Static pressure and airflow at reduced fan speeds

  1. This is probably a stupid question but I've been going around in circles for a while now and have gotten myself completely confused.

    I have a fan and a pump, with performance charts (static pressure vs. air flow) for both. I need to try and determine flow rates for each device when run at reduced speeds.

    The fan/pump will be pulling a gas flow through a small tube, and exhausting to atmosphere. I know that's not the right way to use a fan, but that's what I'm stuck with right now. I can measure the pressure at the fan/pump inlet while running at different voltages.

    Searching around the internet, I found that air flow is linearly proportional to fan speed and static pressure is proportional to fan speed squared.

    So I'm guessing that if I'm at half the fan speed I should be at a quarter (.52) of the static pressure. I can measure the pressure, multiply by 4 and look it up on the chart. Then take the corresponding air flow and knock it in half to get the actual flow rate.

    That's a complete guess. If anyone can steer me in the right direction, I would appreciate it because I'm really stuck here. Thanks for your help.

  2. jcsd
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