Augmentation of turbulent convective heat transfer in tubes with three-dimensional internal extended surfaces

This article presents the experimental results on heat transfer and frictio n characteristics inside fourteen tubes with three-dimensional internal ext ended surfaces for the turbulent flow of water and an aqueous solution of e thylene glycol (55% ethylene glycol by weight). During the experiments, Rey nolds 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 thermophy sical properties of the working fluid on heat transfer and friction charact eristics are discussed. The experimental results show that the heat transfe r coefficient could be enhanced up to 4-fold over smooth tube with three-di mensional internal extended surfaces and the friction factor was also incre ased by almost 4-fold for the turbulent flow of water. By using a heat-mome ntum transfer analogy, heat transfer and friction correlations are obtained which are suitable over wider variations of thermophysical properties and operating conditions.