Natural convection in a nanofluid filled concentric annulus between an outer square cylinder and an inner elliptic cylinder

The lattice Boltzmann method is applied to investigate the natural convection flow of a nanofluid in a concentric annulus between a cold outer square cylinder and a heated inner elliptic cylinder. In order to simulate the effective thermal conductivity and viscosity of nanofluid, Maxwell-Garnetts (MG) and Brinkman models are used, respectively. This investigation is compared with other numerical methods and found to be in excellent agreement. Numerical results for flow and heat transfer characteristics are obtained for various values of the nanoparticle volume fraction, Rayleigh number and eccentricity. The results show that the minimum value of enhancement of heat transfer occurs at epsilon = 0.95 for Ra = 10(5), but, for other values of Rayleigh number, is obtained at epsilon = 0.65. (C) 2013 Sharif University of Technology. All rights reserved.