Atomization and deposition rates in vertical annular two-phase flow

The two-phase annular regime is characterized by a high velocity gas stream flowing through the core of the tube surrounded by a thin, highly agitated liquid film flowing concurrently along the tube wall. Part of the liquid may be entrained as droplets in the gas phase.; The specific goals of this study were to measure fully developed rates of interchange and entrained fraction over a wide range of flow variables in the upward configuration of the annular regime, to obtain a more fundamental understanding of liquid interchange phenomena via studies of liquid film characteristics and to develop an improved design correlation for the entrained fraction.; Towards this end, air-water experiments have been conducted in two vertical pipe lines, 2.54 and 4.20 cm in diameter. Air velocities ranging from 20 to 120 m/s and total liquid flow rates ranging from 10 to 100 g/s were investigated. The steady film tracer technique was used to measure fully developed rates of interchange. A new procedure, employing flush mounted electrode probes, was developed to obtain the tracer concentration in the liquid film. This technique allowed non intrusive, in situ measurement of the tracer concentration while providing simultaneous information concerning liquid film characteristics.; Two models for the rate of atomization, proposed by Tatterson (1975) and Leman (1985), have been examined in light of the data obtained in this study. In order to investigate atomization mechanisms and further substantiate theoretical proposals, a study of the relationship between liquid film flow rate and liquid film characteristics was also undertaken.; Deposition rates in the annular two-phase flow regime have been modeled using a turbulent particle diffusion model. As a result of this analysis, a new empirical relation for the rate of deposition has been proposed. An analysis of the momentum loss due to droplet interchange has also been performed, thus allowing a critical evaluation of an interfacial friction factor correlation developed by Asali (1984).; Finally, several design equations for the equilibrium entrained fraction were reviewed in light of the results of this study and an improved correlation proposed.