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Re: [TowerTalk] Oil For Dummy Load

To: towertalk@contesting.com
Subject: Re: [TowerTalk] Oil For Dummy Load
From: Howard Hoyt <hhoyt@mebtel.net>
Date: Fri, 4 Dec 2015 15:02:57 -0500
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
>>"even distilled water is conductive if even so little. Once it get in contact with any metal >>it will start to dissolve the metal and become ionized = conducting. Other than that, water >> would be very good for a dummy load with its high heat capacity. hans - N2JFS"

I second that and would emphasize ESPECIALLY distilled water is chemically active. After 30 years running an ultra high purity water system I can tell you about dissolved stainless steel fittings, eaten from the inside until they fell apart.

Water is basically H_2 O but: a certain percentage of the H_2 O will disassociate into free H2 and O ions which are fantastically corrosive. In the pure water industry waters purity is rated by it's conductivity due to free ions, and theoretically pure water is measured at ~18Mohms per cc. In order to keep it this pure it must exist in a loop system, continually being polished using cation and anion resin beds to remove free ions. Even then the few ions which manage to remain for any length of time corrode just about anything other than certain grades of Teflon or other special polymers.

This characteristic of water is unfortunate, because it is a superb cooling fluid, with high heat capacity, thermal conductivity and low viscosity with a thin laminar flow layer. In our chiller systems we had to add large amounts of anti-corrosive and highly toxic anti-biological agents to de-ionized water to stabilize the thermal transfer and preserve fittings.

A reasonable replacement for water is pure inhibited ethylene glycol, we used to use Dynalene brand which is probably too expensive for ham use. Do not use automotive coolant, it contains metallic and silicate based anti-corrosive agents which are meant to operate in an air-free environment. They can foster growth of gels which can coat the surfaces, inhibiting heat transfer.

All in all, cheap mineral oil looks to be a good fluid to use!

Howie - WA4PSC
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