Refrigeration And Air Conditioning MCQ Questions & Answers | Mechanical Engineering

- The human body can lose heat even if its temperature is less than the atmospheric temperature.
- The increase in air movement increases the evaporation from the human body.

- In vapour absorption refrigerator, the compression of refrigerant is avoided.
- Sub-cooling can be achieved by circulating more quantity of cooling water through the condenser.
- In vapour compression refrigeration, the vapour is drawn in the compressor cylinder during its suction stroke and is compressed adiabatically during the compression stroke.

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

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

- 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.

- 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.

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

The ratio of actual mass of water vapour in a given volume of moist air to the mass of water vapour in the same volume of saturated air at the same temperature and pressure, is called Relative humidity

The ratio of the actual mass of water vapour in a unit mass of dry air to the mass of water vapour in the same mass of dry air when it is saturated at the same temperature and pressure, is called Degree of saturation

The capillary tube, as an expansion device, is used in
- Domestic refrigerators
- Water coolers
- Room air conditioners