This article provides experimental results on the expansion of a refrigerant inside adiabatic helically coiled capillary tubes. The experimental data were obtained in capillary tubes of 0.787, 0.914 and 1.041 mm… Click to show full abstract
This article provides experimental results on the expansion of a refrigerant inside adiabatic helically coiled capillary tubes. The experimental data were obtained in capillary tubes of 0.787, 0.914 and 1.041 mm internal diameter, 2 and 3 m length, 83 mm coil diameter, mass flow rates between 2.7 and 14.3 kg/h, R134a as refrigerant fluid, and inlet subcooling between 6 and 47 °C. The uncertainties of the results for mass flow rate were below 4.5%. Ten prediction methods from the literature were compared with the experimental data, and the best prediction achieved 11.9% mean absolute error. A novel, general and simple dimensionless correlation for coiled and straight adiabatic capillary tubes based on a regression with an extended database containing eleven different refrigerant fluids is proposed. The correlation predicted the extended database with 5.7% mean absolute error and can be applied for subcooled, two-phase or supercritical inlet conditions.
               
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