Design the system so that the total pressure drop does not exceed 10% of the system pressure. The system pressure being the pressure at the top of the column. The system consists of all piping and fittings (including pipe entrance losses) AND THE CONDENSER that is between the column and the vacuum source (vacuum pump, ejectors or combination). Size the pipe and the remainder is for the condenser. I've seen a condenser pressure drop specified for 1 mmHg for a deep vacuum system. <br>
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You have plenty of pressure to work with (4 psia = about 207 mm Hg abs = 207 Torr). As a matter of fact, some engineers would kill for that much pressure to work with!<br>
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Phil Leckner<br>
First Content Manager<br>
The Chemical Engineers' Resource Page