Refrigeration & Air-Conditioning 1000+ MCQ with answer for SSC CPO

1. The desirable property of a refrigerant is
A. Low boiling point
B. High critical temperature
C. High latent heat of vaporisation
D. All of these
Answer : D

2. 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

3. 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

4. A Bell Coleman refrigerator working on dense air system as compared to open air system, for the same range of temperature, results in ________ power per tonne of refrigeration.
A. Same
B. Lower
C. Higher
D. None of these
Answer : B

5. 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

6. The condition of refrigerant as it leaves the compressor in a vapour compression system is
A. Saturated liquid
B. Wet vapour
C. Dry saturated vapour
D. Superheated vapour
Answer : D

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

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

9. 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

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

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

12. 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

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

14. The relative humidity lines on a psychrometric chart are
A. Vertical and uniformly spaced
B. Horizontal and uniformly spaced
C. Horizontal and non-uniformly spaced
D. Curved lines
Answer : D

15. In case of sensible heating of air, the coil efficiency is given by (where B.P.F. = Bypass factor)
A. B.P.F. - 1
B. 1 - B. P.F.
C. 1/ B.P.F.
D. 1 + B.P.F.
Answer : B

16. Domestic refrigerator working on vapour compression cycle uses the following type of expansion device
A. Electrically operated throttling valve
B. Manually operated valve
C. Thermostatic valve
D. Capillary tube
Answer : D

17. 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

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

19. 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

20. For obtaining high COP, the pressure range of compressor should be
A. High
B. Low
C. Optimum
D. Any value
Answer : B

21. In order to collect liquid refrigerant and to prevent it from going to a ________, a device known as accumulator is used at the suction of compressor.
A. Compressor
B. Condenser
C. Expansion valve
D. Evaporator
Answer : A

22. 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

23. 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

24. 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

25. As relative humidity decreases, the dew point temperature will be ________ wet bulb temperature.
A. Same as
B. Lower than
C. Higher than
D. None of these
Answer : B

26. 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

27. A one tonne refrigerating machine means that
A. One tonne is the total mass of machine
B. One tonne refrigerant is used
C. One tonne of water can be converted into ice
D. One tonne of ice when melts from and at 0° C in 24 hours, the refrigeration effect is equivalent to 210 kJ/min
Answer : D

28. During sensible cooling of air ________ decreases.
A. Wet bulb temperature
B. Relative humidity
C. Dry bulb temperature
D. Specific humidity
Answer : C

29. The sub-cooling 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 : B

30. The dry bulb temperature lines, on the psychrometric chart are
A. Vertical and uniformly spaced
B. Horizontal and uniformly spaced
C. Horizontal and non-uniformly spaced
D. Curved lines
Answer : A

31. It is desired to condition the outside air from 70% relative humidity and 45° C dry bulb temperature to 50% relative humidity and 25° C dry bulb temperature (room condition). The practical arrangement will be
A. Dehumidification
B. Cooling and humidification
C. Cooling and dehumidification
D. Dehumidification and pure sensible cooling
Answer : C

32. If a heat pump cycle operates between the condenser temperature of +27°C and evaporator temperature of -23°C, then the Carnot COP will be
A. 0.2
B. 1.2
C. 5
D. 6
Answer : D

33. During humidification process, __________ increases.
A. Wet bulb temperature
B. Relative humidity
C. Dry bulb temperature
D. Specific humidity
Answer : B

34. The boiling point of carbon dioxide is
A. -20.5°C
B. -50°C
C. -63.3°C
D. -78.3°C
Answer : D

35. A vapour absorption refrigerator uses __________ as a refrigerant.
A. Water
B. Ammonia
C. Freon
D. Aqua-ammonia
Answer : D

36. Bell Coleman cycle is a
A. Reversed Carnot cycle
B. Reversed Otto cycle
C. Reversed Joule cycle
D. Reversed Rankine cycle
Answer : C

37. Freon group of refrigerants are
A. Inflammable
B. Toxic
C. Non-inflammable and toxic
D. Nontoxic and non-inflammable
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. In a refrigerating machine, heat rejected is _________ heat absorbed.
A. Equal to
B. Less than
C. Greater than
D. None of these
Answer : C

40. 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

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

42. 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

43. 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

44. The value of C.O.P in vapour compression cycle is usually
A. Always less than unity
B. Always more than unity
C. Equal to unity
D. Any one of the above
Answer : B

45. 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

46. The higher temperature in vapour compression cycle occurs at
A. Receiver
B. Expansion valve
C. Evaporator
D. Compressor discharge
Answer : D

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

48. The capillary tube, as an expansion device, is used in
A. Domestic refrigerators
B. Water coolers
C. Room air conditioners
D. All of these
Answer : D

49. A pressure gauge on the discharge side of a refrigerant compressor reads too high. The reasons will be
A. Lack of cooling water
B. Water temperature being high
C. Dirty condenser surface
D. All of these
Answer : D

50. Cooling water is required for following equipment in ammonia absorption plant
A. Condenser
B. Evaporator
C. Absorber
D. Condenser, absorber and separator (rectifier)
Answer : D