MIXED CONVECTION HEAT AND MASS TRANSFER IN RADIALLY ROTATING RECTANGULAR DUCTS

Abstract

The present work investigates mixed convection heat and mass transfer in the entrance region of radially rotating rectangular ducts with water film evaporation along the porous duct watts. Mechanisms of secondary vortex development in the ducts under various conditions are examined by a vorticity-velocity numerical method. Emphasis is placed on the rotation effects, including both Coriolis and centrifugal buoyancy forces, and the mass diffusion effect on the flow structure and heat transfer characteristics. Results are presented in particular for an air-water vapor system under various conditions. Predicted results show that the effects of liquid film evaporation along the porous duct walls on the mixed convection neat transfer are rather substantial. The magnitude of the evaporative latent heal transfer may be 10 times greater than that of sensible heat transfer. The predictions also demonstrate that the distributions of Nu, Sh⊂z⊂, and fRe are closely related to the emergence, disappearance, growth, and decay of the rotating-induced secondary vortices. Additionally, a higher Nu⊂z⊂ is found for a rectangular duct with a larger aspect ratio ( γ = 2) due to the relatively stronger secondary flows.

Notes

Address correspondence to Professor Kuan-Tzong Lee, Department of Mechanical Engineering, Oriental Institute of Technology, 58, Sze-Chuan Road, Sec. 2, Pan Chiao. Taipei 22064, Hsien, Taiwan, R.O.C.