Thermo vapor compressor (TVC) is simply a steam ejector employed in multi-effect desalination (MED) system. A greater understanding of flow phenomena inside an ejector is important for improving ejector performance. We conducted a computational fluid dynamics (CFD) investigation into the flow structure inside a steam ejector. The study focused on the effects of operating pressure and ejector geometry on the flow structure and performance of the steam ejector. The CFD results were verified with available experimental data. The angle of the converging duct considered the geometrical parameter in this study was varied as 0, 0.5, 1, 2, 3.5 and 4.5 degrees. The ejector with a converging duct angle of 1 has the best performance. (C) 2009 Elsevier Ltd. All rights reserved.