Entropy generation in a rectangular packed duct with wall heat flux

The entropy generation due to heat transfer and friction has been calculate d 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 expres sion 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 calc ulate the nonisothermal temperature profiles along the flow passage. The ve locity profile takes into account the increase in the velocity near the wal l due to the higher voidage in this region of the bed. The effect of the as ymmetric heating on the velocity profile is neglected under the thermal con ditions considered. The volumetric entropy generation rate and the irrevers ibility 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 t he optimality criterion of equipartition of entropy generations should be c onsidered separately for these regions of the packed duct. (C) 1999 Elsevie r Science Ltd. All rights reserved.