one point:
Water does not have high heat capacity, but it's great for transferring
heat. 1 calorie will heat 1 cc of water 1 deg.
Heat capacity and the ability are quite different.
73
Roger (K8RI)
On 12/4/2015 3:02 PM, Howard Hoyt wrote:
>>"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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