Efficient Correlation Method for Satellite Thermal Analysis Model Using Multiple Linear Regression and Optimization Algorithms

Jaewon Kang,김건웅,Somin Shin,김정호 한국항공우주학회 2023 International Journal of Aeronautical and Space Sc Vol.24 No.5

As the thermal analysis model of satellites is used as an important indicator for thermal design, it must accurately simulate the thermal behaviour of actual satellites for precise thermal design. To increase the accuracy of the thermal analysis model, it must be correlated using the thermal balance test data for actual satellite models. To achieve this, we herein propose an efficient correlation method for satellite thermal analysis models using multiple linear regression techniques with quadratic terms and optimization algorithms. The proposed method reduces the amount of computation by choosing dominant parameters through sensitivity analysis and creating a multiple linear regression model that can replace the thermal analysis model in the subsequent optimization process. Subsequently, optimization algorithms are applied to the multiple linear regression model to perform the correlation of the thermal analysis model. In this study, the numerical validation of the proposed method was performed using numerical data from a reference thermal analysis model to verify the reliability and accuracy of the proposed method before it was applied to the correlation of the thermal analysis model using experimental data. The thermal analysis result of the reference thermal analysis model was set as the target value to correlate, and quantitative performance evaluation was performed for various combinations of optimization algorithms and design of experiments methods by comparing the estimated analysis parameters. The results of this study demonstrate that the proposed method can efficiently produce an accurate correlation model for thermal analysis.

Thermal and structural analysis of a cryogenic conduction cooling system for a HTS NMR magnet

In, Sehwan,Hong, Yong-Ju,Yeom, Hankil,Ko, Junseok,Kim, Hyobong,Park, Seong-Je The Korea Institute of Applied Superconductivity a 2016 한국초전도저온공학회논문지 Vol.18 No.1

The superconducting NMR magnets have used cryogen such as liquid helium for their cooling. The conduction cooling method using cryocoolers, however, makes the cryogenic cooling system for NMR magnets more compact and user-friendly than the cryogen cooling method. This paper describes the thermal and structural analysis of a cryogenic conduction cooling system for a 400 MHz HTS NMR magnet, focusing on the magnet assembly. The highly thermo-conductive cooling plates between HTS double pancake coils are used to transfer the heat generated in coils, namely Joule heating at lap splice joints, to thermal link blocks and finally the cryocooler. The conduction cooling structure of the HTS magnet assembly preliminarily designed is verified by thermal and structural analysis. The orthotropic thermal properties of the HTS coil, thermal contact resistance and radiation heat load are considered in the thermal analysis. The thermal analysis confirms the uniform temperature distribution for the present thermal design of the NMR magnet within 0.2 K. The mechanical stress and the displacement by the electromagnetic force and the thermal contraction are checked to verify structural stability. The structural analysis indicates that the mechanical stress on each component of the magnet is less than its material yield strength and the displacement is acceptable in comparison with the magnet dimension.

해양플랜트에 사용되는 배관의 열 하중과 구조물의 운동에 따른 구조안전성 평가

류보림(Ryu, Bo Rim),강호근(Kang, Ho Keun),Duong Phan Anh,이진욱(Lee, J in Uk) 한국항해항만학회 2021 한국항해항만학회지 Vol.45 No.4

본 논문에서는 해양구조물의 배관에 작용하는 환경조건과 구조물의 움직임에 따른 구조안전성 평가를 수행하였다. 배관에 작용하는 조건은 N2 generator의 설계 조건을 분석하여 최고온도와 최저온도 조건을 적용하였다. 구조물의 움직임은 DNV 규칙에 따라 계산하여 적용하였다. 각각의 조건을 조합하고 열 하중, 운동 하중 그리고 배관지지대의 유무에 따라 총 26가지 하중 조합을 구성하였고 상용프로그램인 MSC Patran/Nastran을 이용하여 해석을 진행하였다. 열해석은 Steady-state 방법인 Sol 153, 열-구조 연성 해석은 Linear-static 방법인 Sol 101을 각각 적용하여 수행하였다. 해석 결과, Set 1과 Set 2에서는 배관 내의 온도가 낮을수록, Set 3에서는 온도가 높을수록, Set 4에서는 배관 내외부의 온도 차가 클수록 응력이 증가하는 경향이 있었다. 하지만, 온도 하중만 있는 조건과 운동 하중만 있는 조건에서의 응력의 합이 두 하중의 복합 하중 조건에서의 응력과 같은 값을 나타내지는 않았다. 즉, 운동 하중에 의한 영향은 운동의 방향, 배관의 배치나 지지대의 위치 등에 따라 달라진다는 것을 알 수 있다. 따라서, 설계 시점에서 배관에 작용하는 운동 하중의 크기와 방향, 배관의 배치 그리고 배관 지지대의 위치 등을 종합적으로 고려할 필요가 있다. The objective of this study was to evaluate structural safety according to environmental conditions acting on the piping of offshore structure and the motion of the structure. As for conditions acting on the piping, the maximum and minimum temperature conditions were used to analyze the design conditions of N2 generator. The motion of the structure was calculated and applied according to the DNV(Det Norske Veritas) rule. Each condition was combined and a total of 26 load combinations were constructed according to thermal load, motion load, and presence or absence of pipe support. Analysis was performed using a commercial program MSC Patran/Nastran. Thermal analysis was performed by applying the steady-state method, Sol 153. Thermal-structural coupled analysis was performed using Sol 101, a linear-static method. As a result of the analysis, the stress tended to increase when temperature inside the pipe was lower in Set 1 and Set 2, when temperature was higher in Set 3, and when the temperature difference between the inside and outside of the pipe in Set 4 was increased. However, the sum of stresses in the condition with only temperature load and the condition with only the kinetic load did not show the same value as the stress in the composite load condition of two loads. That is, the influence of the motion load varied depending on the direction of motion, the arrangement of pipes, and the position of the support. Therefore, it is necessary to comprehensively consider the size and direction of the motion load acting on the piping, the arrangement of the piping, and the location of the pipe supports during the design of piping.

Thermal-structural analysis of ITER triangular support for dominant load verification

Kim, Y.G.,Hwang, J.H.,Jung, Y.J.,Kim, H.S.,Ahn, H.J. North-Holland ; Elsevier Science Ltd 2014 Fusion engineering and design Vol.89 No.12

The triangular support is located on the lower inner shell of vacuum vessel of ITER, which should be designed to withstand various loads such as nuclear heat, coolant pressure and so on. The appropriateness of its design is evaluated under the dominant load that could represent the most conservative condition among the design loads. In order to decide the dominant load, a valid method for thermal-structural analysis is firstly verified considering contradictory behaviors between heat and structural loads. In this paper, two approaches; one-way coupling and load combination, are introduced for thermal-structural analysis. The one-way coupling is a method generally used but has a limit to apply on contradictory conditions. The load combination could give a proper solution since it evaluates each load independently and then adds up each result linearly. Based on the results of each case, structural analysis for another load case, baking condition with incident, is conducted to find out which load is dominant for triangular support. Consequently, it is found that the baking condition is the dominant load for triangular support bracket. The proposed load combination method gives a physically reasonable solution which can be used as a reference for checking the validity of other thermal-structural analysis. It is expected that these results could be applied for manufacturing design of the triangular support under various load conditions.

ASSESSMENT OF THERMAL FATIGUE IN MIXING TEE BY FSI ANALYSIS

Jhung, Myung Jo Korean Nuclear Society 2013 Nuclear Engineering and Technology Vol.45 No.1

Thermal fatigue is a significant long-term degradation mechanism in nuclear power plants. In particular, as operating plants become older and life time extension activities are initiated, operators and regulators need screening criteria to exclude risks of thermal fatigue and methods to determine significant fatigue relevance. In general, the common thermal fatigue issues are well understood and controlled by plant instrumentation at fatigue susceptible locations. However, incidents indicate that certain piping system Tee connections are susceptible to turbulent temperature mixing effects that cannot be adequately monitored by common thermocouple instrumentations. Therefore, in this study thermal fatigue evaluation of piping system Tee-connections is performed using the fluid-structure interaction (FSI) analysis. From the thermal hydraulic analysis, the temperature distributions are determined and their results are applied to the structural model of the piping system to determine the thermal stress. Using the rain-flow method the fatigue analysis is performed to generate fatigue usage factors. The procedure for improved load thermal fatigue assessment using FSI analysis shown in this study will supply valuable information for establishing a methodology on thermal fatigue.

Thermal and structural analysis of a cryogenic conduction cooling system for a HTS _MR magnet

Sehwan In,Yong-Ju Hong,Han-Kil Yeom,Junseok Ko,Hyobong Kim,Seong-Je Park 한국초전도.저온공학회 2016 한국초전도저온공학회논문지 Vol.18 No.1

The superconducting NMR magnets have used cryogen such as liquid helium for their cooling. The conduction cooling methodusing cryocoolers, however, makes the cryogenic cooling system for NMR magnets more compact and user-friendly than thecryogen cooling method. This paper describes the thermal and structural analysis of a cryogenic conduction cooling system for a400 MHz HTS NMR magnet, focusing on the magnet assembly. The highly thermo-conductive cooling plates between HTS doublepancake coils are used to transfer the heat generated in coils, namely Joule heating at lap splice joints, to thermal link blocks andfinally the cryocooler. The conduction cooling structure of the HTS magnet assembly preliminarily designed is verified by thermaland structural analysis. The orthotropic thermal properties of the HTS coil, thermal contact resistance and radiation heat load areconsidered in the thermal analysis. The thermal analysis confirms the uniform temperature distribution for the present thermaldesign of the NMR magnet within 0.2 K. The mechanical stress and the displacement by the electromagnetic force and the thermalcontraction are checked to verify structural stability. The structural analysis indicates that the mechanical stress on each componentof the magnet is less than its material yield strength and the displacement is acceptable in comparison with the magnet dimension.

Assessment of Thermal Fatigue in Mixing Tee by FSI Analysis

Myung Jo Jhung 한국원자력학회 2013 Nuclear Engineering and Technology Vol.45 No.1

Thermal fatigue is a significant long-term degradation mechanism in nuclear power plants. In particular, as operating plants become older and life time extension activities are initiated, operators and regulators need screening criteria to exclude risks of thermal fatigue and methods to determine significant fatigue relevance. In general, the common thermal fatigue issues are well understood and controlled by plant instrumentation at fatigue susceptible locations. However, incidents indicate that certain piping system Tee connections are susceptible to turbulent temperature mixing effects that cannot be adequately monitored by common thermocouple instrumentations. Therefore, in this study thermal fatigue evaluation of piping system Tee-connections is performed using the fluid-structure interaction (FSI) analysis. From the thermal hydraulic analysis, the temperature distributions are determined and their results are applied to the structural model of the piping system to determine the thermal stress. Using the rain-flow method the fatigue analysis is performed to generate fatigue usage factors. The procedure for improved load thermal fatigue assessment using FSI analysis shown in this study will supply valuable information for establishing a methodology on thermal fatigue.

Hydro-thermo-mechanical analysis on high cycle thermal fatigue induced by thermal striping in a T-junction

Sun-Hye Kim,허남수,김문기,조대근,최영환,Jin-Ho Lee,최재붕 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.10

Turbulent mixing in a T-junction causes thermal striping which is irregular and frequent fluctuation of thermal layer. Thermal striping is a significant thermal problem because it causes unpredicted high cycle thermal fatigue and fatigue cracking in piping systems. Since this phenomenon is hardly detected by common plant instruments due to high frequency and complex mechanism, numerical approaches are indispensable for a precise evaluation. This research was carried out to define a suitable and effective numerical method for evaluating thermal stress and fatigue induced by thermal striping. A three-dimensional hydro-thermo-mechanical analysis was performed based on one-way separate analysis method to find out the characteristics of stress components and its results were compared to the results of a one-dimensional simplified analysis. It was found that the detailed three-dimensional analysis is indispensable because one-dimensional simplified analysis can overestimate or underestimate according to the assumed heat transfer coefficient and cannot estimate the considerable mean stress effects.

항공기 플랩 제어를 위한 선형 구동기의 구조 안전성 평가

김동협,김상우 항공우주시스템공학회 2019 항공우주시스템공학회지 Vol.13 No.4

The objective of this study was to evaluate the structural safety of the basic design for the linear actuator for the flap control of aircrafts. The kinetic behavior of the linear actuator was determined using the multi-body dynamics (MBD) analysis, and the contact force was calculated to be used as input data for the structural analysis based on the finite element analysis. In the structural analysis, the thermal and static behaviors of the linear actuator satisfying the designed velocity were examined, and the structural safety of the linear actuator evaluated. Moreover, the dynamic behaviors of the key components of the linear actuator were investigated by the modal analysis. The actuation rod linearly moved with about 5 mm/s when the motor operated at 225 rpm and the maximum contact force of 32.83 N occurred between two driving gears. Meanwhile, the structural analysis revealed that the maximum thermal and static stresses were 1.57% and 78% of the yield strength of steel, respectively, and they were in a safe range of the structure. In addition, the linear actuator for the basic design is stable to the resonance by avoiding the natural frequencies of the components. 본 연구에서는 항공기 플랩 제어를 위한 선형 구동기의 기본 설계에 대한 구조 안전성을 평가하였다. 다물체 동역학 분석을 통해 선형 구동기의 기계적 운동을 이해하였고, 접촉 하중을 산출하여 유한요소해석 기반의 구조 분석에 적용하였다. 구조 분석에서는 선형 구동기의 설계 속도 조건에 대한 열, 정적 거동을 검토하였고, 구조적 안전성을 평가하였다. 또한 모드 해석을 수행하여 동적 거동을 분석하였다. 분석 결과, 모터가 225 rpm으로 작동 시 구동 로드는 약 5 mm/s로 병진 운동하였고, 기어 간 최대 32.83 N의 접촉 하중이 발생하였다. 한편, 최대 열 응력과 정 응력은 철의 항복강도의 약 1.57%, 78%로 발생하였고, 각 부품은 서로의 공진 주파수를 회피하였다. 따라서 제안된 선형 구동기의 기본설계는 구조적으로 안전하며, 공진에 대해 안정적임을 밝혔다.

An Analytical Study on the Thermal-Structure Stability Evaluation of Mill-Turn Spindle with Curvic Coupling

Choon-Man Lee(이춘만),Ho-In Jeong(정호인) 한국기계가공학회 2020 한국기계가공학회지 Vol.19 No.1

As demand for high value-added products with hard materials increases, the line center is used for producing high value-added products in many industries such as aerospace, automobile fields. The line center is a key device for smart factory automation that can improve the production efficiency and the productivity. Therefore, the development of a mill-turn line center is necessary to produce high value-added products with complex shapes flexibly. In the mill-turn process, a milling process and a turning process are combined. In particular, the turning process needs to increase the rigidity of the spindle. The purpose of this study is to analyze the thermal-structural stability through thermo-structural coupled analysis for a mill-turn spindle with a curvic coupling. The maximum temperature and thermal stability of the spindle were analyzed by thermal distribution. In addition, the thermal deformation and thermal-structural stability of the spindle were analyzed through thermo-structural coupled analysis.