• 지구물리
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• 제2권3호
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• pp.225-233
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• 1999

암석의 비저항값은 암석 자체의 성질뿐만 아니라 유체의 종류, 온도, 물 포화율, 접촉상태, 유도분극, 측정기기 및 사용전원의 주파수 등, 여러 요인에 의하여 영향을 받는다. 이 연구는 암석의 비저항을 정확하고 정밀하게 측정하기 위한 기초 연구의 일환으로서, 비저항 실측자료를 비교 분석하는 과정을 통하여 비저항 측정에 영향을 주는 다양한 요소들을 추적하고, 아울러 비저항 측정에 있어서 최적의 환경 조건을 찾고자 하였다. 특히 온도, 물 포화율, 시료와 전극의 접촉상태, 측정 주파수의 영향 등이 종합적으로 분석되었으며, 전도성 접착제와 절연 테이핑 방법 그리고 시계열 비저항자료의 이용이 비저항 측정의 정확도와 정밀도 향상에 크게 기여할 수 있음을 보였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2214-2219
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• 2008

The thermal contact resistance(TCR) of nanosized contact spots has been investigated through a multiscale analysis which considers the resolution of surface topography. A numerical simulation is performed on the finite element model of rough surfaces. Especially, as the contact size decreases below the phonon mean free path, the size dependent thermal conductivity is considered to calculate the TCR. In our earlier model which follows an elastic material, the TCR increases without limits as the number of nanosized contact spots increases in the process of scale variation. However, the elastoplastic contact induces a finite limit of TCR as the scale varies. The results are explained through the plastic behavior of the two contacting models. Furthermore, the effect of air conduction in nanoscale is also investigated.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2357-2362
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• 2008

LHP is different from a conventional heat pipes in design and heat and fluid flow passages. The situations of the former is much complex than the latter. In LHPs, evaporation occurs at the contact interface between the heating plate and the porous wick, so some micro channels machined at the contact interface serve to let the vapor flow out of the evaporator. This complexity of contact geometry was known to cause a high resistance to heat flow. The present work was to study the problem of heat passage across the contact surface for LHPs and determine those values contact resistance. For two cases of contact structures, the thermal contact resistances were examined experimentally, one being obtained through mechanical contact under pressure and the other through sintered bonding. Nickel powder wick and copper plate were used for specimens. The result showed that a substantial reduction of contact resistance of an order of degree could be obtainable by sintered bonding.

• 오토저널
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• 제17권3호
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• pp.11-18
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• 1995

본 논문에서는 주철 라이너를 삽입한 알루미늄 블럭 엔진 개발과정에서 주조 불량이 발생하였을때, 냉각계에 일어나는 제반 현상을 분석하고, 이를 해결해 나가는 과정을 기술하였다. 이를 위하여 주철 블럭과 알루미늄 블럭을 장착한 엔진의 피스톤 온도와 블럭의 열유속, 열정산을 측정하였다. 측정한 결과는 다음과 같다. 1. 알루미늄 블럭 제작시 주철 라이너와 알루미늄 블럭 사이에 공기층이 크거나, 용탕 충진이 불완전한 주조 불량이 발생하면 열접촉 저항이 커져 엔진 열전달 경로에 큰 영향을 준다. 2. 알루미늄 블럭 제작시 주조 불량이 발생하면 피스톤에서 라이너로의 전열량이 줄어듦에 따라 냉각수로의 전열량은 감소하는데, 6,000rpm, 전부하에서 알루미늄 블럭의 출력 대비 냉각수로의 방열량의 비는 38.3%이고, 주철 블럭은 44.1%이다. 3. 알루미늄 블럭 제작시 주조 불량이 발생하면, 피스톤 온도가 15-20.deg.C 정도 상승하여 피스톤 손상을 유발시킬 수 있다. 4. 알루미늄 블럭의 주조가 완벽하게 되어 주철 라이너와 알루미늄 몸체 사이에서의 열접촉저항이 없어지면, 스토로크 방향에 따른 금속면 온도 분포가 균일하게 된다. 5. 실린더 라이너의 주조상태 개선없이 오일젯을 사용한 결과 피스톤의 온도를 만족할 만한 수준으로 감소시켰다. 6. 6000rpm, 전부하에서 오일젯 적용시 출력 대비 냉각수로의 방열량의 비가 38.3%에서 36.2%로 감소하고, 출력대비 오일로의 방열량의 비는 9.6%에서 11.2%로 증가한다. 7. 오일젯 작용시 오일 펌프의 용량 증대와 오일 쿨러의 장착이 필수적이다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 춘계학술대회 논문집
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• pp.635-640
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• 1996

A thermo-elastic system in the production machine has highly nonlinear dynamic characteristics. In general, the finite element method is utilized for accurate analysis. However, it requires large computing time. Thus, thermo-elastic systems are usuallymodeled as electric and fluid system using lumped para,eter. In this paper. we propose the bondgraph model and transient simulation methodology of thermo-elastic system in consideration of various boundary and joint contact conditions. Consequently, the proposed method ensures a possibility of its on-line compensation about undesirable phenomena by using real time estimate process and electronic cooling device for thermal appropriate behavior. Thermo-elastic model consisting of bush and shaft including contact condition is presented.

• 마이크로전자및패키징학회지
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• 제6권4호
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• pp.23-33
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• 1999

유한요소법을 이용한 IGBT 3상 풀브릿지 모듈의 열.응력 해석을 수행하였다. 패키지 재료에 의한 영향을 살피고자 AIN과 $A1_2O_3$절연기판을 사용한 경우를 비교하였으며, 적층구조의 규격을 변화시켜 열해석 및 열응력 해석결과를 비교하였다. 열해석 경계조건 설정에 따른 차이를 비교하기 위하여 등가열전달계수 경계조건(FHTCC)과 일정온도 경계조건(CTC)으로 나누어 해석하였다. 절연기판 면적의 증가는 열저항 감소에 거의 기여하지 못하였으나 열응력 감소에는 상당한 효과를 보였는데, 기판면적이 3배 넓어지면 열저항 감소분은 $A1_2O_3$ 절연기판 모듈에서 8.9%정도, AIN 절연기판 모듈에선 1.5% 정도 감소하는데 그쳤으나 열응력은 최고 60%의 감소를 보였다. 또한 솔더의 두께가 증가할수록 열저항은 증가하였으나, 열응력은 감소 또는 일정하게 유지함을 확인하였다. 각 모듈에서 최대응력값은 모두 절연기판과 접촉된 상, 하부 Cu pad에서 발생하였으며 모듈 패키지 가장자리 부분보다는 중앙부의 응력값이 높았다.

• 한국정밀공학회지
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• 제27권1호
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• pp.91-98
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• 2010

The increasing of power and processing speed and miniaturization of central processor unit (CPU) used in electronics equipment requires better performing thermal management systems. A typical thermal management package consists of thermal interfaces, heat dissipaters, and external cooling systems. There have been a number of experimental techniques and procedures for estimating thermal conductivity of thin, compressible thermal interface material (TIM). The TIM performance is affected by many factors and thus TIM should be evaluated under specified application conditions. In compact packaging of electronic equipment the chip is interfaced with a thin heat spreader. As the package is made thinner, the coupling between heat flow through TIM and that in the heat spreader becomes stronger. Thus, a TIM characterization system for considering the heat spreader effect is proposed and demonstrated in detail in this paper. The TIM test apparatus developed based on ASTM D-5470 standard for thermal interface resistance measurement of high performance TIM, including the precise measurement of changes in in-situ materials thickness. Thermal impedances are measured and compared for different directions of heat dissipation. The measurement of the TIM under the practical conditions can thus be used as the thermal criteria for the TIM selection.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2009년 추계학술대회논문집
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• pp.135-144
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• 2009

In this study, the heat transfer and fluid flow characteristics of a condenser for a refrigerator are analyzed with the numerical method. The main objective of the study is to obtain basic data in order to develop a new type of condenser focused on an influence of thermal resistance of air side and thermal contact resistance on the heat transfer performance. The CFD technique was used for whole study, and experiments were performed in order to verify the reliability of the numerical analysis and predict the thermal contact resistance. In this study, a heat exchanger sample was made of a part of condenser to make the experimental and numerical analysis simple and efficient. Water was used for the inner working fluid of the heat exchanger, and an experimental apparatus was composed concisely. A heat exchanger sample of tube type was used to verify the reliability of numerical analysis, and a heat exchanger of fin and tube type was used to predict the ratio of thermal contact resistance to the overall thermal resistance.

• 한국전산유체공학회지
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• 제15권1호
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• pp.46-55
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• 2010

In this study, the heat transfer and fluid flow characteristics of a condenser for a refrigerator are analyzed with the numerical method. The main objective of the study is to obtain basic data in order to develop a new type of condenser focused on an influence of thermal resistance of air side and thermal contact resistance on the heat transfer performance. The CFD technique was used for whole study, and experiments were performed in order to verify the reliability of the numerical analysis and predict the thermal contact resistance. In this study, a heat exchanger sample was made of a part of condenser to make the experimental and numerical analysis simple and efficient. Water was used for the inner working fluid of the heat exchanger, and an experimental apparatus was composed concisely. A heat exchanger sample of tube type was used to verify the reliability of numerical analysis, and a heat exchanger of fin and tube type was used to predict the ratio of thermal contact resistance to the overall thermal resistance.

• 설비공학논문집
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• 제26권1호
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• pp.32-37
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• 2014

The thermal contact resistance (TCR) is one of the important resistance components in cryogenic systems. Cryogenic measurement devices using a cryocooler can be affected by TCR because the device has to consist of several metal components that are in contact with each other for heat transfer to the specimen without a cryogen. Therefore, accurate measurement and understanding of TCR is necessary for the design of cryogenic measurement devices using a cryocooler. The TCR occurs at the interface between metals and it can be affected by variable factors, such as the roughness of the metal surface, the contact area and the contact pressure. In this study, we designed a TCR measurement system at variable temperature using a cryocooler as a heat sink. Copper was selected as a specimen in the experiment because it is widely used as a heat transfer medium in cryogenic measurement devices. We measured the TCR between Cu and Cu for various temperatures and contact pressures. The effect of the interfacial materials on the TCR was also investigated.