Mixed convection takes place when the presence of a temperature difference in a forced-flow field gives rise to density differences and thus to a buoyancy force. Buoyancy influences internal forced-convection heat transfer in ways that depend on whether the flow is laminar or turbulent, up-flow or down-flow and on duct geometry. Laminar mixed convection in vertical or inclined ducts deserves a special interest for its applications in the design of cooling systems for electronic devices or for solar collectors. Flow through and fast porous media attracts considerable research activities in...