Mixed convection in a horizontal porous duct with a sudden expansion and local heating from below

Results are reported for an experimental and numerical study of forced and mixed convective heat transfer in a liquid-saturated horizontal porous duct . The cross section of the duct has a sudden expansion with a heated region on the lower surface downstream and adjacent to the expansion. Within rite framework of Darcy's formulation, the calculated and measured Nusselt numb ers for 0.1 < Pe < 100 and 50 < Ra < 500 are in excellent agreement. Furthe r, the calculated Nusselt numbers are very close to those for the bottom-he ated flat duct. This finding has important implications for convective hear and mass transfer in geophysical systems and porous matrix heat exchangers . The calculations were also carried out for glass bend-packed beds saturat ed with water using non-Darcy's formula. The streamlines in the forced conv ection indicate that, even with non-Darcy effects included, recirculation i s nor observed downstream of an expansion and the heal transfer rate is dec reased but only marginally.