Work

A numerical simulation method for CO2 leakage considering non-equilibrium phase transition

Year: 2025

Type: article

Abstract: CO2 has strong compressibility and complex phase change characteristics. Once a leakage occurs, it will undergo rapid expansion and intricate phase-transition, causing a compound pressure drop process including a pressure plateau. Maintaining high pressure plateau at outlet provides energy for the propagation of ductile cracks. While throttling and phase exchange cause a continuous decrease in temperature, which may lead to brittle fracture of the pipeline. Therefore, it is quite necessary to establish a numerical simulation method that can accurately predict the characteristics of CO2 leakage. In this work, SW state equation is utilized to calculate the property of CO2. The Mixture and Lee model are brought together to calculate the non-equilibrium phase transition characteristics. A numerical simulation method applicable to all phase states of CO2 depressurization is established, and experimental data of CO2 depressurization in gas, liquid, and supercritical phase are chosen for model validation. The results note that this method can successfully simulate the pressure drop and temperature drop laws during the non-equilibrium phase transition depressurization process of all phase CO2 leaks. For the pressure drop and temperature drop simulation, result of gas CO2 agree well with experimental data. However, a shortened overall depressurization time compared with experiment of the liquid and supercritical CO2 is predicted in the third stage of depressurization. The limit boundaries of the depressurization path and decompression wave are obtained through phase equilibrium and single-phase isentropic depressurization calculations, further explaining the non-equilibrium effect in CO2 leakage depressurization process.

Source: Journal of Pipeline Science and Engineering

DOI: 10.1016/j.jpse.2025.100402