> > Actually, not all fans are set up to suck out of the box.
Ha! > Blowing in works better for heat transfer (you're pushing cold dense air, > rather than sucking warm undense air).. Most test equipment uses the "suck > in through a filter and pressurize the box" design approach. I think PCs > evolved the other way because the single fan was in the power supply, and > you didn't want to blow hot air, preheated by the power supply, through the > rest of the system. So it is set up as an "exhaust from PS box" fan. > > And a lot of higher performance PCs (like the Dell sitting on my desk) use > centrifugal fans (with variable speed, to boot) > > Jim Lux > > -----Original Message----- > From: [email protected] [mailto:[email protected]] On > Behalf Of Daniel Pfenniger > Sent: Wednesday, June 06, 2012 10:33 AM > To: [email protected] > Cc: Beowulf Mailing List > Subject: Re: [Beowulf] Desktop fan reccommendation > > [email protected] wrote: > > > >> The Dyson bladeless and silent fans are based om a different > >> principle, a cylindrical thin air layer carries along the inner air > >> column, the air flow is then laminar ( > http://www.dyson.com/store/fans.asp). > > > > Which is not good if your trying to cool stuff..... > > Well, the fans we are discussing expel air *out* of the box so the heat > carried by the air doesn't care about the downstream laminar or turbulent > state of the airflow. > > However noise generation does depend on the airflow state, since the > acoustic power is proportional to the 8th power of the turbulence eddy > speed (Lighthill 1952, 1954). This is why jet planes are noisy, as their > turbulence is almost sonic. The airplane or helicopter propeller tips, or > the fan blade ends move closer to the sound speed, so most of the sound is > generated there. > > The conclusion is that to keep a computer quiet one has advantage to use > large fans rotating at low speed. For the same air/heat output one gets > much less noise, especially if the airflow is laminar. > > > Dan > > > > > > > _______________________________________________ > Beowulf mailing list, [email protected] sponsored by Penguin Computing > To change your subscription (digest mode or unsubscribe) visit > http://www.beowulf.org/mailman/listinfo/beowulf > _______________________________________________ > Beowulf mailing list, [email protected] sponsored by Penguin Computing > To change your subscription (digest mode or unsubscribe) visit > http://www.beowulf.org/mailman/listinfo/beowulf > -- - - - - - - - - - - - - - - - - - - - - - Nathan Moore Winona, MN - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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