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I Dust Accumulation on Fan Blades and Elsewhere

  1. Jul 11, 2018 #1
    Any cooling fan, as well as any objects that it cools, will invariably become choked with fine dust after a time. But this seems quite surprising considering that all the dust is being accumulated on surfaces that are exposed to large currents of moving air.

    I've learned of two possible reasons:

    1) The boundary layer of air attached to the surface does not move and all dust can easily collect there.
    2) Static charge on the surfaces will hold dust.

    Reason #2 does not seem plausible because dust can collect on grounded heat sinks in computers.

    I suppose that the true reason is #1.

    Any comments?

    Whatever the reason, there seems no way to prevent it other than filtering the air.
     
  2. jcsd
  3. Jul 11, 2018 #2

    Grinkle

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    Gold Member

    I don't think that is sound logic. If you can remove all charge from the blades and they still get just as dusty, I think that would cast doubt on reason (2).
     
  4. Jul 11, 2018 #3
    I imagine van der Waals interactions are also important.
    The article linked below has a discussion on the forces and interactions that result in dust accumulation in microelectronics.
    https://www.tandfonline.com/doi/pdf/10.1080/02786828708959155
     
  5. Jul 12, 2018 #4
    Another option is to close the system from dirt-laden outside air, and use an enclosure cooler for heat removal.
     
  6. Jul 12, 2018 #5

    russ_watters

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    Staff: Mentor

    Often the dust is found on impact sites like the leading edge or low pressure or velocity zones.
     
  7. Jul 12, 2018 #6
    Dust can collect anywhere because of its ion charge and what the dust is composed of. I believe #2 is most likely correct and really discount #1
     
  8. Jul 15, 2018 #7
    Also, for fan blades and things with edges, take a look at house dust under a microscope. Some dust is more like filaments than particles. Those filaments can catch on edges and tiny irregularities. Combine that with static electricity caused by friction and you've got dust buildup. The lack of dust buildup on the bottoms of shelves, for example, is due to very low static electricity potential.
     
  9. Jul 15, 2018 #8

    Tom.G

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    Science Advisor

    In storm drains (water carrier rather than air), in heavy flows from the street through the grate, there is a build-up with the consistency of soft sandstone on the back wall of the drain. This appears where the entering water impacts the back wall and deposits sediments. Eventually the build-up impedes drainage. When the water gets too deep, one of us in the neighborhood will remove the access cover and use a steel pole to break up the deposit. This supports the OP's reason No. 1, for at least this situation.

    Cheers,
    Tom
     
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