IRREVERSIBILITY PHENOMENA ASSOCIATED WITH HEAT-TRANSFER AND FLUID FRICTION IN LAMINAR FLOWS THROUGH SINGLY CONNECTED DUCTS

The main objective of this study is to explore the existence of thermo dynamic irreversibility Extrema for laminar fluid flow with heat trans fer under fully developed conditions through different cross-sectional , free-flow area ducts. The evaluation of thermodynamic trade-offs cau sed by simultaneous heal transfer at a finite temperature difference a nd fluid friction will be emphasized in terms of the dimensionless ent ropy generation as a performance criterion. A set of duct geometries u nder investigation included circular, rectangular, square, triangular, sine and a set of longitudinal finned circular tubes. One of the prag matical goals of the analysis is to establish the mutual relationship between the hydrodynamic and thermal aspects using, from one side, the conventional area goodness factor, and from the other side, the therm odynamic performance evaluation criterion. The quantitative results fo r the set of parameters under investigation show that the improvement and/or the deterioration of the performance of one geometry with respe ct to another depend on the duct geometry, the Reynolds number and the inlet-wall temperature ratio for a given fluid and a certain duct len gth. Copyright (C) 1996 Elsevier Science Ltd.