Temperature and entropy generation behavior in rectangular ducts with 3-D heat transfer coupling (conduction and convection)

Temperature and entropy generation fields are evaluated for 3-D heat transfer coupling (conduction and convection) using a mathematical and computational model. Results are obtained from numerical simulation and analyzed for conditions of fully developed laminar flow inside rectangular ducts. Thermal boundary conditions, at the walls cross section and axial direction, are non-uniform and not imposed. A numerical method of modified TDMA algorithm combined with an iterative solution for the system of algebraic equations obtained was developed. Equations were discretised by finite differences. Convergence is guaranteed by applying the first law of thermodynamics. Considering the thinness of the walls, conduction effectiveness is well represented as 1-D. The methodology applied considers air, water and oil as working fluids at 300 K and carbon-steel as wall material. Results for these cases are presented with the intention of finding, the best fluid heating conditions as a first approach to the design of heat exchangers systems.