Potential benefits of saturation cycle with two-phase refrigerant injection

• A saturation cycle is proposed to enhance the vapor compression cycle performance.
• Two-phase refrigerant injection technique is applied to the multi-stage cycle.
• Modeling results of the proposed cycle show the significant performance improvement.
• Low GWP refrigerants are applied and R123 shows the highest performance.
• New parameters, α and ε, are used to show the potential of the saturation cycle.

In this paper, a saturation cycle is proposed to enhance a vapor compression cycle performance by reducing thermodynamic losses associated with single phase gas compression and isenthalpic expansion. In order to approach the saturation cycle, a two-phase refrigerant injection technique is applied to the multi-stage cycle. This multi-stage cycle with different options is modeled, and its performance is evaluated under ASHRAE standard operating conditions for air conditioning systems. Moreover, the two-phase refrigerant injection cycle is compared with the typical vapor injection cycle which is utilizing the internal heat exchanger or the flash tank. Low GWP refrigerants are applied to this two-phase refrigerant injection cycle. In terms of the COP and its improvement, R123 has a higher potential than any other refrigerants in the multi-stage cycle. Lastly, practical ideas realizing the saturation cycle are discussed such as multi-stage phase separator, phase separator with helical structure inside, and injection location of the compressor.