Environmental Engineering Reference
In-Depth Information
Table 3.11 Average
molecular thermal capacity
parameters
Atomic state
Thermal capacity parameter
Two-atom gas
10
4
t
C
v
¼
4
:
8
þ
4
:
5
Water vapor
10
4
t
C
v
¼
4
:
0
þ
21
:
5
Three-atom gas
C
v
¼
9
:
0
þ
5
:
7
10
4
t
Four-atom gas
C
v
¼
a
þ
bt
Five-atom gas
10
4
t
C
v
¼
12
þ
4
:
5
Carbon
C
v
¼
6
:
0
Salt
C
v
¼
28
:
3
Aluminum oxide
C
v
¼
23
:
86
þ
67
:
3
10
4
t
Now, with TNT as an example, the explosion temperature is calculated, and
TNT explosion reaction equation is,
C
6
H
2
NO
ð
2
CH
3
!
2CO
2
þ
CO
þ
4C
þ
H
2
O
þ
1
:
2H
2
þ
1
:
4N
2
þ
0
:
2NH
3
þ
1113
:
28 kJ
=
mol
The thermal capac
ity
of TNT explosion products is the following:
In two at
omi
c gas, C
v
¼
ð
1
þ
1
:
2
þ
1
:
4
Þ
ð
4
:
8
0
:
00045 t
Þ ¼
17
:
28
þ
0
:
00162 t;
In water
, C
v
¼
1
ð
4
:
0
þ
0
:
00215 t
Þ ¼
4
:
0
þ
0
:
00215 t;
In CO
2
,
C
v
¼
2
ð
9
:
0
þ
0
:
00058 t
Þ ¼
18
:
0
þ
0
:
00116 t;
In NH
3
,
C
v
¼
0
:
2
ð
10
:
0
þ
0
:
00045 t
Þ ¼
2
:
0
þ
0
:
00009 t;
In C, C
v
¼
24.
Thermal capacity of all explosive products,
P
C
v
t
¼
65
:
28
þ
0
:
00502t
So, a = 65.28 and b = 0.00502 are introduced into Eq.
3.26
, then,
4
6
¼
p
65
t
¼
:
:
28
2
þ
:
:
65
28
4
0
00502
266
08
1000
260
C
¼
3
;
2
0
:
00502
or
T
¼
;
þ
¼
;
3
260
273
3
533 K
From the average molecular thermal capacity parameters, the calculated value is
slightly low, thus the calculated explosion temperature t are slightly large.
B. Explosion product internal energy method
Internal energy of explosion product ingredients is another method to calculate
the explosion temperature. The change of internal energy of explosion product with
temperature has been calculated accurately as shown in Table
3.12
.
In the explosion, Eq.
3.7
is believed to be a constant-volume process, i.e.,
dV = 0, while all of the released heat are used in the internal energy transition of
explosion products, namely,
D
E
¼
Q
v
. Therefore, with energy data of explosion
product change in Table
3.12
, explosion temperature can be calculated.
