# Thermal Power Plant Objective Questions and Answers(PDF)

### Thermal Power Plant Objective Questions and Answers(PDF) for Electrical and Mechanical Engineers

1.The critical pressure ratio of a convergent nozzle is defined as
(a) the ratio of outlet pressure to inlet pressure of nozzle
(b) the ratio of inlet pressure to outlet pressure of nozzle
(c) the ratio of outlet pressure to inlet pressure only when mass flow rate per unit area is minimum
(d) the ratio of outlet pressure to inlet pressure only when mass flow rate = c
Ans: d

2.The isentropic expansion of steam through nozzle for the steam initially dry saturated at inlet is approximated by equation.
(a) pv = C
(b) pv1A = C
(c) pv1i = C
(d) pv
Ans: d

3.The effect of considering friction losses in steam nozzle for the same pressure ratio leads to
(a) increase in exit velocity from the nozzle
(6) decrease in exit velocity from the nozzle
(c) no change in exit velocity from the nozzle
(d) increase or decrease depending upon the exit quality of steam
Ans: b

4.In case of impulse steam turbine
(a) there is enthalpy drop in fixed and moving blades
(b) there is enthalpy drop only in moving blades
(c) there is enthalpy drop in nozzles
(d) none of the above
Ans: c
5.The artificial draught normally is designed to produce
(a) less smoke
(b) morr draught
(c) less chimney gas temperature
(d) all of the above
Ans: d

6.For the induced draught the fan is located
(a) near bottom of chimney
(b) near bottom of furnace
(c) at the top of the chimney
(D) anywhere permissible
Ans: a

7.The pressure at the furnace is minimum in case of
(a) forced draught system
(b) induced draught system
(c) balanced draught system
(d) natural draught system
Ans: c

8.The efficiency of chimney is approximately
(a) 80%
(b) 40%
(c) 20%
(d) 0.25%
Ans: d

9.The isentropic expansion of steam through nozzle for the steam initially superheated at inlet is approximated by equation
(a) pvls=C
(b) pv1126 = C
(c) pv1A = C
(d) pv = C
Ans: a

10.The ratio of exit pressure to inlet pressure for maximum mass flow rate per unit area of steam through a nozzle when steam is initially dry saturated is
(a) 0.6
(6) 0.578
(c) 0.555
(d) 0.5457
Ans: b

11.The ratio of exit pressure to inlet pressure of maximum mass flow rate per area of steam through a nozzle when steam is initially superheated is
(a) 0.555
(b) 0.578
(c) 0.5457
(d) 0.6
Ans: c

12.For forced draught system, the function of chimney is mainly
(a) to produce draught to accelerate the combustion of fuel
(b) to discharge gases high up in the atmosphere to avoid hazard
(c) to reduce the temperature of the hot gases discharged
(d) none of the above
Ans: b

13.Artificial draught is produced by
(a) induced fan
(b) forced fan
(c) induced and forced fan
(d) all of the above
Ans: d

14.The draught in locomotive boilers is produced by
(a) forced fan
(b) chimney
(c) steam jet
(d) only motion of locomotive
Ans: c

15.For the same draught produced the power of induced draught fan as compared to forced draught fan is
(a) less
(b) more
(c) same
(d) not predictable
Ans: b

16.Artificial draught is produced by
(a) air fans
(b) steam jet
(c) fan or steam jet
(d) all of the above
Ans: d

17.The modern steam turbines are
(a) impulse turbines
(b) reaction turbines
(c) impulse-reaction turbines
(d) none of the above
Ans: c

18.The draught which a chimney produces is called
(a) induced draught
(b) natural draught
(c) forced draught
(d) balanced draught
Ans: b

19.The draught produced by steel chimney as compared to that produced by brick chimney for the same height is
(a) less
(b) more
(c) same
(d) may be more or less
Ans: b

20.In a boiler installation the natural draught is produced
(a) due to the fact that furnace gases being light go through the chimney giving place to cold air from outside to rush in
(b) due to the fact that pressure at the grate due to cold column is higher than the pressure at the chimney base due to hot column
(c) due to the fact that at the chimney top the pressure is more than its environmental pressure
(d) all of the above
Ans: b

21.The draught produced, for a given height of the chimney and given mean temperature of chimney gases
(a) decreases with increase in outside air temperature
(b) increases with increase in outside air temperature
(c) remains the same irrespective of outside air temperature
(d) may increase or decrease with increase in outside air temperature
Ans: a

22.Mercury is a choice with steam in binary vapour cycle because it has
(a) higher critical temperature and pressure
(b) higher saturation temperature than other fluids
(c) relatively low vapourisation pressure
(d) all above
Ans: d

23.Binary’vapour cycles are used to
(a) increase the performance of the condenser
(b) increase the efficiency of the plant
(c) increase efficiency of the turbine
Ans: b

24.A steam power station requires space
(a) equal to diesel power station
(b) more than diesel power station
(c) less than diesel power station
Ans: b

25.Economiser is used to heat
(a) air
(b) feed water
(c) flue gases
(d) all above
Ans: b
26.The effect of considering friction in steam nozzles for the same pressure ratio leads to
(a) increase in dryness fraction of exit steam
(b) decrease in dryness fraction of exit steam
(c) no change in the quality of exit steam
(d) decrease or increase of dryness fraction of exit steam depending upon inlet quality
Ans: a

27.The draught produced by chimney of given height at given outside temperature
(a) decreases if the chimney gas temperature increases
(b) increases if the chimney gas temperature increases
(c) remains same irrespective of chimney gas temperature
(d) may increase or decrease
Ans: b