Refrigeration and Air conditioning | Set 3

1. "The difference between the length of a certain brass rod and that of a steel rod is clamped to be constant at all temperatures". The above statement

A. can never be true

B. can be valid only for temperatures below 0?C

C. can be true provided their lengths are directly proportional to the linear coefficients of the material of the rod

D. can be true provided their lengths are directly proportional to the linear coefficients of the material of the rod

E. None of the above

Correct : D. can be true provided their lengths are directly proportional to the linear coefficients of the material of the rod

2. Ten grams of moisture per kg of dry air is removed from atmospheric air during air conditioning and the temperature becomes 30?C. If the atmospheric conditions are 40?C DBT and 60% Relative humidity, the RH of air after refrigeration would be

3. PVC tubes are used for condenser and evaporator when the refrigerant is

4. Which reciprocating compressor is usually used in domestic refrigerators?

5. A Carnot refrigerator extracts 100 kcal of heat per minute from a cold room which is maintained at - 15?C and it is discharged to atmosphere 30C?. The horse power required to run the unit would be

6. If space occupied by the refrigerating plant and cost is the major consideration, which of the following refrigerant will be preferred?

7. When ammonia is the refrigerant, which of the following will be be the material for pipe through which refrigerant flows?

8. Moisture in Freon refrigeration system causes

A. Ineffective refrigeration

B. Damage to compressor

C. High power consumption

D. Freezing of automatic regulating valve

E. None of the above

Correct : D. Freezing of automatic regulating valve

9. Which of the following is not a desirable property of a refrigerant?

A. High critical temperature

B. Low specific heat of liquid

C. Low boiling point

D. High specific volume of air

E. All of the above

Correct : D. High specific volume of air

10. A Carnot refrigerator operates between 300.3 K and 273 K. The fraction of cooling effect required as work input is

11. A thermometer in the compressor discharge line

A. Confirms the flow of refrigerant

B. Indicates the efficiency of cycle

C. Helps in adjusting the compressor performance

D. Shows the heat of refrigerant leaving the cylinder on way to the condenser

E. None of the above

Correct : D. Shows the heat of refrigerant leaving the cylinder on way to the condenser

12. Freon 12 is a compound consisting of stoms of

A. Carbon, hydrogen and fluorine

B. Carbon and hydrogen

C. Carbon, hydrogen, fluorine and chlorine

D. Carbon, fluorine and chlorine

E. Carbon, hydrogen and oxygen

Correct : D. Carbon, fluorine and chlorine

13. During sensible of cooling of air

A. Wet bulb temperature decreases and relative humidity increases

B. Both wet bulb temperatures as well as relative humidity increase

C. Both humidity ratio as well as relative humidity remain constant

D. Both wet bulb temperature as well as relative humidity decrease

E. Wet bulb temperatures increases and relative humidity decreases

Correct : A. Wet bulb temperature decreases and relative humidity increases

14. The type of compressor used in refrigeration system is

15. In a refrigeration cycle the heat is rejected by refrigerant at

16. 2 HP per ton of refrigeration is required to maintain the temperature of - 40?C in the refrigerator if the refrigeration cycle works on Carnot cycle. The COP of the cycle would be

17. An average adult while sitting in a cinema hall

A. Discharges about 100 kcal of heat per hour

B. Discards about 500 kcal of heat per hour

C. Absorbs about 500 kcal of heat per hour

D. Neither absorbs nor discards heat

E. Absorbs about 100 kcal of heat per hour

Correct : A. Discharges about 100 kcal of heat per hour

18. During compression in a vapour compression cycle of the refrigerant is super heated

19. The heat removed capacity of a one ton refrigerator is

20. A prssure gauge on the discharge side of compressor

A. Is mounted for show only

B. Indicates the temperature of refrigerant after compression

C. Gives a warning when the pressure reaches a dangerous point

D. Gives an ideas about the coefficient of performance of the cycle

E. Confirms the flow of refrigerant in cycle

Correct : C. Gives a warning when the pressure reaches a dangerous point

21. Major modification required to produce temperature of - 200?C in a vapour compression refrigeration system using Freon 12 as refrigerant, is

A. Condenser capacity must be increased to handle the refrigerant

B. Size of compressor required would be large to handle volumes of vapour

C. Compression ratio has to be restricted till stronger body of compressor is needed

D. Freon 12 cannot be used for such low temperatures

E. Insulation should be capable of withstanding such low temperatures

Correct : D. Freon 12 cannot be used for such low temperatures

22. In a vapour absorption refrigeration system the power is required for vapour compressor as compared to that in vapour compression cycle is

23. In a mechanical refrigeration system the refrigerant occurs as liquid (or very wet vapour) between

A. Before and after compressor

B. Expansion valve or evaporator

C. Condenser and expansion valve

D. Evaporation valve and compressor

E. Compressor outlet and condenser

Correct : C. Condenser and expansion valve

25. The ratio of specific humidity of moist air to the specific immidity of the saturated air at the same temperature, is known as

A. Absolute humidity

B. Degree of saturation and degree of reaction

C. Relative humidity

D. Any of the above

E. None of the above

Correct : B. Degree of saturation and degree of reaction

26. Dehydration means

A. Removing steam from any matter

B. Removing water from any matter

C. Removing hydrogen from any matter

D. Removing hydrogen from a hydrocarbon

E. Removing hydrogen from a mixture

Correct : B. Removing water from any matter

27. Defrosting in a refrigerator may be done by

A. Stopping the compressor for a while

B. Opening the door of refrigerator

C. Placing trays of warm water in the refrigerator

D. Any of the above

E. None of the above

Correct : D. Any of the above

28. A cooling tower in a refrigeration system

A. Removes heat from refrigerant

B. Removes heat from brine

C. Removes heat from lubricating oil

D. Removes heat from hot water coming out of condenser

E. None of the above

Correct : D. Removes heat from hot water coming out of condenser

29. A hermetic compressor is

A. A reciprocating compressor

B. A valveless compressor

C. A thermodynamically efficient comprossor

D. A factory sealed unit containing motor and compressor

E. None of the above

Correct : D. A factory sealed unit containing motor and compressor

30. A refrigerant is added to vapour compression cycle through

A. High side in vapour form

B. High side in liquid form

C. Low side in liquid form

D. None of the above

E. Any of the above

Correct : B. High side in liquid form

32. Dalton's law of partial pressure state that

A. All gases exert partial pressures only

B. All gases or mixture of gases exent partial pressures

C. All gases or mixture of gases in a container will exert their own pressure on the container entirely indipendent of the others

D. Total pressure exerted by a mixture of gases or vapours is equal to the pressure exerted by individual gases or vapours

E. None of the above

Correct : C. All gases or mixture of gases in a container will exert their own pressure on the container entirely indipendent of the others

33. When moisture is removed from air at constant dry bulb temperature the process is known as

34. In a newly charged ammonia compression system, the clicking sound in the expansion valve indicates

A. High pressure after compression

B. Leakage of ammonia

C. Excessive ammonia charged

D. Lack of ammonia

E. Evaporator coils chocked

Correct : D. Lack of ammonia

35. The difference between wet and dry bulb temperature

A. Increases at atmospheric temperature

B. Increases as air gets wet

C. Increases as air gets drier

D. Remains constant always

E. None of the above

Correct : C. Increases as air gets drier

36. For better performance a desert cooler

A. Should be placed inside the room

B. Should be placed outside

C. Should be mounted on window

D. Should be placed at the roof level

E. None of the above

Correct : C. Should be mounted on window

37. Which of the following are synonyms?

A. Humidity ratio and specific humidity

B. Degree of saturation and degree of reaction

C. Sensible cooling and dehumidification

D. Relative humidity and specific humidity

E. Dehumidification

Correct : A. Humidity ratio and specific humidity

38. At 100% humidity

A. We bulb temperature is same as atmospheric temperature

B. Dry bulb temperature is same as atmospheric temperature

C. Wet bulb temperature is same as dry bulb temperature

D. Dry bulb temperature is exactly half the wet bulb temperature

E. Wet bulb temperature is exactly half the dry bulb temperature

Correct : C. Wet bulb temperature is same as dry bulb temperature

39. Which of the following symptoms will indicate under charging of a vapour compressor refrigeration cycle?

A. Compressor runs continuously

B. Frost on suction line

C. Low suction pressure

D. Low head pressure

E. All of the above

Correct : B. Frost on suction line

41. Cooling towers are used for cooling water

A. To be used for cooling the compressor

B. To be used for filtration of air

C. To be injected in circulating air

D. To be used for humidification

E. To be used for cooling the building

Correct : A. To be used for cooling the compressor

43. In a ammonia vapour compression cycle during gas charging the connection is made

A. Anywhere in the cycle

B. At the compressor cycle

C. On low pressure side near evaporat

D. At the compressor outlet

E. On high pressure side close to receiver

Correct : E. On high pressure side close to receiver

44. In central air conditioning system

A. Entire equipment is placed in the air conditioned space

B. There is only one machine which performs the function of air conditioning

C. All the major equipment is located in one central space removed from the air to be conditioned

D. Is used when small area is to be air conditioned

E. None of the above

Correct : C. All the major equipment is located in one central space removed from the air to be conditioned

47. In order to ensure leak proof mechanical links, the end of copper tubing in refrigeration cycle is

48. A Bell-Coleman cycle is

A. Reversed Otto cycle

B. Reversed Carnot cycle

C. Reversed Sterling cycle

D. Reversed Joule cycle

E. Reversed Rankine cycle

Correct : D. Reversed Joule cycle

49. On a particular time of a day if dry bulb temperature is equal to the wet bulb temperature, then it can be safely concluded that

A. Dew point was less than 20?C

B. Rain had occurred one or two hours earlier

C. Relative humidity of air was 100%

D. Specific humidity of air was 0.010 kg per kg of dry air

E. Atmospheric air was free from moisture

Correct : C. Relative humidity of air was 100%

50. Which of the following is not a dehydrator?

51. A water cooler is installed with one ton vapour compression cycle. In 24 hours it will provide

A. 0.1 ton of cold water

B. One tonne of cold water

C. The change is gradual throughout the cycle

D. More than one tonne of cold water

E. Half ton of cold water

Correct : D. More than one tonne of cold water

52. In rainy season desert coolers become ineffective

A. Because of low temperature

B. Pleasant weather

C. Rain serves the purpose of cooler

D. Humidity of air increases

E. None of the above

Correct : D. Humidity of air increases

53. When Freon 12 is the refrigerant, the condenser and evaporator cables are made of

54. In vapour absorption system using ammonia, water is required for

A. Absorber only

B. Separator only

C. Condenser, absorber and separator

D. Condenser only

E. Condenser and absorber

Correct : C. Condenser, absorber and separator

55. The ratio of mass of water vapour associated with unit mass of dry air to the mass of water vapour associated with unit mass of dry air saturated at the same temperature is known as

56. In a refrigerator system if compressor fails to operate, the probable reason could be

57. A thermometer in vapour compression system is installed in the main line close to the compressor

A. As it helps the operator to adjust compressor for greatest efficiency

B. As temperature indicates whether liquid or vapour refrigerant is going to compressor

C. As temperature helps in calculating the coefficient of performance

D. As the performance of other units of the cycle can be controlled

E. None of the above

Correct : A. As it helps the operator to adjust compressor for greatest efficiency

58. White ice is

A. Sub-cooled water

B. Fast cooled water

C. Due to dissolved air, gases and impurities

D. Produced by blowing air during freezing

E. None of the above

Correct : C. Due to dissolved air, gases and impurities

59. In which type of single phase motor the starting torque is low

A. Capacitor start type

B. Shaded pole type

C. Starting torque is same in all motors

D. Permanent split capacitor type

E. Capacitor start and capacitor run type

Correct : B. Shaded pole type

61. Dew points temperature is an indication of

A. Moisture content of air

B. Dryness of air

C. Lowest temperature where air and water vapour start separating

D. Condition air

E. Any of the above

Correct : A. Moisture content of air

62. The most common type of vapour absorption system in use for industrial application is

63. Brazing is the process used for joining

A. Two ferrous materials

B. One ferrous and one non-ferrous material

C. Two non-ferrous materials

D. Two non-metals

E. None of the above

Correct : C. Two non-ferrous materials

64. Of the following chemicals the liquid having the greatest cooling effect on an individual is

65. In vapour absorption system the function of rectifier is

A. To cool the vapour leaving the analyzer

B. To separate ammonia and water

C. To dissolve ammonia in water

D. To add energy from external source

E. None of the above

Correct : A. To cool the vapour leaving the analyzer

66. Sometimes refrigeration plants use cooling towers. The water cooled in those towers is supplied

A. For defrosting evaporator coils

B. To cool compressor cylinder only

C. To cool refrigerant in evaporator

D. To cool refrigerant in condenser

E. None of the above

Correct : D. To cool refrigerant in condenser

67. When moisture is added to air at constant dry bulb temperature, the process is known as

68. The condition of refrigerant before and after the condenser in a vapour compression cycle is

A. Wet vapour, wet vapour

B. Dry saturated, wet vapour

C. Dry saturated, dry saturated

D. Liquid, liquid

E. Dry saturated, saturated liquid

Correct : E. Dry saturated, saturated liquid

69. The COP of a reversed Carnot cycle is 5. The ratio of highest absolute temperature to the lowest absolute temperature

70. In case the relative humidity of atmospheric air is 100% the rate of evaporation of water will be

71. In which of the following plants secondary refrigerant is used?

72. If the suction pressure of a refrigeration compressor is too high, it shows

A. Lack of refrigerant on cycle

B. Excessive load and evaporator

C. Negligible load on evaporator

D. Any of above

E. None of the above

Correct : B. Excessive load and evaporator

73. The crankcase explosion of a refrigeration compressor

A. Occurs due to ignition of vapours in compressor crank case

B. Occurs when load is too high

C. Means breakdown in compression

D. Occurs between piston and cylinder heads

E. Means ignition of refrigeration due to high temperature

Correct : A. Occurs due to ignition of vapours in compressor crank case

74. A cooling tower cools water

A. Below wet bulb temperature

B. Equal to wet bulb temperature

C. Slightly above wet bulb temperature

D. Wet bulb has no bearing on cooling load performance

E. None of the above

Correct : C. Slightly above wet bulb temperature

75. While designing air conditioning system for a theatre the various heat loads are categorized as given below. Which one will give lowest heat load?

76. The secondary refrigerant used in milk chilling plants is usually

77. Hydrogen cannot be liquefied at room temperature by the application of pressure, because

A. It is a diatomic molecule

B. It has high viscosity

C. Its critical temperature is lower than the normal room temperature

D. Its thermal conductivity is high

E. It has low density

Correct : C. Its critical temperature is lower than the normal room temperature

78. The condension of moisture contained in air will take place at

A. Any where between dry bulb temperature and wet bulb temperature

B. Dew point temperature

C. Dry bulb temperature

D. Wet bulb temperature

E. Saturation temperature

Correct : B. Dew point temperature

79. If a discharge pressure of a refrigeration compressor is too high, it shows there is (are)

A. Too little or too warm condenser water

B. Fouled tubes in shell and tube condenser

C. Improper operations of evaporator condenser

D. Overcharge of refrigerant

E. Any of the above

Correct : E. Any of the above

80. The statement that molecular weight of all gases occupy the same volume at NTP is known as

81. The condition of refrigerant before and after the expansion or throttle valve in a vapour compression system is

A. Wet vapour, very wet vapour

B. Wet vapour, dry vapour

C. High pressure saturated liquid, very wet vapour

D. Very wet vapour, high pressure, saturated liquid

E. None of the above

Correct : C. High pressure saturated liquid, very wet vapour

82. The function of desuperheating coil in a condenser is

A. To remove heat from condenser

B. To improve performance of a condenser

C. To discharge the heat exchanged in condenser to the surroundings

D. To remove the heat of superheat of the refrigerant before it enters the condenser

E. None of the above

Correct : D. To remove the heat of superheat of the refrigerant before it enters the condenser

83. When the air temperature reaches the point where relative humidity is 100% the air is saturated because it cannot hold any more moisture. This temperature is called

84. An increase in the movement of the molecules within a solid, liquid or gas corresponds to

A. A drop in temperature

B. No change in temperature

C. Latent heat addition/removal

D. A rise in temperature

E. None of the above

Correct : D. A rise in temperature

Quiznetik

Refrigeration and Air conditioning | Set 3

1. "The difference between the length of a certain brass rod and that of a steel rod is clamped to be constant at all temperatures". The above statement

2. Ten grams of moisture per kg of dry air is removed from atmospheric air during air conditioning and the temperature becomes 30?C. If the atmospheric conditions are 40?C DBT and 60% Relative humidity, the RH of air after refrigeration would be

3. PVC tubes are used for condenser and evaporator when the refrigerant is

4. Which reciprocating compressor is usually used in domestic refrigerators?

5. A Carnot refrigerator extracts 100 kcal of heat per minute from a cold room which is maintained at - 15?C and it is discharged to atmosphere 30C?. The horse power required to run the unit would be

6. If space occupied by the refrigerating plant and cost is the major consideration, which of the following refrigerant will be preferred?

7. When ammonia is the refrigerant, which of the following will be be the material for pipe through which refrigerant flows?

8. Moisture in Freon refrigeration system causes

9. Which of the following is not a desirable property of a refrigerant?

10. A Carnot refrigerator operates between 300.3 K and 273 K. The fraction of cooling effect required as work input is

11. A thermometer in the compressor discharge line

12. Freon 12 is a compound consisting of stoms of

13. During sensible of cooling of air

14. The type of compressor used in refrigeration system is

15. In a refrigeration cycle the heat is rejected by refrigerant at

16. 2 HP per ton of refrigeration is required to maintain the temperature of - 40?C in the refrigerator if the refrigeration cycle works on Carnot cycle. The COP of the cycle would be

17. An average adult while sitting in a cinema hall

18. During compression in a vapour compression cycle of the refrigerant is super heated

19. The heat removed capacity of a one ton refrigerator is

20. A prssure gauge on the discharge side of compressor

21. Major modification required to produce temperature of - 200?C in a vapour compression refrigeration system using Freon 12 as refrigerant, is

22. In a vapour absorption refrigeration system the power is required for vapour compressor as compared to that in vapour compression cycle is

23. In a mechanical refrigeration system the refrigerant occurs as liquid (or very wet vapour) between

24. The chemical formula for Freon-12 is

25. The ratio of specific humidity of moist air to the specific immidity of the saturated air at the same temperature, is known as

26. Dehydration means

27. Defrosting in a refrigerator may be done by

28. A cooling tower in a refrigeration system

29. A hermetic compressor is

30. A refrigerant is added to vapour compression cycle through

31. The horse power per ton of refrigerating effect when ammonia is used as a refrigerant, will be nearly

32. Dalton's law of partial pressure state that

33. When moisture is removed from air at constant dry bulb temperature the process is known as

34. In a newly charged ammonia compression system, the clicking sound in the expansion valve indicates

35. The difference between wet and dry bulb temperature

36. For better performance a desert cooler

37. Which of the following are synonyms?

38. At 100% humidity

39. Which of the following symptoms will indicate under charging of a vapour compressor refrigeration cycle?

40. The drift loss in cooling towers is around

41. Cooling towers are used for cooling water

42. Refrigerant 744 is

43. In a ammonia vapour compression cycle during gas charging the connection is made

44. In central air conditioning system

45. A refrigerant cycle is usually a

46. Refrigerant R-40 is

47. In order to ensure leak proof mechanical links, the end of copper tubing in refrigeration cycle is

48. A Bell-Coleman cycle is

49. On a particular time of a day if dry bulb temperature is equal to the wet bulb temperature, then it can be safely concluded that

50. Which of the following is not a dehydrator?

51. A water cooler is installed with one ton vapour compression cycle. In 24 hours it will provide

52. In rainy season desert coolers become ineffective

53. When Freon 12 is the refrigerant, the condenser and evaporator cables are made of

54. In vapour absorption system using ammonia, water is required for

55. The ratio of mass of water vapour associated with unit mass of dry air to the mass of water vapour associated with unit mass of dry air saturated at the same temperature is known as

56. In a refrigerator system if compressor fails to operate, the probable reason could be

57. A thermometer in vapour compression system is installed in the main line close to the compressor

58. White ice is

59. In which type of single phase motor the starting torque is low

60. Air conditioning means

61. Dew points temperature is an indication of

62. The most common type of vapour absorption system in use for industrial application is

63. Brazing is the process used for joining

64. Of the following chemicals the liquid having the greatest cooling effect on an individual is

65. In vapour absorption system the function of rectifier is

66. Sometimes refrigeration plants use cooling towers. The water cooled in those towers is supplied

67. When moisture is added to air at constant dry bulb temperature, the process is known as

68. The condition of refrigerant before and after the condenser in a vapour compression cycle is

69. The COP of a reversed Carnot cycle is 5. The ratio of highest absolute temperature to the lowest absolute temperature

70. In case the relative humidity of atmospheric air is 100% the rate of evaporation of water will be

71. In which of the following plants secondary refrigerant is used?

72. If the suction pressure of a refrigeration compressor is too high, it shows

73. The crankcase explosion of a refrigeration compressor

74. A cooling tower cools water

75. While designing air conditioning system for a theatre the various heat loads are categorized as given below. Which one will give lowest heat load?

76. The secondary refrigerant used in milk chilling plants is usually

77. Hydrogen cannot be liquefied at room temperature by the application of pressure, because

78. The condension of moisture contained in air will take place at