Development and verification of general correlations for pressure drop and heat transfer in single-phase turbulent flow in enhanced tubes

Abstract

General correlations are developed and verified for friction factor and heat-transfer coefficient for single-phase turbulent flow in internally augmented tubes. Data from frequently referred investigations were gathered for a wide range of tube parameters with e d , 0.01 to 0.2; p d , 0.1 to 7.0; α 90 , 0.3 to 1.0, and flow parameters Re, 5000 to 250,000 and Pr, 0.66 to 37.6. The data were applied to a linear model to obtain normalized correlations that were then modified to approach smooth tube correlation as the roughness variables became very small. A shape function was included in the friction correlation to account for different rib profiles. These correlations were then verified by independent experiments. Different types of commercial ribbed tubes were tested with water as working fluid under heating conditions. Five wire coil inserts were tested in another apparatus using air under cooling conditions. The parameters tested were Re = 5000–60,000, e d = 0.023–0.127, p d = 0.12–1.17 , and α 90 = 0.34–0.91 . The results proved that the correlations can be successfully applied to a wide range of roughness types and Prandtl number. The present correlations are superior, for this large database, to those presented by other investigators. The friction factor correlation predicts 96% of the database to within ±50% and 77% of the database to within ±20%. Corresponding prediction figures for the heat-transfer correlation are 99 and 69%.