New entrainment rate correlation in annular two-phase flow applicable to wide range of flow condition

Assuming the rate of droplet entrainment is characterized by the ratio of the interfacial shear force to the surface tension force acting on the phase interface, new correlation representing the rate of droplet entrainment in annular-dispersed two-phase flow was developed. Although the correlation is based on the simple assumption, the quasi-equilibrium droplet flow rates measured in many experiments were predicted reasonably well (root mean square error of entrainment fraction was roughly halved comparing with several existing correlations). Its applicability to the non-equilibrium situation was also demonstrated by the numerical calculations using a one-dimensional three-fluid model.