Evaluation of Various Ejector Profiles on CO₂ Transcritical Refrigeration System Performance

Area of Science:

• Thermodynamics
• Refrigeration Engineering
• Energy Systems

Background:

• Transcritical carbon dioxide (CO2) cooling systems are gaining traction due to environmental concerns.
• Ejectors offer a potential method for performance enhancement in refrigeration cycles.
• Optimizing ejector design is crucial for maximizing their benefits in CO2 systems.

Purpose of the Study:

• To investigate the impact of different ejector profiles on CO2 transcritical cooling system performance.
• To quantify the energy savings and work recovery achieved by a multi-ejector system.
• To analyze the influence of ejector geometry and operating conditions on exergy destruction.

Main Methods:

• Comparative analysis of an ejector-boosted CO2 refrigeration system against a second-generation layout.
• Operation under transcritical mode at 35 °C motive flow temperature and 90 bar discharge pressure.
• Evaluation of energy input reduction and expansion work loss recovery.
• Exergy analysis to assess system efficiency and destruction.

Main Results:

• Activation of the ejector led to a maximum reduction in input power of 8.77%.
• The multi-ejector block recovered up to 25.4% of expansion work losses with VEJ1 + 2 combination.
• Ejector geometry and operating conditions significantly affect system exergy destruction.
• Deploying the ejector in parallel with the HPV remarkably reduced exergy destruction during expansion.

Conclusions:

• Multi-ejector systems offer substantial energy savings and improved performance in CO2 transcritical cooling.
• Optimized ejector design and parallel configuration with HPV minimize exergy destruction, enhancing overall system efficiency.