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Re: [Amps] Advice needed for SS amp

To: Manfred Mornhinweg <>, "" <>
Subject: Re: [Amps] Advice needed for SS amp
From: "Fuqua, Bill L" <>
Date: Fri, 7 Jun 2013 03:46:20 +0000
List-post: <">>
We had a professor with a large water cooled 3cv10,000 tube in a DC electron 
metal evaporator power supply.
Guy working on a shoe string budget. It was donated. He could not run tap water 
thru it so I had him get a 55 gallon
drum and fill it with distilled water. Pump and a deionization filter was 
attached. He did ultimately cool with tap water
by running the tap water thru 1/2 inch cooper tubing in a coil placed in the 
drum.  Worked great!
  He did not need all the full capacity of the power supply and he was able to 
cool it and his e-gun evaporation system
at the same time. 
  As I said, he was on a shoe string budget. This power supply put out over 5kV 
at few amps. 
Bill wa4lav

From: Amps [] on behalf of Manfred Mornhinweg 
Sent: Thursday, June 06, 2013 10:08 PM
Subject: Re: [Amps] Advice needed for SS amp

Larry, Jim,

> Any one want to check my math?

I checked it, and Larry is right.

A half gallon of water (1893 milliliters), which has a specific heat of
roughly 4.19 joule per milliliter per kelvin (the actual value varies
slightly with temperature), heated for 5 minutes (300 seconds) with 1500
watts, would warm up by

1500 * 300 / 1893 / 4.19 = 56.7 kelvin,

which is the same as 56.7 degrees Celsius. Hardly enough to make it
boil, unless it was pretty warm to begin with!

Starting from typical tap temperature, and considering some loss that
ends up heating the kettle and producing some steam, the actual time
required for boiling would be somewhat between 7 and 8 minutes, assuming
the power is actually 1500 W and the water volume is actually half a
gallon - and that the water is pure, not mixed with some liquid that has
a lower specific heat! Now I don't think that anyone will boil a
water/glycol mix to make coffee, but it's very possible that the heater
actually is consuming more than 1500 W, or that the amount of water is
somewhat less than half a gallon.

This illustrates that cooling a legal limit amp with a bucket of water
under the operating desk is a satisfactory method for casual operation
in SSB, but won't cut it for a full weekend of RTTY contesting!


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