Mass Transfer

531.Unit operation involved in the prilling of urea is

  1. Evaporation
  2. Drying
  3. Crystallisation
  4. Both (B) and (C)

Correct answer: (D)
Both (B) and (C)

532.Unsaturated air (with dry and wet bulb temperatures being 35 and 25°C respectively) is passed through water spray chamber maintained at 35°C. The air will be

  1. Cooled
  2. Humidified
  3. Both (A) & (B)
  4. Dehumidified

Correct answer: (B)
Humidified

533.Unsaturated air (with dry bulb and wet bulb temperatures being 45°C and 25°C respectively) is passed through a water spray chamber maintained at 23°C. The air will be cooled and

  1. Humidified with wet bulb temperature decreasing
  2. Humidified at constant wet bulb temperature
  3. Dehumidified
  4. None of these

Correct answer: (A)
Humidified with wet bulb temperature decreasing

534.Unsaturated air (with dry bulb temperature and dew point being 35°C and 18°C respectively) is passed through a water spray chamber maintained at 15°C. The air will be cooled

  1. And humidified
  2. And dehumidified with increase in wet bulb temperature
  3. At the same relative humidity
  4. And dehumidified with decrease in wet bulb temperature

Correct answer: (D)
And dehumidified with decrease in wet bulb temperature

535.Use of natural draft cooling tower is practised, when the air has low

  1. Humidity
  2. Temperature
  3. Both 'a' & 'b'
  4. Neither 'a' nor 'b'

Correct answer: (C)
Both 'a' & 'b'

536.Use of packed towers for distillation is generally limited to the

  1. Small sizes
  2. Multi-component distillation
  3. High pressure operation
  4. Vacuum distillation

Correct answer: (A)
Small sizes

537.Use of raschig rings in place of crushed stones as packing in packed beds (other things being same)

  1. Increases pressure drop, increases surface area
  2. Increases pressure drop, decreases surface area
  3. Decreases pressure drop, increases surface area
  4. Decreases pressure drop, decreases surface area

Correct answer: (C)
Decreases pressure drop, increases surface area

538.Very tall packed towers are divided into series of beds to

  1. Reduce the overall pressure drop
  2. Avoid channelling
  3. Reduce liquid hold-up
  4. Avoid flooding

Correct answer: (B)
Avoid channelling

539.Water entrained by circulating air in cooling towers is termed as

  1. Drift
  2. Blow down
  3. Vapor load
  4. None of these

Correct answer: (A)
Drift

540.Water-ethyl alcohol solution can be concentrated (in respect of alcohol concentration) by _________ distillation.

  1. Atmospheric
  2. Vacuum
  3. High pressure
  4. None of these

Correct answer: (B)
Vacuum

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