The Effects of Property Variations on Natural Convection in a Square Enclosure

1999 ◽  
Vol 121 (1) ◽  
pp. 57-62 ◽  
Author(s):  
A. F. Emery ◽  
J. W. Lee
Keyword(s):  
Natural Convection ◽  
Constant Heat Flux ◽  
Variable Properties ◽  
Temperature Dependent ◽  
Constant Heat ◽  
Square Enclosure ◽  
Average Temperature ◽  
Temperature Dependent Conductivity ◽  
Vertical Walls ◽  
Prandtl Numbers

Natural convection in a square enclosure with heated vertical walls and temperature-dependent conductivity and viscosity was simulated for Prandtl numbers ranging from 0.01 to 1.0 and Ra ≤ 106. Although the variable properties produced observable changes in the the temperatures and velocities, the overall heat transfer, as represented by the Nusselt number, was found to be unaffected and was accurately correlated in terms of the Rayleigh and Prandtl numbers using Nu=0.185Ra00.278Pr00.089 with properties evaluated at the average temperature. This correlation applies to both isothermal and constant heat flux hot walls.

Thermoconvective Motion of Low Prandtl Number Fluids Within a Horizontal Cylindrical Annulus

1977 ◽  
Vol 99 (4) ◽  
pp. 596-602 ◽  
Author(s):  
J. R. Custer ◽  
E. J. Shaughnessy
Keyword(s):  
Heat Flux ◽  
Natural Convection ◽  
Prandtl Number ◽  
Perturbation Expansion ◽  
Constant Heat Flux ◽  
Basic Flow ◽  
Constant Heat ◽  
Grashof Number ◽  
Cylindrical Annulus ◽  
Prandtl Numbers

Steady natural convection in very low Prandtl number fluids is investigated using a double perturbation expansion in powers of the Grashof and Prandtl numbers. The fluid is contained in a horizontal cylindrical annulus, the walls of which either are held at constant temperature or support a constant heat flux. In both cases the evolution of the flow for increasing Grashof number is of interest. It is found that the basic flow pattern consists of one eddy. For both boundary conditions the center of this eddy falls into the lower half of the annulus as the Grashof number increases. Such behavior is directly opposite to experimental results obtained in fluids of higher Prandtl number.

Effects of Viscous Dissipation and Radiation on MHD Natural Convection in Oblique Porous Cavity with Constant Heat Flux

2017 ◽  
Vol 9 (2) ◽  
pp. 463-484 ◽  
Author(s):  
Ammar I. Alsabery ◽  
Habibis Saleh ◽  
Ishak Hashim
Keyword(s):  
Heat Flux ◽  
Natural Convection ◽  
Viscous Dissipation ◽  
Inclination Angle ◽  
Hartmann Number ◽  
Constant Heat Flux ◽  
Governing Equations ◽  
Constant Heat ◽  
Left Wall ◽  
Porous Cavity

AbstractEffects of viscous dissipation and radiation on MHD natural convection in oblique porous cavity with constant heat flux is studied numerically in the present article. The right inclined wall is maintained at a constant cold temperatureTcand the left inclined wall has a constant heat fluxqwith lengthS, while the remainder of the left wall is adiabatic. The horizontal walls are assumed to be adiabatic. The governing equations are obtained by applying the Darcy model and Boussinesq approximations. COMSOL's finite element method is used to solve the non-dimensional governing equations together with specified boundary conditions. The governing parameters of this study are Rayleigh number (Ra=10,100,200,250,500 and 1000), Hartmann number (0≤Ha≤20), inclination angle of the magnetic field (0° ≤ω≤π/2), Radiation (0≤R≤15), the heater flux length (0.1≤H≤1) and inclination angle of the sloping wall (–π/3≤ϕ≤π/3). The results are considered for various values of the governing parameters in terms of streamlines, isotherms and averageNusselt number. It is found that the intensity of the streamlines and the isotherm patterns decrease with an increment in Hartmann number. The overall heat transfer is significantly increased with the increment of the viscous dissipation and the radiation parameters.

Three-Dimensional Numerical Analysis for Convection of Air in a Bore Space of a Superconducting Magnet

2003 ◽  
Author(s):  
G. Tomita ◽  
M. Kaneda ◽  
T. Tagawa ◽  
H. Ozoe
Keyword(s):  
Magnetic Field ◽  
Heat Flux ◽  
Natural Convection ◽  
Numerical Analysis ◽  
Strong Magnetic Field ◽  
Three Dimensional ◽  
Superconducting Magnet ◽  
Constant Heat Flux ◽  
Constant Heat ◽  
Magnetizing Force

Three-dimensional numerical computations were carried out for the natural convection of air in a horizontal cylindrical enclosure in a magnetic field, which is modeled for a bore space of a horizontal superconducting magnet. The enclosure was cooled from the circumferential sidewall at the constant heat flux and vertical end walls were thermally insulated. A strong magnetic field was considered by a one-turn electric coil with the concentric and twice diameter of the cylinder. Without a magnetic field, natural convection occurs along the circumferential sidewall. When a magnetic field was applied, magnetizing force induced the additional convection, that is, the cooled air at the circumferential wall was attracted to the location of a coil. Consequently, the temperature around the coil decreased extensively.

Numerical Study of Three-Dimensional Oscillatory Natural Convection at Low Prandtl Number in Rectangular Enclosures

2000 ◽  
Vol 123 (1) ◽  
pp. 77-83 ◽  
Author(s):  
Shunichi Wakitani
Keyword(s):  
Natural Convection ◽  
Prandtl Number ◽  
Numerical Study ◽  
Three Dimensional ◽  
Width Ratio ◽  
Three Dimensional Flow ◽  
Longitudinal Vortices ◽  
Aspect Ratios ◽  
Vertical Walls ◽  
Prandtl Numbers

Numerical investigations are presented for three-dimensional natural convection at low Prandtl numbers (Pr) from 0 to 0.027 in rectangular enclosures with differentially heated vertical walls. Computations are carried out for the enclosures with aspect ratios (length/height) 2 and 4, and width ratios (width/height) ranging from 0.5 to 4.2. Dependence of the onset of oscillation on the Prandtl number, the aspect ratio, and the width ratio is investigated. Furthermore, oscillatory, three-dimensional flow structure is clarified. The structure is characterized by some longitudinal vortices (rolls) as well as cellular pattern.

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