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Thread: Axial Flow Fan Selection

  1. #1
    Associate Engineer
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    Axial Flow Fan Selection

    We have a new dust-test chamber (approx 800mm x 800mm x 800mm) in which we would like test our industrial printers functioning in dusty environments. Currently we have 4 small axial fans (201m^3/hr and 4200rpm) mounted in a row which blow talcum powder around inside the cabinet after the operator inserts a measured amount, with the intention that the talc is blown into the printer interior to see what affect it has.
    However, we have found that the fans are not quite man enough to keep the talc in suspension. After running for a while the talc settles on the chamber floor and only a small amount remains in suspension. We are looking to use more powerful fans to keep all the talc in suspension.
    Would the approach be to upgrade to axial fans with a higher volumetric flow or should we rather be using fans with a higher speed? (or both?). Or should we possibly be using a different type of fan?
    Any suggestions would be very much appreciated.

  2. #2
    Principle Engineer Cragyon's Avatar
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    talc settles on the chamber floor


    Have you considered increasing agitation of the talc on the chamber floor with the fans you have? Increasing the velocity blowing on the settled talc mat be the solution.

  3. #3
    Associate Engineer
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    Thanks Cragyon. Currently the 4 fans are mounted along the one edge of the floor and blowing across the floor area to the other edge where we have a 45deg deflector pointing upwards in an attempt to lift the talc vertically again when it gets to the other side. It marginally works, but still needs a lot of improvement.
    I assume increasing the fan velocity would mean higher rpm and not higher m^3/hr?

  4. #4
    Principle Engineer Cragyon's Avatar
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    I assume increasing the fan velocity would mean higher rpm and not higher m^3/hr?


    No, the volume of air will also increase.

  5. #5
    Administrator Kelly Bramble's Avatar
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    Can you change the inlet of the air to the fans so that it draws from a low area were the talc powder wants to settle?

  6. #6
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    I am going to go way off the resrevation here with a totally different design suggestion (all are welcome to give their feedback or modification recommendations on this).
    What I would suggest is a total chamber redesign that replaces the floor of your box with a lower chamber with porous material between this lower chamber and the upper test chamber and a fan input. The fan's power supply would then have a timer so that the fan would sequentially briefly turn on to lift the talc and then shut off to allow the talc to settle. The porous (fabric?) floor would provide an even lifting flow across the entire chamber floor to lift the talc. One issue withn this is that the fan on period may need to be very short to prevent creating too much pressure in the chamber and minimize a reverse return flow through the membrane when the fan stops (or idles) when the power suts off.

    This is a variation on the system used in dry bulk material transfer systems to aerate the materia;l but, in that case the flow is continuous into the open flowing air duct transfer system.

  7. #7
    Associate Engineer
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    Many thanks for your replies Cragyon, Kelly & JAlberts..... you has given me food for thought to look at some alternatives.

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