98
4 Mine Ventilation Networks
f 4
f 12
=
(0.75 + 0.25 log 12)
2
(0.75 + 0.25 log 4)
2
=
1.04
0.81
f 4
f 12
= 1.28
Exercise 4.5 A test was carried out to determine the resistance to the passage of
air in a group of homothetic galleries, of equal coefficient of friction, supported by
yieldable steel arches with steel wire mesh and equipped with rails and pipes. Data
from these trials are shown in table:
Cross-sectional area, A (m 2 )
Atkinson’s hectometric resistance, R 100 (μ)
20
0.28
15
0.59
13
0.94
8
2.9
6
6
You are asked to:
(a) Estimate the value of the aerodynamic resistance for a hectometer of gallery of
10 m
2 of cross-sectional area.
(b) Estimate the value of the aerodynamic resistance for a hectometer of gallery of
1 m
2 of cross-sectional area.
(c) Comment on the extent to which these data conform to the theory exposed in
the chapter.
Solution
(a) The previous data can be represented in a Cartesian coordinate system offering
the exponential equation of the figure.
0
1
2
3
4
5
6
7
0
5
10
15
20
25
R
100
S (m 2 )