QUESTION BANK

POWER PLANT PERFORMANCE

1. Increase in heat rate of a power plant infers to( a ) Increasing Efficiency( b ) Decreasing efficiency( c ) No effect( d ) None of the above

2. Unit of Heat Rate is( a ) KwH / KCal( b ) Kcal / KwH( c ) Dimensionless quantity i.e. no units( d ) None of the above

3. Reheating enables the designer to increase the upper limit of working pressure while keeping the exhaust wetness in limit.

( a ) True( b ) False( c ) Reheating has no such effect on wetness.( d ) None of the above

4. Out of the following parameters which of these affect the dry flue gas losses( a ) Lack of Soot blowing.( b ) High Excess air( c ) Burner Tilt( d ) All of the above

5. Amount of oxygen required for complete combustion of hydrogen present in coal to form moisture is

( a ) Equal to eight times the weight of hydrogen in coal.( b ) Slightly less than eight times the weight of hydrogen in coal.( c ) Slightly Greater than eight times the weight of hydrogen in coal.( d ) None of the above

6.Excess air monitoring to maintain the efficiency of the boiler is done at( a ) Air Pre Heater gas side inlet.( b ) Air Pre Heater gas side outlet.( c ) Air Pre Heater air side inlet.( d ) Air Pre Heater air side outlet.

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7.Increase in entropy with the flow of steam from one stage to another of turbine depicts( a ) Increase in efficiency of turbine.( b ) Decrease in efficiency of turbine.( c ) It will not effect the efficiency of turbine at all.( d ) None of the above

8. What is the distribution of the power output of the H.P. I.P. and L.P. turbines operating in a fossil power plant?( a ) 28%, 22%, 50%( b ) 50%, 40%, 10%( c ) 80%, 10%, 20%( d ) 15%, 12%, 73%

9. Which of the following has the largest effect on heat rate?( a ) Decreasing mainstream temperature 1%( b ) Decreasing reheat temperature 1%( c ) Taking a heater out of the cycle.( d ) Decreasing mainstream pressure 1%

10.Which of the following parameters do not affect the performance of condenser directly.( a ) Air ingress.( b ) Increase in CW Outlet Temperature.( c ) Increase in CW Inlet Temperature.( d ) Change in mass flow rate of cooling water through condenser.

11. Assertion: Decrease in CW flow leads to decrease in condenser performance. Reason: Less CW flow causes an increase in CW Outlet Temperature.( a ) Assertion is true but reason is false.( b ) Assertion is false but reason is True.( c ) Both assertion and reason are true and reason is correct explanation of assertion.( d ) Both assertion and reason are true but reason is not the correct explanation of assertion.

12. Increase in CW Inlet temperature at condenser as compared to optimum value leads to ( a ) Increase in condenser back pressure and hence more output.( b ) Decrease in condenser back pressure and hence more output.( c ) Increase in condenser back pressure and hence less output.( d ) Decrease in condenser back pressure and hence less output.

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13. Repairing condenser air leaks leads to( a ) Increase in condenser back pressure and hence more output of turbine.( b ) Decrease in condenser back pressure and hence more output of turbine.( c ) Increase in condenser back pressure and hence less output of turbine.( d ) Decrease in condenser back pressure and hence less output of turbine.

14. Bio fouling effects in condenser tubes leads to( a ) Increase in condenser back pressure and hence more output of turbine.( b ) Decrease in condenser back pressure and hence more output of turbine.( c ) Increase in condenser back pressure and hence less output of turbine.( d ) Decrease in condenser back pressure and hence less output of turbine.

15. Assertion: Deteoration in cooling tower performance reduces condenser performance Reason: Increase in cooling water temp at inlet reduces the condenser back pressure.( a ) Assertion is true but reason is false.( b ) Assertion is false but reason is True.( c ) Both assertion and reason are true and reason is correct explanation of assertion.( d ) Both assertion and reason are true but reason is not the correct explanation of assertion

16. The design wet bulb temperature for cooling towers is usually selected at…..( a ) Peak summer temperature.( b ) Peak winter temperature.( c ) Peak rainy season Temperature.( d ) Can be taken for anytime of the year.

17. Pre dominant cooling mechanism of a wet cooling tower is( a ) Evaporation.( b ) Convection( c ) Radiation( d ) None of the above.

18. Cooling tower Recirculation and interference leads to …………… in wet bulb temperature thus ……………..affecting the tower performance.( a ) Increase, Negatively( b ) Decrease, Negatively.( c ) Increase, Positively.( d ) Decrease, Positively.

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19. Natural draft cooling towers have ………. Recirculation and interference problems and hence ………….. Recirculation allowance is recommended for this type of cooling towers.( a ) Low, Very less( b ) High, Very high.( c ) Low, Very high( d ) High, Very low.

20. Pre dominant cooling mechanism of a dry cooling tower is( a ) Evaporation.( b ) Convection( c ) Radiation( d ) Both b and c.

21. Difference between the hot water temperature (inlet to CT) and cold water temperature (outlet of CT) is defined as( a ) Range ( b ) Approach( c ) Effectiveness.( d ) Terminal Temp difference.

22. An increase in value of the parameter “APPROACH” leads to ………….. , in size of cooling towers.( a ) Always Increase( b ) Always Decrease( c ) Sometimes increase & sometimes decrease.( d ) No effect

23. Operating the air pre heater soot blowing leads to…………., in dry flue gas losses.( a ) Always Increase( b ) Always Decrease( c ) Sometimes increase & sometimes decrease.( d ) No effect

24. Which of the following operating parameter variation will positively affect the heat rate.( a ) Reduced furnace oxygen level.( b ) Negligence in condenser tube cleanliness.( c ) Improper cycle isolation.( d ) None of the above.

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25. Damaged flash box internals (used to separate two passes of feed water in FW Heaters) leads to( a ) Increase in TTD and decrease in DCA( b ) Decrease in TTD and increase in DCA( c ) Increase in TTD and no effect on DCA( d ) No effect on TTD and an increase in DCA.

26. Which of the following statements is true?

Statement 1: TTD is an indicator of amount of heat transfer. Statement 2: DCA is an indicator of heater level Statement 3. DCA is more dominating factor as compared to TTD in heat rate

deviations Statement 4: TTD is more dominating factor as compared to DCA in heat rate deviations( a ) 1 & 2 only( b ) 1 2 & 4( c ) Only 1( d ) 1 2 & 3

27. Passing of High Energy drain valve affects in

( a ) Loss of High Energy steam

( b ) Deterioration in Condenser Vacuum

( c ) Damage to the valve ( d ) All of the above.

28. Which of the following is not an unaccounted loss in power plant( a ) Radiant heat losses in boilers( b ) Mill reject loss( c ) passing of high energy drain valves( d ) piping radiation losses in turbine area.

29. Correct order of losses in seals of turbine is( a ) Tip seal losses > Inter stage seal losses> Shaft seals( b ) Tip>Shaft> Inter stage( c ) Shaft > Tip > Inter stage( d ) Inter stage > Shaft >Tip

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30. Which of following if increased will lead to better mill performance( a ) Volatile matter content in coal( b ) Moisture content( c ) HGI( d ) Ash content.

31. Which of the following is the correct order of turbine efficiencies( a ) HPT>IPT>LPT( b ) IPT>LPT>HPT( c ) IPT>HPT>LPT( d ) LPT>IPT>HPT

32. Which of the following will have a positive impact on thermal cycle efficiency( a ) Increased cycle make up( b ) Increased turbine exhaust pressure.( c ) Decreased TTD and DCA( d ) Increased condensate sub cooling.

33. Reheater spray has a more dominating impact on decreasing the heat rate as compared to superheater spray.( a ) True( b ) False

34. In a certain project of NTPC the swampy area near the cooling towers was paved with fly ash bricks. What would be the effect on CT performance if all other conditions remain as it is?( a ) Increase ( b ) decrease( c ) No affect

35. Arrange the following losses in power plant in correct sequenceHeat rejected in condenser: q1Dry flue gas losses: q2Radiant heat losses in boiler & piping of turbine: q3( a ) q1>q2>q3( b ) q3>q2>q1( c ) q1>q3>q2( d ) q2>q1>q3

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