Quantification of free convection within a hemispherical annulus through a porous medium saturated by water-copper nanofluid

2019 ◽  
Vol 29 (3) ◽  
pp. 1153-1166 ◽  
Author(s):  
Abderrahmane Baïri ◽  
Nagaraj Suresh ◽  
Palanisamy Gayathri ◽  
Nagarajan Nithyadevi ◽  
Purusothaman Abimanyu
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Rayleigh Number ◽  
Electronic Device ◽  
Numerical Study ◽  
Control Volume ◽  
Saturated Porous Medium ◽  
Pure Water ◽  
Thermal Design ◽  
Content Type

Purpose A porous medium saturated with a nanofluid based on pure water and copper nanoparticles is used for cooling a hemispherical electronic device contained in an annulus space. The disc of the cavity could be inclined at an angle ranging from 0 ° (horizontal disc with dome facing upwards) to 180° (horizontal disc with dome facing downwards). The important surface heat flux generated by the dome leads to high Rayleigh number values reaching 7.29 × 10^10. The purpose of this work is to examine the influence of the nanofluid saturated porous medium on the free convective heat transfer. Design/methodology/approach Heat transfer occurring between this active component and the isothermal passive cupola is quantified by means of a three-dimensional numerical study using the control volume method associated to the SIMPLE algorithm. Findings The work shows that heat transfer in the annulus space is improved by interposing a porous medium saturated with the water-copper nanofluid. Originality/value New correlation is proposed to calculate the Nusselt number for any combination of the inclination angle, the fraction volume, the Rayleigh number and the ratio between the thermal conductivities of the porous medium and the fluid. The wide ranges corresponding to these parameters allow the thermal design of this electronic equipment for various configurations.

Natural convective cooling of electronics contained in tilted hemispherical enclosure filled with a porous medium saturated by water-copper nanofluid

2019 ◽  
Vol 29 (1) ◽  
pp. 280-293 ◽  
Author(s):  
Abderrahmane Baïri ◽  
Jean-Gabriel Bauzin ◽  
Alexander Martín-Garín ◽  
Nacim Alilat ◽  
José Antonio Millán-García
Keyword(s):  
Porous Medium ◽  
Rayleigh Number ◽  
Control Method ◽  
Volume Fraction ◽  
Electronic Device ◽  
Thermal State ◽  
Pure Water ◽  
Volume Control ◽  
Content Type ◽  
Average Temperature

Purpose The purpose of this study is to determine the thermal behavior of a hemispherical electronic device contained in a concentric hemispherical enclosure, cooled by means of free convection through a porous medium saturated with a water–copper nanofluid. Influence of various parameters on the thermal state of this device is processed in this work. The high power generated by the dome leads to a Rayleigh number varying in the 5.2 × 107-7.29 × 1010 range. The volume fraction of the monophasic nanofluid varies between 0 (pure water) and 10 per cent while the base of the hemispherical cavity (disc) is inclined between 0° (horizontal disc with dome facing upward) and 180° (horizontal disc with dome facing downward). Design/methodology/approach The three-dimensional numerical approach is carried out by means of the volume control method associated to the SIMPLE algorithm. Findings The work shows that the average temperature of the active component increases with the Rayleigh number according to a conventional law of the power type. The increase in the angle of inclination also goes with a systematic rise in the average temperature. However, increasing the ratio of the solid–fluid thermal conductivities decreases the average temperature of the component, given the respective contributions of the conductive and natural convective phenomena occurring through the nanofluid saturated porous media. The values of this ratio vary in this work between 0 (interstice between the two hemispheres without porous medium) and 70. Originality/value The correlation proposed in this work allows to calculate the temperature of the active electronic component for all the combinations of the four influence parameters which vary in wide ranges.

Free convection of a hybrid nanofluid past a vertical plate embedded in a porous medium with anisotropic permeability

2019 ◽  
Vol 30 (8) ◽  
pp. 4083-4101 ◽  
Author(s):  
Aneela Bibi ◽  
Hang Xu ◽  
Qiang Sun ◽  
Ioan Pop ◽  
Qingkai Zhao
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Stability Analysis ◽  
Flat Surface ◽  
Saturated Porous Medium ◽  
Heat Energy ◽  
Hybrid Nanofluid ◽  
Anisotropic Permeability ◽  
Content Type ◽  
Hybrid Nanofluids

Purpose This study aims to carry out an analysis for flow and heat transfer of a new hybrid nanofluid over a vertical flat surface embedded in a saturated porous medium with anisotropic permeability at high Rayleigh number. Here the hybrid nanofluid is considered as the working fluid, with different kinds of small particles in nanoscale being suspended. Design/methodology/approach The generalized homogenous model is introduced to describe the behaviors of hybrid nanofluid. Within the framework of the boundary layer approximations, the governing equations embodying the conservation equations of total mass, momentum and thermal energy are reduced to a set of fully coupled ordinary differential equations via relevant scaling transformations. A flow stability analysis is performed to examine the behavior of convective heat energy. Accurate solutions are obtained by means of a very efficient homotopy-based package BVPh 2.0. Findings Results show that the linear correlations of physical quantities among the base fluid and its suspended nanoparticles are adequate to give accurate results for simulation of behaviors of hybrid nanofluids. Heat enhancement can be also fulfilled by hybrid nanofluids. A flow stability analysis suggests the heat-related power index m > −1/3 for satisfying the increasing behavior of convective heat energy. Originality/value Free convection of a hybrid nanofluid near a vertical flat surface embedded in a saturated porous medium with anisotropic permeability is investigated for the first time. The simplified hybrid nanofluid model is proposed for describing nanofluid behaviors. The results of this proposed approach agree well with those given by the traditional hybrid nanofluid model and experiment. It is expected that, by using different combinations of various kinds of nanoparticles, the new generation of heat transfer fluids can be fabricated, which possess similar thermal-physical properties as regular nanofluids but with lower cost.

Natural convective heat transfer in a hemispherical cavity filled with ZnO–H2O nanofluid saturated porous medium

2018 ◽  
Vol 29 (10) ◽  
pp. 1850097 ◽  
Author(s):  
Abderrahmane Baïri ◽  
Najib Laraqi
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Nusselt Number ◽  
Rayleigh Number ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Volume Fraction ◽  
Saturated Porous Medium ◽  
Physical Parameters ◽  
Numerical Work

This three-dimensional (3D) numerical work based on the volume control method quantifies the convective heat transfer occurring in a hemispherical cavity filled with a ZnO–H2O nanofluid saturated porous medium. Its main objective is to improve the cooling of an electronic component contained in this enclosure. The volume fraction of the considered monophasic nanofluid varies between 0% (pure water) and 10%, while the cupola is maintained isothermal at cold temperature. During operation, the active device generates a heat flux leading to high Rayleigh number reaching [Formula: see text] and may be inclined with respect to the horizontal plane at an angle ranging from 0[Formula: see text] to 180[Formula: see text] (horizontal position with cupola facing upwards and downwards, respectively) by steps of 15[Formula: see text]. The natural convective heat transfer represented by the average Nusselt number has been quantified for many configurations obtained by combining the tilt angle, the Rayleigh number, the nanofluid volume fraction and the ratio between the thermal conductivity of the porous medium’s solid matrix and that of the base fluid. This ratio has a significant influence on the free convective heat transfer and ranges from 0 (without porous media) to 70 in this work. The influence of the four physical parameters is analyzed and commented. An empirical correlation between the Nusselt number and these parameters is proposed, allowing determination of the average natural convective heat transfer occurring in the hemispherical cavity.

Thermal performance of nanofluid saturated porous medium on cooling electronics contained in an inclined hemispherical enclosure

2018 ◽  
Vol 29 (06) ◽  
pp. 1850039 ◽  
Author(s):  
A. Baïri ◽  
N. Laraqi
Keyword(s):  
Porous Medium ◽  
Horizontal Plane ◽  
Base Fluid ◽  
Volume Fraction ◽  
Electronic Device ◽  
Thermal State ◽  
Saturated Porous Medium ◽  
Pure Water ◽  
Solid Matrix ◽  
Average Temperature

A nanofluid saturated porous medium is used for cooling purposes of a plane electronic device contained in the base of a hemispherical cavity. According to the intended application in embarked electronics, the base could be tilted with respect to the horizontal plane by an angle ranging from 0[Formula: see text] to 180[Formula: see text] (horizontal disc with cupola facing upwards and downwards, respectively). The volume fraction of the considered monophasic water-based ZnO nanofluid varies between 0% (pure water) and 10%, while the Rayleigh number based on the radius of the cavity ranges from [Formula: see text] to [Formula: see text]. The ratio between the thermal conductivity of the porous medium solid matrix and that of the base fluid varies between 0 and 70. Influence of these four parameters on the average temperature of the active electronic device is presented and commented. The work shows that the saturated porous medium has a significant effect on the thermal state of the electronic device. A correlation is proposed to easily calculate this temperature for any combination of these parameters, which allows thermal sizing for optimal cooling of this assembly used in electronics engineering.

Natural Convection Experiments in a Stratified Liquid-Saturated Porous Medium

1986 ◽  
Vol 108 (3) ◽  
pp. 660-666 ◽  
Author(s):  
D. C. Reda
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Porous Media ◽  
Natural Convection ◽  
Rayleigh Number ◽  
Saturated Porous Medium ◽  
High Permeability ◽  
Transfer Rates ◽  
Variable Porosity ◽  
Radial Extent

Natural convection heat transfer from a constant-flux cylinder, immersed vertically through a stratified (two-layer) liquid-saturated porous medium, was investigated experimentally. Measured radial temperature profiles and heat transfer rates agreed well with numerical predictions based on the work of Hickox and Gartling. The 1:6 permeability-ratio interface existing between the two layers was found to effectively trap buoyancy-driven fluid motion within the high-permeability region, beneath the interface. Within this high-permeability region, Nusselt number versus Rayleigh number data were found to correlate with previously measured results, obtained for the same basic geometry, but with a fully permeable upper-surface hydrodynamic boundary condition. In both cases, the vertical and radial extent of the region under study were large compared to the radius of the heat source. Combined results indicate that, for a given Rayleigh number in the Darcy-flow regime, heat transfer rates from cylinders immersed vertically in uniform liquid-saturated porous media of large vertical and radial extent potentially approach limiting values. Variable-porosity effects which occur in unconsolidated porous media adjacent to solid boundaries were investigated numerically for cases where the particle-to-heater diameter ratio was small (≈ 10−2). Results showed variable-porosity effects to have a negligible influence on the thermal field adjacent to such boundaries under conditions of Darcy flow.

Numerical Investigation of Porosity Effect on Confined Round Impinging Jets of Nanofluids in Aluminum Foams

2021 ◽  
Author(s):  
Bernardo Buonomo ◽  
Anna di Pasqua ◽  
Oronzio Manca ◽  
Sergio Nappo
Keyword(s):  
Heat Transfer ◽  
Rayleigh Number ◽  
Metal Foam ◽  
Numerical Study ◽  
Pure Water ◽  
Energy Condition ◽  
Particle Diameter ◽  
Impinging Jets ◽  
Two Dimensional ◽  
Aluminum Foams

Abstract In this paper a numerical study on mixed convection in confined impinging round jets in a porous media is carried out. Pure water and Al2O3/water based nanofluids are employed as working fluids; a single-phase model approach has been applied to evaluate their properties. A two-dimensional domain is analyzed and different Peclet are considered. The Rayleigh number is fixed equal to 30000. The thermal non-equilibrium energy condition (LTNE) is assumed to accomplish two-dimensional simulations on the metal foam section. The examined aluminum foams are characterized by distinct porosity (ε), from 0.90 to about 0.97, for different values of pores per inch (PPI), equal to 5, 10, 20 and 40. The particle volume concentrations range from 0% to 4% and the particle diameter is equal to 30 nm. The target surface is heated by a constant temperature value, calculated according to the value of Rayleigh number. The results show that the convective heat transfer coefficients increase with increasing of values of Peclet number and nanoparticle concentration. Furthermore, the heat transfer coefficient shows a different behavior at varying porosity for different Peclet and Rayleigh numbers. In addition, temperature profiles are presented for the fluid and solid phases of the porous zone.

Experimental Study of Free Convection from a Vertical Flat Plate in Porous Media

2008 ◽  
Vol 273-276 ◽  
pp. 796-801
Author(s):  
L.B.Y. Aldabbagh ◽  
Mohsen Sharifpur ◽  
Mahdi Zamani
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Rayleigh Number ◽  
Free Convection ◽  
Flat Plate ◽  
Saturated Porous Medium ◽  
Convection Heat Transfer ◽  
Steady State Condition ◽  
Free Convection Heat ◽  
Vertical Flat Plate

A set of experiments is done to study the phenomenon of free convection heat transfer from an isothermal vertical flat plate embedded in a saturated porous medium in steady state condition. The porous medium consisting of 0.8 cm spheres. The aspect ratio of the isothermal flat plate, H/W, is equal to 2. Where H is the height and W is the width of the vertical plate. The investigations were cared out for Darcy modified Rayleigh number between 100 and 500. The results indicate that heat transfer increases linearly with increasing the Darcy modified Rayleigh number. In addition, the present results are in good agreement with the higher-order boundary layer theory obtained by Cheng and Hsu [1].

Natural convection in porous media

1985 ◽  
Vol 150 ◽  
pp. 89-119 ◽  
Author(s):  
V. Prasad ◽  
F. A. Kulacki ◽  
M. Keyhani
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Porous Medium ◽  
Rayleigh Number ◽  
Effective Thermal Conductivity ◽  
Darcy’S Law ◽  
Saturated Porous Medium ◽  
Darcy's Law ◽  
Experimental Results ◽  
Rayleigh Numbers

Experimental results on free convection in a vertical annulus filled with a saturated porous medium are reported for height-to-gap ratios of 1.46, 1 and 0.545, and radius ratio of 5.338. In these experiments, the inner and outer walls are maintained at constant temperatures. The use of several fluid–solid combinations indicates a divergence in the Nusselt-number–Rayleigh-number relation, as also reported by previous investigators for horizontal layers and vertical cavities. The reason for this divergence is the use of the stagnant thermal conductivity of the fluid-filled solid matrix. A simple model is presented to obtain an effective thermal conductivity as a function of the convective state, and thereby eliminate the aforementioned divergence. A reasonable agreement between experimentally and theoretically determined Nusselt numbers is then achieved for the present and previous experimental results. It is thus concluded that a unique relationship exists between the Nusselt and Rayleigh numbers unless Darcy's law is inapplicable. The factors that influence the breakdown of Darcian behaviour are characterized and their effects on heat-transfer rates are explained. It is observed that, once the relation between the Nusselt and Rayleigh numbers branches out from that obtained via the mathematical formulation based on Darcy's law, its slope approaches that for a fluid-filled enclosure of the same geometry when the Rayleigh number is large enough. An iterative scheme is also presented for estimation of effective thermal conductivity of a saturated porous medium by using the existing results for overall heat transfer.

Non-Darcian Effects in Open-Ended Cavities Filled With a Porous Medium

1991 ◽  
Vol 113 (3) ◽  
pp. 747-756 ◽  
Author(s):  
J. Ettefagh ◽  
K. Vafai ◽  
S. J. Kim
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Rayleigh Number ◽  
Prandtl Number ◽  
Saturated Porous Medium ◽  
Critical Value ◽  
Inertial Parameter ◽  
Flow Models ◽  
Flow And Heat Transfer ◽  
Buoyancy Driven Convection

The importance and relevance of non-Darcian effects associated with the buoyancy driven convection in open-ended cavities filled with fluid-saturated porous medium is analyzed in this work. Several different flow models for porous media, such as Brinkman-extended Darcy, Forchheimer-extended Darcy, and generalized flow models, are considered. The significance of inertia and boundary effects, and their crucial influence on the prediction of buouancy-induced flow and heat transfer in open-ended cavities, are investigated. Analysis is made on the proper choice of parameters that can fully determine the criteria for the range of validity of Darcy’s law in this type of configuration. Critical values of the inertial parameter, Λcrit, below which, for any given modified Rayleigh number, the Darcy flow model breaks down, have been investigated. It is shown that the critical value of the inertial parameter depends on the modified Rayleigh number and that this critical value increases as Ra* increases. It is also observed that for higher modified Rayleigh number, the deviation from a Darcian formulation appears at Darcy numbers greater than 1×10−4. The Prandtl number effects on convective flow and heat transfer are shown to be quite significant for small values of Pr. The Prandtl number effects are reduced significantly for higher values of the Prandtl number.

Sign in / Sign up

Export Citation Format

Share Document