Radiation effects on mixed convection heat transfer in a vertical square duct

A numerical study has been made of the interaction of the thermal radiation with laminar mixed convection for a gray fluid (a gas that may have partic ulates in suspension) in a vertical square duct. Using the vorticity-veloci ty method, the three-dimensional Navier-Stokes equations and energy equatio ns were solved simultaneously. The integro-differential radiative transfer equation was solved by the discrete ordinates method. Results are presented for a wide range of governing parameters. The effects are emphasized of th ermal buoyancy and radiative transfer on the development of velocity and te mperature fields, the friction factor and the Nusselt number. The results s how that radiation significantly affects the total Nusselt number Nu(t) and tends to reduce the buoyancy effects. In addition, radiation speeds the de velopment of the temperature field. (C) 2001 Elsevier Science Ltd. All righ ts reserved.