Karla Gonçalves ^1,2* Szabolcs Varga ² Dariusz Butrymowicz ³ Kamil Śmierciew ³

• ¹ Faculty of Engineering, University of Porto, Porto, Portugal
• ² Institute of Science and Innovation in Mechanical Engineering and Industrial Engineering, Faculty of Engineering, University of Porto, Porto, Portugal
• ³ Bialystok University of Technology, Bialystok, Podlaskie Voivodeship, Poland

This study focuses on assessing the Homogeneous Equilibrium Model's applicability to simulate a CO2 flashing ejector at a reduced pressure of 0.47. The model was implemented in FLUENT, integrating a user-defined real gas model. Simulation results with different boundary condition options were compared to experimental data. The analysis was carried out to evaluate the predictive capabilities of the model and assess the experimental data quality. The results indicate that the developed model accurately estimated the motive mass flow rate, with a maximum relative error of 5.7%, showing better performance than previously reported data. The entrained flow rate, assuming double choking operation, was significantly higher than the experimental measurement, and the CFD-predicted wall static pressure underestimated the experimental profile, suggesting singlechoked ejector operation. In contrast, the outflow density was better predicted under the same assumption, with an average error of 8.6%. Nevertheless, the simulated temperature profiles showed good agreement with the experimental data, especially when using the experimental entrained mass flow rate as a boundary condition. It was concluded that although the CFD simulations are highly valuable for predicting complex flow phenomena in flashing ejectors, additional research to generate high-quality experimental data for CO2 ejector model validation would be of great importance.