Re: freon alternative

[Mark Denovich <mark@domain.elided>]

Ralph Fetsch wrote:
> The reason this mixture was outlawed is because if you have a leak you have
> a very big bomb under the hood of a hot engine.
I don't want to be disagreeable or start a debate, but this is bunk. 
It sounds sensible... propane is a flammable gas, the Hindenburg* was 
filled with flammable gas, therefore...

However this conventional wisdom does not stand up to scientific 
evaluation, nor is it supported by a vast amount of empirical data on 
the use of HC refrigerants in automotive air-conditioning.

References:
http://ctan.unsw.edu.au/pub/archive/HC/papers/HCpapers.html
specifically: http://ctan.unsw.edu.au/pub/archive/HC/papers/alpga95.pdf
http://yarchive.net/ac/hydrocarbon_danger.html

If you consider other references, please consider the motives of the 
source.  I tried to find studies from reasonably neutral parties.

If you don't want to bother with the math, which is more worrisome:

~20 gal of gasoline with lines running through the passenger compartment 
and over the top of a hot engine.  Brake fluid, motor oil, air 
compressor oil, and power steering fluid are all flammable, and much 
more likely to stay 'lit' and are in the close proximity of very hot 
exhaust components.

Less than 2lbs of HC refrigerant, which is easily disappated, has a very 
narrow fuel/air ratio range where it is explosive, does not easily stay 
'lit' (and thus would be unlikely to catch other things on fire) and 
even in the worst case senario simply does not have the energy to be a 
likely cause of significant bodily harm.

I'll risk Mr. Ashcroft et al. knocking on my door, to mention that I 
have a lot of experience in the past working with explosive gas 
mixtures.   Their bark is much worse than their bite.

	--Mark

*in the case of the Hindenburg the skin of the blimp was doped with a 
varnish containing powdered aluminum and iron oxide.   If you've ever 
made your own fireworks you'd know just how interesting powdered 
aluminum can be.   The hydrogen burned off almost instantly, the part 
the made it so memorable was the burning skin.

see more at http://engineer.ea.ucla.edu/releases/blimp.htm
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