Technical documentation and software quality assurance for project ...

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where
F = 3.6233⋅10 −5 m ˙
Pc = 3.6713 ˙ m
T j =
2
do 2
do 2Ts 2
2 + ( γ g −1)M
j
T c = 2T s
1+ γ g
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T c
γ g W gk
T s
γ g W gk
These formulas need to be modified slightly for the pipeline flare and two-phase release
scenarios. ALOHA assumes that the gas expands adiabatically in the last 200 pipe
diameters in the pipeline release. It exits at atmospheric pressure and therefore the
effective source diameter, Ds for the choked option reduces to that for the unchoked
option given earlier. For two-phase, ALOHA uses a modification of the formula in Cook
et al. (1990)
D s = d j
ρ jρ v
ρ a
where ρ is the pure vapor density. The modification of the Cook formula was necessary
v
to insure that it would reduce to the proper algorithm when the two-phase case reduced to
the pure gas scenario.
For a tilted jet, Kalghatgi (1983) showed in laboratory experiments that the flame
€ length reduces as the jet is tilted into the wind. Chamberlain (1987) uses Kalghatgi’s
empirical fit equation to determine the flame length, LB. Extending from the center of
the hole to the flame time, LB, is calculated
[ ( ) ]
L B =105.4D s 1− 6.07⋅10 −3 θ j − 90
and the flame length € in still air, LBO,
LBo =
[ 0.51exp( −0.4v)
€ + 0.49]
1− 6.07 ⋅10 −3 θ j − 90
( ) =
ξ L Bo
⎡
⎢
⎣
g
2 2
Ds u j
1
3
⎤
⎥ ⋅ LBo ⎦
L B
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[ ( ) ]
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