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In a mine ventilation system, the resistances of two splits A and B are 0.5 Ns<sup>2</sup>m<sup>-8</sup> and 2 Ns<sup>2</sup>m<sup>-8</sup> respectively. Combined resistance of two shafts and trunk airways is 0.7 Ns<sup>2</sup>m<sup>-8</sup>. A quantity of 20 m<sup>3</sup>/s of air passes through split A. The total air quantity passing the mine in m<sup>3</sup>/s is
A
30
B
27
C
25
D
17
Correct Answer:
30
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
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 power of the ventilation system in kW are
A
82.9
B
48.9
C
24.9
D
27.9
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 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
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
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
The figure shows PV (pressure-volume) diagram of a mine ventilated by both natural means and an exhaust fan. The total ventilation energy is represented by
A
Area ABF + Area CDEF
B
Area ABRS + Area CDEF
C
Area ABRS + Area QDCR
D
Area ABF + Area QDCR
The resistances of each branches KL, LM, MN, NK is R and that of LN is 1.414 R. the equivalent resistance between K and M is
A
R
B
0.5 R
C
0.75 R
D
2 R
While measuring average air velocity of air flowing through a circular duct using precise traversing with equal area method, the radii r
1
, r
2
and r
3
, in mm, as shown in the figure of the three circles should be
A
83, 167 and 240
B
36, 107 and 261
C
102, 177 and 228
D
108, 157 and 216
