----- Original Message ----- From: "mike bryce"
<proso...@sssnet.com>
To: "Richard Knoppow" <1oldle...@ix.netcom.com>
Cc: <captc...@flash.net>; <Drakelist@zerobeat.net>
Sent: Thursday, December 16, 2010 9:32 AM
Subject: Re: [Drakelist] AC4 heat Fan Summary
thought I'd toss my .02 in with a question
on the tr series, a fan mounted to the rear of the pa
compartment,
should it blow in
or suck out?
since we're not trying to pressurize a compartment,
there's
plenty of holes in the cage and top cover, and since heat
rises,
it would seem to me that one would mount the fan so it
would
blow into and onto the final tubes
To me, it seems a fan sucking air out of the pa
compartment
would have to compete with the natural convention of heat
raising
so, what's the word from the thermal gods?
Mike, WB8VGE
SunLight Energy Systems
The Heathkit Shop
http://www.theheathkitshop.com/
I noted this in my little diatribe. For the T4 the
fan
works best sucking the heat out from the top. Its very
simple and works. Most of the heat in this TX comes from
the
finals and is concentrated in the final compartment.
While
it is in a perforated metal enclosure there is a lot of
heat
generated in a small area plus the addition of the
external
cabinet further interferes with both direct radiation of
heat and convection. A small fan very significantly
reduces
the heat.
Much of what I wrote has to do with completely
enclosed
spaces where the conditions are quite different from the
above. Where you can control the air flow there are
advantages to positive pressure but, again, one must be
careful to plot out the flow of _heat_ to insure one is
not
getting unintended heating rather than cooling.
Actually,
that's the problem with using a pushing fan on something
like the T4, the heat is pushed out around other
components
and can heat them up where the sucking fan draws cool air
from around the tubes and exhausts it directly to the
air.
I mainly wanted to point out the differences between
cooling a basically open area like the T4 final cage and
a
completely enclosed space like the AC-4.
--
Richard Knoppow
Los Angeles
WB6KBL
dickb...@ix.netcom.com
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