Process Equipment and Plant Design
For a cylindrical shell, (subject to the thickness of uppermost course being more than the minimum for diaofthe tank in question), the thickness of the courses of shell

Remains same throughout
Decreases upwards
May decrease or increase upwards depending upon whether vacuum or positive pressure would be maintained inside the shell
Increases upwards

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

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