Thermodynamic analysis of convective heat transfer in an annular packed bed

A combination of the first and second law of thermodynamics has been utiliz ed in analyzing the convective heat transfer in an annular packed bed. The bed was heated asymmetrically by constant heat fluxes. Introduction of the packing enhances wall to fluid heat transfer considerably, hence reduces th e entropy generation due to heat transfer across a finite temperature diffe rence. However, the entropy generation due to fluid-flow friction increases . The net entropy generations resulting from the above effects provide a ne w criterion in analysing the system. Using the modified Ergun equation for pressure drop estimation and a heat transfer coefficient correlation for an annular packed bed, an expression for the volumetric entropy generation ra te has been derived and displayed graphically. In the packed annulus, the f ully developed temperature profile and the plug flow conditions have been a ssumed and verified with experimental data. The volumetric entropy generati on map shows the regions with excessive entropy generation due to operating conditions or design parameters for a required task, and leads to a better understanding of the behavior of the system. (C) 2000 Elsevier Science Inc . All rights reserved.