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A new model of mass flow characteristics in electronic expansion valves considering metastability.

Author(s) : CHEN L., LIU J., CHEN J., et al.

Type of article: Article

Summary

This paper presents an experimental study on the mass flow characteristics of electronic expansion valves in a wide operating condition range. It was found that flow choking always occurs under common operating conditions in refrigeration systems. Based on metastability in EEVs, a new model predicting mass flow rate was proposed under flow choking conditions. Different from the conventional models using Bernoulli equation which employed downstream pressure at the EEV exit and a corrected mass flow coefficient, the present model considered metastable liquid flow caused by rapid depressurization, and employed single-phase incompressible flow coefficient and metastable pressure at the throat. An empirical correlation of the metastable pressure, based on the experimental data for R-22 and its substitutes, R-407C and R-410A, was developed in a power law form of dimensionless parameters including upstream operating parameters and refrigerant thermophysical properties and throat area. The predictions of the present model were found to be in good agreement with the measured data, and approximately 95% of the measured data fall within a relative deviation of ±7.0%. The comparison with a prior model shows that, in terms of flashing mechanism application and predicting accuracy, the present model is better than the conventional model without considering metastability. [Reprinted with permission from Elsevier. Copyright, 2008].

Details

  • Original title: A new model of mass flow characteristics in electronic expansion valves considering metastability.
  • Record ID : 2009-1092
  • Languages: English
  • Source: International Journal of thermal Sciences - vol. 48 - n. 6
  • Publication date: 2009/06

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