Experimental study of turbulent flow inside a circular tube with longitudinal interrupted fins in the streamwise direction

Experiments were performed to determine the detailed module-by-module pressure drop characteristics of turbulent flow inside circular finned tubes. The tubes were equipped with longitudinal fins interrupted in the streamwise direction by their arrangement in both a staggered and an inline manner. Experiments were carried out for two different fin geometries with hydraulic diameters D-h = 14.89 and 13.46 mm, two different numbers of fins (N = 6 and 12), and two relative fin heights (H/r(0) = 0.5 and 0.3). Air is the working fluid, with Prandtl number 0.7 and Reynolds number ranging from 5000 to 50,000, based on the hydraulic diameter and velocity via minimum cross-sectional area of the tested finned tubes. The velocity profiles for all the tested finned tubes in the direction at the symmetry boundary in the periodic fully developed region were presented. The module-by-module friction factor was found to vary only in the initial modules and then to attain a constant periodic fully developed value after four to six modules. The results showed that, in the periodic fully developed region, the tube pressure drop with continuous fins is higher than that of the inline arrangement of fins and lower than that of the staggered arrangement of fins. (C) Elsevier Science Inc., 1997.