Enhancement of Forced Convection Heat Transfer in Tubes Using Staged Tangential Flow Injection. Final Report, June 1987-December 1989

摘要

Experiments using air as the test fluid were carried out to study enhancement in heat transfer in tangential injection induced swirl flow. In the experiments 25.4 mm (1 inch) and 50.8 mm (2 inch) diameter tubes were employed. The tubes were heated electrically. The heated length of the tubes varied from 3.05 m to 3.66 m. Three series of experiments were conducted. In the first series, fluid was tangentially injected in stages through two sets of 5.08 mm (0.2 inch) diameter tubular injectors. In the second series, injection was accomplished through a manifold. In the third series, a 50.8 mm (2 inch) diameter tube instead of 25.4 mm (1 inch) diameter tube used in series one and two was employed, and fluid was injected through a manifold having six 11.1 mm (0.44 inch) diameter passages. In all of the tests Reynolds numbers varied from 15,000 to 57,000. In comparison to single stage injection, fluid injection at several places along the direction of flow can improve net enhancement in heat transfer. With a manifold type of injection through a chamber, which simulates the application of the method in a multi-tube heat exchanger, net enhancement was substantially improved over that for tubular injectors.