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Revisiting the mixing chamber velocity coefficient in two-phase ejectors: A physically interpretable approach.

Author(s) : SMIERCIEW K., GAGAN J., LUKASZUK M., DUDAR A., ZOU H., YANG T., BUTRYMOWICZ D.

Type of article: IJR article

Summary

The mixing chamber velocity coefficient φ in two-phase ejectors is commonly treated either as a constant or as a parameter obtained through empirical data fitting. While such approaches are widely accepted, they provide limited physical insight and weak transferability across geometries and operating conditions. This study demonstrates that φ is not a fixed quantity but a function of local two-phase flow physics. Based on an extensive experimental dataset for R290, three mixing chamber geometries were analyzed: convergent, cylindrical, and reamed convergent. A physically grounded definition of φ is introduced, based on a direct comparison between actual and isentropic outlet velocities. Instead of empirical tuning, the coefficient is correlated with dimensionless groups representing specific physical mechanisms: relative Weber number, slip ratio, momentum flux ratio, entrainment ratio, and normalized nozzle exit position. The correlation developed for the convergent geometry shows high agreement with experimental data (R2 = 0.983). When applied to different geometries, the functional dependence of φ is preserved, confirming that the selected dimensionless parameters capture the governing physical mechanisms. A systematic change in magnitude is observed, directly linked to geometric parameters. A geometry-dependent scaling factor restores high agreement with experimental data (R2 up to 0.98), demonstrating that geometry affects the magnitude of φ without altering its functional behavior. The results provide a physically interpretable and transferable framework for describing two-phase ejector mixing.

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Details

  • Original title: Revisiting the mixing chamber velocity coefficient in two-phase ejectors: A physically interpretable approach.
  • Record ID : 30035290
  • Languages: English
  • Subject: Technology
  • Source: International Journal of Refrigeration - Revue Internationale du Froid - vol. 189
  • Publication date: 2026/09
  • DOI: http://dx.doi.org/https://doi.org/10.1016/j.ijrefrig.2026.106996

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