• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제23권3호
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• pp.157-178
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• 2019

The present correspondence is conveyed on to consider the fascinating and novel characteristics of radiative hydromagnetic convective flow of a chemically reacting fluid over an exponentially accelerated inclined porous plate. Exact solutions for the fluid velocity, temperature and species concentration, under Boussinesq approximation, are obtained in closed form by the two term perturbation technique. The interesting parts of thermal dispersing outcomes are accounted in this correspondence. Graphical evaluation is appeared to depict the trademark direct of introduced parameters on non dimensional velocity, temperature and concentration profiles. Also, the numerical assortment for skin friction coefficient, Nusselt number and Sherwood number is examined through tables. The certification of current examination is confirmed by making an examination with past revelations available in composing, which sets a benchmark for utilization of computational approach.

• 한국기계가공학회지
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• 제20권6호
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• pp.70-75
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• 2021

Recently, several efforts have been made to improve the thermal efficiency of a refrigerant compressor. In this study, we attempted to improve energy efficiency ratio (EER) performance by reducing the superheat of the linear compressor. To this end, heat generated inside the compressor must be effectively dissipated. Therefore, heat dissipation was improved by processing ribs in the gap-flow region generated owing to the vibration of the compressor body. The results showed that the convective heat transfer coefficient becomes significantly high when ribs are used, increasing the heat dissipation rate. This helps improve EER by reducing the superheat of the compressor.

• Steel and Composite Structures
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• 제38권5호
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• pp.523-531
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• 2021

The generalized thermoelastic analysis problem of a two-dimension porous medium with and without energy dissipation are obtained in the context of Green-Naghdi's (GNIII) model. The exact solutions are presented to obtain the studying fields due to the pulse heat flux that decay exponentially in the surface of porous media. By using Laplace and Fourier transform with the eigenvalues scheme, the physical quantities are analytically presented. The surface is shocked by thermal (pulse heat flux problems) and applying the traction free on its outer surfaces (mechanical boundary) through transport (diffusion) process of temperature to observe the analytical complete expression of the main physical fields. The change in volume fraction field, the variations of the displacement components, temperature and the components of stress are graphically presented. Suitable discussion and conclusions are presented.

• Structural Engineering and Mechanics
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• 제82권2호
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• pp.259-270
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• 2022

The paper investigates the residual stresses arising in a thermoviscoelastic cylinder as a result of layer-by-layer deposition of material on its lateral surface. Internal stresses are caused by incompatible deformations that accumulate in the assembly as a result of joining parts with different temperatures. For the analysis of internal stresses, an analytical solution to the axisymmetric quasi-static problem of thermoelasticity for a growing cylinder is constructed. It is shown that the distribution of residual stresses depends on the scenario of the surfacing process. In this case, the supply of additional heat to the growing body can significantly reduce the unevenness of temperature fields and reduce the intensity of residual stresses. The most effective is uneven heating, which can be realized, by the action of an alternating current with a tunable excitation frequency. The temperature and residual stresses fields on the growing surface is analyzed numerically for Titanium and Copper materials.

• 한국전산유체공학회지
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• 제13권2호
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• pp.48-54
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• 2008

COMS (Communication, Ocean and Meteorological Satellite) is a geostationary satellite and has been developing by KARI for communication, ocean and meteorological observations. It will be launched by ARIANE 5. Ka-band components are installed on South panel, where single solar array wing is mounted. Radiators, embedded heat pipes, external heat pipe, insulation blankets and heaters are utilized for the thermal control of the satellite. The Ka-band payload section is divided several areas based on unit operating temperature in order to optimize radiator area and maximize heat rejection capability. Other equipment for sensors and bus are installed on North panel. The ocean and meteorological sensors are installed on optical benches on the top floor to decouple thermally from the satellite. During the transfer orbit operation, satellite will be under severe thermal environments due to low dissipation of components, satellite attitudes and LAE(Liquid Apogee Engine) firing. This paper presents temperature and heater power prediction and validation of thermal control design during transfer orbit operation.

• 조명전기설비학회논문지
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• 제21권10호
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• pp.82-88
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• 2007

이 논문에는 교류전압에서 ZnO 피뢰기 소자의 열적 전기적 특성을 기술하였다. ZnO 피뢰기 소자의 누설전류는 시간의 변화에 따라 측정하였다. ZnO 피뢰기 소자의 온도분포를 열화상카메라에 의해 관측하였다. ZnO 피뢰기 소자의 열화 및 열폭주 현상은 열발생과 열방산을 결정짓는 ZnO 피뢰기 소자의 온도한계와 밀접한 관계가 있다. ZnO 피뢰기 소자의 저항은 ZnO 피뢰기 소자의 온도와 누설전류에 의해 민감하게 변화한다. 결론적으로 ZnO 피뢰기 소자의 열화 및 열폭주 현상은 ZnO 피뢰기 소자의 온도와 소자를 통해 흐르는 누설전류에 상당히 의존적인 것으로 나타났다.

• 한국수소및신에너지학회논문집
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• 제26권2호
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• pp.184-191
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• 2015

As the power electronics system increases the frequency, the power loss and thermal management are paid more attention. This research presents a real time model of dissipation power with junction temperature response for 120kw IGBT inverter which is applied to the thermal management of high power IGBT inverter. Since the computational time is critical for real time simulation, look-up tables of IGBT module characteristic curve are implemented. The power loss from IGBT provides a clue to calculate the temperature of each module of IGBT. In this study, temperature of each layer in IGBT is predicted by lumped capacitance analysis of layers with convective heat transfer. The power loss and temperature of layers in IGBT is then communicated due to mutual dependence. In the dynamic model, PWM pulses are employed to calculation real time IGBT and diode power loss. Under Matlab/Simulink$^{(R)}$ environment, the dynamic model is validated with experiment. Results showed that the dynamic response of power loss is closely coupled with effective thermal management. The convective heat transfer is enough to achieve proper thermal management under guideline temperature.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2007년도 추계 학술대회논문집
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• pp.227-231
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• 2007

COMS (Communication, Ocean and Meteorological Satellite) is a geostationary satellite and has been developing by KARI for communication and ocean and meteorological observations. It will be launched by ARIANE 5. Ka-band components are installed on South panel, where single solar array wing is mounted. Radiators, embedded heat pipes, external heat pipe, insulation blankets and heaters are utilized for the thermal control of the satellite. The Ka-band payload section is divided several areas based on unit operating temperature in order to optimize radiator area and maximize heat rejection capability. Other equipment for sensors and bus are installed on North panel. The ocean and meteorological sensors are installed on optical benches on the top floor to decouple thermally from the satellite. During the transfer orbit operation, satellite will be under severe thermal environments due to low dissipation of components, satellite attitudes and LAE(Liquid Apogee Engine) firing. This paper presents temperature and heater power prediction and validation of thermal control design during transfer orbit operation.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2005년도 한국우주과학회보 제14권1호
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• pp.129-132
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• 2005

본 논문에서는 HAUSAT-2의 궤도 열 해석과 열 제어계의 예비설계를 살펴본다. HAUSAT-2의 열 제어계를 설계하기 위해서 우선 열 제어의 기본 이론 및 열 평형 방정식을 바탕으로 능동 및 수동의 각종 열 제어 방법을 고려하여 HAUSAT-2에 적합한 열 제어 방법 및 재질을 선정하였다(Karam 1998). 또한, 예상궤도인 고도 650km, 경사각 $98^{\circ}$의 태양동기궤도에서 HAUSAT-2가 처해지는 열 환경에 대한 분석 및 위성체의 각 면에 가해지는 은도 분포 및 범위를 예측하여 이를 바탕으로 열 제어계를 설계하였다. 열 해석은 기본적으로 시스템레벨의 해석, 부품레벨의 해석, 보드레벨의 해석 차순으로 진행되었으며, 현재 HAUSAT-2의 열 해석은 발열이 비교적 많은 보드의 해석까지 진행된 상태이며, 이러한 열 해석을 통해서 얻은 결과는 요구조건을 만족하지 못하는 부분에 대해 설계 변경 등을 통해서 모든 부품이 허용온도 범위를 유지하도록 HAUSAT-2의 열 제어계를 설계하였다. 향후 구조-열 모델(STM; Structure & Thermal Model)을 제작한 후 열 진공시험을 통해 열 해석 결과에 대한 검증을 수행할 것이다.

• 마이크로전자및패키징학회지
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• 제23권2호
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• pp.73-78
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• 2016

집적회로(Integrated Circuit) 소자의 트랜지스터(transistor) 밀도 증가는 소자에서 발생하는 열 방출(heat dissipation)의 급격한 상승을 초래하여 열 문제를 발생시키고, 이는 소자의 성능과 열적 신뢰성에 영향을 크게 미친다. 열문제의 해결방안 중 본 연구에서는 냉매를 이용한 액체 냉각방법을 연구하였으며, 실리콘 웨이퍼에 관통실리콘비아(through Si via)와 마이크로 채널(microchannel)을 딥 반응성 이온 애칭(deep reactive ion etching)로 구현한 후 유리기판과 어노딕본딩을 통하여 액체 냉각 구조를 제작하였다. 제작된 마이크로 채널 위에 Ag, Cu 또는 Cr/Au/Cu bump를 스크린프린팅(screen printing) 방법으로 형성하였고, 범프의 유무를 통해 액체 냉각 전후의 냉각 모듈의 실리콘 표면온도의 변화를 적외선현미경으로 분석하였다. Cr/Au/Cu bump가 탑재된 액체 냉각 모듈의 경우 가열온도 $200^{\circ}C$에서 냉각 전후의 실리콘 표면 온도 차이는 약 $45.2^{\circ}C$이고, 전력밀도 감소는 약 $2.8W/cm^2$ 이었다.