Chemical Engineering - Heat Transfer

31. 

The characteristic dimensionless groups for heat transfer to a fluid flowing through a pipe in laminar flow are

A. Re.Gz
B. Nu, Pr
C. Nu, Pr, Re
D. Nu, Gz

Answer: Option D

Explanation:

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32. 

Heat transfer rate described by Fourier's law will decrease, if the __________ increases.

A. thermal conductivity
B. thickness
C. temperature difference
D. heat transfer area

Answer: Option B

Explanation:

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33. 

A black body does not __________ radiation.

A. absorb or emit
B. refract
C. reflect
D. both(b) & (c)

Answer: Option D

Explanation:

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34. 

The capacity of double-effect evaporator is less than half of the capacity of two single effects, each of which is operating over same terminal temperature difference, when the

A. solution has an elevation of boiling point.
B. evaporators operate under vacuum.
C. evaporators opreate at atmospheric pressure.
D. none of these.

Answer: Option A

Explanation:

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35. 

Peclet number (Pe) is given by

A. Pe = Re.Pr
B. Pe = Re/Pr
C. Pe = Pr/Re
D. Pe = Nu.Re

Answer: Option A

Explanation:

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