single stage centrifugal compressor, two-phase ejector, compact R718 water chiller
A novel compact R718 water chiller with integration of a centrifugal compressor stage and two phase ejectors as a second stage compression device is proposed. The paper describes the investigations of this R718 refrigerating cycle. The limitations of the R718 centrifugal compressor stage pressure ratio are discussed, and possibilities for introduction of two-phase ejectors in the R718 refrigerating systems with direct evaporation and condensation are analyzed. The complex thermal and flow phenomena connected with additional compression, desuperheating and condensation inside the two-phase ejector flow field are investigated and performance characteristics are estimated. The thermodynamic processes are shown in pressure – enthalpy and temperature – entropy diagrams. Based on the described thermodynamic model, a computational procedure was generated to evaluate the performance characteristics of this R718 refrigerating unit. The implementation of the two-phase ejector in the R718 centrifugal compressor refrigerating systems causes simplification of the R718 unit, and reduction of their size and cost. The energy efficiency of these refrigerating systems may also be increased.