Natural Convection Heat Transfer of a Nanofluid in a Trapezoidal Enclosure Filled by a Porous Medium ConsideringLocal Thermal Non-equilibrium

In present study, natural convection heat transfer of a nanofluid in a trapezoidal enclosure saturated by a porous medium is investigated. A local thermal non-equilibrium model including three thermal equations for the phases of fluid, nanoparticles and solid porous matrix is utilized. Moreover, in order to determine comprehensive behavior of dispersed nanoparticles inside the fluid phase, a non- homogeneous model (Buongiorno,s model) is employed. Governing equations in present study are transformed into a non-dimensional form and finally are solved by using the finite element method. The obtained results indicate that the increase of Rayleigh number has a significant increase in the average Nusselt number for the fluid phase and a less significant increase in the average Nusselt number for the nanoparticles. In addition, raising of the buoyancy ratio parameter tends to reduce the average Nusselt number for fluid phase and nanoparticles. In other hand, the variation of Rayleigh number and buoyancy ratio parameter shows a less impact on the average Nusselt number for the phase of porous sold matrix.