[Amps] liquid cooling

[donroden at hiwaay.net]

I've run vapor phase and water cooled klystrons for fourty years, and  
unless there is some compelling reason to vapor phase, I prefer  
keeping the coolant under 140 degrees f.   ( That would be under 100  
degrees in a ham amp )

Don WA4NPL



Quoting "Paul Christensen" <w9ac at arrl.net>:

>> Vapor-phase cooling is even more efficient: you
> actually get the water up to boiling, and _LOTS_ of energy is carried off
> in those steam bubbles. "
>
> With vapor-phase cooling, a rise in H2O temperature near the boiling point
> is fine, but heat transfer efficiency begins to greatly suffer at the point
> of hot-spot boiling.  Steam bubbles create an insulation property and
> diminish the heat transfer efficiency.  As the heat transfer efficiency
> creases, H2O temperature rises, creating even more bubbles until thermal
> runaway results.
>
> Typical heat absorption with vapor-phase cooling is roughly 600
> calories/gram of H2O while vaporizing.  By contrast, in a closed-loop H2O
> system, approximately 35 calories of heat can be absorbed per gram of H2O.
> Using these numbers, vapor-phase cooling requires a flow of only ~ 6% of the
> same H2O volume as does a closed H2O system.
>
> It would be interesting to compare the efficiency of a closed-loop ATF oil
> solution to these two H2O methods.   As to maintenance of a typical
> vapor-phase cooling architecture in amateur service, it's very minimal.  I
> purge my distilled H2O at 12 month intervals and during the year, I never
> see leakage rise to more than about 2 mA of current at 4KV.  Nor have I
> experienced any algae build-up in the Florida heat & humidity.
>
> Last year, I rebuilt the entire plumbing system of an Alpha Seventy
> amplifier.  It was the first re-build done to the amp in 40 years.  Total
> cost for all the original OEM parts was less than $10 + an additional $40
> for a custom bellows section and about 12-inches of Polypropylene line.  The
> condenser is about the size of a motorcycle radiator and uses soft-soldered
> joints.  It would probably take a very long time before it fails and repair
> should be easy.
>
> Paul, W9AC
>
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