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Bill
The reason that PG is use in automotive cooling system is to reduce "film" boiling.
Georges B.
-------Original Message-------
Date: 06/28/05 08:39:14
Subject: [FlyRotary] Re: NPG + use in aircraft??
At 11:58 PM 6/27/2005, you wrote:
> Al
>What I meant was due to the high boiling point of PG it would protect
>against"film" boiling which causes pre-ignition.
I don't think so.
The higher boiling point would raise the temperature of the hot
spot. This is not likely to impede film boiling. It takes a fairly stout
heat source (and a big temperature difference) to get film boiling in plain
water. Raising the boiling point would only make a difference if you were
very close to the transition and everything else stayed the same.
The higher viscosity of NPG would tend to impede convective
cooling (as well as forced convection) which would promote localized film
boiling. The lower specific heat and heat of vaporization for NPG would
make it much more prone to film boiling as well.
Looking at the numbers, it seems to me that if you have film
boiling problem using water, you are going to be much worse off using NPG.
Bill Dube'
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