Mixed convection from a discrete heater in lid-driven enclosures filled with non-Newtonian nanofluids

The transport mechanism of laminar combined convection flow of an incompressible viscous non-Newtonian nanofluid in a shear- and buoyancy-driven enclosure has been investigated in this article. The micropolar fluid model is used for the rheological behavior of the non-Newtonian fluid. A heat source with constant volumetric rate is attached in a part of the bottom wall and the remaining parts are thermally insulated. The vertical walls of the cavity are considered to be adiabatic, while the top wall is cooled and moves from left to right with uniform velocity. The thermal conductivity and the dynamic viscosity of the nanofluid are represented by different experimental correlations that are suitable to each nanoparticles. The finite volume method is applied to solve the dimensionless form of the governing equations. A discussion is provided for the effects of the governing parameters on the local Nusselt number and average Nusselt number along the heat source. It is found that an increase in the vortex-viscosity parameter causes a reduction in the local Nusselt number. As the vortex-viscosity parameter increases by 10 times from 0.5 to 5, the Nusselt number reduces by 15%. Additionally, as the nanoparticle volume fraction increases, the rate of heat transfer increases. As the volume fraction increases by 100% from 0.1 to 0.2, the Nusselt number increases by 86%.