Thermodynamic potential of using a counter rotating novel axial impeller to compress water vapor as refrigerant

摘要

This paper investigates the thermodynamic potential of using multi-stage variable speed counter rotating axial impellers as part of a water chiller system to compress water vapor (R718) as refrigerant. For this multi-stage compressor a modified cycle with an intercooling strategy is used between stages. Multi-stage compression with flash intercooling results in at least 30% improvement of coefficient of performance (COP) at full load compared to conventional refrigerants like R134a. Novel axial composite impellers, manufactured at extremely low cost, are proposed to take the compression role. To predict this counter rotating axial impeller's thermodynamic capacity, a numeric CFD approach is taken in the study to generate steady state performance maps; based on the maps it is found that maximum pressure ratio of single counter rotating stage reaches 1.3 with isentropic efficiency around 70%. The aim of this study is to demonstrate that this counter rotating novel axial impeller has the potential to produce a high enough pressure ratio, and with a practical isentropic efficiency, in a multi-stage compressor to compress water vapor as refrigerant.