Process Equipment and Plant Design
Ratio of tube length to shell diameter for a shell and tube heat exchanger is

4 : 1 to 8 : 1 for liquid-liquid exchanger
< 4 : 1 for gas-gas exchangers
8 : 1 to 12 : 1 for both liquid-liquid and gas-gas heat exchangers
Both B & C

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Process Equipment and Plant Design
Weep holes provided in the plates of a distillation column

All of these
Are normally located near the overflow weir so that any delivery of liquid during operation follows approximately the same path as the overflow fluid
Must be large enough (usually 1/4" to 5/8" dia) to prevent plugging but should not deliver excessive amount of fluid during operation
Facilitate draining out liquid from a tray when the unit is not in operation

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