Low Dean Number Convective Heat Transfer in Helical Ducts of Rectangular Cross Section

Abstract

Flow in a torroidal duct is characterized by increased convective heat transfer and friction compared to a straight duct of the same cross section. In this paper the importance of the nonplanarity (torsion) of a helical duct with rectangular cross section is investigated. A previously determined low Dean number velocity solution is used in the decoupled energy equation for the hydrodynamically fully developed, thermally developing case. Torsion, known to increase the friction factor, is found to cause a decrease in the fully developed Nusselt number compared to pure torroidal flow. Therefore, it is recommended that torsion be minimized to enhance heat transfer.