21. In a mine ventilation system, the resistances of two splits A and B are 0.5 Ns2m-8 and 2 Ns2m-8 respectively. Combined resistance of two shafts and trunk airways is 0.7 Ns2m-8. A quantity of 20 m3/s of air passes through split A. The total air quantity passing the mine in m3/s is
22. Model OXD-2M O2 defficiency meter contains rechargable battery of . . . . . . . .
23. A fan circulates 24 m3/s of air at a pressure of 1200 Pa in a ventilation district. It is intended to reduce the air quantity to 16 m3/s by placing a regulator. Assuming the pressure remains unchanged, the size of the regulator in m2 is
24. A mine fan produces 30 m3/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 m3/s generated by the fan will be
25. Air flows at 2 m3/s through a forcing fan duct of 0.3 m2 having uniform cross-section. The duct resistance is 40 Ns2m-8 and air density is 1.2 kg/m3. The total pressure generated by the fan in Pa is
26. While measuring average air velocity of air flowing through a circular duct using precise traversing with equal area method, the radii r1, r2 and r3, in mm, as shown in the figure of the three circles should be
27. 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
28. Ignition temperature of methane is
29. An exhaust fan attached to an evasee of 18 m2 cross-sectional area at the outlet circulates 150 m3/s of air at the pressure of 1000 Pa in a mine ventilation system. The ratio of the inlet to outlet area of the evasee is 1 : 4 and the density of air is 1.2 kg/m3. The quantity of air circulated in the mine in absence of evasee is 120 m3/s. The eva see efficiency in % is
30. A coolant is desirable component in the design of a self- contained breathing apparatus since
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