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MCQ
61. A good refrigerant should have-
high latent heat of vaporisation and low freezing point
high operating pressures and low freezing point
high specific volume and high latent heat of vaporisation
low COP and low freezing point
64. The function of oil separator in vapour compression refrigerator is to-
lubricate the compressor
Prevent the oil being carried to condenser
reduce the heat transfer effeciency
none of the above
67. A condenser of refrigeration system rejects heat at the rate of 120kW while its compressor consunes a power of 30 kW. The coefficient of performance of the system would be-
1/4
3
4
1/3
72. In order to collect liquid refrigerant and to prevent if from going to a----- device known as necumulator is used at the suction of compressor.
compressor
expansion valve
condenser
evaporator
80. A refrigerating system operating on reversed Brayton refrigeration cycle is used for maintaining 250K. If the temperature at the end of constant pressure cooling is 300K and rise in the temperature of air in the refrigerator is 50K, then the net work of compression will be (assuune air as working substance with Cp=1kJ/kgK-
25kJ/kg
50kJ/kg
100kJ/kg
125kJ/kg