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

1. In a refrigeration cycle, the flow of refrigerant is controlled by
A. Compressor
B. Condenser
C. Evaporator
D. Expansion valve
Answer : D

2. Which of the following cycles uses air as the refrigerant?
A. Ericson
B. Stirling
C. Carnot
D. Bell Coleman
Answer : D

3. 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

4. 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

5. In a reversed Brayton cycle, the heat is absorbed by the air during
A. Isentropic compression process
B. Constant pressure cooling process
C. Isentropic expansion process
D. Constant pressure expansion process
Answer : D

6. The humidity ratio or specific humidity is the mass of water vapour present in
A. 1 m3 of wet air
B. 1 m3 of dry air
C. 1 kg of wet air
D. 1 kg of dry air
Answer : D

7. In a vapour compression system, the condition of refrigerant is dry saturated vapour
A. Before entering the compressor
B. After leaving the compressor
C. Before entering the condenser
D. After leaving the condenser
Answer : A

8. The boiling point of ammonia is
A. -10.5°C
B. -30°C
C. -33.3°C
D. -77.7°C
Answer : C

9. The bypass factor (B. P. F.) in case of sensible heating of air is (Where td? = Dry bulb temperature of air entering the heating coil, td? = Dry bulb temperature of air leaving the heating coil, and td? = Dry bulb temperature of heating coil)
A. (td? - td?)/(td? - td?)
B. (td? - td?)/(td? - td?)
C. (td? - td?)/(td? - td?)
D. (td? - td?)/(td? - td?)
Answer : B

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

12. Highest temperature encountered in refrigeration cycle should be
A. Near critical temperature of refrigerant
B. Above critical temperature
C. At critical Temperature
D. Much below critical temperature
Answer : D

13. 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

14. A refrigerant compressor is used to
A. Raise the pressure of the refrigerant
B. Raise the temperature of the refrigerant
C. Circulate the refrigerant through the refrigerating system
D. All of the above
Answer : D

15. The thermostatic expansion valve operates on the changes in the
A. Degree of superheat at exit from the evaporator
B. Temperature of the evaporator
C. Pressure in the evaporator
D. None of the above
Answer : A

16. The advantage of dry compression is that
A. It permits higher speeds to be used
B. It permits complete evaporation in the evaporator
C. It results in high volumetric and mechanical efficiency
D. All of the above
Answer : D

17. The ratio of heat extracted in the refrigerator to the work-done on the refrigerant is called
A. Coefficient of performance of refrigeration
B. Coefficient of performance of heat pump
C. Relative coefficient of performance
D. Refrigerating efficiency
Answer : A

18. The C.O.P. of an absorption type refrigerator is given by (where T? = Temperature at which the working substance receives heat, T? = Temperature of cooling water, and T? = Evaporator temperature)
A. [T? (T? - T?)] / [T? (T? - T?)]
B. [T? (T? - T?)]/ [T? (T? - T?)]
C. [T? (T? - T?)] / [T? (T? - T?)]
D. [T? (T? - T?)] / [T? (T? - T?)]
Answer : B

19. The freezing point of sulphur dioxide is
A. -56.6°C
B. -75.2°C
C. -77.7°C
D. -135.8°C
Answer : B

20. 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

21. Which of the following statement is correct?
A. The human body can lose heat even if its temperature is less than the atmospheric temperature.
B. The increase in air movement increases the evaporation from the human body.
C. The warm air increases the rate of radiation of heat from the human body.
D. Both (A) and (B)
Answer : D

22. The relative humidity is defined as
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 : D

23. Absorption system normally uses the following refrigerant
A. Freon-11
B. Freon-22
C. CO2
D. Ammonia
Answer : D

24. The specific humidity during cooling and dehumidification
A. Remains constant
B. Increases
C. Decreases
D. None of these
Answer : C

25. The wet bulb temperature during sensible cooling of air
A. Remains constant
B. Increases
C. Decreases
D. None of these
Answer : C

26. In a refrigeration system, heat absorbed in comparison to heat rejected is
A. More
B. Less
C. Same
D. More for small capacity and less for high capacity
Answer : B

27. One ton of refrigeration is equal to the refrigeration effect corresponding to melting of 1000 kg of ice
A. In 1 hour
B. In 1 minute
C. In 24 hours
D. In 12 hours
Answer : C

28. The refrigerant widely used in domestic refrigerators is
A. Ammonia
B. Carbon dioxide
C. Sulphur dioxide
D. R-12
Answer : D

29. The boiling point of ________ is 10.5°C.
A. Ammonia
B. R-12
C. Sulphur dioxide
D. Carbon dioxide
Answer : C

30. In a refrigerating machine, heat rejected is _________ heat absorbed.
A. Equal to
B. Less than
C. Greater than
D. None of these
Answer : C

31. The dry bulb temperature during sensible heating of air
A. Remains constant
B. Increases
C. Decreases
D. None of these
Answer : B

32. The humidification process, on the psychrometric chart is shown by
A. Horizontal line
B. Vertical line
C. Inclined line
D. Curved line
Answer : B

33. One ton refrigeration corresponds to
A. 50 kcal/ min
B. 50 kcal/ hr
C. 80 kcal/ min
D. 80 kcal/ hr
Answer : A

34. The operating pressure for refrigerating units using R-12 as a refrigerant is
A. 2 bar
B. 8 bar
C. 15 bar
D. 30 bar
Answer : B

35. 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

36. The material of pipe lines for a system using Freon as a refrigerant should be
A. Brass
B. Copper
C. Steel
D. Aluminium
Answer : B

37. The optimum effective temperature for human comfort is
A. Higher in winter than in summer
B. Lower in winter than in summer
C. Same in winter and summer
D. Not dependent on season
Answer : B

38. The difference between dry bulb temperature and wet bulb temperature, is called
A. Dry bulb depression
B. Wet bulb depression
C. Dew point depression
D. Degree of saturation
Answer : B

39. In aqua ammonia and Lithium bromide water absorption refrigeration systems, the refrigerants are respectively
A. Water and water
B. Water and lithium bromide
C. Ammonia and lithium bromide
D. Ammonia and water
Answer : D

40. During dehumidification process, the relative humidity
A. Remains constant
B. Increases
C. Decreases
D. None of these
Answer : C

41. A condenser of refrigeration system rejects heat at the rate of 120 kW, while its compressor consumes a power of 30 kW. The coefficient of performance of the system will be
A. 1/4
B. 1/3
C. 3
D. 4
Answer : D

42. The operating temperature of a cold storage is 2°C. The heat leakage from the surrounding is 30 kW for the ambient temperature of 40°C. The actual C.O.P. of refrigeration plant used is one fourth that of ideal plant working between the same temperatures. The power required to drive the plant is
A. 1.86 kW
B. 3.72 kW
C. 7.44 kW
D. 18.6 kW
Answer : D

43. 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

44. R-12 is generally preferred over R-22 in deep freezers since
A. It has low operating pressures
B. It gives higher coefficient of performance
C. It is miscible with oil over large range of temperatures
D. All of the above
Answer : C

45. 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

46. The wet bulb depression is zero when relative humidity is
A. Zero
B. 0.5
C. 0.75
D. 1.0
Answer : D

47. The specific humidity during dehumidification process
A. Remains constant
B. Increases
C. Decreases
D. None of these
Answer : C

48. The bypass factor, in case of sensible cooling of air, is given by (where td? = Dry bulb temperature of air entering the cooling coil, td? = Dry bulb temperature of air leaving the cooling coil, and td? = Dry bulb temperature of the cooling coil)
A. (td? -td?)/( td? -td?)
B. (td? -td?)/( td? -td?)
C. (td? -td?)/( td? -td?)
D. (td? -td?)/( td? -td?)
Answer : B

49. 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

50. Aqua ammonia is used as refrigerant in the following type of refrigeration system
A. Compression
B. Direct
C. Indirect
D. Absorption
Answer : D