250+ TOP MCQs on Open Air Refrigeration System – 1 and Answers

Refrigeration Multiple Choice Questions on “Open Air Refrigeration System – 1”.

1. Which of the following can be called as a refrigeration process?
a) Cooling of hot ingot from 1000 C to room temperature
b) Cooling of a pot of water by mixing it with a large block of ice
c) Cooling in rooms using a ceiling fan
d) Cooling of hot water by mixing it with tap water
Answer: b
Clarification: Refrigeration is the process of cooling the body with the help of evaporation during the contact with the other external surface, hence when Ice mixes with water, the water in pot will suddenly drop its temperature whereas the Ice will be converted liquid and evaporate (invisibly).

2. What is the main disadvantage of natural refrigeration methods?
a) They are expensive
b) They are poisonous
c) They are not environment friendly
d) They are dependent on local conditions
Answer: d
Clarification: Natural Refrigeration process is dependent on the local conditions like temperature of surrounding, pressure at which it occurs, and volume of the refrigerant etc. hence it cannot be predicted exactly.

3. For what condition, evaporative cooling system is ideal?
a) Hot and Dry
b) Hot and Humid
c) Cold and Humid
d) Moderate Hot but Humid
Answer: a
Clarification: As the humidity increases, it becomes difficult to produce refrigeration effect as there increases the need to set up a de-humidifier too.

4. Compared to natural refrigeration methods, artificial refrigeration methods are________
a) dis-continuous
b) not reliable
c) continuous
d) environment friendly
Answer: c
Clarification: As artificial refrigeration uses various refrigerants like R-12,R-14,R-150 etc. along with CFC it becomes harmful for environment, but it produces a constant cooling whenever required.

5. What is the main function of an expansion valve?
a) Reduce the refrigerant pressure
b) Maintain high and low side pressures
c) Protect evaporator
d) Control the velocity of flow of refrigerants
Answer: b
Clarification: Expansion valve mainly increases or decreases the flow of refrigerants, which directly affects the increase and decrease in the pressures.

6. In a domestic icebox type refrigerator, the ice block is kept at the top because __________
a) it is easy for the user to operate
b) disposal of water is easier
c) hot air can be easily removed from the top
d) cold air can flow down due to buoyancy effect
Answer: d
Clarification: Buoyancy effect acts similar to the gravitational force that occurs on the surface outside, hence the more dense cold air comes to the bottom and the hot air goes at the top, but there is no chance of hot air in the refrigerator.

7. Why are vapour absorption system better than compression system?
a) Uses low grade thermal energy
b) Uses no energy
c) Uses refined petroleum energy to produce least pollution
d) Uses high grade thermal energy
Answer: a
Clarification: It uses low grade of thermal energy, hence it can easily be operated for greater output, and economically.

8. In a triple fluid vapour absorption refrigeration system, why is the hydrogen gas used?
a) Improve system performance
b) Reduce the partial pressure of vapour in the evaporator
c) Calculate the refrigerant
d) Provide the vapour seal
Answer: b
Clarification: Hydrogen gas is lighter and less dense than many of the gases. Hence it is used to reduce the partial pressure in the vapour in the evaporator.

9. Why low temperature refrigeration is produced in an air standard refrigeration system?
a) Evaporation of liquid air
b) Throttling of air
c) Expansion of air in turbine
d) Condensing of air
Answer: c
Clarification: Due to expansion of air in turbines, the pressure in the air decreases and the loss of pressure results in the fall of temperature. Hence low temperature is obtained in air standard refrigeration system.

10. The required input to the steam jet refrigeration systems is in the form of?
a) Mechanical energy
b) Thermal energy
c) High pressure, motive steam
d) Both mechanical and thermal
Answer: c
Clarification: For a Steam jet refrigeration, the velocity at input is an important part to produce the Jet effect. Hence the input pressure must be high enough as possible.