Enhancement of Thermohydraulic Performance of Turbulent Flow in Rectangular and Square Ribbed Ducts With Twisted-Tape Inserts

Abstract

The thermohydraulic performance of turbulent flow of air through rectangular and square ribbed ducts with twisted-tape inserts has been experimentally studied. The performance is influenced by the twisted-tape-generated swirl flow and the boundary layer separation, reattachment, and flow recirculation due to the ribs. Correlations developed for friction factor and Nusselt number satisfactorily predict the experimental data. The performance of the ribbed ducts with full-length twisted-tape inserts is found to be better than only ribbed ducts and ducts with only twisted-tape inserts. The regularly spaced twisted-tape elements in specific cases significantly perform better than their full-length counterparts. However, the short-length twisted-tape performance is worse than the full-length twisted tapes.