Computational Simulation of Swirl Enhanced Flow and Heat Transfer in a Twisted Oval Tube

Abstract

Fully developed swirling Flow in a twisted tube with an oval cross section is considered. The results shown here are for a tube with an elliptical cross section with a twist ratio of 6 and an aspect ratio of 0.7 (see equations above). The wall of the tube is held at a constant temperature. The secondary flows induced by the tube twist promote mixing in the plane normal to the bulk flow direction. This mixing works to maintain a high temperature gradient close to the tube wall and in turn increase the Nusselt number relative to that in a straight tube of the same cross section. The temperature plots show that it is indeed the case that the in‐plane mixing is effective in maintaining the temperature gradient near the tube wall. The isometric view shows flow streamlines (ribbons represent adjacent streamlines) to illustrate the swirling natur eo ft he flow.