Chemical Engineering - Heat Transfer

26. 

Pick out the wrong statement.

A. Orifice baffles are never used in a shell and tube heat exchanger.
B. Pressure drop on the shell side of a heat exchanger depends upon tube pitch also.
C. In a horizontal tube evaporator, surface blanketing by air is avoided.
D. Split ring type and pull through type floating heads are two commonly used floating heads is heat exchangers.

Answer: Option A

Explanation:

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27. 

Convective heat transfer co-efficient in case of fluid flowing in tubes is not affected by the tube length/diameter ratio, if the flow is in the __________ zone.

A. laminar
B. transition
C. both 'a' & 'b'
D. highly turbulent

Answer: Option D

Explanation:

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28. 

The actual temperature drop across the heating surface in an evaporator depends on the

A. feed.
B. depth of liquid over heating surface.
C. pressure difference between steam chest and vapour space.
D. all (a), (b) and (c).

Answer: Option D

Explanation:

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29. 

Which of the following is not used as a medium for high temperature heating ?

A. Dowtherm
B. mercury
C. liquid metal (e.g. molten sodium)
D. fused salts (e.g., an eutectic mixture of 53% KNO3, 40% NaNO2and 7% NaNO3)

Answer: Option B

Explanation:

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30. 

Presence of a non-condensing gas in a condensing vapour

A. increases the rate of condensation.
B. decreases thermal resistance.
C. is desirable to increase the film co-efficient.
D. none of these.

Answer: Option D

Explanation:

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