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Effects of air impurities on the condensation behavior and thermophysical properties of isobutane (R600a) under typical refrigerator operating conditions.

Author(s) : HASAN R., JEONG J. H.

Type of article: IJR article

Summary

Refrigerants in vapor compression refrigeration systems are often contaminated with air due to incomplete evacuation prior to refrigerant charging. The presence of residual air hinders heat transfer and reduces the energy efficiency of these systems. In this study, the condensation behavior and thermophysical properties of isobutane (R600a) mixed with 0 to 2.5% mass fraction of air (N 2 and O 2 ) are investigated using molecular dynamics (MD) simulations over a temperature range of 260 K to 330 K. The microscopic condensation process and the dissolution behavior of air molecules are analyzed to provide insight into molecular interactions during the condensation of R600a/air mixtures. The presence of air disrupts the condensation process by delaying nucleation. Consequently, both the saturated vapor and saturated liquid temperatures decrease. These saturation temperatures are determined for various air concentrations, and a corresponding phase diagram is constructed. The temperature glide increases with air content, reaching up to 32.16 K at 2.5% air for 6.82 bar. Furthermore, the MD simulation results are analyzed to obtain thermophysical properties, including density, internal energy, thermal conductivity, specific heat, viscosity, and phase behavior of R600a/air mixtures. The presence of air appears to induce layering of R600a molecules and disrupts energy uniformity within the system, thereby altering the condensation behavior of R600a during the vapor-to-liquid phase transition. This study provides novel molecular-level insights into how small amounts of air influence the thermophysical properties and phase- change behavior of R600a, which are valuable information for researchers in refrigeration and heat pump sys tems.

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Pages: 20 p.

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Details

  • Original title: Effects of air impurities on the condensation behavior and thermophysical properties of isobutane (R600a) under typical refrigerator operating conditions.
  • Record ID : 30034482
  • Languages: English
  • Source: International Journal of Refrigeration - Revue Internationale du Froid - vol. 181
  • Publication date: 2026/01
  • DOI: http://dx.doi.org/10.1016/j.ijrefrig.2025.11.014

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