Mechanical vapor compressor is an essential component that governs the system performance and stability in the multi-effect desalination (MED) system. The importance of improving mechanical vapor compressor's compressing ability in enhancing the efficiency of multi-effect desalination (MED) system has been stressed for a long time. This study was aimed to investigate the influences of inlet skew angle of the impeller on performance improvement. Four designs of inlet skew angles were attempted at the first stage impeller with 8 degrees, 10 degrees, 15 degrees, and 20 degrees respectively. Three dimensional fluid flows were simplified using periodic model to reduce the computational cost and time required. A good performance was expected as which effectively reduce the losses caused by secondary flow in the flow passage of the impeller. The results show detail flow pattern on decreasing the secondary flow due to incidence angle at the impeller eye and impeller passage. The numerical solutions were performed and allowed the better design. (C) 2011 Elsevier B.V. All rights reserved.