• Journal of the Korea Institute of Military Science and Technology
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• v.11 no.1
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• pp.102-111
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• 2008

This paper describes the basic model and simulation results of thermal battery. Voltage and thermal analysis is a critical part of thermal-battery design because of the need to maintain the inner temperature above the electrolyte melting point. Traditionally, battery design has depended on an empirical approach, in which prototype batteries are outfitted with thermocouples and the design of subsequent batteries is refined accordingly. We have developed the basic model that allows the design engineer to configure or modify a battery, quickly conduct a thermal analysis, and efficiently review the results. Based on performance tests, the thermal-battery model was established and the effect of design parameters on battery performance was analyzed.

• Proceedings of the KIEE Conference
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• 2002.04a
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• pp.52-54
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• 2002

최근 초고압 전력기기에 대한 많은 연구가 활발히 진행되고 있음에도 불구하고 통전용량에 크게 영향을 미치는 열해석에 대한 연구가 많이 부족한 실정이다. 본 논문에서는 초고압전력기기인 GIS(Gas Insulated Switchgear)의 모선에 대한 열해석을 다루었다. 해석방법은 유한요소법을 이용하여 온도상승을 예측하였다. 유한요소법은 3각형 등의 임의의 형상을 요소로서 채용할 수 있으므로 3상 모선과 같이 복잡한 형상도 표현할 수 있다. 열전달계수는 형상, 유동조건, 유체의 종류를 고려한 상관식을 이용하여 해석적으로 정확히 계산하였다. 열해석에 있어 자계해석을 통한 도체 및 탱크의 손실값 산정이 선행되어야 하는데, 이 손실값이 온도상승의 원인이 되므로 정확히 계산하여야 한다. 손실의 원인이 되는 도체 및 탱크의 저항은 온도가 상승함에 따라 비선형으로 변화하는데, 이것을 고려하여 반복적으로 계산함으로서 해석의 정확성을 높이고자 하였다. 실제 모델에 대한 온도상승 실험치와 본 논문에서 제시한 방법으로 해석한 계산치와의 비교를 통해 타당성을 입증하였다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.05a
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• pp.113-122
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• 2010

A two-dimensional thermal response and ablation analysis code for predicting charring material ablation and shape change on solid rocket nozzle is presented. For closing the problem of thermal analysis, Arrhenius' equation and Zvyagin's ablation model are used. The moving boundary problem are solved by remeshing-rezoning method. For simulation of complicated thermal protection systems, this method is integrated with a three-dimensional finite-element thermal and structure analysis code through continuity of temperature and heat flux.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1999.04a
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• pp.13-13
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• 1999

본 논문에서는 해석영역의 형상변화, 즉 로켓노즐 내열재의 삭마로 인해 야기된 경계 면의 이동을 고려하면서 2차원 비정상 비등방성 재료의 열전달 문제를 해석할 수 있는 수치해석에 대해 기술하였다. 수치해석 알고리즘은 유한요소법이며 열해석시 경계면 이동으로 인한 격자계의 절점 좌표점이 계산과정 동안에 이동하는 변형 가능한 유한요소격자(transformable finite-element grid)를 사용하였다. 본 수치해석기법의 타당성 입증을 위해 극심한 열하중이 부여된 조건하에서 엄밀해가 존재하는 비정상 축대칭문제 및 고체로켓 노즐내열재에 대해 열해석을 수행하였으며, 그 결과 수치해는 엄밀해 또는 실험치와 잘 일치함을 보이었다. 여러 가지 복합재로 구성된 내삽노즐 또는 외삽노즐에 대해서도 안정된 수치해를 얻을 수 있었다. 아울러 노즐목삽입재로 탄소-탄소 복합재를 적용한 고체추진기관 내삽노즐을 해석모델로 택하여 열전달 해석을 수행하고 해석결과를 분석하였다. 노즐의 표면산화반응에 대한 열반응상수, 즉 Arrhenius 형태로 표시된 식에서 pre-exponential factor 및 activation energy 변화가 탄소-탄소 복합재 및 탄소-페놀릭 복합재의 삭마량에 미치는 영향에 대해서 고찰하였다.

• Journal of the Korean Society of Propulsion Engineers
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• v.3 no.2
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• pp.37-47
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• 1999

This paper describes the thermal analysis which can calculate the ablation depth and temperature distribution of the rocket nozzle liner allowing geometry change caused by the ablation of nozzle liner. In this analysis, Zvyagin's model is used for surface ablation and Yaroslavtseva's model for in-depth pyrolysis. A deforming finite-element grid is used to account for external-boundary movement due to the erosion of thermal liner. The accuracy of the present numerical method is evaluated with a rocket nozzle liner and the numerical solutions are favorably agreed with experimental data. The temporal variations of temperature and ablation depth at the thermal liner of another rocket nozzle are numerically simulated and the results are discussed. Special emphasis is given to the effects of kinetic constants for carbon-carbon and carbon-phenolic composites on the ablation depth of thermal liner.

• Aerospace Engineering and Technology
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• v.12 no.2
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• pp.24-29
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• 2013

A spacecraft radiator is a thermal control method to eject internally dissipated heat into the space generated from operation of unit boxes. The efficiency of thermal design may be improved by optimizing radiator design. In this paper, the optimization approach method of node-based radiator design was suggested which is to combine numerical thermal analysis with optimization algorithm. This method has meaning that it can be used practically to implement the spacecraft radiator design regardless of thermal analysis and optimization algorithm software and maintain the same basic concept of an ordinary radiator design approach based on node division of a thermal model. The overall analysis framework with thermal analysis and optimization algorithm would be presented.

• Journal of the Korean Society of Propulsion Engineers
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• v.9 no.2
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• pp.89-96
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• 2005

This study has been performed on the mechanism of heat transfer between stratospheric airship and its surroundings while the airship is staying in the air at the altitude of 20km. The computational grid of airship has been generated and the results influenced by the number and the shape of grids have been compared. The temperature distributions have been obtained through this thermal analysis considering three modes of heat transfer - conduction, convection and radiation - in stratospheric conditions. Based on the airship's surface and inner temperature variations, the influence of temperature distributions on the helium envelope and the payload has been predicted.

• Journal of the Korea Convergence Society
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• v.11 no.8
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• pp.153-158
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• 2020

In this study, the thermal and stress analyses were performed by applying a temperature condition of 100℃ at CPU cooler model. The value of heat flux value is shown to be the most at the lower rod area. The upper part becomes, the smaller the heat flow rate. The highest temperature is shown at the bottom of the CPU cooler model. Overall, the upper part becomes, the smaller the temperature becomes. Based on the temperature analysis, the thermal deformation caused by expansion, the deformation becomes smaller as the upper part of the overlapping plates. The great deformation happens at the bent area of the small rod as the lower part of model and the least deformation is shown at the lowest floor of model. In addition, the maximum thermal stress of 570.63 MPa happens at the floor below model. The stress is shown to decrease as the upper part of the overlapping plates becomes. But the stress is shown to increase somewhat at the middle part of model. By applying the study result on the thermal and stress analyses of CPU cooler, this study is seen to be suitable for the aesthetic convergence.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.1
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• pp.120-124
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• 2003

KAISTSAT- 4, an experimental small satellite, is being developd by Satellite Technology Research Center in KAIST as a sequel mission to KITSAT-1, 2, and 3. The flight model scheduled to be launched in 2003, the qualification model construction and testing have been completed recently. The satellite subsystems of the qualification model have been tested under a thermal vacuum environment harsher than expected in the orbit. Thermal balance test has also been done in order to evaluate and tune the thermal analysis model of the qualification model. This paper describes the thermal vacuum test procedure, the results, as well as the lessons learned during the tests, which can be useful for future thermal vacuum tests of small satellites.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.5
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• pp.437-446
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• 2021

As flying vehicle's speed is getting faster, the magnitude of aerodynamic heating is getting bigger. High-speed vehicle's exterior skin is heated to hundreds of degrees, and electrical equipments inside the vehicle are heated, simultaneously. Since allowable temperature of electrical equipments is low, they are vulnerable to effect of aerodynamic heating. These days, lots of techniques are applied to estimate temperature of electrical equipments in flight condition, and to make them thermally safe from heating during flight. In this paper, new model building technique for thermal safety analysis is introduced. To understand internal thermal transient characteristic of electrical equipment, simple heating experiment was held. From the result of experiment, we used our new building technique to build thermal analysis model which reflects thermal transient characteristic of original equipment. This model can provide internal temperature differences of electrical equipment and temperature change of specific unit which is thermally most vulnerable part in the equipment. So, engineers are provided much more detailed thermal analysis data for thermal safety of electrical equipment through this technique.