Process Equipment and Plant Design
In a shell and tube heat exchanger for a given heat transfer surface area, smaller diameter tubes are favoured as compared to larger diameter ones ; because the smaller diameter tubes

None of these
Are easier to clean
Are less prone to fouling
Can be fitted into a smaller shell diameter hence the cost of the heat exchanger would be less

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Process Equipment and Plant Design
A stuffing box is used for

Facilitating smooth opening and closing of a valve
Absorbing the contraction/expansion of pipeline due to temperature changes
Prevention of fluid leakage around moving parts
Reducing the resistance of fluid flow

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Process Equipment and Plant Design
Pick out the wrong statement about the design of a sieve plate column.

Minimum recommended downcomer residence time for the disengagement of entrained vapour is the same for both foaming and non-foaming liquids, which is about 20 seconds
Width of the calming section provided at the inlet and outlet sides of the plate is 75 mm for column diameter below 1.5 metres and 100 mm for larger diameter columns
An increased weir height improves the tray efficiency at the cost of high plate pressure drop; optimum wear height being 40-90 mm for column pressure above atmospheric and 6-12 mm for vacuum columns
For segmental downcomers, the chord length is 60-80% of the column diameter. An initial value of downcomer area of 12% is taken in the design

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