A thermal vapor compressor (TVC) that is to be adopted for use in a multi-effect desalination (MED) plant is designed with a high entraining performance and is appraised with respect to its stability robustness of operating in the double choking region under abrupt changes in the operating conditions such as the motive and suction steam pressures which can be easily caused due to external disturbances. Firstly the shape of the TVC having a high entraining performance is determined by performing an iterative CFD analysis for the various shape conditions under the given design pressure conditions. Then the entrainment ratio of the TVC is determined numerically in a certain fluctuating range of the operational pressure. Alteration patterns of the entrainment ratio arc then considered to assess whether the working of the TVC transfers to the unstable operating region or not.