• Title/Summary/Keyword: thermal modeling

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Thermal Analysis and Design of AlGaInP-based Light Emitting Diode Arrays

  • Ban, Zhang;Liang, Zhongzhu;Liang, Jingqiu;Wang, Weibiao;JinguangLv, JinguangLv;Qin, Yuxin
    • Current Optics and Photonics
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    • v.1 no.2
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    • pp.143-149
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    • 2017
  • LED arrays with pixel numbers of $3{\times}3$, $4{\times}4$, and $5{\times}5$ have been studied in this paper in order to enhance the optical output power and decrease heat dissipation of an AlGaInP-based light emitting diode display device (pixel size of $280{\times}280{\mu}m$) fabricated by micro-opto-electro-mechanical systems. Simulation results showed that the thermal resistances of the $3{\times}3$, $4{\times}4$, $5{\times}5$ arrays were $52^{\circ}C/W$, $69.7^{\circ}C/W$, and $84.3^{\circ}C/W$. The junction temperature was calculated by the peak wavelength shift method, which showed that the maximum value appears at the center pixel due to thermal crosstalk from neighboring pixels. The central temperature would be minimized with $40{\mu}m$ pixel pitch and $150{\mu}m$ substrate thickness as calculated by thermal modeling using finite element analysis. The modeling can be used to optimize parameters of highly integrated AlGaInP-based LED arrays fabricated by micro-opto-electro-mechanical systems technology.

An Analysis of Thermal Conductivity of Ceramic Fibrous Insulator by Modeling & Simulation Method I (모델링/시뮬레이션 기법을 이용한 세라믹 섬유 단열재의 열전도도 해석 I)

  • Kang, Hyung;Baek, Yong-Kee
    • Journal of the Korea Institute of Military Science and Technology
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    • v.5 no.1
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    • pp.83-95
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    • 2002
  • Thermal conductivity of ceramic fibrous insulator was analysed and predicted by using the modeling/simulation technique. Ceramic fibrous insulators are widely used as high temperature insulator on account of their lightweight mass and heat resisting properties. Especially it is suitable to protect the high speed aircraft and missiles from severe aero-thermodynamic heating. Thermal conductivity of ceramic fibrous insulator could be determined from the conductive heat transfer and the radiative heat transfer through the insulator. In order to estimate conductive thermal conductivity, homogenization technique was applied, while radiative thermal conductivity was computed by means of random number and radiation probability. Particularly radiation probability can make it possible to estimate the conductivity of fibrous insulator without any experimental constant. The calculated conductivity predicted in the present study have a reasonable accuracy with an average error of 7 percent to experimental data.

Experimental Research for Identification of Thermal Stratification Phenomena in The Nuclear Powerplant Emergency Core Coolant System(ECCS). (원전 비상 노심냉각계통 배관 열성층화 현상 규명을 위한 실험적 연구)

  • Song, Dho-In;Choi, Young-Don;Park, Min-Su
    • Proceedings of the KSME Conference
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    • 2001.11b
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    • pp.735-740
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    • 2001
  • In the nuclear power plant, emergency core coolant system(ECCS) is furnished at reactor coolant system(RCS) in order to cool down high temperature water in case of emergency. However, in this coolant system, it occurs thermal stratification phenomena in case that there is the mixing of cooling water and high temperature water due to valve leakage in ECCS. This thermal stratification phenomena raises excessive thermal stresses at pipe wall. Therefore, this phenomena causes the accident that reactor coolant flows in reactor containment in the nuclear power plant due to the deformation of pipe and thermal fatigue crack(TFC) at the pipe wall around the place that it exists. Hence, in order to fundamental identification of this phenomena, it requires the experimental research of modeling test in the pipe flow that occurs thermal stratification phenomena. So, this paper models RCS and ECCS pipe arrangement and analyzes the mechanism of thermal stratification phenomena by measuring of temperature in variance with leakage flow rate in ECCS modeled pipe and Reynold number in RCS modeled pipe. Besides, results of this experiment is compared with computational analysis which is done in advance.

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A Numerical Study on a Prediction of Performance of the Metal Hydride Thermal Conversion System through the Propagation Phenomena of Superadiabatic Thermal Waves (초단열 열파동의 전파현상을 활용하는 수소저장합금 열변환 시스템의 성능예측을 위한 수치해석적 연구)

  • Kim, Gyu-Jeong;Kim, Gwan-Yeong;Chae, Jae-U
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.25 no.4
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    • pp.572-582
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    • 2001
  • A method of metal-hydride thermal conversion that is an alternative to the traditional method is proposed and investigated. The unit heat pump consists of reactors of two different metal-hydrides are distributed inside parallel channels filled with porous media. The channels are blown through with a heat-transfer agent. Thermal conversion develops as a set of successive heat waves. By a numerical-modeling method it is shown that the maximum thermal effect is attained in synchronous motion of the heat wave and the heat source (or sink) that accompanies the phase transition in the succession of unit metal-hydride pumps. The results are presented in a form convenient for prediction of the thermal and energy efficiency of the proposed thermal-conversion method in real devices.

Thermal Analysis on the Engineering Model of Command and Telemetry Unit for a Geostationary Communications Satellite (정지궤도 통신위성의 원격측정명령처리기 기술모델 열해석)

  • Kim, Jung-Hoon;Koo, Ja-Chun
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.32 no.9
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    • pp.114-121
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    • 2004
  • Thermal design changes and analysis on the engineering model of Command Telemetry Unit(CTU) for a geostationary communications satellite arc performed for the purpose of developing an engineering qualification model. A thermal model is developed by using power consumption measurement values of each functional board and thermal cycling test results. In modeling heat dissipated EEE parts, heat dissipation is imposed evenly on the EEE part footprint area which is projected to the printed circuit board. All the EEE parts of CTU meet the requirement of their allowable temperature range when placed on the engineering qualification level of thermal vacuum environments in accordance with the proposed thermal design changes.

THERMAL ANALYSES AND VERIFICATION FOR HAUSAT-2 SMALL SATELLITE (HAUSAT-2 소형위성 열해석 검증 및 보드-레벨 열해석)

  • Lee Mi-Hyeon;Kim Dong-Woon;Chang Young-Keun
    • Journal of Astronomy and Space Sciences
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    • v.23 no.1
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    • pp.39-54
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    • 2006
  • HAUSAT-2 is nano satellite with 25kg mass being developed by Space System Research Lab. in Hnakuk Aviation University. This paper addresses HAUSAT-2 small satellite thermal analyses and its verification at satellite system, electronic box, and PCB levels. Thermal model which is used for system-level and box-level thermal analyses was verified and corrected through thermal vacuum/balance test. The new board-level thermal analysis methodology, modelling high-power dissipating EEE parts directly, was proposed. The proposed methodology has been verified with test results.

A Study on Performance of Seasonal Borehole Thermal Energy Storage System Using TRNSYS (TRNSYS를 이용한 Borehole 방식 태양열 계간축열 시스템의 성능에 관한 연구)

  • Park, Sang-Mi;Seo, Tae-Beom
    • Journal of the Korean Solar Energy Society
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    • v.38 no.5
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    • pp.37-47
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    • 2018
  • The heating performance of a solar thermal seasonal storage system applied to a glass greenhouse was analyzed numerically. For this study, the gardening 16th zucchini greenhouse of Jeollanam-do agricultural research & extension services was selected. And, the heating load of the glass greenhouse selected was 576 GJ. BTES (Borehole Thermal Energy Storage) was considered as a seasonal storage, which is relatively economical. The TRNSYS was used to predict and analyze the dynamic performance of the solar thermal system. Numerical simulation was performed by modeling the solar thermal seasonal storage system consisting of flat plate solar collector, BTES system, short-term storage tank, boiler, heat exchanger, pump, controller. As a result of the analysis, the energy of 928 GJ from the flat plate solar collector was stored into BTES system and 393 GJ of energy from BTES system was extracted during heating period, so that it was confirmed that the thermal efficiency of BTES system was 42% in 5th year. Also since the heat supplied from the auxiliary boiler was 87 GJ in 5th year, the total annual heating demand was confirmed to be mostly satisfied by the proposed system.

Inner Temperature Distribution by Two Appearances of Series-Cell Configured Battery Pack using Cylindrical Cells (원통형셀 기반 직렬배터리팩의 외형(정사/직사면체) 차이에 의한 내부 열분포 기초해석)

  • Han, Dong-Ho;Lee, Pyeng-Yeon;Park, Jin-Hyeng;Kim, Jonghoon;Yoo, Kisoo;Cho, In-Ho
    • The Transactions of the Korean Institute of Power Electronics
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    • v.23 no.6
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    • pp.408-414
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    • 2018
  • Given that lithium-ion batteries are expected to be used as power sources for electric and hybrid vehicles, thermodynamics experimentation and prediction based on experimental data were performed. Thermal, electrochemical, and electrochemical/electrical-thermal models were used for accurate battery modeling. Various applications of different battery packs were demonstrated, and thermal analysis was performed using the same experimental conditions for square and rectangular battery packs. Accurate thermal analysis for a single cell should be prioritized to determine the thermal behavior of the battery pack. The energy balance equation, which contains heat generation and heat transfer factors, defines the thermal behavior of the battery pack. By comparing battery packs of different shapes tested under the same condition, this study revealed that the rectangular battery pack is superior to the square battery pack in terms of the maximum temperature of inner cells and temperature variation between cells.

Effect of non-uniform temperature distributions on nonlocal vibration and buckling of inhomogeneous size-dependent beams

  • Ebrahimi, Farzad;Salari, Erfan
    • Advances in nano research
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    • v.6 no.4
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    • pp.377-397
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    • 2018
  • In the present investigation, thermal buckling and free vibration characteristics of functionally graded (FG) Timoshenko nanobeams subjected to nonlinear thermal loading are carried out by presenting a Navier type solution. The thermal load is assumed to be nonlinear distribution through the thickness of FG nanobeam. Thermo-mechanical properties of FG nanobeam are supposed to vary smoothly and continuously throughout the thickness based on power-law model and the material properties are assumed to be temperature-dependent. Eringen's nonlocal elasticity theory is exploited to describe the size dependency of nanobeam. Using Hamilton's principle, the nonlocal equations of motion together with corresponding boundary conditions based on Timoshenko beam theory are obtained for the thermal buckling and vibration analysis of graded nanobeams including size effect. Moreover, in following a parametric study is accompanied to examine the effects of the several parameters such as nonlocal parameter, thermal effect, power law index and aspect ratio on the critical buckling temperatures and natural frequencies of the size-dependent FG nanobeams in detail. According to the numerical results, it is revealed that the proposed modeling can provide accurate frequency results of the FG nanobeams as compared some cases in the literature. Also, it is found that the small scale effects and nonlinear thermal loading have a significant effect on thermal stability and vibration characteristics of FG nanobeams.