Laminar mixed convection in the entrance region of horizontal quarter circle ducts

Laminar mixed convection in the entrance region for horizontal quarter circular ducts with the curved wall on top has been investigated. The governing momentum and energy equations were solved numerically using a marching technique with finite control volume approach following the SIMPLER algorithm. Results were obtained for the thermal boundary conditions of uniform heat input axially and with uniform wall temperature circumferentially (H1 boundary condition) with Pr=0.7 and a wide range of Grashof numbers. These results include velocity, temperature distributions, at different axial locations, covering all aspects of flow, axial distribution of local Nusselt numbers and local friction factor. It was found that Nusselt numbers were close to the forced convection values near the entrance region and then decreasd to a minimum as the distance from the entrance increases and then rises due to the effect of free convection before reaching constant value (fully developed). As Grashof number increases Nusselt number and friction factor increases in both developing and fully developed regions.