Showing papers on "Natural convection published in 2012"
TL;DR: In this paper, the state-of-the-art knowledge and research results of thermal transport in open celled cellular metal foams, which covers the effective thermal conductivity, forced convection, natural convection and thermal radiation, pool boiling and flow boiling heat transfer, solid/liquid phase change heat transfer and catalytic reactor were provided.
374 citations
TL;DR: In this paper, the melting phase change heat transfer in paraffin-saturated in open-celled metallic foams was experimentally and numerically studied, and the effects of foam morphology parameters, including porosity and pore density, on the wall temperature and the temperature uniformity inside the foam were investigated.
313 citations
TL;DR: In this paper, the effect of static radial magnetic field on the thermal conductivity and viscosity of a concentric annulus between a cold outer square and heated inner circular cylinders was investigated numerically using the lattice Boltzmann method.
287 citations
TL;DR: In this paper, the second law analysis of thermodynamics in enclosures due to buoyancy-induced flow for energy systems is reviewed and the authors define entropy generation minimization or thermodynamic optimization.
Abstract: This paper reviews the second law analysis of thermodynamics in enclosures due to buoyancy-induced flow for energy systems It defines entropy generation minimization or thermodynamic optimization In addition, the article summarizes the recent works on entropy generation in buoyancy-induced flows in cavity and channels Studies on mixed convection were also included in the study Presentation was performed for flow in porous media and viscous fluid filled media at different shaped enclosures and duct under buoyancy-induced force
252 citations
TL;DR: In this paper, a comprehensive review on the research progress on the natural convective heat transfer characteristics of nanofluids for both single and two-phase models is presented, where both experimental and theoretical studies are reviewed for natural convection of Nanofluid in different types of enclosures.
Abstract: Nanofluids are considered to have great potential for heat transfer enhancement and are highly suited to application in practical heat transfer processes. Recently, several important studies were carried out to understand and explain the causes of the enhancement or control of heat transfer using nanofluids. The main aim upon which the present work is based is to give a comprehensive review on the research progress on the natural convective heat transfer characteristics of nanofluids for both single- and two-phase models. Both experimental and theoretical studies are reviewed for natural convection of nanofluids in different types of enclosures.
251 citations
TL;DR: In this paper, a semi-annulus enclosure filled with nanofluid is used for natural convection heat transfer in a control volume based finite element method (CVFEM).
237 citations
TL;DR: In this paper, a two component non-homogenous equilibrium model is used for the nanofluid that incorporates the effects of Brownian motion and thermophoresis, and variable thermal conductivity and variable viscosity are taken into account in this work.
226 citations
TL;DR: In this article, the authors used the control volume based finite element method (CVFEM) to simulate the fluid flow and heat transfer of Cu-water nanofluid in the presence of a horizontal magnetic field.
216 citations
TL;DR: The steady boundary layer free convection flow past a horizontal flat plate embedded in a porous medium filled by a water-based nanofluid containing gyrotactic microorganisms is investigated in this article.
200 citations
TL;DR: In this article, a combined experimental and numerical study is performed aiming to understand the role of buoyancy-driven convection during constrained melting of phase change materials (PCMs) inside a shell and tube heat exchanger.
193 citations
TL;DR: In this article, the Galerkin finite element method has been employed to solve momentum and energy balance as well as post processing streamfunctions and heatfunctions in the presence of hot and cold side walls.
TL;DR: In this article, a numerical analysis of natural convection has been performed for a two-dimensional triangular enclosure with partially heated from below and cold inclined wall filled with nanofluid in presence of magnetic field.
TL;DR: In this paper, a scaling law for the onset of plate tectonics on terrestrial planets was proposed, which states that damage must reduce the viscosity of shear zones in the lithosphere to a critical value equivalent to the underlying mantle viscosities.
TL;DR: In this article, a free convection thermophoretic hydromagnetic flow over a radiate isothermal inclined plate with heat source/sink effect is considered, and the shooting method is employed to yield the numerical solutions for the model.
TL;DR: In this article, the cooling performance and mass of a pin-fin radial heat sink were optimized to obtain a lighter heat sink while maintaining a similar cooling performance to that of a plate-fin heat sink.
TL;DR: In this article, the effect of Brownian motion and thermophoresis on convective flow of a nanofluid over a convectively heated vertical plate is investigated using a similarity analysis of the transport equations.
TL;DR: In this article, the effects of Grashof number and volume fraction of Cu-water nanofluid on natural convection heat transfer and fluid flow inside a two-dimensional wavy enclosure has been investigated numerically.
TL;DR: In this paper, lattice Boltzmann method is applied to investigate the natural convection flows utilizing nanofluids in a square cavity, where the fluid in the cavity is a water-based Nanofluid containing Al2O3 or Cu nanoparticles.
TL;DR: In this paper, the authors studied steady, laminar, natural convection boundary layer flow over a permeable vertical cone embedded in a porous medium saturated with a nanofluid in the presence of uniform lateral mass flux.
Abstract: Purpose – The purpose of this paper is to study steady, laminar, natural convection boundary‐layer flow over a permeable vertical cone embedded in a porous medium saturated with a nanofluid in the presence of uniform lateral mass flux.Design/methodology/approach – The paper studies steady, laminar, natural convection boundary‐layer flow over a permeable vertical cone embedded in a porous medium saturated with a nanofluid in the presence of uniform lateral mass flux.Findings – The presence of nanoparticles has significant effects of heat transfer.Originality/value – The area of nanofluids is very original.
TL;DR: In this paper, the effect of internal heat source on the onset of Darcy-Brinkman convection in a porous layer saturated by nanofluid is studied, and the resulting eigenvalue problem is solved numerically using the Galerkin technique with the Rayleigh number as the eigen value.
TL;DR: In this paper, the authors focused on the numerical modeling of steady laminar natural convection flow in an annulus filled with water-alumina nanofluid, where the inner surface of the annulus is heated uniformly by a uniform heat flux q and the outer boundary is kept at a constant temperature T c.
TL;DR: In this article, a simple three noded triangular element is used to divide the porous domain into smaller segments known as elements and then the algebraic set of equations resulting from the finite element equation are assembled into a global matrix and then solved iteratively to get the solution variables.
TL;DR: In this paper, a parametric study was conducted and the effects of pertinent parameters such as Rayleigh number, size of the adiabatic square body, and volume fraction of the Cu nanoparticles on the fluid flow and thermal fields and heat transfer inside the cavity were investigated.
TL;DR: In this paper, the effect of Rayleigh number, solid volume fraction and both Hartmann number and heat generation or absorption coefficient on the iso-contours of streamline and temperature were investigated in a square cavity filled with different nanofluids.
TL;DR: In this article, a boundary condition-enforced immersed boundary method is presented for simulation of free and forced convection problems with Dirichlet-type boundary condition, where heat source/sink is introduced into the energy equation to model the effect of immersed boundary.
TL;DR: In this article, the conservation equations of mass, momentum and energy are solved using the finite volume method for varying inclination angles between 0° and 90° and two cavity height based Rayleigh numbers, Ra = 104 and 105, a Prandtl number of Pr = 102 and three cavity aspect ratios of 1, 4 and 8.
TL;DR: In this article, the authors studied the free convection boundary-layer flow of a nanofluid along a stretching sheet with thermal radiation in the presence of magnetic field and obtained non-similar equations, continuity, momentum, energy, and concentration equations.
Abstract: In this work, we study the unsteady free convection boundary-layer flow of a nanofluid along a stretching sheet with thermal radiation in the presence of magnetic field. To obtain non-similar equations, continuity, momentum, energy, and concentration equations have been non-dimensionalized by usual transformation. The non-similar solutions are considered here which depend on the magnetic parameter M, radiation parameter R, Prandtl number Pr, Eckert number Ec, Lewis number Le, Brownian motion parameter Nb, thermophoresis parameter Nt, and Grashof number Gr. The obtained equations have been solved by an explicit finite difference method with stability and convergence analysis. The velocity, temperature, and concentration profiles are discussed for different time steps and for the different values of the parameters of physical and engineering interest.
TL;DR: In this article, a parametric study was conducted and effects of pertinent parameters such as Rayleigh number, the aspect ratio of the C-shaped enclosure, and the volume fraction of the Cu nanoparticles on the flow and temperature fields and the rate of heat transfer inside the enclosure were investigated.
TL;DR: In this article, the Lattice Boltzmann simulation of natural convection in an open enclosure which subjugated to water/copper nanofluid has been investigated, and the results show that the average Nusselt number increases with augmentation of Rayleigh number and the volume fraction of nanoparticles for whole ranges of aspect ratios.
TL;DR: In this article, a systematic study of the triggering of the regime with an enhanced heat transfer, originally named the "Ultimate Regime" of convection, was conducted in convection cells with various aspect ratios and different specificities such as altered boundary conditions or obstacles inserted in the flow.
Abstract: Rayleigh-B\'enard cells are one of the simplest systems to explore the laws of natural convection in the highly turbulent limit. However, at very high Rayleigh numbers (Ra > 1E12) and for Prandtl numbers of order one, experiments fall into two categories: some evidence a steep enhancement of the heat transfer while others do not. The origin of this apparent disagreement is presently unexplained. This puzzling situation motivated a systematic study of the triggering of the regime with an enhanced heat transfer, originally named the "Ultimate Regime" of convection. High accuracy heat transfer measurements have been conducted in convection cells with various aspect ratios and different specificities, such as altered boundary conditions or obstacles inserted in the flow. The two control parameters, the Rayleigh and Prandtl numbers have been varied independently to disentangle their relative influence. Among other results, it is found that i) most experiments reaching very high $Ra$ are not in disagreement if small differences in Prandtl numbers are taken into account, ii) the transition is not directly triggered by the large scale circulation present in the cell, iii) the sidewall of the cell have a significant influence on the transition. The characteristics of this Ultimate regime are summarized and compared with R. Kraichnan prediction for the asymptotic regime of convection.