Numerical method for simulating high pressure CO₂ flows with nonequilibrium condensation

A numerical method for compressible flows withnonequilibrium condensation is reconstructed for simulatingsupercritical CO₂ flows with nonequilibrium condensationunder high pressure conditions. Thermophysical propertiesare interpolated from pressure-temperature look-up tables anddensity-internal energy look-up tables, which are generatedusing the polynomial equations in REFPROP. We employ thehigh pressure nonequilibrium condensation model in which thecritical radius of a liquid droplet is modified by consideringnon-ideal gas. We simulate high pressure CO₂ flows through aLaval nozzle, which was experimentally investigated byLettieri et al. High-pressure CO₂ passes through the nozzle,leading to a decrease in its pressure and temperature. It reachesthe supercooled condition near the throat. Nucleation and thesubsequent growth of droplets lead to an increase in thecondensate mass fraction in the diverging area. The proposedmethod for real gas reproduced the peak of pressuredistribution owing to the release of latent heat, whereas thenumerical result assuming ideal gas is different from theexperimental result. The nucleation region obtained using thepresent method is earlier and narrower than that in the case ofideal gas. The early and rapid nucleation leads to the high masscondensate rate at the outlet. These results show thatconsidering the real gas effect and nonequilibriumcondensation is crucial for developing the impeller of acompressor for the supercritical CO₂ Brayton cycle.