MCQ
2201. 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
2202. The COP of refrigerator working on a reversed Carnot cycle is-
T1/T2-T1
T2-T1/T1
T1-T2/T1
T2/T2-T1
2203. A vapour absorption refrigerator uses ........ us a refrigerant.
water
ammonia
freon
aqua-ammonia
2204. The COP of a heat pump working on a reversed Carnot cycle is-
T1/T2-T1
T2-T1/T1
T1-T2/T1
T2/T2-T1
2205. 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
2206. The subcooling in a refrigeration cycle-
does not alter COP
dreases COP
increases COP
none of these
2207. 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
2208. 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
2209. 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
2210. The superheating in a refrigeration cycle-
does not alter COP
decreases COP
increases COP
none of these
2211. The COP of a domestic refrigerator in comparison to domestic air conditioner will be--
same
less
more
unpredictable
2212. In vapour compressor is used—
a vapour compressor is used
a liquid pump is used
both a vapour compressor and a liquid pump is used
none of above
2213. 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
2214. 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
2215. 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
2216. In a domestic vapour compression refrigerator, the refrigerant commonly used is-
CO
Ammonia
R-12
all of these
2217. The COP of the vapour absorption cycle as compared to vapour compression cycle is—
higher
lower
same
none of above.
2218. An ordinary passenger aircraft requires a cooling system of capacity-
2 TR
4TR
8TR
10 TR
2219. The pipe material for the refrigetors sing ammonia as refrigerant should be of--
copper
cast steel or wrought iron
brass
aluminium
2220. The highest temperature during the cycle in a vapour compression system r occurs after evaporation.
True
False