[Amps] H2O cooled tubes

["John T. M. Lyles" <jtml@lanl.gov>]

To build a heat exchanger you can make some quick calculations to see 
what sort of heating you are dealing with.

You will be dumping the plate dissipation, some filament power and 
some drive power (probably low) into heating water, and assume the 
worst case like it is mistuned at low efficiency. Then the 
temperature rise and flow are related by :

0.2648 x delta T x flow = Power in kW
Using a mix of units, pardon me Europeans, where Delta T is in 
degrees C and Flow is in Gallons Per minute.

You can then determine what sort of flow to expect through your 
transmission cooler or heater core, by hooking up your hose or pump, 
and pouring the outlet into a gallon bucket. With this sort of flow 
(assume some losses in the elbows and tubing), you will heat the 
water a given rise in temp over the outlet water.

This all assumes that you have the heat removal capacity in your 
exchanger, a big fan outside, or a larger thermal mass at the other 
side of it. If the outlet temp rises over time, even with the fan 
running, then realize that your tube will run hotter too.

Never boil water in the anode of a water cooled tube, unless it is 
specially designed for that, such as a vapor phase, multiphase, 
hypervapotron or whatever the manufacturer calls it.

As for HV rating on the hoses, try to keep DC leakage current under 
one mA, or you may slowly eat away your pipe fittings where the HV 
bridges them across the water. Use Deionized water and take a reading 
on conductivity if you have a meter. You can calculate the hose 
diameter, and assume it is a resistor of that diameter with the 
conductivity per cm. You can determine how long the gap in the hoses 
needs to be for a given current. Smaller hoses give higher R, which 
is an advantage. Then the flow is lower of course. Then the Delta T 
is higher. All is a trade off.

Try to use Teflon, polypropylene, silicone, or other low carbon 
hoses.  PVC water pipe will work too, but keep it out of RF E fields.

73
John
K5PRO
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