Look up Thermacore in Lancaster PA, they are
making some innovative heat pipe cooling loops
for integrated circuits and other applications.
As for adding sodium or other ions to DI water:
this will increase the conductivity greatly and
cause current flow in the hoses. Eventually leads
to migration of the copper and brass fittings, as
deposits along the inner walls of the hoses.
Also, this will erode away the fitting where the
hoses connect to the tube from the mA flowing. In
our water cooler RF amplifiers, I try and keep
current under 250 uA in the hoses if possible.
When we have large OD hoses like 2 inches or more
(for big toobes) this is a problem, and it
requires length to get enough resistance between
the tube and ground, in each hose. In a hose such
as 1 inch PEX (which is sold at Home Despot and
'Lows' for home plumbing) about 60 inches are
required with 5 Megohm-cm water conductivity
(very clean). We trip HV interlocks on many of
our systems if the Foxboro conductivity meter
indicates below 5 Megohm-Cm. This indicates time
to change the Culligan bottles. Call Culligan
man. For smaller hoses like 1/2 and 3/8 inch
(more likely at the 5 kW and under level) lenght
is shorter. Just treat the hose full of water as
a big resistor in your ohms law analysis.
For occasional use, be sure that the water
quality is still good. There must be test kits
available? If you open the system to air,
dissolved oxygen is a bad thing. We use
deoxigenator bottles as well as RO bottles. We
keep it below 5 ppb as recommended by CPI/Eimac.
Thales tube company sells expendable electrolyic
anodes which are placed inside the water fittings
at the connections to their tubes, so that you
sacrifice them, and run higher conductivity
water. It can be as low as 100 kohm-cm using
these devices. But they need to be checked
annually in 24/7 operation, as the tips will
erode away to below the edge of the brass
fitting, then you expose the fitting to
erosion/corrosion.
One more point, do not use regular steel in the
plumbing for a DI cooled loop. It must be copper,
brass, or stainless steel.
I agree that water cooling is a proper subject
for some QRO systems. Probably has been beat to
death here this past two weeks though! Try it,
you'll like how quiet it is. BUT, as you all
know, HV and water don't like to mix.... However,
for solid state, its relatively painless:
I helped design and install two 2.8 kW CW water
cooled amplifiers at 805 MHz, at work here in
1994-97. They replaced a room full of RCA
Cermelox Tetrodes in cavities, which had been
made obsolete when Burle Industries quit making
the tubes. Our complete 40 dB amplifier with
power supply fitted in one tall 19 inch rack. We
used a slug of MRF899 bipolar transisitors, as
LDMOS wasn't the rage then. You can read about
the amplifier and see photos in the 1998 RF Expo
Proceedings from San Jose, or send me a note and
I can forward a copy.
73
John
K5PRO
>Will writes:
>>
>> Personally, I dont see anything wrong with the posts as they
>> pertain directly to water cooled tubes. If some addative can
>> be used to cool a tube better, this is an amp forum, and it
>> should be discussed. This especially if the addative can
>> prolong the life of a very expensive tube.
>
>Neither do I see a problem. Fact is, by this time next year
>I expect to see a water cooled solid state amplifier available
>at Dayton. There should be some 120 - 200 volt transistors
>available at a reasonable price per watt by then the problem
>will be keeping them cool with a typical heatsink/fan. A
>water cooled substrate (copper block) with a small closed loop
>system would make for a very nice package.?
>
>I hope we see some 1500 Watt (CW) output 100% duty cycle solid
>state amps (4 transistors) at reasonable prices (competitive
>with the Ameritron, TenTec, Commander, etc.) within the next
>two or three years.
>
>73,
>
> ... Joe, K4IK
>
>
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