In the present paper, a study of flow pattern in a variable geometry ejector used in solar refrigeration system was conducted in an effort to achieve the optimum geometry and improve the understanding of the important flow behaviors that lead to ejector performance drop. Since the entropy generation is equivalent to performance losses, this parameter was investigated in numerical simulations. The results showed that the mixing phenomenon act as a main role in the entropy generation when the temperature of the condenser is higher than critical temperature, meanwhile the shock event operates the major parameter when the condenser temperature is lower than critical. In addition, a remarkable correlation between the entropy generation and the ejector performance was revealed, and so 37% performance improvement obtained. (C) 2016 Published by Elsevier Ltd.