# Thermal Engineering Questions and Answers – Steam Condensers – Cooling Towers

This set of Thermal Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Steam Condensers – Cooling Towers”.

1. What is the function of a cooling tower in a power plant?
a) It cools the hot water coming back from the condenser
b) It cools the hot water being supplied to the condenser
c) It heats the cold water coming back from the condenser
d) It heats the cold water being supplied to the condenser

Explanation: The cooling water that is passed through the condenser, for condensing steam coming out of the turbine, gets heated and in order to cool that water down, cooling towers are used. So that the water can be reused again.

2. Which of the following phenomenon is used to cool water in a cooling tower?
a) Evaporation
c) Condensation
d) Conduction

Explanation: In a cooling tower, hot water is allowed to fall drop by drop and air is constrained to move in the opposite direction. This results in some part of water getting evaporated. Due to this the rest of the water is cooled.

3. Humidity of air affects the cooling of water in a cooling tower.
a) True
b) False

Explanation: Humidity of air affects the evaporation rate thus affecting the cooling of water. Also, temperature of air, size and height of tower and velocity of air entering the tower affect the cooling of water.

4. The cooling of water is affected by degree of uniformity in descending water.
a) True
b) False

Explanation: Ideally, degree of uniformity of descending water should be high. Also, air should be accessible to all parts of the tower and there should be proper arrangement of plates for efficient cooling of water.

5. Based on the material, with which the towers are made, cooling towers are classified into _____
a) Timber towers, Concrete towers and Alloy duct type
b) Induced and forced draught type
c) Induced and natural draught type
d) Timber towers, Concrete towers and Steel duct type

Explanation: Cooling towers are classified into timber towers, concrete towers and steel duct type, based on the material with which they are made. Timber towers are rarely used. Concrete towers are widely used owing to their huge capacity.
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6. Which of the following statements about timber towers is False?
a) Timber towers have longer life than concrete and steel duct type towers
b) Timber towers have high maintenance charges
c) Timber towers have limited cooling capacity
d) Timber towers are rarely used

Explanation: Timber towers on exposure to sun, wind, water etc. rot easily, hence, they have shorter life than concrete and steel duct type towers. They have high maintenance charges and limited cooling capacity. Due to the mentioned reasons, they are rarely used.

7. Which of the following statements about concrete towers is FALSE?
a) Concrete towers have large capacity (of the order 5 x 103 m3/h)
b) Longer life than timber towers
c) Concrete towers have good stability under air pressure
d) Concrete towers require frequent maintenance

Explanation: Concrete towers have towers are known are known to have large capacity, sometimes of the order 5 x 103 m3/h. They have a longer life than timber towers and have higher stability under air pressure. They don’t require low maintenance.

8. Which of the following statements about duct type cooling towers is TRUE?
a) They are widely used in modern power plants
b) Their water handling capacity is small
c) On continued exposure to wind, water and sun, they rot
d) They have short life

Explanation: Duct type cooling towers have long life, but small capacity. Owing to the small capacity they are rarely used in the modern power plants. They can operate either on forced, induced or natural draught.

9. Which of the following statements regarding cooling towers is FALSE?
a) Concrete towers have longer life than timber tower
b) Timber towers have high maintenance charges
c) Duct-type cooling towers have small capacity
d) Cooling towers are used to cool down the water being supplied to the boiler of the power plant

Explanation: Cooling towers are used to cool down the water being passed though the condenser. The discharge of cooling towers is collected in the cooling pond and reused as cooling water in the condenser.

10. Which type of cooling tower is shown in the image below?

a) Induced draught cooling tower
b) Forced draught cooling tower
c) natural draught cooling tower
d) Forced or induced depending upon the sense of rotation of fan

Explanation: The given figure represents an induced draught cooling tower. The location of fan in case of induced draught cooling towers is a the top opening of the tower. In case of forced draught, the fan is located at the bottom. Natural draught cooling towers doesn’t have a fan.

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