refrigeration and air conditioning MCQs – Page 2

Practise focused refrigeration and air conditioning questions with marked answers for exam preparation and subject revision.

refrigeration and air conditioning Mcqs
51. For better COP of refrigerator, the pressure range corresponding to temperature in evaporator and condenser must be____________________?
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A. high

B. euqal

C. under some conditions small and under some conditions high

D. anything

E. small
52. In vapor compression cycle the condition off refrigerant is dry saturated vapor________________?
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A. before entering the expansion valve

B. before passing through the condenser

C. before entering the compressor

D. after passing through the condenser

E. after passing through the expansion or throttle valve

53. Air refrigeration operates on_____________________?
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A. Rankine cycle

B. Reversed Carnot cycle

C. Erricson cycle

D. Brayton cycle

E. Carnot cycle

54. The vapor compression refrigerator employs the following cycle_________________?
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A. Reversed Carnot

B. Brayton

C. Carnot

D. Reversed Rankine

E. Rankine

55. In a refrigeration cycle, the flow of refrigerant is controlled by___________________?
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A. condenser

B. all of the above

C. evaporator

D. expansion valve

E. compressor

56. In refrigerators, the temperature difference between the evaporating refrigerant and the medium being cooled should be_________________?
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A. as low as possible (3 to 11C)

B. zero

C. high, of the order of 25

D. none of the above

E. any value

57. Refrigeration in aeroplanes usually employs the following refrigerant___________________?
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A. Freon-11

B. Freon-22

C. Co2

D. none of the above

E. Air
58. The higher temperature in vapour compression cycle occurs at____________________?
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A. receiver

B. compressor discharge

C. expansion valve

D. evaporator

E. condenser discharge

59. The general rule for rating refrigeration systems (excepting for C02 system) is to approximate following h.p. per ton of refrigeration__________________?
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A. 0.5 to 0.8 h.p. per ton of refrigeration

B. 2 to 5 h.p. per ton of refrigeration

C. 0.1 to 0.5 h.p. per ton of refrigeration

D. 5 to 10 h.p. per ton refrigeration

E. 1 to 2 h.p. per ton of refrigeration
60. The lower horizontal line of the refrigeration cycle plotted on pressure-enthalpy-diagram represents_____________________?
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A. metering of the refrigerant liquid

B. none of the above

C. evaporation of the refrigerant liquid

D. compression of the refrigerant vapour

E. condensation of the refrigerant vapour

61. The domestic refrigerator uses following type of compressor ____________________?
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A. axial

B. none of the above

C. piston type reciprocating

D. centrifugal

E. miniature sealed unit

62. Super heating in a refrigeration cycle __________________?
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A. decreases COP

B. COP remains unaltered

C. unpredictable

D. other factors decide COP

E. increases COP

63. The condensing pressure due to the presence of non-condensable gases, as compared to that actually required for condensing temperatures without non-condensable gases ____________________ ?
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A. may be higher or lower depending upon the nature of non-condensable gases

B. will remain unaffected

C. will be higher

D. unpredictable

E. will be lower

64. Cooling water is required for following equipment in ammonia absorption plant__________________?
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A. evaporator

B. absorber

C. condenser and absorber

D. condenser, absorber and separator (rectifier)

E. condenser

65. One ton of the refrigeration is_________________?
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A. the standard unit used in refrigeration problems

B. the refrigeration effect to produce 1 ton of ice in 1 hour time

C. the cooling effect produced by melting 1 ton of ice

D. the refrigeration effect to produce 1 ton of ice at NTP conditions

E. the refrigeration effect to freeze 1 ton of water at 0C into ice at 0C in 24 hours
66. Domestic refrigerator working on vapour compression cycle uses the following type of expansion device____________________?
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A. electrically operated throttling valve

B. capillary tube

C. expansion valve.

D. manually operated valve

E. thermostatic valve

67. Under-cooling in a refrigeration cycle_________________?
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A. COP remains unaltered

B. decreases COF

C. increases COP

D. other factors decide COP

E. unperdictable

68. In vapor compression refrigeration system, refrigerant occurs as liquid between_________________?
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A. compressor and evaporator

B. none of the above

C. compressor and condenser

D. expansion valve and evaporator

E. condenser and expansion valve

69. The COP of a vapor compression plant in comparison to vapor absorption plant is ________________?
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A. same

B. unpredictable

C. more/less depending on size of plant

D. less

E. more
70. The moisture in a refrigerant is removed by___________________?
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A. expansion valve

B. driers

C. dehumidifier

D. evaporator

E. safety relief valve

71. The coefficient of performance is the ratio of the refrigerant effect to the_________________?
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A. none of the above

B. enthalpy increase in compressor

C. all of the above

D. work done by compressor

E. heat of compression

72. In a flooded evaporator refrigerator, an accumulator at suction of compressor is used to___________________?
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A. detect liquid in vapour

B. increase refrigeration effect

C. collect liquid refrigerant and prevent it from going to compressor

D. superheat the vapour

E. collect vapours

73. The refrigerant for a refrigerator should have ___________________?
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A. high sensible heat

B. high total heat

C. high latent heat

D. low sensible heat

E. low latent heat

74. Reducing suction pressure in refrigeration cycle_________________?
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A. lowers evaporation temperature

B. lowers compressor capacity because vapour is lighter

C. increases power required per ton of refrigeration

D. all of the above

E. reduces weight displaced by piston

75. Critical pressure of a liquid is the pressure_________________?
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A. above which liquid becomes vapour

B. at which all the three phases exist together

C. above which liquid becomes solid

D. above which liquid becomes gas

E. above which liquid will remain liquid
76. Freon group of refrigerants are___________________?
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A. non-toxic and inflammable

B. inflammable

C. toxic

D. non-toxic and non-inflammable

E. non-inflammable and toxic

77. The vapor pressure of refrigerant should be_________________?
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A. could be anything

B. lower than atmospheric pressure

C. higher than atmospheric pressure

D. none of the above

E. equal to atmospheric pressure

78. Mass flow ratio of NH3 in comparison to Freon-12 for same refrigeration load and same temperature limits is of the order of___________________?
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A. 1:01

B. 9:01

C. 1 : 9

D. 1:03

E. 3:01

79. Where does the lowest temperature occur in a vapour compression cycle ?
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A. condenser

B. evaporator

C. receiver

D. expansion valve

E. compressor

80. In a refrigeration system, heat absorbed in comparison to heat rejected is_________________?
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A. more

B. less for small capacity and more for high capacity

C. less

D. more for small capacity and less for high capacity

E. same

81. Choose the wrong statement ?
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A. Temperature of medium being cooled must be below that of the evaporator

B. frost on evaporator reduces heat transfer

C. refrigerant is circulated in a refrigeration system to transfer heat

D. All solar thermally operated absorption systems are capable only of intermittent operation

E. Refrigerant leaves the condenser as liquid

82. Which of the following is not a desirable property of a refrigerant_________________?
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A. non-inflammable

B. low boiling point

C. good electrical conductor

D. high triiscibility with oil

E. large latent heat

83. At lower temperatures and pressures, the latent heat of vaporisation of a refrigerant_________________?
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A. remains same

B. depends on other factors

C. none of the above

D. decreases

E. increases
84. In a vapor compression cycle, the refrigerant immediately after expansion valve is___________________?
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A. wet vapour

B. saturated liquid

C. liquid

D. dry vapour

E. sub-cooled liquid

85. Pick up the incorrect statement?
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A. weak solution in liquid heat exchanger gives up heat to the strong solution

B. lithium bromide plant cant operate below 0C

C. lithium bromide used in vapour absorption cycle is nonvolatile

D. concentration of solution coming out of lithium bromide generator is more in comparison to that entering the generator

E. a separator is used in lithium bromide plant to remove the unwanted water vapour by condensing
86. Formation of frost on evaporator in refrigerator ________________?
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A. decreases compressor power

B. increases heat transfer rate

C. is immaterial

D. can be avoided by proper design

E. results in loss of heat due to poor heat transfer
87. Absorption system normally uses the following refrigerant___________________?
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A. Freon-22

B. C02

C. ammonia

D. Freon-11

E. S02

88. Choose the correct statement?
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A. Superheat and sensible heat of a. refrigerant are same

B. If operating temperature of system is low, then refrigerant with low boiling point should be used

C. Precooling and subcooling bf refrigerant are same

D. Refrigerant is inside the lubes in case of a direct-expansion chiller

E. A refrigerant should have low latent heat

89. Highest pressure encountered in a refrigeration system should be________________?
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A. near critical pressure

B. there is no such restriction

C. much below critical pressure

D. much above critical pressure

E. critical pressure of refrigerant

90. Highest temperature encountered in refrigeration cycle should be________________?
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A. could be anywhere

B. much below critical temperature

C. above critical temperature

D. near critical temperature of refrigerant

E. at critica. temperature

91. If the evaporator temperature of a plant is lowered, keeping the condenser temperature constant, the h.p. of compressor required will be________________?
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A. more

B. more/less depending on rating

C. less

D. same

E. unpredictable

92. One of the purposes of sub-cooling the liquid refrigerant is to________________?
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A. ensure that only liquid and not the vapour enters the expansion (throttling) valve

B. reduce compressor discharge temperature

C. reduce compressor overheating

D. increase cooling effect

E. none of the above

93. 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________________?
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A. Ammonia

B. Carbon dioxide

C. Freon

D. Brine

E. Hydrocarbon refrigerant

94. Pick up the correct statement about giving up of heat from one medium to other in ammonia absorption system ?
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A. ammonia vapour to strong solution

B. strong solution to weak solution

C. weak solution to strong solution

D. strong solution to ammonia vapour

E. ammonia vapour to weak solution