Rotary compressor, economization, refrigerant injection
While models have previously been developed to investigate scroll compressor performance with a single injection port, the model described in this paper explores the effect of multiple injection ports on the performance of a novel rotary spool compressor. The model includes the effects of heat transfer and leakage and is numerically solved to predict the compressor power consumption and mass flow rate. The injection ports are modeled assuming that saturated vapor is injected at a specified pressure and the timing of the injection process can be controlled. Running at a speed of 1907 rpm with R-22 as the working fluid, an evaporating pressure of 391 kPa, an inlet temperature of 7.6°C, and a discharge pressure of 1890 kPa, the model predicts that adding a single injection port will provide a 12% increase in the coefficient of performance (COP) of the cycle. Adding a second injection port increases the COP by an additional 4% compared to the cycle with a single port, or 16% over the baseline performance of the cycle without economization. The compressor model is also used to investigate the effect of injection pressure, injection port location, and injection port diameter on economized cycle performance.