Environmental Engineering Reference
In-Depth Information
Ta b l e 4 . 7
The viscosity coefficient of gases in units of 10
5
g/(cm s) [31, 36].
T
, K
100
200
300
400
600
800
1000
H
2
4.21
6.81
8.96
10.8
14.2
17.3
20.1
He
9.77
15.4
19.6
23.8
31.4
38.2
44.5
CH
4
-
7.75
11.1
14.1
19.3
-
-
H
2
O
-
-
-
13.2
21.4
29.5
37.6
Ne
14.8
24.1
31.8
38.8
50.6
60.8
70.2
CO
-
12.7
17.7
21.8
28.6
34.3
39.2
N
2
6.88
12.9
17.8
22.0
29.1
34.9
40.0
Air
7.11
13.2
18.5
23.0
30.6
37.0
42.4
O
2
7.64
14.8
20.7
25.8
34.4
41.5
47.7
Ar
8.30
16.0
22.7
28.9
38.9
47.4
55.1
CO
2
-
9.4
14.9
19.4
27.3
33.8
39.5
Kr
-
-
25.6
33.1
45.7
54.7
64.6
Xe
-
-
23.3
30.8
43.6
54.7
64.6
particlesinagasisgivenby
s
T
μ
0.47
ND
σ
D
,
(4.63)
g
where
N
is the number density of gas atoms or molecules,
T
is the room gas tem-
perature, and
is the reduced mass of a test particle and a gas particle. The values
of the gas-kinetic cross sections
μ
g
on the basis of (4.63) and measured values of
the diffusion coefficients are given in Table 4.5.
The thermal conductivity coefficients are given in Table 4.6 for inert gases and
simple molecular gases at a pressure of 1 atm, and the viscosity coefficients at atmo-
spheric pressure are represented in Table 4.7 according to the corresponding mea-
surements. Note also the simple relation (4.57) within the framework of the first
Chapman-Enskog approximation between the thermal conductivity coefficient and
the viscosity coefficient.
σ
4.3
Transport of Electrons in Gases
4.3.1
Diffusion and Mobility of Electrons in Gases in Electric Field
Comparing the drift of electrons in gases in an external electric field with that of
neutral atomic particles in gases, we note that in contrast to neutral particles with a
Maxwell distribution function for velocities, the distribution function for electrons
