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Optimization of two-phase expansion nozzles: An exergy based analysis of fluid property influence.

Author(s) : SAUGNAC R., SAMPEDRO E. O., BOUALLOU C.

Type of article: IJR article

Summary

Two-phase expansion energy-recovery systems, such as ejectors and two-phase turbines, can substantially improve the efficiency of air conditioning, heating, liquefaction or power generation thermodynamic processes. One of their key component is the stator, or nozzle, that converts fluid enthalpy into kinetic energy. The choice of fluid depends on considerations such as cycle efficiency. However, estimating the efficiency of two-phase expansion is not trivial and can be highly dependent on the working fluid. This paper analyses the effects of the geometric design and fluid properties on the efficiency of two-phase nozzles. The aim is to identify trends in the properties that most significantly affect performance so the fluid hydrodynamic properties are included in the selection process. To this end, a tool for the optimal 1D bi-fluid design of the nozzle is developed, followed by a exergy analysis to determine the thermophysical properties responsible for the losses. The optimization tool is based on an Euler-Euler flow solver with advanced closure terms and a genetic algorithm profile optimizer. The calibration of the physical model is based on experimental data from the literature on R744, R290 and R134a fluids used in commercial refrigeration operating conditions. Optimization and exergetic analysis are performed for similar conditions. A nozzle per fluid was designed. The results show an increase in nozzle efficiency of around 10 % associated with the optimization. Once the nozzles are optimized, comparative exergy analysis indicates that the key parameters affecting losses are liquid density, liquid-vapour density ratio and liquid heat capacity to characteristic length ratio.

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Pages: 17 p.

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Details

  • Original title: Optimization of two-phase expansion nozzles: An exergy based analysis of fluid property influence.
  • Record ID : 30034368
  • Languages: English
  • Subject: Technology
  • Source: International Journal of Refrigeration - Revue Internationale du Froid - vol. 179
  • Publication date: 2025/11
  • DOI: http://dx.doi.org/https://doi.org/10.1016/j.ijrefrig.2025.07.028

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