Refrigeration and Air Conditioning important question and answer

Question 1 : 
Heat removing capacity of a one-ton refrigerator is 
Option A: 25 Kcal / sec
Option B: 50 Kcal / min
Option C: 50 Kcal / hour
Option D: 100 Kcal / hour 
Explaination: 50 Kcal/min

Question 2 : 

In SI units, one tonne of refrigeration is equivalent to  
Option A: 1.5 kW
Option B: 2.5 kW

Option C: 3.5 kW
Option D: 5 kW
Explanation: In SI units, one tonne of refrigeration is equivalent to 3.5 kW and 210 kJ/min. 


Question 3 : 

In a refrigeration system, the moisture is removed by 
Option A: Driers
Option B: Desiccants
Option C: Filter driers
Option D: All of the above
Explanation: Moisture is removed by driers, filter driers and desiccants too. 

Question 4 :

Subcooling occurs when the vapour
Option A: Has high latent heat
Option B: Has low latent heat
Option C: Removes sensible heat from the refrigerant
Option D: Has high thermal conductivity
Explanation: Subcooling occurs when the vapour removes sensible heat from the refrigerant.

Question 5: 

In the sensible cooling process, specific humidity
Option A: Increases
Option B: Decreases
Option C: Remain constant
Option D: NONE
Explanation: In a sensible cooling process, specific humidity remains constant and relative humidity increases.  

Question 6: 

The dew point temperature as compared to wet bulb temperature for unsaturated air is
Option A: Equal
Option B: Less
Option C: More 
Option D: Unpredictable
Explanation: DPT is less than WBT for unsaturated air.

Question 7:

Air conditioning means?
Option A: Cooling and Heating
Option B: Removal of air impurities
Option C: Dehumidifying
Option D: All of the above
Explanation: A system for controlling the humidity, ventilation, and temperature in a building or vehicle, typically to maintain a cool atmosphere in warm conditions. 

Question 8: 

The main parts of a vapour compression refrigeration system in a sequence are
Option A: Compressor, Condensor, Evaporator and Throttle valve
Option B: Compressor, Throttle valve, Condensor, and Evaporator
Option C: Compressor, Evaporator, Condensor, and Throttle valve
Option D: Compressor, Condensor, Throttle valve, and Evaporator
Explanation: First compressor then condenser, throttle valve and last evaporator. 

Question 9: 

If a refrigerant is having low specific heat, then co-efficient of performance will be
Option A: Lower
Option B: Higher
Option C: Same
Option D: NONE
Explanation: Higher

Question 10: 

The ratio for sensible heat factor is 
Option A: Latent heat to Sensible heat
Option B: Sensible heat to Latent heat
Option C: Latent heat to Total heat
Option D: Sensible heat to Total heat
Explanation: SHF = Sensible heat / Total Heat 
Sensible heat is the heat which increases or decreases the temperature of the body.

Question 11: 

The subcooling in the refrigeration cycle, 
Option A: Increases COP
Option B: Reduce cooling
Option C: Increases work of compression
Option D: Reduce condenser size
Explanation: The subcooling process increases the COP of the refrigeration cycle. 
The coefficient of performance or COP of a heat pump, refrigerator or air conditioning system is a ratio of useful heating or cooling provided to work required. Higher COPs equate to lower operating costs. 

Question 12: 

The phenomenon of emf developed between two dissimilar metals in contact is which of the following effect
Option A: Seeback effect
Option B: Thomson effect
Option C: Peltier effect
Option D: Thermocouple effect

Explanation: A temperature difference between two dissimilar electrical conductors or semiconductors produces a voltage difference is called as seeback effect. 

Question 13: 

In a refrigeration cycle, the heat is absorbed by a refrigerant in a and heat is rejected by a refrigerant in a
Option A: Evaporator, Condensor 
Option B: Evaporator, Compressor
Option C: Condensor, Evaporator
Option D: Evaporator, Expansion valve 
Explanation: The heat is absorbed by an evaporator and rejected by the condenser. 

Question 14: 

Mass of the water vapour present in 1 kg of dry air is called, 
Option A: Relative humidity
Option B: Absolute humidity
Option C: Humidity ratio
Option D: Percentage humidity
Explanation: Humidity ratio, it is also known as specific humidity. 

Question 15: 

Mass of the water vapour present in 1 mof dry air is called, 
Option A: Relative humidity
Option B: Absolute humidity
Option C: Percentage of humidity
Option D: Humidity ratio
Explanation: Absolute humidity

Question 16: 

Dew point is the temperature at which, 
Option A: Ice starts melting in the presence of air without external aid
Option B: Condensation of water vapour in air starts
Option C: Vapourisation of water vapour in air starts
Option D: NONE
Explanation: The dew point is the temperature to which air must be cooled to become saturated with water vapour. Dew point temperature indicates dryness of the air, moisture content of air, condition of air. 

Question 17:

Dry bulb, wet bulb and dew point temperature are the same for, 
Option A: Dry air
Option B: Saturated air
Option C: Wet air
Option D: NONE
Explanation: Saturated air 


Question 18: 

The difference between the dry bulb and wet bulb temperature is called
Option A: Dry bulb temperature
Option B: Wet-bulb temperature
Option C: Dew point temperature
Option D: NONE
Explanation: WBT = DBT - WBT 

Question 19: 

The moisture content of air is indicated by, 
Option A: Dry bulb temperature
Option B: Wet-bulb temperature
Option C: Dew point temperature
Option D: Both A and B
Explanation: Moisture content of air is indicated by the dry bulb and wet bulb temperature. 

Question 20: 

If wet-bulb depression is zero, it indicates
Option A: Relative humidity is zero
Option B: Relative humidity is 100%
Option C: Rain is likely to occur
Option D: NONE
Explanation: If the wet-bulb depression is zero relative humidity is 100% as wet-bulb depression indicates relative humidity. 

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