• 제목/요약/키워드: Thermal-flow Boundary Condition

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복합열전달과 열경계조건에 관한 연구 (Investigation of the Conjugate Heat Transfer and Wall Thermal Boundary Conditions)

  • 장병훈
    • 대한기계학회논문집B
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    • 제23권1호
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    • pp.33-42
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    • 1999
  • The effects of wan thermal boundary condition were investigated for a uniform wall temperature, a uniform wall heat flux, and for coupled heat conduction In the channel wall with transverse rectangular ribs. Numerical investigations for steady laminar flow show behavior similar to that observed experimentally in the separated flow region for flow over a cylinder. Conjugate heat transfer with a low solid-fluid thermal conductivity ratio does not lead to the same results as for the uniform heat flux boundary condition, and heat transfer reversal is found on the back sides of the ribs.

수정된 내부 에너지 비평형 1차 외삽 경계조건을 적용한 열 유동 격자 볼츠만 모델에 관한 수치적 연구 (Numerical Simulation of Thermal Lattice Boltzmann Model with a Modified In-Ternal Energy Non-Equilibrium First-Order Extrapolation Boundary Condition)

  • 정해권;김래성;이현구;이재룡;하만영
    • 대한기계학회논문집B
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    • 제31권7호
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    • pp.620-627
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    • 2007
  • In this paper, we adapt a modified internal energy non-equilibrium first-order extrapolation thermal boundary condition to the thermal lattice Boltzmann model (TLBM). This model is the double populations approach to simulate hydrodynamic and thermal fields. The bounce-back boundary condition which is a traditional boundary condition of lattice Boltzmann method has only a first order in numerical accuracy at the boundary and numerical instability. A non-equilibrium first-order extrapolation boundary condition has been verified to be of better numerical stability than the bounce-back boundary condition and this boundary condition is proved to be of second-order accuracy for the flat boundaries. The two-dimensional natural convection flow in a square cavity with Pr=0.71 and various Rayleigh numbers are simulated. The results are found to be in good agreement with those of previous studies.

커스프 균열에 대한 열응력세기 계수의 경계요소해석 (Bounary Element Analysis of Thermal Stress Intensity Factors for Cusp Cracks)

  • 이강용;조윤호
    • 대한기계학회논문집
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    • 제14권1호
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    • pp.119-129
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    • 1990
  • 본 연구에서는 선적분화 된 체적력항을 갖는 경계요소법을 이용하여, Griffi- th균열에 대한 열응력세기계수를 구하여 Sumi의 결과와 비교 검토하고, 유무한체내의 대칭 입술형및 대칭 익형 커스프균열들(symmetric lip and airfoil cusp cracks)의 열 응력세기계수를 균열묘면이 단열된 경우와 일정 온도로 유지된 경우에 대해 계산하고 자 한다.

SORET AND CHEMICAL REACTION EFFECTS ON THE RADIATIVE MHD FLOW FROM AN INFINITE VERTICAL POROUS PLATE

  • MALAPATI, VENKATESWARLU;DASARI, VENKATA LAKSHMI
    • Journal of the Korean Society for Industrial and Applied Mathematics
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    • 제21권1호
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    • pp.39-61
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    • 2017
  • In this present article, we analyzed the heat and mass transfer characteristics of the nonlinear unsteady radiative MHD flow of a viscous, incompressible and electrically conducting fluid past an infinite vertical porous plate under the influence of Soret and chemical reaction effects. The effect of physical parameters are accounted for two distinct types of thermal boundary conditions namely prescribed uniform wall temperature thermal boundary condition and prescribed heat flux thermal boundary condition. Based on the flow nature, the dimensionless flow governing equations are resolved to harmonic and non harmonic parts. In particular skin friction coefficient, Nusselt number and Sherwood number are found to evolve into their steady state case in the large time limit. Parametric study of the solutions are conducted and discussed.

유량 보존 경계 조건을 적용한 커넥팅 로드 베어링의 성능 해석 (Analysis of Connecting Rod Bearings Using Mass-Conserving Boundary Condition)

  • 김병직;김경웅
    • Tribology and Lubricants
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    • 제14권3호
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    • pp.39-45
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    • 1998
  • Reynolds equation, which describes behavior of fluid film in journal bearings, basically satisfies mass conservation. But, boundary conditions usually used with this equation, e.g. half Sommerfeld or Reynolds boundary conditions, cannot fulfill this natural law of conservation. In the case of connecting rod bearing, where applied load is dynamic and its magnitude is relatively large, such unrealistic boundary conditions have serious influence on calculation results, especially on lubricant flow rate or power disspation which are important parameters in thermal analysis. In this paper, mass-conserving boundary condition was applied in the finite element analysis of connecting rod bearings. Lubricant flow rate and power dissipation rate were calculated together with journal center locus, minimum film thickness and maxmium film pressure. These computation results were compared with those of the case of Reynolds boundary condition. Balance between inlet and outlet flow rate was well achieved in the case of mass-conserving boundary condition.

다공성 재생기의 방향성을 고려한 왕복유동 수치해석 (Numerical analysis in oscillating flow considering orientation of porous media regenerator)

  • 양문흠;박상진;노승탁
    • 대한기계학회논문집B
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    • 제21권12호
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    • pp.1668-1678
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    • 1997
  • Numerical analyses were performed to investigate the characteristics of regenerator in oscillating flow by using moving boundary method and Darcy model. In this work, periodic adiabatic boundary condition was suggested as the boundary condition of adiabatic part so that the effects of the thermal inertia of the wall could be considered. In carrying out numerical analyses, two models were applied and compared. One called isotropic model has the same thermal conductivity in radial and axial directions within a porous media. The other called aeolotropic model has different conductivity in each directions. Isotropic model could not show the advantage of energy reduction which needs to maintain constant wall temperature difference between heater and cooler. But aeolotropic model could simulate the reduction of energy consumption.

회전방향 온도변화를 갖는 매우 빠르게 회전하는 파이프 내의 기체유동 (Gas Flow in a Rapidly Rotating Pipe with Azimuthal-Varying Thermal Wall Condition)

  • 박준상;현재민
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2003년도 추계학술대회
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    • pp.628-633
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    • 2003
  • An analysis on the steady-state has been made of flow of a compressible fluid rapidly-rotating in a pipe. The flow is induced by an small arbitrary azimuthally-varying thermal forcing added on the basic state of rigid body isothermal rotation. The system Ekman number is assumed to be very small value. Analytic solutions have been obtained for axisymmetric and non-axisymmetric types, in which the axisymmetric solution comes from the azimuthally-averaged wall boundary condition and the non-axisymmetric solution from fluctuating wall boundary condition.

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내연기관 피스톤의 열부하 해석을 위한 경제조건 설정에 관한 연구 (A Study on Boundary Conditions of Piston Thermal Loading Analysis in Internal Combustion Engines)

  • 정동수;조용석;최헌오;이진형
    • 대한기계학회논문집
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    • 제12권3호
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    • pp.528-533
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    • 1988
  • 본 연구에서는 피스톤의 온도분포 및 열변형을 유한요소법에 의해 분석할 경 우 입력 데이타로 주어질 경계조건은 Li가 사용한 열저항 회로법을 근거로 하여 여기 에 경험치를 부여하는 방법으로 초기 설정치를 구하고, 또 전해질 탱크 상사법에 의한 실험적인 방법으로 결과를 구하여서 두 결과를 비교 검토하고자 한다.

점탄성 특성을 가진 폴리머용액의 난류유동 열적입구길이에 관한 실험적 연구 (An experimental study on the thermal entrance lengths for viscoelastic polymer solutions in turbulent tube flow)

  • 유상신;황태성;엄정섭
    • 대한기계학회논문집
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    • 제12권5호
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    • pp.1189-1196
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    • 1988
  • 본 연구에서는 내경이 각각 8.5mm와 10.3mm이며 무차원길이가 각각 710과 1158인 두 개의 시험관을 사용하는 유동장치를 제작하여 시험관 입구에서부터 유체역 학적 경계층(hydrodynamic boundary layer)과 열적 경계층(thermal boundary layer)이 동시에 발달하기 시작하는 경계조건을 형성하고 관벽에서 일정한 열 플럭스(constant heat flux)를 발생하는 조건을 부여하였다. 퇴화현상(degradation)에 대하여 비교적 안정성을 가진 폴리아크라마이드(polyacrylamide) Separan Ap273을 수도물에 용해하여 제조한 폴리머용액으로 유동특성과 열전달특성을 실험하여 열적입구길이와 열전달특성 을 규명하고자 한다.

Boundary layer measurements for validating CFD condensation model and analysis based on heat and mass transfer analogy in laminar flow condition

  • Shu Soma;Masahiro Ishigaki;Satoshi Abe;Yasuteru Sibamoto
    • Nuclear Engineering and Technology
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    • 제56권7호
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    • pp.2524-2533
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    • 2024
  • When analyzing containment thermal-hydraulics, computational fluid dynamics (CFD) is a powerful tool because multi-dimensional and local analysis is required for some accident scenarios. According to the previous study, neglecting steam bulk condensation in the CFD analysis leads to a significant error in boundary layer profiles. Validating the condensation model requires the experimental data near the condensing surface, however, available boundary layer data is quite limited. It is also important to confirm whether the heat and mass transfer analogy (HMTA) is still valid in the presence of bulk condensation. In this study, the boundary layer measurements on the vertical condensing surface in the presence of air were performed with the rectangular channel facility WINCS, which was designed to measure the velocity, temperature, and concentration boundary layers. We set the laminar flow condition and varied the Richardson number (1.0-23) and the steam volume fraction (0.35-0.57). The experimental results were used to validate CFD analysis and HMTA models. For the former, we implemented a bulk condensation model assuming local thermal equilibrium into the CFD code and confirmed its validity. For the latter, we validated the HMTA-based correlations, confirming that the mixed convection correlation reasonably predicted the sum of wall and bulk condensation rates.