250+ TOP MCQs on Single and Multiple Effect Evaporators and Answers

Food Processing Unit Operations Multiple Choice Questions on “Single and Multiple Effect Evaporators”.

1. What are the three functional sections present in evaporator?
a) Heat exchanger, evaporating section
b) Heat exchanger, separator
c) Separator, evaporating section
d) Heat exchanger, evaporating section, separator
Answer: d
Clarification: The evaporator is made up of three functional sections. They are the heat exchanger, the evaporating section, where the liquid boils and evaporates, and the separator in which the vapour leaves the liquid and passes off to the condenser or to other equipment.

2. What are the advantages of multiple effect evaporators over single effect evaporator?
a) Suitable for large scale operation
b) Suitable for continuous operation
c) Maximize the energy input required for evaporating
d) Suitable for large scale and for continuous operation
Answer: d
Clarification: Advantages of multiple effect evaporators are suitable for large scale and for continuous operation. It is highly economical when compared to single effect. Multiple effects are used to minimize the energy input required to evaporate undesirable water content.

3. Who invented the multiple-effect evaporator?
a) Norbert Rillieux
b) Justus von Liebig
c) Nils Wallerius
d) Rudolf Clausius
Answer: a
Clarification: Norbert Rillieux invented multiple-effect evaporator. Justus von Liebig invented water cooled condenser. Nils Wallerius discovered evaporation. Rudolf Clausius invented the term entropy.

4. Are these statements about the feeding mechanism of evaporatortrue?
Statement 1: In forward feed, the most concentrated liquids will occur in the last effect.
Statement 2: In forward feed, the liquid is pumped from one effect to the next against the pressure drops.
a) True, False
b) True, True
c) False, True
d) False, False
Answer: a
Clarification: In forward feed, the most concentrated liquids will occur in the last effect. The liquid feed progress is simple as it passes from effect one to otherand therefore it does not require pumping for the feed to flow. But in backward feed, the liquid is pumped from one effect to the next against the pressure drops.

5. Who discovered evaporation?
a) Norbert Rillieux
b) Justus von Liebig
c) Nils Wallerius
d) Rudolf Clausius
Answer: c
Clarification: Norbert Rillieux invented multiple-effect evaporator. Justus von Liebig invented water cooled condenser. Nils Wallerius discovered evaporation. Rudolf Clausius invented the term entropy.

6. What is the steam economy of single effect evaporator?
a) 0.8
b) 1.3
c) 10
d) 5.6
Answer: a
Clarification: Steam economy of the evaporator is defined as the number kilogram of water vaporized from all the effects per kilogram of steam used. The steam economy of single effect evaporator is about 0.8 (<1).

7. What are the different modes of feed in multiple effect evaporators?
a) Forward feed arrangement
b) Backward feed arrangement
c) Forward feed arrangement and backward feed arrangement
d) Perpendicular feed arrangement
Answer: c
Clarification: The different modes of feed in multiple effect evaporators are forward feed arrangement, backward feed arrangement, mixed feed and parallel feed arrangement.

8. Where is the feed introduced in climbing film evaporator?
a) Bottom
b) Top
c) Middle
d) Anywhere
Answer: a
Clarification: The climbing film plate evaporator is designed to produce a thin film. In the climbing film evaporators, the feed is introduced at the bottom of the tubes and thus vapor due to evaporation expands which results in rise of the liquid along the tubes.

9. How to increase the economy of multi effect evaporator?
a) Decrease the usage of steam
b) Increase the steam capacity
c) Reuse the latent heat of the water vapor
d) Reuse the latent heat of the liquid feed
Answer: a
Clarification: Reuse the latent heat of the water vapor to increase the economy of multi effect evaporator.This type of evaporator uses the water vapor from one effect as the heating medium for the next effect, which operates at a lower boiling point.

10. Is evaporation and boiling the same?
a) True
b) False
Answer: b
Clarification: There are two types of vaporization 1.Evaporation and 2.Boiling. Evaporation is defined as surface of a body of liquid turning into gas. Boiling refers to heating up a liquid until it releases vapor.