Multiple choice questions (MCQ) on Refrigeration and air conditioning

1. A refrigeration system

a. Removes heat from a low temperature body and delivers it to a high temperature body

b. Removes heat from a high temperature body and delivers it to a low temperature body

c. Rejects energy to low temperature body

d. None of the above


2. The capacity of domestic refrigerator is in the range of

a. 0.1 to 0.3 TR             b. 0 to 3 TR                   c. 3 to 5 TR       d. None of the above


3. In a boot strap air evaporation takes place

a. Between the second heat exchanger and the cooling turbine

b. Between the combustion chamber and the first heat exchanger

c. Between the first heat exchanger and the secondary compressor

d. None of the above


4. In a vapour compression system the condition of refrigerant before passing through the condenser is

a. Superheated vapour              b. Wet vapour

c. Saturated liquid                     d. None of the above


5. The oil separator in a refrigeration cycle is installed

a. Before compressor                                        b. Between compressor and condenser

c. Between condenser and evaporator                c. None of the above


6. In a lithium bromide absorption refrigeration system

a. Lithium bromide is used as a refrigerant and water as absorbent

b. Water is used as a refrigerant and lithium bromide as absorbent

c. Ammonia is used as a refrigerant and lithium bromide as absorbent

d. None of the above


7. The desirable property of a refrigerant is

a. Low boiling point                                           b. High critical temperature

c. High latent heat of vaporization                      d. All of the above


8. A mixture of dry air and water vapour, when the air has diffused the maximum amount of water vapour into it, is called

a. Dry air           b. Moist air       c. Saturated air              d. None of the above


9. During humidification process, dry bulb temperature

a. Remains constant                  b. Increases

c. Decreases                             d. None of the above


10. The function of air conditioning system is

a. Cooling and humidification                 b. Cooling and dehumidification

c. Heating and humidification                 d. Heating and dehumidification


11. The difference between the comfort air conditioning and industrial lies in the

a. equipment cost                                 b. process adopted

c. indoor requirements                           d. ambient conditions


12. The pipes and fitting in an ammonia refrigeration system should be made of

a. cast steel or wrought iron                   b. aluminium

c. naval brass                                       d. copper


13. An automatic expansion valve is required to maintain constant

a. pressure in the evaporator                   b. temperature in the freezer

c. pressure in the liquid line                    d. temperature in the condenser


14. In summer air conditioning, the conditioned air passing through the space undergoes a process of

a. sensible cooling                     b. cooling and dehumidification

c. sensible heating                    d. heating and humidification


15. A sample of moist air is at a temperature T and relative humidity 50%. A part of the moisture is removed adiabatically by using an absorbent. If the heat of absorption is negligible, the resulting air will have the same

a. dry bulb temperature but a lower wet bulb temperature

b. wet bulb temperature but a higher dry bulb temperature

c. dry bulb temperature but a higher wet bulb temperature

d. wet bulb temperature but a lower dry bulb temperature


16. Use of hermetically sealed compressor in a vapour compression refrigeration system results in

a. decrease in energy consumption                      b. increase in energy consumption

c. increase in COP                                             d. increase in pressure ratio


17. Excessive pressure drop in liquid line in a refrigerating system causes

a. high condenser                                  b. flashing of the liquid refrigerant

c. higher evaporator pressure                  d. under cooling of the liquid refrigerant


18. Dry compression in reciprocating compressor is preferred because it

1. prevent valve damage

2. enables use of thermostatic expansion valve

3. minimizes irreversibilities in the compressor

4. prevents washing out of the lubricating oil from cylinder walls

Of these statements:

a. 1 and 2 are correct                 b. 2 and 3 are correct

c. 1 and 4 are correct                 d. 3 and 4 are correct


19. If a sample of moist air of 50% humidity at atmospheric pressure is isothermally compressed to a pressure of two atmospheres, then

a. its relative humidity will reduce to 25%            b. its relative humidity will remain unchanged

c. the sample of air will become saturated           d. saturation pressure will increase to twice the value


20. Evaporative regulation of body temperature fails when the body temperature is

a. more than wet bulb temperature but less than dry bulb temperature

b. more than dew point but less than wet bulb temperature

c. more than dew point but less than dry bulb temperature

d. less than dew point