[Amps] Meaning of "conduction cooled"

[David Kirkby]

Will Matney wrote:
> Bill,
> 
> One thing about conduction cooled tubes to me is that there is a hot spot at 180 degrees from where it mounts to the heatsink. A convection cooled tube with heat fins has cool air passing over these fins 360 degrees around the circumferance. I'm not sure if any tests have been done, but this may lead to the conduction tube failing before the convection one, I don't know.
> 
> Best,
> 
> Will

I had a few email exchanges with Reid at Eimac about CC tubes. 
Apparently they do run a lot warmer (typically) and so their life is 
shorter than air-cooled tubes. The manufacturing cost is higher - much 
of that due to the waste disposal problem of the BeO that is used is 
carcegogenic. So all this adds to their cost and relative unpopularity.

Here is a data sheet on pretty big CC tube with an anode dissipation of 
1 kW. I'm not aware of any bigger ones.

http://www.g8wrb.org/data/Eimac/Y-477.pdf

It's a special version of the 4CX1500B.

There are other conduction cooled tube data sheets at

http://www.g8wrb.org/tetrodes.shtml (tetrodes)

and

http://www.g8wrb.org/triodes.shtml (triodes).






> 
> *********** REPLY SEPARATOR  ***********
> 
> On 11/3/05 at 1:26 PM Bill Fuqua wrote:
> 
> 
>>If a tube is convection, conduction, radiation, liquid or vapor phase 
>>cooled has to do with how heat ,produced by the kinetic energy from 
>>colliding electrons, is removed from the anode.  From there it may pass 
> 
>>from one place to another until ultimately dissipated into the environment 
> 
>>by all sort of heat transfer mechanisms.  There are some very minor points 
>>about this that can be argued, such as,  in the case of the convection 
>>cooled tubes or even the radiation cooled tubes where there is thermal 
>>conduction from the side of the anode where the electrons collide to the 
>>surface where it is dissipated. But that is a very minor point  except to 
>>the nitpicking purest.
>>
>>73
>>Bill wa4lav
>>  
>>
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> 
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-- 
David Kirkby,
G8WRB

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