Regular Article

Numerical analysis of Al₂O₃/water nano-fluids natural convection and entropy generation in enclosures^*

Laboratoire des Sciences et Ingénierie Maritimes, Faculté de Génie Mécanique, USTO Mohamed Boudiaf, BP 1505 El M’naouer Oran, Algeria

^a e-mail: warda.boudaoud@univ-usto.dz

Received: 27 January 2017
Revised: 4 March 2017
Accepted: 6 March 2017
Published online: 12 May 2017

Abstract

The aim of this work is to analyze the natural convection phenomena and entropy generation of water-based Al₂O₃ nanofluids in square enclosure. The simulated domain corresponds to a square cavity heated from below and cooled from the top. The left and right walls are heated up to a height H = (3/4 W) and are adiabatic in the remaining part (1-H). Numerical investigations have been carried out based on coupled partial differential equations of momentum and energy which are solved using finite volume method. The effective thermal conductivity of the nanofluid was expressed by the Maxwell-Garnetts model however the dynamic viscosity was calculated according to the Brinkman formula. The obtained results were presented by average Nusselt number, streamlines, isotherms and entropy generation with various pertinent parameters, namely, Rayleigh number (10⁰ ≤ Ra ≤ 10⁶), volumetric fraction of nanoparticles (1% ≤ ϕ ≤ 4% ). It was found that the heat transfer increases with the increase of Rayleigh number and volume fraction. The choice of these parameters is important to obtain maximum enhancement of heat transfer with minimum entropy generation.