1000+ Refrigeration & Air-Conditioning Multiple Choice Question Answer [Solved]

1. The general rule for rating refrigeration systems (excepting for CO? system) is to approximate following h.p. per ton of refrigeration
A. 0.1 to 0.5 h.p. per ton of refrigeration
B. 0.5 to 0.8 h.p. per ton of refrigeration
C. 1 to 2 h.p. per ton of refrigeration
D. 2 to 5 h.p. per ton of refrigeration
Answer : C

2. An important characteristic of absorption system of refrigeration is
A. Noisy operation
B. Quiet operation
C. Cooling below 0°C
D. Very little power consumption
Answer : B

3. Where does the lowest temperature occur in a vapour compression cycle?
A. Condenser
B. Evaporator
C. Compressor
D. Expansion valve
Answer : B

4. In refrigerator, liquid receiver is required between condenser and flow controlling device, if quantity of refrigerant for system is
A. Less than 2 kg
B. More than or equal to 3.65 kg
C. More than 10 kg
D. There is no such consideration
Answer : B

5. Oil separator in a refrigeration cycle is installed
A. Before compressor
B. Between compressor and condenser
C. Between condenser and evaporator
D. Between condenser and expansion valve
Answer : B

6. The alignment circle is marked on the psychrometric chart at
A. 20°C DBT and 50% RH
B. 26°C DBT and 50% RH
C. 20°C DBT and 60% RH
D. 26°C DBT and 60% RH
Answer : B

7. During sensible cooling,
A. Relative humidity remains constant
B. Wet bulb temperature increases
C. Specific humidity increases
D. Partial pressure of vapour remains constant
Answer : D

8. The thermostatic expansion valve is also called
A. Constant pressure valve
B. Constant temperature valve
C. Constant superheat valve
D. None of these
Answer : C

9. The relative coefficient of performance is
A. Actual COP/theoretical COP
B. Theoretical COP/actual COP
C. Actual COP × theoretical COP
D. None of these
Answer : A

10. During heating and humidification, the final relative humidity of air
A. Can be lower or higher than that of the entering air
B. Is lower than that of the entering air
C. Is higher than that of the entering air
D. None of the above
Answer : A

11. Relative humidity is given by (where pv = Partial pressure of water vapour, pb = Barometric pressure, ps = Pressure of saturated air, pd = Pressure at dry bulb temperature, pw = Saturation pressure corresponding to wet bulb temperature, and ? = Degree of saturation)
A. 0.622 Pv / (Pb - Pv)
B. ?/[1 - (1 - ?) (Ps/Pb)]
C. [Pv (Pb - Pd)]/ [Pd (Pb - Pv)]
D. None of these
Answer : B

12. 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
A. Humidity ratio
B. Relative humidity
C. Absolute humidity
D. Degree of saturation
Answer : D

13. The formation of frost on cooling coils in a refrigerator
A. Increases heat transfer
B. Improves C.O.P. of the system
C. Increases power consumption
D. Reduces power consumption
Answer : C

14. During dehumidification process, __________ remains constant.
A. Wet bulb temperature
B. Relative humidity
C. Dry bulb temperature
D. Specific humidity
Answer : C

15. Presence of moisture in a refrigerant affects the working of
A. Compressor
B. Condenser
C. Evaporator
D. Expansion valve
Answer : D

16. The pressure at the inlet of a refrigerant compressor is called
A. Suction pressure
B. Discharge pressure
C. Critical pressure
D. Back pressure
Answer : A

17. One tonne of refrigeration (1TR) means that the heat removing capacity is
A. 21 kJ/min
B. 210 kJ/min
C. 420 kJ/min
D. 620 kJ/min
Answer : B

18. The leakage in a refrigeration system using Freon is detected by
A. Halide torch
B. Sulphur sticks
C. Soap and water
D. All of these
Answer : A

19. During cooling and dehumidification, dry bulb temperature
A. Remains constant
B. Increases
C. Decreases
D. None of these
Answer : C

20. Mass flow ratio of NH? in comparison to Freon12 for same refrigeration load and same temperature limits is of the order of
A. 1 : 1
B. 1 : 9
C. 9 : 1
D. 1 : 3
Answer : B

21. At lower temperatures and pressures, the latent heat of vaporisation of a refrigerant
A. Decreases
B. Increases
C. Remain same
D. Depends on other factors
Answer : B

22. The COP of a vapour compression plant in comparison to vapour absorption plant is
A. More
B. Less
C. Same
D. More/less depending on size of plant
Answer : A

23. One of the purposes of sub cooling the liquid refrigerant is to
A. Reduce compressor overheating
B. Reduce compressor discharge temperature
C. Increase cooling effect
D. Ensure that only liquid and not the vapour enters the expansion (throttling) valve
Answer : D

24. In a lithium bromide absorption refrigeration system
A. Lithium bromide is used as a refrigerant and water as an absorbent
B. Water is used as a refrigerant and lithium bromide as an absorbent
C. Ammonia is used as a refrigerant and lithium bromide as an absorbent
D. None of the above
Answer : B

25. The bypass factor of a cooling coil decreases with
A. Decrease in fin spacing and increase in number of rows
B. Increase in fin spacing and increase in number of rows
C. Increase in fin spacing and decrease in number of rows
D. Decrease in fin spacing and decrease in number of rows
Answer : A

26. In vapour compression cycle the condition of refrigerant is superheated vapour
A. After passing through the condenser
B. Before passing through the condenser
C. After passing through the expansion or throttle valve
D. Before entering the expansion valve
Answer : B

27. 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 a low temperature body
D. None of the above
Answer : A

28. On the pressure-enthalpy diagram, condensation and desuperheating is represented by a horizontal line because the process
A. Involves no change in volume
B. Takes place at constant temperature
C. Takes place at constant entropy
D. Takes place at constant pressure
Answer : D

29. Degree of saturation or percentage humidity is
A. The mass of water vapour present in 1 m³ of dry air
B. The mass of water vapour present in 1 kg of dry air
C. 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.
D. 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
Answer : C

30. In vapour compression cycle, the condition of refrigerant is saturated liquid
A. After passing through the condenser
B. Before passing through the condenser
C. After passing through the expansion throttle valve
D. Before entering the expansion valve
Answer : A

31. A thermostatic expansion valve in a refrigeration system
A. Ensures the evaporator completely filled with refrigerant of the load
B. Is suitable only for constant load systems
C. Maintains different temperatures in evaporator in proportion to load
D. None of the above
Answer : A

32. An evaporator is also known as
A. Freezing coil
B. Cooling coil
C. Chilling coil
D. All of these
Answer : D

33. In vapour compression cycle the condition off refrigerant is dry saturated vapour
A. After passing through the condenser
B. Before passing through the condenser
C. After passing through the expansion or throttle valve
D. Before entering the compressor
Answer : D

34. A bootstrap air cooling system has
A. One heat exchanger
B. Two heat exchangers
C. Three heat exchangers
D. Four heat exchangers
Answer : B

35. In a flooded evaporator refrigerator, an accumulator at suction of compressor is used to
A. Collect liquid refrigerant and prevent it from going to compressor
B. Detect liquid in vapour
C. Superheat the vapour
D. Collect vapours
Answer : A

36. The vertical and uniformly spaced lines on a psychrometric chart indicates
A. Dry bulb temperature
B. Wet bulb temperature
C. Dew point temperature
D. Specific humidity
Answer : A

37. Which of the following statement is correct?
A. The constant enthalpy lines are also constant wet bulb temperature lines.
B. The wet bulb and dry bulb temperature are equal at saturation condition.
C. The wet bulb temperature is a measure of enthalpy of moist air.
D. All of the above
Answer : D

38. The index which correlates the combined effects of air temperature, relative humidity and air velocity on the human body, is known as
A. Mean radiant temperature
B. Effective temperature
C. Dew point temperature
D. None of these
Answer : B

39. While designing the refrigeration system of an aircraft, the prime consideration is that the
A. System has high C.O.P.
B. Power per TR is low
C. Mass of refrigerant circulated in the system is low
D. Mass of the refrigeration equipment is low
Answer : D

40. The refrigerant supplied to a compressor must be
A. Superheated vapour refrigerant
B. Dry saturated liquid refrigerant
C. A mixture of liquid and vapour refrigerant
D. None of these
Answer : A

41. Which of the following refrigerant has the highest freezing point.
A. Ammonia
B. Carbon dioxide
C. Sulphur dioxide
D. R-12
Answer : B

42. In a domestic vapour compression refrigerator, the refrigerant commonly used is
A. CO?
B. Ammonia
C. R-12
D. All of these
Answer : C

43. In Electrolux refrigerator
A. Ammonia is absorbed in hydrogen
B. Ammonia is absorbed in water
C. Ammonia evaporates in hydrogen
D. Hydrogen evaporates in ammonia
Answer : C

44. The lowest thermal diffusivity is of
A. Iron
B. Lead
C. Aluminium
D. Rubber
Answer : D

45. The coefficient of performance of a domestic refrigerator is ________ as compared to a domestic air-conditioner.
A. Same
B. Less
C. More
D. None of these
Answer : B

46. The lower horizontal line of the refrigeration cycle plotted on pressure-enthalpy diagram represents
A. Condensation of the refrigerant vapour
B. Evaporation of the refrigerant liquid
C. Compression of the refrigerant vapour
D. Metering of the refrigerant liquid
Answer : B

47. In vapour compression cycle, the condition of refrigerant is high pressure saturated liquid
A. After passing through the condenser
B. Before passing through the condenser
C. After passing through the expansion or throttle valve
D. Before entering the expansion valve
Answer : D

48. The vapour pressure of refrigerant should be
A. Lower than atmospheric pressure
B. Higher than atmospheric pressure
C. Equal to atmospheric pressure
D. Could be anything
Answer : B

49. Air conditioning means
A. Cooling
B. Heating
C. Dehumidifying
D. All of these
Answer : D

50. Which of the following refrigerant has the lowest boiling point?
A. Ammonia
B. Carbon dioxide
C. Sulphur dioxide
D. R-12
Answer : B