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평활관 및 마이크로핀관 내 초임계 이산화탄소의 냉각열전달 특성
이대훈(Daehun Lee),전민주(Minjoo Jeon),손창효(Changhyo Son),오후규(Hookyu Oh) 대한설비공학회 2010 대한설비공학회 학술발표대회논문집 Vol.2010 No.6
The cooling heat transfer characteristics of supercritical CO₂ in smooth and micro-fin tubes were investigated experimentally. The main components of the refrigerant loop are a receiver, a CO₂ compressor, a mass flow meter, an evaporator and a micro-fin tube as a test section. The test was conducted at mass flux from 1200 to 2000 ㎏/㎡s, inlet cooling pressure from 9 to 10 ㎫. The cooling heat transfer coefficients of the micro-fin tube are about 12~39% higher than those of the smooth tube. In comparison with test results and existing correlations, correlations failed to predict the cooling heat transfer coefficient of CO₂ in the micro-fin tube. Therefore, it is necessary to develop reliable and accurate predictions determining the cooling heat transfer coefficient of CO₂ in the micro-fin tube.
이대훈(Daehun Lee),박상신(Sang-Shin Park),고태조(Tae Jo Ko),심재술(Jaesool Shim) 한국기계가공학회 2017 한국기계가공학회지 Vol.16 No.2
Friction occurs when surfaces that are in contact move relatively between solid surfaces, fluid layers, and materials slide against one another. This friction force causes wear on the contact surface, generates unwanted heat and leads to performance degradation. Thus, much research has been performed to avoid friction reduction. Among these studies, a textured surface that has micro patterns on the surface has drawn attention for its ability to reduce friction. A mathematical model is developed in this study to examine friction reduction due to the texture of a surface. Numerical simulations are carried out with respect to various factors such as the shape aspect ratio and texture depth of a diamond-shaped texture in the hydrodynamic lubrication regime. As a result, a shape aspect ratio of 1 is best for friction reduction.
1.2kW 급 BLDC 모터의 열 발산 측정 시스템 개발
이인준(Injun Lee),예정우(Jungwoo Ye),이대훈(Daehun Lee),황평(Pyung Hwang),심재술(Jaesool Shim) 대한기계학회 2013 大韓機械學會論文集A Vol.37 No.11
본 논문은 1.2㎾ 급 BLDC 모터의 분석을 위하여 열 발산 측정 시스템을 제작하였다. 온도증가는 모터절연체의 문제를 일으켜 모터 수명과 연결되므로 모터의 온도를 아는 것은 중요하다. 실험에서 모터의 부하를 설정하기 위해 자동차용 제너레이터를 장착하였고, 부하의 변경을 위해 165W~495W 를 변화를 주었다. 다양한 부하조건하에 분당 모터 회전 수를 2000 ~ 4000 까지 변경하면서 모터 각 부분에 열전대로 시간에 따른 온도변화를 측정하였다. 실험 결과로서 자연대류조건하에서는 모터의 회전 수 및 부하가 증가할수록 온도는 수렴하지 않으며 모터코일의 온도가 최고 120 ℃ 이상까지 증가하였으나, 강제 대류조건하에서는 4000s 이상에서 84 ℃에 수렴하였다. 모터의 최대/최소 온도 차이는 회전 수 및 부하가 증가할수록 최소 10 ℃~26 ℃의 차이를 보였다. 온도의 분포는 모터코일(1 번채널), 모터외부옆면(5 번채널), 모터내부 캡(2 번채널), 모터외부상부(4 번채널), 모터내부벽면(3 번채널)순으로 나타났다. In this study, a heat dissipation measurement system is developed to analyze a 1.2-㎾ BLDC motor. It is important to check the temperature of the motor because an increase in temperature causes problems in the motor insulations, which in turn influences the motor life. A generator for a vehicle is installed to set up a load. We changed the load from 165 to 495 W. While the rpm varies from 2000 to 4000 under various load conditions, the changes in temperature were measured for the operating period by using a thermocouple. The results of experiments conducted under natural convection conditions suggest that the temperature was not stationary with the rpm, load, and coil of the motor and it kept increasing over 120 ℃. However, under forced convection conditions, the temperature stationarily reached 84 ℃ after 4000 s. The difference between the maximum and the minimum temperatures was 10?26 ℃ with an increase in the rpm and load. The orders of high temperature were as follows: motor coil (Ch#1), side of motor surface (Ch#5), inside of motor cap (Ch#2), upper side of motor surface (Ch#4), and inner wall of the motor (Ch#3).
황태원(Taewon Hwang),국재호(Jaeho Kuk),이대훈(Daehun Lee),조주연(Juyeon Cho),김준형(Junhyeong Kim),허은균(Eungyun Heo),황선영(Sunyoung Hwang),이민기(Minki Lee),한성주(Sungju Han),장원석(Wonseok Chang),박기영(Giyoung Park),이성욱(Seangwo 한국자동차공학회 2018 한국자동차공학회 부문종합 학술대회 Vol.2018 No.6
In this paper, we deal with a monocoque body, carbon wheel and engine mapping for student formula vehicle. In the case of monocoque body, it was designed and manufactured based on torsional stiffness. By the torsional stiffness test, it is possible to make the monocoque body lighter than the steel tube frame structure and higher in torsional stiffness. Also in order to reduce the rotational inertia of the drive system, the existing aluminum wheels were replaced with the carbon wheels directly designed and made. We have developed a design with a higher lateral stiffness and a lighter weight than aluminum wheels and validated by lateral stiffness test using natural frequency. We are proceeding with mapping using 250cc engine and aftermarket ECU, and we optimized mapping using optimization program. As a result, we were able to shorten the time and create a more complete map.