On 6/6/2013 12:13 AM, Bill Turner wrote:
ORIGINAL MESSAGE: (may be snipped)
On Wed, 05 Jun 2013 20:09:34 -0400, K8RI wrote:
Water cooling is nice, but you are probably going to need either DI or
distilled water at those voltages and water cooling can be a royal PITA
when things go wrong.
REPLY:
I realize the pitfalls, but with DI or distilled water, I was thinking of
completely submerging the transistors and heatsink. Sounds a bit loony but
it might work. The drawback of course is you don't have an unlimited supply
like if you were using an outside hose connection and cooling only the
heatsink. .
It's been done with transistors and tubes, although I think the tubes
were in the 300 to 500 volt range and iy was just to see if it could be
done. This is a bit different from where only the tube envelope was
submerged. It was a long time ago, but I'll bet there are some on here
who remember the particulars.
With transistors (particularly computers) the entire circuit has been
submerged in coolants of at least several types and I have heard of
several QRO approaches using submersion.
Although at room temp water is the most efficient coolant it might
present problems with solder. There must be alloys that are less
susceptible to the corrosive effects of DI water and I would think
complete submersion would work and these circuits would be less prone to
changes in capacitance due to the presence of the water. I was lucky to
survive Chem 111 and 112 although I did get good grades.
Silicone 200 fluid of a low viscosity should be effective as well,
although less effective at heat removal than water it is still quite
effective.
Whether just the immersion of the transistor case or the entire circuit
both sound feasible to me.
I like the idea of complete submersion as it removes the problem of
level control. with submersion position, or movement is no longer a
problem. 1 gram or CC of water increases 1 degree in temperature for
each calorie of heat removed so it takes relatively little flow to
handle 1 KW of heat which is the dissipation of an amp putting out the
legal limit at 60% efficiency.
If refrigerated it can greatly increase the transistor's power handling
capacity. With computers they just submerge the entire CPU, or CPUs
directly in the refrigerant.
Good Luck!
es 73
Roger (K8RI)
One way to find out.
73, Bill W6WRT
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