Fully developed, forced convection heat transfer in a rectangular packed duct is analyzed numerically based on a two-dimensional model incorporating the effects of Raschig ring packing on the Ergun equation. The boundary conditions are based on asymmetric heating with only the top wall supplied with a constant heat flux, while the other walls are adiabatic. The numerical predictions are compared with measured temperature profiles and local Nusselt numbers obtained from a large scale packed duct with L/H = 16 and W/H = 8, using Raschig rings of 4.8 cm in size. The prediction represents the experimental data satisfactorily. The volumetric entropy generation of the duct is also evaluated and displayed graphically that shows the distribution of entropy generation due to heat transfer and pressure drop in the duct.