Conjugate Mixed Convection in a Horizontal Cylindrical Duct under the Solid Shell Internal Heat Generation

This paper deals with three-dimensional, mixed convection in a cylindrical duct horizontally. This latter is partially subjected to a uniform volumetric heat generation at the solid-liquid interface. The working fluid (water) with a parabolic velocity profile and a constant temperature T۰ enters the tube. The study was carried out for different Richardson numbers values Ri=۰.۱-۸ at Reynolds number Re=۶۰۰. Results were conducted so that to show the influence of Richardson number Ri on the dynamic and thermal fields and local Nusselt number Nu(q,z) and peripherally averaged axial Nusselt number Nu(z). Also, analyses of the results showed that the hydrodynamic effects are manifested by the existence of secondary flow, inducing temperature gradient at a cross-section between the top and bottom of the duct. The reversed flow is observed for a low Reynolds number Re=۱۰. A significant increase in heat exchange is observed in mixed convection compared to pure forced convection flow. Correlations for the variation of average Nusselt number Nu (Ri,z) at the entrance region with Ri and z=z¢/Di and local Nusselt Nu(Ri) number in the hydrodynamics establishment zone are proposed and compared with the present numerical results.

Keywords:

Mixed convection , heat transfer , horizontal duct , local and average Nusselt numbers