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. Calculated and measured Nusselt numbers for 0.1 < Pe < 100 and 50 < Ra < 500 are in excellent agreement. Overall Nusselt numbers are correlated in terms of Nu/Pe¹⁵ and Ra/Pe¹⁵. Calculated Nusselt numbers are very close to those for the bottom-heated flat duct, and this result has several important implications for convective heat and mass transfer in geophysical systems and porous matrix heat exhcangers.