[Amps] Muffin Fans and hot exhaust/2

Dr. David Kirkby davek@medphys.ucl.ac.uk
Tue, 23 Jul 2002 14:28:51 +0100

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.

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

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