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Re: [Amps] Meaning of "conduction cooled"

To: amps@contesting.com
Subject: Re: [Amps] Meaning of "conduction cooled"
From: Ian White G/GM3SEK <gm3sek@ifwtech.co.uk>
Reply-to: Ian White GM3SEK <g3sek@ifwtech.co.uk>
Date: Thu, 3 Nov 2005 19:25:54 +0000
List-post: <mailto:amps@contesting.com>
Steve Thompson wrote:
>
>
>Vic K2VCO wrote:
>> Floyd Sense wrote:
>>
>>>Most amps today use convection cooling.  To me, radiation cooling would
>>>imply no airflow used and that isn't seen very often.
>>
>>
>> I would say that external anode tubes like the 3Cx800, etc. are
>> convection (or more precisely, forced-air) cooled,
 >
>But doesn't convection (and forced air) start with conduction between
>the hot surface and the air - so they're all conduction cooled?
>
Not in the normal usage of those terms... but it also depends on whom 
you ask.

A fluid dynamicist would describe any kind of heat transfer by a moving 
fluid as "convection". An engineer would divide this into "free 
convection" (driven only by buoyancy) and "forced convection".

However, both would say that "conduction" can only occur in a solid, and 
thus it ends at the surface boundary.

>I'd say a 'conduction cooled' tube displaces the heat through a solid
>link to a cooled surface

Certainly, that is always what "conduction cooled tube" means.

The three classical heat transfer mechanisms are conduction, convection, 
and radiation. If you look hard at any particular amplifier, and think 
in detail about the way the heat is transferred away from the hot bits 
(anode/collector/drain) and eventually dumped out into the surrounding 
environment, you will always find that all three mechanisms are 
involved.



-- 
73 from Ian G/GM3SEK
http://www.ifwtech.co.uk/g3sek
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