BLEVE and fireball models

Several integrated analysis packages contain BLEVE and fireball modeling. These include ... 

This section covers radiation due to BLEVEs with accompanying fireballs. First, a brief description is given of experimental investigations of BLEVEs and their fireballs. Next, some fireball models, primarily for predicting fireball diameter and combustion duration, are presented. Most of these models evolved from experimental results. Finally, some radiation models, based on experiments and theory, are given. 

The physical models described in Chapter 2 generate a variety of incident outcomes that arc caused by release of hazardous material or energy. Dispersion models (Section 2.3) estimate concentrations and/or doses of dispersed vapor vapor cloud explosions (VCE) (Section 3.1), physical c q)losion models (Section 3.3), fireball models (Section 3.4), and confined explosion models (Section 3.5) estimate shock wave overpressures and fragment velocities. Pool fire models (Section 3.6), jet fire models (Section 3.7), BLEVE models (Section 3.4) and flash fire models (Section 3.2) predict radiant flux. These models rely on the general principle that severity of outcome is a function of distance from the source of release. 

By using the Stoll and Chianta (1971) relation and their own BLEVE model, Lihou and Maund (1982) calculated a hazard range for severe bums to people (X) of 55 m for a BLEVE fireball of 1000 kg of propane, and of 255 m for 50,000 kg of propane. These distances can be approximated by... 

The fireball is assumed to be constant over this duration, although in reality some growth and decay may occur. Films taken of actual BLEVEs indicate that a fireball rises. This is not addressed in most models in other words, the fireball is assumed to be a sphere resting on the ground. 

The influence of such a two-step vessel failure on fireball formation appears to be significant. Some of the observations made here contradict earlier works bas on liquid superheat and the results from single-step failures and thus will be important in designing further experiments and developing realistic fireball and BLEVE models. 

Pitblado (1986) lists thirteen published correlations and compares BLEVE fireball diameters as a ftmetion of mass released. The TNO formula (Pietersen and Huerta, 1985) gives good overall fit to observed data, but there is substantial scatter in the source data. All models use a power law correlation to relate BLEVE diameter and duration to mass. Useful formulas for BLEVE physical parameters are (AIChE, 1994) ... 

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