3.6 Air Speed Measurement
77
(continued)
N
A
B
C
D
7
3.4
3.7
4
–
8
3.4
3.7
4.1
–
D
–
–
–
4.7
Solution
N
A
B
C
D
0
–
–
–
4.5
1
3.4
3.5
4.1
–
2
3.5
3.6
4.2
–
3
3.3
3.6
4.3
–
4
3.4
3.8
4.2
–
5
3.4
3.7
4.1
–
6
3.4
3.6
4.2
–
7
3.4
3.7
4
–
8
3.4
3.7
4.1
–
D
–
–
–
4.7
n
i=1
v i
27.1
29.2
33.2
n
i=1 v i
n
3.4
3.65
4.18
4.6
Exact formula:
v m = 0.083 (4.6 + 0.313) (4.18 + 0.286) (3.65 + 0.282) 3.4 = 3.693
Approximate formula:
v m = 0.07 (4.6 + 0.3) (3.4 + 3.65 + 4.18) = 3.691
Simplified formula:
v m = 0.8 · 4.6 = 3.68
3.6.5 Smoke-Cloud Generator (Smoke Tube)
Smoke tubes are one of the devices traditionally used to measure slow air speeds
in mine galleries. They consist of a glass tube that can be broken at one end so