In the present study, a novel ejector was designed based oil a constant area ejector model and manufactured in order to investigate the performance of an ejector refrigeration system in a wider operating range. The ejector, with movable primary nozzle, was mounted oil the system that was previously constructed for low pressure refrigerants. The modified refrigeration system has been tested using hot water as driving fluid and R123 as working fluid. The effects of the operating temperatures oil the cooling capacity and performance coefficient of the system were investigated experimentally when the primary nozzle position was optimum at the ejector area ratio of 9.97. As a result, a performance coefficient of 0.39 was obtained at the vapor generator temperature 98 degrees C, the evaporator temperature 10 degrees C and critical condenser pressure 129 kPa. (C) 2007 Elsevier Ltd. All rights reserved.