Two-phase pressure drop of ammonia in horizontal small diameter tubes: Experiments and correlation

A series of experiments are conducted to investigate the two-phase pressure drop of ammonia in horizontal small diameter tube. The experiments are performed at saturation temperatures of -15.8-4.6 degrees C, and the mass flux range is from 20 to 100 kg m(-2) s(-1). This paper analyzes the influence mechanisms of vapor quality, mass flux, saturation temperature, and tube diameter on the two-phase frictional pressure gradient in detail. Meanwhile, several correlations are compared with all the experimental data and the results show that the Muller-Steinhagen and Heck (1986) correlation gives the best agreement. With the analysis of the major forces for ammonia two-phase flow under the tested experimental conditions, the Reynolds number and Bond number are introduced to modify the Muller-Steinhagen and Heck (1986) correlation. Lastly, a modified correlation is developed with the mean absolute deviation of only 13.5%, and 89.2% of the data are within the +/- 30% error band. In addition, the modified correlation is evaluated based on a complied database which contains 951 experimental data points from 11 published literatures. (C) 2018 Elsevier Ltd and IIR. All rights reserved.