• 설비공학논문집
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• 제18권8호
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• pp.664-671
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• 2006

We propose the correlation to predict the spreading thermal resistance on a plate with symmetrical four heat sources. The correlation transforms four heat sources to a single equivalent heat source and then the spreading thermal resistance can be obtained with the existing equation for a single heat source. When the four heat sources are mounted on a square base plate, the correlation is expressed as a function of the heat source size, the length of base plate, the plate thermal conductivity and the distance between heat sources. Compared to the results of three-dimensional numerical analysis, the spreading thermal resistance by the proposed correlation is in good agreement within 10 percent accuracy.

• 한국정밀공학회지
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• 제33권8호
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• pp.629-634
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• 2016

Laser-assisted machining (LAM) is one of the most effective methods of processing difficult-to-cut materials, such as titanium alloys and various ceramics. However, it is associated with problems such as the inability of the laser heat source to generate an appropriate preheating temperature. To solve the problem, thermally assisted machining with multiple heat sources is proposed. In this study, thermal analysis of multiple heat sources by laser and arc is performed according to power, heat source size, and leading heat source position. Then, the results are analyzed according to each condition. The results of this analysis can be used as a reference to predict preheating temperature in thermally assisted machining with multiple heat sources.

• 태양에너지
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• 제18권4호
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• pp.39-47
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• 1998

The natural convection heat transfer in a vertical plate with discrete heat sources was studied experimentally. The particular interest was the thermal interaction of the heat sources. In this study, the radiative and conductive heat transfer were considered as heat loss, Thus, the net convective heat transfer rate was presented as adiabatic temperature and thermal wake function. As a results, for non-uniform heating condition, heat input ratio(q1/q2) was most dominant parameter for the thermal wake function. The convective heat transfer rate is decreased with the increasing of channel ratio. For the range of $7.50{\times}10^5<Rac<8.66{\times}10^6$, a useful correlation was proposed as a function of channel Rayleigh number.

• 대한기계학회논문집
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• 제13권4호
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• pp.726-733
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• 1989

본 연구에서는 전력 다이오드 칩이 방산판에 부착되어 있는 형상을 기준하여 열전달 모형을 설정하고 해석적 해가 존재하는 단수형상으로 이상화하여 국부적 온도 상승을 일으키는 조건을 파악하고 실제형상의 모형에 대하여 유한요소해석에 의한 온도분포 계산결과를 제시한다.또한 발열체가 인접해 있는 경우에 대한 온도 집중 현상의 결과도 아울러 검토한다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.792-793
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• 2008

This paper deals with the temperature calculation using equivalent thermal network for surface mounted permanent magnet synchronous motor(SPMSM) under the steady-state condition. In the equivalent thermal network, heat sources are generated from copper loss and iron loss. Heat transfer consists of conduction, convection and radiation. However, radiation is neglected in this paper because its effect is much smaller than others. Although the heat transfer coefficient in conduction use material property, heat transfer coefficient in convection is difficult to measure due to the atmosphere and ambient condition. Temperatures of each region in SPMSM are measured by thermocouple in operating condition and the thermal resistances of convection are calculated by kirchhoff's current law(KCL) and experimental result. In order to verify the validation and reliability of the proposed equivalent thermal network, temperature which is calculated other load condition is compared with experimental results. Accordingly, temperatures of each region in other SPMSMs will be easily predicted by the proposed equivalent thermal network.

• 대한기계학회논문집B
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• 제40권2호
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• pp.119-126
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• 2016

본 연구는 실험적인 방법과 열유동 해석 방법을 사용하여 대용량 압출형 히트싱크의 방열성능에 미치는 열원 대칭배열의 영향을 고찰하고, 이를 바탕으로 제조원가가 낮은 고효율의 히트싱크를 제안하고자 한다. 실험결과를 통해서 유사한 유효 유동단면적을 가지는 경우에 히트싱크의 전열면적이 방열성능에 큰 영향을 줌을 확인할 수 있었으며, 히트싱크의 양면 모두를 이용하는 방열이 훨씬 효과적인 방열이 가능함을 알 수 있었다. 또한, 대칭으로 열원을 배치한 경우가 비대칭 배치보다 효율적으로 방열됨을 알 수 있었다. 해석연구의 결과를 통해서는 실험결과와 정성적으로는 유사한 경향을 확인할 수 있었으며, 실험연구에서 확인하지 못한 질량유량별 및 투입열량별 추이, 단면과 양면 사용의 정량적 비교 등이 가능하였다.

• Coupled systems mechanics
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• 제8권5호
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• pp.415-437
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• 2019

The present research deals with two-dimensional axisymmetric deformation in transversely isotropic magneto thermoelastic solid with and without energy dissipation, with two temperature and time-harmonic source. The proposed model is helpful for finding the type of relations between mechanical and thermal fields as most of the structural elements of heavy industries are frequently related to mechanical and thermal stresses at a higher temperature. The Hankel transform has been used to find a solution to the problem. The displacement components, stress components, and temperature distribution with the horizontal distance in the physical domain are calculated numerically. The effect of time-harmonic source and two temperature is depicted graphically on the resulting quantities.

• 설비공학논문집
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• 제20권11호
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• pp.711-717
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• 2008

Despite the fact that UFAD(Under Floor Air Distribution) systems have many benefits and are being applied in the field in increasing numbers, there is a strong need for an improved fundamental understanding of several key performance features of these systems. This study numerically investigates the effect of supplied air temperature and supplied flow rate on the performance of UFAD, especially focused on thermal comfort. Also this study has compared UFAD with conventional overhead air distribution system. In contrast to the well-mixed room air conditions of the conventional overheat system, UFAD system produces an overall floor-to-ceiling airflow pattern that takes advantage of the natural buoyancy produced by heat sources in the occupied zone and more efficiently removes heat loads and contaminants from the space. Thermal comfort parameters were evaluated by CFD approach and then PMV was computed to detect the occupants' thermal sensation. Results show that radiative mean temperature plays crucial role on the evaluating PMV. Until now, the radiative temperature has been the missing link between CFD and thermal comfort, but the present study paves the way for overcoming this weakness.

• 대한기계학회논문집A
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• 제29권4호
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• pp.526-533
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• 2005

Reliability problem in inkjet printhead, one of MEMS devices, is also very important. To eject an ink drop, the temperature of heater must be high so that ink contacting with surface reaches above $280^{o}C$ on the instant. Its heater is embedded in the thin multi-layer in which several materials are deposited. MEMS processes are the main sources of residual stresses development. Residual stress is one of the factors reducing the reliability of MEMS devices. We measured residual stresses of single layers that consist of multilayer. FE analysis is performed using design of experiment(DOE). Transient analysis for heat transfer is performed to get a temperature distribution. And then static analysis is performed with the temperature distribution obtained by heat transfer analysis and the measured residual stresses to get a stress distribution in the structure. Although the residual stress is bigger than thermal stress, thermal stress is more influential on fatigue life.

• 한국기계가공학회지
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• 제18권10호
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• pp.93-98
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• 2019

Recently, with the development of the aerospace and automotive industries, the demand for high-melting-point materials has increased. However, high-melting-point materials are difficult to cut through conventional machining methods. Thermally assisted machining (TAM) is a method for improving the machinability by preheating the materials. A laser, the most commonly used device for TAM, has high efficiency through local preheating but is not sufficient for maintaining a high preheating temperature due to rapid cooling. However, the use of multi-heat sources can supplement the disadvantage of a single heat source. The high preheating temperature can be maintained with a wide and deep heat-affected zone (HAZ) by multi-heat sources. The purpose of this study is to analyze the preheating effects of multi-heat sources using laser plasma. Thermal analysis and preheating experiments were carried out. As a result, the high preheating effect of multi-heat sources compared with a single heat source was verified.