Natural convection of nanofluids flow with 'nanofluid-oriented' models of thermal conductivity and dynamic viscosity in the presence of heat source

Purpose - The purpose of this paper is to make a numerical study of natural convection of water-based nanofluids in a square cavity when a discrete heat source is embedded on the bottom wall, applying a 'nanofluid-oriented' model for the calculation of the effective thermal conductivity (Xu-Yu-Zou-Xu's model) and the effective dynamic viscosity (Jang-Lee-Hwang-Choi's model). Another motivation is the numerical solution of the equations of the flow with a meshless method. Design/methodology/approach - A meshless point collocation method with moving least squares (MLS) approximation is used. A test validation study of the numerical method takes place for pure water flow, as well for water/Al₂O₃ nanofluids. The influence of pertinent parameters such as Rayleigh number (Ra), the non-uniform nanoparticle size keeping the mean nanoparticle diameter fixed, the volume fraction of nanoparticles and the location of heat source on the cooling performance are studied. Findings - The presence of a discrete heat source, as well as the various thermal boundary conditions affects the characteristics of the nanofluid flow and heat transfer. When the ratio of minimum to maximum nanoparticle diameter is increased, the local Nusselt number is increased and the heat source temperature is decreased. The increase of solid volume fraction of nanoparticles causes the heat source maximum temperature to decrease and the Nusselt Number to increase. Originality/value - The present study constitutes an original contribution to the nanofluid flow and heat transfer characteristics when a discrete heat source is presence. 'Nanofluid-oriented' models are used for the calculation of the effective thermal conductivity and dynamic viscosity.