A non-equilibrium phase transition computational fluid dynamics (CFD) model for liquid CO₂ decompression with higher prediction accuracy is presented. In this model, Span-Wagner equation of state (EoS) is applied and compiled, the slip velocity between phases is considered, and the interphase mass transfer is controlled by introducing relaxation time coefficients. For validation, the numerical results are compared with the “shock tube” test results, showing good agreement. On this basis, the transient behaviour of the high-pressure liquid CO₂ pipelines during decompression is investigated, and the influences of initial state parameters (density and temperature) on the transient behaviour are further studied. It is found that the pressure change amplitude, the pressure change rate, the temperature change amplitude and the temperature change rate, as well as the outlet massflow increase with an increase in initial density and temperature. The durations of the sudden drop process of pressure and temperature are about 100 microseconds (μs). The degree of superheat of liquid CO₂ decreases with an increase in initial density during decompression. Besides, the pressure plateau value has a negative linear correlation with the initial density, while a positive linear correlation with the initial temperature.

提出了一种具有较高预测精度的液态CO ₂减压非平衡相变计算流体力学模型。在该模型中，应用并编译了Span-Wagner状态方程（EoS），考虑了相之间的滑移速度，并通过引入弛豫时间系数来控制相间传质。为了进行验证，将数值结果与“冲击管”测试结果进行了比较，显示出很好的一致性。在此基础上，高压液体CO ₂的瞬态行为研究了减压过程中的管线，并研究了初始状态参数（密度和温度）对瞬态行为的影响。发现随着初始密度和温度的增加，压力变化幅度，压力变化率，温度变化幅度和温度变化率以及出口质量流量增加。压力和温度突然下降过程的持续时间约为100微秒（μs）。减压时，液态CO ₂的过热度随着初始密度的增加而降低。此外，压力平稳值与初始密度呈负线性关系，而与初始温度呈正线性关系。