Three Dimensional Numerical Simulation of the Natural Convection in an Annulus With an Internal Slotted Cylinder

2011 ◽  
Author(s):  
Mo Yang ◽  
Jin Wang ◽  
Kun Zhang ◽  
Ling Li ◽  
Yuwen Zhang
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Numerical Solutions ◽  
Three Dimensional ◽  
Convection Heat Transfer ◽  
Natural Convection Heat Transfer ◽  
Dimensional Model ◽  
Heat Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Rayleigh Numbers

Detailed numerical analysis is presented for three-dimensional natural convection heat transfer in annulus with an internal concentric slotted cylinder. The internal slotted cylinder and the outer annulus are maintained at uniform but different temperatures. Governing equations are discretized using control volume technique based on staggered grid formulation and solved using SIMPLE algorithm with QUICK scheme. Flow and heat transfer characteristics are investigated for a Rayleigh number range of 10 to 106 while Prandtl number (Pr) is taken to be 0.7. The results indicate, at Rayleigh numbers below 105, the system shows two dimensional flow and heat transfer characteristics. On the other hand, the flow and heat transfer shows three dimensional characteristics while for Rayleigh numbers greater than 5×105. Comparison with experimental results indicated that the numerical solutions by three dimensional model can obtain more accuracy than the numerical solutions by two dimensional model. Besides, Numerical results show that the average equivalent conductivity coefficient of natural convection heat transfer of this problem can be enhanced by as much as 30% while relative slot width is more than 0.1.

Natural Convection in a Partitioned Cubic Enclosure

1992 ◽  
Vol 114 (2) ◽  
pp. 410-417 ◽  
Author(s):  
K. C. Karki ◽  
P. S. Sathyamurthy ◽  
S. V. Patankar
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Numerical Solutions ◽  
Three Dimensional ◽  
The Other ◽  
Two Dimensional ◽  
Flow And Heat Transfer ◽  
Dimensional Simulation ◽  
Oriented Parallel ◽  
Rayleigh Numbers

Numerical solutions are obtained for fluid flow and heat transfer in a cubic enclosure with a vertical adiabatic partition. The two zones of the enclosure are connected by a single rectangular opening. The partition is oriented parallel to the isothermal sidewalls, one of which is heated and the other cooled while the remaining walls are adiabatic. Results have been presented for air for the Rayleigh numbers in the range 104−107. The width of the opening is held fixed while the height, relative to the enclosure height, is varied from 0.25 to 0.75. The effects of various parameters on the flow structure and heat transfer are investigated. The results of the three-dimensional simulation have also been compared with those for the corresponding two-dimensional configurations.

Pseudosteady-State Natural Convection Inside Spheres

1975 ◽  
Vol 97 (1) ◽  
pp. 54-59 ◽  
Author(s):  
M. Y. Chow ◽  
R. G. Akins
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Driving Force ◽  
Numerical Solutions ◽  
Convection Heat Transfer ◽  
Flow Patterns ◽  
Natural Convection Heat Transfer ◽  
Constant Flow ◽  
Convection Heat ◽  
Rayleigh Numbers

Natural convection heat transfer to water contained within five different sized spheres was studied. Pseudosteady-state was maintained by keeping the driving force for convection constant, i.e., the temperature outside the sphere was increased steadily so that the temperature difference between the outside and the center remained constant. Flow visualization was used to determine flow patterns within the spheres. Laminar flow was found to exist below Rayleigh numbers of about 107. The flow patterns along with the position of the circulation centers are presented and compared with recent numerical solutions. The overall heat transfer in the laminar region was fitted by least squares and the following correlation obtained: Nu=0.80Ra0.30

Natural Convection Heat Transfer of Water Within a Horizontal Cylindrical Annulus With Density Inversion Effects

1983 ◽  
Vol 105 (1) ◽  
pp. 117-123 ◽  
Author(s):  
P. Vasseur ◽  
L. Robillard ◽  
B. Chandra Shekar
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Numerical Solutions ◽  
Cold Water ◽  
Freezing Point ◽  
Convection Heat Transfer ◽  
Natural Convection Heat Transfer ◽  
Convection Heat ◽  
Density Inversion ◽  
Cylindrical Annulus

The effect of density inversion on steady natural convection heat transfer of cold water, between two horizontal concentric cylinders of gap width, L, is studied numerically. Water near its freezing point is characterized by a density maximum at 4°C. Numerical solutions are obtained for cylinders with nonlinear Rayleigh numbers RA ranging from 2 × 103 to 7.6 × 104, a radius ratio 1.75 ≤ ra ≤ 2.6 and an inversion parameter γ, relating the temperature for maximum density with the cavity wall temperatures, between −2 and 2. The results obtained are presented graphically in the form of streamline and isotherm contour plots. The heat transfer characteristics, velocity profiles, and local and overall Nusselt numbers are studied. The results of the present study were found qualitatively valid when compared with an experimental investigation carried out in the past.

Natural Convection Heat Transfer Phenomena in Packed Bed Systems

2014 ◽  
Author(s):  
Olugbenga O. Noah ◽  
Johan F. Slabber ◽  
Josua P. Meyer
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Thermal Energy ◽  
Unit Volume ◽  
Convection Heat Transfer ◽  
Natural Convection Heat Transfer ◽  
Convection Heat ◽  
Heat Transfer Characteristics ◽  
Coated Particles ◽  
Transfer Characteristics

Natural convection heat transfer in fluid-saturated porous media has in recent years gained considerable attention especially in High Temperature Reactors (HTR). It is lately proposed that Light Water Reactors (LWT) can be made safer by re-designing the fuel in the fuel assembly. In the proposed design, porous medium containing fuel in the form of loose coated particles in a Helium environment is introduced inside the cladding tubes of the fuel elements. These coated particles are treated as a bed from where heat is transferred to the cladding tube and the gas movement is due to natural convection. This proposal will require an understanding of the heat transfer characteristics from heated particles fuel to the gas atmosphere within the cladding tubes. In this present study, the natural convection heat transfer characteristics in packed beds from fluid-to-particle and bed particles to helium gas (thermal energy storage system) was experimentally investigated. Medium condition in this study was homogenous, isotropic, negligible radiant heat transfer and at local thermal non-equilibrium (LTNE). Theoretical formulation of microscopic thermal energy balance in the medium was employed in the analysis of experimental data. This formulation accounts for the convective heat transfer coefficient, the net rate of heat conduction into a unit volume of the solid and the heat production per unit volume of the particle. Dimensionless parameters like the Nusselt, Grashof, Prandtl, Rayleigh and Biot numbers defining heat transfer effect in the medium were equally determined and results validated with the KTA correlation.

Three-Dimensional Laminar Natural Convection in an Inclined Air Slot With Hexagonal Honeycomb Core

1991 ◽  
Vol 113 (4) ◽  
pp. 906-911 ◽  
Author(s):  
Y. Asako ◽  
H. Nakamura ◽  
Z. Chen ◽  
M. Faghri
Keyword(s):  
Natural Convection ◽  
Numerical Solutions ◽  
Transfer Problem ◽  
Three Dimensional ◽  
Convection Heat Transfer ◽  
Temperature Fields ◽  
Honeycomb Core ◽  
Inclination Angles ◽  
Side Walls ◽  
Rayleigh Numbers

Numerical solutions are obtained for a three-dimensional natural convection heat transfer problem in an inclined air slot with a hexagonal honeycomb core. The air slot is assumed to be long and wide such that the velocity and temperature fields repeat themselves in successive enclosures. The numerical methodology is based on an algebraic coordinate transformation technique, which maps the complex cross section onto a rectangle, coupled with a calculation procedure for fully elliptic three-dimensional flows. The calculations are performed for Rayleigh numbers in the range of 103 to 105, inclination angles in the range of −90 to 80 deg, Prandtl number of 0.7, and for five values of the aspect ratio. Three types of thermal boundary condition for the honeycomb side walls are considered. The average Nusselt number results are compared with those for a rectangular two-dimensional enclosure.

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