Natural convection in square enclosures differentially heated at sides using alumina-water nanofluids with temperature-dependent physical properties

Abstract

Laminar natural convection of Al 2 O 3 + H 2 O nanofluids inside square cavities differentially heated at sides is studied numerically. A computational code based on the SIMPLE-C algorithm is used for the solution of the system of the mass, momentum, and energy transfer governing equations. Assuming that the nanofluid behaves like a single-phase fluid, these equations are the same as those valid for a pure fluid, provided that the thermophysical properties appearing in them are the nanofluid effective properties. The thermal conductivity and dynamic viscosity of the nanofluid are calculated by means of a couple of empirical equations based on a wide variety of experimental data reported in the literature. The other effective properties are evaluated by the conventional mixing theory. Simulations are performed for different values of the nanoparticle volume fraction in the range 0-0.06, the diameter of the suspended nanoparticles in the range 25-100 nm, the temperature of the cooled sidewall in the range 293-313 K, the temperature of the heated sidewall in the range 298-343 K, and the Rayleigh number of the base fluid in the range 10 3 -10 7 . All computations are executed in the hypothesis of temperature-dependent effective properties. The main result obtained is the existence of an optimal particle loading for maximum heat transfer, that is found to increase as the size of the suspended nanoparticles is decreased, and the nanofluid average temperature is increased.

Effect of Al2O3/water nanofluid on Conjugate Free Convection in a Baffle Attached Square Enclosure

“…The results show that for increasing volume fractions there is certain rate of increase in heat transfer rate. Marta Cianfrini et al [16] analyzed the effect of size of the nanoparticles on heat transfer inside an enclosure filled with Al2O3/water nanofluid and reported that higher the size of the nanoparticles better is the heat transfer. Zoubair Boulahia et al [17] examined the combined effect of copperwater nanofluid and a cold obstacle on heat transfer performance of a square enclosure.…”

Natural convection in an inclined porous triangular enclosure with various thermal boundary conditions

“…These studies provide good understanding in circulation of cardiovascular system, design of solar collectors and geothermal systems. There are plenty of studies in enclosures with different geometries [1][2][3] under various conditions, like, radiation [4], external magnetic field [5], aspect ratio [6], variable fluid properties [7,8], and rotating rod [9]. Aich et al [1] examined natural convection in an isosceles prismatic enclosure and asymmetric flow structure is observed.…”

Numerical investigation on natural convection of nanofluids in an inclined square enclosure with non-uniform heated walls

“…They concluded that nano uid type was a key factor in heat transfer enhancement, and CuO nanoparticles led to a better heat transfer rate than Al 2 O 3 nanoparticles did. Cianfrini et al [15] numerically studied the laminar natural convection of Al 2 O 3 -water nano uids inside square cavities. They found that when the nanoparticle volume fraction increased to an optimal particle loading, the amount of heat transfer of nano uids reached a peak across the enclosure.…”