Hazards of LNG Releases - an Efficient Numerical Modeling Technique

Abstract

In previous work [1], a two-phase Smoothed Particle Hydrodynamics (SPH) model was developed for the simulation of the release and spreading of LNG over complex terrain. Compared to traditional multiphase CFD methods, the meshless SPH approach has several advantages, such as (i) excellent mass conservation, especially when modeling small-scale features of moving and deforming fluid interfaces (e.g. thin films or small vapor bubbles); (ii) efficient tracking of complex interface deformation and movement; and (iii) effective dealing with complex flow boundaries. As a result, the SPH method is found to be suitable for simulating LNG loss of containment events where the details of the release and spreading events.

In this work, the SPH model is further developed to include a more advanced treatment of the near-boundary vaporization. With conjugate heat transfer between the LNG and the solid substrate taken into consideration, the heat flux going into LNG heating and phase change is determined based on the assumption of film boiling heat transfer domination. The near-boundary vaporization model is tested in simulations of boiling with single bubble growth on horizontal and vertical heating surfaces.

The dispersion and the possible combustion of vaporized LNG are important issues in the LNG release hazard analysis. The mixing and transport of LNG vapor with air, however, are better described by traditional multiphase CFD models. The above-mentioned SPH model of LNG spreading is proposed to be coupled with the CFD solver OpenFOAM using LIGGGHTS CFD-Coupling [2]. A limited testing of the coupled SPH-OpenFOAM model for a realistic large scale LNG release scenario is conducted and discussed.

Reference:

[1] Bui, A., Reed, M., Liu, T., and Peterson, E., “Modelling of LNG Spreading and Vaporization Using Smoothed Particle Hydrodynamics Method”, Proceedings of the 12^th AIChE GCPS, Houston, Texas, April, 2016.

[2] www.cfdem.com