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

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

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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

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

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