THERMODYNAMIC ANALYSIS OF CONVECTIVE HEAT-TRANSFER IN A PACKED DUCT WITH ASYMMETRICAL WALL TEMPERATURES

Combination of the first and second law of thermodynamics has been uti lized in analysing the convective heat transfer in a rectangular packe d duct. Raschig ring type of packing in the air flow passage is used t o enhance the heat transfer from uniformly heated front wall to air wh en the other walls are adiabatic. The packing increases wall to fluid heat transfer considerably, hence reduce the entropy generation due to the heat transfer across a finite temperature difference. However, th e entropy generation due to fluid flow friction increases. The net ent ropy generations resulting from the above effects provide a new criter ion in analysing the system. Using the Ergun equation for pressure dro p estimation, an expression for the volumetric rate of entropy generat ion has been derived for a vertical 0.675 m long packed duct (H/W = 0. 31). This expression has been displayed graphically to show the influe nces of physical and geometric parameters on the entropy generation. I ntroduction of packing proves to be a thermodynamically sound augmenta tion technique of convective heat transfer. Copyright (C) 1996 Elsevie r Science Ltd.