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Water cooling Power Tubes

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i am planing on building something with a water cooled power tube, and i was wundering how exactly should i buid the jaket to cool the tube, shuld i just emerse the anode in a water bath like a vapor cooled tube, or should i build a pipe coil on the anode (with some brass or bronze or copper inbetween) that runs the water threw it.

i am asking because i didnt finde a lot of infos on the subject of watercooling a power tube.

the disapation of the tube is a few KW´s
 
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Joined 2010
I have seen it done on thyratrons..

The problem with the system was the water became contaminated by metal from the tubes and bypassed the rubber insulators..leakage detecting circuits were used..I have very limited experience with this...I guess some on here have much more..

I guess you have seen this:
Vacuum Tube Liquid Cooling

The leakage I refer to is electrical conduction across the insulating boundary into the cooling equipment..


Regards
M. Gregg
 
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Well one would assume the tube and the water was at the same ambient temperature to start off with. Think of a fish tank heater.

You could google and see what guys are doing with brushless motors, the odd one makes their own jacket from brass. Not to many do though as standard size water jackets are available for under $10.

Go old school DIY and get a thin sheet of brass, some spigots and solder.

These look a little ghetto but you get the idea.

Homemade Water Jacket PiX - Blast - Traxxas
Custom Water Cooling Jacket - Rum Runner Racing
 
to answer th "v4lve lover", the tube is designd to be water cooled, its got a copper anode so water cooling, its not a litle amp tube. and i dont think that i will finde a water jacket for a tube like the GU-5A or the GU-10A or simuler power tubes. and making a jacket isnt the problem, its the "how it works" that im interested it. (how i need to cool the anodes)
 
Vapor phase is a genuine PITA. I'd stick with direct cooling of a tight fitting jacket with thermal compound between it and the tube. One way to construct such a jacket is to cast a mold with plaster paris and then use mold to either electroplate or manually form aluminum or copper sheet. To start electroplate vapor vacuum deposit aluminum on inside of mold. You may wish to do some clearancing in mold to deal with jacket thickness.

But... suspension in Dow Corning silicon oil would probably be simpler.
Doc
 
3.5kW of heat is a LOT! Same as electric Kettle!--ie, boil 3 pints of water in a few minutes.....

What on earth are you gonna make with That thing? Water-cooled radio Transmitter valve!

If you say, SE Audio-Amp, then IMHO, you are totally Nuts!

The amount of heat you'll need to remove, can easily be done by using the appropriate enclosure to allow the water seals to immerse anode in water, and a pump to circulate the water to a Car Radiator with a fan attached!

Anode then would need to be at Ground potential and the Cathode, Heater, Grid Drive etc referenced at Minus 4kV...

NOT an easy project....
 
In many cases it is desirable to operate the tube's anode at ground potential. This keeps the water system at ground and eliminates high voltage problems. Of course, the other tube elements must be operated at a progressively higher negative potential to function. This is the way all water cooled induction and dielectric heaters that I have seen do it.

From the Eimac "Care And Feeding Of Power Grid Tubes".

Water-cooled tubes depend upon an adequate flow of water to carry away heat fast enough to maintain the cooled parts at a safe operating temperature. The recommended flow as specified by the technical data sheet should be maintained at all times when the tube is in operation. Inadequate flow of water at high temperature may cause formation of steam bubbles at the anode surface where the water is in direct contact with it. This can contribute to premature tube failure or burnout.

Be electrolysis and scale formation, hard water may cause a gradual constriction of some parts of the water system. Therefore, water flow and plumbing fittings must be inspected regularly. The fittings on the positive potential end of an insulating section of hose or ceramic water coil or column are particularly subject to corrosion or electrolysis unless they have protective "targets". Targets should be checked periodically and replaced when they have disintegrated.

Cooling water temperature is important. The tube technical data sheet should be consulted to be sure operartion is within safe limits.

Purity of cooling water is important. The specific resistivity must be maintained at 1 megohm-cm minimum at 25ºC. Distilled or deionized water should be used and the purity and flow protection should be periodically checked to insure against excessive degradation. Oxygen and carbon dioxide in the coolant will form copper oxide reducing cooling efficiency and electrolysis may destroy the cooling passages. In addition, a filter screen should be installed in the tube inlet line to trap any circulating debris which might clog coolant passages within the tube.

If the air is humid and the cooling water is cold, condensation accumulates on the surfaces of all pipes, tube jackets and other parts carrying water. This condensation may decrease surface leakage resistance, of drops of water may fall on some electrial componets and cause erratic operation or failure. Some means is then necessary to control the temperature of the incoming water to keep it above the dew point. Control is rather easy in a closed cooling system, but in a system which employs tap water and drains the exhaust water into a sewer, control is difficult.

Connecting lines should be of an insulating material such as polypropylene, but chlorinated polyvinyl chloride (CPVC) is also acceptable and is stronger.

Circulating water can remove up to 1000 watts per square centimeter of effective internal anode area. In pratice, the temperature of water leaving the tube is limited to 70ºC to preclude the possibility of spot boiling. This water is then passed through a heat exchanger where it is cooled to 30ºC-40ºC before being pumped over the tube again.
 
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i was intending on using Distilled water to cool the tube in a closed system, as a heet exchanger i was also intending on using a car radiator. and the destilled water should limit the leakeg current to within a few mA (or less), else i will reconfigur the system to run the cathode at highvoltage insted of the anode (this will be somewhat tricky to do).

and did i understand you corectly that you want me to directly emerse the copper anode in a water bath, cuz i was thinking about a copper (or aloiy of sorts) cilender with copper tubing raped around it (maby in a gruve, the cilender stands on insulaters rated for 20KV.
 
Distilled water and pure ethelyne glycol was generally used on the liquid cooled TV transmitters I've worked on. The glycol could be omitted where chillers are run inside or where climate never reaches freezing. I was told that the glycol mix actually worked better for cooling, but I couldn't verify it.
Doc
 
... i was thinking about a copper (or aloiy of sorts) cilender with copper tubing raped around it...
Wrapping a coil of tubing around the anode to carry the water would greatly reduce the efficiency compaired to water directly on it, I would think.

I was told that the glycol mix actually worked better for cooling, but I couldn't verify it.
Sure you can. Your automobile uses that all year round. At least it should.
 
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There are Ethylene Glycol specs for this type of application, we use it for our cooling water in our Electromagnetic Stirrers. The water is also critical. We filter and continuously maintain it in soft and Deionized state. If we fail to maintain it at that level we tend to estroy 1 million$ stir coils quite quickly. Luckily we have sofisticated ground fault detectors which shut it down before it becomes a threat to personel.
 
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Joined 2010
Just for interest,

The system I worked on had an interlock that shut down the tube if the cooling system failed and would not start unless the pump was running.. :)

Any electrical leakage detected also shut it down. also flow detection was used..


Regards
M. Gregg
 
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