[TowerTalk] Oil For Dummy Load
Roger (K8RI) on TT
K8RI-on-TowerTalk at tm.net
Sat Dec 5 01:00:36 EST 2015
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.
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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