Process Equipment and Plant Design
In a double pipe (concentric) heat exchanger, the hydraulic radius for heat transfer (for a fluid flowing through the annulus) would be

Less than that for fluid flow
More than that for fluid flow
Same as that for fluid flow
D₂ - D₁ (D₁ and D₂ are I.D. of inner and outer pipes respectively)

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Process Equipment and Plant Design
A forced circulation long tube vertical evaporator as compared to the natural circulation evaporator

Both B & C
Employs a centrifugal pump placed between external downtake from vapor drum and inlet to tube bundle
Employs high velocity, high heat transfer rate and less heating surface requirement
Is economical in operation

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Process Equipment and Plant Design
Pick out the wrong statement pertaining to the design of a basket type evaporator.

The tube bundle is suspended on bracket
It is used for high viscosity liquor having large rate of scaling
There is no central downtake
Downtake is formed by the annular space between the bundle and the shell

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