Environmental Engineering Reference
In-Depth Information
The gas-kinetic cross section as the collision parameter of atoms or molecules
at room temperature is defined on the basis of (4.59) for the diffusion coefficient
within the framework of the hard-sphere model, and the measured values of the
diffusion coefficient are used in this formula. Correspondingly, the connection be-
tween the gas-kinetic cross section
σ
g
and the diffusion coefficient
D
of atomic
Ta b l e 4 . 5
Gas-kinetic cross sections
σ
g
expressed in units of 10
15
cm
2
[34].
Colliding particles
He
Ne
Ar
Kr
Xe
H
2
N
2
O
2
CO
CO
2
He
1.3
1.5
2.1
2.4
2.7
1.7
2.3
2.2
2.2
2.7
Ne
1.8
2.6
3.0
3.3
2.0
2.4
2.5
2.7
3.1
Ar
3.7
4.2
5.0
2.7
3.8
3.9
4.0
4.4
Kr
4.8
5.7
3.2
4.4
4.3
4.4
4.9
Xe
6.8
3.7
5.0
5.2
5.0
6.1
H
2
2.0
2.8
2.7
2.9
3.4
N
2
3.9
3.8
3.7
4.9
O
2
3.8
3.7
4.4
CO
4.0
4.9
CO
2
7.5
Ta b l e 4 . 6
The thermal conductivity coefficient
of gases at atmospheric pressure in units of
10
4
W/(cm K) [35].
T
, K
100
200
300
400
600
800
1000
H
2
6.7
13.1
18.3
22.6
30.5
37.8
44.8
He
7.2
11.5
15.1
18.4
25.0
30.4
35.4
CH
4
-
2.17
3.41
4.88
8.22
-
-
NH
3
-
1.53
2.47
6.70
6.70
-
-
H
2
O
-
-
-
2.63
4.59
7.03
9.74
Ne
2.23
3.67
4.89
6.01
7.97
9.71
11.3
CO
0.84
1.72
2.49
3.16
4.40
5.54
6.61
N
2
0.96
1.83
2.59
3.27
4.46
5.48
6.47
Air
0.95
1.83
2.62
3.28
4.69
5.73
6.67
O
2
0.92
1.83
2.66
3.30
4.73
5.89
7.10
Ar
0.66
1.26
1.77
2.22
3.07
3.74
4.36
CO
2
-
0.94
1.66
2.43
4.07
5.51
6.82
Kr
-
0.65
1.00
1.26
1.75
2.21
2.62
Xe
-
0.39
0.58
0.74
1.05
1.35
1.64
