Correlation of two-phase friction for refrigerants in small-diameter tubes

Single-phase and adiabatic two-phase flow pressure drop were measured for R-134A, R-22 and R-404A flowing in a multi-port extruded aluminum tube with hydraulic diameter of 2.13 mm, and in two copper tubes having inside diameters of 6.25 and 3.25 mm, respectively. The single-phase friction factor was predicted within +/-10% using the Blasius friction correlation. The Friedel correlation did not predict the two-phase data accurately, especially for high reduced pressure. Using the data taken in the present and in a previous study, a new correlation for two-phase friction pressure drop in small diameter tubes was developed by modifying the Friedel correlation. The new correlation predicts 119 data points with a mean deviation of 11.5%. (C) 2001 Elsevier Science Inc. All rights reserved.