• 한국기계가공학회지
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• 제14권4호
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• pp.62-72
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• 2015

Interest in three-dimensional (3D) printing processes has grown significantly, and several types have been developed. These 3D printing processes are classified as Selective Laser Sintering (SLS), Stereo-Lithography Apparatus (SLA), and Fused Deposition Modeling (FDM). SLS can be applied to many materials, but because it uses a laser-based material removal process, it is expensive. SLA enables fast and precise manufacturing, but available materials are limited. FDM printing's benefits are its reasonable price and easy accessibility. However, metal printing using FDM can involve technical problems, such as suitable component supply or the thermal expansion of the heating part. Thus, FDM printing primarily uses materials with low melting points, such as acrylonitrile butadiene styrene (ABS) or polylactic acid (PLA) resin. In this study, an FDM process for enabling metal printing is suggested. Particularly, the nozzle and heatsink for this process are focused for stable printing. To design the nozzle and heatsink, multi-physical phenomena, including thermal expansion and heat transfer, had to be considered. Therefore, COMSOL Multiphysics, an FEM analysis program, was used to analyze the maximum temperature, thermal expansion, and principal stress. Finally, its performance was confirmed through an experiment.

• 한국전기전자재료학회논문지
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• 제27권8호
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• pp.541-546
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• 2014

Korea Expressway Corporation established standard of LED lighting fixture in Dec. 2013. To raise compatibility, the standard requires a fixed form and it is applied to street lights and tunnel lights, etc. Because streetlight has different circumstance condition from tunnel light that is down light and exposed to constant wind velocity over height of 8 meters, in case of LED module which has the same shape, characteristic of radiant heat can be different. In this paper, we designed 25 [W] LED Module that is designated by standard of Korea Expressway Corporation and analyzed characteristics of radiant heat about natural convection and forced convection. It is dropped 10.12[$^{\circ}C$] that max temperature is decreased by increasing 20 mm of bended height of heatsink at the condition of natural convection. Radiant heat characteristic of bended height 35 mm became 78.08[$^{\circ}C$] at the condition of natural convection, 55.30[$^{\circ}C$] at the condition of forced convection so that 22.78[$^{\circ}C$] is decreased that is 29.1[%] decrease. Bended height 55mm became 67.96[$^{\circ}C$] at the condition of natural convection, 48.04[$^{\circ}C$] at the condition of forced convection so that 19.92[$^{\circ}C$] is decreased that is 29.3% decrease.

• 한국전기전자재료학회논문지
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• 제26권12호
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• pp.920-923
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• 2013

In this paper, the characteristics of a carbon nanotube composite heat sink proposed to replace the advanced Al heat sinks for LED lighting devices were studied. Proposed CMP-PLA heat sink was made by mixing 20~70 wt% carbon nanotube, 20~70 wt% bio-degradable polymer of melt-blended PLA (poly lactic acid) and PBS (poly butylene succinate) and PLA nucleating agents composed of the mixture of soybean oil and biotites, at $150{\sim}220^{\circ}C$ with 1,000~1,500 rpm. Optical and electric characteristics of 7.5 W LED lighting devices using heat sinks with such prepared CMP-PLA were investigated. And, the properties of the heat, which was not released from the CMP-PLA type heat sinks, was also investigated. The color temperature of LED lighting devices using the CMP-PLA heat sinks was 5,956 K, which is x= 0.32 and y= 0.34 in the XY chromaticity, and the color rendering index was 75. The luminous flux and the luminous efficiency of LED lighting devices using the CMP-PLA heat sinks was 540.6 lm and 72.68 lm/W respectively. Measured initial temperature of the heat sinks was $27^{\circ}C$, and their temperature increased as time to be saturated at $52^{\circ}C$ after an hour.

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 1996년도 학술대회
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• pp.27-31
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• 1996

In this paper, The SSPA(Solid State Power Amplifier) is 100 watts amplifier which is used with C-Band Satellite communication Up-Link frequency, 5.875 ∼6.425 GHz. SSPA requires more output power than is available from a single GaAs FET with result it is necessary to combine the output of many device. To achieve a high power, it is important to make a good N-way power divider which has a small different phase, good combining efficiency and high power handling capability. The reliability of Power GaAs FET decrease with increasing junction temperature, power amplifier in general dissipate amount of power. It is important to provide them with a heatsink and a temperature compensation circuit to dispose of the unwanted heat. To compensate temperature, Using PIN diode attenuator, it is enable to get a precision gain control. The output power of the SSPA is more than 100 watt with which the TWTA (Traveling-Wave Tube Amplifier) can be replaced. Each stage was measured by the Network analyzer PH8510C, Power meter Booton 42BD, The gain is more than 53 dB, flatness is less than 1.5 dB.

• KIEAE Journal
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• 제14권6호
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• pp.81-86
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• 2014

In recent years, many researchers have considered the building energy consumption reduction accordingly to deal with abnormal climate changes and greenhouse gas reduction. However, the lighting energy use ratio has increased in spite of the development of the high efficiency lighting device. Therefore, the study aims to produce the LED lighting applications for the effective lighting heat removal by using the heat characteristics of LED lighting and analyzing the heat removal effect. In order to increase radiant heat efficiency, the heat pipe and heat sink was attached on PCB as LED lighting applications. Experiment was conducted to verify the temperature and air velocity of inside duct: thermocouples, anemometer. The heat removal effect of LED lighting applications was measured by observing the temperature of the lighting applications and the change of air velocity in duct. The experiment shows that the temperature change in the duct according to air velocity was $0.9{\sim}5.8^{\circ}C$. It is also concluded that heat removal was calculated from 33 to 81W.

• 한국기계가공학회지
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• 제16권2호
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• pp.142-148
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• 2017

The objective of this study is to investigate the cooling characteristics of a heat sink for an LED headlight used in passenger cars. To this end, this study conducts the experimental and numerical analysis of the heat sink heated at constant heat fluxes without air flow applied. In the experiments, heat was transferred at a constant heat flux through the bottom of a heat sink. The measured temperature on pre-selected locations of the heat sink was in good agreement with the numerically predicted one. The experimental and numerical results indicate that the convective heat transfer coefficient for the natural convection mode was decreased by increasing the heat flux applied to the bottom of heat sink, lowering the cooling capabilities.

• 반도체디스플레이기술학회지
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• 제15권3호
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• pp.12-17
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• 2016

In this study, numerical simulations for the conjugate heat transfer of air with a heat-sink of CPU were conducted. The heat-sink consisted of many fins of cylinder shape and the effect of the number of fins on the cooling performance of the heat sink was investigated. Grid independent solutions were obtained to compare the maximum temperature of the heat-sink for various conditions. It was found that maximum temperature of the heat-sink asymptotically approached 310K as the number of fins went to infinity. The energy exchange of air with the heat-sink was found to be nearly independent on the number of fins.

• 한국전기전자재료학회논문지
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• 제28권2호
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• pp.137-141
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• 2015

The purpose of this study is examining thermal dissipation materials for the lighting and radiate efficiency improvement of 8W LED and confirming the properness of the thermal dissipation materials for LED heat sink. Solid Works flow simulation on 8W class COB was done based on the material characteristics of thermal conductive polymer materials. According to the result of simulation, Al had better thermal dissipation performance than PET. Highest temperature was $7.6^{\circ}C$ higher while lowest temperature was $7.8^{\circ}C$ lower. The test on the heat sinks made by the materials, highest temperature was $4.1^{\circ}C$ higher and lowest temperature was $3.9^{\circ}C$ lower. It is possible to confirm that Al heat sink has better thermal dissipation efficiency because it has better dispersion of heat generated at junction temperature and less heat cohesion. The weight of PET heat sink was reduced than Al heat sink by 46.9% by the density difference between Al and PET. In conclusion, thermal dissipation performance of thermal conductive polymer is lower than Al material however, it is possible to lighting heat sink because thermal conductive polymer has better formability, has lower specific weight and enables various design options.

• 한국컴퓨터정보학회논문지
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• 제14권1호
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• pp.145-151
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• 2009

아키텍처 유닛 단위의 프로세서 온도 시뮬레이션은 신뢰성 있는 프로세서 개발이 중요해진 오늘날에 반드시 필요한 실험이다. 프로세서 공정이 미세화하고 회로 집적이 고밀도화하면서 기존의 냉각 기법으로 효과적인 해결이 어려운 열섬(hotspot) 현상이 발생하고 있기 때문이다. 그러나 지금까지 제안되었거나 개발되어있는 온도 시뮬레이션 도구들은 시뮬레이션 시간이 너무 오래 걸리거나 정밀도가 떨어지는 등의 제약으로 인하여 실제 시스템을 모델링하기에 부족한 점이 있었다. 본 논문에서는 성능계수기를 이용한 실시간 온도 추적 도구의 정밀도를 높이는 방법을 제시하고, 이를 구현하는 것을 목표로 한다. 그 결과, 동적 전압 및 주파수 조절(Dynamic Voltage and Frequency Scaling, DVFS)과 같은 온도 제어 기술을 실제 프로세서에 적용시켰을 때 일어나는 온도 변화를 실시간으로 추적할 수 있는 기반환경이 조성되었다.

• 한국정보전자통신기술학회논문지
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• 제7권1호
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• pp.20-25
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• 2014

차세대 친환경 조명인 LED소자는 온도가 올라갈수록 LED의 발광효율이 떨어지고 $80^{\circ}C$이상 올라갈수록 수명이 감소하고 스펙트럼선의 파장이 본래의 파장보다 장파장 쪽으로 이동하는 Red Shift현상 및 $T_j$ 상승에 따라 광 출력이 감소되는 큰 문제점이 대두되고 있어 열을 최소화 할 수 있는 방열설계 연구가 진행 중이다. COB Type LED의 경우 보드에 LED 칩을 직접 결합시켜 열 저항을 낮췄지만 주거용 13.5W의 경우 방열판을 통해 발열 문제를 해결해야한다. 본 논문에서는 주거용 13.5W COB LED 다운라이트에 맞게 Heat Sink를 설계하고, 그 설계한 Heat Sink와 13.5W COB를 패키징하여 Solidworks flow simulation을 통해 최적의 Fin두께를 선정하여 접촉식 온도계를 사용한 열적 특성을 분석 하고 평가 하였다.