[Beowulf] Desktop fan reccommendation

[Lux, Jim (337C)]

-----Original Message-----
From: Vincent Diepeveen [mailto:diep at xs4all.nl] 
Sent: Wednesday, June 06, 2012 10:46 AM
To: Lux, Jim (337C)
Cc: Daniel.Pfenniger at unige.ch; holway at th.physik.uni-frankfurt.de; Beowulf Mailing List
Subject: Re: [Beowulf] Desktop fan reccommendation


On Jun 6, 2012, at 7:28 PM, Lux, Jim (337C) wrote:
> And a lot of higher performance PCs (like the Dell sitting on my  
> desk) use centrifugal fans (with variable speed, to boot)
>

When i googled on centrifugal fans, i saw huge prices in the hundreds  
of dollars.

Would mean the centrifugal fans are more expensive than the entire  
cluster which seems a tad odd.

So it's gonna be the cheapskate cardboard solution with some duct  
tape and glue and relative cheap fans.

---

The fan in my dell is plastic and cheap.. I've seen them surplus for under $5..

But what you want is often sold as a "squirrel cage blower"..

The advantages are:
a) good performance against backpressure
b) lots of very small blades, so the "blade repetition rate" noise is high frequency, low amplitude and easily absorbed
c) they give decent performance at low rotation rates (500-1000 RPM)

they are the dominant device used in, for instance, heating and airconditioning.

A good cheap source is from automotive scrap yards.  The blower that pushes the air through the heater core and all the various ducts in a car is well suited to pushing a lot of air through a lot of loss.  12VDC typically.  Make sure you get the housing too, not just the squirrel cage and motor. This may require a bit of hacksawing on modern cars.

Ones from upscale cars are quieter than more downscale cars.  So find that Mercedes scrap, not the stuff from the DDR (Do Trabants even have heaters, or do you wear your good socialist overcoat)


Here's a typical item on eBay
http://www.ebay.com/itm/Squirrel-Cage-Shaded-Pole-Blower-Fan-220-CFM-Dayton-60-available-/190685633240?pt=LH_DefaultDomain_0&hash=item2c65bfdad8

Here's a 12VDC one
http://www.ebay.com/itm/454-CFM-12-VOLT-DC-SPAL-007-A42-32D-3-SPEED-CAB-FAN-BLOWER-16-1406-/270917027943?_trksid=p4340.m1982&_trkparms=aid%3D555000%26algo%3DPW.CURRENT%26ao%3D1%26asc%3D10%26meid%3D8950398135996031222%26pid%3D100009%26prg%3D1005%26rk%3D1


I've also seen somewhat larger versions of this as an appliance.. plastic housing, designed to be set on the floor to blow air for cooling or helping to dry  recently mopped floors or wet carpets.

Here's one from a computer
http://www.surpluscenter.com/item.asp?item=16-1151&catname=electric

I should point out that they make these in huge sizes (as in 1 million CFM) for applications like underground mine ventilation