Thermodynamic and Property-Driven Evaluation of Low-GWP Refrigerants as Alternatives to R-134a in VCR Systems

Abstract

The global phase-out of high-global warming potential (high-GWP) refrigerants has intensified the search for environmentally benign and energy-efficient alternatives to R-134a in vapor compression refrigeration systems (VCRS). This study presents a comprehensive thermodynamic evaluation of low-GWP refrigerants, including R-152a, R-515B, R-1234ze(E), R-1234yf, R-290, R-600a, R-600, and R-1270, as potential replacements for R-134a. A steady-state thermodynamic cycle model was developed, incorporating fixed superheating and subcooling levels, with simulations conducted for evaporator temperatures between −10°C and 15°C and condenser temperatures between 10°C and 50°C. Key performance indicators such as coefficient of performance (COP), compressor power consumption, and refrigerant mass-flow rate were calculated and normalized relative to R-134a. The results show that hydrocarbon refrigerants (R-600a and R-600) achieve up to 3%–4% higher COP than R-134a, while R-152a provides approximately 3%–4% COP improvement with reduced compressor power (~ 4%). In contrast, R-1234yf exhibits 4%–5% lower COP and 2%–5% higher compressor power, whereas R-290 and R-1270 show moderate efficiency penalties of 1%–3%. R-515B and R-1234ze(E) demonstrate near-baseline performance, with COP variations within ±1% of R-134a. Mass-flow rate reductions of 40%–50% are observed for hydrocarbons and R-152a due to higher latent heat, while R-1234yf requires 25%–28% higher flow rate. The results further reveal that performance trends are strongly governed by latent heat, thermal conductivity, viscosity, and reduced pressure. Overall, low-GWP refrigerants can deliver comparable or superior thermodynamic performance to R-134a, though trade-offs between efficiency, compressor loading, and volumetric capacity must be considered. These findings provide practical guidance for selecting sustainable refrigerants that balance environmental impact and operational efficiency in future cooling system design.