Performance Evaluation of Low-GWP HFO Refrigerants and Their Blends in a Subcooled Vapor Compression Cycle: A Python-CoolProp Simulation Approach

Abstract

The environmental challenges posed by high-GWP refrigerants like R134a have necessitated the transition toward low-GWP alternatives, notably Hydrofluoroolefins (HFOs). This research presents a detailed simulation-based performance analysis of a Vapour Compression Refrigeration System (VCRS) incorporating a Liquid–Vapour Heat Exchanger (LVHE) to enable mechanical subcooling. Using Python and CoolProp, we compare the thermodynamic behavior of R134a, pure HFOs—R1234ze(E) and R1233zd(E)—and their binary blends across varying subcooling levels (0°C–30°C). An optimal subcooling value of 20°C is established, and a 70:30 blend of R1234ze(E) and R1233zd(E) is proposed as the most viable drop-in alternative to R134a. The results demonstrate substantial improvements in Refrigeration Effect (RE), Coefficient of Performance (COP), and system safety under optimized subcooling. Validation against published benchmarks ensures the reliability of the simulation approach. This study contributes a novel, environmentally conscious refrigerant blend optimized for subcooled VCRS applications, aligning with international climate mandates.

Introduction

Context and Motivation:
Global warming and ozone depletion concerns have driven the phase-out of high-GWP refrigerants like R134a (GWP ≈ 1430) under regulations such as the Kigali Amendment. Hydrofluoroolefins (HFOs), including R1234ze(E) and R1233zd(E), have emerged as promising alternatives due to their ultra-low GWP (<10), zero ozone depletion potential, and compatibility with existing systems. However, research on binary HFO blends, especially under subcooled conditions in refrigeration cycles, remains limited.

Research Focus:
This study integrates mechanical subcooling using a Liquid–Vapour Heat Exchanger (LVHE) within a single-stage VCRS to enhance energy efficiency and environmental compliance. Subcooling improves refrigeration effect and compressor stability while reducing entropy generation. Using Python–CoolProp simulations, the study proposes a novel 70:30 blend of R1234ze(E)–R1233zd(E) as a thermodynamically optimized and eco-friendly replacement for R134a.

Literature Insights:

• HFO Refrigerants:
  Studies show HFOs like R1234ze(E) outperform traditional refrigerants in efficiency and reduce environmental impact. Blends such as R513A and R450A maintain system compatibility while lowering GWP. Mechanical subcooling enhances their performance further, although pure HFOs may require higher input power.

• Subcooling Techniques:
  Mechanical subcooling via LVHEs increases the enthalpy difference in the evaporator, improving system stability and increasing COP by 9–33%. Subcooling reduces vapor fraction at the compressor inlet, thus improving overall cycle efficiency.

• Refrigerant Blends and Properties:
  Blends of R1234ze(E) and R1233zd(E) show promise for balanced performance and environmental benefits. However, accurate thermophysical property data are scarce, and simulation tools like CoolProp and Python-based models are crucial for effective analysis.

• Integration Challenges:
  No refrigerant perfectly meets all criteria (low GWP, high efficiency, low flammability). Regional energy emission factors also influence overall sustainability. Hybrid systems and renewable energy integration offer additional opportunities for improved refrigeration system sustainability.

System Configuration:
The simulated VCRS includes an evaporator, compressor, condenser, expansion valve, and an LVHE placed between condenser and evaporator. The LVHE mechanically subcools high-pressure liquid refrigerant using heat exchange with low-pressure vapor from the evaporator outlet. This process increases the refrigeration effect, reduces compressor workload, and improves COP.

Key Takeaway:

The study proposes an environmentally friendly, energy-efficient refrigeration solution by combining HFO blends with mechanical subcooling, validated through advanced simulation, to support sustainable cooling system design.

Conclusion

This present work undertook a comprehensive simulation-based evaluation of low-GWP refrigerants and their blends in a Vapour Compression Refrigeration System (VCRS) enhanced with a Liquid–Vapor Heat Exchanger (LVHE). Based on the thermodynamic modeling, subcooling analysis, and blend simulations, the following conclusions are drawn: The R1234ze(E):R1233zd(E) (70:30) blend at 20°C subcooling demonstrated the highest COP (2.69) and second-highest refrigeration effect (143.67?kJ/kg) among all tested configurations, while maintaining a favorable lower-moderate operating pressure range (1.12–7.86?bar). Compared to R134a at 0°C subcooling, the blend improved COP by 9.35% and refrigeration effect by 18.69%. When compared to R134a at 20°C subcooling, the blend still achieved a 3.86% higher COP and only a 4.82% lower refrigeration effect, while requiring 8.43% less compressor work. These performance metrics, combined with its ultra-low GWP and safety classification (A2L), make the blend a viable and sustainable replacement for R134a in modern VCR systems. Trends matched previous empirical studies, notably that by Agarwal et al. (2021) verifying simulation correctness and academic robustness. Practical implementation of this blend could be immediate for commercial refrigeration and chillers, requiring only minor design adaptations.

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. [28] C. P. Arora, Refrigeration and Air Conditioning, 3rd ed., New Delhi: McGraw Hill Education, 2013. [29] Y. A. Çengel and M. A. Boles, Thermodynamics: An Engineering Approach, 9th ed., McGraw Hill Education, 2014.

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.