A Comprehensive Review on Low-GWP HFO Refrigerants and Subcooling Techniques in Vapor Compression Refrigeration Systems

The global transition toward environmentally sustainable technologies has intensified the research and development of low-global warming potential (GWP) refrigerants and performance-enhancing techniques in vapor compression refrigeration (VCR) systems. Among various candidates, hydrofluoroolefins (HFOs) have emerged as leading alternatives to hydrofluorocarbons (HFCs) due to their favorable thermophysical properties and negligible ozone depletion potential (ODP). Concurrently, subcooling strategies such as dedicated mechanical subcooling (DMS), condensate-assisted subcooling (CAS), and nanoparticle-enhanced methods are being investigated to enhance the coefficient of performance (COP) and energy efficiency of VCR systems. This review comprehensively evaluates 27 recent research works that span drop-in replacement studies, system-level simulations, subcooling configurations, and life-cycle environmental assessments. The findings collectively highlight the performance trade-offs, system adaptability, and long-term viability of low-GWP refrigerants like R1234yf, R1234ze(E), and R513A, as well as the role of subcooling in mitigating energy and exergy losses. This synthesis serves as a foundation for researchers and engineers aiming to design efficient and sustainable refrigeration systems aligned with global climate objectives