Heat Transfer MCQ Questions & Answers

21

Vacuum is generally maintained in the vapour space of an evaporator mainly to

A) Get economical temperature difference by using moderate pressure steam B) Facilitate forward feeding in multiple effect evaporation C) Concentrate heat sensitive materials D) Achieve very high concentration of the final product

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Answer & Solution

Answer: Option A

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22

Prandtl and Reynold's analogies are identical for Prandtl number value of

A) 0 B) 0.5 C) 1 D) 5

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Answer & Solution

Answer: Option C

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23

In case of vertical tube evaporator, with increase in liquor level, the overall heat transfer co-efficient

A) Increases B) Decreases C) Is not affected D) May increase or decrease; depends on the feed

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Answer & Solution

Answer: Option B

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24

Dietus-Boelter equation cannot be used for molten metals mainly due to its very low

A) Prandtl number B) Grashoff number C) Thermal conductivity D) Viscosity

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Answer & Solution

Answer: Option A

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25

A hollow sphere and a solid sphere of the same material and equal radii are heated to the same temperature. In this case,

A) The cooling rate will be the same for the two spheres and hence the two spheres will have equal temperatures at any instant B) Both the spheres will emit equal amount of radiation per unit time in the beginning C) Both will absorb equal amount of radiation from the surrounding in the beginning D) Both B & C

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Answer & Solution

Answer: Option D

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26

Pick out the wrong statement.

A) The emissivity of a surface decreases, if it gets corroded by atmospheric environment B) The emissivity of a surface increases with increase in surface roughness C) The emissivity of a polished surface is quite low D) The emissivity of a non-metallic surface decreases with increase in the temperature

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Answer & Solution

Answer: Option A

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27

An ejector is used to

A) Increase pressure B) Increase temperature C) Remove condensate D) None of these

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Answer & Solution

Answer: Option D

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28

An insulator should have

A) Low thermal conductivity B) High thermal conductivity C) Less resistance to heat flow D) A porous structure

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Answer & Solution

Answer: Option A

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29

Shell side pressure drop in a shell and tube heat exchanger does not depend upon the

A) Baffle spacing & shell diameter B) Tube diameter & pitch C) Viscosity, density & mass velocity of shell side fluid D) None of these

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Answer & Solution

Answer: Option D

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30

For large heat transfer area requirement, shell and tube heat exchanger is preferred, because it

A) Occupies smaller space B) Is more economical C) Is easy to operate and maintain D) All of the above

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Answer & Solution

Answer: Option D

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Heat Transfer MCQ Questions & Answers | Chemical Engineering