Approaching the performance limit for economized cycles using simplified cycles

• A model of a vapor compression cycle with saturated vapor injection was developed.
• Saturated vapor injection through 3 ports is predicted to increase COP by 12%.
• It provides 67% of the improvement possible with continuous two-phase injection.
• Most of the benefits of economization are provided by saturated vapor injection.
• Most of the benefits of injection are provided with a small number of ports.

Modifications such as economization aim to improve the efficiency of vapor compression equipment by cooling the refrigerant during the compression process. A previous study (Mathison et al., 2010) explored the theoretical limit to cycle performance with economizing, which was defined as the performance when a saturated vapor state was maintained in the compressor by continuously injecting a two-phase mixture. However, achieving continuous injection and controlling the quality of the injected refrigerant poses a substantial challenge. Therefore, the current paper investigates the ability of an economized cycle with saturated vapor injection through a finite number of ports to approach the limiting cycle performance. For an air-conditioner using R-410A with an evaporation temperature of 5 °C and a condensing temperature of 40 °C, the model predicts that injecting saturated vapor through three ports will improve the COP by 12%, which is approximately 67% of the maximum benefit provided by economizing in the limiting case.