An empirical correlation of refrigerant flow rate through coiled capillary tubes

Chasik Park, Yonghee Jang, Yongchan Kim, Young Soo Lee

Research output: Contribution to journalArticlepeer-review


Air-conditioners use a spirally coiled capillary tube as an expansion device to enhance compactness of the unit. However, most empirical correlations in open literature were developed for straight capillary tubes without considering coiled effects on the mass flow rate. The objectives of this study are to investigate the flow characteristics of coiled capillary tubes and to develop a generalized correlation for mass flow rate through coiled capillary tubes. The mass flow rates through the coiled capillary tubes and straight capillary tubes were measured by varying operating conditions and tube geometry. The condensing temperatures varied at 40.5, 47.5 and 54.5°C, and subcoolings altered at 3.5, 6.5 and 11.5°C. The mass flow rates of the coiled capillary tubes decreased by 5 to 16% compared with those of the straight capillary tubes at the same operating conditions. An empirical correlation was developed by introducing equivalent length of capillary tube with non-dimensional parameters for coiled shape. The present correlation predicts the data with average and standard deviations of 0.33% and 3.24%, respectively.

Original languageEnglish
Pages (from-to)91-98
Number of pages8
JournalTransactions of the Korean Society of Mechanical Engineers, B
Issue number1
Publication statusPublished - 2007 Jan


  • Coiled capillary tube
  • Empirical correlation
  • Expansion device
  • Mass flow rate

ASJC Scopus subject areas

  • Mechanical Engineering


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