Deionized water works fine for cooling big tubes so it shouldnt affect metal
for a long time before needing replacement.
Carl
KM1H
----- Original Message -----
From: "Roger" <sub1@rogerhalstead.com>
To: <amps@contesting.com>
Sent: Tuesday, November 29, 2011 7:10 PM
Subject: Re: [Amps] Can distilled water be used for a dummy load ??
> On 11/29/2011 9:05 AM, Jim Thomson wrote:
>> My hb 50 ohm dummy load consists of 4 x 200 ohm globars in parallel
>> [type SP, glass bodied
>> and suitable for oil immersion]. Each resistor is 1" diam x 12" long.
>> [275 W CCS in air]
>> Each resistor resides inside it's own 2.875" OD x sched 40 Aluminum
>> tube.
>> All 4 x thick walled AL tubes are heliarc welded.
>
> I'd try it and see. As long as it's either distilled or Deionized it
> should work. As this is a new system you have not used with oil, you
> don't have to worry about cleaning it. I'd check it with and analyzer
> and with no fluid, then add water and check again to see how it
> changed. If it changes for the worse then I'd try the mineral oil.
>
> Yes, water is about the best thing going for heat transfer (calories per
> unit weight) at atmospheric pressure. Oil, although not as good is
> probably good enough.
>
> Water may need to be changed maybe once a year. DI is ion hungry so I
> don't know how it'd work with the solder joints or metal in the circuit.
> Tap water? It definitely will lower the resistance of the dummy load.
> Whether it will adversely affect the SWR, only a test will show.
>
> 73
>
> Roger (K8RI)
>
>>
>> I heard some place that instead of xfmr oil, that distilled water can be
>> used instead?
>> The same glass bodied type SP resistors, [50 ohm, high wattage] are
>> used in water cooled loads,
>> the type that has the garden hose on one end, etc.
>>
>> Seems to me that distilled water will conduct heat a lot better than xfmr
>> oil. The question is,
>> will the use of distilled water in a 7 gallon metal container, with
>> resistors immersed present any
>> swr problems ? If I remember correctly, swr was high on heath cantenna
>> loads if no oil used at all,
>> and dropped to dead flat once the oil was poured in. There was also a
>> similar 50 ohm load in the
>> old arrl books, same resistor as I'm using but it was a single 50 ohm
>> unit, and not 4 x 200 ohms in parallel.
>>
>> I would prefer not to use xfmr oil if at all possible. It's a little
>> tougher to get a hold of these days..and not cheap.
>> My main concern however is something leaks. Water on the concrete floor
>> in the shop is one thing, but 7 x
>> gals of xfmr oil is a disaster. Can you add rust inhibitor's or
>> glycol to the distilled water ??
>> Do I even have to use distilled water, or will clean tap water work ?
>>
>> A 50/50 mix of water/glycol will result in a 265 deg F boiling
>> point..BUT the heat transfer is no
>> where as good. I'm using a new 7 x gal paint can for this project, the
>> 4 x resistors and the welded AL
>> tube assy, hang from the top lid.
>>
>> Thanks... Jim VE7RF
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>
>
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