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How to size pumps in pressurized systems?

atomic
atomic Member Posts: 9
in THE MAIN WALL
When sizing a circulator for a pressurized system, how do you figure the total head ? I have a flat plate heat exchanger with 14 ft of head @90 GPM, and a short run of 3" pipe. The system pressure is 15 PSI. Just pulling numbers off the pump curves doesn't seem to allow for the system being pressurized. Is there a correction factor, or a rule of thumb to go by? Or is the pump curve the best way to do it? Thanks for any light you're able to shed on this subject.

Comments

  • Mark Eatherton
    Mark Eatherton Member Posts: 5,852
    Fill pressure has little to do with pump sizing in a closed loop system...

    Fill pressure has to do with overcoming the vertical height of the building, and maintaining a required minimum inlet pressure to the pump. Period.



    A pump is nothing more than a pressure differential machine. It generates pressure between its inlet and outlet flanges. What the piping system does with that pressure differential is dependent upon size of pipe, pressure drop of connected devices etc.



    In order to calculate how many GPM a given pump will produce, you have to go through the iteration of calculating flow, and associated pressure drop. Pressure drop in a series circuit is additive. Once you have this number, you can go to the manufacturers performance curves and see what that particular pump is capable of producing. Make sure it is capable of producing slightly more pressure (head) than is needed, at the required flow (GPM) and you should be golden.



    ME

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