1000+ Refrigeration & Air-Conditioning MCQ for CAT [Solved]

1. During a refrigeration cycle, heat is rejected by the refrigerant in a
A. Compressor
B. Condenser
C. Evaporator
D. Expansion valve
Answer : B

2. A valve which maintains a constant degree of superheat at the end of the evaporator coil, is called
A. Automatic expansion valve
B. High side float valve
C. Thermostatic expansion valve
D. Low side float valve
Answer : D

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

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

5. Pick up the correct statement about giving up of heat from one medium to other in ammonia absorption system
A. Strong solution to weak solution
B. Weak solution to strong solution
C. Strong solution to ammonia vapour
D. Ammonia vapours to weak solution
Answer : B

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

7. 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

8. In aqua ammonia absorption refrigeration system, incomplete rectification leads to accumulation of water in
A. Condenser
B. Evaporator
C. Absorber
D. None of these
Answer : A

9. 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

10. A good refrigerant should have
A. High latent heat of vaporisation and low freezing point
B. High operating pressures and low freezing point
C. High specific volume and high latent heat of vaporisation
D. Low C.O.P. and low freezing point
Answer : A

11. Chaperon equation is applicable for registration at
A. Saturation point of vapour
B. Saturation point of liquid
C. Sublimation temperature
D. Triple point
Answer : A

12. 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

13. In a vapour compression system, the condition of refrigerant before entering the expansion or throttle valve is
A. High pressure saturated liquid
B. Wet vapour
C. Very wet vapour
D. Dry vapour
Answer : A

14. Ammonia absorption refrigeration cycle requires
A. Very little work input
B. Maximum work input
C. Nearly same work input as for vapour compression cycle
D. Zero work input
Answer : A

15. 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

16. In a pressure enthalpy chart, the space to the left of the saturated liquid line represents
A. Wet vapour region
B. Superheated vapour region
C. Sub-cooled liquid region
D. None of these
Answer : C

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

18. The condition of refrigerant after passing through the condenser in a vapour compression system is
A. Saturated liquid
B. Wet vapour
C. Dry saturated vapour
D. Superheated vapour
Answer : A

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 C.O.P. of a Carnot refrigerator in winter will be _________ as compared to C.O.P. in summer.
A. Same
B. Lower
C. Higher
D. None of these
Answer : C

21. The lowest temperature during the cycle in a vapour compression system occurs after
A. Compression
B. Expansion
C. Condensation
D. Evaporation
Answer : D

22. During adiabatic saturation process on unsaturated air __________ remains constant.
A. Relative humidity
B. Dew point temperature
C. Dry bulb temperature
D. Wet bulb temperature
Answer : D

23. The comfort conditions in air conditioning are at (where DBT = Dry bulb temperature, and RH = Relative humidity)
A. 25°C DBT and 100% RH
B. 20°C DBT and 80% RH
C. 22°C DBT and 60% RH
D. 25°C DBT and 40% RH
Answer : C

24. The evaporator used in household refrigerators is
A. Frosting evaporator
B. Non-frosting evaporator
C. Defrosting evaporator
D. None of these
Answer : A

25. Hydrogen is used in Electrolux refrigeration system so as to _________ the rate of evaporation of the liquid ammonia passing through the evaporator.
A. Equalise
B. Reduce
C. Increase
D. None of these
Answer : C

26. 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

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

28. 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

29. 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

30. The wet bulb depression indicates _________ humidity of the air.
A. Absolute
B. Relative
C. Specific
D. None of these
Answer : B

31. During humidification process, dry bulb temperature
A. Remains constant
B. Increases
C. Decreases
D. None of these
Answer : A

32. A refrigeration cycle operates between condenser temperature of + 27°C and evaporator temperature of -23°C. The Carnot coefficient of performance of cycle will be
A. 0.2
B. 1.2
C. 5
D. 6
Answer : C

33. 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

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. 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

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

37. Wet bulb temperature is the temperature of air recorded by a thermometer, when
A. It is not affected by the moisture present in the air
B. Its bulb is surrounded by a wet cloth exposed to the air
C. The moisture present in it begins to condense
D. None of the above
Answer : B

38. 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

39. When the lower temperature of a refrigerating machine is fixed, then the coefficient of performance can be improved by
A. Operating the machine at higher speeds
B. Operating the machine at lower speeds
C. Raising the higher temperature
D. Lowering the higher temperature
Answer : D

40. Under cooling in a refrigeration cycle
A. Increases C.O.P
B. Decreases C.O.P
C. C.O.P remains unaltered
D. Other factors decide C.O.P
Answer : A

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

42. Efficiency of a Carnot engine is given as 80%. If the cycle direction be reversed, what will be the value of COP of reversed Carnot Cycle?
A. 1.25
B. 0.8
C. 0.5
D. 0.25
Answer : D

43. The sensible heat factor during the heating and humidification process is given by (where h? = Enthalpy of air entering the heating coil, h? = Enthalpy of air leaving the heating coil, and hA = Enthalpy of air at the end of humidification process)
A. (hA - h2)/ (h1 - h2)
B. (h2 - hA)/ (h1 - h2)
C. (h1 - h2)/ (hA - h2)
D. (hA - h1)/ (h2 - h1)
Answer : D

44. 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

45. 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

46. In a refrigeration system, the expansion device is connected between the
A. Compressor and condenser
B. Condenser and receiver
C. Receiver and evaporator
D. Evaporator and compressor
Answer : C

47. Which of the following refrigerants has lowest freezing point?
A. Freon-12
B. NH3
C. CO2
D. Freon-22
Answer : D

48. In a bootstrap air evaporative cooling system, the evaporator is provided
A. Between the combustion chamber and the first heat exchanger
B. Between the first heat exchanger and the secondary compressor
C. Between the secondary compressor and the second heat exchanger
D. Between the second heat exchanger and the cooling turbine
Answer : D

49. 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

50. In a psychrometric process, the sensible heat added is 30 kJ/s and the latent heat added is 20 kJ/s. The sensible heat factor for the process will be
A. 0.3
B. 0.6
C. 0.67
D. 1.5
Answer : B