• 태양에너지
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• 제12권2호
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• pp.28-42
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• 1992

This investigation is carried out numerically for the two dimensional natural convection and surface radiation heat transfer in a square enclosure. The bottom wall is a constant heat flux at hot temperature and also top wall is isothermal at cold temperature whereas the left and right side walls are adiabatic except a transparent window on the right side partially. The exchange of radiant energy is obtained by the net radiation method and the shape factor by the crossed string method. The change in temperature and Nusselt number distributions of the walls due to the effect of the wall emissivity for various emissivities and for various dimensionless insolation energies are investigated. The dimensionless local convective heat flux and local radiative heat flux distributions in the wall except an adiabatic wall are also compared.

• 대한기계학회논문집B
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• 제22권1호
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• pp.79-92
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• 1998

A numerical study has been performed to obtain the air-side flow and heat transfer characteristics for a two-row lanced finned tube heat exchanger with 7 mm tube outer diameter. The increases of dimensionless local heat flux at the leading edge of slit and bottom surface of the fin were noticed. The temperature of air at downstream of the 2nd row of the lanced fin becomes more uniform than that of the plain fin because the mixing of energy increases by the slit and the side-slit. As the inlet velocity increases, the contribution of the 1st row to heat transfer decreases and that of 2nd row increases.

• 대한기계학회논문집
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• 제12권2호
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• pp.338-348
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• 1988

본 연구는 환상휜에서 휜 바탕의 온도가 조기적으로 변화할 때, 휜 바탕의 온도가 주기적으로 변화할 때, 휜 주변 뿐만 아니라 휜 선단에서의 대류현상을 고려한 과도 전열에 대한 해석이다.

• 대한기계학회논문집B
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• 제24권4호
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• pp.519-525
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• 2000

The effect of nozzle diameter on the local Nusselt number distributions has been investigated for an axisymmetric turbulent jet impinging on the flat plate surface. The flow at the nozzle exit has a fully developed velocity profile. A uniform heat flux boundary condition at the plate surface was created using gold film Intrex. Liquid Crystal was used to measure the plate surface temperature. The experiments were made for the jet Reynolds number (Re) 23,000, the dimensionless nozzle to surface distance (L/d) from 2 to 14, and the nozzle diameter (d) from 1.36 to 3.40 cm. The results show that the Nusselt number at and near the stagnation point increase with an increasing value of the nozzle diameter.

• Journal of Computational Design and Engineering
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• 제3권4호
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• pp.330-336
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• 2016

The present work is concerned with heat and mass transfer of an electrically conducting second grade MHD fluid past a semi-infinite stretching sheet with convective surface heat flux. The analysis accounts for thermophoresis and thermal radiation. A similarity transformations is used to reduce the governing equations into a dimensionless form. The local similarity equations are derived and solved using Nachtsheim-Swigert shooting iteration technique together with Runge-Kutta sixth order integration scheme. Results for various flow characteristics are presented through graphs and tables delineating the effect of various parameters characterizing the flow. Our analysis explores that the rate of heat transfer enhances with increasing the values of the surface convection parameter. Also the fluid velocity and temperature in the boundary layer region rise significantly for increasing the values of thermal radiation parameter.

• 태양에너지
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• 제15권2호
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• pp.47-64
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• 1995

등열유속상태(等熱流速狀態)를 유지(維持)하고 있는 수평 전열판이 회전하고 있을 때, 여기에 수분류가 충돌(衝突)할 경우의 열전달특성을 실험적으로 연구했다. 노즐직경(直經)과 전열면간(傳熱面間)의 거리(距離)를 일정(一定)하게 유지하고, 분류(噴流)레이놀즈수(數)와 회전(回轉)레이놀즈수(數)를 변화시키면서 이의 영향을 살펴보았다. 실험결과, 국소(局所)Nusselt수(數)를 국소회전(局所回轉)레이놀즈수(數), 분류(噴流)레이놀즈수(數), 분류(噴流)프란틀수(數), 무차원반경(無次元半徑)의 함수로 나타내었다.

• 대한기계학회논문집B
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• 제21권4호
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• pp.579-588
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• 1997

The heat transfer and flow measurements from a convex curved surface to a circular impinging jet have been made. The flow at the nozzle exit has a fully developed velocity profile. The jet Reynolds number (Re) ranges from 11,000 to 50,000, the dimensionless nozzle-to-surface distance (L/d) from 2 to 10, and the dimensionless surface curvature (d/D) from 0.034 to 0.089. The results show that the stagnation point Nusselt number (N $u_{st}$ ) increases with increasing value of d/D. The maximum Nusselt number at the stagnation point occurs at L/d .ident. 6 to 8 for all Re's and d/D's tested. For larger L/d, N $u_{st}$ dependency on Re is stronger due to an increase of turbulence in the approaching jet as a result of the more active exchange of momentum with a surrounding air. The local Nusselt number decreases monotonically from its maximum value at the stagnation point. However, for L/d=2 and Re=23,000, and for L/d.leq.4 and Re=50,000, the stream wise Nusselt number distributions exhibit secondary maxima at r/d .ident. 2.2. The formation of the secondary maxima is attributed to an increase in the turbulence level resulting from the transition from a laminar to a turbulent boundary layer.ndary layer.

• 대한기계학회논문집B
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• 제23권2호
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• pp.243-253
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• 1999

The dual reciprocity boundary element method (DRBEM) is used to solve the Graetz problem of laminar flow inside circular duct. In this method the domain integral tenn of boundary integral equation resulting from source term of governing equation is transformed into equivalent boundary-only integrals by using the radial basis interpolation function, and therefore complicate domain discretization procedure Is completely removed. Velocity profile is obtained by solving the momentum equation first and then, using this velocities as Input data, energy equation Is solved to get the temperature profile by advancing from duct entrance through the axial direction marching scheme. DRBEM solution is tested for the uniform temperature and heat flux boundary condition cases. Local Nusselt number, mixed mean temperature and temperature profile inside duct at each dimensionless axial location are obtained and compared with exact solutions for the accuracy test Solutions arc in good agreement at the entry region as well as fully developed region of circular duct, and their accuracy are verified from error analysis.

• Journal of Mechanical Science and Technology
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• 제20권1호
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• pp.158-166
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• 2006

Extended Graetz problem in microtube is analyzed by using eigenfunction expansion to solve the energy equation. For the eigenvalue problem we applied the shooting method and Galerkin method. The hydrodynamically isothermal developed flow is assumed to enter the microtube with uniform temperature or uniform heat flux boundary condition. The effects of velocity and temperature jump boundary condition on the microtube wall, axial conduction and viscous dissipation are included. From the temperature field obtained, the local Nusselt number distributions on the tube wall are obtained as the dimensionless parameters (Peclet number, Knudsen number, Brinkman number) vary. The fully developed Nusselt number for each boundary condition is obtained also in terms of these parameters.

• Journal of applied mathematics & informatics
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• 제41권5호
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• pp.1085-1102
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• 2023

In this study the magneto hydrodynamic (MHD) micro polar fluid flow of a viscous incompressible fluid past a porous medium in the presence of chemical reaction is considered. This work is devoted to investigate the Soret effect and Electromagnetic radiation effect and analyze analytically. In the energy equation the applied magnetic field strength and in the concentration equation the Soret effect are incorporated. The basic PDE (partial differential equations) are reduced to ODE (ordinary differential equations) using non dimensional variables. Then the analytical solution of the dimensionless equations are found using perturbation technique. The features of the fluid flow parameters are analyzed, discussed and explained graphically. The graphical solutions are found using MATLAB R2019b. Skin friction coefficient at the wall, Couple stress coefficient at the plate and the local surface heat flux are also thoroughly examined. Overall, this study sheds light on the complex interplay between physical parameters in the behavior of MHD micro-polar fluid past a porous medium in the presence of chemical reaction.