Chemical Engineering - Heat Transfer
Exercise :: Heat Transfer - Section 11
| 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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