Development of general correlations for pressure drop in single-phase turbulent flow inside internally helically grooved tubes

Experiments investigating the pressure drop and heat transfer in single-phase turbulent flow inside internally helically grooved tubes were carried out using fourteen helically grooved tubes and a smooth tube with outer diameters of 6.35 mm. The range of geometric parameters of the test tubes were number of grooves, 45 to 65, helix angle, 16 to 26 deg., and groove height, 0.2 to 0.3 mm. In the experiments, water was used as a test fluid; its inlet temperature was kept at 16 to 18 degrees C and the flow rate was varied from 0.03 to 0.11 kg/s. From the data obtained, we found that the friction factor increased with increasing helix angle and ratio of inner surface area of the grooved tubes to that of the smooth tube; and decreased with increasing number of grooves. Correlations for predicting the friction factor were developed based on measured data. The correlations could predict the experimental data within +/- 10% and data reported in the literature within +/- 20%.