Experimental study on transient characteristics and thermal stratification of high−pressure CO2 leakage under different initial density

Accidental leakage is one of the major safety issues in the carbon capture and storage project (CCS), which may pose a significant danger to pipelines, containers and surrounding crowd. It is necessary to study the leakage behavior of high−pressure CO₂, providing data support for the risk assessment of CO₂ leakage. In this paper, the accidental leakage of high−pressure CO₂ is simulated by releasing CO₂ from a storage tank, aiming to understand the transient characteristics and thermal stratification inside the tank of CO₂ leakage process. The initial CO₂ is at different initial density of 600∼1000 kg/m³ and at almost the same initial pressure of 10.8 ± 0.4 MPa. Firstly, the outlet transient characteristics and temperature evolution inside the tank are presented. Then, the variation of P−T curves and phase evolution are analyzed in detail. Finally, the leakage behavior under different initial density is described. The results show that the leakage process can be clearly divided into three stages based on the outlet pressure. The outlet pressure evolution, phase evolution and temperature distribution inside the tank are very different in these three stages. This research is of great significance for leakage risk prediction, early leakage detection and leakage hazard control.