MCQ on Refrigerator & AC 51-105

51. One ton refrigeration corresponds to
(A) 50 kcal/ min✔
(B) 50 kcal/ hr
(C) 80 kcal/ min
(D) 80 kcal/ hr

52. 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

53. 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

54. 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

55. In vapour compression cycle, the condition of refrigerant is saturated liquid
(A) After passing through the condenser✔
(B) Before passing through the condenser
(C) After passing through the expansion throttle valve
(D) Before entering the expansion valve

56. Which of the following refrigerant has the maximum ozone depletion potential in the stratosphere?
(A) Ammonia
(B) Carbon dioxide
(C) Sulphur dioxide
(D) Fluorine✔

57. 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

58. Hydrogen is used in Electrolux refrigeration system so as to _________ the rate of evaporation of the liquid ammonia passing through the evaporator.
(A) Equalize
(B) Reduce
(C) Increase✔
(D) None of these

59. Pick up the wrong statement. A refrigerant should have
(A) Tow specific heat of liquid
(B) High boiling point✔
(C) High latent heat of vaporisation
(D) Higher critical temperature

60. The pressure at the inlet of a refrigerant compressor is called
(A) Suction pressure✔
(B) Discharge pressure
(C) Critical pressure
(D) Back pressure

61. Condensing temperature in a refrigerator is the temperature
(A) Of cooling medium
(B) Of freezing zone
(C) Of evaporator
(D) At which refrigerant gas becomes liquid✔

62. In aircraft, air refrigeration Cycle is used because of
(A) Low weight per tonne of refrigeration✔
(B) High heat transfer rate
(C) Low temperature at high altitudes
(D) Higher coefficient of performance

63. Highest pressure encountered in a refrigeration system should be
(A) Critical pressure of refrigerant
(B) Much below critical pressure✔
(C) Much above critical pressure
(D) Near critical pressure

64. 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

65. 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

66. The dry bulb temperature during sensible heating of air
(A) Remains constant
(B) Increases✔
(C) Decreases
(D) None of these

67. Vertical lines on pressure-enthalpy chart show constant
(A) Pressure lines
(B) Temperature lines
(C) Total heat lines✔
(D) Entropy lines

68. During heating and dehumidification process, dry bulb temperature
(A) Remains constant
(B) Increases✔
(C) Decreases
(D) None of these

69. 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

70. 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

71. 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✔

72. In a bootstrap air evaporative cooling system, the evaporator is provided
(A) Between the combustion chamber and the first heat exchanger
(B) Between the first heat exchanger and the secondary compressor
(C) Between the secondary compressor and the second heat exchanger
(D) Between the second heat exchanger and the cooling turbine✔

73. The COP of a domestic refrigerator
(A) Is less than 1
(B) Is more than 1✔
(C) Is equal to 1
(D) Depends upon the make

74. The air cooling system mostly used in transport type aircrafts is
(A) Simple air cooling system
(B) Simple evaporative air cooling system
(C) Bootstrap air cooling system✔
(D) All of these

75. The higher temperature in vapour compression cycle occurs at
(A) Receiver
(B) Expansion valve
(C) Evaporator
(D) Compressor discharge✔

76. 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

77. 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

78. The evaporator changes the low pressure liquid refrigerant from the expansion valve into
(A) High pressure liquid refrigerant
(B) Low pressure liquid and vapour refrigerant
(C) Low pressure vapour refrigerant✔
(D) None of these

79. 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

80. Carbon dioxide is
(A) Colourless
(B) Odourless
(C) Non-flammable
(D) All of these✔

81. 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✔

82. 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

83. If a gas is to be liquefied, its temperature must be
(A) Increased to a value above its critical temperature
(B) Reduced to a value below its critical temperature
(C) Equal to critical temperature✔
(D) None of the above

84. The capacity of a domestic refrigerator is in the range of
(A) 0.1 to 0.3 TR✔
(B) 1 to 3 TR
(C) 3 to 5 TR
(D) 5 to 7 TR

85. The lowest thermal diffusivity is of
(A) Iron
(B) Lead
(C) Aluminium
(D) Rubber✔

86. In a vapour compression cycle, the refrigerant immediately after expansion valve is
(A) Liquid
(B) Sub-cooled liquid
(C) Saturated liquid
(D) Wet vapour✔

87. Which of the following statement is correct for ammonia as a refrigerant?
(A) It is toxic to mucous membranes.
(B) It requires large displacement per TR compared to fluoro carbons.
(C) It reacts with copper and its alloys.
(D) All of these✔

88. Critical pressure of a liquid is the pressure
(A) Above which liquid will remain liquid✔
(B) Above which liquid becomes gas
(C) Above which liquid becomes vapour
(D) Above which liquid becomes solid

89. The optimum effective temperature for human comfort is
(A) Higher in winter than in summer
(B) Lower in winter than in summer✔
(C) Same in winter and summer
(D) Not dependent on season

90. Formation of frost on evaporator in refrigerator
(A) Results in loss of heat due to poor heat transfer✔
(B) Increases heat transfer rate
(C) Is immaterial
(D) Can be avoided by proper design

91. 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✔

92. The suction pipe diameter of refrigerating unit compressor in comparison to delivery side is
(A) Bigger✔
(B) Smaller
(C) Equal
(D) Smaller/bigger depending on capacity

93. The coefficient of performance (C.O.P.) of a refrigerator working as a heat pump is given by
(A) (C.O.P.)P = (C.O.P.)R + 2
(B) (C.O.P.)P = (C.O.P.)R + 1✔
(C) (C.O.P)P = (C.O.P)R - 1
(D) (C.O.P)P = (C.O.P)R

94. Presence of moisture in a refrigerant affects the working of
(A) Compressor
(B) Condenser
(C) Evaporator
(D) Expansion valve✔

95. During heating and humidification, the final relative humidity of air
(A) Can be lower or higher than that of the entering air✔
(B) Is lower than that of the entering air
(C) Is higher than that of the entering air
(D) None of the above

96. Which of the following cycles uses air as the refrigerant?
(A) Ericson
(B) Stirling
(C) Carnot
(D) Bell Coleman✔

97. The curved lines on a psychrometric chart indicates
(A) Dry bulb temperature
(B) Wet bulb temperature
(C) Dew point temperature
(D) Relative humidity✔

98. On the pressure-enthalpy diagram, condensation and desuperheating is represented by a horizontal line because the process
(A) Involves no change in volume
(B) Takes place at constant temperature
(C) Takes place at constant entropy
(D) Takes place at constant pressure✔

99. When the temperature of the surrounding is higher than the temperature of the body, then the heat loss by convection from the body to the surrounding will be
(A) Positive
(B) Negative✔
(C) Zero
(D) None of these

100. The general rule for rating refrigeration systems (excepting for CO₂ system) is to approximate following h.p. per ton of refrigeration
(A) 0.1 to 0.5 h.p. per ton of refrigeration
(B) 0.5 to 0.8 h.p. per ton of refrigeration
(C) 1 to 2 h.p. per ton of refrigeration✔
(D) 2 to 5 h.p. per ton of refrigeration

101. The atmospheric air at dry bulb temperature of 15°C enters a heating coil maintained at 40°C. The air leaves the heating coil at 25°C. The bypass factor of the heating coil is
(A) 0.376
(B) 0.4
(C) 0.6✔
(D) 0.67

102. The change in evaporator temperature in a refrigeration cycle, as compared to change in condenser temperature, influences the value of C.O.P.
(A) More✔
(B) Less
(C) Equally
(D) Unpredictable

103. Most thermostatic expansion valves are set for a superheat of
(A) 5°C✔
(B) 10°C
(C) 15°C
(D) 20°C

104. In a refrigeration system, heat absorbed in comparison to heat rejected is
(A) More✔
(B) Less
(C) Same
(D) More for small capacity and less for high capacity

105. 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