decreased with the increased degree of glume discoloration, while grain thickness was not changed greatly. Chalkiness was a little higher in damaged grain than in normal grain without definite trends by degree of discoloration. Ripening ratio, 1000 grain weight and yield decreased with increased degree of glume discoloration in damaged panicle by typhoon. Decreasing order in yield was white rice, rough rice and brown rice. Ratio of brown rice to rough rice increased, white rice to brown rice decreased, and milling recovery was not changed greatly with increased degree of 히ume discoloration.

• 대한가정학회지
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• 제35권5호
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• pp.239-248
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• 1997

to design nature-affinitive, reasonable and effcient thermal environment plannings and facilities, the holding patterns of heating-cooling facilities·accessory devices and residents' evaluation in Cheju Province were surveyed as well as residents' understanding for them. Major findings of this study are summarized as follows: 1) In the cooling system, the percentage of air-conditioner possessor was 19.4%, which was lower possessive rate than mainland's. The location of air-conditioner was mainly public area. That is, 55.3% of the location is livingroom, and the rest was Anbang. the general cooling accessory device was a fan. It was frequently used at the children's room and the dining room. The possessive patterns of air-conditioner depend on the characteristics of residents, such as the academic carrier and the average monthly income. Characteristics of house for air-conditioner possess depend on the location, house type, the size of floor space. 2) In the heating system, individual heating system reached to 57.3%. Heating accessory devices were oil stove and electric heating blanket. Only 32.2% of survey population were holders. 3) Residents preferred better ventilated room arrangement, which was characteristic of subtropical areas. 4) The preferred condition for heating-cooling facilities and accessory devices were strong solidity, less air pollution, and less noise.

• Journal of Power Electronics
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• 제13권4호
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• pp.546-551
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• 2013

This paper deals with the optimum design of the stator and rotor shape of the interior permanent magnet synchronous motors (IPMSM) that are used in applications for automobiles. IPMSMs have the following advantages: high power, high torque, high efficiency, etc. However, cogging torque which causes noise and vibrations is generated at the same time. The optimum design of shape of a IPMSM was carried out with the aim of reducing cogging torque. Six variables which affect to the performance of a IPMSM are chosen. The main effect variables were determined and applied to the response surface methodology (RSM). When compared to the initial model using the finite elements method (FEM), the optimum model highly reduces the cogging torque and improves the total harmonics distortion (THD) of the back-electro motive force (EMF). A prototype of the designed model was manufactured and experimented on to verify the feasibility of the IPMSM.

• 설비공학논문집
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• 제25권12호
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• pp.641-646
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• 2013

The purpose of this study is to improve the cooling performance of single and cascade refrigeration systems using thermoelectric modules. The system consists of a heat sink, fan, and thermoelectric module. The operating parameters considered in this study include power distribution between the first- and second-stage thermoelectric modules, air flow, and variable condensing unit. The cooling capacity increased with decreases in the temperature difference between hot and cold surfaces, but decreased with increases in the condensing temperature. The COP decreased with increasing electric power of the thermoelectric module because of the increased Joule heat. The cooling performance improvement using the thermoelectric module is represented by the freezer temperature.