A numerical study based on a two-fluid model to describe the fluid-dynamic behaviour of the two-phase flow inside ducts is presented. The discretization of the governing equations has been developed by means of the finite volume technique using a staggered mesh. A semi-implicit pressure-based method is used to couple the fluid conservation equations. Different empirical correlations have been used to evaluate the mass, momentum and energy exchanged through the interface, gas and liquid distribution in the tube, and other terms which appear in the conservation equations. These correlations are used depending on the flow regime map, which is function of the gas volume fraction and velocities. The instability of the two-fluid model due to the equations system is non-hyperbolic has been analyzed. Different two-phase flow cases have been solved by means of the method proposed in this paper. After a verification process to assess the quality of the numerical results obtained, the results are compared, when possible, with analytical solutions, and also with experimental data obtained by the authors. (C) 2012 Elsevier Ltd. All rights reserved.