• 제목/요약/키워드: minimum heat dissipation

검색결과 14건 처리시간 0.026초

일부 전류분류영역을 가짐으로서 최소 열손실을 갖는 초전도 전류도입선 (Minimum Heat Dissipation of HTS Current Lead Having Partial Current Sharing Region)

  • 설승윤;허광수
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2001년도 추계학술대회논문집B
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    • pp.131-136
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    • 2001
  • In this paper, a high-temperature superconductor(HTS) current lead operating in current sharing mode is described. The minimum heat dissipation and the optimum safety factor(cross-sectional area) is obtained analytically for partial current sharing HTS leads. It is assumed that the current lead is in conduction cooled state, and the sheath material is the alloy of silver and gold. The reduced cross-sectional area results partial current sharing state, and consequently reduces conduction heat transfer, but the Joule heat generation is increased. The optimized HTS current lead is different from the conventional copper leads. In the copper leads, the minimum heat dissipation is obtained for the zero gradient of temperature at warm end. However, the temperature gradient at warm end is not zero when the HTS lead operates at minimum dissipation state.

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자연대류를 고려한 초전도 전류도입선의 최적 설계 (Optimal design of HTS current lead considering natural convection)

  • 손봉준;설승윤
    • 한국초전도저온공학회:학술대회논문집
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    • 한국초전도저온공학회 2003년도 추계학술대회 논문집
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    • pp.269-273
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    • 2003
  • In this paper the HTS current lead for superconducting device is studied numerical method. The current lead is cooled by surrounded He gas by natural convection. To find wall heat flux, the linearization method is adopted Numerical results using natural convection cooling are compared with conventional cooling methods such as conduction cooling and vapor cooling. The results shows that the minimum heat dissipation is much smaller than conduction cooling. Also, the minimum heat dissipation is obtained for the non-zero gradient of temperature at warm end. HTS current lead operating current sharing mode is reduce heat flow to superconducting system.

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30W급 LED 투광등 설치각도에 따른 히트싱크 온도분포에 관한 연구 (A Study on Heatsink Temperature Distribution according to the Installation Angle of a 30W LED Floodlight)

  • 이영호;이중섭;정한식
    • 한국기계가공학회지
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    • 제18권8호
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    • pp.24-30
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    • 2019
  • This study investigated the heat dissipation characteristics of a heat-sensitive LED. The results of the empirical test showed that the best temperature intensification was found at 90 with 15-fins, and the heatsink installed perpendicular to the direction of the flow of air was directly connected to the air in the largest heat shield area, leading to the best cooling, and the number of fin also resulted increase in the heat discharge area, resulting in the largest cooling action with 15 fins. It was found that the rate of air flow changed in the range of 1.5m/s to 2.5m/s, but only by a deviation of about $2^{\circ}C$ to $3^{\circ}C$ from the current state of 15 fins at 2.5m/s, and the rate of air flow increased, but the performance of the heat release was not significantly increased. As a result wind speed with minimum air flow conditions of 1.5m/s can greatly contribute to the heat dissipation performance.

HEATING OF SUNSPOT CHROMOSPHERES BY SLOW-MODE ACOUSTIC SHOCK WAVES

  • Lee, Myung-Gyoon;Yun, Hong-Sik
    • 천문학회지
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    • 제18권1호
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    • pp.15-31
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    • 1985
  • Making use of the arbitrary shock theory developed by Ulmschneider (1967, 1971) and Ulmschneider and Kalkofen (1978), we have calculated the dissipation rates of upward-travelling slow-mode acoustic shock waves in umbral chromospheres for two umbral chromosphere models, a plateau model by Avrett (1981) and a gradient model by Yun and Beebe (1984). The computed shock dissipation rates are compared with the radiative cooling rate given by Avrett (1981). The results show that the slow-mode acoustic shock waves with a period of about 20 second can heat the low umbral chromospheres travelling with a mechanical energy flux of $2.6{\times}10^6\;erg/cm^2s$ at a height of $300{\sim}400km$ above the temperature minimum region.

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자연대류를 고려한 전류도입선의 최적설계 (Optimal design of Current lead considering Natural convection)

  • 손봉준;설승윤
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2003년도 추계학술대회
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    • pp.103-108
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    • 2003
  • In this paper, the current lead for superconducting device is studied by numerical method. The current lead is cooled by surrounded $N_{2}$ gas by natural convection. The heat conduction equation for current lead and boundary layer equation for $N_{2}$ gas must be solved simultaneously. The boundary layer equation for $N_{2}$ gas is highly nonlinear for varied temperature of current lead. So the linearization method is adopted for simplicity. Numerical results using natural convection cooling are compared with the conventional cooling methods such as conduction cooling and vapor cooling methods. The main difference of natural convection cooing is the non-zero temperature gradient at the top of current lead for the minimum heat dissipation into superconducting devices. For the optimized conduction-cooling and vapor-cooling current leads, the temperature gradient at the top of current lead is zero. Also, the heat flow at the cold end is much smaller than conduction cooling case.

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고압 다이캐스팅용 알루미늄 합금의 열전도성 및 주조성에 미치는 첨가원소의 영향 (Effect of Alloying Elements on the Thermal Conductivity and Casting Characteristics of Aluminum Alloys in High Pressure Die Casting)

  • 김철우;김영찬;김정한;조재익;오민석
    • 대한금속재료학회지
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    • 제56권11호
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    • pp.805-812
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    • 2018
  • High pressure die casting is one of the precision casting methods. It is highly productivity and suitable for manufacturing components with complex shapes and accurate dimensions. Recently, there has been increasing demand for efficient heat dissipation components, to control the heat generated by devices, which directly affects the efficiency and life of the product. Die cast aluminum alloys with high thermal conductivity are especially needed for this application. In this study, the influence of elements added to the die cast aluminum alloy on its thermal conductivity was evaluated. The results showed that Mn remarkably deteriorated the thermal conductivity of the aluminum alloy. When Cu content was increased, the tensile strength of cast aluminum alloy increased, showing 1 wt% of Cu ensured the minimum mechanical properties of the cast aluminum. As Si content increased, the flow length of the alloy proportionally increased. The flow length of aluminum alloy containing 2 wt% Si was about 85% of that of the ALDC12 alloy. A heat dissipation component was successfully fabricated using an optimized composition of Al-1 wt%Cu-0.6 wt%Fe-2 wt%Si die casting alloy without surface cracks, which were turned out as intergranular cracking originated from the solidification contraction of the alloy with Si composition lower than 2 wt%.

고온초전도 테이프를 이용한 적층형 전류 도입선의 최적설계 (Optimum Design of Multi-Stacking Current Lead Using HTS Tapes)

  • 설승윤;김민수;나필선
    • 한국초전도ㆍ저온공학회논문지
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    • 제3권1호
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    • pp.35-39
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    • 2001
  • The optimum cross-sectional area profile of gas-cooled high-temperature superconductor(HTS) current lead is analyzed to have minimum helium boil-off rate. The conventional constant area HTS lead has much higher helium consumption than the optimum HTS lead considered in this study. The optimum HTS lead has variable cross-sectional area to have constant satiety factor. An analytical formula of optimum shape of lead and temperature profile are obtained. For multi-stacking HTS current leads, the optimum tape lengths and minimum heat dissipation rate are also formulated. The developed formulations are applied to the Bi-2223 material, and the differences between constant area, constant safety-factor, and multi-stacking current leads are discussed.

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고온초전도 테이프를 이용한 다단 전류 도입선의 최적설계 (Optimal Design of Multi-Step Current Leads Using HTS Tapes)

  • 김민수;나필선;설승윤
    • 한국초전도저온공학회:학술대회논문집
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    • 한국초전도저온공학회 2001년도 학술대회 논문집
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    • pp.84-88
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    • 2001
  • The optimum cross-sectional area Profile of gas-cooled high-temperature superconductor (HTS) current lead is analyzed to have minimum helium boil-off rate. The conventional constant area HTS lead has much higher helium consumption than the optimum HTS lead considered in this study. The optimum HTS lead has variable cross-sectional area to have constant safety factor. An analytical formula of optimum shape of lead and temperature profile are obtained. For multi-step HTS current leads, the optimum tape lengths and minimum heat dissipation rate are also formulated. The developed formulations are applied to the Bi-2223 material, and the differences between constant area, constant safety-factor, and multi-step current leads are discussed.

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Reaction of Gae-Phase Atomic Hydrogen with Chemisorbed Hydrogen Atoms on an Iron Surface

  • Kim, M. S.;Ree, J.
    • Bulletin of the Korean Chemical Society
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    • 제18권9호
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    • pp.985-994
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    • 1997
  • The reaction of gas-phase atomic hydrogen with hydrogen atoms chemisorbed on Fe(110) surface is studied by use of classical trajectory procedures. Flow of energy between the reaction zone and bulk solid phase has been treated in the generalized Langevin equation approach. A London-Eyring-Polanyi-Sato energy surface is used for the reaction zone interaction. Most reactive events are found to occur in strong single-impact collisions on a subpicosecond scale via the Eley-Rideal mechanism. The extent of reaction is large and a major fraction of the available energy goes into the vibrational excitation of H2, exhibiting a vibrational population inversion. Dissipation of reaction energy to the heat bath can be adequately described using a seven-atom chain with the chain end bound to the rest of solid. The extent of reaction is not sensitive to the variation of surface temperature in the range of Ts=0-300 K in the fixed gas temperature, but it shows a minimum near 1000 K over the Tg=300-2500 K.

상변화물질과 열관을 병렬 조합한 위성부품 열제어장치의 수치해석적 연구 (Numerical Study on the Thermal Control Device for Satellite Components Using the Phase Change Material Combined with Heat Pipe in Parallel)

  • 신윤섭;김태수;김택영;서영배;서정기;현범석;전형열
    • 한국항공우주학회지
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    • 제44권4호
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    • pp.373-379
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    • 2016
  • 주기적 단속적으로 작동하는 위성부품의 열제어를 위하여 고상-액상 상변화물질(PCM, Phase Change Material)과 열관을 병렬로 결합한 열제어장치를 제안하였으며, 이의 성능을 수치해석을 통하여 검증하였다. 상변화 중 큰 잠열과 일정하게 유지되는 온도에 의하여 작은 방열판 면적에서도 부품의 최고온도를 제어할 수 있으며, 냉각기에는 PCM에 축적된 에너지가 방출됨으로써 보온히터 소모전력을 절약할 수 있다. 동일한 형태의 Al TBM(Thermal Buffer Mass)을 사용하면 비슷한 효과를 기대할 수 있으나, 질량과 보온히터의 소모전력이 증가하므로 PCM에 비하여 비효율적이다. 설계된 PCM 열제어장치는 발열량과 작동시간에 따라 그 양을 최적화할 수 있다.