Conjugated natural convection in horizontal annuli partially filled with metallic foams by using two-equation model

The current study presents the natural convection in a horizontally positioned concentric annulus partially filled with highly conductive metallic foams by using a two-equation model for non-equilibrium heat transfer. Annuli with a porous layer sintered on the inner wall (mode I) and on the outer wall (mode II) are compared with each other via numerical simulation. In the metal-foam region, the momentum transfer is described using the Forchheimer and Brinkman-extended Darcy flow model, whereas the energy conservation is described using the local thermal non-equilibrium model. Some numerical treatments are adopted for the conjugated flow and heat transfer in the two regions besides the foam-fluid interface. The effects of some key parameters on heat transfer are discussed. These key parameters include the Rayleigh number (Ra), dimensionless foam thickness, thermal conductivity ratio, porosity, and pore density. The conductiondominated, transition, and convection-dominated regimes are found with increasing Ra. The dimensionless interfacelocation scope for the thermal performance being superior to empty annulus is provided for the two modes. Under the same foam thickness, the Nusselt number of mode I is slightly higher than that of mode II.