[R-390] Tube Cooling

[kirklandb at sympatico.ca]

Seems to me Tisha did some of these experiments awhile back.

> From: quartz55 at hughes.net
> To: R-390 at mailman.qth.net
> Date: Thu, 18 Apr 2013 18:05:54 -0400
> Subject: [R-390] Tube Cooling
> 
> I remember painting some tube shields on some old piece of equipment years ago and it seemed to run cooler.  But..what I'm going to do since I have some of the IERC shields is take one and put my Fluke thermocouple in it against the tube to measure the temperature. Then tape the thermocouple right on the tube without a shield, and then also paint a standard crappy tube shield and measure the same thing, same tube same RX and see what the results are. I might even cut the top out of a crappy standard shield and see what that does.
> 
> I would posit that if you cut the top out of a standard tube shield, painted it mat black inside and out, so it was not containing the heat and let it convect better, it may do some good.  The thing is the IERC shields do contact the glass better, but there is minimal contact to the shield, so there is not much thermal transfer to the outer shield, thus not much radiation. I would think the best thing is to have mat black inside the shield, open top, and mat black outside the shield, I'm not sure the cad plating will make any difference to the mat black paint color, it's mostly about radiation, not convection. Best convection would in my opinion be best with no shield.  If you cut the top out of a IERC shield, it would probably work better too.
> 
> Painting the tube black may work too, hmm, maybe wrap it in a mat black tape?
> 
> Give me some time, I'm in the middle of spring here and there's too much to do.
> 
> Dave
> N3DT
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