Latest Refrigeration and Air Conditioning mcq with answers-02

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Latest Refrigeration and Air Conditioning Questions and Answers

84. Air refrigeration cycle is used in
(a) domestic refrigerators
(b) commercial refrigerators
(c) air conditioning
(d) gas liquefaction
(e) such a cycle does not exist.
Ans: d

85. In a vapour compression cycle, the refrigerant immediately after expansion valve is
(a) liquid
(b) sub-cooled liquid
(c) saturated liquid
(d) wet vapour
(e) dry vapour.
Ans: d

86. The vapour pressure of refrigerant should be
(a) lower than atmospheric pressure
(b) higher than atmospheric pressure
(c) equal to atmospheric pressure
(d) could be anything
(e) none of the above.
Ans: b

87. For better COP of refrigerator, the pressure range corresponding to temperature in evaporator and condenser must be
(a) small
(b) high
(c) euqal
(d) anything
(e) under some conditions small and under some conditions high.
Ans: a

88. The bank of tubes at the back of domestic refrigerator are
(a) condenser tubes
(b) evaporator tubes
(c) refrigerant cooling tubes
(d) capillary tubes
(e) throttling device.
Ans: a

89. The higher temperature in vapour compression cycle occurs at
(a) receiver
(b) expansion valve
(c) evaporator
(d) condenser discharge
(e) compressor discharge.
Ans: e

90. Highest temperature encountered in refrigeration cycle should be
(a) near critical temperature of refrigerant
(b) above critical temperature
(c) at critica. temperature
(d) much below critical temperature
(e) could be anywhere.
Ans: d

93. Absorption system normally uses the following refrigerant
(a) Freon-11
(b) Freon-22
(c) C02
(d) S02
(e) ammonia.
Ans: e

95. The value of COP in vapour compression cycle is usually
(a) always less than unity
(b) always more than unity
(c) equal to unity
(d) any one of the above
(e) none of the above.
Ans: b

96. 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
(e) less for small capacity and more for high capacity.
Ans: b

97. 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
(e) condensing temperature of ice.
Ans: d

98. 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
(e) decreases compressor power.
Ans: a

103. A refrigeration cycle operates between condenser temperature of + 27°C and evaporator temperature of- 23°C. The Carnot coefficient of performance of cycle will be
(a) 0.2
(b) 1.2
(c) 5
(d) 6
(e) 10.
Ans: c

104. Which of the following is not a desirable property of a refrigerant
(a) high triiscibility with oil
(b) low boiling point
(c) good electrical conductor
(d) large latent heat
(e) non-inflammable.
Ans: c

105. 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
(e) none of the above.
Ans: c

106. Pick up the correct statement about giving up of heat from one medium to other in ammonia absorption system
(a) strong solution to weak solution
(b) weak solution to strong solution
(c) strong solution to ammonia vapour
(d) ammonia vapour to weak solution
(e) ammonia vapour to strong solution.
Ans: b

107. Efficiency of a Cornot 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
(e) none of the above.
Ans: d

107. If a heat pump cycle operates between the condenser temperature of +27°C and evaporator temperature of – 23°C, then the Carnot COP will be
(a) 0.2
(b) 1.2
(c) 5
(d) 6
(e) 10.
Ans: d

109. Aqua ammonia is used as refrigerant in the following type of refrigeration system
(a) compression
(b) direct
(c) indirect
(d) absorption
(e) none of the above.
Ans: d

111. In a refrigeration cycle, the flow of refrigerant is controlled by
(a) compressor
(b) condenser
(c) evaporator
(d) expansion valve
(e) all of the above.
Ans: d

112. Where does the lowest temperature occur in a vapour compression cycle ?
(a) condenser
(b) evaporator
(c) compressor
(d) expansion valve
(e) receiver.
Ans: b

113. 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
(e) sensing reduction in pressure.
Ans: a

124. Pick up the incorrect statement
(a) lithium bromide used in vapour absorption cycle is nonvolatile
(b) lithium bromide plant can’t operate below 0°C
(c) a separator is used in lithium bromide plant to remove the unwanted water vapour by condensing
(d) concentration of solution coming out of lithium bromide generator is more in comparison to that entering the generator
(e) weak solution in liquid heat exchanger gives up heat to the strong solution.
Ans: c

126. Mass flow ratio of NH3 in comparison to Freon-12 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
(e) 3 : 1
Ans: b

127. Freon group of refrigerants are
(a) inflammable
(d) toxic
(c) non-inflammable and toxic
(d) non-toxic and inflammable
(e) non-toxic and non-inflammable.
Ans: e

128 Ammonia is
(a) non-toxic
(b) non-inflammable
(c) toxic and non-inflammable
(d) highly toxic and inflammable
(e) none of the above.
Ans: d

129. In vapour compression cycle using NH3 as refrigerant, initial charge is filled at
(a) suction of compressor
(b) delivery of compressor
(c) high pressure side close to receiver
(d) low pressure side near receiver
(e) anywhere in the cycle.
Ans: c

132. 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
(e) the refrigeration effect to produce 1 ton of ice in 1 hour time.
Ans: c

134. Superheating in a refrigeration cycle
(a) increases COP
(b) decreases COP
(c) COP remains unaltered
(d) other factors decide COP
(e) unpredictable.
Ans: b

135. For proper refrigeration in a cabinet, if the temperature and vapour pressure difference between cabinet and atmosphere is high, then
(a) bigger cabinet should be used
(b) smaller cabinet should be used
(c) perfectly tight vapour seal should be used
(d) refrigerant with lower evaporation temperature should be used
(e) refrigerant with high boiling point must be used.
Ans: c