Prediction of amount of entrained droplets in vertical annular two-phase flow

Abstract Prediction of amount of entrained droplets or entrainment fraction in annular two-phase flow is essential for the estimation of dryout condition and analysis of post dryout heat transfer in light water nuclear reactors and steam boilers. In this study, air–water and organic fluid (Freon-113) annular flow entrainment experiments have been carried out in 9.4 and 10.2 mm diameter test sections, respectively. Both the experiments covered three distinct pressure conditions and wide range of liquid and gas flow conditions. The organic fluid experiments simulated high pressure steam–water annular flow conditions. In each experiment, measurements of entrainment fraction, droplet entrainment rate and droplet deposition rate have been performed by using the liquid film extraction method. A simple, explicit and non-dimensional correlation developed by Sawant [Sawant, P.H., Ishii, M., Mori, M., 2008. Droplet entrainment correlation in vertical upward co-current annular two-phase flow. Nucl. Eng. Des. 238 (6), 1342–1352] for the prediction of entrainment fraction is further improved in this study in order to account for the existence of critical gas and liquid flow rates below which no entrainment is possible. Additionally, a new correlation is proposed for the estimation of minimum liquid film flow rate at the maximum entrainment fraction condition. The improved correlation successfully predicted the newly collected air–water and Freon-113 entrainment fraction data. Furthermore, the correlations satisfactorily compared with the air–water, helium–water and air–genklene experimental data measured by Willetts [Willetts, I.P., 1987. Non-aqueous annular two-phase flow. D.Phil. Thesis, University of Oxford]. However, comparison of the correlations with the steam–water data available in literature showed significant discrepancies. It is proposed that these discrepancies might have been caused due to the inadequacy of the liquid film extraction method used to measure the entrainment fraction or due to the change in mechanism of entrainment under high liquid flow conditions.

[1]  B. A. Bennett,et al.  Flow visualization studies of boiling at high pressure , 1965 .

[2]  Barry J. Azzopardi,et al.  Drops in annular two-phase flow , 1997 .

[3]  J. C. Asali.  Entrainment in vertical gas-liquid annular flows , 1984 .

[4]  G. F. Hewitt,et al.  The motion and frequency of large disturbance waves in annular two-phase flow of air-water mixtures , 1963 .

[5]  Mamoru Ishii,et al.  Generation and Size Distribution of Droplet in Annular Two-Phase Flow , 1983 .

[6]  Michitsugu Mori,et al.  Properties of disturbance waves in vertical annular two-phase flow , 2008 .

[7]  M. Bertodano,et al.  Experiments for entrainment rate of droplets in the annular regime , 2001 .

[8]  I. Willetts.  Non-aqueous annular two-phase flow , 1987 .

[9]  R. M. Nedderman,et al.  Pressure gradient and liquid film thickness in co-current upwards flow of gas/liquid mixtures: Application to film-cooler design , 1965 .

[10]  Mamoru Ishii,et al.  Inception criteria for droplet entrainment in two-phase concurrent film flow , 1975 .

[11]  S. Namie,et al.  Droplet Transfer in Two-Phase Annular Mist Flow : Part 1, Experiment of Droplet Transfer Rate and Distributions of Droplet Concentration and Velocity , 1972 .

[12]  W. A. Crago,et al.  Liquid film flow‐rates in two‐phase flow of steam and water at 1000 lb./sq. in. abs , 1969 .

[13]  G. Hewitt,et al.  Sampling probe studies of the gas core in annular two-phase flow—II: Studies of the effect of phase flow rates on phase and velocity distribution , 1964 .

[14]  R. M. Nedderman,et al.  The coalescence of disturbance waves in annular two phase flow , 1968 .

[15]  Clayton T. Crowe,et al.  Effect of particle size on modulating turbulent intensity , 1989 .

[16]  G. Hewitt,et al.  Annular two-phase flow , 1970 .

[17]  T. J. Hanratty,et al.  Relation of deposition to drop size when the rate law is nonlinear , 1996 .

[18]  M. Ishii,et al.  Flow regime transition criteria for upward two-phase flow in vertical tubes , 1984 .

[19]  R. M. Nedderman,et al.  The motion and frequency of large disturbance waves in annular two-phase flow of air-water mixtures , 1963 .

[20]  Atomization and deposition rates in vertical annular two-phase flow , 1988 .

[21]  M. Ishii,et al.  Droplet entrainment correlation in vertical upward co-current annular two-phase flow , 2008 .

[22]  K. Sekoguchi,et al.  Interfacial structures in upward huge wave flow and annular flow regimes , 1989 .

[23]  Barry J. Azzopardi,et al.  Turbulence modification in annular gas/liquid flow , 1999 .

[24]  Gad Hetsroni,et al.  Particles-turbulence interaction , 1989 .

[25]  Geoffrey F. Hewitt,et al.  Studies of wispy-annular flow using transient pressure gradient and optical measurements , 2000 .

[26]  T. J. Hanratty,et al.  Correlation of entrainment for annular flow in vertical pipes , 2002 .