Non-equilibrium natural convection in a differentially-heated nanofluid cavity partially filled with a porous medium (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...
International Journal of Heat and Mass Transfer, 2015
The steady natural convection in a two-dimensional porous square cavity filled with a nanofluid and including internal heat generation is presented in this paper. The mathematical model considered consists of the Darcy equation for the momentum, while a new model is proposed for the energy and nanoparticles' concentration equations. The system of partial differential equations is written in terms of a dimensionless stream function, temperature and concentration of the nanoparticles and is solved numerically using the finite difference method. The effects of the governing parameters, such as: Rayleigh number Ra, the Lewis number Le and the dimensionless ratio between the thermophoretic and Brownian coefficients N BT on the velocity, temperature and nanoparticles' concentration, Nusselt and Sherwood numbers are studied. It is found that the addition of the nanoparticles into the fluid saturated porous medium reduces the temperature and enhances the heat transfer when the value of the thermal conductivity of the nanoparticles is much higher than the thermal conductivity of the solid structure of the porous medium. This addition has almost no effect on the flow and heat transfer characteristics when the values of the thermal conductivity of the nanoparticles and the thermal conductivity of the solid structure of the porous medium have close values.
2015
Natural convection is convection where the fluid motion is driven by buoyancy forces. Porous media and nanofluids have an impact on the heat transfer capabilities of thermal systems. The present experimental study is part of ongoing research and lies at the intersection of buoyancy driven flow in a cavity, porous mediums and nanofluids. The nanofluid consists of Al2O3 nanoparticles in the base fluid of 60% ethylene glycol (EG) and 40% water. A Rayleigh number range of 6 × 10 < Ra∗ < 1.6 × 10, for a volume fraction of 0.2% nanoparticles. The porous medium used is glass spheres of 16mm. In this research the effective viscosity of the nanofluid was determined experimentally while the effective thermal conductivity was available in the literature. The results showed that heat transfer is affected by both the porous medium and the nanofluid. The results show that the heat transfer in the case of porous media with nanofluid is more than the case of pure base fluid. However, more exp...
Study of Laminar Naturel Convection in Partially Porous Cavity in the Presence of Nanofluids
Journal of Advanced Research in Fluid Mechanics and Thermal Sciences, 2020
The objective of this work is the mathematical modelling and the numerical simulation of the stationary, laminar, and natural convection, in a confined square cavity (H = L) filled with two fluids (a mixture of nanoparticles of aluminum oxide and Al2O3 water) in one partition and pure water in the other partition. A porous conductive wall of thickness w (w = L/e) and thermal conductivity Keff constitutes the exchange surface between these two partitions. The fluid movement is modeled by the Navier-Stokes equations in the two partitions, while the porous medium is modelled by the Darcy–Brinkman equation. Comsol Multiphysics software is used to solve the system of differential equations that is based on the finite element method. The results are discussed with particular attention to the mean and local Nusselt number (Nu), streamlines and isotherms. A parametric study for Rayleigh number Ra (102 to 106), volume fraction j (0% to 10%), and Darcy number Da (10-7 to 10-2) is performed. T...
Natural convection is convection where the fluid motion is driven by buoyancy forces. Porous media and nanofluids have an impact on the heat transfer capabilities of thermal systems. The present experimental study is part of ongoing research and lies at the intersection of buoyancy driven flow in a cavity, porous mediums and nanofluids. The nanofluid consists of Al 2 O 3 nanoparticles in the base fluid of 60% ethy-lene glycol (EG) and 40% water. A Rayleigh number range of 6 × 10 3 < Ra * < 1.6 × 10 4 , for a volume fraction of 0.2% nanoparticles. The porous medium used is glass spheres of 16mm. In this research the effective viscosity of the nanofluid was determined experimentally while the effective thermal conductivity was available in the literature. The results showed that heat transfer is affected by both the porous medium and the nanofluid. The results show that the heat transfer in the case of porous media with nanofluid is more than the case of pure base fluid. However, more experimentation for a wider range of Rayleigh numbers will be a part of future works of this ongoing research.
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.
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. .
2021
In the present work, results of a numerical study carried out using finite volume method, to investigate the fluid flow and heat transfer characteristics of Alumina ( Al2O3 ) nanoparticles in the base fluid (water) in a square cavity under natural convection mode are presented. The Semi Implicit Method for Pressure Linked Equations (SIMPLE) algorithm was used to solve the discretized momentum and energy equations. Constant temperature heat sources of same strength are placed on bottom and left vertical surfaces whereas the right surface was kept cold, while the top surface was maintained as adiabatic. The impact of Rayleigh number (RaN) ( 1000 to 106 ) and nanoparticles volume fraction (Φ = 0 %, 5 %, 10 %, 15 % and 20 %) on fluid and heat flow characteristics were numerically investigated and presented in the form of streamlines, isothermal lines, mid line horizontal and vertical velocity components, local Nusselt number ( Nuloc ) and average Nusselt number ( Nuavg ). The obtained r...