One purpose of the chimney is to move the air upward and then rotate the
direction of flow to near horizontal as done by the upper curve of the
chimney thus directing the airflow toward the anode connection. While
we understand that air directed at one side of a cylinder does flow
symeticrally around the cylinder. To this end it does concern me that
the air exiting from a chimney is directed at the anode connector and
heat sink which typically have horizontal fins. Personally not having
measured the turbulance, I'd have to agree with others that folks at
EIMAC made quite a study of the socket, tube chimney and anode
connector. Perhaps there's not as much cooling required for the anode
cooler as we think and thus the turbulance generated is a mute point.
FYI: My VHF legal limit amp uses a blower with a 6" dia wheel that is
only 2" wide turning at 3600 RPM. Yea, it's a bit noisy partly because
it has ball bearings (sleeve bearings would be less noisy) but the tube
is still as good as the day it was installed and there is no drift in
tuning from cold start to several hours of EME CW work. And oh yes, I
blow it from the bottom up.
73
Bob K4TAX
measures wrote:
>
> >
> >Just an observation, the design of a chimney is such that the vertical
> >flow of air is directed evenly around the tube envelope and as it exits,
> >also against the anode seal & heat sink at the top. I really don't
> >think a Coleman lantern globe or a pickle jar does the job.
> >
> ? Bob: Any opinion about the use of vertical air flow on horizontal
> cooling fins.?
>
> >Bottom cooling is also required on many tubes due to the heat produced
> >by the heater/filament. Socket contacts last a lot longer when they are
> >kept cool. I've seen solder melted out of the tube pins due to
> >inadequate cooling.
> >
> >As to blowers, a centrifugal blower is the only way to go. Muffin fans
> >just won't produce the required air flow with typical back pressures
> >presented by air system sockets. My experience says big diameter wheels
> >that are 2" wide are better than small wheels that are 4" to 6" wide.
>
> ? amen . This is how Kooltronics builds their line of high-pressure
> blowers.
> ?
> >Even though the two fans may spec that same CFM, this has to do with
> >radial velocity.
> >
> cheers, Bob
>
> >Jon Ogden wrote:
> >>
> >> on 5/13/01 9:52 AM, measures at 2@vc.net wrote:
> >>
> >> > ? You don't seem to get it, Jon. A high-speed centrifugal blower is
> >> > required to overcome the back-pressure in the SK-510 air system socket.
> >>
> >> Perhaps I don't, Rich.
> >>
> >> And perhaps I am full of BS. But I prefer cooling systems that work in the
> >> direction of natural convection of heat. Heat flows up. So something that
> >> blows cool air over something in an upward direction is in my mind better
> >> than something that blows air across it.
> >>
> >> Your comments about the blower and the reduction of air flow are quite
> >> correct, I am sure. Yet, the guys at Eimac that designed the cooling
> >> system
> >> and chimneys and tubes way back when weren't a bunch of boobs either. I am
> >> sure they had good reason to do it that way.
> >>
> >> Jon
> >>
>
> - Rich..., 805.386.3734, www.vcnet.com/measures.
> end
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