[Amps] Muffin Fans and hot exhaust/2

[2]

>Tom Rauch wrote:
>
>> In fact most noise is caused by bearings in the fan, turbulence in
>> the impeller, and at times from turbulence in the device the air is
>> forced through. Some fans and blowers have poor balance, but that
>> mostly causes a low rumble.
>
>One manufacturer of hard drives (Fujitsu if memory servers me correct) has
>produced what has been billed as a silent drive. Clearly motors can be made
>very quite.
>
>I'm not aware of how to reduce wind noise - that is I'm sure a specialist
>subject I know zero about.
>
>Vapour cooling is a method used for large tubes and has been also been used
>by some ham amps. I once had a 4CV20000, which was a vapour cooled 20 kW
>device from Eimac. I abandoned any ideas of using it, since I did not know
>its condition and had no hope of getting another. However, Eimac did (do?)
>make an 800 W (if memory severs me right) vapour cooled tube and I believe
>a ham amp used it. Vapour cooling is almost silent.
>
One rub with vapour-cooling is that the cooling water is normally vented 
to the atmosphere.  Since humans exhale carbon-dioxide, carbonic acid 
forms in the water -- which makes it conductive - plus carbonic acid 
attacks metal.

>I used to use a rather inefficient laser system (50 kW input, for 1W out -
>and that was on a good day). The coolers on that made rather a lot of
>noise.
>
>--
>Dr. David Kirkby,
>Senior Research Fellow,
>Department of Medical Physics,
>University College London,
>11-20 Capper St, London, WC1E 6JA.
>Tel: 020 7767 6409 Fax: 020 7769 6269
>e-mail davek@medphys.ucl.ac.uk
>
>
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>


-  R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K, 
www.vcnet.com/measures.  
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