MCQ
81. In a refrigeration cycle, the flow of refrigerant is controlled by-
The basic functions of an expansion device used in refrigeration rystems are to:
1. Reduce pressure from condenser pressure to evaporator pressure, and
2. Regulate the refrigerant flow from the high-pres liquid line into the evaporator at a rate equal tot evaporation rate in the evaporate
Compressor
Condenser
Evaporator
Expansion valve
82. The relative coefficient of performance is equal to-
Theortical COP/Actual COP
Actual COP/Theortical COP
Actual COP x Theoretical COP
none of these
83. Vertical Laes on pressure-enthalpy chart show consent-
pressure lines
total heat lines
temperature lines
entropy lines
84. A heat pump working on a reversed Carnot cycle has a COP of 4. It works as a refrigerator taking 1 kW of work input. The refrigerating effect will be-
1KW
2kW
3kW
4kW
85. The COP of a refrigeration cycle with increase in evaporatour temperature, keeping condenser temperature constant will-.
decrease
increase
remain unaffected
unpredictable
86. The COP of a domestic refrigerator in comparison to domestic air conditioner will be--
same
less
more
unpredictable
87. The refrigeration effect in a dry evaporator compared to flooded evaporator in a similar plant is-.
same
less
more
unpredictable
88. The operating temperature of a cold storage is -4°C. The heat leakage from the surrounding is 30kW for the ambient temperature of 35°C. The actual COP of refrigeration plant used is one fourth that of ideal plant working between the same temperatures. The power required to drive the plant is-
1.86kW
7.44kW
3.72kW
21.74W
89. For the same capacity of plant, the COP of the vapor absorption refrigeration system is--
lower than the COP of the vapour compression refrigeration system
higher than the COP of the vapour compression refrigeration system
same as the COP of the vapour compression refrigeration system
none of the above
90. The COP of a vapor compression plant in comparison to vapor absorption plant is-
more
same
less
unpredictable
91. The evolution of heat of solution takes place in ammonia absorption plant when--
ammonia vapour goes into solution
ammonia vapour is driven out of solution
lithium bromide mixes with ammonia
weak solution mixes with strong solution
92. Cooling water is required for following equipment in ammonia absorption plant-
condenser
evaporator
absorber
condenser, absorber and separator (rectifier)
93. The mass of water vapour present in.......... is called absolute humidity.
1m³ of wet air
1kg of wet air
1m³ of dry air
1kg of dry air
94. A reversible engine has ideal thermal efficiency of 30%. When it is used as a refrigerating machine with all other conditions unchanged, the coefficient of performance will be-
1.33
3.33
2.33
4.33
95. Reducing suction pressure in refrigeration cycle-.
lowers evaporation temperature
increases power required per ton of refrigeration
lowers compressor capacity because vapour is highter
reduces weight displaced by piston
all of the above
96. One tonne of refrigeration (1 TR) means that the heat removing capacity is-
21kJ/min
420kJ/min
210kJ/min
620kl/min
97. Most of the domestic refrigerators work on the following refrigeration system-.
vapour compression.
vapour absorption
Carnot cycle
electrolux refrigerator
98. The change in evaporator temperature in a refrigeration cycle, as compared to change in condenser temperature, influences the value of COP-
more
equally
less
unpredictable
99. Which of the following refrigerants has lowest freezing point?
Freon-12
NH
CO
Freon-22
100. The COP of a refrigeration cycle with lowering of condenser temperature, keeping the evaporator temperature constant will-
increase
decrease
unpredictable
remain unaffected