Explore topic-wise MCQs in Mechanical Engineering Questions.

This section includes 94 Mcqs, each offering curated multiple-choice questions to sharpen your Mechanical Engineering Questions knowledge and support exam preparation. Choose a topic below to get started.

51.

Rating of a domestic refrigerator is of the order of__________________?
A. 0.1 ton
B. 5 tons
C. 10 tons
D. 40 tons
E. 100 tons
Answer» B. 5 tons
Discussion
52.

The domestic refrigerator uses following type of compressor ____________________?
A. centrifugal
B. axial
C. miniature sealed unit
D. piston type reciprocating
E. none of the above
Answer» E. none of the above
Discussion
53.

Refrigeration in aeroplanes usually employs the following refrigerant___________________?
A. Co2
B. Freon-11
C. Freon-22
D. Air
E. none of the above
Answer» E. none of the above
Discussion
54.

In a refrigeration cycle, the flow of refrigerant is controlled by___________________?
A. compressor
B. condenser
C. evaporator
D. expansion valve
E. all of the above
Answer» E. all of the above
Discussion
55.

Condensing temperature in a refrigerator is the temperature_________________?
A. of cooling medium
B. of freezing zone
C. of evaporator
D. at which refrigerant gas becomes liquid
E. condensing temperature of ice
Answer» E. condensing temperature of ice
Discussion
56.

The lower horizontal line of the refrigeration cycle plotted on pressure-enthalpy-diagram represents_____________________?
A. condensation of the refrigerant vapour
B. evaporation of the refrigerant liquid
C. compression of the refrigerant vapour
D. metering of the refrigerant liquid
E. none of the above
Answer» C. compression of the refrigerant vapour
Discussion
57.

Formation of frost on evaporator in refrigerator ________________?
A. results in loss of heat due to poor heat transfer
B. increases heat transfer rate
C. is immaterial
D. can be avoided by proper design
E. decreases compressor power
Answer» B. increases heat transfer rate
Discussion
58.

In a refrigeration system, heat absorbed in comparison to heat rejected is_________________?
A. more
B. less
C. same
D. more for small capacity and less for high capacity
E. less for small capacity and more for high capacity
Answer» C. same
Discussion
59.

In vapour compression cycle using NH3 as refrigerant, initial charge is filled at_________________?
A. suction of compressor
B. delivery of compressor
C. high pressure side close to receiver
D. low pressure side near receiver
E. anywhere in the cycle
Answer» D. low pressure side near receiver
Discussion
60.

Super heating in a refrigeration cycle __________________?
A. increases COP
B. decreases COP
C. COP remains unaltered
D. other factors decide COP
E. unpredictable
Answer» C. COP remains unaltered
Discussion
61.

Freon group of refrigerants are___________________?
A. inflammable
B. toxic
C. non-inflammable and toxic
D. non-toxic and inflammable
E. non-toxic and non-inflammable
Answer» F.
Discussion
62.

Moisture in freon refrigeration system causes________________?
A. ineffective refrigeration
B. high power consumption
C. freezing automatic regulating valve
D. corrosion of whole system
E. breakdown of refrigerant
Answer» D. corrosion of whole system
Discussion
63.

The leaks in a refrigeration system using Freon are detected by____________________?
A. halide torch which on detection produces greenish flame lighting
B. sulphur sticks which on detection gives white smoke
C. using reagents
D. smelling
E. sensing reduction in pressure
Answer» B. sulphur sticks which on detection gives white smoke
Discussion
64.

The C.O.P of a refrigeration cycle with increase in evaporator temperature, keeping condenser temperature constant, will______________________?
A. increase
B. decrease
C. remain unaffected
D. may increase or decrease depending on the type of refrigerant used
E. unpredictable
Answer» B. decrease
Discussion
65.

On the pressure-enthalpy diagram, condensation and desuperheating is represented by a horizontal line because the process ________________?
A. involves no change in volume
B. takes place at constant temperature
C. takes place at constant entropy
D. takes place at constant enthalpy
E. takes place at constant pressure
Answer» F.
Discussion
66.

For obtaining high COP, the pressure range of compressor should be_______________?
A. high
B. low
C. optimum
D. any value
E. there is no such criterion
Answer» C. optimum
Discussion
67.

Most of the domestic refrigerators work on the following refrigeration system _________________?
A. vapour compression
B. vapour absorption
C. carnot cycle
D. electrolux refrigerator
E. dual cycle
Answer» B. vapour absorption
Discussion
68.

Reducing suction pressure in refrigeration cycle_________________?
A. lowers evaporation temperature
B. increases power required per ton of refrigeration
C. lowers compressor capacity because vapour is lighter
D. reduces weight displaced by piston
E. all of the above
Answer» F.
Discussion
69.

The suction pipe diameter of refrigerating unit compressor in comparison to delivery side is_________________?
A. bigger
B. smaller
C. equal
D. smaller/bigger depending on capacity
E. unpredictable
Answer» B. smaller
Discussion
70.

The advantage of dry compression is that________________?
A. it permits higher speeds to be used
B. it permits complete evaporation in the evaporator
C. it results in high volumetirc and mechanical efficiency
D. all of the above
E. none of the above
Answer» E. none of the above
Discussion
71.

Under-cooling in a refrigeration cycle_________________?
A. increases COP
B. decreases COF
C. COP remains unaltered
D. other factors decide COP
E. unperdictable
Answer» B. decreases COF
Discussion
72.

One ton of the refrigeration is_________________?
A. the standard unit used in refrigeration problems
B. the cooling effect produced by melting 1 ton of ice
C. the refrigeration effect to freeze 1 ton of water at 0°C into ice at 0°C in 24 hours
D. the refrigeration effect to produce 1 ton of ice at NTP conditions
E. the refrigeration effect to produce 1 ton of ice in 1 hour time
Answer» D. the refrigeration effect to produce 1 ton of ice at NTP conditions
Discussion
73.

For proper refrigeration in a cabinet, if the temperature and vapour pressure difference between cabinet and atmosphere is high, then_________________?
A. bigger cabinet should be used
B. smaller cabinet should be used
C. perfectly tight vapour seal should be used
D. refrigerant with lower evaporation temperature should be used
E. refrigerant with high boiling point must be used
Answer» D. refrigerant with lower evaporation temperature should be used
Discussion
74.

Short horizontal lines on pressure-enthalpy chart show__________________?
A. constant pressure lines
B. constant temperature lines
C. constant total heat lines
D. constant entropy lines
E. constant volume lines
Answer» B. constant temperature lines
Discussion
75.

Mass flow ratio of NH3 in comparison to Freon-12 for same refrigeration load and same temperature limits is of the order of___________________?
A. 1 : 1
B. 1 : 9
C. 9 : 1
D. 1 : 3
E. 3 : 1
Answer» C. 9 : 1
Discussion
76.

Ammonia is __________________?
A. non-toxic
B. non-inflammable
C. toxic and non-inflammable
D. highly toxic and inflammable
E. none of the above
Answer» E. none of the above
Discussion
77.

Where does the lowest temperature occur in a vapour compression cycle ?
A. condenser
B. evaporator
C. compressor
D. expansion valve
E. receiver
Answer» C. compressor
Discussion
78.

The change in evaporator temperature in a refrigeration cycle, as compared to change in condenser temperature, influences the value of C.O.P_____________________?
A. more
B. less
C. equally
D. unpredictable
E. none of the above
Answer» B. less
Discussion
79.

Cooling water is required for following equipment in ammonia absorption plant__________________?
A. condenser
B. evaporator
C. absorber
D. condenser and absorber
E. condenser, absorber and separator (rectifier)
Answer» F.
Discussion
80.

The evolution of heat of solution takes place in ammonia absorption plant when _____________________?
A. ammonia vapour goes into solution
B. ammonia vapour is driven out of solution
C. lithium bromide mixes with ammonia
D. weak solution mixes with strong solution
E. lithium bromide is driven out of solution
Answer» B. ammonia vapour is driven out of solution
Discussion
81.

The refrigeration effect in a dry evaporator compared to flooded evaporator in a similar plant is_________________?
A. same
B. more
C. less
D. more or less depending on ambient conditions
E. unpredictable
Answer» D. more or less depending on ambient conditions
Discussion
82.

The COP of a vapor compression plant in comparison to vapor absorption plant is ________________?
A. more
B. less
C. same
D. more/less depending on size of plant
E. unpredictable
Answer» B. less
Discussion
83.

Which of the following refrigerants has lowest freezing point_______________?
A. Freon-12
B. NH3
C. C02
D. Freon-22
E. S02
Answer» E. S02
Discussion
84.

The C.O.P. of a refrigeration cycle with lowering of condenser temperature, keeping the evaporator temperature constant, will__________________?
A. increase
B. decrease
C. may increase or decrease depending on the type of refrigerant used
D. remain unaffected
E. unpredictable
Answer» B. decrease
Discussion
85.

The general rule for rating refrigeration systems (excepting for C02 system) is to approximate following h.p. per ton of refrigeration__________________?
A. 0.1 to 0.5 h.p. per ton of refrigeration
B. 0.5 to 0.8 h.p. per ton of refrigeration
C. 1 to 2 h.p. per ton of refrigeration
D. 2 to 5 h.p. per ton of refrigeration
E. 5 to 10 h.p. per ton refrigeration
Answer» D. 2 to 5 h.p. per ton of refrigeration
Discussion
86.

Absorption system normally uses the following refrigerant___________________?
A. Freon-11
B. Freon-22
C. C02
D. S02
E. ammonia
Answer» F.
Discussion
87.

In a vapor compression cycle, the refrigerant immediately after expansion valve is___________________?
A. liquid
B. sub-cooled liquid
C. saturated liquid
D. wet vapour
E. dry vapour
Answer» E. dry vapour
Discussion
88.

The coefficient of performance is the ratio of the refrigerant effect to the_________________?
A. heat of compression
B. work done by compressor
C. enthalpy increase in compressor
D. all of the above
E. none of the above
Answer» E. none of the above
Discussion
89.

Choose the wrong statement ?
A. Temperature of medium being cooled must be below that of the evaporator
B. Refrigerant leaves the condenser as liquid
C. All solar thermally operated absorption systems are capable only of intermittent operation
D. frost on evaporator reduces heat transfer
E. refrigerant is circulated in a refrigeration system to transfer heat
Answer» B. Refrigerant leaves the condenser as liquid
Discussion
90.

Choose the correct statement?
A. A refrigerant should have low latent heat
B. If operating temperature of system is low, then refrigerant with low boiling point should be used
C. Precooling and subcooling bf refrigerant are same
D. Superheat and sensible heat of a. refrigerant are same
E. Refrigerant is inside the lubes in case of a direct-expansion chiller
Answer» C. Precooling and subcooling bf refrigerant are same
Discussion
91.

Highest temperature encountered in refrigeration cycle should be________________?
A. near critical temperature of refrigerant
B. above critical temperature
C. at critica. temperature
D. much below critical temperature
E. could be anywhere
Answer» E. could be anywhere
Discussion
92.

Pick up the incorrect statement?
A. lithium bromide used in vapour absorption cycle is nonvolatile
B. lithium bromide plant can’t operate below 0°C
C. a separator is used in lithium bromide plant to remove the unwanted water vapour by condensing
D. concentration of solution coming out of lithium bromide generator is more in comparison to that entering the generator
E. weak solution in liquid heat exchanger gives up heat to the strong solution
Answer» D. concentration of solution coming out of lithium bromide generator is more in comparison to that entering the generator
Discussion
93.

A certain refrigerating system has a normal operating suction pressure of 10 kg/cm gauge and condensing pressure of about 67 kg/cm. The refrigerant used is________________?
A. Ammonia
B. Carbon dioxide
C. Freon
D. Brine
E. Hydrocarbon refrigerant
Answer» C. Freon
Discussion
94.

Vertical lines on pressure-enthalpy chart show constant_______________?
A. pressure lines
B. temperature lines
C. total heat lines
D. entropy lines
E. volume lines
Answer» D. entropy lines
Discussion