Purpose and Scope of This Item This Data Item provides information for the design and performance evaluation of ejectors@ jet pumps or injectors in which the primary fluid is steam and the secondary fluid is a liquid or a gas. The terms steam/liquid and steam/gas ejector are employed according to whether the secondary fluid is a liquid or gas. Techniques for the optimum design of a steam driven ejector are presented. The method for steam/liquid ejectors is based on a theoretical analysis@ that for steam/gas ejectors is based on experimental data obtained on a wide range of steam driven ejectors. A performance prediction method for steam/liquid ejectors is also presented@ based on the same theoretical analysis as is used in the design method. A performance prediction method for steam/gas ejectors is discussed briefly.