Numerical investigation on the multiphase jet dispersion and sublimation cooling characteristics during accidental release of liquid CO2

Abstract

The increasing deployment of liquid CO₂ projects requires a deep understanding of the jet dispersion and sublimation cooling characteristics during accidental pipeline release of liquid CO₂ from a career to accurately assess the hazards caused to nearby targets. In this study, a pipe flow model was established considering the flashing delay phenomenon and a source model was built to handle the phase transition from vapour-liquid to vapour-solid near the nozzle outlet. These two models were combined to quickly predict the pseudo source parameters, which can be used as the inlet boundary conditions for the computational fluid dynamics (CFD) model to simulate the jet dispersion of liquid CO₂. The effects of pipe inlet pressure, vapour mass fraction, nozzle size, pipe length, pipe diameter, pipe roughness and ambient temperature on CO₂ concentration, plume temperature, plume velocity, mass flow rate of dry ice and dry ice survival distance were analyzed. The results show that the prediction errors of the mass flow rate using the pipe flow model and source model were almost lower than 20 %. The temperature, velocity and CO₂ concentration predicted by the CFD model agree well with the experimental results. The assumption size distribution (1 ∼ 30 μm) of dry ice, described by the Rosin-Rammler model, can well capture the significant temperature drop near the release point. Moreover, an assessment process was proposed to design and optimize the release pipeline of liquid CO₂ to meet some standard requirements.