Calculation of the turbulent flow and heat transfer in expanding ducts

Calculations of the flow and heat transfer in expanding ducts of different angles of expansion, different Reynolds numbers, and different swirl numbers are presented. The influence of each of these parameters on the flow patterns and heat transfer coefficients at a constant wall temperature is presented. The calculations were obtained by the solution of the conservation equations of mass, momentum, and energy in their orthogonal curvilinear form over an orthogonal curvilinear grid of which the boundaries coincide with the duct boundaries. A two equation model which comprises the solution of the kinetic energy of turbulence and its dissipation rate was used in the present calculations. The results of the calculations indicate that the separation which is caused by the duct expansion and described by the stream-functions causes an augmentation of the local Nusselt numbers.