scholarly journals Numerical two-dimensional natural convection in an air filled square enclosure, tilted (25° and 65°) in relation to the horizontal plane, heated from two opposite sides for rayleigh numbers ranging between 103 and 2.106

2010 ◽  
Vol 16 (3) ◽  
Author(s):  
F.P Kieno ◽  
A Ouedraogo
Keyword(s):  
Natural Convection ◽  
Horizontal Plane ◽  
Two Dimensional ◽  
Square Enclosure ◽  
Rayleigh Numbers

scholarly journals Classification of Flow Modes for Natural Convection in a Square Enclosure with an Eccentric Circular Cylinder

Energies ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2788
Author(s):  
Hyun-Sik Yoon ◽  
Yoo-Jeong Shim
Keyword(s):  
Natural Convection ◽  
Rayleigh Number ◽  
Circular Cylinder ◽  
Flow Structures ◽  
Two Dimensional ◽  
Square Enclosure ◽  
Wide Range ◽  
Secondary Vortices ◽  
Rayleigh Numbers

The present study investigated the natural convection for a hot circular cylinder embedded in a cold square enclosure. The numerical simulations are performed to solve a two-dimensional steady natural convection for three Rayleigh numbers of 103, 104 and 105 at a fixed Prandtl number of 0.7. This study considered the wide range of the inner cylinder positions to identify the eccentric effect of the cylinder on flow and thermal structures. The present study classifies the flow structures according to the cylinder position. Finally, the present study provides the map for the flow structures at each Rayleigh number (Ra). The Ra = 103 and 104 form the four modes of the flow structures. These modes are classified by mainly the large circulation and inner vortices. When Ra = 105, one mode that existed at Ra = 103 and 104, disappears in the map of the flow structures. The new three modes appear, resulting in total six modes of flow structures at Ra = 105. New modes at Ra = 105 are characterized by the top side secondary vortices. The corresponding isotherms are presented to explain the bifurcation of the flow structure.

Lattice Boltzmann Computations of Natural Convection Heat Transfer of Nanofluid in a Square Cavity Heated by Protruding Heat Source

2020 ◽  
Vol 12 (4) ◽  
Author(s):  
Mustapha Faraji ◽  
El Mehdi Berra
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Heat Source ◽  
Inclination Angle ◽  
Lattice Boltzmann ◽  
Base Fluid ◽  
Numerical Code ◽  
Convection Flow ◽  
Square Enclosure ◽  
Rayleigh Numbers

Abstract This paper reported the mathematical modeling and numerical simulation of natural convection flow of Cu/water nanofluid in a square enclosure using the lattice Boltzmann method (LBM). The cavity is heated from below by heat source and cooled by the top wall. The vertical walls are adiabatic. After validating the numerical code against the numerical and experimental data, simulations were performed for different Rayleigh numbers (104–0.5 × 107), nanoparticles volume fractions (0–8%), and cavity inclination angle (0 deg–90 deg). The effects of the studied parameters on the streamlines, on isotherms distributions within the enclosure, and on the local and average Nusselt numbers are investigated. It was found that heat transfer and fluid flow structure depend closely on the nanoparticle concentration. Results show differences in stream separation between a base fluid and the nanofluid. Also, adding small nanoparticles fractions, less than 6%, to the base fluid enhances the heat transfer for higher Rayleigh numbers and cavity inclination angle less than 30 deg. It is concluded that the optimal dilute suspension of copper nanoparticles can be applied as a passive way to enhance heat transfer in natural convection engineering applications.

Natural Convection Liquid Cooling of a Substrate-Mounted Protrusion in a Square Enclosure: A Parametric Study

1992 ◽  
Vol 114 (2) ◽  
pp. 401-409 ◽  
Author(s):  
S. B. Sathe ◽  
Y. Joshi
Keyword(s):  
Natural Convection ◽  
Boundary Conditions ◽  
Flow Behavior ◽  
Air Cooling ◽  
Square Enclosure ◽  
Simple Boundary ◽  
Wide Range ◽  
Solid Region ◽  
Rayleigh Numbers ◽  
Thermal Conductivities

The coupled conduction and natural convection transport from a substrate-mounted heat generating protrusion in a liquid-filled square enclosure is numerically examined. The governing steady two-dimensional equations are solved using a finite-difference method for a wide range of Rayleigh numbers, protrusion thermal conductivities and widths, substrate heights, and enclosure boundary conditions. The results presented apply to liquids with 10≤Pr≤1000. It was established that in many situations it may be inappropriate to specify simple boundary conditions on the solid surface and decouple the conduction within the substrate or the protrusion. Higher Rayleigh numbers, protrusion thermal conductivities, and widths enhanced cooling. A variation in the substrate height did not affect the maximum protrusion temperature; however, the flow behavior was considerably altered. An empirical correlation for the maximum protrusion temperature was developed for a wide range of parametric values. The enclosure thermal boundary conditions changed the heat transfer in the solid region to only a small extent. Immersion cooling in common dielectric liquids was shown to be advantageous over air cooling only if the thermal conductivity of the protrusion was larger than that of the liquid.

Combined Radiation-Convection in Gray Fluids Enclosed in Vertical Cavities

1982 ◽  
Vol 104 (4) ◽  
pp. 609-615 ◽  
Author(s):  
G. Lauriat
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Natural Convection ◽  
Thermal Radiation ◽  
Two Dimensional ◽  
Flow And Heat Transfer ◽  
Rayleigh Numbers

The interaction of thermal radiation with natural convection in a gray fluid contained inside a cavity is numerically examined. The radiation part of the problem is treated by using the two-dimensional P-1 approximation. The effect of radiation on the conduction, transition, and boundary layer regimes is investigated. The results show that radiation decreases the intensity of the flow at low Rayleigh numbers and, in contrast, leads to an increased flow in convection regimes. The influence of the radiative parameters on the flow and heat transfer is discussed.

scholarly journals Numerical Investigation for the Modeling of the Magnetic Buoyancy Force during the Natural Convection of Air in a Square Enclosure

2014 ◽  
Vol 6 ◽  
pp. 873260 ◽  
Author(s):  
Kewei Song ◽  
Toshio Tagawa ◽  
Liang-bi Wang ◽  
Hiroyuki Ozoe
Keyword(s):  
Magnetic Field ◽  
Natural Convection ◽  
Buoyancy Force ◽  
Nonuniform Magnetic Field ◽  
Temperature Fields ◽  
Two Dimensional ◽  
Numerical Computations ◽  
Square Enclosure ◽  
Magnetic Buoyancy ◽  
Magnetizing Force

Numerical computations are carried out for natural convection of air in a two-dimensional square enclosure under a nonuniform magnetic field and together with the gravity field. The nonuniform magnetic field is supplied by a cubic permanent magnet placed above the enclosure. Two kinds of the expressions for the magnetizing force are considered and compared in the numerical computations. The flow and temperature fields, the magnetizing force field and the Nusselt number for two kinds of magnetizing force expressions are all presented in this paper. The numerical results reveal that the natural convection inside the enclosure does not depend on the types of the expressions for magnetizing force.

An Experimental Study on Natural Convection Heat Transfer in an Inclined Square Enclosure Containing Internal Energy Sources

1988 ◽  
Vol 110 (2) ◽  
pp. 345-349 ◽  
Author(s):  
Jae-Heon Lee ◽  
R. J. Goldstein
Keyword(s):  
Natural Convection ◽  
Internal Energy ◽  
Extreme Values ◽  
Convection Heat Transfer ◽  
Energy Sources ◽  
Square Enclosure ◽  
Nusselt Numbers ◽  
Inclination Angles ◽  
The Right ◽  
Rayleigh Numbers

An experiment was carried out to study two-dimensional laminar natural convection within an inclined square enclosure containing fluid with internal energy sources bounded by four rigid planes of constant equal temperature. Inclination angles, from the horizontal, of 0, 15, 30, and 45 deg for Rayleigh numbers from 1.0 × 104 to 1.5 × 105 were studied. At inclined angles of 0 and 15 deg, there are two extreme values of temperature and temperature gradient within the fluid, while there is only one at 30 and 45 deg. Local and average Nusselt numbers are obtained on all four walls. As the inclination angle increases, the average Nusselt number increases on the right (upper) and bottom walls, decreases on the left (lower) wall and stays almost constant on the top wall.

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