This work presents a novel framework for numerically simulating the depressurization of tanks and pipelines containing carbon dioxide (CO2). The framework focuses on efficient solution strategies for the coupled system of fluid flow equations and thermodynamic constraints. A key contribution lies in proposing a new set of equations for phase equilibrium calculations which simplifies the traditional vapor-liquid equilibrium (VLE) calculations for two-phase CO2 mixtures. The first major novelty resides in the reduction of the conventional four-equation VLE system to a single equation, enabling efficient solution using a non-linear solver. This significantly reduces computational cost compared to traditional methods. Furthermore, a second novelty is introduced by deriving an ordinary differential equation (ODE) directly from the UV-Flash equation. This ODE can be integrated alongside the governing fluid flow equations, offering a computationally efficient approach for simulating depressurization processes.

翻译：本研究提出了一种用于数值模拟含有二氧化碳（CO2）的储罐和管道降压过程的新框架。该框架重点关注流体流动方程与热力学约束耦合系统的高效求解策略。一个关键贡献在于提出了一套用于相平衡计算的新方程，该方程简化了传统两相CO2混合物的气液平衡（VLE）计算。第一个主要创新点在于将传统的四方程VLE系统简化为单一方程，从而能够使用非线性求解器进行高效求解。与传统方法相比，这显著降低了计算成本。此外，第二个创新点是通过直接从UV-Flash方程推导出一个常微分方程（ODE）。该ODE可以与主导的流体流动方程联立积分，为模拟降压过程提供了一种计算高效的方法。