Three-Dimensional Natural Convection in a Confined Fluid Overlying a Porous Layer

1993 ◽  
Vol 115 (3) ◽  
pp. 631-638 ◽  
Author(s):  
A. K. Singh ◽  
E. Leonardi ◽  
G. R. Thorpe
Keyword(s):  
Natural Convection ◽  
Porous Layer ◽  
Numerical Solutions ◽  
Numerical Study ◽  
Fluid Layer ◽  
Three Dimensional ◽  
Side Wall ◽  
Slip Boundary Condition ◽  
Solution Procedure ◽  
Convection Current

This paper presents a numerical study of three-dimensional, laminar natural convection in an enclosure containing a fluid layer overlying a porous layer saturated with the same fluid. The Brinkman-extended Darcy formulation is used to model fluid flow in the porous layer as this facilitates the imposition of a no-slip boundary condition at the fluid/porous layer interface. The enclosure is heated from one side wall and cooled from an opposite wall, while the remaining walls are adiabatic. The mathematical analysis is carried out in terms of a vorticity-vector potential formulation that ensures the conservation of mass. The governing equations in non-dimensional form are transformed into parabolic equations by means of a false transient method in order to facilitate a solution procedure by an alternating direction implicit method. Accuracy of the numerical solutions with respect to uniformly and nonuniformly spaced grid points has been tested by performing extensive numerical experiments. As expected, it is found that the intensity of free convection is much more profound in the fluid layer. The numerical results indicate that penetration of the fluid into the porous region depends strongly upon the Darcy and Rayleigh numbers. The effect of the ratio of thermal conductivities (porous to fluid regions) is to intensify the convection current in the fluid layer.

Three-Dimensional Laminar Natural Convection in a Vertical Air Slot With Hexagonal Honeycomb Core

1990 ◽  
Vol 112 (1) ◽  
pp. 130-136 ◽  
Author(s):  
Y. Asako ◽  
H. Nakamura ◽  
M. Faghri
Keyword(s):  
Natural Convection ◽  
Numerical Solutions ◽  
Transfer Problem ◽  
Three Dimensional ◽  
Convection Heat Transfer ◽  
Side Wall ◽  
Temperature Fields ◽  
Honeycomb Core ◽  
Wall Boundary Conditions ◽  
Laminar Natural Convection

Numerical solutions are obtained for a three-dimensional natural convection heat transfer problem in a vertical air slot with a thin hexagonal honeycomb core. The air slot is assumed to be of such dimensions 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 the Rayleigh number in the range of 103 to 105, for a Prandtl number of 0.7, and for five values of the aspect ratio of the honeycomb enclosure. The average Nusselt number results for the case of a thin honeycomb core are compared with the previously obtained results for a thick honeycomb core with conduction and adiabatic side wall boundary conditions.

Eddie Leonardi Memorial Lecture: “Natural Convection From Earth to Space”

2012 ◽  
Vol 134 (3) ◽  
Author(s):  
Victoria Timchenko
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Numerical Solutions ◽  
Numerical Study ◽  
Three Dimensional ◽  
Experimental Investigations ◽  
Memorial Lecture ◽  
Numerical Studies ◽  
Fluid Properties ◽  
Microgravity Conditions

This lecture is dedicated to the memory of Professor Eddie Leonardi, formerly International Heat Transfer Conference (IHTC-13) Secretary, who tragically died at an early age on December 14, 2008. Eddie Leonardi had a large range of research interests: he worked in both computational fluid dynamics/heat transfer and refrigeration and air-conditioning for over 25 years. However starting from his Ph.D. ‘A numerical study of the effects of fluid properties on natural convection’ awarded in 1984, one of his main passions has been natural convection and therefore the focus of this lecture will be on what Eddie Leonardi has achieved in numerical and experimental investigations of laminar natural convective flows. A number of examples will be presented which illustrate important difficulties of numerical calculations and experimental comparisons. Eddie Leonardi demonstrated that variable properties have important effects and significant differences occur when different fluids are used, so that dimensionless formulation is not appropriate when dealing with flows of fluids with significant changes in transport properties. Difficulties in comparing numerical solutions with either numerically generated data or experimental results will be discussed with reference to two-dimensional natural convection and three-dimensional Rayleigh–Bénard convection. For a number of years Eddie Leonardi was involved in a joint US-French-Australian research program—the MEPHISTO experiment on crystal growth—and studied the effects of convection on solidification and melting under microgravity conditions. Some results of this research will be described. Finally, some results of experimental and numerical studies of natural convection for building integrated photovoltaic (BIPV) applications in which Eddie Leonardi had been working in the last few years will be also presented.

Three-Dimensional Natural Convection in a Vertical Porous Layer With a Hexagonal Honeycomb Core

1992 ◽  
Vol 114 (4) ◽  
pp. 924-927 ◽  
Author(s):  
Y. Asako ◽  
H. Nakamura ◽  
Y. Yamaguchi ◽  
M. Faghri
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Boundary Conditions ◽  
Porous Layer ◽  
Numerical Solutions ◽  
Transfer Problem ◽  
Three Dimensional ◽  
Temperature Fields ◽  
Honeycomb Core ◽  
Thermal Boundary Conditions

Numerical solutions are obtained for a three-dimensional natural convection heat transfer problem in a vertical porous layer with a hexagonal honeycomb core. The porous layer is assumed to be long and wide such that the velocity and temperature fields repeat themselves in successive enclosures. The natural convection problem is solved for only one honeycomb enclosure with periodic thermal boundary conditions. The porous layer is assumed to be homogeneous and isotropic and the flow is obtained by using the Darcian model. The numerical methodology is based on an algebraic coordinate transformation technique, which maps the hexagonal cross section onto a rectangle. The transformed governing equations are solved with the SIMPLE algorithm. The calculations are performed for the Darcy–Rayleigh number in the range of 10 to 103 and for eight values of the aspect ratio (H/L = 0.25, 0.333, 0.5, 0.7, 1, 1.4, 2, and 5). Two types of thermal boundary condition for the honeycomb core wall are considered: conduction and adiabatic honeycomb core wall thermal boundary conditions. The results are presented in the form of average and local heat transfer coefficients and are compared with the corresponding values for two and three-dimensional rectangular enclosures.

Eddie Leonardi Memorial Lecture: Natural Convection from Earth to Space

2010 ◽  
Author(s):  
Victoria Timchenko
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Numerical Solutions ◽  
Numerical Study ◽  
Three Dimensional ◽  
Experimental Investigations ◽  
Memorial Lecture ◽  
Thermally Driven ◽  
Fluid Properties ◽  
Microgravity Conditions

This lecture is dedicated to the memory of Professor Eddie Leonardi, formerly International Heat Transfer Conference (IHTC-13) Secretary, who tragically died at an early age on December 14, 2008. Eddie Leonardi had a large range of research interests: he worked in both computational fluid dynamics/heat transfer and refrigeration and air-conditioning for over 25 years. However starting from his PhD ‘A numerical Study of the effects of fluid properties on Natural Convection’ awarded in 1984, one of his main passions has been natural convection and therefore the focus of this lecture will be on what Eddie Leonardi has achieved in numerical and experimental investigations of laminar natural convective flows. A number of examples will be presented which illustrate important difficulties of numerical calculations and experimental comparisons. Eddie Leonardi demonstrated that variable properties have important effects and significant differences occur when different fluids are used, so that non-dimensionalisation is not an appropriate tool when dealing with fluids in thermally driven flows in which there are significant changes in transport properties. Difficulties in comparing numerical solutions with either numerically generated data or experimental results will be discussed with reference to two-dimensional natural convection and three-dimensional Rayleigh-Be´nard convection in bounded domains with conducting boundaries. For a number of years Eddie Leonardi was involved in a joint US-French-Australian research program — the MEPHISTO experiment on crystal growth — and studied the effects of convection on solidification and melting under microgravity conditions. The results of this research will be described. Finally, results of experimental and numerical studies of natural convection for Building Integrated Photovoltaic (BIPV) applications in which Eddie Leonardi had been working in the last few years will also be presented.

CFD Analysis of Natural Convection in a Cubic Enclosure Heated From a Side Wall With Experimental Verification Using PIV

2009 ◽  
Author(s):  
Nuri Alpay Ku¨rekci
Keyword(s):  
Natural Convection ◽  
Numerical Study ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Side Wall ◽  
Velocity Measurements ◽  
Dimensional Solution ◽  
Image Velocimetry ◽  
Vertical Walls ◽  
Good Agreement

Natural convection of air in a cubical volume is investigated experimentally and numerically. A cubical volume of 20×20×20 cm dimensions was built for the experimental study. One of the vertical walls covering the volume is hot, the other one is cold and the rest are adiabatic. Three walls are made of aluminum and the others are made of heat-resistant glass. The hot wall temperature is kept constant during the experiments by means of an electrical heater. The cold wall is at the ambient temperature. Other adiabatic surfaces are insulated with polyurethane foam. Experiments are performed in an air-conditioned room at 21°C. PIV (Particle Image Velocimetry) is used for velocity measurements. The FLUENT CFD software package is used for the numerical study. A three-dimensional solution is obtained for the laminar flow case for a 61×61×61 grid. The numerical and experimental results are compared with each other for the validation of the numerical solution under the testing conditions of TH = 69°C, TC = 41°C and Ra = 1.3×107. Results obtained from the numerical and experimental studies are in a reasonably good agreement with each other.

EXPERIMENTAL AND NUMERICAL STUDY OF THREE-DIMENSIONAL NATURAL CONVECTION AND FREEZING IN WATER

1994 ◽  
Author(s):  
C. Abegg ◽  
Graham de Vahl Davis ◽  
W.J. Hiller ◽  
St. Koch ◽  
Tomasz A. Kowalewski ◽  
...  
Keyword(s):  
Natural Convection ◽  
Numerical Study ◽  
Three Dimensional

Effect of Periodic Imposed Heat Flux on Three-Dimensional Natural Convection in a Partially Heated Cubical Enclosure

2016 ◽  
Vol 831 ◽  
pp. 83-91
Author(s):  
Lahoucine Belarche ◽  
Btissam Abourida
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Numerical Study ◽  
Control Volume ◽  
Vertical Wall ◽  
Three Dimensional ◽  
Maximum Temperature ◽  
Cubical Enclosure ◽  
Simplec Algorithm ◽  
Volume Method

The three-dimensional numerical study of natural convection in a cubical enclosure, discretely heated, was carried out in this study. Two heating square sections, similar to the integrated electronic components, are placed on the vertical wall of the enclosure. The imposed heating fluxes vary sinusoidally with time, in phase and in opposition of phase. The temperature of the opposite vertical wall is maintained at a cold uniform temperature and the other walls are adiabatic. The governing equations are solved using Control volume method by SIMPLEC algorithm. The sections dimension ε = D / H and the Rayleigh number Ra were fixed respectively at 0,35 and 106. The average heat transfer and the maximum temperature on the active portions will be examined for a given set of the governing parameters, namely the amplitude of the variable temperatures a and their period τp. The obtained results show significant changes in terms of heat transfer, by proper choice of the heating mode and the governing parameters.

scholarly journals Numerical study of the turbulent natural convection of nanofluids in a partially heated cubic cavity

2021 ◽  
pp. 57-57
Author(s):  
Zakaria Lafdaili ◽  
Sakina El-Hamdani ◽  
Abdelaziz Bendou ◽  
Karim Limam ◽  
Bara El-Hafad
Keyword(s):  
Nusselt Number ◽  
Natural Convection ◽  
Heat Exchange ◽  
Metallic Nanoparticles ◽  
Volume Fraction ◽  
Numerical Study ◽  
Three Dimensional ◽  
Stability Characteristic ◽  
Horizontal Strip ◽  
Turbulent Natural Convection

In this work we study numerically the three-dimensional turbulent natural convection in a partially heated cubic cavity filled with water containing metallic nanoparticles, metallic oxides and others based on carbon.The objective is to study and compare the effect of the addition of nanoparticles studied in water and also the effect of the position of the heated partition on the heat exchange by turbulent natural convection in this type of geometry, which can significantly improve the design of heat exchange systems for better space optimization. For this we have treated numerically for different volume fractions the turbulent natural convection in the two cases where the cavity is heated respectively by a vertical and horizontal strip in the middle of one of the vertical walls. To take into account the effects of turbulence, we used the standard turbulence model ? - ?. The governing equations are discretized by the finite volume method using the power law scheme which offers a good stability characteristic in this type of flow. The results are presented in the form of isothermal lines and current lines. The variation of the mean Nusselt number is calculated for the two positions of the heated partition as a function of the volume fraction of the nanoparticles studied in water for different Rayleigh numbers.The results show that carbon-based nanoparticles intensify heat exchange by convection better and that the position of the heated partition significantly influences heat exchange by natural convection. In fact, an improvement in the average Nusselt number of more than 20% is observed for the case where the heated partition is horizontal.

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