Free convection heat transfer in a square cavity filled with a porous medium saturated by a nanofluid (original) (raw)
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International Journal of Heat and Technology, 2021
The involvement of non-linear convection effects in a natural convective fluid flow and heat transfer along with the effects of magnetic field in a porous cavity is studied numerically. Cu-water filled cavity of higher temperature at the left wall and lower temperature at the right wall. The governing equations are organized to achieve the required flow by using two-dimensional equations of energy, continuity and momentum. Vorticity-stream function based dimensionless equations are solved using the finite difference techniques. The results are discussed for various dimensionless parameters such as the Darcy number, non-linear convection parameter, Hartmann number, Rayleigh number and solid volume fraction of the nanoparticles. An augment in streamline velocity and convection heat transfer are observed by increasing the Rayleigh number, non-linear convection parameter and Darcy number. The non-linear convection parameter has a lesser effect on the lower Rayleigh numbers. Diminished s...
PLOS ONE, 2015
The free convection heat transfer of Cu-water nanofluids in a parallelogrammic enclosure filled with porous media is numerically analyzed. The bottom and top of the enclosure are insulated while the sidewalls are subject to limited temperature difference. The Darcy flow and the Tiwari and Das' nanofluid models are considered. The governing dimensionless partial differential equations are numerically solved using a finite difference code. The results are reported for isotherms and streamlines as well as Nusselt number as a function of the volume fraction of nanoparticles, porosity, types of the porous matrix, inclination angle, aspect ratio and different Rayleigh numbers. It is found that the presence of the nanoparticles inside the enclosure deteriorates the heat transfer rate, which is caused due to the increase of dynamic viscosity by the presence of nanoparticles. Therefore, in applications in which the nanofluids are used for their advantages, such as enhanced dielectric properties or antibacterial properties, more caution for the heat transfer design of the enclosure is necessary. engineering applications. In many cases, the enclosures are filled with a porous medium, which is saturated by a fluid. Convection in porous media has many applications in several sections of industries such as cooling of electronic devices, buildings, solar collectors, geothermal energy, fuel cells, food, etc. .
International Journal of Numerical Methods for Heat & Fluid Flow, 2019
Purpose-This study aims to numerically analyze natural convection of alumina-water nanofluid in a differentially-heated square cavity partially filled with a heat-generating porous medium. A single-phase nanofluid model with experimental correlations for the nanofluid viscosity and thermal conductivity has been considered for the description of the nanoparticles transport effect in the present study. Local thermal nonequilibrium approach for the porous layer with the Brinkman-extended Darcy model has been used. Design/methodology/approach-Dimensionless governing equations formulated using stream function, vorticity and temperature have been solved by the finite difference method. The effects of the Rayleigh number, Ostrogradsky number, Nield number and nanoparticles volume fraction on nanofluid flow, heat and mass transfer have been analyzed. Findings-It has been revealed that the dimensionless heat transfer coefficient at the fluid/solid matrix interface can be a very good control parameter for the convective flow and heat transfer intensity. The present results are original and new for the study of non-equilibrium natural convection in a differentially-heated nanofluid cavity partially filled with a porous medium. Originality/value-The results of this paper are new and original with many practical applications of nanofluids in the modern industry.
Conjugate heat transfer in a Differentially Heated Porous Cavity Filled with Nanofluids
The conjugate natural convection-conduction heat transfer in a square domain composed of nanofluids filled porous cavity heated by a vertical solid wall is studied under steady-state conditions. The vertical left wall of the solid is kept isothermal at hot temperature T h. The vertical right wall of the solid is in contact with the nanofluid saturated porous medium contained in the cavity. The right vertical wall of the cavity is kept isothermally at the lower temperature T c. The upper and lower horizontal walls are kept adiabatic. The governing equations of the heat transfer in the solid wall and heat and nanofluid flow, based on the Darcy model, in the nanofluid-saturated porous medium together with the derived relation of the interface temperature are solved numerically using the over-successive relaxation finite-difference method. A temperature independent nanofluids properties model is adopted. The investigated parameters are the nanoparticles volume fraction (0-0.2), Rayleigh number Ra (10-1000), solid wall to base-fluid saturated porous medium thermal conductivity ratio k wf (0.1, 1, 10), and the solid wall thickness D (0.05-0.5). The results are presented in the conventional form; contours of streamlines and isotherms and the average Nusselt number. At a very low Rayleigh number Ra=10, an enhancement in heat transfer within the porous cavity with is observed. Otherwise, the heat transfer may be unchanged or deteriorated with depending on the wall thickness D and the conductivity ratio k wf .
Heat transfer and natural convection of nanofluids in porous media
European Journal of Mechanics - B/Fluids, 2014
h i g h l i g h t s • Natural convection of a nanofluid in a porous matrix is numerically investigated. • Alternative expressions are suggested for the thermal expansion coefficient of the nanofluid. • A meshless numerical solver is adapted to the extended Darcy-Brinkman equation. • The role of the nanofluid properties in the cooling performance is studied.
Review of convection heat transfer and fluid flow in porous media with nanofluid
Renewable and Sustainable Energy Reviews, 2015
There are two advantages of using porous media. First, its dissipation area is greater than the conventional fins that enhances the heat convection. Second is the irregular motion of the fluid flow around the individual beads which mixes the fluid more effectively. Nanofluids result from the mixtures of base fluid with nanoparticles having dimensions of (1-100) nm, with very high thermal conductivities; as a result, it would be the best convection heat transfer by using two applications together: porous media and nanofluids. This article aims to summarize the published articles in respect to porosity, permeability (K) and inertia coefficient (C f ) and effective thermal conductivity (k eff ) for porous media, also on the thermophysical properties of nanofluid and the studies on convection heat transfer in porous media with nanofluid.
Forced Convection Heat Transfer of Nanofluids in a Porous Channel
Transport in Porous Media, 2012
This article is concerned with the effects of flow and migration of nanoparticles on heat transfer in a straight channel occupied with a porous medium. Investigation of force convective heat transfer of nanofluids in a porous channel has not been considered completely in the literature and this challenge is generally considered to be an open research topic that may require more study. The fully developed flow and steady Darcy-Brinkman-Forchheimer equation is employed in porous channel. The thermal equilibrium model is assumed between nanofluid and solid phases. It is assumed that the nanoparticles are distributed non-uniformly inside the channel. As a result the volume fraction distribution equation is also coupled with governing equations. The effects of parameters such as Lewis number, Schmidt number, Brownian diffusion, and thermophoresis on the heat transfer are completely studied. The results show that the local Nusselt number is decreased when the Lewis number is increased. It is observed that as the Schmidt number is increased, the wall temperature gradient is decreased and as a consequence the local Nusselt number is decreased. The effects of Lewis number, Schmidt number, and modified diffusivity ratio on the volume fraction distribution are also studied and discussed.
Free convection in a porous cavity filled with nanofluids
2012
The effect of different kind nanoparticles (cooper, alumina and titania) on free convection in a square cavity filled with a fluid-saturated porous medium have been investigated numerically. The top and bottom horizontal walls of cavity are considered adiabatic, while the vertical walls are kept at constant temperatures. The mathematical model consists in a set of partial differential equations along with the corresponding boundary conditions and these equations were solved numerically using a finite-difference scheme discretization and a Gauss-Seidel technique. The obtained results are presented in terms of streamlines, isotherms and local and averaged Nusselt numbers. Key-Words: free convection, porous media, nanofluid, numerical solution
Romanian Journal of Technical Sciences - Applied Mechanics
Natural convection is investigated in a square cavity divided in three layers, nanofluid at the middle and the upper and lower parts for porous layer. The cavity is heated from the left and cold from the right at constant temperature Th and Tc respectively. The side walls are well insulated. The Buongiorno’s model was used to evaluate the distribution of nanoparticles and takes account the Brownian and thermophoresis motion. The governing equations are solved by the Galerkin finite element method. The governing parameters are Rayleigh (103≤ Ra ≤ 106), porous layer thickness (0.3 ≤ Lp ≤ 0.05).The result shows that increasing buoyancy forces reinforce circulation flow in the nanofluid layer than the porous layer, the decrease effect of porous layer thickness improve considerably the convective heat transfer. The heat and mass transfer are enhanced.