Economisers improve boiler efficiency by__________?

Related Mcqs:

1. The efficiency of a modern boiler using coal and heat recovery equipment is about_____________?

   A. 25 to 30%
   B. 40 to 50%
   C. 65 to 70%
   D. 85 to 90%

2. The overall efficiency of a steam power station is ________ its thermal efficiency.

   A. less than
   B. equal to
   C. greater than
   D. none of the above

3. 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

4. For the safety of a steam boiler the number of safety valves fitted are____________?

   A. four
   B. three
   C. two
   D. one

5. Where unpulverised coal has to be used and boiler capacity is large, the stoker which is used is______________?

   A. underfeed stoker
   B. overfeed stoker
   C. any

6. Blowing down of boiler water is the process_____________?

   A. to reduce the boiler pressure
   B. to increase the steam temperature
   C. to control the solid concentration in the boiler water by removing some of the concentrated saline water
   D. none of the above

7. In Rankine cycle the work output from the turbine is given by__________?

   A. change of internal energy between inlet and outlet
   B. change of enthaply between inlet and outlet
   C. change of entropy between inlet and outlet
   D. change of temperature between inlet and outlet

8. The overall efficiency of thermal power plant is equal to____________?

   A. Rankine cycle efficiency
   B. Carnot cycle efficiency
   C. Regenerative cycle efficiency
   D. Boiler efficiency x turbine efficiency x generator efficiency

9. Rankine cycle efficiency of a good steam power plant may be in the range of____________?

   A. 15 to 20 per cent
   B. 35 to 45 per cent
   C. 70 to 80 per cent
   D. 90 to 95 per ceut

10. The thermal efficiency of the engine with condenser as compared to without condenser, for a given pressure and temperature of steam, is_____________?

    A. higher
    B. lower
    C. same as long as initial pressure and temperature is unchanged
    D. none of the above