mechanical engineering MCQs – Page 213

Practise multiple-choice questions from mechanical engineering for competitive examinations and subject revision. Review each marked answer and report any item that may be outdated or unclear.

mechanical engineering Mcqs

1. compressors gas turbines and jet engines 2. theory of machines 3. nuclear power plants 4. engineering materials 5. strength of materials mechanical engineering 6. thermodynamics 7. heat transfer 8. i c engines 9. steam boilers engines nozzles and turbines 10. engineering mechanics 11. fluid mechanics mechanical engineering 12. production technology 13. machine design 14. hydraulic machines 15. workshop technology 16. refrigeration and air conditioning

4241. The COP of a vapor compression plant in comparison to vapor absorption plant is ________________?
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A. same

B. unpredictable

C. more/less depending on size of plant

D. less

E. more

4242. The moisture in a refrigerant is removed by___________________?
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A. expansion valve

B. driers

C. dehumidifier

D. evaporator

E. safety relief valve

4243. The coefficient of performance is the ratio of the refrigerant effect to the_________________?
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A. none of the above

B. enthalpy increase in compressor

C. all of the above

D. work done by compressor

E. heat of compression

4244. In a flooded evaporator refrigerator, an accumulator at suction of compressor is used to___________________?
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A. detect liquid in vapour

B. increase refrigeration effect

C. collect liquid refrigerant and prevent it from going to compressor

D. superheat the vapour

E. collect vapours

4245. The refrigerant for a refrigerator should have ___________________?
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A. high sensible heat

B. high total heat

C. high latent heat

D. low sensible heat

E. low latent heat

4246. Reducing suction pressure in refrigeration cycle_________________?
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A. lowers evaporation temperature

B. lowers compressor capacity because vapour is lighter

C. increases power required per ton of refrigeration

D. all of the above

E. reduces weight displaced by piston

4247. Critical pressure of a liquid is the pressure_________________?
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A. above which liquid becomes vapour

B. at which all the three phases exist together

C. above which liquid becomes solid

D. above which liquid becomes gas

E. above which liquid will remain liquid

4248. Freon group of refrigerants are___________________?
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A. non-toxic and inflammable

B. inflammable

C. toxic

D. non-toxic and non-inflammable

E. non-inflammable and toxic

4249. The vapor pressure of refrigerant should be_________________?
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A. could be anything

B. lower than atmospheric pressure

C. higher than atmospheric pressure

D. none of the above

E. equal to atmospheric pressure

4250. Mass flow ratio of NH3 in comparison to Freon-12 for same refrigeration load and same temperature limits is of the order of___________________?
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A. 1:01

B. 9:01

C. 1 : 9

D. 1:03

E. 3:01

4251. Where does the lowest temperature occur in a vapour compression cycle ?
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A. condenser

B. evaporator

C. receiver

D. expansion valve

E. compressor

4252. In a refrigeration system, heat absorbed in comparison to heat rejected is_________________?
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A. more

B. less for small capacity and more for high capacity

C. less

D. more for small capacity and less for high capacity

E. same

4253. Choose the wrong statement ?
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A. Temperature of medium being cooled must be below that of the evaporator

B. frost on evaporator reduces heat transfer

C. refrigerant is circulated in a refrigeration system to transfer heat

D. All solar thermally operated absorption systems are capable only of intermittent operation

E. Refrigerant leaves the condenser as liquid

4254. Which of the following is not a desirable property of a refrigerant_________________?
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A. non-inflammable

B. low boiling point

C. good electrical conductor

D. high triiscibility with oil

E. large latent heat

4255. At lower temperatures and pressures, the latent heat of vaporisation of a refrigerant_________________?
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A. remains same

B. depends on other factors

C. none of the above

D. decreases

E. increases

4256. In a vapor compression cycle, the refrigerant immediately after expansion valve is___________________?
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A. wet vapour

B. saturated liquid

C. liquid

D. dry vapour

E. sub-cooled liquid

4257. Pick up the incorrect statement?
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A. weak solution in liquid heat exchanger gives up heat to the strong solution

B. lithium bromide plant cant operate below 0C

C. lithium bromide used in vapour absorption cycle is nonvolatile

D. concentration of solution coming out of lithium bromide generator is more in comparison to that entering the generator

E. a separator is used in lithium bromide plant to remove the unwanted water vapour by condensing

4258. Formation of frost on evaporator in refrigerator ________________?
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A. decreases compressor power

B. increases heat transfer rate

C. is immaterial

D. can be avoided by proper design

E. results in loss of heat due to poor heat transfer

4259. Absorption system normally uses the following refrigerant___________________?
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A. Freon-22

B. C02

C. ammonia

D. Freon-11

E. S02

4260. Choose the correct statement?
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A. Superheat and sensible heat of a. refrigerant are same

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. Refrigerant is inside the lubes in case of a direct-expansion chiller

E. A refrigerant should have low latent heat

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