230
6 Fans and Flow Control Devices
Airflow rate
25
1 fan
2 fans
a)
Pressure
20
10
25
10
20
b)
Fig. 6.31 a Parallel fan connection diagram; b characteristic curves of parallel connection of two
equal fans
Question 6.3 You have determined the pressure and airflow rate required to ventilate
a mine. The largest fan available supplied by the manufacturer is insufficient for the
air quantity demand of the mine. One of the members of your team is inclined to
place two fans in series, another to place two in parallel and a third comments on
the possibility of splitting the air currents. Discuss which of the above decisions are
correct and the price of each one of them.
Answer
To place two fans in parallel would allow us to increase the airflow rate supplied,
while placing them in series would not. Splitting the airflow will decrease the total
mine resistance, but may result in insufficient airflow rate in each split, so additional
checks should be carried out. This decision, although it may be the cheapest from
the point of view of energy consumption, requires earth movement for the execution
of the additional galleries, thus greatly increasing costs.
Exercise 6.8 To undertake successfully the secondary ventilation of a development
heading 45.8 m
3 s
−1 of air are needed at the face. The leaking calculations made
indicate that this can be carried out by means of a forcing system in which the fan
blows 46.21 m
3 s
−1 (Q fan ) at a pressure of 4861.7 Pa (P fan ). The following data is also
available:
System impedance curve:
Q v
P
0
0
10
228
20
911
30
2049
40
3643
50
5693
55
6888
6 Fans and Flow Control Devices
Airflow rate
25
1 fan
2 fans
a)
Pressure
20
10
25
10
20
b)
Fig. 6.31 a Parallel fan connection diagram; b characteristic curves of parallel connection of two
equal fans
Question 6.3 You have determined the pressure and airflow rate required to ventilate
a mine. The largest fan available supplied by the manufacturer is insufficient for the
air quantity demand of the mine. One of the members of your team is inclined to
place two fans in series, another to place two in parallel and a third comments on
the possibility of splitting the air currents. Discuss which of the above decisions are
correct and the price of each one of them.
Answer
To place two fans in parallel would allow us to increase the airflow rate supplied,
while placing them in series would not. Splitting the airflow will decrease the total
mine resistance, but may result in insufficient airflow rate in each split, so additional
checks should be carried out. This decision, although it may be the cheapest from
the point of view of energy consumption, requires earth movement for the execution
of the additional galleries, thus greatly increasing costs.
Exercise 6.8 To undertake successfully the secondary ventilation of a development
heading 45.8 m
3 s
−1 of air are needed at the face. The leaking calculations made
indicate that this can be carried out by means of a forcing system in which the fan
blows 46.21 m
3 s
−1 (Q fan ) at a pressure of 4861.7 Pa (P fan ). The following data is also
available:
System impedance curve:
Q v
P
0
0
10
228
20
911
30
2049
40
3643
50
5693
55
6888