Chemical Engineering - Heat Transfer

1. 

The critical radius 'r' of insulation on a pipe is given by

A. r = 2k/h
B. r = k/h
C. r = k/2h
D. r = h/k

Answer: Option B

Explanation:

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2. 

As per Kirchoffs law, the ratio of the total radiating power to the absorptivity of a body depends on the

A. temperature of the body only.
B. wavelength of monochromatic radiation.
C. both (a) and (b).
D. nature of material of body.

Answer: Option A

Explanation:

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3. 

If the baffle spacing in a shell and tube heat exchanger increases, then the Reynolds number of the shell side fluid

A. remains unchanged.
B. increases.
C. increases or decreases depending on number of shell passes.
D. decreases.

Answer: Option D

Explanation:

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4. 

The heat transfer by radiation from a mild steel surface is to be reduced by reducing the emissivity of the surface. This can be best achieved by

A. painting the surface black.
B. painting the surface white (with aluminium paint).
C. giving the surface a mirror finish.
D. roughening the surface.

Answer: Option B

Explanation:

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5. 

__________ paint has the maximum absorption coefficient.

A. Black
B. Yellow
C. White
D. Grey

Answer: Option A

Explanation:

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