Testing and modeling of a two-phase ejector

Abstract

The ejector expansion refrigeration cycle is a modified vapor compression cycle in which a two phase ejector is used to recover a portion of the work otherwise lost in the expansion valve. The ejector improves cycle performance by increasing compressor inlet pressure and by lowering the quality of the fluid entering the evaporator. Theoretically, a cooling COP improvement of approximately 21 % is achievable for a typical refrigerating cycle and an ideal ejector. If the ejector performed as well as typical single-phase ejectors, an improvement of 12% could be achieved. Previous tests have demonstrated a smaller 3.7% improvement; the difference is in the poor performance of the two-phase ejector. <p>The purpose of this research is to understand the operating characteristics of the two phase ejector and to improve design. A two-phase ejector test rig has been constructed and tested. Preliminary data show performance superior to previously tested two-phase ejectors, but still inferior to single phase ejectors. Ejector performance corresponds to refrigeration cycle COP improvements ranging from 3.9010 to 7.6%. This performance was obtained with an ejector designed from single-phase ejector and wet steam ejector design methods. The poor performance indicates the design methods must be improved for two-phase ejectors. This research has begun the development of design methods for the two-phase ejectors and this research has developed models to describe the fluid dynamics and thermodynamics of the ejector.