Natural convection of air and water with variable thermophysical properties about a vertical isothermal flat plate embedded in a Darcy porous medium.

We study the steady laminar flow along an isothermal vertical impermeable and permeable plate embedded in a saturated porous medium for which the Darcy law is valid. The investigation concerns air and water taking into account the variation of their physical properties with temperature in both upward and downward flow. The results are obtained with the direct numerical solution of the governing equations and cover relatively large temperature differences. The Prandtl number varied between 0.54 and 0.86 for air and between 3.83 and 13.18 for water. It is found that the variation of physical properties with temperature play an important role on wall heat transfer and wall shear stress and large departures from the constant properties values are observed. The largest differences of wall heat transfer and wall shear stress from the corresponding constant properties values reach 75% and 357% in air and 42% and 388% in water. [ABSTRACT FROM AUTHOR]