[TowerTalk] Oil For Dummy Load

[Howard Hoyt]

 >>"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