Performance study of sub-cooled CO2 trans-critical air conditioning cycle: The combined effect of vapor quality and compressor efficiency

Abstract

Carbon dioxide, one of the most critical potential refrigerants, has little impact on the environment. CO2 trans-critical cycles are an essential topic in air conditioning. The current study investigates the performance of the CO2 trans-critical air conditioning cycle for various parameters. The distinct contribution of this work arises from its emphasis on the interrelated nature of the combined effect of compressor efficiency and vapor quality at the evaporator inlet on the overall performance of the CO2 trans-critical cycle; by filling this knowledge gap, the research endeavours to comprehensively understand the system’s behavior under a wide range of operation conditions. The cycle has been modelled using Engineering Equation Solver (EES) and MATLAB codes and validated against an experimental study. The results showed that the cooling capacity increases by 66% when gas-cooling pressure rises from 100 to 150 bar. Raising vapor quality from 0.1 to 0.5 and lowering the degree of superheat from 12 to 0 °C reduces the cooling capacity by 52.4% and increases the coefficient of performance by 87%. Power consumption of the compressor decreases by 50% by increasing compressor efficiency from 70% to 100% and lowering gas cooling pressure from 110 to 80 bar. While the coefficient of performance of the cycle increases by 111.7% by increasing compressor efficiency from 70 to 100% with a degree of sub-cool from 0 to 6 °C and a degree of superheat from 0 to 12 °C.

Keywords

• Airconditioning
• Efficiency
• Simulation
• Trans-critical CO2
• Vapor Quality

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