Power Plant Engineering

71. The draught produced, for a given height of the chimney and given mean temperature of chimney gases

1. decreases with increase in outside air temperature
2. increases with increase in outside air temperature
3. remains the same irrespective of outside air temperature
4. may increase or decrease with increase in outside air temperature

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72. The draught which a chimney produces is called

1. induced draught
2. natural draught
3. forced draught
4. balanced draught

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73. The effect of considering friction in steam nozzles for the same pressure ratio leads to

1. increase in dryness fraction of exit steam
2. decrease in dryness fraction of exit steam
3. no change in the quality of exit steam
4. decrease or increase of dryness fraction of exit steam depending upon inlet quality

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74. The effect of considering friction losses in steam nozzle for the same pressure ratio leads to

1. increase in exit velocity from the nozzle
2. decrease in exit velocity from the nozzle
3. no change in exit velocity from the nozzle
4. increase or decrease depending upon the exit quality of steam

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75. The efficiency of a modern boiler using coal and heat recovery equipment is about

1. 25 to 30%
2. 40 to 50%
3. 65 to 70%
4. 85 to 90%

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76. The efficiency of chimney is approximately

1. 80%
2. 40%
3. 20%
4. 0.25%

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77. The energy radiated by sun on a bright sunny day is approximately

1. 700 W/m2
2. 800 W/m2
3. 1 kW/m2
4. 2 kW/m2

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78. The isentropic expansion of steam through nozzle for the steam initially dry saturated at inlet is approximated by equation.

1. pv = C
2. pv1A = C
3. pv1i = C
4. pv

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79. The isentropic expansion of steam through nozzle for the steam initially superheated at inlet is approximated by equation

1. pvls=C
2. pv1126 = C
3. pv1A = C
4. pv = C

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80. The main source of production of biogas is

1. human waste
2. wet cow dung
3. wet livestock waste
4. all above

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