Chemical Engineering - Heat Transfer

21. 

A sphere of radius 'R1' is enclosed in a sphere of radius 'R2'. The view (or shape) factor for radiative heat transfer of the outer sphere with respect to the inner sphere is

A. 0
B. R2/(R1+R2)
C. 1
D. (R1/R2)2

Answer: Option B

Explanation:

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22. 

For a laminar flow of fluid in a circular tube, 'h1' is the convective heat transfer co-efficient at velocity 'V1'. If the velocity is reduced by half and assuming the fluid properties are constant, the new convective heat transfer co-efficient is

A. 1.26 h1
B. 0.794 h1
C. 0.574 h1
D. 1.741 h1

Answer: Option B

Explanation:

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23. 

The main purpose of providing fins on heat transfer surface is to increase the

A. temperature gradient.
B. mechanical strength of the equipment.
C. heat transfer area.
D. heat transfer co-efficient.

Answer: Option C

Explanation:

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24. 

A BTU/hr.ft.2 °F is equal to

A. 1 kcal/hr. m2°C.
B. 4.88 kcal/hr. m.2°C.
C. 1 kcal/hr. m2.°K.
D. none of these.

Answer: Option B

Explanation:

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25. 

Which of the following has the lowest Prandtl number ?

A. Molten sodium (a coolant used in fast breeder reactor)
B. Water
C. Transformer oil
D. Dilute H2SO4

Answer: Option A

Explanation:

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