Image
MCQ
924. 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
925. 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
930. 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
932. 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
935. The COP of a refrigeration cycle with increase in evaporatour temperature, keeping condenser temperature constant will-.
decrease
increase
remain unaffected
unpredictable
936. The COP of a refrigeration cycle with lowering of condenser temperature, keeping the evaporator temperature constant will-
increase
decrease
unpredictable
remain unaffected
937. 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