Anonymous asked in Science & MathematicsEngineering · 1 decade ago

Calculating CFM from Air velocity?

I'm building an air flow bench to test internal combustion engine components and people typically use pitot tubes to measure water pressure and then use that pressure to calculate air velocity, and then from that calculate CFM. However, Can I just use an air velocity meter instead? Then from that calculate CFM?


4 Answers

  • 1 decade ago
    Favorite Answer

    You also need to know if you want actual cubic feet per minute (ACFM) or standard cubic feet per minute (SCFM).

    ACFM is based on the actual pressure and temperature of the air flowing in the duct. SCFM is corrected to standard conditions which are typically 14.7 psia and 60 degs F.

    I think the idea of taking a velocity profile across the duct is a good idea regardless of the method you use to measure the flow rate.

  • 1 decade ago

    Sure, you can calculate CFM from air meter velocity, but you have two things to watch out for. 1) Where do you put the air meter? I don't know how big your duct is, but velocity can vary in different parts of a duct. 2) If you are using an electronic, resistance type air meter it won't have this effect, but if you put in one of the propeller types in the ductwork, you can affect the dP in the system.

    I think people like to use the pitot tube arrangement because it is cheap and reliable.

  • Anonymous
    1 decade ago

    Some of you that are mechanically inclined may think of cars and their air flow sensor that monitors the air mix in your fuel injection systems. Others may think of Oxygen flow meters that are used on oxygen tanks in many older patient homes. Did you realize that major corporations also use different types of meters to monitor gasses?

  • Anonymous
    4 years ago

    Take the number of cubic feet that flows past a point in a number of minutes, and divide the two. .

Still have questions? Get your answers by asking now.