MIXED CONVECTION HEAT AND MASS-TRANSFER IN RADIALLY ROTATING RECTANGULAR DUCTS

The present work investigates mired convection heat and moss transfer in the entrance region of radially rotating rectangular ducts with wat er film evaporation along the porous duct walls. Mechanisms of seconda ry vortex development in the ducts under various conditions are examin ed by a vorticity-velocity numerical method. Emphasis is placed on the rotation effects, including both Coriolis and centrifugal buoyancy fo rces, and the mass diffusion effect on the flow structure and heat tra nsfer characteristics. Results are presented in particular for an air- wafer vapor system under various conditions. Predicted results show th at the effects of liquid film evaporation along the porous duct walls on the mixed convection Beat transfer are rather substantial. The magn itude of the evaporative latent heat transfer may be 10 times greater than that of sensible heat transfer. The predictions also demonstrate that the distributions of Nu, Sh,, and pie are closely related to the emergence, disappearance, growth, and decay of the rotating-induced se condary vortices. Additionally, a higher Nu(z) is found for a rectangu lar duct with a larger aspect ratio (gamma = 2) due to the relatively stronger secondary flows.