Limiting Performance of the Ejector Refrigeration Cycle with Pure Working Fluids

Area of Science:

• Thermodynamics
• Refrigeration Engineering
• Chemical Engineering

Background:

• Ejector refrigeration cycles (ERCs) are a promising heat-driven technology with significant energy consumption.
• The ideal cycle's coefficient of performance (COP) lacks working fluid property insights, causing an efficiency gap.
• Understanding working fluid impact is crucial for optimizing ERC efficiency.

Purpose of the Study:

• To derive the limiting COP and thermodynamics perfection for subcritical ERCs.
• To evaluate the ERC efficiency limit considering pure working fluid constraints.
• To analyze the influence of working fluid thermophysical properties on ERC performance.

Main Methods:

• Derivation of limiting COP and thermodynamics perfection for subcritical ERCs.
• Evaluation using 15 pure working fluids.
• Analysis of thermophysical parameters like specific entropy increase and saturated liquid slope.

Main Results:

• The limiting COP is a function of working fluid thermophysical parameters and operating temperatures.
• Limiting COP increases with specific entropy increase and saturated liquid slope.
• R152a, R141b, and R123 demonstrated the best performance with limiting thermodynamic perfections of 86.8%, 84.90%, and 83.67% respectively.

Conclusions:

• Working fluid properties significantly impact ERC efficiency limits.
• Specific thermophysical parameters are identified as key drivers for higher limiting COP.
• Optimal working fluids like R152a, R141b, and R123 offer high thermodynamic perfection for subcritical ERCs.