MCQ
61. The COP of the vapour absorption cycle as compared to vapour compression cycle is—
higher
lower
same
none of above.
62. 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
63. The superheating in a refrigeration cycle-
does not alter COP
decreases COP
increases COP
none of these
64. The subcooling in a refrigeration cycle-
does not alter COP
dreases COP
increases COP
none of these
65. The COP of refrigerator working on a reversed Carnot cycle is-
T1/T2-T1
T2-T1/T1
T1-T2/T1
T2/T2-T1
66. 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
Himalay Sen Sir
মেকানিক্যাল ইঞ্জিনিয়ারিং MCQ
mechanical mcq
মেকানিক্যাল বিগত সালের প্রশ্ন সমাধান
রেফ্রিজারেশন mcq
ব্যাখ্যা: here ambient air will be at 350 K
Air after cooling effect 300K (air temp ine as i act as refrigerant
Air before cooling effect = 250K
Cooling effect (300-250)=50kJ/kg
Total heat rejected to atm =(350-250) =100kJ/kg
Hence work done by compressor=Total heat rejected-Cooling effect
100-50=50kj/kg
67. Which of the following refrigerant has the lowest freezing point?
R-11
R-22
R-12
Ammoma
68. The capacity of a domestic refrigerator is the range of-
0.1 to 0.3 TR
1 to 3 TR
3 to 5 TR
5 to 7 TR
69. The highest temperature during the cycle in a vapour compression system r occurs after evaporation.
True
False
70. An ordinary passenger aircraft requires a cooling system of capacity-
2 TR
4TR
8TR
10 TR
71. 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. A vapour absorption refrigerator uses ........ us a refrigerant.
water
ammonia
freon
aqua-ammonia
73. 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
74. 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
75. 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
76. The temperature of ammonia after compression in a vapour compression system is-
20 to 50°C
70 to 100°C
50 to 70°C
none of these
77. 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
78. A refrigerant with the highest critical pressure is-
R-11
R-22
R-12
Ammonia
79. In a domestic vapour compression refrigerator, the refrigerant commonly used is-
CO
Ammonia
R-12
all of these
80. The pipe material for the refrigetors sing ammonia as refrigerant should be of--
copper
cast steel or wrought iron
brass
aluminium