Modeling of the two-phase flow during depressurization of liquified CO2 in a pipe

Abstract

Modeling transient CO₂ two-phase flow in a pipe is essential in studying depressurization mechanisms resulting from liquified CO₂ accidental release. Generated data from such models predict the released flow characteristics and possible propagating fractures. Accordingly, they provide valuable input for risk prevention in designing and safely operating CO₂ transport pipelines. CO₂ depressurization simulation involves fluid-mechanical and thermodynamic models, primarily expressed by hyperbolic partial differential equations and an equation of state (EOS). Besides, these models are solved with appropriate numerical methods. This paper deals with a drift flux - homogeneous equilibrium model (HEM) construction utilizing central-upwind-weighted essentially non-oscillatory (WENO) numerical schemes to describe two-phase flow during CO₂ decompression in a pipe. Rapid transition in mass, momentum, and energy at the interface between liquid and vapor phases is assumed in the flow HEM. Thus, the two-phase flow is in a thermal, mechanical, and chemical equilibrium. The thermodynamic properties are calculated by applying Span-Wagner EOS. The high-resolution second-order central, central-upwind, and third-order weighted essentially non-oscillatory (WENO) schemes have been executed with the HEM, and they effectively captured rapid phase transition. The central-upwind and essentially non-oscillatory (ENO) schemes' stencils can be appropriate for constructing a higher-order accuracy central-upwind-WENO scheme. This structured scheme uses a smoothness indicator as an alternative to the limiter function. Besides, the variables in the cell interface are determined by WENO reconstruction, while central-upwind is used to compute the flux properties.