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Energy Engineering Multiple Choice Questions on “Cooling Ponds and Towers”.
1. Open cooling system is also called as ____________
A. parallel system
B. once through system
C. air based system
D. non-reversible system
Answer: B
clarification: Open system is also called as once through system, in this system the water is drawn directly from the upstream side of the river pumped through the condenser and discharged to the downstream side of the river at temperature 5 to 10°C in excess of inlet temperature.
2. How many number of spray nozzle does each module on spray pond cooling system contains?
A. 1
B. 2
C. 3
D. 4
View Answer
Answer: D
clarification: Modules in spray pond cooling system contain 4 spray nozzles. The surface area of contact of water is increased when it is sprayed in air. Cooling occurs due to the evaporation of water vapours as the spray propels upwards and falls down to the surface.
3. Which of the following is the simplest method of cooling the condenser water?
A. Spray cooling pond
B. Cooling tower
C. Indirect air cooling
D. Hyperbolic cooling tower
Answer: A
clarification: Spray cooling pond is the simplest method of all. The hot water coming out of the condenser is sprayed through the nozzles to expose maximum surface area of water to air for effective cooling. The spray ponds are surrounded with wooden walls to prevent the wind from carrying the water particles.
4. In which type of cooling pond system are nozzles arranged on same elevation?
A. Single deck system
B. Double deck system
C. Natural Flow system
D. Direct flow system
Answer: A
clarification: In a single deck system spray nozzles are arranged at the same elevation. Its effective cooling effect is less than double deck system. Hot water is sprayed through the spray nozzle in air. Cooling occurs due to the evaporation of water vapors at the spray propels and falls down the surface.
5. In which type of cooling system are nozzles arranged on different elevation?
A. Single deck system
B. Double deck system
C. Natural Flow system
D. Direct flow system
Answer: B
clarification: In double system of cooling ponds the spray nozzles are arranged at different elevations. Cooling effect is more than single deck cooling system as water comes in contact with air at lower temperatures.
6. What are used in the direct flow system to transverse the pond before uniting at intake?
A. Separators
B. Filters
C. Baffle walls
D. Porous pipes
Answer: C
clarification: In direct flow system the hot water coming out of the condenser enters the middle channel. On reaching the far end it is divided into two currents being directed by the baffle walls so as to transverse the pond several times before uniting at intake point.
7. Select the disadvantage of cooling pond out of the given?
A. The area required of cooling in a cooling pond is small
B. Spray losses due to evaporation and windage run high
C. There is no control over the temperature of cooled water
D. The cooling efficiency is low compared with cooling water
Answer: C
clarification: The cooling effect is reduced with the decrease in wind velocity and if the load on the plant increases, the pond does not respond to the requirement. When the maximum cooling is required during increased load, it provides minimum cooling in absence of wind flow.
8. What type of cooling system is used in the large power plants?
A. Cooling ponds
B. Natural flow system
C. Cooling towers
D. Single deck system
Answer: C
clarification: In large power plants cooling towers are used in the place of cooling ponds. A cooling tower is a wooden or metallic rectangular structure, with packed baffling devices. The hot water is delivered to the top of tower and is made to fall down the tower and is broken into small particles while passing over the baffling devices.
9. How does outside air enter into the wet cooling system?
A. Air vents
B. Louvers
C. Tuyeres
D. Vacuum
View Answer
Answer: B
clarification: Air and water are thoroughly mixed by fill as water splashes down from one fill level to the next due to gravity outside air enters the tower through louvers from the side of the tower. The heat and mass transfer between water and air is enhanced due to intimate mixing.
10. How is water circulated throughout the dry cooling tower system?
A. Finned tubes
B. Metal pipes
C. Porous tubes
D. Swirling tubes
Answer: A
clarification: In dry cooling tower circulating water is passed through finned tubes over which cooling air is passed. Heat is rejected to air in the form of sensible heat. A dry cooling tower may be either natural draft type or forced draft type. These types are cheap than wet types of cooling tower.
11. Why is exhaust steam coming out of turbine is admitted to a steam header?
A. To increase the pressure
B. To decrease the velocity
C. To decrease the pressure drop
D. To control the pollution
Answer: C
clarification: Exhaust steam from turbine is admitted to a steam header in order to minimize the pressure drop. Steam gets condensed as it passes down through the finned tubes arranged in parallel rows.
12. In which system is Cooling of hot water is done on tray as step by?
A. Mechanical draught cooling system
B. Hyperbolic cooling tower
C. Atmospheric cooling tower
D. Wet cooling tower
Answer: C
clarification: In atmospheric cooling tower, the hot water is delivered at the top most trays and it falls down from one tray to another until it reaches the tank below the tower. The water is cooled by air flowing across the tower.
13. How does the flow of air occur in natural draught cooling towers?
A. Natural pressure head density between cold outside air and humid inside air
B. Variation in pressure of both cold outside air and humid inside air
C. Due to the given air vents and vacuum ports
D. Because of difference in the volume of both the of airs
View Answer
Answer: A
clarification: In natural draught cooling tower, the flow of air occurs due to the natural pressure head caused by density difference between the cold outside air and hot humid air inside. The disadvantage of natural draught cooling system is that, to produce to produce large draught the tower should be very high.
14. How is air produced in mechanical draught cooling tower?
A. Air Tuyeres
B. Propeller fans
C. Air blowers
D. Louvre
Answer: B
clarification: In mechanical draught cooling tower the draught of air id produced mechanically by means of propeller fans. This increases the cooling rate by increasing the air velocity over the wet surfaces and through the tower. These two towers give higher efficiency; reduce spray and windage losses and less ground area.
15. Why is induced draught considered better than the forced draught?
A. Because power requirement is high for forced draught
B. Maintenance of induced draught fan is costlier
C. Forced draught is less efficient
D. Forced draught produces less amount of speed of air
View Answer
Answer: A
clarification: Induced draught is considered to be better than forced draught because, the power requirement is high for forced draught and the maintenance of fan is costlier. The induced draught occupies less space ass the fan drives are placed at the top of the tower, the cooling effect is distributed across the entire cross section of the tower.