Entropy generation in a rectangular packed duct with wall heat flux

The entropy generation due to heat transfer and friction has been calculated for fully developed, forced convection flow in a large rectangular duct, packed with spherical particles, with constant heat fluxes applied to both the top (heated) and bottom (cooled) wall. An approximate analytical expression for the velocity profile developed for packed bed with H/d(p) > 5 has been used together with the energy equation of fully developed flow to calculate the nonisothermal temperature profiles along the flow passage. The velocity profile takes into account the increase in the velocity near the wall due to the higher voidage in this region of the bed. The effect of the asymmetric heating on the velocity profile is neglected under the thermal conditions considered. The volumetric entropy generation rate and the irreversibility distribution ratios have been calculated and displayed graphically for the values of H/d(p) = 5 and 20. It was found that the irreversibility distributions are not continuous through the wall and core regions, hence the optimality criterion of equipartition of entropy generations should be considered separately for these regions of the packed duct. (C) 1999 Elsevier Science Ltd. All rights reserved.