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

More 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
Less than that for fluid flow

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Process Equipment and Plant Design
Pick out the wrong statement pertaining to shell and tube heat exchanger.

Baffles are supported independently of the tubes by tie rods and positioned by spacers
Tie rods are fixed at one end in the tube sheet by making blind holes and the minimum number of tie rods is 4 with at least 10 mm diameter
Clearance between shell & baffles and between tube & baffles should be minimum to avoid by-passing of the fluid, but it should be enough to permit the removal of tube bundle
Bracket supports are used for horizontal shell, while saddle support is used for vertical shell

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Process Equipment and Plant Design
The centre to centre distance between two consecutive baffles in a shell and tube heat exchanger is called the baffle pitch or baffle spacing, which is more than 1/5th the I.D. of the shell. Which of the following is not a function of the baffles?

To provide support to the tube bundle
To increase the tube side heat transfer co-efficient by inducing turbulence
To increase the residence time of shell side fluid
To reduce the induced vibration in the tubes

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