The paper presents the results of numerical CFD modeling of two-phase flow ejector operation. In the analyzed ejector, the direct-contact condensation phenomenon occurs when the motive water is in contact with the sucked-in superheated steam. Presented in the paper device is a two-phase water-driven ejector condenser which distinguishes it from most such gas-driven devices and is one of the critical components of the developed gas power plant with negative CO2 emission. CFD modeling is a powerful tool and gives the opportunity to analyze combined phenomena such as turbulent flow, multiphase flow, and condensation process in the complex geometrical models at steady and unsteady states. The geometrical model of the ejector was developed to enable condensation in the one flow pass and generate low pressure and the inlet of the gas. To calculate the velocity and pressure distribution, the geometrical design was simplified to the 2D axisymmetric ejector model. The CFD model was created using Simcenter STAR CCM+ software. The RANS approach was used in turbulent flow simulation, and the Euler-Euler approach was applied to multiphase flow modeling. As a result of the study, the influence of condensation on the operation of ejector condenser has been assessed. The pressure and velocity distribution result can help investigate the ejector design factors and evaluate the presented solution's performance. Temperature distribution can confirm existing places where the high differences of temperature exist and where the condensation process is the most intensive.