Natural Convection in a Vertical Cavity Partially Filled With Porous Medium: Effect of Aspect Ratio, Darcy and Fluid Rayleigh Numbers

Volume 1 ◽  
2004 ◽  
Author(s):  
Sushant Anand ◽  
R. C. Arora
Keyword(s):  
Porous Medium ◽  
Natural Convection ◽  
Aspect Ratio ◽  
Saturated Porous Medium ◽  
Darcy Number ◽  
Medium Effect ◽  
Staggered Grid ◽  
Medium Increase ◽  
Diffusive Fluxes ◽  
Volume Method

Numerical investigation of natural convection in a rectangular cavity partially filled with fluid-saturated porous medium has been carried out. Rayleigh number (104 to 107) and Darcy Number (10−1 to 10−10), Aspect Ratio (0.75, 1.0, and 1.25) are considered parameters. The governing equations have been solved numerically by SIMPLEC, a finite volume method on staggered grid arrangement. Power-law scheme has been used to approximate convective and diffusive fluxes. The results obtained are presented for the streamlines, isotherms and variation of Nusselt number at the walls. For values of Darcy Number above 10−4, a convective regime has been found to exist in which flow is nearly independent of Darcy Number, while at low values (below 10−6) the conduction dominated region occurs in the porous medium. Increase in Aspect Ratio increases intensity of circulation while maintaining the symmetry with respect to diagonals. Increase in aspect ratio increases the region of uniform temperature which covers most of the porous region.

Natural Convection in an Annular Porous Medium: Effect of Brinkman Correction on the Bifurcation Point

2015 ◽  
Vol 789-790 ◽  
pp. 403-406 ◽  
Author(s):  
Jabrane Belabid ◽  
Abdelkhalek Cheddadi
Keyword(s):  
Porous Medium ◽  
Natural Convection ◽  
Bifurcation Point ◽  
Saturated Porous Medium ◽  
Darcy Number ◽  
Medium Effect ◽  
Published Data ◽  
Alternating Direction ◽  
Concentric Cylinders ◽  
Good Agreement

This work presents a numerical investigation of the natural convection in a saturated porous medium bounded by two horizontal concentric cylinders, modeled taking into account the Brinkman term. The governing equations (in the stream function and temperature formulation) were solved using the ADI (Alternating Direction Implicit) method. The results obtained for the bifurcation point are in a good agreement with the available published data forDa≈0. A study of the effect of Darcy number on the bifurcation point is conducted.

Natural Convection Inside a Bidisperse Porous Medium Enclosure

2009 ◽  
Vol 132 (1) ◽  
Author(s):  
Arunn Narasimhan ◽  
B. V. K. Reddy
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Natural Convection ◽  
Volume Fraction ◽  
Solid Phase ◽  
Darcy Number ◽  
The Core ◽  
Side Walls ◽  
Porous Blocks ◽  
Rayleigh Numbers

Bidisperse porous medium (BDPM) consists of a macroporous medium whose solid phase is replaced with a microporous medium. This study investigates using numerical simulations, steady natural convection inside a square BDPM enclosure made from uniformly spaced, disconnected square porous blocks that form the microporous medium. The side walls are subjected to differential heating, while the top and bottom ones are kept adiabatic. The bidispersion effect is generated by varying the number of blocks (N2), macropore volume fraction (ϕE), and internal Darcy number (DaI) for several enclosure Rayleigh numbers (Ra). Their effect on the BDPM heat transfer (Nu) is investigated. When Ra is fixed, the Nu increases with an increase in both DaI and DaE. At low Ra values, Nu is strongly affected by both DaI and ϕE. When N2 is fixed, at high Ra values, the porous blocks in the core region have negligible effect on the Nu. A correlation is proposed to evaluate the heat transfer from the BDPM enclosure, Nu, as a function of Raϕ, DaE, DaI, and N2. It predicts the numerical results of Nu within ±15% and ±9% in two successive ranges of modified Rayleigh number, RaϕDaE.

Natural Convection in Vertical Channels with Porous Media and Adiabatic Extensions

2010 ◽  
Vol 297-301 ◽  
pp. 1432-1438
Author(s):  
Assunta Andreozzi ◽  
Bernardo Buonomo ◽  
Oronzio Manca ◽  
Sergio Nardini
Keyword(s):  
Natural Convection ◽  
Wall Temperature ◽  
Finite Extension ◽  
Darcy Number ◽  
Geometrical Parameters ◽  
Computational Domain ◽  
Stream Condition ◽  
Diffusive Effects ◽  
Volume Method ◽  
Heated Plates

A numerical investigation on natural convection in air in a vertical heated channel, partially filled with porous medium, with adiabatic extensions downward and collinear the heated plates is accomplished. The fluid flow is assumed two-dimensional, laminar, steady state and incompressible. The porous material is considered as homogeneous and isotropic and the Brinkman-Forchheimer-extended Darcy model is considered. A finite-extension computational domain is employed to simulate the free-stream condition and allows to account for the diffusive effects and the numerical results are obtained using the finite volume method by FLUENT. Results in terms of wall temperature profiles are presented to evaluate the effects of the main thermal and geometrical parameters. The adiabatic extensions determine a wall temperature decrease and wall temperature decreases increasing Darcy number. In full filled heated channels wall temperature presents a significant increase for Darcy number decrease.

Natural Convection in a Cylindrical Enclosure Filled With Heat Generating Anisotropic Porous Medium

2001 ◽  
Vol 124 (1) ◽  
pp. 203-207 ◽  
Author(s):  
M. R. Dhanasekaran ◽  
Sarit Kumar Das ◽  
S. P. Venkateshan
Keyword(s):  
Porous Medium ◽  
Natural Convection ◽  
Thermal Diffusivity ◽  
Aspect Ratio ◽  
Numerical Study ◽  
Critical Value ◽  
Permeability Ratio ◽  
Anisotropic Permeability ◽  
Anisotropic Porous Medium ◽  
Diffusivity Ratio

A numerical study has been made to analyze the effects of anisotropic permeability and thermal diffusivity on natural convection in a heat generating porous medium contained in a vertical cylindrical enclosure with isothermal wall and the top and bottom perfectly insulated surfaces. The results show that the anisotropies influence the flow field and heat transfer rate significantly. The non-dimensional maximum cavity temperature increases with increase in permeability ratio. For aspect ratio greater than or equal to two, the nondimensional maximum cavity temperature increases with an increase in the thermal diffusivity ratio. For aspect ratio equal to unity, there exists a critical value of thermal diffusivity ratio at which the maximum cavity temperature is a minimum. This critical value increases with an increase in the value of anisotropic permeability ratio. Based on a parametric study correlations for maximum cavity temperature and average Nusselt number are presented.

Radiation Effect on Heat and Mass Transfer by Natural Convection from a Horizontal Surface Embedded in a Porous Medium

2018 ◽  
Vol 16 ◽  
pp. 140-157 ◽  
Author(s):  
Nasreen Bano ◽  
Oluwole Daniel Makinde ◽  
B.B. Singh ◽  
Shoeb R. Sayyed
Keyword(s):  
Mass Transfer ◽  
Porous Medium ◽  
Natural Convection ◽  
Heat And Mass Transfer ◽  
Saturated Porous Medium ◽  
Lewis Number ◽  
Similarity Solutions ◽  
Horizontal Surface ◽  
Integral Approach ◽  
Power Law Exponent

This paper deals with the study of the heat and mass transfer characteristics of natural convection from a horizontalsurface embedded in a radiating fluid saturated porous medium. Similarity solutions for buoyancy induced heat and masstransfer from a horizontal surface, where the wall temperature and concentration are a power function of distance fromthe origin, are obtained by using an integral approach of Von Karman type. The effects of the governing parameters suchas buoyancy ratio, Lewis number, radiation parameter and the power-law exponent on local Nusselt and local Sherwoodnumbers have been investigated both numerically and graphically.

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