Visual measurements of droplet size in gas–liquid annular flow

Drop size distributions have been measured for nitrogen–water annular flow in a 9.67 mm hydraulic diameter duct, at system pressures of 3.4 and 17 bar and a temperature of 38 °C. These new data extend the range of conditions represented by existing data in the literature, primarily through an increase in system pressure. Since most existing correlations were developed from data obtained at lower pressures, it should be expected that the higher-pressure data presented in this paper would not necessarily follow those correlations. For two volume median correlations tested, one does not predict the new data very well, while the other only predicts those data taken at the lower pressure of 3.4 atm. An existing maximum drop size correlation predicts the current data to a reasonable approximation. Similarly, a related correlation for the Sauter mean diameter can predict the new data, provided the coefficient in the equation is adjusted.