Refrigeration And Air Conditioning - Study Mode

[#136] For ammonia refrigerating systems, the tubes of a shell and tube condenser are made of
Correct Answer

(C) Steel

Explanation

Solution: For ammonia refrigerating systems, the tubes of a shell and tube condenser are made of steel

[#137] R-12 is generally preferred over R-22 in deep freezers since
Correct Answer

(C) It is miscible with oil over large range of temperatures

Explanation

Solution: R-12 is generally preferred over R-22 in deep freezers since It is miscible with oil over large range of temperatures

[#138] A good refrigerant should have
Correct Answer

(A) High latent heat of vaporisation and low freezing point

Explanation

Solution: - The refrigerant should have low boiling point and low freezing point. - It must have low specific heat and high latent heat. Because high specific heat decreases the refrigerating effect per kg of refrigerant and high latent heat at low temperature increases the refrigerating effect per kg of refrigerant. - It must have high critical pressure and temperature to avoid large power requirements. - It should have low specific volume to reduce the size of the compressor. - It must have high thermal conductivity to reduce the area of heat transfer in evaporator and condenser. - It should be non-flammable, non-explosive, non-toxic and non-corrosive. - It should not have any bad effects on the stored material or food, when any leak develops in the system.

[#139] Pick up the wrong statement. A refrigerant should have
Correct Answer

(B) High boiling point

Explanation

Solution: - The refrigerant should have low boiling point and low freezing point. - It must have low specific heat and high latent heat. Because high specific heat decreases the refrigerating effect per kg of refrigerant and high latent heat at low temperature increases the refrigerating effect per kg of refrigerant. - It must have high critical pressure and temperature to avoid large power requirements. - It should have low specific volume to reduce the size of the compressor. - It must have high thermal conductivity to reduce the area of heat transfer in evaporator and condenser. - It should be non-flammable, non-explosive, non-toxic and non-corrosive. - It should not have any bad effects on the stored material or food, when any leak develops in the system.

[#140] For proper refrigeration in a cabinet, if the temperature and vapour pressure difference between cabinet and atmosphere is high, then
Correct Answer

(C) Perfectly tight vapour seal should be used

Explanation

Solution: For proper refrigeration in a cabinet, if the temperature and vapour pressure difference between cabinet and atmosphere is high, then Perfectly tight vapour seal should be used