LAMINAR MIXED CONVECTION IN A HORIZONTAL SEMICIRCULAR DUCT WITH AXIALLY NONUNIFORM THERMAL-BOUNDARY CONDITION ON THE FLAT WALL

Mixed convection in a horizontal semicircular duct is studied numerical. An axially nonuniform temperature distribution is prescribed on the flat wall, with the midsection at a higher temperature than the end sections. The full three-dimensional Navier-Stokes equations coupled with the energy equation are solved using a control-volume method. Results are presented for two values of the Grashof number (Gr = 5 X 10(3) and 5 X 10(4)) and three values of the Reynolds number (Re = 10, 20, 50), for a gas with Prandtl number of 0.7. For flow conditions characterized by a large value of the parameter Gr/Re2, the buoyancy forces give rise to both longitudinal and transverse rolls in the duct, which cause nonuniformities in the heat flux distribution. The secondary flow pattern and the heat flux distribution on the heated section of the flat wall are strongly dependent on the thermal boundary condition on the curved wall of the duct.