There are waterless coolants used in automotive applications. Evans
seems to be the main manufacturer in NA. The main advantage is that
its boiling point is way higher than water + antifreeze. This means
that the operating pressure is near atmospheric and allows operation
at temperatures that would cause overpressure issues with water based
coolants.
Whether it is useful for this application is unknown to me.
Al
AB2ZY
________________________________________
From: Amps <amps-bounces@contesting.com> on behalf of Jeff DePolo
<jd0@broadsci.com>
Sent: Monday, March 6, 2017 1:32 PM
To: amps@contesting.com
Subject: Re: [Amps] SS amps watercooling - was PowerGenius XL
## IF conductivity is NOT an issue, then Id suggest using
what is already
being used in car eng radiator setups. Distilled water + a
corrosion inhibitor.
Typ a 50-50 mix of glycol + distilled water is used. The
glycol offers the
inhibitor properties, and also raises the boiling point by a
bunch, to typ 265 deg F,
IF under typ pressure of 10-15 psi. Less, with lower
pressure, but still more than
212 deg F. That 50-50 mix will also lower the freezing
point to aprx -40 deg F.
You can also buy the 50-50 premixed, just pour it in.
I agree.
In liquid-cooled broadcast transmitters (both tube and solid-state), the
thermal transfer fluid is typically a 50/50 mix of distilled water and
Dowtherm SR-1. SR-1 is ethylene glycol with corrosion inhibitors.
There
are a few manufacturers that recommend or specify something else;
Rohde and
Schwarz comes to mind - they spec DEX-COOL for some of their rigs (and,
yeah, I know all of the GM DEX-COOL horror stories, though I've never
experienced any problems myself either in broadcast transmitters nor
in my
own GM vehicles).
50/50 is a good all-around mix ratio for SR-1. It provides freeze
protection down to around -35 degrees F, yields a healthy
concentration of
corrosion inhibitors, and prevents bacterial growth/contamination.
Unless there is some anomaly that occurs during the life of the
coolant that
results in contamination, the primary reason to replace coolant at
regular
intervals is due to the natural change in pH. When the system is
initially
filled, the pH of the 50/50 glycol mix is about 9.3. As the glycol
ages,
and as the copper and aluminum in the plumbing and system components
leach
into the coolant, the pH slowly falls. We usually do a flush when
the pH
falls below 8.0, and we never ever let it go below 7.5. You don't
want to
let it turn acidic. While you can try to extend the lifespan of the
coolant
by adding KOH to raise the pH, by the time the pH starts gets down
near 8.0,
the corrosion inhibitors are likely nearing depletion anyway.
You can send a fluid sample out to a lab for testing of all the main
indicators of the health of the coolant (glycol concentration, pH,
inhibitor
concentration, contaminants, etc.) -- probably overkill for ham
amplifiers.
Dow will even do it for free if your system is large enough (as I
recall, if
the volume of coolant in the system is over 200 gallons they do it for
nothing). But, for home/ham use, I think that if you just do a
visual on
the coolant to confirm it's the proper color and free of
contaminants, and
you check the pH every few months and when it falls below 8.0 do a
flush and
re-fill, you would be fine.
By the way, cleaning the system real well before the first fill is very
important. A solution of a few percent TSP in distilled water is
typically
used, and then flushed twice with distilled water before filling the
system
with the 50/50 mix.
The usual disclaimers apply regarding the toxicity of ethylene
glycol, the
proper disposal of the same, yada yada yada.
--- Jeff WN3A
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