Showing papers on "Combined forced and natural convection published in 2011"
TL;DR: In this paper, turbulent forced convection flow of water-Al2O3 nanofluid in a circular tube, subjected to a constant and uniform heat flux at the wall, is numerically analyzed.
240 citations
TL;DR: In this article, the authors compared CFD predictions of single-phase and three different two-phase models (volume of fluid, mixture, Eulerian) for laminar mixed convection of Al2O3-water nanofluids.
196 citations
TL;DR: In this paper, a top-sided lid-driven cavity heated by a corner heater is considered under isothermal boundary conditions with different length in bottom and right vertical walls. But the results showed some very interesting results.
181 citations
TL;DR: In this paper, the authors investigated the stability of double-diffusive convection for viscoelastic fluid with Soret effect in a porous medium using a modified-Maxwell-Darcy model.
179 citations
TL;DR: In this article, the authors investigated mixed convection in a square cavity of sinusoidal boundary temperatures at the sidewalls in the presence of magnetic field and obtained the results for various combinations of amplitude ratio, phase deviation, Richardson number, and Hartmann number.
148 citations
TL;DR: In this paper, forced convection flows of nanofluids consisting of water with TiO2 and Al2O3 nanoparticles in a horizontal tube with constant wall temperature are investigated numerically.
144 citations
TL;DR: In this article, an experimental investigation of turbulent heat transfer in vertical upward and downward supercritical CO2 flow was conducted in a circular tube with an inner diameter of 4.5mm.
143 citations
TL;DR: In this paper, a two-phase mixture model has been used to investigate the thermal behaviors of the nanofluid for various inclination angles of enclosure ranging from θ−−60° to θ −60°, volume fraction from 0% to 8%, Richardson numbers varying from 0.01 to 100 and constant Grashof number 104.
134 citations
TL;DR: In this article, the combined effects of Soret (thermal-diffusion) and Dufour (diffusion-thermo) on unsteady MHD non-Darcy mixed convection over a stretching sheet embedded in a saturated porous medium in the presence of thermal radiation, viscous dissipation and first-order chemical reaction are analyzed.
134 citations
TL;DR: In this article, a thermal lattice Boltzmann model is developed for the melting with natural convection in porous media at the representative elementary volume scale, and an evolution equation of the temperature distribution function is constructed through selecting the equilibrium distribution function and non-linear source term properly.
126 citations
TL;DR: In this paper, a numerical simulation using a finite volume scheme is carried out for a laminar steady mixed convection problem in a two-dimensional square enclosure of width and height (L), with a rotating circular cylinder of radius (R = 0.2L) enclosed inside it.
TL;DR: In this article, an analytical and numerical study of natural convection in a shallow rectangular cavity filled with nanofluids is presented, where analytical solutions for the stream function and temperature are obtained using a parallel flow approximation in the core region of the cavity and an integral form of the energy equation.
TL;DR: In this article, the authors considered the Brownian motions of nanoparticles to determine the effective thermal conductivity and the effective dynamic viscosity of Al2O3-water nanofluid, which depend on temperature.
TL;DR: In this article, the effects of mixed convective heat and mass transfer in an asymmetric channel with peristalsis were discussed numerically and explained graphically, and the analytical solutions for temperature, concentration, velocity and stream function were obtained.
TL;DR: In this article, the effects of Peclet number, interphase heat transfer co-efficient and thermal conductivity ratio on the performance of an annular cylinder with saturated porous medium were investigated.
TL;DR: In this paper, a second-grade viscoelastic fluid past a wedge with porous suction or injection has been studied, and the results indicated that elastic effect (E) in the flow could increase the local heat transfer coefficient and enhance the heat transfer of a wedge.
Abstract: A magnetic hydrodynamic (MHD) mixed convective heat transfer problem of a second-grade viscoelastic fluid past a wedge with porous suction or injection has been studied. Governing equations include continuity equation, momentum equation and energy equation of the fluid. It has been analyzed by a combination of a series expansion method, the similarity transformation and a second-order accurate finite-difference method. Solutions of wedge flow on the wedge surface have been obtained by a generalized Falkner–Skan flow derivation. Some important parameters have been discussed by this study, which include the Prandtl number (Pr), the elastic number (E), the free convection parameter (G) and the magnetic parameter (M), the porous suction and injection parameter (C) and the wedge shape factor (β). Results indicated that elastic effect (E) in the flow could increase the local heat transfer coefficient and enhance the heat transfer of a wedge. In addition, similar to the results from Newtonian fluid flow and conduction analysis of a wedge, better heat transfer is obtained with a larger G and Pr.
TL;DR: In this article, the Boussinesq approximation of the Navier-Stokes equations is used to obtain the upper bound on the vertical heat transport in two-dimensional Rayleigh-B\'enard convection between stress-free isothermal boundaries.
Abstract: Rigorous upper limits on the vertical heat transport in two-dimensional Rayleigh-B\'enard convection between stress-free isothermal boundaries are derived from the Boussinesq approximation of the Navier-Stokes equations. The Nusselt number Nu is bounded in terms of the Rayleigh number Ra according to $\mathrm{Nu}\ensuremath{\le}0.2891{\mathrm{Ra}}^{5/12}$ uniformly in the Prandtl number Pr. This scaling challenges some theoretical arguments regarding asymptotic high Rayleigh number heat transport by turbulent convection.
01 Jan 2011
TL;DR: In this article, results of applying a non-uniform magnetic field on a ferrofluid (kerosene and 4-vol% Fe3O4 ) flow in a vertical tube have been reported.
TL;DR: In this paper, the evaporation characteristics of fuel droplets containing suspended aluminum nanoparticles were determined under natural and weak forced convections at varying flow temperatures, and it was shown that under higher convection temperatures droplet evapuration follows the classical D 2 -law under low forced convection or natural convection.
TL;DR: A boundary layer analysis is presented for the mixed convection past a vertical wedge in a porous medium saturated with a nano fluid and the dependency of the friction factor, surface heat transfer rate, and mass transfer rate has been discussed.
Abstract: A boundary layer analysis is presented for the mixed convection past a vertical wedge in a porous medium saturated with a nano fluid. The governing partial differential equations are transformed into a set of non-similar equations and solved numerically by an efficient, implicit, iterative, finite-difference method. A parametric study illustrating the influence of various physical parameters is performed. Numerical results for the velocity, temperature, and nanoparticles volume fraction profiles, as well as the friction factor, surface heat and mass transfer rates have been presented for parametric variations of the buoyancy ratio parameter Nr, Brownian motion parameter Nb, thermophoresis parameter Nt, and Lewis number Le. The dependency of the friction factor, surface heat transfer rate (Nusselt number), and mass transfer rate (Sherwood number) on these parameters has been discussed.
TL;DR: In this article, the authors investigate the flow and heat transfer in a 2D square cavity where the flow is induced by a shear force resulting from the motion of the upper lid combined with buoyancy force due to bottom heating.
TL;DR: In this article, the authors investigated the unsteady mixed convection flow past a vertical porous flat plate moving through a binary mixture in the presence of radiative heat transfer and nth-order Arrhenius type of irreversible chemical reaction by taking into account the diffusion-thermal (Dufour) and thermo-diffusion (Soret) effects.
Abstract: This study investigates the unsteady mixed convection flow past a vertical porous flat plate moving through a binary mixture in the presence of radiative heat transfer and nth-order Arrhenius type of irreversible chemical reaction by taking into account the diffusion-thermal (Dufour) and thermo-diffusion (Soret) effects. Assuming an optically thin radiating fluid and using a local similarity variable, the governing nonlinear partial differential equations have been transformed into a set of coupled nonlinear ordinary differential equations, which are solved numerically by applying shooting iteration technique together with fourth-order Runge-Kutta integration scheme. Graphical results for the dimensionless velocity, temperature, and concentration distributions are shown for various values of the thermophysical parameters controlling the flow regime. Finally, numerical values of physical quantities, such as the local skin-friction coefficient, the local Nusselt number, and the local Sherwood number are pre...
TL;DR: In this article, the effects of the outlet positions, Richardson numbers, Reynolds numbers, locations, and aspect ratios of an inner square cylinder on the flow and the thermal fields were investigated and their ranges are as follows: the Richardson number and Reynolds number are varied in the ranges from 0−10 and 50−200, respectively, location of the inner cylinder (0.25−≤L X...
Abstract: The study of two-dimensional mixed convection from a heated square solid cylinder located at the center of a vented cavity filled with air (Pr = 0.71) is performed. The horizontal walls and the right vertical wall are kept adiabatic, while the left vertical wall is maintained at a constant temperature T c . The flow is assumed to be laminar, steady and of constant physical properties except for the density in the buoyancy term, which follows the Boussinesq approximation. The developed mathematical model is governed by the coupled equations of continuity, momentum, and energy and is solved by the finite-difference method. This study investigates the effects of the outlet positions, Richardson numbers, Reynolds numbers, locations, and aspect ratios of inner square cylinder on the flow and the thermal fields. The parameters studied and their ranges are as follows: the Richardson number and Reynolds number are varied in the ranges from 0–10 and 50–200, respectively, location of the inner cylinder (0.25 ≤ L X ...
TL;DR: In this article, a Galerkin weighted residual finite element method with a Newton-Raphson iterative algorithm is adopted to solve the governing equations for mixed convection heat transfer in a lid-driven cavity along with a heated circular hollow cylinder positioned at the center of the cavity.
TL;DR: In this article, developing turbulent forced convection flow of a water-Al2O3 nanofluid in a square tube, subjected to constant and uniform wall heat flux, is numerically investigated.
Abstract: In this article, developing turbulent forced convection flow of a water-Al2O3 nanofluid in a square tube, subjected to constant and uniform wall heat flux, is numerically investigated. The mixture model is employed to simulate the nanofluid flow and the investigation is accomplished for particles size equal to 38 nm. An entropy generation analysis is also proposed in order to find the optimal working condition for the given geometry under given boundary conditions. A simple analytical procedure is proposed to evaluate the entropy generation and its results are compared with the numerical calculations, showing a very good agreement. A comparison of the resulting Nusselt numbers with experimental correlations available in literature is accomplished. To minimize entropy generation, the optimal Reynolds number is determined.
TL;DR: In this paper, a numerical investigation of steady laminar mixed convection heat transfer in a lid driven cavity with a flexible bottom surface is analyzed, and the authors show that the elasticity of the bottom wall surface plays a significant role on the heat transfer enhancement.
TL;DR: In this paper, the effects of solid volume fraction, aspect ratio and buoyancy forced on thermal and hydraulics behaviors of nanofluid flow in elliptic ducts have been presented and discussed.
TL;DR: In this article, the authors considered three different types of nanoparticles, namely Cu, Al2O3 and TiO2, and found that for each particular nanoparticle, as the nanoparticle volume fraction φ increases, the magnitude of the skin friction coefficient decreases, and this leads to an increase in the value of the mixed convection parameter λ which first produces no separation.
Abstract: Steady mixed convection boundary layer flow from an isothermal horizontal circular cylinder embedded in a porous medium filled with a nanofluid has been studied for both cases of a heated and cooled cylinder. The resulting system of nonlinear partial differential equations is solved numerically using an implicit finite-difference scheme. The solutions for the flow and heat transfer characteristics are evaluated numerically for various values of the governing parameters, namely the nanoparticle volume fraction φ and the mixed convection parameter λ. Three different types of nanoparticles are considered, namely Cu, Al2O3 and TiO2. It is found that for each particular nanoparticle, as the nanoparticle volume fraction φ increases, the magnitude of the skin friction coefficient decreases, and this leads to an increase in the value of the mixed convection parameter λ which first produces no separation. On the other hand, it is also found that of all the three types of nanoparticles considered, for any fixed values of φ and λ, the nanoparticle Cu gives the largest values of the skin friction coefficient followed by TiO2 and Al2O3. Finally, it is worth mentioning that heating the cylinder (λ > 0) delays separation of the boundary layer and if the cylinder is hot enough (large values of λ > 0), then it is suppressed completely. On the other hand, cooling the cylinder (λ < 0) brings the boundary layer separation point nearer to the lower stagnation point and for a sufficiently cold cylinder (large values of λ < 0) there will not be a boundary layer on the cylinder.
TL;DR: In this paper, the authors used a short triangular conductive fin to simulate the flow and temperature fields in a lid-driven square cavity and found that the fin is a good control parameter for heat transfer, temperature distribution and flow field.