Enhanced Heat Transfer with Swirl Duct Under Rolling and Pitching Environment

Abstract

A detailed experimental investigation of heat transfer in a square duct fitted with twisted tape under a rolling and pitching environment is described, with particular reference to the heat transfer augmentation of shipping machinery. This study focuses on the development of an experimental procedure and methods for data processing, the parametric analysis and a selection of measurements that illustrate the manner by which the swinging forces and buoyancy interactively affect the local heat transfer. The swinging Coriolis force and buoyancy influence to a considerable extent the forced convection heat transfer in the swirl duct. Although enhancing the buoyancy level increases the heat transfer as the swirl duct rolls or pitches, the swinging Nusselt number is initially reduced relative to the stationary condition at the weak swinging oscillation, but tends to recover as the swinging force increases. The synergistic effects of harmonic and nonharmonic rolling and pitching oscillations reduce the heat transfer. Hot spots could develop in a swirl duct due to the slow rolling and/or pitching motions if the effect of the swinging oscillations on the heat transfer is not adequately considered. An empirical correlation has been developed for both single-axis and compound swinging conditions which permits the interactive effect of swinging Coriolis and buoyancy forces on forced convection to be quantified and which provides an evaluation of the local heat transfer in a swinging swirl duct.