(222e) A Non-Equilibrium Model for Bleve Simulation

Boiling liquid expanding vapor explosion (BLEVE) occurs when there is a sudden loss of containment of a pressure vessel containing a superheated liquid or a liquefied gas. The resulting thermal radiation is intense and has the potential to cause severe health-damage even loss of life as well as other material damage.

When a liquefied gas vessel is depressurized rapidly, it becomes highly superheated. Consequently, a great deal of bubbles generated homogeneously in the bulk liquid, and the liquid vaporize violently. The higher the superheat, the larger the number of bubbles generated. Consequently, the pressure will increase dramatically, sometimes even surpass the initial pressure in the vessel, causing further destruction.

A new non-equilibrium model is suggested to simulate this BLEVE process. Firstly, a new hypothesis for predicting homogeneous nucleation rate in superheated liquids is proposed according to the probability distribution of energy fluctuation in statistical thermodynamic fluctuation theory. Then, the pressure decrease and re-increase process is simulated by combining a bubble growth and collapse model based upon non-equilibrium thermodynamic theory and a model for the dynamic process of vapor space.

A case study is given to illuminate the dynamic processes of pressure, temperature, mass, liquid level, outlet velocity, evaporating heat as well as homogeneous nucleation rate during release of the LPG tank. The influences of initial temperature (initial pressure), crack diameter, initial liquid level, tank volume and percent of propane in LPG on the LPG vapor explosion thermal processes are then discussed.