[Amps] Oil v water cooling

Sat Apr 18 05:28:33 EDT 2015

It's been a long time, but as John said, these solutions are ion hungry 
and particularly DI water.  We measured resistivity at ohms per cubic 
centimeter,.  It's not just solder, they will reduce a brass hose 
fitting to a dull copper color that you can crumble with your fingers.  
It also likes copper, to the resistivity monitoring mentioned several 
times is a necessity. We went through thousands of gallons of DI water.
Oil can most likely be used on almost any water cooled tube, but water 
is likely, by far, the best for carrying heat away.  I can't imagine 
using oil

73

Roger  (K8RI)

On 4/16/2015 12:13 PM, David Lisney wrote:
> Hi, I believe that not all "distilled water" is suitable for this, you may need to specify "deionised water". The water conductivity needs regular checking, it will rise as it gets contaminated by traces of solder flux etc...I seem to remember where in a published design for a watercooled amplifier that about 6" from the tube anode that the plastic cooling pipe went through a brass coupler that had a meter connected between it and chassis ground to monitor leakage current.
> Regards David G0FVT
>
> Sent from my iPad
>
>> On 16 Apr 2015, at 17:01, amps-request at contesting.com wrote:
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>> Today's Topics:
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>>    1. oil vs distilled water cooling. (John Lyles)
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>> ----------------------------------------------------------------------
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>> Message: 1
>> Date: Wed, 15 Apr 2015 21:57:07 -0600
>> From: John Lyles <jtml at losalamos.com>
>> To: amps at contesting.com
>> Subject: [Amps] oil vs distilled water cooling.
>> Message-ID: <552F3313.2080307 at losalamos.com>
>> Content-Type: text/plain; charset=windows-1252; format=flowed
>>
>>> ##  so exactly what is the issue with oil vs distilled water ???   Distilled water
>>> can be found in 4 litre jugs, cheap, at any grocery store.  To the best of my knowledge,
>>> distilled water will extract heat a lot faster / better than oil.   I only saw 1-2 small tubes in the
>>> entire Eimac catalog that used oil cooling.  All their big commercial broadcast tubes are either
>>> air, or water, or vapor phase cooled tubes.  Or multi-phase cooled.... which is a combo of
>>> water cooled and vapour phase cooling.
>> All of the amplifiers I design and use at work are water cooled, some
>> flowing water and some multiphase, or hypervapotron mode, which is the
>> same thing but a trademark. Its not a tough problem to crack, and I'm
>> dealing with considerable HV. I studied the RCA, Eimac and Thomson
>> recommendations some years ago, and use a common set of specifications.
>> Keep the DC leakage current in the hoses < 500 uA per hose. So for
>> whatever resistivity is maintained, the hose diameter and length is
>> designed for this current (resistance) at the maximum plate voltage to
>> be used. DI water is closed loop cooled, as its New Mexico and we cannot
>> waste water. This complicates things with heat exchangers and secondary
>> loops with cooling towers. Since the water is recycled, we have to watch
>> the ph and the dissolved oxygen level as well. For < 5 kV DC I think the
>> requirements are much less difficult to meet.
>>
>> Now, adding an ionic additive like water wetter is risky for a pure DI
>> or distilled water system. One reply said the typical content is:
>>> DiIsoPropyl Alcohol Ether 1-4.9%
>>> TriIsopropyl Alcohol Diether 1-4.9%
>>> Sodium Molybdate 1-4.9%
>>> Tolyltriazole 1-3%
>>> PolySiloxane Polymer
>> That third one is a good corrosion inhibitor. I use the same molybdate
>> as an ionic additive, that when put in solution with pure water, makes
>> an excellent dummy load. The amount is about 0.5% by weight, and I use
>> what are called water column loads. These are essentially
>> multiwavelength long coaxial cylinders with a shorted center conductor
>> at the far end. They contain a way for this solution to flow through,
>> and if I use pure water the mismatch is terrible, like 1 dB RL. When I
>> add the 0.5%, the match becomes 20 dB RL at a specific frequency. So a
>> tiny bit of molybdate makes a huge change in RF loss. I have also
>> noticed that it makes a large difference in the DC conductivity of the
>> solution. My best soup is 530 microsiemens/cm^2. With just a few hundred
>> cc dumped into a system with several hundred gallons flowing will change
>> this value by a factor or 2 or more.
>>
>> I would be wary of doping the distilled water with these chemicals
>> without doing an experiment first.
>>
>>
>>> ##  last year, I tested distilled water  vs  tap water  with just a fluke 87 dvm.  The
>>> dc resistance of distilled water is sky high compared to tap water. Distilled water is
>>> a superb insulator.   Dunno what happens to the dc resistance once  water wetter is
>>> added to the distilled water.  I should re-run the test.   For a tube cooling application
>>> it?s a moot point, since it?s a closed loop anyway.
>>
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