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Thermal performance of flooded evaporator with enhanced tubes and Low-GWP refrigerants.

Author(s) : PAUL S., LASKAR N., DAS M. K.

Type of article: IJR article

Summary

The global transition toward low-GWP refrigerants introduces challenges such as higher operating pressures and mechanical strain on conventional copper (Cu) tubes. While stainless steel (SS) tubes provide superior mechanical stability and corrosion resistance, their low thermal conductivity limits heat transfer. To address this limitation, the present study investigates Cu-coated SS tubes in flooded evaporator applications, focusing on the influence of coating thickness, porosity, and refrigerant selection on HTC. The approach combines numerical
modeling with experimental validation. The results show that Cu-coated SS tubes outperform uncoated SS tubes in HTC, while achieving performance comparable to uncoated Cu tubes. Coating thickness exhibited a non-linear effect, with an optimum at 50 μm, beyond which performance declined due to increased resistance and reduced nucleation activity. Incorporating porosity further improved HTC, with an optimum value of 0.2, balancing nucleation site density and capillary-driven liquid replenishment. The performance of low-GWP refrigerants
R152a and R1234yf was also evaluated against the widely used R134a. For uncoated tubes, R152a achieved up to 3 % higher HTC than R134a and 25 % higher than R1234yf, while coated tubes amplified these advantages to 6 % and 34 %, respectively. Among the refrigerants tested, R152a consistently exhibited the lowest wall-superheat across all heat fluxes, followed by R134a and R1234yf. Consequently, R152a shows potential to replace R134a, whereas R1234yf requires enhanced surfaces to be viable, increasing cost and design complexity. This study highlights that optimally designed Cu-coated SS tubes can drive the development of efficient, compact, and costeffective HVAC systems using low-GWP refrigerants.

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Pages: 17 p.

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Details

  • Original title: Thermal performance of flooded evaporator with enhanced tubes and Low-GWP refrigerants.
  • Record ID : 30034788
  • Languages: English
  • Subject: Technology
  • Source: International Journal of Refrigeration - Revue Internationale du Froid - vol. 185
  • Publication date: 2026/05
  • DOI: http://dx.doi.org/10.1016/j.ijrefrig.2026.02.005

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