Solutions of supercritical CO2 flow through a convergent-divergent nozzle with real gas effects

• Published in: International journal of heat and mass transfer Vol. 116; pp. 127 - 135
• Main Authors: Raman, S.K., Kim, H.D.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.01.2018; Elsevier BV
• Subjects: Carbon dioxide; Compressibility; Compressible flow; Compressors; Convergent-divergent nozzles; Equation of state; Equations of state; Flow characteristics; Flow resistance; Gas dynamics; Gases; Machinery and equipment; Pressure loss; Real gas effect; Shock wave; Shock waves; Supercritical carbon dioxide; Thermal conductivity; Thermodynamic properties; Thermophysical properties; Turbines; Viscosity; Working fluids; Supercritical carbon dioxide; Real gas effect; Shock wave; Compressible flow; Equation of state
• ISSN: 0017-9310; 1879-2189
• DOI: 10.1016/j.ijheatmasstransfer.2017.09.019

•S-CO2 flow through nozzle is theoretically analyzed with six different EOSs.•The flow properties predicted with real gas EOS is compared with ideal gas EOS.•The flow field inside the shock wave is also analyzed with real gas effects.•The influence of thermodynamic models choice in the S-CO2 flow modeling is analyzed. Supercritical CO2 (S-CO2) has a density as high as that of its liquid phase while the viscosity remains closer to its gaseous phase. S-CO2 has the potential to be used as a working fluid in compressor as it requires much less work due to its low compressibility as well as relatively small flow resistance. Besides the material properties and design calculations, the thermodynamic properties of working gases play a vital role in the design and efficiency of various machinery such as compressors, turbines, etc. Equation of state (EOS) which accounts the real gas effects is used in computational analysis to estimates the thermodynamic properties of the working fluid. Each EOS gives priority to real gas effects phenomena differently and for the analysis of the fluid dynamic machinery, as of today, there is no standard procedure for selecting a suitable equation of state (EOS). To understand the influence of real gas effects on the formation of a shock wave, S-CO2 flow through a convergent-divergent nozzle, is theoretically analyzed. The thermophysical and transport properties calculated with the six different equation of state (EOS) are used to estimate the flow characteristics. An in-house code based on the real gas approach which solves gas dynamics equations with variable gas properties is used to analytically analyze the compressible flow of S-CO2 through nozzle. The solution for the shock strength, total pressure loss, and location of the normal shock wave at different back pressure conditions is obtained. Using Becker’s solutions with varying viscosity and thermal conductivity estimated from each EOS, the properties inside the normal shock wave are calculated. Numerical results of supersonic S-CO2 flow varies with different EOS candidates and the formation of shock wave is found to be significantly influenced by the real gas effects.