[TowerTalk] Oil For Dummy Load

[Roger (K8RI) on TT]

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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