Comprehensive 4Es (Energy, Exergy, Economic, Environmental) Analyses of Dedicated Mechanical Subcooled Vapour Compression Refrigeration Systems Using Low-GWP Refrigerants as R134a substitutes

With increasing restrictions on high GWP refrigerants in refrigeration system, the transition to efficient, climate-friendly alternatives has become necessary. Some efficient low GWP options fall within the A2/A2L flammability class, necessitating strict adherence to safety standards, introducing additional design and cost implications. Despite these challenges, integrated assessments that simultaneously address performance, environmental impact, safety requirements, and economic viability in a dedicated mechanical subcooling refrigeration system (DMS-VCRS) remain scarce. This study presents a comprehensive parametric evaluation of seven R134A substitutes under the DMS-VCRS framework using 4Es (Energy, Exergy, Economic, Environmental) analysis. It includes TEWI-based environmental analysis and safety-economic assessments for A2/A2L refrigerants. The R134a substitute refrigerants that were examined in this work include R1234ze(E), R1234yf, R440A, R450A, R513A, R515A, and R152A. The model of the DMS-VCRS was carried out using STEAG Ebsilon Professional software with REFPROP 9.1 thermophysical property correlation. The model validation demonstrated excellent agreement with the literature (RMSE = 0.0334, MAPE < 3%, R² > 0.997). Parametric studies investigated the influence of condenser temperatures, evaporator temperatures, degrees of subcooling, degrees of superheating, and refrigerant mass-flow ratios on thermodynamics, economics, and environmental impacts performance. R152A and R440A performed better than R134A, achieving a 7% increase in COP, a 6% increase in exergy efficiency, and a 13–22% reduction in Total Equivalent Warming Impact (TEWI) compared to R134A. Reliability-bounded operating ranges for subcooling degrees (22–39.5 °C) and superheating degrees (1.5–37.5 °C), along with other parameters, yielded optimal conditions at 34–37 °C condenser 1 temperature, −4 °C evaporator temperature, and 27.3–32.5 °C and 20–25 °C subcooling and superheating, respectively. The performance of 4Es was consistently and mildly impacted by variations in superheating and subcooling degrees. While indirect emissions from power consumption show a total TEWI (>85%). Their economic competitiveness is demonstrated by the fact that R152A and R440A had the lowest Annual Total Cost Rate (ATCR) (≈5% below R134a) and Total System Cost (TCR-SYS), which was roughly 9% higher than R134a but 12% lower than R1234yf. Although R152A and R440A are mildly flammable (A2), safe operation can be ensured under the IEC 60335-2-89 guideline through charge limitation, leak detection, and ventilation