Investigation of non-equilibrium effects during the depressurization of carbon dioxide

Predicting the phase change of liquid CO₂ during depressurization is highly relevant for the application in refrigeration units and for safety analysis in the context of CO₂ capture and storage (CCS). For abrupt depressurization processes, nucleation of gas will not occur at equilibrium and the liquid becomes superheated. In this work, we analyze the experimental results of depressurization tests conducted in the ECCSEL depressurization facility in Trondheim for pure CO₂ and determine the degree of superheat reached in the tests. The experiments include depressurization from 11-12 MPa to atmospheric pressure at different temperatures and the thermodynamic path in one of the cases passes near the critical point. The results agree well with the nucleation rate predicted by classical nucleation theory