The article presents a one-dimensional three-fluid model for solving the stationary flow problem on a two-phase steam-water annular dispersed stream in a vertical heated channel, based on nine balance equations with an equal phase pressure assumed. The validation of the marching algorithm of the described stationary problem has been carried out by comparison with the published experimental data relating to a two-phase flow in a circular pipe under adiabatic conditions for pressures of 3 – 9 MPa, total flow rates of 500 – 3000 kg /(m^2∙s) and internal diameters of 10 and 20 mm. The total pressure differences in the channel were calculated. Good qualitative agreement with experimental data was obtained. Small quantitative disagreements were found. They were shown to be reduced by the refinement of the closing relations.