Chemical Engineering - Heat Transfer

16. 

In Biot number, the characteristic length used is the ratio of the __________ of the solid.

A. volume to surface area
B. perimeter to surface area
C. surface area to volume
D. surface area to perimeter

Answer: Option A

Explanation:

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17. 

Which of the following is the most widely used heat insulating material for pipelines carrying steam ?

A. Tar dolomite bricks followed by asbestos.
B. Fireclay refractory followed by aluminium sheet.
C. Cotton followed by aluminium foil.
D. 85% magnesia cement and glass wool.

Answer: Option D

Explanation:

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18. 

Heat transfer co-efficient equation for forced convection, Nu = 0.023 Re0.8 . Prn, is not valid, if the value of

A. n = 0.4 is used for heating.
B. n = 0.3 is used for cooling.
C. Reynolds number for the flow involved is > 10000.
D. Reynolds number for the flow involved is < 2100.

Answer: Option D

Explanation:

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19. 

Which is the best tube arrangement (in a shell and tube heat exchanger) if the fluids are clean and non-fouling ?

A. Square pitch
B. Triangular pitch
C. Diagonal square pitch
D. None of these

Answer: Option B

Explanation:

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20. 

In case of a multipass shell and tube heat exchanger, the temperature drop in the fluid

A. is inversely proportional to the resistance across which the drop occurs.
B. and the wall are proportional to individual resistances.
C. and the wall is not related.
D. none of these.

Answer: Option B

Explanation:

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