Date: Wed, 24 Nov 2010 21:52:30 -0800
From: "Bill, W6WRT" <dezrat1242@yahoo.com>
Subject: Re: [Amps] Tube Cooling..
ORIGINAL MESSAGE:
On Tue, 23 Nov 2010 20:28:52 +0000 (GMT), DAVE WHITE
<mausoptik@btinternet.com> wrote:
> Whilst it may seem counter-intuitive to blow cooling air DOWNwards I've seen
> tome successful Eastern European designs whereby large fans blow air directly
> downward onto the top of the tubes so that the air runs by the fins.
REPLY:
The trouble with that approach is you have hot air blowing down over the
tube seals and socket. Not good. Anodes by themselves are relatively
unaffected to heat compared to the seals and socket.
Better to have the cool incoming air flow over the socket and seals
first and then go to the anode.
73, Bill W6WRT
## partially agreed. On any Eimac spec sheet, they will always depict both
top down cooling, and bottom up cooling.
With top down cooling, way more CFM is required. Also, a separate air hose
must be used to cool the coaxial fil stem
on some tubes like 3x3 and 3x6, etc. It's those fil seals that will get you
every time with top down cooling. The normal
deal with the 3x3 and 3x6, when using top down cooling is.... 5-10 cfm must be
directed at the coaxial fil. Top down
cooling will work, but wouldn't be my 1st choice.
## You also have to be careful when using muffin fans, and using em to suck
hot air out ! Papst used to make
many of their 3/4/6" diam fans in two versions, sleeve bearings and ball
bearings. [ they all appear to be ball bearing
only these days]. The ball bearing versions would handle a lot more heat
than the sleeve bearing version.
85 deg C VS 55 deg C. 55 deg C is not that much .......= 131 deg F.
[85 deg C = 185 deg F]
## depending on how hot the exhaust air gets, you could shorten the life of a
sleeve bearing fan very quickly.
later... Jim VE7RF
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