Reverse Cooling patents

[Greg Hermann]

>I lloked thru my Evans file and found some info on the Evans patents for
>aqueous and non-aqueous ( propylene glycol) cooling systems. The patents
>for PG systems are: 4,550,694  , 4,630,572   and 5,031,579.
>
>There is alot more to the patent for reverse flow cooling aqueous
>cooling systems than just reversing the flow. I have not read the
>patent but according to some literature, it is the understanding of the
>important role of vapor formation and recondensation which allowed Evans
>to solve problems not understood or solved by others. This, I believe,
>is why the patent was granted. The NUMBER is 5,255,636. It applies in
>the USA.
>
>That is why PG works so well if one does the whole system- ie : better,
>pump, radiator, etc etc. MUST get rid of all the water since any left
>will give the trouble causing vapor which allows high metal temps and
>detonation or esc retard etc etc
>
>regards,
>
>frank parker

Well--the trouble is that the vapor over a glycol (either one) water
solution condenses at a significantly lower temp than the temp of the
liquid--basically because the vapor has a higher percentage of water (the
lower boiling component of the solution) in it than the solution does. Same
principal as what goes on in a fractional distillation tower to make it
work. The difference between the boiling temp and the condensing temp is
greatest for glycol/water solutions at about a 50/50 mixture.

What that means is--that the little nucleate boiling bubbles have to travel
further out into the liquid stream in the water jacket before they
condense. This is hardly new science or technology--it is at least as old
as absorbtion refrigeration cycles and fractionating towers.

I am still kind of astounded that Evans was able to get a patent on it!

And the liquid pumping horsepower to get the same cooling effect with 100%
Glycol is pretty astoundingly higher than what is required with water.

Regards, Greg