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Re: [Amps] Fan for SB220

To: amps@contesting.com
Subject: Re: [Amps] Fan for SB220
From: Adrian <vk4tux@bigpond.com>
Date: Sun, 19 Dec 2010 08:31:02 +1000
List-post: <amps@contesting.com">mailto:amps@contesting.com>
There seems to be a lot of confusion regarding heat transfer here. Black 
is not the the best colour for radiating heat, it does not radiate 
anything and that's what makes it black *.

That also is why it is a good idea in the sb-220 tube cabinet to 
minimise reflected radiated heat back to the tubes. I have compared 
before and after temperatures on the mid tube outside envelope 
temperature and saw a 17 deg C drop after the inner cabinet was painted 
flat black on my sb-220

Due to this *,  black maintains a higher surface temperature making it 
more efficient with convection cooling (not radiated ) than other 
colours, heat transfer is dependent on the temperature difference 
between the two mediums involved with conduction and convection cooling.

A black plate between the tubes would be effective to reduce radiated 
heat transfer between the two tubes, as it will absorb the radiated heat 
raising the material surface temperature, and releasing this heat with 
convection cooling from the fan, but I would be concerned with the 
effect on stray capacitance with its close proximity , and I'd like to 
keep stuff like that well away from the B+ in anycase.

I say painting the tube surround black is a smart move, but forget about 
added divider plates.
May cause more problems than it helps.

Adrian ... vk4tux
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