Highlights of an ejector analysis

Ejectors are fluid energy transfer devices which rely on direct fluid momentum exchange in a mixing process. This direct exchange is responsible for the mechanical simplicity of ejector devices. This simplicity is, however, not shared by the analysis of these devices. The great number of variables which are of interest for ejector operations lead to considerable functional complexities. In addition the influence of some of the variables on the ejector performance can be extremely sensitive. These conditions make an intuitive estimate of ejector performances in many cases impossible. The direct momentum exchange process allows, however, the establishment of a very reliable fluid dynamic picture as a basis for the analysis. Details of the mixing process do not enter the analysis and mixing can be treated as a completely independent problem. The simplifying assumption of one dimensional flow has an inherent validity for the fluid momentum considerations. By overcoming the functional difficulties of the analysis very realistic performance predictions can be made for a great variety of operating conditions including those which provide optimum ejector layouts.