A prototype ejector system having a nominal cooling capacity of 30 kW was used to study the influence of ejector geometry and operating conditions on the ejector performance. Experiments were realized over a wide parameter range: primary inlet pressure from 1700 to 2900 kPa; secondary inlet pressure from 170 to 550 kPa; outlet pressure from 350 to 1000 kPa. The performance was evaluated in terms of the entrainment ratio and the temperature lift. The experimental results led to the following observations: (a) A simple calculation of the primary mass flow rate can be used for the design of ejector systems; (b) A given ejector operated at fixed primary inlet pressure shows a range of outlet pressures where the entrainment ratio is maximum. A correlation of the optimal entrainment ratio versus the primary pressure is proposed; (c) There is an inverse relationship between the temperature lift and the entrainment ratio; (d) For a fixed primary inlet pressure, the optimal outlet pressure can be set at a given value by the appropriate geometry of the ejector. Finally, a two-plateau behavior of entrainment ratio as a function of outlet pressure was observed, which might be related to an improper nozzle exit position. Crown Copyright (C) 2018 Published by Elsevier Ltd. All rights reserved.