Experimentation and modeling of refrigerant flow through coiled capillary tubes

Chasik Park, Sunil Lee, Hoon Kang, Yongchan Kim

Research output: Contribution to journalArticlepeer-review

55 Citations (Scopus)


Air-conditioners use spirally coiled capillary tubes as an expansion device to enhance compactness of the unit. However, most empirical correlations for predicting refrigerant flow rate through capillary tubes were developed for straight capillary tubes without consideration of coiled effects. The objectives of this study are to investigate the flow characteristics of the coiled capillary tubes and to develop a generalized correlation for the mass flow rate through the coiled capillary tubes. The mass flow rate of R22 through the coiled capillary tubes and straight capillary tubes was measured for various operating conditions and tube geometries. The mass flow rates of the coiled capillary tubes decreased by 5-16% more than those of the straight capillary tubes at the same operating conditions. A generalized correlation for predicting refrigerant mass flow rate through coiled capillary tubes was developed by introducing the parameter of capillary equivalent length. The present correlation showed good predictions with the present database for R22, R407C and R410A in the straight and coiled capillary tubes, yielding average and standard deviations of 0.24% and 4.4%, respectively.

Original languageEnglish
Pages (from-to)1168-1175
Number of pages8
JournalInternational Journal of Refrigeration
Issue number7
Publication statusPublished - 2007 Nov

Bibliographical note

Funding Information:
This research was supported by a grant (BA2-101-2-0-1) from the Carbon Dioxide Reduction & Sequestration Center, one of the 21st Century Frontier R&D Programs in the Ministry of Science and Technology of Korea.


  • Air conditioner
  • Air conditioning
  • Capillary tube
  • Coiled tube
  • Correlation
  • Expansion device
  • Experiment
  • Flow
  • Modelling

ASJC Scopus subject areas

  • Building and Construction
  • Mechanical Engineering


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