Measurements of Fully-Developed Augmented Convection in a Symmetrically Grooved Channel

Abstract

Measurements of fully-developed augmented convection and pressure drop of air flow in an isothermal, symmetrically grooved channel are reported for channel Reynolds numbers ranging from 800 to 5,000. Grooves, oriented transverse to the flow, are of triangular shape with dimensions that are comparable to the hydraulic diameter of the channel. The grooved section is designed to excite instabilities in the flow leading to increased mixing at sub-transitional Reynolds numbers. Local heat transfer measurements are made using a holographic interferometer. Interferograms, representative of the cross-span-average temperature of the air in the channel, are analyzed to produce data records of the air temperature distribution and the local heat flux along the grooved walls. Heat flux distributions are spatially averaged to produce a correlation of fully-developed Colburn j-factor for this surface configuration. A performance evaluation of the grooved surface applied to a simple heat exchanger shows that it provides thermal performance which is comparable to other surfaces commonly employed in compact heat exchangers.