Chemistry Reference
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(the point at which the heat emission curve crosses the heat evolution curve be-
low the inflection point) are similar to the characteristics of the process that occurs
without volumetric evaporation (in the latter case the stationary heating is slightly
higher). The behavior of the liquid under conditions corresponding to the region
above the explosion initiation limit is of particular interest.
It is known that the temperature of the nonevaporating substance in the region
above the explosion initiation limit grows rapidly (after an induction period) during
thermal explosion, up to quite high values close to the adiabatic combustion (ex-
plosion) temperature. The behavior of a volatile liquid explosive is completely dif-
ferent. If the heat emission conditions correspond to the region above the explosion
initiation limit (Fig. 10.2, line 3), a new stationary mode of the process occurs due to
the specific character of the heat evolution function. This mode is characterized by
a high warm-up
T
st
=
T
st
-
T
0
, which significantly exceeds the maximum warm-up
(R
T
0
cr
/
E
) determined via the classical Semenov theory for gases and nonvolatile
condensed systems.
In this case, the temperature of the liquid,
T
st
, is determined by a combination of
kinetic constants, volumetric evaporation parameters and heat-transfer characteris-
tics, and can be found by computationally solving (10.9). The upper limit of the tem-
perature of the liquid is
T
ad
, which corresponds to the adiabatic process
Δ
S
/
V
= 0
(Fig. 10.1). By placing the term in square brackets in expression (10.1) equal to zero
and introducing the theoretical liquid boiling point,
T
b
, determined from
P
∞
=
P
0
exp
α
,
L
R
T
b
−
one obtains
R
T
b
L
ln(1 +
Lb
/
Qa
)
1 +(R
T
b
/
L
) ln(1 +
Lb
/
Qa
)
.
T
ad
=
T
b
−
(10.10)
Taking into account that, as a rule,
ln
1 +
Lb
Qa
<<
1
,
R
T
b
L
then expression (10.10) can be simplified to
R
T
b
L
ln(1 +
Lb
T
ad
=
T
k
−
Qa
)
.
(10.11)
One can see from Eqs. (10.10) and (10.11) and Fig. 10.1 that
T
ad
increases as the
ambient pressure increases and always remains below the boiling point.
At
T
st
the process occurs vigorously and is characterized by significant heat evo-
lution, resulting in active vapor formation. In experimental studies this process is
interpreted as a flash. The flash can be accompanied by a bright glow in the case
of self-inflammation of the vapor-gas mixture or it can occur as a flameless pro-
cess. Since it is a matter of special interest, the analysis of the critical conditions
for vapor-gas mixture self-inflammation is not considered here. In experiments on
