• Title/Summary/Keyword: 열전달거동

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Experimental and Numerical Investigation for the Effect of Baffles on Heat Transfer Behaviors in a Rectangular Channel (사각채널에서 설치된 배플에 의한 열전달 거동에 관한 실험 및 수치해석)

  • Kang, Ho-Keun;Ahn, Soo-Whan;Bae, Sung-Taek
    • Proceedings of the Korean Society of Marine Engineers Conference
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    • 2006.06a
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    • pp.45-46
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    • 2006
  • Experimental and numerical analysis on the heat transfer behaviors and the associated frictional loss in a rectangular channel with two inclined perforated baffles($\;5^{\circ}$) mounted on the bottom plate has been systematically performed. The parametric effects of perforated baffles (3, 6, 9 holes) and flow Reynolds number on heat transfer characteristics of the heated target surface are explored. A combination of two baffles of same overall size was considered and the flow Reynolds number for this study is varied between 28,900 and 61,800. Comparisons of the experimental data with the numerical results by commercial code CFX 5.7 are made. As for the investigation of heat transfer behaviors on local Nusselt number with the two baffles installed at $x/D_h=0.8\;and\;x/D_h=8.0$, it is evident that there exist an optimum perforation density to maximize heat transfer coefficients; i.e., the maximum Nusselt number decreases with increasing number of holes.

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Air-side Heat Transfer and Friction Characteristics of Fined-tube Heat Exchangers under Heating Condition (핀-관 열교환기의 난방운전 시 공기측 열전달 및 마찰특성)

  • Kwon, Young Chul;Chang, Keun Sun;Ko, Kuk Won;Kim, Young Jae;Park, Byung Kwon
    • Applied Chemistry for Engineering
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    • v.17 no.5
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    • pp.476-482
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    • 2006
  • An experimental study has been performed to investigate the characteristics of air-side heat transfer and friction of a fined tube heat exchanger under heating conditions. Air enthalpy calorimeter was used to obtain the performance evaluation and analysis of the fined tube heat exchanger. Eight finned tube heat exchangers with slit fin, louver fin, and plain fin were used. The air-side heat transfer coefficient was calculated by the log-mean-temperature-difference. Air-side heat transfer and friction were presented in terms of j factor and friction factor on Reynolds number. From the experimental result, it was found that the variations of air-side heat transfer and friction of fined tube heat exchanger with the change of the fin configuration, row number, fin pitch, and tube circuit were obtained. j factor and friction factor decreased with Reynolds number increased. The tube circuit affected the air-side heat transfer and friction. In the case of slit and louver fin, j factor of 1st row was higher than that of 2nd row. But, with increasing Re, j factor was reversed. The characteristics of j factor and friction factor of 2nd row heat exchanger were different according to the kind of fins.

가스 발생기를 이용한 수직발사 사출 시스템에 관한 해석적 연구

  • 변종렬;오종윤;황용석
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 1999.10a
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    • pp.28-28
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    • 1999
  • 본 연구에서는 가스 발생기에서 발생되는 고온, 고압의 가스를 이용하여 유도탄을 수직 발사하는 사출 시스템에 대해 해석적 연구를 수행하였다. 사출 시스템에 의한 수직발사 방식은 발사관내에 설치된 가스 발생기에 의해 생성된 가스가 사출 실린더의 피스톤을 구동시켜, 피스톤에 연결된 유도탄을 요구되는 높이로 사출 시킨 후 유도탄이 점화되는 발사방식이다. 이러한 발사방식은 유도탄 자체의 부스터 발사방식에 비해 유도탄의 화염에 의한 영향이 적다. 현재 사출 시스템은 가스발생기, 가스 튜브, 사출 실린더와 피스톤으로 구성되어있다. 본 논문은 가스 발생기에서 사출 실린더까지의 내부 유동장을 일차원적으로 모델링하였고, 가스발생기, 가스튜브, 실런더 내의 유동과 열전달 과정 및 유도탄의 동적거동에 대한 미분방정식을 연립하여 4th-order Runge-Kutta 방법으로 계산하였다. 또한 가스튜브와 사출 실린더의 열전달 손실에 대하여 1차원 비정상 열전도 방정식의 수치적 계산을 통해 에너지 손실을 계산하였다. 특히 해석에 사용된 작동유체인 추진제 가스의 열학적 상태량은 온도 함수의 5차 다항식으로 표현하여 사용하였다. 이론적인 해석을 통해 사출 장치 시스템의 성능 요구조건과 신뢰성을 만족시키기 위한 가스발생기의 추진제 그레인 및 사출 시스템 설 계 조건을 도출하였다.

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Heat Transfer Analysis of Bi-Material Problem with Interfacial Boundary Using Moving Least Squares Finite Difference Method (이동최소제곱 유한차분법을 이용한 계면경계를 갖는 이종재료의 열전달문제 해석)

  • Yoon, Young-Cheol;Kim, Do-Wan
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.20 no.6
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    • pp.779-787
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    • 2007
  • This paper presents a highly efficient moving least squares finite difference method (MLS FDM) for a heat transfer problem of bi-material with interfacial boundary. The MLS FDM directly discretizes governing differential equations based on a node set without a grid structure. In the method, difference equations are constructed by the Taylor polynomial expanded by moving least squares method. The wedge function is designed on the concept of hyperplane function and is embedded in the derivative approximation formula on the moving least squares sense. Thus interfacial singular behavior like normal derivative jump is naturally modeled and the merit of MLS FDM in fast derivative computation is assured. Numerical experiments for heat transfer problem of bi-material with different heat conductivities show that the developed method achieves high efficiency as well as good accuracy in interface problems.

An experimental study for boiling heat transfer enhancement under electric fields (전기장하에서의 비등 열전달 촉진에 관한 실험적 연구)

  • O, Si-Deok;Gwak, Ho-Yeong
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.20 no.7
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    • pp.2298-2314
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    • 1996
  • Electric field effect on boiling of refrigerants R11, R113, and FC72 has been investigated experimentally. One purpose of the experimental investigation is to determine the effects of the electrode arrangements on electrohydrodynamic boiling of the above mentioned liquids. The test equipment employed in the experiment consists of a shell and tube heat exchanger with six or six and twelve rows of electrode wires around the tube. It has been found that the applied voltage promotes the boiling heat transfer coefficient except FC72. Boiling heat transfer enhancement obtained is about 230% for R11, 280% for R113. It has also been observed that bubbles detached from the tube aggregate at the place where the electrical gradient force balances with the buoyancy one. These aggregated bubbles force to decrease the boiling heat transfer coefficient as well as to reduce the voltage needed to the dielectric breakdown.

An Evaluation on Thermal-Structural Behavior of Nozzle Assembly during Burning Time (연소시간 중 노즐조립체의 열-구조적 거동분석에 관한 연구)

  • Ro, Younghee;Seo, Sanggyu;Jeong, Seongmin
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2017.05a
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    • pp.536-542
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    • 2017
  • A great deal of difficulty is encountered in the thermo-mechanical analyses of nozzle assembly for solid propellant rocket motors. The main issue in this paper is the modeling of the boundary conditions and the connections between the various components-gaps, relative movements of the components, contacts, friction, etc. This paper evaluated the complex phenomena of nozzle assembly during burning time with co-simulation which include fluid, thermal surface reaction/ablation and structural analysis. The validity of this approach was verified by comparison of analysis results with measured strains.

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An Evaluation on Thermal-structural Behavior of Nozzle Assembly during Burning Time (연소시간 중 노즐조립체의 열-구조적 거동분석에 관한 연구)

  • Ro, Younghee;Seo, Sangkyu;Jeong, Seongmin
    • Journal of the Korean Society of Propulsion Engineers
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    • v.22 no.4
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    • pp.36-43
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    • 2018
  • A great deal of difficulty is encountered in the thermo-mechanical analyses of nozzle assemblies for solid propellant rocket motors. The main issue in this paper is the modeling of the boundary conditions and the connections between the various components-gaps, relative movements of the components, contacts, friction, etc. This paper evaluates the complex phenomena of nozzle assemblies during burning time with co-simulations that include fluid, thermal surface reaction/ablation, and structural analysis. The validity of this approach is verified via comparison of analysis results with measured strains.

A Study on the Thermal Behaviour of Via Design in the Ceramic Package (세라믹 패키지 내에서 비아에 따른 열적 거동에 관한 연구)

  • 이우성;고영우;유찬세;김경철;박종철
    • Journal of the Microelectronics and Packaging Society
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    • v.10 no.1
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    • pp.39-43
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    • 2003
  • Thermal management is very important for the success of high density circuit design in LTCC. In this paper, LTCC substrates containing thermal via and pad were fabricated in order to study the influence of the thermal dissipation. To realize the accurate thermal analysis for structure design, a series of simple thermal conductivity measurement by laser flash method and parametric numerical analysis have been carried out. The LTCC substrate including via and Ag pad has good thermal conductivity over 103 W/mK which is 44% value of pure Ag material. Thermal behaviors with via arrays, size and density in the LTCC substrate were studied by numerical method.

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Thermal Management of a Nickel/Metal Hydride Battery (Nickel/Metal Hydride 전지의 열관리기술 개발)

  • Kim, Junbom
    • Applied Chemistry for Engineering
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    • v.8 no.4
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    • pp.667-672
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    • 1997
  • Thermal behavior of high capacity Nickel/Metal hybride battery in analyzed using the NISA software which is based on the three dimensional finite element method. Differential energy balance equation is used for the conduction heat transfer of the battery, while convective heat transfer equation is used for the interface between the battery and air. Heat generation rate and convective heat transfer coefficient are tested as variables to investigate thermal behavior, and the generalized equation for maximum temperature inside the battery is developed. The abrupt rise of the battery temperature due to the quick charge or discharge can be prevented from the use of metallic cooling fin. In addition, temperature augmentation of the battery is negligible when the low thermal conductive and thin insulating material is used outside of the battery case.

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