Power Plant Engineering MCQ

61. In Rankine cycle, the work output from a turbine is given by

(a) change of enthalpy between inlet and outlet.
(b) change in internal energy between inlet and outlet.
(c) change of entropy between inlet and outlet.
(d) change in temperature between inlet and outlet.

62. Binary vapor cycles are used for

(a) increasing the turbine efficiency.
(b) improving the condenser performance.
(c) improving the plant efficiency.
(d) all of the above.

63. Binary vapor cycles are not being adopted because

(a) initial cost of such plants is high.
(b) such plants are suitable for high load factors only.
(c) pipes of thicker sections are required.
(d) ideal vapors are not available.

64. The overall efficiency of a thermal power station is equal to

(a) that of Rankine cycle.
(b) that of regenerative cycle.
(c) that of Binary vapour cycle.
(d) product of boiler efficiency, turbine efficiency and generator efficiency.

65. Rankine cycle operating between pressure limits of P₁ and P₂ has thermal efficiency

(a) lower than that of Carnot cycle operating between same pressure limits.
(b) higher than that of Carnot cycle operating between same pressure limits.
(c) same as that of Carnot cycle operating between same pressure limits.
(d) none of the above.

66. Reheat cycle in a steam power station is employed for

(a) improving thermal efficiency.
(b) improving condenser performance.
(c) reducing heat losses.
(d) utilizing heat of flue gases.

67. In a regenerative cycle, feed water is heated by

(a) heaters.
(b) drained steam from the turbine.
(c) exhaust gases.
(d) all of the above.

68. In a regenerative feed heating cycle,

(a) the optimum value of the fraction of steam extracted for feed water heating increases with the increase in Rankine cycle efficiency.
(b) the greatest economy is affected when steam is extracted from several places in different stages of the steam turbine.
(c) thermal efficiency is reduced.
(d) both (a) and (b).

69. What is the approximate efficiency of a normal thermal power station?

(a) 30 – 40%
(b) 45 – 55%
(c) 20 – 25%
(d) 60 – 70%

70. In a thermal power station, a typical heat balance sheet, for a large turbine and surface condenser taken together, is the percentage distribution of heat energy in:

1. work done or thermal efficiency.
2. friction and windage loss.
3. heat to circulating water.
4. heat in condensate to be retained to the boiler.

The percentage amount of heat in the heads stated above, in the descending order is:
(a) 3, 4, 1 and 2.
(b) 2, 1, 4 and 3.
(c) 3, 1, 4 and 2.
(d) 2, 4, 1 and 3.

71. Maximum efficiency of modern coal fired steam-raising thermal power plants is restricted to about 0.35 (a low value), mainly because of

(a) low alternator efficiency.
(b) high energy ions in boilers.
(c) low steam turbine mechanical efficiency.
(d) high energy loss from turbine exhaust to condenser.

72. Which of the following contributes to the Rankine cycle efficiency improvement in a steam power plant ?

(a) Use of high pressure.
(b) Reheat of steam at intermediate stages.
(c) Use of steam for heating of boiler feed water.
(d) All of the above.

73. The steam power plant efficiency can be improved by

(a) using large quantity of water.
(b) burning large quantity of coal.
(c) using high pressure and high temperature steam.
(d) decreasing the load on the plant.

74. The average load factor of thermal power plants in India is

(a) 100%
(b) 80 – 95%
(c) 50 – 60%
(d) 35 – 45%
(e) 20 – 30%

75. As the size of a thermal generating unit increases, the capital cost per kW of installed capacity

(a) increases.
(b) decreases.
(c) remains the same.
(d) may increase or decrease.

76. The modern trend in electric power generation is

(a) to have a large number of small size thermal plants located at different places.
(b) to have large size thermal plants near load centers.
(c) to have large size thermal plants located near coal fields.
(d) none of the above.

77. In the feed water and steam circuit of a thermal power plant, the condensate flows from the condensate extraction pump to the boiler feed pump and, then to the boiler. The HP and LP heaters are located in this circuit in relation to the boiler feed pump (BFP) as

(a) both HP and LP heaters after BFP.
(b) HP heater before and, LP heater after BFP.
(c) both HP and LP heaters before BFP.
(d) LP heater before and, HP heater after BFP.

78. In thermal power plants, the pressure in the working fluid cycle is developed by

(a) condenser.
(b) superheater.
(c) feed water pump.
(d) turbine.

79. Deaerative heating is done to

(a) heat the steam.
(b) heat the feed water.
(c) remove dissolved gases in water.
(d) remove dissolved solid impurities in water.

80. In a thermal power plant, the feed water coming to the economiser is heated using

(a) HP steam.
(b) LP steam.
(c) direct heat in the furnace.
(d) flue gases.