Theoretical and practical comparison of two-phase ejector refrigeration cycles including First and Second Law analysis

• Theoretical analysis and comparison of different two-phase ejector cycles.
• Cycles with vs. without vapor–liquid separator, single vs. dual evaporator.
• Cycles can have identical 1st Law, but different 2nd Law efficiencies.
• Practical advantages of some cycles may influence selection for real applications.

This paper compares the standard two-phase ejector refrigeration cycle with a liquid–vapor separator to two alternate, less commonly considered two-phase ejector refrigeration cycles as well as to a conventional cycle with an expansion valve. An analytical comparison of the different ejector cycles' theoretical COP's is presented and used to show that they have the same theoretical COP. Numerical models are used to further compare the cycles in terms of theoretical COP and availability destruction. The results show that the standard two-phase ejector cycle has lower availability destruction and higher Second Law efficiency than the alternate ejector cycles despite having the same theoretical COP. Some advantages and disadvantages of the different ejector cycles that are not accounted for in the theoretical COP are discussed. The potential practical advantages offered by the alternate ejector cycles show that these and other alternate ejector cycles may be worth additional attention in future studies.