94
4 Mine Ventilation Networks
R =
Q 2 =
1
lbf
ft
2
1000
ft
3
s
2 =
1
lbf
ft
2
1000 2 ft
6
s 2
=
1 lbf s
2
1000 2 ft
8
In this case, the conversion to the SI would be:
One historical unit, still of some use, is the murgue (μ). This is defined as: “Resistance of a airway which causes a pressure loss
6 of 1 gf m
−2 when traversed by an
airflow rate of 1 m
3 s
−1 ”. Thus, 1 kμ = 1 Wb.
All in all, the equivalence between all the units is:
1 atkinson = 0.0597 gaul = 0.0061 kμ.
Exercise 4.4 Based on the above definitions, find the conversion factor from murgues
to gauls.
Solution
Let us start by applying the definition of murgue:
R =
Q 2 =
1
gf
m 2
1
m 3
s
2 =
1 gf s
2
m 8
Its conversion to the SI will, therefore, be:
Typical Values of Atkinson Friction Factors (Total Coefficients)
Although specific measurements of friction factors at each mine are required, preliminary studies can be based on existing literature. Thus, a good reference may be
Prosser and Wallace (1999), where the authors make their own measurements and
compare them with those found in classical literature (Table 4.1).
6 gf = gram force.