Numerical Simulation of Natural Convection in an Enclosure Partly Filled with a Porous Medium Saturated with a Nanofluid

Abstract

Natural convection inside an enclosure partly filled with a porous slab saturated with a nanofluid has been investigated numerically using various thermal boundary conditions. The Galerkin finite element method was used to solve the governing equations. Four different scenarios were modelled. Firstly, two-dimensional laminar natural convection in a vertical or a horizontal alignment to the porous-nanofluid layers was investigated with a linearly heated left-hand side enclosure wall. At low values of the thermal conductivity ratio and Darcy number, the heat transfer rate was higher for the horizontal alignment compared to the vertical alignment and vice versa at a high value of the Darcy number. Secondly, the same geometry was studied with a sinusoidally heated left-hand side enclosure wall. It was found that the temperature amplitude and wave number of the sinusoidally heated wall significantly affected the heat transfer rate. At the thermal conductivity ratio < 1 and the Darcy number ≥ 10−3, the heat transfer rate increased in the vertical alignment of the porous-nanofluid layers compared to the horizontal alignment. In both of these scenarios, the porous slab direction inside the enclosure played a significant role on the heat transfer. Thirdly, two-dimensional laminar natural convection of a hybrid nanofluid inside the porous-nanofluid layers using a thermal nonequilibrium model has been simulated. It was found that increasing the modified thermal conductivity ratio and interphase heat transfer coefficient values strongly enhanced the heat transfer rate and satisfy the thermal equilibrium case. Finally, the amplitude and the wave number of the corrugated wall have a significant role on the turbulent natural convection in a three-dimensional enclosure partly filled with porous slab saturated with a hybrid nanofluid. For all scenarios, the lower thickness of the porous slab using the nanofluid predicted a new trend of the fluid flow and heat transfer compared to the porous enclosure.