A Comprehensive Review on Performance Enhancement of Vapor Compression Refrigeration Systems Using Nanoparticle-Enhanced Refrigerants and Capillary Tube Optimization

Abstract

Vapor Compression Refrigeration Systems (VCRS) are widely used in domestic, commercial, and industrial applications due to their reliability and compact design. However, increasing energy demand and environmental concerns associated with conventional refrigerants have driven researchers to explore advanced techniques for improving system efficiency. One promising approach involves the use of nanoparticle-enhanced refrigerants (nano-refrigerants) and optimization of expansion devices such as capillary tubes. This review paper presents a comprehensive analysis of recent research on the application of metal and metal-oxide nanoparticles, including CuO, SiO?, Al?O?, ZnO, and MnO?, dispersed in conventional refrigerants such as R134a. The influence of nanoparticle type, concentration, stability, and capillary tube diameter on system performance parameters—such as coefficient of performance (COP), heat transfer rate, compressor power consumption, and pressure characteristics—is critically reviewed. The study highlights performance improvements reported in experimental and numerical investigations and discusses the challenges related to nanoparticle dispersion, system compatibility, and long-term reliability. Future research directions for achieving sustainable and high-efficiency refrigeration systems are also outlined.

Introduction

Vapor Compression Refrigeration Systems (VCRS) are widely used in domestic, medical, and industrial applications but face challenges related to high energy consumption and environmental impact from high-GWP refrigerants. Improving their thermal performance and energy efficiency has therefore become an important research focus.

Nanotechnology offers a promising solution through the use of nano-refrigerants, which are created by dispersing nanoparticles such as CuO, Al?O?, SiO?, ZnO, TiO?, and MnO? into conventional refrigerants. These nanoparticles enhance thermal conductivity, improve boiling and condensation heat transfer, reduce compressor power consumption, and increase the coefficient of performance (COP). Experimental studies have reported COP improvements of 10–25%, with hybrid nanoparticles showing even greater enhancements due to synergistic effects.

The capillary tube, a key expansion device in small-scale refrigeration systems, significantly influences refrigerant flow and system efficiency. Optimizing capillary tube diameter in combination with nano-refrigerants has been shown to improve pressure drop characteristics, cooling performance, and system stability.

Despite their benefits, nano-refrigerants face challenges such as particle agglomeration, increased viscosity, material compatibility issues, high costs, and long-term stability concerns. Future research should focus on optimizing nanoparticle selection and concentration, improving stability and durability, developing cost-effective and eco-friendly nanoparticles, integrating nano-refrigerants with low-GWP refrigerants, and using numerical modeling to optimize capillary tube design.

Conclusion

This review highlights the significant potential of nanoparticle-enhanced refrigerants and capillary tube optimization in improving the performance of vapor compression refrigeration systems. Experimental and numerical studies consistently demonstrate improvements in heat transfer and COP with the use of nano-refrigerants, particularly hybrid nanoparticle combinations. While challenges related to stability, cost, and system compatibility remain, continued research and technological advancements are expected to pave the way for sustainable and energy-efficient refrigeration systems in the near future.

References

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Copyright

Copyright © 2026 Harendra Bind, Amit Shrivastava . 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.