Bissoy
Login
Get Advice on Live Video Call
Earn $ Cash $ with
consultations on Bissoy App
A mine fan produces 30 m<sup>3</sup>/s of air at 240 Pa pressure running at 1400 rpm. If the fan speed is increased to 2100 rpm, the pressure in Pa and the quantity in m<sup>3</sup>/s generated by the fan will be
A
540 and 67.5
B
540 and 45.0
C
360 and 45.0
D
540 and 30.0
Correct Answer:
540 and 45.0
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
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
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
A main fan of a mine circulates 40 m
3
/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
2
/m
8
. 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
3
/s is
A
20
B
30
C
40
D
50
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%. the fan pressure in Pa is
A
50
B
350
C
500
D
650
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
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
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
. The mine quantity in m
3
/s is
A
160
B
56.57
C
45.9
D
40
The main fan operating point of a ventilation system is shown in the figure below. If an NPV of 200 Pa assists the ventilation system, the resultant pressure (Pa) and quantity (m
3
) generated by the
A
500, 681
B
600, 63
C
640, 55
D
400, 63
E
640, 66
A fan running at 200 rpm develops a pressure of 50 mm water gauge; the fan speed is increased to 300 rpm. the water gauge developed will be
A
75 mm
B
112.5 mm
C
164 mm
D
97 mm
