Abstract
The local and volumetric heat transfer and entropy generation analysis of natural convection is carried out using Lattice Boltzmann method in a cavity with refrigerant rigid body and filled with MWCNT-MgO (15% - 85%)/Water nanofluid. To increase the accuracy of the results and avoid wrong predictions of theoretical correlations, the thermo-physical properties of nanofluid are measured experimentally in five solid volume fractions of 0.25, 0.5, 1, 1.5 and 2 vol% in a temperature range of 300 to 340 (K). To utilize these results, some correlations for dynamic viscosity and thermal conductivity in terms of temperature and solid volume fraction are developed and used in the numerical simulations. The considered cavity is heated with constant and uniform temperature from side walls, the top and bottom walls are insulated and the refrigerant rigid body has constant and uniform cold temperature. The influences of different governing parameters such as Rayleigh number, solid volume fraction and refrigerant rigid body configuration on the local Nusselt variation, fluid friction irreversibility map, heat transfer irreversibility map, average Nusselt number, volumetric entropy generation, Bejan number, fluid flow and temperature field are resented comprehensively. It is concluded that the configuration of refrigerant rigid body has pronounced effect on the fluid flow, heat transfer and entropy generation. Furthermore, the Nusselt number has direct relationship with Rayleigh number and solid volume fraction, and the entropy generation has direct and reverse relationship with Rayleigh number and solid volume fraction, respectively. (C) 2017 Elsevier B.V. All rights reserved.