Study on supercritical CO2 critical flow through orifices under power cycle operating conditions

Abstract

For prediction of critical flow occurring under supercritical carbon dioxide (S-CO2) condition, one-dimensional (1-D) analytical critical flow models are evaluated in this study. Specifically, homogeneous equilibrium model (HEM) and a newly proposed non-equilibrium model are evaluated. The new non-equilibrium model adopts Moody's slip ratio for mechanical non-equilibrium and a newly proposed correlation of supercooling for thermal non-equilibrium. For evaluation of the models over various thermodynamic states, S-CO2 critical flow experi-ment through an orifice is conducted to supplement and expand a range of previously published S-CO2 critical flow experiment data. From the evaluation results with the expanded S-CO2 critical flow experiment database, the new non-equilibrium model shows better prediction performance than HEM in terms of the prediction of critical mass flux and critical pressure. For practical applications, discharge coefficients for each 1-D analytical critical flow model are suggested for the orifice geometry.