Analysis of transcritical CO2 vortex tube performance using a real gas thermodynamic model

• Published in: International journal of thermal sciences 2022-07, Vol.177, Article 107555
• Main Authors: Mansour, Ahmed, Lagrandeur, Junior, Poncet, Sébastien
• Format: Article
• Language: English
• Subjects: Carbon dioxide; Exergy efficiency; Real gas; Transcritical conditions; Vortex tube
• ISSN: 1290-0729; 1778-4166
• DOI: 10.1016/j.ijthermalsci.2022.107555

A new real gas model is developed to estimate the cold and hot exit temperatures of a vortex tube. The effect of the Bödewadt boundary layer flow is taken into account in addition to the introduction of a correction factor to account for high cold mass fractions. The model results are validated against an ideal gas model and with experimental data available in the literature for three different working fluids, namely air, R134a and carbon dioxide. The model exhibits similar results compared to the ideal gas model for air while it substantially enhances the predictions of the cold and hot exit temperatures for R134a and carbon dioxide. In addition, a parametric study is performed to test the operation of carbon dioxide under transcritical conditions. Working under transcritical conditions, liquid droplets form after the inlet gas expansion. In effect, the hot exit temperature decreases significantly below the inlet temperature. However, the cooling and heating powers can get significantly higher up to a 1 kW compared to only 90 W under subcritical conditions. Also, the exergy efficiency increases notably by at least 88.5%. •A new thermodynamic model for vortex tubes working with real gases is developed.•The model is carefully validated against experimental data for air, R134a and CO2.•A parametric study is achieved under subcritical and transcritical conditions for CO2.•The maximum exergy efficiency can reach 52% under transcritical conditions.•The results point out the key role of the separation efficiency of the liquid.