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

Abstract

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.

Introduction

1. Background & Motivation

• Growing concerns over climate change and environmental degradation have led to a global push to phase down high-GWP refrigerants like R134a and R410A, aligning with policies such as the Kigali Amendment.

• Focus has shifted toward low-GWP hydrofluoroolefins (HFOs), such as R1234ze(E), R1234yf, and blends like R513A, due to their low environmental impact and promising thermodynamic properties.

• In parallel, subcooling techniques (e.g., Dedicated Mechanical Subcooling - DMS, Condensate-Assisted Subcooling - CAS) are increasingly used to improve energy efficiency and system performance in VCR systems.

2. Objective of the Paper

• A structured review of 27 peer-reviewed studies, focusing on:

  1. Low-GWP refrigerant performance and environmental assessment

  2. Advanced subcooling strategies to enhance the Coefficient of Performance (COP) and reduce energy usage.

3. Key Findings

A. Low-GWP Refrigerants: Performance vs. Trade-offs

• R1234ze(E) and R1234yf often match or surpass R134a in terms of COP, especially under optimized conditions.

• Blends like R513A and R450A offer a compromise between performance and system compatibility.

• Trade-offs include:

  • Slightly lower cooling capacity

  • Higher compressor power requirement

  • Flammability or redesign needs in some cases

B. Environmental Impact & Lifecycle Assessments

• All HFOs show significant reductions in Total Equivalent Warming Impact (TEWI) and Life Cycle Climate Performance (LCCP).

• Environmental impact must also consider indirect emissions from electricity use.

• Regional energy mix (e.g., fossil vs. renewable) influences the overall sustainability of refrigerants (via the critical emission factor concept).

C. Subcooling Techniques for COP Enhancement

• DMS and CAS consistently improved system COP by up to 33%, reduced energy consumption, and improved compressor life.

• Techniques like nanoparticle-enhanced refrigerants (e.g., CuO) further improved heat transfer efficiency.

• Subcooling reduced exergy destruction in key components (condenser, evaporator), optimizing system performance.

D. Simulation Tools & Data Gaps

• Accurate modeling is crucial for refrigerant evaluation.

  • Tools like Python-based solvers (CoolProp) and regression models have improved real-time simulation.

• Data gaps remain in thermophysical properties of newer refrigerants (e.g., R1336mzz(E)), affecting model accuracy.

E. Challenges in Adoption

• No “perfect refrigerant” exists; trade-offs between flammability, cost, efficiency, and compatibility persist.

• Some high-performance systems (e.g., ejector or hydro-CO? piston cycles) require complex engineering, limiting short-term scalability but offering long-term promise.

Conclusion

The transition toward sustainable and efficient refrigeration systems is gaining momentum through the dual pathways of adopting low-GWP refrigerants—especially hydrofluoroolefins (HFOs)—and integrating subcooling techniques within vapor compression refrigeration systems. This comprehensive review of 27 peer-reviewed studies confirms that refrigerants such as R1234ze(E), R1234yf, and blends like R513A and R450A can function as effective drop-in or modified replacements for R134a, with measurable improvements in energy efficiency and significant reductions in environmental impact. Subcooling strategies, notably dedicated mechanical subcooling (DMS), condensate-assisted subcooling (CAS), and nanoparticle-enhanced systems, were consistently shown to elevate system performance and reduce irreversibilities. While the performance of some HFOs lags marginally behind traditional refrigerants in terms of cooling capacity or COP, their ultra-low GWP values and compatibility with existing infrastructure make them strong candidates for large-scale deployment. However, widespread adoption of low-GWP refrigerants and advanced subcooling techniques requires overcoming challenges such as limited thermophysical data, flammability classifications, system design complexities, and region-specific grid emission factors. As simulation tools and experimental datasets mature, future VCR system development will increasingly rely on integrated optimization frameworks that consider environmental, thermodynamic, and economic parameters concurrently. This review affirms the critical role of HFO refrigerants and subcooling strategies in shaping the next generation of refrigeration systems aligned with global climate commitments.

References

[1] J. Belman-Flores, et al., “Drop-In Replacement of R134a in a Household Refrigerator with Low-GWP Refrigerants R513A, R516A, and R1234ze(E),” 2023. [2] K. Solanki, et al., “Performance Enhancement and Environmental Analysis of Vapor Compression Refrigeration System with Dedicated Mechanical Subcooling,” 2023. [3] R. Prasad, et al., “Experimental and Simulation Study of the Latest HFC/HFO and Blend of Refrigerants in Vapour Compression Refrigeration System as an Alternative of R134a,” 2023. [4] A. Agarwal, et al., “Energy and Exergy Investigations of R1234yf and R1234ze as R134a Replacements in Mechanically Subcooled Vapour Compression Refrigeration Cycle,” 2020. [5] Y. Touaibi and H. Koten, “Energy Analysis of VCR System Using R1234yf and R1234ze as R134a Replacements,” Journal of Advanced Research in Fluid Mechanics and Thermal Sciences, n.d. [6] A. Tarish, et al., “Exergy and Performance Analyses of Impact Subcooling for Vapor Compression Refrigeration System Utilizing Eco-Friendly Refrigerants,” 2020. [7] M. Mclinden and M. Huber, “(R)Evolution of Refrigerants,” 2020. [8] M. Ghanbarpour, et al., “Theoretical Global Warming Impact Evaluation of Medium and High Temperature Heat Pumps Using Low-GWP Refrigerants,” 2021. [9] U. Farooq, et al., “Thermodynamic Performance Analysis of Hydrofluoroolefins (HFO) Refrigerants in Commercial Air-Conditioning Systems for Sustainable Environment,” 2020. [10] A. Pundkar, et al., “Performance Evaluation of LGWP-Series Refrigerants as a Substitute for HFC-134a Air Conditioning System: A Sustainable Approach,” 2025. [11] K. Alsouda, et al., “Vapor Compression Cycle: A State-of-the-Art Review on Cycle Improvements, Water and Other Natural Refrigerants,” 2023. [12] M. Triki, et al., “Exergy Analysis of a Solar Vapor Compression Refrigeration System Using R1234ze(E) as an Environmentally Friendly Replacement of R134a,” 2024. [13] J. Yi, et al., “Performance Evaluation of Centrifugal Refrigeration Compressor Using R1234yf and R1234ze(E) as Drop-In Replacements for R134a,” 2022. [14] A. Gil and J. Kasperski, “Efficiency Evaluation of the Ejector Cooling Cycle Using a New Generation of HFO/HCFO Refrigerant as a R134a Replacement,” 2018. [15] I. Bell, et al., “Survey of Data and Models for Refrigerant Mixtures Containing Halogenated Olefins,” 2021. [16] T. Odunfa and O. Oseni, “Numerical Simulation and Performance Assessment of a Nanoparticle Enhanced Vapour Compression Refrigeration System,” 2021. [17] S. Faraldo, et al., “Optimization of a Highly-Efficient Hydro-CO2 Piston for Commercial Refrigeration,” n.d. [18] M. Sumeru, et al., “A Review on Sub-Cooling in Vapor Compression Refrigeration Cycle for Energy Saving,” 2019. [19] C. Aprea, et al., “HFO1234ze as Drop-in Replacement for R134a in Domestic Refrigerators: An Environmental Impact Analysis,” 2016. [20] D. Gupta, et al., “Thermodynamic Analysis and Effects of Replacing HFC by Fourth-Generation Refrigerants in VCR Systems,” 2018. [21] R. Mishra and M. Khan, “Theoretical Exergy Analysis of Actual Vapour Compression System with HFO-1234yf and HFO-1234ze as an Alternative Replacement of HFC-134a,” 2016. [22] L. Fedele, et al., “Thermophysical Properties of Low GWP Refrigerants: An Update,” 2023. [23] A. Allen, et al., “A Python-Based Code for Modeling the Thermodynamics of the Vapor Compression Cycle Applied to Residential Heat Pumps,” 2023. [24] A. Mota-Babiloni, et al., “A Review of Refrigerant R1234ze(E) Recent Investigations,” 2015. [25] M. Mclinden, et al., “New Refrigerants and System Configurations for Vapor-Compression Refrigeration,” 2020. [26] A. Mogaji, et al., “COP Enhancement of Vapour Compression Refrigeration System Using Dedicated Mechanical Subcooling Cycle,” 2020. [27] A. Olaoke, et al., “Computationally Efficient Property Calculation for Mixed Refrigerants Using Weighted Piecewise Polynomial Regression,” 2024.

Copyright

Copyright © 2025 Akshat Tiwari, Dr. B. K. Chourasia. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.