Three-Dimensional Study of Combined Conduction, Radiation, and Natural Convection From Discrete Heat Sources in a Horizontal Narrow-Aspect-Ratio Enclosure

1999 ◽  
Vol 121 (4) ◽  
pp. 992-1001 ◽  
Author(s):  
V. H. Adams ◽  
Y. Joshi ◽  
D. L. Blackburn
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Aspect Ratio ◽  
Three Dimensional ◽  
Thermal Conductance ◽  
Flow Characteristics ◽  
Convection Flow ◽  
Heat Sources ◽  
Length Width ◽  
Horizontal Substrate

Three-dimensional natural convection flow and heat transfer were numerically studied for a three-by-three array of discrete protruding heat sources on a horizontal substrate in an air-filled, rectangular, narrow-aspect-ratio enclosure with length, width, and height ratio of 6:6:1. The governing equations for natural convection in air, coupled with conjugate conduction and radiation within the enclosure were solved using a finite volume method. The study examines the complex thermal interactions between the heat sources, substrate, and enclosure walls as affected by the thermal conductance of the walls and substrate with the intent of determining which physical effects and level of detail are necessary to accurately predict thermal behavior of discretely heated enclosures. The influence of radiation on the overall heat transfer is given particular attention. The three-dimensionality of the problem was evident in the overall flow characteristics and in the convective heat transfer edge effects on the heat source surfaces. Excellent agreement between temperature predictions on the heat sources and substrate and experimental measurements was obtained for modified Rayleigh numbers in the range of 9.7 × 105 to 1.6 × 107.

Three-Dimensional Steady and Oscillatory Natural Convection in a Rectangular Enclosure With Heat Sources

2016 ◽  
Vol 138 (9) ◽  
Author(s):  
Amin Bouraoui ◽  
Rachid Bessaïh
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Numerical Study ◽  
Three Dimensional ◽  
Air Cooling ◽  
Heat Sources ◽  
Rectangular Enclosure ◽  
Aspect Ratios ◽  
Simpler Algorithm ◽  
Strong Relation

In this paper, a numerical study of three-dimensional (3D) natural convection air-cooling of two identical heat sources, simulating electronic components, mounted in a rectangular enclosure was carried out. The governing equations were solved by using the finite-volume method based on the SIMPLER algorithm. The effects of Rayleigh number Ra, spacing between heat sources d, and aspect ratios Ax in x-direction (horizontal) and Az in z-direction (transversal) of the enclosure on heat transfer were investigated. In steady state, when d is increased, the heat transfer is more important than when the aspect ratios Ax and Az are reduced. In oscillatory state, the critical Rayleigh numbers Racr for different values of spacing between heat sources and their aspect ratios, at which the flow becomes time dependent, were obtained. Results show a strong relation between heat transfers, buoyant flow, and boundary layer. In addition, the heat transfer is more important at the edge of each face of heat sources than at the center region.

Effects of the Heat Transfer at the Side Walls on Natural Convection in Cavities

1990 ◽  
Vol 112 (2) ◽  
pp. 370-378 ◽  
Author(s):  
Y. Le Peutrec ◽  
G. Lauriat
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Numerical Solutions ◽  
Three Dimensional ◽  
Thermal Conductance ◽  
Fluid Flows ◽  
Heat Losses ◽  
Transfer Rates ◽  
Side Walls ◽  
The Difference

Numerical solutions are obtained for fluid flows and heat transfer rates for three-dimensional natural convection in rectangular enclosures. The effects of heat losses at the conducting side walls are investigated. The problem is related to the design of cavities suitable for visualizing the flow field. The computations cover Rayleigh numbers from 103 to 107 and the thermal conductance of side walls ranging from adiabatic to commonly used glazed walls. The effect of the difference between the ambient temperature and the average temperature of the two isothermal walls is discussed for both air and water-filled enclosures. The results reported in the paper allow quantitative evaluations of the effects of heat losses to the surroundings, which are important considerations in the design of a test cell.

A comprehensive review on natural convection flow and heat transfer

2019 ◽  
Vol 29 (3) ◽  
pp. 834-877 ◽  
Author(s):  
Alireza Rahimi ◽  
Ali Dehghan Saee ◽  
Abbas Kasaeipoor ◽  
Emad Hasani Malekshah
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Industrial Applications ◽  
Convection Flow ◽  
Heat Sources ◽  
Comprehensive Review ◽  
Content Type ◽  
Thermal Boundary Conditions ◽  
Flow And Heat Transfer ◽  
Different Types

PurposeThe purpose of this paper is to carry out a comprehensive review of some latest studies devoted to natural convection phenomenon in the enclosures because of its significant industrial applications.Design/methodology/approachGeometries of the enclosures have considerable influences on the heat transfer which will be important in energy consumption. The most useful geometries in engineering fields are treated in this literature, and their effects on the fluid flow and heat transfer are presented.FindingsA great variety of geometries included with different physical and thermal boundary conditions, heat sources and fluid/nanofluid media are analyzed. Moreover, the results of different types of methods including experimental, analytical and numerical are obtained. Different natures of natural convection phenomenon including laminar, steady-state and transient, turbulent are covered. Overall, the present review enhances the insight of researchers into choosing the best geometry for thermal process.Originality/valueA comprehensive review on the most practical geometries in the industrial application is performed.

Aspect Ratio Effect on Natural Convection Flow in a Cavity Submitted to a Periodical Temperature Boundary

2006 ◽  
Vol 129 (8) ◽  
pp. 1060-1068 ◽  
Author(s):  
Nader Ben Cheikh ◽  
Brahim Ben Beya ◽  
Taieb Lili
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Aspect Ratio ◽  
Vertical Wall ◽  
Heated Wall ◽  
Convection Flow ◽  
Natural Convection Flow ◽  
Temperature Boundary ◽  
Shallow Cavities ◽  
Periodic Temperature

The effect of aspect ratio on natural convection flow in a cavity submitted to periodic temperature boundary, is investigated numerically. The temperature of the heated wall is either maintained constant or varied sinusoidally with time while the temperature of the opposite vertical wall is maintained constant. The results are given for a range of varied parameters as Rayleigh number (5×103⩽Ra⩽106), cavity aspect ratio (1∕6⩽A⩽8), and period of the sinusoidally heated wall (1⩽τ⩽1600). The amplitude of oscillation (a=0.8) and the Prandtl number (Pr=0.71) were kept constant. The results obtained in the steady state regime show that the heat transfer averaged over the cold wall is maximum when the aspect ratio is in the range 1⩽A⩽2. In the case of a periodic temperature boundary, it is shown that the deviation between the mean heat transfer and the heat transfer of the constant heated case is larger for shallow cavities.

scholarly journals Intensification of Heat Transfer in Cavity Partially Heated and Filled with Nanofluid (Cu-Water)

2015 ◽  
Vol 55 ◽  
pp. 173-179
Author(s):  
Ridha Jmai ◽  
Brahim Ben Beya ◽  
Taieb Lili
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Natural Convection ◽  
Aspect Ratio ◽  
Heat Transfer Rate ◽  
Finite Volume ◽  
Transfer Rate ◽  
Heat Sources ◽  
Flow And Heat Transfer ◽  
Vertical Walls

Natural convection in a rectangular cavity with aspect ratio (Ax), partially heated and filled with a nanofluid (Cu-Water) has been studied numerically. Two heat sources with length (B) are placed on the opposite vertical walls; the remainder of the walls is maintained adiabatic while the horizontal walls are brought to a cold temperature. The equations governing the flow are solved using a finite volume home code using a multigrid technique. Among the parameters governing the flow, a detailed study on the effects of the aspect ratio (Ax) and the length of the source (B) on flow and heat transfer rate is given. The results are shown in terms of streamlines and isotherms. It was found that the transfer of heat significantly increases with the aspect ratio (Ax) and the length of the source (B). A correlation expressing the Nusselt number as a function of (Ax) and d is established.

Numerical investigation of Rayleigh-Benard Natural convection and entropy generation in a cubic cavity with discrete heat sources

2021 ◽  
pp. 1-9
Author(s):  
Chemseddine Maatki ◽  
Kaouther Ghachem ◽  
Mohammed A. Almeshaal ◽  
Nidhal Ben Khedher ◽  
Lioua Kolsi
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Heat Transfer Rate ◽  
Entropy Generation ◽  
Transfer Rate ◽  
Three Dimensional ◽  
Heat Sources ◽  
Discrete Heat Sources ◽  
Dimensional Distribution ◽  
Volume Method

Abstract The Three-dimensional natural convection with isothermal discrete heat sources in a cubical cavity has been carefully studied using the 3D vector potential-vorticity formulation. Based on the finite volume method, the governing equations are solved with a home-made computational code (written in Fortran). Assuming that all cavity vertical walls are adiabatic, the upper wall of the cavity is kept at a cold temperature. However, in the bottom face, heat sources are placed under different configurations. The size of the discrete sources, their positions, and their numbers are varied for different Rayleigh numbers. The Prandtl number is fixed at 0.71. Three-dimensional distribution of the temperature iso-surfaces, the heat transfer rate, and entropy generation are evaluated. It is found that heat transfer and entropy generation are strongly affected by the arrangement of the discrete heated sources. In conclusion, the heat transfer rate is maximized, and the entropy generation is minimized for the inline arrangement of more than two heaters compared to the diagonal one.

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