Refrigeration & Air-Conditioning MCQ Solved Paper for XAT

1. Air refrigeration cycle is used in
A. Domestic refrigerators
B. Commercial refrigerators
C. Air conditioning
D. Gas liquefaction
Answer : D

2. Which of the following statement is correct?
A. In vapour absorption refrigerator, the compression of refrigerant is avoided.
B. Sub-cooling can be achieved by circulating more quantity of cooling water through the condenser.
C. In vapour compression refrigeration, the vapour is drawn in the compressor cylinder during its suction stroke and is compressed adiabatically during the compression stroke.
D. All of the above
Answer : D

3. The bank of tubes at the back of domestic refrigerator is
A. Condenser tubes
B. Evaporator tubes
C. Refrigerant cooling tubes
D. Capillary tubes
Answer : A

4. In order to cool and dehumidify a stream of moist air, it must be passed over the coil at a temperature
A. Which lies between the dry bulb and wet bulb temperatures of the incoming stream
B. Which lies between the wet bulb and dew point temperatures of the incoming stream
C. Which is lower than the dew point temperature of the incoming stream
D. Of adiabatic saturation of incoming stream
Answer : C

5. 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

6. 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

7. The temperature of ammonia after compression in a vapour compression system is
A. 20 to 50°C
B. 50 to 70°C
C. 70 to 110°C
D. None of these
Answer : C

8. 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

9. Reducing suction pressure in refrigeration cycle
A. Lowers evaporation temperature
B. Increases power required per ton of refrigeration
C. Lowers compressor capacity because vapour is lighter
D. All of the above
Answer : D

10. 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

11. During sensible heating of air _________ decreases.
A. Wet bulb temperature
B. Relative humidity
C. Dry bulb temperature
D. Specific humidity
Answer : B

12. The conditioned air supplied to the room must have the capacity to take up
A. Room sensible heat load only
B. Room latent heat load only
C. Both room sensible heat and latent heat loads
D. None of the above
Answer : C

13. In a vapour absorption refrigeration system, the compressor of the vapour compression system is replaced by
A. Liquid pump
B. Generator
C. Absorber and generator
D. Absorber, generator and liquid pump
Answer : D

14. For better C.O.P of refrigerator, the pressure range corresponding to temperature in evaporator and condenser must be
A. Small
B. High
C. Equal
D. Anything
Answer : A

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

16. The coefficient of performance (C.O.P.) of a refrigerator working as a heat pump is given by
A. (C.O.P.)_P = (C.O.P.)_R + 2
B. (C.O.P.)_P = (C.O.P.)_R + 1
C. (C.O.P)_P = (C.O.P)_R - 1
D. (C.O.P)_P = (C.O.P)_R
Answer : B

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

18. 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

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

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

21. Air refrigerator works on
A. Reversed Carnot cycle
B. Bell Coleman cycle
C. Both (A) and (B)
D. None of these
Answer : C

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

23. 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

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

25. In a saturated air-water vapour mixture, the
A. Dry bulb temperature is higher than wet bulb temperature
B. Dew point temperature is lower than wet bulb temperature
C. Dry bulb, wet bulb and dew point temperature are same
D. Dry bulb temperature is higher than dew point temperature
Answer : C

26. The process, generally used in winter air-conditioning to warm and humidity the air, is called
A. Humidification
B. Dehumidification
C. Heating and humidification
D. Cooling and dehumidification
Answer : C

27. 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

28. Moisture in Freon refrigeration system causes
A. Ineffective refrigeration
B. High power consumption
C. Freezing automatic regulating valve
D. Corrosion of whole system
Answer : C

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

30. 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

31. A refrigerating system operating on reversed Brayton refrigeration cycle is used for maintaining 250 K. If the temperature at the end of constant pressure cooling is 300K and rise in the temperature of air in the refrigerator is 50 K, then the net work of compression will be (assume air as working substance with Cp = 1 kJ/kg)
A. 25 kJ/kg
B. 50 kJ/kg
C. 100 kJ/kg
D. 125 kJ/kg
Answer : B

32. 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

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

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

35. Choose the correct statement
A. A refrigerant should have low latent heat
B. If operating temperature of system is low, then refrigerant with low boiling point should be used
C. Pre-cooling and sub-cooling bf refrigerant are same
D. Superheat and sensible heat of a refrigerant are same
Answer : B

36. 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

37. The heat rejection factor (HRF) is given by
A. 1 + C.O.P
B. 1 - C.O.P.
C. 1 + (1/C.O.P)
D. 1 - (1/C.O.P)
Answer : C

38. In a spray washing system, if the temperature of water is higher than the dry bulb temperature of entering air, then the air is
A. Heated and dehumidified
B. Heated and humidified
C. Cooled and humidified
D. Cooled and dehumidified
Answer : B

39. 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

40. 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

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

42. In vapour compression refrigeration system, refrigerant occurs as liquid between
A. Condenser and expansion valve
B. Compressor and evaporator
C. Expansion valve and evaporator
D. Compressor and condenser
Answer : C

43. 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

44. One ton of the refrigeration is
A. The standard unit used in refrigeration problems
B. The cooling effect produced by melting 1 ton of ice
C. The refrigeration effect to freeze 1 ton of water at 0°C into ice at 0°C in 24 hours
D. The refrigeration effect to produce 1 ton of ice at NTP conditions
Answer : C

45. Which of the following is not a desirable property of a refrigerant?
A. High risibility with oil
B. Low boiling point
C. Good electrical conductor
D. Large latent heat
Answer : C

46. The superheating in a refrigeration cycle
A. Does not alter C.O.P.
B. Increases C.O.P.
C. Decreases C.O.P.
D. None of these
Answer : C

47. In which of the following refrigeration system, waste heat can be effectively used?
A. Vapour compression cycle
B. Vapour absorption cycle
C. Air refrigeration cycle
D. None of these
Answer : B

48. In mechanical refrigeration system, the refrigerant has the maximum temperature
A. In evaporator
B. Before expansion valve
C. Between compressor and condenser
D. Between condenser and evaporator
Answer : C

49. The reduced ambient air cooling system has
A. One cooling turbine and one heat exchanger
B. One cooling turbine and two heat exchangers
C. Two cooling turbines and one heat exchanger
D. Two cooling turbines and two heat exchangers
Answer : C

50. 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