Natural convection heat transfer in a porous matrix with significant fluid property changes

Natural convection heat transfer in a porous matrix with significant fluid property changes under high pressure and temperature is analyzed by a finite element method. A specific problem involves convection in a square box heated from one side. The fluid properties are mostly tabulated from a steam table, but the viscosity is calculated from temperature and density. It is found that the average heat transfer characteristics with significant fluid property changes do not differ much from those with Boussinesq approximation, if the Rayleigh number is defined at the algebraic mean temperature. However, local Nusselt numbers and temperature fields exhibit measurable deviations, primarily due to significant viscosity changes.