Freezing of Water-Saturated Porous Media in the Presence of Natural Convection: Experiments and Analysis

1989 ◽  
Vol 111 (2) ◽  
pp. 425-432 ◽  
Author(s):  
S. Chellaiah ◽  
R. Viskanta
Keyword(s):  
Porous Media ◽  
Natural Convection ◽  
Convection Flow ◽  
Liquid Region ◽  
Measured Temperature ◽  
Density Inversion ◽  
Flow And Heat Transfer ◽  
Numerical Predictions ◽  
Darcy Equations ◽  
Water Saturated

Freezing of superheated water-porous media (glass beads) contained in a rectangular test cell has been studied both experimentally and numerically. The effects of liquid superheat and imposed temperature difference were investigated. When the superheat across the liquid region was small the flow in the porous media was weak, and the interface was almost planar. For larger superheats, natural convection flow and the solidification front shape and velocity were found to depend on the imposed temperature and the permeability of the porous medium. Due to the density inversion of water, the rate of freezing was higher, either at the top or at the bottom of the cell, depending on the amount of superheat. The measured temperature distributions were compared with predictions of numerical model that considered both conduction in the solid and natural convection in the liquid region. This model is based on volumetric averaging of the macroscopic transport equations, with phase change assumed to occur volumetrically over a small temperature range. Both Brinkman and Forchheimer extensions were added to the Darcy equations. The effect of density inversion of water on the fluid flow and heat transfer has been modeled. Good agreement has been found between the experimental data and numerical predictions.

scholarly journals A Meshfree Method for Heat Explosion Problems with Natural Convection in Inclined Porous Media

2018 ◽  
Vol 241 ◽  
pp. 01019 ◽  
Author(s):  
Abdoulhafar Halassi ◽  
Youssef Joundy ◽  
Loubna Salhi ◽  
Ahmed Taik
Keyword(s):  
Porous Media ◽  
Natural Convection ◽  
Vertical Direction ◽  
Meshfree Method ◽  
Boussinesq Approximation ◽  
Complex Behaviour ◽  
Meshless Collocation ◽  
Darcy Equations ◽  
Small Inclination ◽  
Good Agreement

This paper investigates the interaction between natural convection and heat explosion in porous media. A meshless collocation method based on multiquadric radial basis functions has been applied to study the problem in an inclined two-dimensional porous media. The governing equations consist of coupling the Darcy equations in the Boussinesq approximation of low density variations to the heat equation with a nonlinear chemical source term. The numerical results obtained are in good agreement with some previous studies that consider the vertical direction. A complex behaviour of solutions is observed, including periodic and aperiodic oscillations. We have shown that a small inclination of the container stabilizes the reactive fluid and can prevent thermal explosion.

Transient Natural Convection Between Two Zones in an Insulated Enclosure

1988 ◽  
Vol 110 (1) ◽  
pp. 116-125 ◽  
Author(s):  
P. A. Litsek ◽  
A. Bejan
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Numerical Experiments ◽  
Thermal Stratification ◽  
Convection Flow ◽  
Natural Convection Flow ◽  
Flow And Heat Transfer ◽  
Vertical Opening ◽  
The Right ◽  
Rayleigh Numbers

The natural convection flow and heat transfer between two enclosures that communicate through a vertical opening is studied by considering the evolution of an enclosed fluid in which the left half is originally at a different temperature than the right half. Numerical experiments show that at sufficiently high Rayleigh numbers the ensuing flow is oscillatory. This and other features are anticipated on the basis of scale analysis. The time scales of the oscillation, the establishment of thermal stratification, and eventual thermal equilibrium are determined and tested numerically. At sufficiently high Rayleigh numbers the heat transfer between the communicating zones is by convection, in accordance with the constant-Stanton-number trend pointed out by Jones and Otis (1986). The range covered by the numerical experiments is 102 < Ra < 107, 0.71 < Pr < 100, and 0.25 < H/L < 1.

scholarly journals Natural Convection Experiments in a Liquid-Saturated Porous Medium Bounded by Vertical Coaxial Cylinders

1983 ◽  
Vol 105 (4) ◽  
pp. 795-802 ◽  
Author(s):  
D. C. Reda
Keyword(s):  
Natural Convection ◽  
Surface Temperature ◽  
Fluid Layer ◽  
Saturated Porous Medium ◽  
Outer Cylinder ◽  
Power Input ◽  
Surface Boundary ◽  
Measured Temperature ◽  
Heater Surface ◽  
Numerical Predictions

An experimental effort is presently underway to investigate natural convection in liquid-saturated porous media utilizing a geometry and hydrodynamic/thermal boundary conditions relevant to the problem of nuclear-waste isolation in geologic repositories. During the first phase of this research program, detailed measurements were made of the steady-state thermal field throughout an annular test region bounded by a vertical, constant-heat-flux, inner cylinder and a concentrically placed, constant-temperature, outer cylinder. An overlying, constant-pressure fluid layer was utilized to supply a permeable upper surface boundary condition. Results showed the heater surface temperature to increase with increasing vertical distance due to the buoyantly driven upflow. The measured temperature difference (ΔT) between the average heater surface temperature and the constant outer-surface temperature was found to be progressively below the straight-line/conduction-only solution for ΔT versus power input, as the latter was systematically increased. Comparisons between measured results and numerical predictions obtained using the finite element code MARIAH showed very good agreement, thereby contributing to the qualification of this code for repository-design applications.

Natural Convection Flow and Heat Transfer Between a Fluid Layer and a Porous Layer Inside a Rectangular Enclosure

1987 ◽  
Vol 109 (2) ◽  
pp. 363-370 ◽  
Author(s):  
C. Beckermann ◽  
S. Ramadhyani ◽  
R. Viskanta
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Natural Convection ◽  
Numerical Model ◽  
Porous Layer ◽  
Fluid Layer ◽  
Convection Flow ◽  
Natural Convection Flow ◽  
Rectangular Enclosure ◽  
Flow And Heat Transfer

A numerical and experimental study is performed to analyze the steady-state natural convection fluid flow and heat transfer in a vertical rectangular enclosure that is partially filled with a vertical layer of a fluid-saturated porous medium. The flow in the porous layer is modeled utilizing the Brinkman–Forchheimer–extended Darcy equations. The numerical model is verified by conducting a number of experiments, with spherical glass beads as the porous medium and water and glycerin as the fluids, in rectangular test cells. The agreement between the flow visualization results and temperature measurements and the numerical model is, in general, good. It is found that the amount of fluid penetrating from the fluid region into the porous layer depends strongly on the Darcy (Da) and Rayleigh (Ra) numbers. For a relatively low product of Ra × Da, the flow takes place primarily in the fluid layer, and heat transfer in the porous layer is by conduction only. On other hand, fluid penetrating into a relatively highly permeable porous layer has a significant impact on the natural convection flow patterns in the entire enclosure.

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