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Chemical Engineering - Heat Transfer - Discussion

Discussion Forum : Heat Transfer - Section 1 (Q.No. 38)
Heat Transfer
38.
Pick out the wrong statement.
In case of heat transfer by purely forced convection, GR/Re2 ≤ 1.
The equivalent diameter of heat transfer for a duct of square cross-section (having each side as 'x') is equal to 4x.
Distillation process is not the same as evaporation.
The effectiveness of nucleate boiling depends basically on the ease with which the bubbles are formed and detached from the heating surface.
Answer: Option
Explanation:
No answer description is available. Let's discuss.
Discussion:
4 comments Page 1 of 1.
Gautam said:   1 decade ago
Equivalent dia. For a duct of square cross section= 4* (cross section area/wetted perimeter).

E.D = 4* (x2/4x).

E.D = x.
Danish said:   8 years ago
Gr is the grash of the number right? Then why it comes under forced convection?

It comes only under the free convection.
Danish said:   8 years ago
Please, explain the 1st option.
Arindam said:   8 years ago
Gr is Grashof number. The ratio Gr/Re2 determines the nature of convection. If it is <<1 then Re is higher and controlling then natural convection. Otherwise Gr higher and dominating, so forced. If it is equal then both have to be considered.
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