Refrigeration & Air-Conditioning 1000+ MCQ with answer for CLAT PG

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

2. 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

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

4. 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

5. The wet bulb temperature at 100% relative humidity is ________ dry bulb temperature.
A. Same as
B. Lower than
C. Higher than
D. None of these
Answer : A

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

7. 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

8. A standard ice point temperature corresponds to the temperature of
A. Water at 0°C
B. Ice at 4°C
C. Solid and dry ice
D. Mixture of ice and water under equilibrium conditions
Answer : D

9. In a domestic refrigerator, a capillary tube controls the flow of refrigerant from the
A. Expansion valve to the evaporator
B. Evaporator to the thermostat
C. Condenser to the expansion valve
D. Condenser to the evaporator
Answer : A

10. 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

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

12. 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

13. Dry 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 : A

14. 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

15. 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

16. In S.J. unit, one ton of refrigeration is equal to
A. 210 kJ/ min
B. 21 kJ/ min
C. 420 kJ/ min
D. 840 kJ/ min
Answer : A

17. The leaks in a refrigeration system using Freon are detected by
A. Halide torch which on detection produces greenish flame lighting
B. Sulphur sticks which on detection gives white smoke
C. Using reagents
D. Smelling
Answer : A

18. 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

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

20. An infinite parallel planes with emissivities e? and e?, the interchange factor for radiation from surface 1 to surface 2 is given by
A. (e? + e?)/ e? + e? - e?e?
B. 1/e? + 1/e?
C. e? + e?
D. e?e?
Answer : A

21. The refrigerant for a refrigerator should have
A. High sensible heat
B. High total heat
C. High latent heat
D. Low latent heat
Answer : C

22. 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

23. Air refrigeration operates on
A. Carnot cycle
B. Reversed Carnot cycle
C. Rankines cycle
D. Brayton cycle
Answer : D

24. For air conditioning the operation theatre in a hospital, the percentage of outside air in the air supplied is
A. Zero
B. 20
C. 50
D. 100
Answer : D

25. 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

26. 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

27. 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

28. 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

29. A heat pump working on a reversed Carnot cycle has a C.O.P. of 5. It works as a refrigerator taking 1 kW of work input. The refrigerating effect will be
A. 1 kW
B. 2 kW
C. 3 kW
D. 4 kW
Answer : D

30. Ammonia is
A. Non-toxic
B. Non-inflammable
C. Toxic and non-inflammable
D. Highly toxic and inflammable
Answer : D

31. The refrigerant after condensation process is cooled below the saturation temperature before throttling. Such a process is called
A. Sub-cooling or under-cooling
B. Super-cooling
C. Normal cooling
D. None of these
Answer : A

32. The domestic refrigerator uses following type of compressor
A. Centrifugal
B. Axial
C. Miniature sealed unit
D. Piston type reciprocating
Answer : D

33. 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, is called
A. Humidity ratio
B. Relative humidity
C. Absolute humidity
D. Degree of saturation
Answer : B

34. A certain refrigerating system has a normal operating suction pressure of 10 kg/cm gauge and condensing pressure of about 67 kg/cm. The refrigerant used is
A. Ammonia
B. Carbon dioxide
C. Freon
D. Brine
Answer : B

35. The coefficient of performance of Electrolux refrigerator is the ratio of
A. Heat supplied by the gas burner to the heat absorbed by the evaporator
B. Heat absorbed by the evaporator to the heat supplied by the gas burner
C. Heat supplied by the gas burner minus the heat absorbed by the evaporator to the heat supplied by the gas burner
D. Heat absorbed by the evaporator minus the heat supplied by the gas burner to the heat absorbed by the evaporator
Answer : B

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

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

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

39. 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

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

41. The fluids used in Electrolux refrigerator are
A. Water and hydrogen
B. Ammonia and hydrogen
C. Ammonia, water and hydrogen
D. None of these
Answer : C

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

43. 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

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

45. If the evaporator temperature of a plant is lowered, keeping the condenser temperature constant, the h.p. of compressor required will be
A. Same
B. More
C. Less
D. More/less depending on rating
Answer : B

46. 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

47. 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

48. 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

49. 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

50. Freon group of refrigerants are
A. Inflammable
B. Toxic
C. Non-inflammable and toxic
D. Nontoxic and non-inflammable
Answer : D