[Amps] SS amps watercooling - was PowerGenius XL

[Kevin]

Propylene Glycol.

It's cheaper than Ethylene Glycol (Car anti-freeze), is non-toxic with 
rust and algae inhibitors. All anti-freeze lowers the freezing point of 
the water it is mixed with. It also raises the boiling point of the same 
mix. A 50/50 mix of "RV Anti-Freeze" may be what your looking for.


On 3/6/2017 8:04 AM, Manfred Mornhinweg wrote:
> Okay, folks, can we then perhaps reach some consensus, or 
> recommendation about what exact liquid to use in watercooled electronics?
>
> It has to be water-based, because there is simply no other liquid that 
> matches water in terms of specific heat, availability and cost.
>
> We don't want buildup of anything in out heat exchangers. So we must 
> make sure that the liquid is pretty much free from calcium, magnesium, 
> carbonate, silicate, sulfate and other such ions that tend to 
> precipitate on hot metal surfaces and form scales. This rules out tap 
> water (unless it's very soft).
>
> We don't want algae growing either. This pretty much requires some 
> sort of alguicide added to the liquid. Otherwise we WILL get them, in 
> the long run. What to use? Chlorine ions? Hypochlorite? Some alcohol?
>
> We don't want corrosion. But a tiny amount of corrosion should be no 
> problem. If we load the amplifier with distilled water, and that water 
> rips some copper from our tubing and heat exchangers, until reaching a 
> balance, is that so bad? I think we can live with it. If not, then we 
> would need some sort of corrosion inhibitor if we start from distilled 
> water.
>
> Conductivity may or may not be an issue. With a typical LDMOSFET amp, 
> that has the source (and cooling block) at ground potential, and every 
> other metal part of the cooling system at ground potential too, 
> conductivity is a non-issue, as long as there are no metals with very 
> different electrochemical potential there (because then one of them 
> would corrode the other, by electrochemical action). It should be easy 
> enough to make the whole system just from copper and plastic, so that 
> there would be only one metal, and no electrolytic corrosion. Then we 
> simply don't need to worry about conductivity.
>
> But if I ever build the amp I planned years ago, that uses cheap 
> switching MOSFETs, I would have two cooling blocks at drain potential. 
> It would be easy to keep the entire water circuit at the supply 
> voltage, so there would be no DC between any parts of the water 
> system, but there would be RF voltage between  the two cooling blocks. 
> Typical water solutions have a resistivity that's plenty high enough 
> to cause only negligible loss, but would the tiny RF current between 
> the two cooling blocks cause harmful electrochemical action? If yes, 
> then an insulating liquid would be needed.
>
> Cars typically use distilled water mixed with concentrated 
> "antifreeze", which is usually a mix of glycol (the antifreeze proper) 
> with corrosion inhibitors, and possibly alguicides, etc. We don't need 
> antifreeze action on our amps, used at room temperature. And in 
> countries like mine, where in most places the weather never gets below 
> freezing, car parts stores sell a refrigerant for cars that doesn't 
> contain antifreeze, but just corrosion inhibitors and a lubricant for 
> the water pump. Would perhaps this stuff, mixed with distilled water, 
> be a good candidate? In cars it's typically used at a concentration of 
> just 1 to 3%.
>
> A note on rainwater: Even in areas free from industrial pollution (if 
> such a place exists...), rainwater is still moderately acidic, because 
> the rain drops absorb carbon dioxide from the air, forming carbonic 
> acid (the same stuff that in much higher concentration makes soft 
> drinks fizzy). I live in a pretty clean, non-industrial forest area, 
> and some months ago I measured the acidity of freshly collected 
> rainwater. Its pH  turned out to be 5.8.
>
> And another note, on tap water: It doesn't seem to be terribly 
> corrosive, at least not to copper, brass and solder. Many houses here 
> have copper water pipes and brass fittings, soldered with either 
> tin-lead solder, or the more modern ones with pure tin, or with alloys 
> having mostly tin and a small amount of some other metal, and these 
> installations run reliably for many years, with hot and cold tap 
> water. Only in areas that have extremely hard water, scaling can 
> become a problem after several decades, mainly when scales shed off 
> and accumulate at the lowest spot of the piping, causing a clog there. 
> But corrosion doesn't seem to happen.
>
> Instead when zinc-plated steel hot water tanks are connected to copper 
> piping,  this forms a shorted galvanic battery! Given slightly acidic 
> tap water, it eats the zinc in a short time, and then starts eating 
> the steel below, and we get rusty hot water! Instead with slightly 
> alkaline tap water there is no big problem.
>
> Anyway I can't avoid the feeling that it would be better to develop 
> good high efficiency linear amps, so that cooling requirements become 
> very low, and nobody would have any need to consider watercooling.
>
> Manfred
>
> ========================
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> http://ludens.cl
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-- 
R. Kevin Stover
AC0H
ARRL
FISTS #11993
SKCC #215
NAQCC #3441


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