Mixed convection heat transfer in a radially rotating square duct with radiation effects

The interaction of thermal radiation with laminar mixed convection for a gr ay fluid in a radially rotating square duct is numerically studied. The int egro-differential radiative transfer equation is solved by the discrete ord inates method. The coupled momentum and energy equations are solved by the DuFort-Frankel numerical scheme. Results are presented in a radially rotati ng square duct over a wide range of the governing parameters. The effects o f rotation-induced buoyancy and thermal radiation on the developments of ve locity, temperature, friction factor and Nusselt number are examined in det ail. The axial variations of the fRe and Nu are characterized by a decay ne ar the entrance due to the entrance effect, but the decay is attenuated by the onset of the secondary flow. The predictions also demonstrate that the radiation presents significant effects on the axial distributions of the to tal Nusselt number Nu, and tends to reduce the centrifugal buoyancy effects . In addition, the heat transfer rate increases with the decrease in the co nduction-to-radiation parameter N-c. (C) 1998 Elsevier Science Ltd. All rig hts reserved.