This paper is intended to establish a simple three-field model, which gives good agreement with a converging nozzle data previously obtained, The problems encountered in developing a mathematical model for two-phase flow are numerous and generally complex. More particularly, the main difficulties concern the closure relations generally correlated empirically and which govern the various transfers at the interfaces and walls. Our methodology consists in taking into account at first the limits of the annular dispersed configuration before reaching step by step its complete description. Such a procedure underlines the necessity to describe the entrainment and deposition mechanisms in order to get a better annular dispersed two-phase flow understanding.