[Amps] PowerGenius XL - Others

[Roger (K8RI)]

Years past, I worked on many water cooled tube type 
amplifiers/oscillators.  Compared to those, water cooling a SS amp is 
outlandishly simple.  Route the Cu water tube through a milled slot in 
the heat spreader.  The most complicated part is how well you want to 
monitor the water flow and temp. Typically a restrictor is placed in the 
input line and the pressure is measured on both sides of the restrictor. 
Due to the heat spreader being at chassis ground, heat sensord can be 
directly attached to the spreader plate.

This has the advantage that a finned cooler can be added, so if the 
water flow stops, the amp can still be fan cooled

73, Roger (K8RI)

On 2/14/2017 2:07 AM, John Lyles wrote:
> I've been using water cooled pulsed RF amplifiers since 1995 at work. 
> The first uses were DMOS MRF151G variants running @28 VDC. In the last 
> 3 years we have moved those out and gone to 48 volt LDMOS, far less 
> devices to get 5500 watts peak at 200 MHz.
>
>> I know water-cooling has been discussed here before, but I agree that a
>> well designed water-cooled SSPA has the potential to gain some 
>> traction in
>> the amateur market if the $ make sense. That said, I think it is
>> unrealistic to expect one of our ham radio manufacturers to offer an
>> "inexpensive" water-cooled SSPA for amateur use. The added complexity 
>> and
>> potential maintenance might be enough to put the water-cooling 
>> concept on
>> "ice" from a ham radio manufacturing point of view.
> .....
>> So far, this is about the closest I have seen to getting to where the
>> water-cooling needs to go (at least from another ham). I suspect in the
>> ISM/radar/broadcast world, water-cooling SSPA's is fairly 
>> straightforward.
> .....
>
> In addition to solid state RF for driver stages, we use a number of 
> different tubes in plain water cooled and hypovaportron cooled.
> The difference is that we have already got a huge deionized water 
> plant, so air cooling is generally avoided for all stages. The 
> amplifiers are cleaner inside.
> John K5PRO
>>
>> A big difference between vapor-phase and liquid-water cooling is that 
>> vapor
>> cooling is much more efficient per volume unit of water passing 
>> through the
>> system.   From the Dick Ehrhorn's description on cooling efficiency:
>>
>> "In typical closed-loop liquid-water-cooled systems, the maximum outlet
>> (hot) water temp must be held well below 100 deg C to avoid hot-spot 
>> boiling
>>
>> on the anode surface, which can and does create steam bubbles, which in
>> turn "insulate" the hot spot from the water so the hot spot gets even
>> hotter. This typically creates a temperature runaway and may lead to
>> destruction of tube and/or cooling components. Typical inlet (cool) 
>> water
>> from the chiller may be specified as </= say, 45 deg C, and maximum 
>> outlet
>> water temp as 80 deg C to avoid spot boiling.
>>
>> Anyway, in this example each gram of cooling water passing through the
>> tube's water jacket can absorb not more than (80-45) = 35 calories of 
>> heat.
>> Conversely, each gram of 45 deg C water entering a vapor-cooled tube's
>> boiler absorbs approximately [540 + (100-45)] = 595 cal/gm while
>> vaporizing. So, vapor cooling requires passing only about 35/595 = 
>> 1/17 as
>> much water
>> volume through the system as does water cooling."
>>
>> Paul, W9AC
>
>
>
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