[Amps] SS amps watercooling

[Jim Thomson]

Date: Thu, 16 Feb 2017 10:19:44 +1300
From: Steve Wright <stevewrightnz at gmail.com>
To: amps at contesting.com
Subject: Re: [Amps] SS amps watercooling

On 16/02/17 06:00, Big Don <bigdon39 at 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