Technical documentation and software quality assurance for project ...

J. Zeeuwen and B.J. Wiekema (1978)The measurement of relative reactivities of
combustible gases, Conf. on the Mechanisms of Explosions in Dispersed Energetic
Materials.
FLARE (Jet Fire)
Summary:
Model calculates the size and shape of a flare or jet for gaseous releases from pipelines, tanks and twophase
releases from tanks. Chamberlain (1987) empirical formulas for vertical and inclined burns in a
horizontal wind are used to describe the geometry of the flame.
MODEL ASSUMPTIONS
• Gas releases from pipe or tank
• Choked and unchoked flow
• Two-phase flow from tank
• Flame assumed from open pipe rather than flare tip
• Burning gas is assumed to behave similar to a hydrocarbon (methane, propane and
ethylene).
• Visible flame described by a frustum of a cone
MODEL INPUTS
• inside diameter of the pipe or orifice (meter)
• average wind speed (meter per second)
• density of air
MODEL DESCRIPTION
Figure 6 shows the flow diagram for the flare. An in-depth description of the model is
reported in Chamberlain (1987) and Lee (2001). Chamberlain’s model was selected over
the alternative point source model since the latter is known to be insufficient within one
to two flame lengths for short-term radiation levels although sufficiently accurate in the
far field (Chamberlain, 1987). The Chamberlain better mimics the actual size and shape
of a flare.
A review of the literature in SFPE (1995) and Lee (2001) identified two versions
of the model, Kalghatgi (1983) and Chamberlain (1987), both of which approximated the
geometry of a flare as a frustum of a cone. While Kalghatgi’s used small burners in a
wind tunnel, the main focus of Chamberlain’s work was on field trials at onshore oil and
gas production installations. Both models used empirically fit equations to describe the
flame shape. In fact, Chamberlain uses Kalghatgi (1983) empirical equation to derive the
flame length. Because Chamberlain’s work was more recent and involved larger scale
testing, the Chamberlain model was selected for ALOHA to describe thermal radiation
hazards for both flares and jets.
From Chamberlain (1987), the gas velocity of the expanded jet, u j , is
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