Experimental research and simulation of two-phase plume for R134a release and diffusion

The frequent occurrence of Liquefied natural gas (LNG) leakage accidents has caused serious economic loss and environmental damage. Therefore, it's of great significance to make assessments on the LNG hazards during its accidental release and associated consequences. This paper focuses on the two-phase release process in the liquefied gas release and dispersion accident and makes investigatatation on the two-phase plume with experimental and numerical approaches. A small-scale experimental system is developed with different sizes of release holes. With the experiment results, the mass outflow rate and temperature have been obtained, which provided initial parameters for the simulation. Jet velocities have been measured by PIV, and results reveal that an obvious velocity breach existing near the leakage nozzle due to the Joule-Thomson effect. Besides, given a point in the X-axis, the jet velocity is decreasing with an increasing diameter hole. Subsequently, the experimental data are utilized to verify the liquid-gas phase numerical model using Eulerian-Lagrange approach. Comparing with the results obtained by single gas phase model, the velocities obtained by liquid-gas phase model show good consistency with the experiments. Afterwards, the validated numerical liquid-gas phase model is employed to analyze the temperature distribution, concentration distribution and droplet size distribution in the near-source release region. With the simulation results, it depicts that there is a violent temperature decrease near the leakage nozzle in the liquid-gas phase model, which was caused by the evaporation of droplets. Meanwhile, concentration of R134a simulated by liquid-gas phase model is higher than the value of single-gas phase. These results emphasize that it’s essential to simulate the release accidents with liquid-gas phase model, especially in the near-source region. Both the experiments and numerical models are of great value for providing assessments and theoretical supports for the risk consequences in the process safety.