[clug] Effect of operating temps on life of integrated circuits

Rodney Peters rodneyp at pcug.org.au
Mon Jan 25 20:35:26 MST 2010

On Saturday 23 January 2010 20:45:57 linux-request at lists.samba.org wrote:
> Message: 6
> Date: Sat, 23 Jan 2010 19:43:21 +1100
> From: Ben Nizette <bn at niasdigital.com>
> To: steve jenkin <sjenkin at canb.auug.org.au>
> Cc: CLUG List <linux at lists.samba.org>
> Subject: Re: [clug] Effect of operating temps on life of integratedclug] 
Effect of operating temps on life of integrated
>         circuits
> Message-ID: <B8C1493B-363F-4B41-82B1-A7F55DFB52E3 at niasdigital.com>
> Content-Type: text/plain; charset=us-ascii
> On 23/01/2010, at 6:32 PM, steve jenkin wrote:

> > Another cute factoid I ran into about Fans:
> >
> > Noise varies with *5th* power of fan speed.
> > Running fans at half-speed is much quieter :-)
> >
> > Not sure about the power-draw of fans w.r.t. speed.
> > I'd have thought cube of speed, but that article said "square law" :-(
> This is another non-trivial eqn I'd think, as energy imparted to air would
> vary with the square of speed, energy lost to acoustic effects varies with
> the 5th power (as you point out, non-trivial at higher speeds) but maybe
> more importantly the reverse-EMF generated by the motor spinning itself
> causes the fan's efficiency to vary widely and in a
> non-trivial-to-calculate-in-a-general way.
I understand that square law applies, for the reasons you suggest, to 
axial-flow fans.  Most fans in IT equipment are of that type.  Cube law is 
generally accepted as the factor for centrifugal fans, which are seen only 
occassionally in IT equipment.


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