Numerical study on the flow over a staggered oval tube for heat-transfer enhancement

A computational study is presented which analyzes details of the flow and heat-transfer behaviors in a staggered oval tube with three-dimensional Navier-Stokes equations. The tube is constructed with a series of alternative vertically and horizontally positioned oval pipes connected by transition sections, which bridge a vertically positioned cross-section to a horizontally positioned one, or vice versa. Results are presented for local as well as overall flow and heat-transfer parameters, including skin-friction coefficient and Nusselt number. It is found that the transition sections contribute most to the promotion of heat transfer but with the penalty of producing the largest pressure drop per unit length. The geometry of the transition section tends to provoke separation bubbles, which not only attenuate local heat-transfer rate but also result in higher pressure-loss. The study demonstrates that, within the range of Reynolds numbers investigated, this configuration can largely enhance heat transfer up to 600% comparing to a circular pipe.