Showing papers on "Natural convection published in 2016"
TL;DR: In this article, the effect of thermal radiation on Al2O3-water nanofluid flow and heat transfer in an enclosure with a constant flux heating element was explored.
398 citations
TL;DR: In this article, forced convection heat transfer in a semi annulus lid under the influence of a variable magnetic field was studied, and the authors used the Control Volume based Finite Element Method (CVFEM) to solve the governing equations considering both Ferrohydrodynamic (FHD) and Magnetohydrodynamics (MHD) effects.
363 citations
TL;DR: In this paper, the authors provide a brief review of researches on nanofluid flow and heat transfer via semi-analytical and numerical methods and show that the Nusselt number is an increasing function of nanoparticle volume fraction.
Abstract: The use of additives in the base fluid like water or ethylene glycol is one of the techniques applied to augment the heat transfer. Newly an innovative nanometer sized particles have been dispersed in the base fluid in heat transfer fluids. The fluids containing the solid nanometer size particle dispersion are called ‘nanofluids’. Two main categories were discussed in detail as the single-phase modeling which the combination of nanoparticle and base fluid is considered as a single-phase mixture with steady properties and the two-phase modeling in which the nanoparticle properties and behaviors are considered separately from the base fluid properties and behaviors. Both single phase and two phase models have been presented in this paper. This paper intends to provide a brief review of researches on nanofluid flow and heat transfer via semi analytical and numerical methods. It was also found that Nusselt number is an increasing function of nanoparticle volume fraction, Rayleigh number and Reynolds number, while it is a decreasing function of Hartmann number.
308 citations
TL;DR: In this article, the effect of magnetic field dependent (MFD) viscosity on free convection heat transfer of nanofluid in an enclosure is investigated, where the bottom wall has constant flux heating element.
248 citations
TL;DR: In this article, the melting and solidification of a phase change materials (PCM) within three various horizontal annulus configurations including two circular cylinders, one elliptical cylinder in a circular cylinder and one finned cylinder in circular cylinder are investigated numerically in terms of the aspect ratio and the orientation of the ellipse.
238 citations
TL;DR: In this paper, thermal behavior in a vertical and horizontal shell-and-tube energy storage system using phase change materials (PCMs) is investigated and compared using a combined conduction and convection heat transfer model.
226 citations
TL;DR: It is observed that the number of branches in the optimised design increases with increasing Grashof numbers, which is opposite to two-dimensional topology optimised designs, which indicates that carefully tailored and complex geometries may improve cooling behaviour considerably compared to simple heat fin geometry.
205 citations
TL;DR: In this article, the effects of various governing parameters such as nanofluid type, Rayleigh number, volume fraction of nanoparticles and height of the rectangular heated body contained in the cavity on hydrothermal characteristics are studied.
195 citations
TL;DR: In this article, the effect of the electric field on nanofluid viscosity is taken into account and the numerical results show that the voltage used can change the flow shape.
Abstract: Natural convection heat transfer of a nanofluid in the presence of an electric field is investigated. The control volume finite element method (CVFEM) is utilized to simulate this problem. A Fe3O4–ethylene glycol nanofluid is used as the working fluid. The effect of the electric field on nanofluid viscosity is taken into account. Numerical investigation is conducted for several values of Rayleigh number, nanoparticle volume fraction, and the voltage supplied. The numerical results show that the voltage used can change the flow shape. The Coulomb force causes the isotherms to become denser near the bottom wall. Heat transfer rises with increase in the voltage supplied and Rayleigh number. The effect of electric field on heat transfer is more pronounced at low Rayleigh numbers due to the predomination of the conduction mechanism.
181 citations
TL;DR: In this paper, a mathematical model of MHD free convection in an inclined wavy enclosure filled with a Cu-water nanofluid in the presence of an isothermal corner heater has been carried out.
179 citations
TL;DR: In this paper, the authors numerically investigated the laminar mixed-convection heat transfer of different water-copper nanofluids inside a microtube with curvature angle of 90°, using a finite volume method.
TL;DR: In this paper, the authors apply the idea of Caputo-Fabrizio time fractional derivatives to magnetohydrodynamics (MHD) free convection flow of generalized Walters'-B fluid over a static vertical plate.
Abstract: The present article applies the idea of Caputo-Fabrizio time fractional derivatives to magnetohydrodynamics (MHD) free convection flow of generalized Walters’-B fluid over a static vertical plate. Free convection is caused due to combined gradients of temperature and concentration. Hence, heat and mass transfers are considered together. The fractional model of Walters’-B fluid is used in the mathematical formulation of the problem. The problem is solved via the Laplace transform method. Exact solutions for velocity, temperature and concentration are obtained. The physical quantities of interest are examined through plots for various values of fractional parameter: $\alpha$
, Walters’-B parameter $\Gamma$
, magnetic parameter M , Prandtl number Pr, Schmidt number Sc, thermal Grashof number Gr and mass Grashof number Gm. As a special case, the published results from open literature are recovered.
TL;DR: In this paper, the authors have analyzed the effect of additive nanoparticles on heat transfer and entropy generation on laminar natural convection of non-Newtonian nanofluids in the presence of an external horizontal magnetic field in a square cavity.
TL;DR: In this paper, the effects of metal foams PPI (number of pores per inch) and porosity on PCM melting rate, heat storage capacity and heat storage density were investigated.
TL;DR: In this paper, the motion of temperature dependent plastic dynamic viscosity and thermal conductivity of steady incompressible laminar free convective magnetohydrodynamic (MHD) Casson fluid flow over an exponentially stretching surface with suction and exponentially decaying internal heat generation was studied.
TL;DR: In this paper, a numerical investigation is performed on the unsteady natural convection of water-based nanofluid within a wavy-walled cavity under the influence of a uniform inclined magnetic field using the mathematical nano-fluid model proposed by Buongiorno.
Abstract: A numerical investigation is performed on the unsteady natural convection of water based nanofluid within a wavy-walled cavity under the influence of a uniform inclined magnetic field using the mathematical nanofluid model proposed by Buongiorno. The left vertical wavy and right vertical flat walls of the cavity are kept at constant but different temperatures whereas the top and bottom horizontal walls are adiabatic. All boundaries are assumed to be impermeable to the base fluid and nanoparticles. The mathematical model formulated in dimensionless stream function, vorticity and temperature variables is solved using implicit finite difference schemes of the second order. The governing parameters are the Hartmann number, undulation number, wavy contraction ratio, inclination angle of the magnetic field relative to the gravity vector and dimensionless time. The effects of these parameters on the average Nusselt number along the hot wavy wall, as well as on the streamlines, isotherms and isoconcentrations are analyzed.
TL;DR: In this article, a numerical analysis of MHD natural convection in a wavy open porous tall cavity filled with a Cu-water nanofluid in the presence of an isothermal corner heater has been carried out.
TL;DR: In this article, the authors investigated conjugate natural convection-conduction heat transfer in an inclined partitioned cavity filled with different nanofluids on different sides of the partition is numerically investigated by using finite element method.
TL;DR: In this paper, mixed convection heat transfer of nano-fluid flow in vertical channel with sinusoidal walls under magnetic field effect is investigated numerically and the heat transfer and hydrodynamic characteristics have been examined.
TL;DR: In this article, the performance of heat transfer and entropy generation on laminar natural convection of non-Newtonian nanofluids in a porous square cavity have been analyzed by Finite Difference Lattice Boltzmann Method (FDLBM).
TL;DR: In this paper, the authors investigated the natural convection in an annulus between two confocal elliptic cylinders filled with a Cu-Al2O3/water hybrid nanofluid.
Abstract: In the present paper, natural convection in an annulus between two confocal elliptic cylinders filled with a Cu-Al2O3/water hybrid nanofluid is investigated numerically. The inner cylinder is heated at a constant surface temperature while the outer wall is isothermally cooled. The basic equations are formulated in elliptic coordinates and developed in terms of the vorticity-stream function formulation using the dimensionless form for 2D, laminar and incompressible flow under steady-state condition. The governing equations are discretized using the finite volume method and solved by an in-house FORTRAN code. Numerical simulations are performed for various volume fractions of nanoparticles (0 ≤ ϕ ≤ 0.12) and Rayleigh numbers (103 ≤ Ra ≤ 3 × 105). The eccentricity of the inner and outer ellipses and the angle of orientation are fixed at e1 = 0.9, e2 = 0.6 and γ = 0° respectively. It is found that employing a Cu-Al2O3/water hybrid nanofluid is more efficient in heat transfer rate compared to the simil...
TL;DR: It is found that the applied magnetic field can suppress both the natural convection and the entropy generation rate, and the nanoparticles addition can be useful if a compromised magnetic field value represented by a Hartman number of 30 is applied.
Abstract: This paper investigates the entropy generation and natural convection inside a C-shaped cavity filled with CuO-water nanofluid and subjected to a uniform magnetic field. The Brownian motion effect is considered in predicting the nanofluid properties. The governing equations are solved using the finite volume method with the SIMPLE (Semi-Implicit Method for Pressure Linked Equations) algorithm. The studied parameters are the Rayleigh number (1000 ≤ Ra ≤ 15,000), Hartman number (0 ≤ Ha ≤ 45), nanofluid volume fraction (0 ≤ φ ≤ 0.06), and the cavity aspect ratio (0.1 ≤ AR ≤ 0.7). The results have shown that the nanoparticles volume fraction enhances the natural convection but undesirably increases the entropy generation rate. It is also found that the applied magnetic field can suppress both the natural convection and the entropy generation rate, where for Ra = 1000 and φ = 0.04, the percentage reductions in total entropy generation decreases from 96.27% to 48.17% for Ha = 45 compared to zero magnetic field when the aspect ratio is increased from 0.1 to 0.7. The results of performance criterion have shown that the nanoparticles addition can be useful if a compromised magnetic field value represented by a Hartman number of 30 is applied.
TL;DR: In this paper, a trapezoidal enclosure filled with carbon nanotube-EG-water nanofluid using variable properties has been numerically investigated using the finite volume method and the SIMPLER algorithm, the governing equations have been discretized.
TL;DR: In this article, the authors studied free convection in an inclined wavy open porous cavity filled with a nanofluid under an influence of the uniform magnetic field in the presence of right bottom corner heater of the constant temperature.
TL;DR: In this paper, a two-dimensional finite volume based numerical model along with enthalpy-porosity technique is employed to simulate the phase change of storage media during the discharging mode.
TL;DR: In this article, a single-step method was used to study the natural convection of Al 2 O 3 -water nanofluids (formulated with single step method) in detail for volume fractions of 0, 0.05, 0., 0.4 and 0.6% in a rectangular cavity, heated differentially on two opposite vertical walls.
TL;DR: In this article, the authors presented a numerical study of natural convection heat transfer and entropy generation of water-alumina nanofluid in baffled L-shaped cavity, where the left vertical and bottom walls were placed in hot and constant Th temperature and the middle horizontal and right vertical walls were in cold and constant Tc temperature.
TL;DR: In this article, a detailed numerical study is carried out to analyze the impact of fin geometry (including fin-length, fin-ratio and the angle between neighbor fins) and outer tube conductivity on PCM melting process; the influence of the natural convection in the horizontal sleeve-tube unit within the longitudinal fins is further examined.
TL;DR: In this paper, the authors used the Rayleigh number to analyse the contribution of natural convection and an empirical model was developed combining diffusive and convective transport for each type of fluid.
TL;DR: In this article, the influence of induced magnetic field on free convection of Al2O3-water nanofluid on permeable plate by means of Koo-Kleinstreuer-Li (KKL) model is reported.
Abstract: In this paper, the influence of induced magnetic field on free convection of Al2O3-water nanofluid on permeable plate by means of Koo-Kleinstreuer-Li (KKL) model is reported. Impact of Brownian motion, along with the properties of nanofluid, are also taken into account. The resulting equations are solved utilizing Runge-Kutta integration method. Obtained results are examined for innumerable energetic parameters, namely Al2O3 volume fraction, suction parameter, and Hartmann and magnetic Prandtl numbers. Results indicate that the velocity profile reduces with rise of the suction parameter and magnetic Prandtl and Hartmann numbers but it increases with addition of nanoparticles. Shear stress enhances with rise of suction parameter, magnetic Prandtl and Hartmann numbers. Temperature gradient improves with augment of suction parameter.