The paper describes the model of a flow of steam with non-equilibrium phase change due to the condensation of sub-cooled vapor. This model is particularly interesting for modeling of flow in steam turbines. The basics of this model follows from the model . The main extension of the model  represents the new droplet growth model which is based on the assumption of the shape of droplet size distribution function and which approximates the polydispersity of wet steam. Additional extensions are related to the empirical corrections of the homogenous nucleation rate, alternative equation of state and regularization of droplet growth speed term. Numerical results are obtained by in-house numerical code based on the symmetrical fractional step method, which is based on a finite volume method for the convection terms with on the Runge-Kutta method for the homogenous nucleation and droplet growth terms. Numerical results for the flow in a convergent-divergent nozzle show the effect of new droplet growth model based on the given shape of droplet size distribution function.