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A main fan of a mine circulates 40 m<sup>3</sup>/s of air at a pressure of 500 Pa. the mine has two splits of equal resistance. The trunk airways have a total resistance of 0.2 Ns<sup>2</sup>/m<sup>8</sup>. When a booster fan is installed in one split, the flow of air in the other splits stops. Assuming that the pressure remains unchanged, the new air quantity flowing through the mine in m<sup>3</sup>/s is
A
20
B
30
C
40
D
50
Correct Answer:
50
A mine ventilation system consists of two splits A and B with resistances of 0.8 Ns
2
m
-8
and 3.2 Ns
2
m
-8
, respectively as shown in figure. Trunk airways have resistance of 0.2 Ns
2
m
-8
. The main mine fan is generating pressure of 500 Pa.
The flows in the two splits are equalized by placing a booster fan in split B. Assume that the fan pressure does not change after installation of the booster fan. The size of the booster fan in Pa is
A
749.05
B
850.08
C
950.02
D
1000.5
The resistances of two splits A and Bare 0.35 Ns
2
m
-8
and 0.05 Ns
2
m
-8
respectively. The combined resistance of the shafts and trunk airways is 0.4 Ns
2
m
-8
. A booster fan is planned to be installed in split A to increase the quantity flowing through it. Assuming that the surface fan continues to operate at a constant pressure of 1000 Pa, the critical pressure of the booster fan in Pa is
A
675
B
875
C
825
D
625
A mine ventilation system consists of two splits A and B with resistances of 0.8 Ns
2
m
-8
and 3.2 Ns
2
m
-8
, respectively as shown in figure. Trunk airways have resistance of 0.2 Ns
2
m
-8
. The main mine fan is generating pressure of 500 Pa.
The air quantities in m
3
/s circulated in the splits A and B respectively are
A
20 and 30
B
30 and 20
C
20 and 10
D
40 and 10
In a mine ventilation system, the resistances of two splits A and B are 0.5 Ns
2
m
-8
and 2 Ns
2
m
-8
respectively. Combined resistance of two shafts and trunk airways is 0.7 Ns
2
m
-8
. A quantity of 20 m
3
/s of air passes through split A. The total air quantity passing the mine in m
3
/s is
A
30
B
27
C
25
D
17
The fan drift pressure readings and fan quantities are measured to be 500 Pa and 65 m
3
/s respectively at the time when NVP aids fan pressure. On reversal, the fan delivers a quantity of 50 m
3
/s while acting against NVP with fan drift pressure of 600 Pa. Assuming that the NVP remains constant in both cases the total resistance of the mine in Ns
2
/m
8
will be
A
0.9487
B
0.2750
C
0.4105
D
0.1635
Pressure characteristic of a mine fan is given by. P = -0.06Q
2
+ 400. where P is the pressure in Pa and Q is the quantity in m
3
/s. The resistance of the mine is 0.19 Ns
2
/m
8
. An identical fan is installed in the mine to operate in series with the existing fan. The new mine quantity in m
3
/s is
A
75.6
B
56.7
C
50.8
D
30.2
In a mine ventilation system, the resistances of two splits A and B are 0.5 Ns
2
m
-8
and 2 Ns
2
m
-8
respectively. Combined resistance of two shafts and trunk airways is 0.7 Ns
2
m
-8
. A quantity of 20 m
3
/s of air passes through split A. The total air power of the ventilation system in kW are
A
82.9
B
48.9
C
24.9
D
27.9
A fan running at a speed of 280 rpm circulates 105 m
3
/s of air in a mine. If the power input to the motor for driving the fan is recorded to be 75 kW, with the combined efficiency of fan and motor at 70%. If the fan pressure is to be increased by 200 Pa by changing the fan speed. the fan speed in rpm will become
A
768
B
549
C
392
D
332
Two splits A and B are ventilated from an intake airway. Resistances of the splits are 0.5 Ns
2
m
-8
and 0.8 Ns
2
m
-8
respectively. A regulator is placed in split B to maintain a flow of 15 m
3
/s and 10 m
3
/s in splits A and B respectively as shown in the figure. The size of the regulator in m
2
is
A
2.1
B
1.3
C
1.2
D
1.13
A fan circulates 24 m
3
/s of air at a pressure of 1200 Pa in a ventilation district. It is intended to reduce the air quantity to 16 m
3
/s by placing a regulator. Assuming the pressure remains unchanged, the size of the regulator in m
2
is
A
1.48
B
0.74
C
0.37
D
0.18
