LIC ADO - Refrigeration & Air-Conditioning 1000+ MCQ [Solved] PDF Download

1. Which of the following refrigerant has the lowest freezing point?
A. R-11
B. R-12
C. R-22
D. Ammonia
Answer : C

2. The centrifugal compressors are generally used for refrigerants that require
A. Small displacements and low condensing pressures
B. Large displacements and high condensing pressures
C. Small displacements and high condensing pressures
D. Large displacements and low condensing pressures
Answer : D

3. The refrigerant used for absorption refrigerators working on heat from solar collectors is a mixture of water and
A. Carbon dioxide
B. Sulphur dioxide
C. Lithium bromide
D. R-12
Answer : C

4. The evolution of heat of solution takes place in ammonia absorption plant when
A. Ammonia vapour goes into solution
B. Ammonia vapour is driven out of solution
C. Lithium bromide mixes with ammonia
D. Weak solution mixes with strong solution
Answer : A

5. The colour of the flame of halide torch, in case of leakage of Freon refrigerant, will change to
A. Bright green
B. Yellow
C. Red
D. Orange
Answer : A

6. 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

7. Most air cooled condensers are designed to operate with a temperature difference of
A. 5°C
B. 8°C
C. 14°C
D. 22°C
Answer : C

8. 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

9. 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

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

11. 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

12. 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

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

14. 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

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

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

17. The moisture in a refrigerant is removed by
A. Evaporator
B. Safety relief valve
C. Dehumidifier
D. Driers
Answer : D

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

19. 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

20. 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

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

22. 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

23. 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

24. 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

25. 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

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

27. 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

28. The condition of refrigerant after passing through the expansion or throttle valve, in a vapour compression system is
A. High pressure saturated liquid
B. Wet vapour
C. Very wet vapour
D. Dry vapour
Answer : C

29. Most of the domestic refrigerators work on the following refrigeration system
A. Vapour compression
B. Vapour absorption
C. Carnot cycle
D. Electrolux refrigerator
Answer : A

30. A refrigeration system
A. Removes heat from a low temperature body and delivers it to a high temperature body
B. Removes heat from a high temperature body and delivers it to a low temperature body
C. Rejects energy to a low temperature body
D. None of the above
Answer : A

31. 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

32. Presence of moisture in a refrigerant affects the working of
A. Compressor
B. Condenser
C. Evaporator
D. Expansion valve
Answer : D

33. The refrigerant used in small tonnage commercial machines (hermetically sealed units) is
A. Ammonia
B. Carbon dioxide
C. Sulphur dioxide
D. R-12
Answer : C

34. 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

35. 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

36. 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

37. The process, generally used in summer air conditioning to cool and dehumidify the air, is called
A. Humidification
B. Dehumidification
C. Heating and humidification
D. Cooling and dehumidification
Answer : D

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

39. The mass of water vapour present in __________ is called absolute humidity.
A. 1 m³ of water
B. 1 m³ of dry air
C. 1 kg of wet air
D. 1 kg of dry air
Answer : B

40. 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

41. 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

42. 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

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

44. 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

45. The process of under-cooling is generally brought about by
A. Circulating more quantity of cooling water through the condenser
B. Using water colder than the main circulating water
C. Employing a heat exchanger
D. Any one of the above
Answer : D

46. 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

47. Mass flow ratio of NH? in comparison to Freon12 for same refrigeration load and same temperature limits is of the order of
A. 1 : 1
B. 1 : 9
C. 9 : 1
D. 1 : 3
Answer : B

48. In refrigerators, the temperature difference between the evaporating refrigerant and the medium being cooled should be
A. High, of the order of 25°
B. As low as possible (3 to 11°C)
C. Zero
D. Any value
Answer : B

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

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