Flow of refrigerant 134a through orifice tubes

G. M. Singh, P. S. Hrnjak, C. W. Bullard

Research output: Contribution to journalArticlepeer-review


In this paper, experimental data and a model for predicting refrigerant flow through orifice tubes used as expansion devices in automotive and other air conditioning systems are presented. The results are analyzed for an extensive set (933 data points) of measurements of mass flow rate of 1,1,1,2,-tetrafluoroethane (CH2FCF3, better known as refrigerant R-134a) through orifice tubes of different diameters and lengths, with and without inlet and outlet screens, over a wide range of operating conditions, and in the range of inlet qualities from 0 to 1 and subcooling up to 40°C. The mass flow rate through orifice tubes was found to be a strong function of inlet pressure, inlet subcooling, and diameter, but a relatively weak function of length. The semi-empirical model is developed using the data set and is applicable over the complete range of operating conditions covering transients and very high vapor quality inlets that are common in automotive air conditioning applications.

Original languageEnglish (US)
Pages (from-to)245-262
Number of pages18
JournalHVAC and R Research
Issue number3
StatePublished - Jul 2001

ASJC Scopus subject areas

  • Building and Construction


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