Home/Volume-2/Underground Environment and Mine Ventilation Volume-2 Underground Environment and Mine Ventilation Admin03/08/20240 136 Less than a minute Report a question What's wrong with this question? You cannot submit an empty report. Please add some details. 0% Underground Environment and Mine Ventilation Underground Environment and Mine Ventilation 1 / 36 1. If the wet bulb temperature exceeds 30.5 deg c at any place air current should be faster than? 1 m/s 2 m/s 3 m/s 0.5 m/s 2 / 36 2. Upto what depth from the surface the temperature is constant? 20m 25m 10m 15m 3 / 36 3. The unit for the kata factor is? millicalories/sq.cm/sec kcal/sec/sq.cm millicalories/sq.cm millicalories/sec/sq.cm 4 / 36 4. By varying the pitch of the blades the pressure generated by axial flow fan is? remains same decreases increases increases 8 times 5 / 36 5. The speed of the centrifugal fan is? 1 to 100 rpm 100 to 300 rpm 300 to 1000 rpm above 1000 rpm 6 / 36 6. The water gauge developed and quantity circulated with an axial flow fan depend on? Size of the fan Shape of the blades Design of the evasee Speed of the blade tips 7 / 36 7. The presence of Nitrous fumes are detected by? The rotten eggs smell sweet smell metallic taste on tongue headache 8 / 36 8. Cooling power is a combination of temperature of air; relative humidity and ...? Moisture content of air density of air velocity of air Pressure 9 / 36 9. For comfortable working conditions the reasonable velocity of air at the working face is? 0.5 to 2 m/s 3 to 4 m/s 5 m/s 6 m/s 10 / 36 10. With an axial fan, the direction of travel of air current to the mine is changed by? changing direction flow of air into fan by means of doors changing the blades on the rotor changing the direction of rotation of the motor not possible with this type of fan 11 / 36 11. Cooling power by conduction convection and radiation is given by using the? dry bulb temperature wet bulb temperature Average time of wet and dry bulbs wet and dry bulb time and velocity of air 12 / 36 12. The overall efficiency of axial flow fan is? 10 to 20 % 70 to 85 % 20 to 30 % 40 to 50 % 13 / 36 13. The mostly used blade type in centrifugal fan is? backward radial forward none 14 / 36 14. Inclined water gauge is used for the measurement of water gauge for? smaller than 200 mm greater than 200 mm smaller than 50 mm greater than 50 mm 15 / 36 15. The value of the kata factor is? 250 300 380 480 16 / 36 16. The water gauge of an axial flow fan can be increased by? increasing speed of rotation changing the pitch of blades installing 2 or more stages enlarging the evasee of the fan 17 / 36 17. Velocity pressure is measured by? Barometer Inclined manometer U-tube Pitot tube 18 / 36 18. Whirling hygrometer is rotated with a speed of? 100 rpm 200 rpm 300 rpm 400 rpm 19 / 36 19. The manometric efficiency of axial flow fan is? 10 to 20 % 70 to 85 % 20 to 30 % 40 to 50 % 20 / 36 20. Static pressure is measured by? Barometer Pitot tube Venturi meter U-tube 21 / 36 21. In the centrifugal fan reentry of the discharged air is prevented by? spiral casing blades evasee eye 22 / 36 22. The difference between the atmospheric pressure and the total pressure on the fan drift is called? Velocity pressure of surface fan Static pressure Total pressure of surface fan none 23 / 36 23. The pitch of the blades of axial flow fans is? 1 to 5 deg 5 to 10 deg 10 to 15 deg 15 to 20 deg 24 / 36 24. The minimum quantity of air per person in deg III mine is? 6 cu.m/min 8 cu.m/min 10 cu.m/min 12 cu.m/min 25 / 36 25. The maximum water gauge developed in axial flow fan is? 10 cm 12.5 cm 13.5 cm 15 cm 26 / 36 26. For light manual workers the wet kata is? 18 25 30 8 27 / 36 27. The noxious and inflammable gases of old workings of a coal mine expand when there is? sudden rise of temperature sudden heavy roof fall sudden rise in barometric pressure sudden drop in barometric pressure 28 / 36 28. The inclined water gauge can read upto? 2 mm 1.5 mm 1 mm 0.2 mm 29 / 36 29. Ordinary U-tube manometers are not useful for measurement of gas velocities? below 12 m/s 13 to 20 m/s 20 to 30 m/s above 30 m/s 30 / 36 30. The velocity of air flowing in a drift where the velocity pressure is 36 mm is? 36 m/s 24 m/s 42 m/s 48 m/s 31 / 36 31. In the centrifugal fan smooth flow air and conversion of velocity energy into pressure energy takes place? In spiral casing In the blades At the tip of the blades In the evasee 32 / 36 32. The wet bulb temperature in development faces should not exceed? 30 deg c 33.5 deg c 35 deg c 38 deg c 33 / 36 33. The instrument that is used to measure the relative humidity is? pitot tube aneroid barometer hygrometer anemometer 34 / 36 34. With a centrifugal fan for a given quantity of air increase of efficiency and reduction in cost of power can be obtained with? well designed blades of the fan well designed spiral casing well designed evasee well designed eye of the impeller 35 / 36 35. The maximum permissible speed of the axial flow fan is? 8000 m/min 6000 m/min 5200 m/min 4200 m/min 36 / 36 36. Geothermic gradient in Indian coal seam is....? 1 deg c per 15 m 1 deg c per 38m 1 deg c per 50 m none Your score is The average score is 56% LinkedIn Facebook Twitter 0% Admin03/08/20240 136 Less than a minute
