NUMERICAL CALCULATIONS OF HEAT TRANSFER AND FRICTION CHARACTERISTICS IN RECTANGULAR DUCTS WITH SLIT AND SOLID RIBS MOUNTED ON ONE WALL

Abstract

The present work concerns development and application of a turbulent model for heat transfer and fluid flow characteristics in rectangular ducts with slit and solid ribs mounted on one wall. The numerical approach is based on the finite-volume technique, and a nonstaggered arrangement is employed. The SIMPLE algorithm is used for handling the pressure–velocity coupling. The k –ϵ turbulence model with wall function is used as a reference. The parameters studied include the entrance flow Reynolds number ( Re  = 8,000, 15,000, 33,000, and 58,000) and rib void fraction ( b  = 0.211, 0.307, and 0.489), whereas the rib height-to-duct hydraulic diameter is fixed at 0.167 (H/D _e  = 0.167) and the working medium is air. Relative to a solid rib duct, the slit rib has a lower friction factor owing to less duct blockage. As to the heat transfer effect, both the solid rib and slit rib walls enhanced the heat transfer as compared with the smooth ducts, because both the solid rib and slit rib are mechanisms of heat transfer augmentation. With greater turbulence-mixing effect, the slit-ribbed geometry provides better heat transfer than the solid-ribbed geometry.

Acknowledgments

We would like to thank the National Science Council of the Republic of China for supporting this work under Contract NSC 89-2212-E-006-036.