Augmentation of Turbulent Convective Heat Transfer in Tubes with Three-dimensional Internal Extended Surfaces

Abstract

This article presents the experimental results on heat transfer and friction characteristics inside fourteen tubes with three-dimensional internal extended surfaces for the turbulent flow of water and an aqueous solution of ethylene glycol (55% ethylene glycol by weight). During the experiments, Reynolds numbers of the fluid ranged from 5,000 to 80,000, and Prandtl numbers from 2.9 to 13.8. Influences of the fin geometric parameters and thermophysical properties of the working fluid on heat transfer and friction characteristics are discussed. The experimental results show that the heat transfer coefficient could be enhanced up to 4-fold over smooth tube with three-dimensional internal extended surfaces and the friction factor was also increased by almost 4-fold for the turbulent flow of water. By using a heat-momentum transfer analogy, heat transfer and friction correlations are obtained which are suitable over wider variations of thermophysical properties and operating conditions.