Date: Thu, 16 Feb 2017 10:19:44 +1300
From: Steve Wright <stevewrightnz@gmail.com>
To: amps@contesting.com
Subject: Re: [Amps] SS amps watercooling
On 16/02/17 06:00, Big Don <bigdon39@gmail.com> wrote:
> Water-cooled amps HEALTH TIP --
> There are enough ways to *electrocute* yourself playing with amps
> without having leaked water spraying everywhere....
> Don N7EF
Watch out driving your diesel car as well - you DO realize that the fuel
pressure in those is around 40,000 psi?
That's obviously highly dangerous and drivers should be degreed
engineers at least, and it goes without saying that women and children
should definitely not be within a few hundred feet of a dangerous
scenario like that!
Or just maybe, non-retard hams can securely fit a hose on a 4psi system
around 50 volts DC.
S
## I would not be worried about water near 50 vdc. Perhaps a minor
concern with water near 240 vac. IF the switching type 50 vdc supply was
separate from the RF deck, it would be a non issue.
## However there are other possible concerns. Say the RF deck ran at 50%
eff.
Say you wanted 1.5 kw out RTTY ..and also FM. That requires 3 kw dc input..
and 1.5 kw CCS of dissipation. 1 watt = 3.412142 BTUs.
1500w = 5118 BTUs. Thats a heck of a lot of BTUs to dump...and CCS.
## water out of your back yard tap is aprx 4 gpm..and thats with aprx 40 psi
from
the street..and also no other devices sucking water, like toilets, dishwasher
etc.
## These small water cooled dummy loads, that use tap water, dump the heated
water into the drain. In the case of the SS water cooled proposal, the heated
water
has to flow to an external, air cooled radiator. Its one big loop. No way can
the water
get anywhere near boiling, anywhere in the loop. Dunno if you could add
redline
water wetter to the mix or not. Water wetter stops the bubbles forming when
close to boiling. Is distilled water even required for a water cooled SS
amp ??
If not, an ideal mix would be distilled water + water wetter. Then you have
pure
water, with no chance of forming bubbles..... but thats only provided you
don’t get
any where near boiling.
## You would also have to have the correct gpm flow rate, and also a rad big
enough
to dump the heat fast enough..and also a big enough fan. Most fans are not
fast as far
as mph air velocity is concerned. They may be high cfm, but the velocity of
the air is not
high at all. Typ 1800 cfm fans used for cooling Heat exchangers used on super
charger
setups for cars only have an actual air velocity of aprx 16-17 mph. Used
on drag cars
so they have some air flowing through the HE, when sitting at 0 mph in the
staging lines.
## check out rads used for eng oil cooling for race cars. They will rate then
for XXX BTUs,
but read the fine print, thats at 80 mph minimum. Any air cooled rad setup
for a SS amp would
also require shrouding the fan to rad..or u lose it right there.
## Ideally what you want is for the flow rate to be FAST through the heat
sink and RF deck, to extract heat, but SLOW
through the rad...to dump heat. But its all one big loop, so you are
screwed. Only fix is a big rad, and lotsa air on the rad.
Other wise you will just be circulating hot water. Think of how long it takes
to boil just 2 litres of water in a standard
1500 W CCS kettle in your kitchen...2-3 mins max. And you cant use vapour
phase cooling with SS devices, too hot at 100 deg C.
## Im sure water cooling can indeed be done with SS, but it would all have to
be sized very carefully.
Jim VE7RF
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