In this study, the effect of the position of the primary nozzle and the converging angle of the mixing section is investigated numerically for a vapor jet ejector to be used in a heat-driven ejector refrigeration cycle. Entrainment ratio is reported as one of the global performance parameters which is affected sensitively by the nozzle position and converging angle of the mixing section. Furthermore, the effect of the geometric parameters is also explained using Mach number distributions throughout the ejector. Mach contours and the shadowgraphs of the ejector as well are displayed comparatively. The influence of the secondary flow effective area is discussed for better comprehension of the ejector performance by means of the aforecited geometrical parameters. The importance of this study is that the results can lead to the design of the mixing chamber of the ejector for the heat-driven ejector refrigeration systems. ANSYS Fluent software package is used for computational fluid dynamics simulations taking real gas thermodynamic properties into account and the numerical model was validated using the experimental data from the literature. (C) 2018 Elsevier Ltd. All rights reserved.